Tuesday, October 10, 2017

Minnie the 400 Monster gets 620 cams: One has one's arse handed to oneself yet again.

Some time ago I bought some 620 cams and sent them out to Ian Drysdale to have them modified to suit the earlier 3 bearing heads so I could try them in other things - namely my 400.  I've also made a rig to hold a spare 400 head I have that allows me to read cam lift as the cam is rotated.  It's all very analogue (ie, me sitting there looking at a degree wheel and dial gauges) and gives me valve lift every 4 degrees of crank rotation.  You'll see more of that in the future.  This way I could compare the 400/600/750 cam (labelled R) and the 620 cam (2S), as below.

Spec wise, the 2S is like the R, but with the inlet closing 15 or so degrees earlier and with more lift on both inlet and exhaust.  In profile, the exhaust is a bit bigger and has an earlier peak while the inlet is as expected.  The reason I wanted to try the 620 cam is that the 400 has a long flat power curve at the top end - it's pretty flat from 9 to 11.  As such, I was wondering if it was over cammed, and figured the 620 cam should be better and a good illustrator of why.  What I was hoping to see on the dyno with the 620 cam was peak power of the same or more, the peak moved down the rpm range and the power dropping away after the peak.

Spec comparison as below:

I fitted the 620 cams at the inlet centreline spec of 112 degrees, and with the drilled pullies I could advance them to 107 to see what happened.  I was also considering retarding them on the dyno as well, but didn't bother in the end.  As usual, the results sucked all the motivation right out of me.

Red is R cam at 108 degrees, blue is 2S cam at 112 degrees and green is 2S cam at 107 degrees.  The midrange improvement is between 5,700 and 7,100 rpm, and the top end loss starts at 8,500 rpm.  Given we're only dealing with 38 hp at the peak, we're not talking great differences here.

As an aside, the runs below are all done with an original 2-2 header and the Megacycle mufflers.  I pulled the 2-1 a few weeks ago and jammed the original horizontal header onto the modified vertical header.  A dyno run showed the same power as where we started all that time ago, and with much the same richness as all the std airbox lid (both snorkels fitted) runs for the 2-1.

Mixture wise, it didn't do much at all.  Still too rich (std 2001 my M400 carbs and jetting).  Top graph is horizontal, second vertical from memory.

To lean it out a bit I thought I'd try to usual trick of pulling a snorkle, which had the usual effect, as below.

Still generally too rich, but better.

As the graphs show, what I wanted to see and what I did see were two different things.  I have become accustomed to dyno disappointment with this bike.

But my mechanical sympathy has me cringing as I rev it over 9,000 rpm looking to use the last of those 38 hp, it's not something I like doing when there's no performance gain to be had.  When I first made the 2-1 and fitted the Acewell dash I was running it up to 8,000 rpm or so and it felt great.  Dyno shows that the 2-1 with Danmoto muffler turns to crap around 7,000 rpm, but under that, and especially through the midrange, it's as good or better than the 2-2.  With the Megacycle muffler it holds the power a bit longer, and definitely felt better on the road between 8 and 9,000 rpm when I held it open just to see how it felt.  But I wouldn't normally go that high riding it around, so I'm a bit caught in the dyno number loop here as it would be.  Or, more to the point (let's be honest here), I didn't expect the things I did to work so badly nor require so many excuses.

Now with the 620 cams it's better again in the midrange, and I think I'll go back to the 2-1 and one snorkel and either tolerate the Danmoto noise or get another muffler made.  I have a design in mind, whether it comes to fruition or not is another matter.

As a comparison to where it was all std, it's not too bad.  Mufflers, cams and one snorkel out of the airbox lid in red, all std in blue.  As a graph, it looks great until you read the numbers on the LH side and think "oh".  Its got another 4 - 5 hp for most of the rev range, which, when you've only got 37 all up, is at least 10%, and more as you go down in rpm.  Woohoo!  Doesn't make it much faster though.  It's slow.  Kinda fun, but still way slow.

Wednesday, September 20, 2017

Minnie the 400 Monster: Not getting anywhere

Man, this thing is just kicking my arse.

What often happens with a project bike of mine is that at some point I go off on a pointless tangent and just dig myself a great big hole.  No point breaking tradition here.

My custom job introduced an obvious issue with the 2 - 1 exhaust, and it has occurred to me that adding the fairing may have played with the fuelling as well.  I've certainly been caught out on that before.

I'd be thinking about what to do about it, and had been getting close to buying another std horizontal header to modify to work with the ceramic coated vertical header and then get a couple of mufflers made to suit.

Thinking about what I had seen with the dyno runs so far, and Dave's comments that i should rejet it to fix the top end richness, I had a look back at some of the runs to see if there was anything to give me hope.  I know from lots of previous experience that top end richness on the Dynojet really kills the power.  Maybe it's richness past the torque peak, as it doesn't seem to affect the power as much through the middle.  A couple of runs caught my attention.

Red is the 2-1 header with the Danmoto muffler and no baffle, blue is the same with one of the snorkels removed to lean it out.  The improvement in top end power with mixture a bit over 13:1 (good for dyno power, but a bit lean on the road imo) was about 4hp.

4hp is about what I'm down from the original headers.  Red is std headers and two Megacycle mufflers, blue is 2-1 and one Megacycle muffler.  An extra 4hp through the top end would be just great, especially with the midrange improvement.

So the obvious was to lean it out.  When I fitted this 400 engine I set these carbs up with the 2001 M400 jetting, which is the same as the M600.  From my video of the slides lifting through the air filter lid, I figured the rich dip was main jet related.  Std is 132.5, and I had 122.5 and 127.5 on hand to choose from.  I was concerned 127.5 wouldn't be enough of a change, so went 122.5.

Easier said than done.  The fairing mounting brackets I made bolt off the bottom of the ignition switch, and all the wiring for the dash, including the original loom sections I needed to hide, are jammed on top of the airbox under the ignition switch.  All of which had to be removed to get the airbox out to access the float bowls.  I'd forgotten about all that guff when I allocated a couple of weekend hours to a main jet change, so it was straight into tanty time from the get go.  Only got myself to blame, on so many fronts.

It's fitted with a heater kit too, so the float bowls are hard to far enough out of the way to get into the mains.

After I had it back together I went for a ride.  Well, first I had to make the dash work again, as disconnecting it made it lose the wheel diameter and the tacho seemed a bit screwy, reading a bit too high.

On the road it felt great, revving out nicely compared to how it had felt before.   Brimming with (over) confidence, I took the chance for an early morning trip to the dyno and typically it went tits up.  On the way there I tried some WOT and it felt pretty crap - flat and surgy - through the midrange.  Turns out it dynod just like it felt.  Crap.

Compared to some previous runs, it gets a bit murky.  The dyno has just had the air/fuel cell replaced, so I don't know if that has influenced anything.  Doesn't explain the difference in how the bike felt though.  Anyway, red is with the leaner 122.5 main jets and one snorkel removed.  Blue is 132.5 main jets and about 5 degrees more ignition advance over std.  Green is the same, but with std ignition advance.  So I really don't know what is going on with it.

The problem is where to go next.  I want to fit some 620 cams to see what happens to the power curve.  I'm hoping that with the early inlet closing, they'll peak the power lower and reduce the need for so many revs.  But, the fact the factory used the 800 cam in the M400ie instead of the 620 cams makes me wonder if that too is just folly.

Before I do that, I want to make sure the result is not tainted by an idiotic exhaust or a wacky fairing.  Plus I have no idea what the original jetting was like with the original headers, which may itself have not been good.  You know where that's going.

Either way, the airbox needs to come out and the 132.5 main jets go back in again which means fighting with the airbox and wiring and other crap and really, I'd have been far better off just leaving the jetting the way it was and fitting the original headers I have.  Joy.

I can always refit the other exhaust when it needs to look good I guess.  I'm even going off that look too.

Friday, August 25, 2017

Minnie the 400 Monster: Muffler comparison test with the 2 -1 header (ie, why is it so bad)

I had the feeling that the Danmoto muffler I had modified for Minnie to go with my 2 -1 header set was the cause of the poor top end.  Getting back to the dyno with a Megacycle muffler fitted proved to be a bit of an organisational nightmare, but I finally got there.

Red is the original headers and two of the Megacycle mufflers.  Blue the 2-1 header with the Danmoto muffler from the previous.  Green is the same as that run, but with one of the Megacycle mufflers instead of the Danmoto.  Bit richer, more power - possibly different wideband sensor to the last runs (wacky?).  Yellow is with Megacycle muffler and one of the airbox lid snorkels removed.  Nowhere near as lean as the runs from last time with a snorkel out, not sure why.  Maybe that was no air filter as well.

All of which means it dyno'd like it felt with the Megacycle muffler - better, and pulled through the top end nicer.  Still down on power though.

An aside here is that when the bike was running the std 2 - 2 header set I didn't have a tacho fitted, and I'm sure I never went over 7,000 rpm.  So that big jump in the std header curve, which happens at around 7,200 rpm, I may never have felt.

I took a std muffler with me for these dyno runs, and some Kokusan ignition units to replace the Ignitech.  I have had intermittant cylinder dropping at idle when hot with this bike for years, across 2 engines now so I know it's not engine related.  I thought I had swapped the Ignitech out without success in the past, but I must say that the issue has not reappeared with these Kokusan units fitted in the couple of times I have ridden Minnie since.  To be fair to the Ignitech, it is the unit I originally bought back in 2006 or so.  It's had a good run, and the new version has a dedicated MAP sensor input which works much better than trying to mimic a TPS with a map sensor.  Maybe I just needed a reason to not feel bad about updating it.

Std muffler in blue, Danmoto in red and Megacycle in yellow.  The air/fuel is a bit unexpected in as much as the red line seems a bit lean, but it may be a physically different sensor (I had two to choose from).  Also you can see that an open muffler leans it out.  I had thought that maybe these carbs would richen up with an open muffler due to the way CV carbs work, but I'm still not convinced this was a good test.  Danmoto is still better than std!  For an illustration of the hollowness of that victory, see the following graph.

As from the previous graph, blue is 2 - 1 header with std muffler, red is 2-1 header with Danmoto muffler and green is way back when with std 2 - 2 headers and std mufflers (all with 108 cam timing).  Yay!  The line for a shot to the pills starts behind me.

Anyway, onward into the slurry.  Red is std muffler as before, blue is Megacycle muffler with Ignitech ignition, green is Megacycle muffler with Kokusan ignition and yellow is Megacycle muffler with Kokusan ignition and one snorkel pulled from the airbox lid.  Helps with the richness.

Comparing headers only (std versus my 2 - 1), first up std mufflers.  

And the Megacycle mufflers.  The point where the two curves cross is bang on 7,000 rpm.

So, some conclusions of sorts.

1/  The Danmoto muffler I really like doesn't work.

2/  The 2-1 header I made doesn't work.

3/  It's too rich at the top end.  From my test of watching the slides lift through the airbox lid I think i'll call it a main jet issue.  If pulling the other snorkel fixed that without hurting the midrange I'd be all over it, but as that wishful plan didn't pan out I'll ignore it for as long as I can't be arsed pulling the airbox out.

4/  Original headers don't work anymore due to the lack of muffler mounts due to the Ducabike rearsets. And the vertical header has been shortened, so any main header will need to be cut, bent and welded as this 2 - 1 header was for them to join.  I did find another original vertical header at work, so I could fit that.

5/  One has dug oneself a hole.

I think I'll need to refit some 2 - 2 headers, as the next step is some 620 cams modified to fit the old 3 bearings heads.

Sunday, June 4, 2017

Magni Sfida / Guzzi PHM40 dyno graph

As alluded to in the Sport 1100 post, a graph from a Magni Sfida running an over 1000cc LM4/5 motor of some tune spec (no idea specifically) fitted with PHM40 carbs.  Which model of PHM40 I don't recall, it was 2008.  

With the 175 mains it came in with it would kill the engine if you held it open from 4,000 rpm - at 6,500 to 7,000 it would shut down, then come back.  As the plugs were very black I figured it might be momentarily fouling the plugs.  The dyno showed OMG rich - off the scale (under 10:1) by 3,500 rpm.  148 mains fixed it, but the mixture tapered in a straight line from 14:1 around 3,500 rpm to 12:1 by 7,500 rpm.

My suspicion now that I look at it is air bleed sizing, which is not adjustable in Dellortos.  So I was worried that I might see a similar thing with the Sport 1100, but also curious that the fact these carbs were made to suit this engine size and rpm range may mean they were different internally to whatever variant of PHM40 was on the Magni.  The problem of "the things you don't know you don't know" means sometimes you have no answers.  I don't know who you'd ask either.

Red is 175 main, blue 165, green 152, dark blue and yellow 148 (LH and RH samples).  A compromise is all that was available here.

Dellorto carb tuning on a Moto Guzzi Sport 1100, with some gearing and ignition rambling

Something I haven't done for 22 years - played with carb tuning on a Sport 1100.

We were dealers at Moto Italiano in 1995 when the Sport 1100 were released.  They ran poorly at low speed, and we tried a few things to fix them that didn't really work.  Looking back now I don't recall what we did, but I don't think we ever changed needles or needle jets.  Probably because it went into the "too hard" basket that you often get at a dealership when you're chasing warranty issues with no support or denial from the importer/warranty issuer.  It can be a very frustrating situation.  Plus I didn't really have much specific Dellorto tuning experience back then, nor the info required in the form that I'm going to use here.

So when I had someone ring and ask me to tune one I was a bit reluctant.  The story was that it used to run very nicely.  Then someone else had played with it, and now it didn't go so well.  The airbox had been removed and small pods filters fitted, and the jetting changed.  It was all a bit vague and I had the feeling I should have done what I knew at least one other person had done and found an excuse not to work on it.  Or just outright refused.  But I have this often trouble making sense of obligation to help people, and agreed.

The original airbox got a lot of blame for the poor low speed running back in the day, but one thing it did have was the somewhat unglamorous plastic ram tubes on the back of the carbs.  I don't recall how long they were, but looking at the available space and remembering what they looked like in my 1100i, I'd think they were around 150mm long.  When you start looking at inlet lengths and theory and how long stuff needs to be, it generally turns out that, on motorcycle applications, you just don't have the room.  The distance from the valve seat to the air entry is the length you're looking at, and for this engine running to 8,000 rpm maximum ideally it'd be in the 450mm range.  More than the available.  

I recalled Barry Jones of Italian Motorcycle Engineering playing with one back in the day, so I gave Baz a call to ask what he had done.  He'd been involved in one fitted with FCR carbs and on that they'd moved the carbs back an extra 50mm or so to give it some more length.  I thought it'd be easier to fit a ram tube of some sort, and went looking for something with a 52mm mounting ID.

I found these - Ram tubes - and figured they'd be as good a place to start as any.  Not too expensive being part of the consideration when you're trying ideas that might turn out to be crap.  I also needed filters, so got some of the Uni filter socks to go over them.

I had also asked Baz for any jetting recommendations.  His reply of K5 and 265 made me think about how you can often overlook a simple basis.  Lots of Ducati 900 bevels with PHM40 run the K4 needle and 265AB needle jet, and for Guzzi it seems to be the K5 needle and 265AB needle jet.  The original setup for the Sport 1100 is K18 and 266AB.  This one had K20 and 268AB.  I have a spreadsheet of Dellorto needles that makes it easy to compare them in an almost visual sense, and that's where I headed before I started changing things.

Well, the first thing I changed was the float height.  Set to 21mm when I started, I lifted the float level to 18mm.  This is done with the carb sitting on the air filter flange and the float pivoting about and above the spindle.  18mm is pretty close to as high as they would go and still give a readable setting, whereas the older PHM were more obvious at 18mm I recall.  Anyway, they were set and I moved on.  I don't use float level as a tuning variable.  I figure offering myself less possibilities for confusion is beneficial.

As was, the carb set up was 60/3 slide, K20 needle on the 3rd notch, 268AB needle jet, 162 main and 65 pilot.  Std spec on the Sport 1100 (Euro that we got anyway) was 60/5, K18@3, 266AB, 152 and 57.  The difference in the slides is the pump ramp - see my  Dellorto phf / phm pump ramp profiles piece for more info there.

Comparing the needles and needle jets can be confusing, but some years ago I made a spreadsheet for just this purpose.  The needle jets, like the Dellorto mains and pilots, are self explanatory - divide the number by 100 and you have the dimension in mm.  A 268 needle jet is 2.68mm, a 152 main is 1.52mm and a 57 pilot is 0.57mm.  On the needle jet AB denotes the physical design of the jet and what carb models it fits into.  Interestingly, the Keihin FCR carbs have only one needle jet size. They offer a vast array of needles varying in root diameter (steps of 0.01mm), taper and overall length to hit the required targets.

The Dellorto needles are numbered without reason as such.  All (afaik) K needles for the PHF/PHM carbs are the same overall length, being 73.5mm as I measured it.  Variables are the root diameter, tip diameter, taper length and number of clip grooves.  This chart shows the options.  It's a bit hard to read, due to the amount of info on it.  I didn't realise there were over 90 K needles - I have up to K30 on my spreadsheet.

Using the numbers I had found, I made a spreadsheet which gives needle diameter at distances from the tip in 2mm steps.  It seemed about the most logical way to do it, although now that I have done some more measuring on them and found the clip grooves are 1.25mm apart using 1.25mm may have made more sense.  The K5, which has 3 grooves, has the top of the clip grooves 2.75, 4.0 and 5.25mm from the top of the needle.  The K20, which has 4 grooves, has the tops of the grooves 1.75, 3.0, 4.25 and 5.50mm from the top of the needle.  Probably more accurate to measure from the bottom of the needle given that's how the taper is specified, but that's not important now.

The spreadsheet looks like this.  This is the "sorted by #" page, and gives you the sizing info in # order.

To begin with, the important piece of info is A, the root diameter.  This is the constant diameter section at the top of the needle, which controls the mixture (in conjunction with the pilot jet, mixture screw setting, slide cutaway and needle root diameter) in the first 1/4 to 1/3 of slide movement (depending on carb throat diameter, maybe even up to 1/2).  Consider, realistically, how often you use more than 1/3 throttle.  Unless you're getting up it for the rent, it's not as often as you might think (hope).

You can see that the K5 is 2.45mm root diameter, whereas the K18 and K20 are 2.50mm.  Meaning the result of running any of these needles will depend also on the chosen needle jet, which is why you might need a 268 with the K18/20 and a 265 with the K5 sort of thing.

And so the confusion sets in.

Comparing the combinations was the next part of the spreadsheet, with a page I called "flow area".  Now, the important part to remember here is that this "flow area" is a calculated number with a somewhat limited grip on reality.  Reality means that there is a Boundary Layer, which refers to the fluid (be it liquid or gas) that is immediately next to a surface over which said fluid is passing.  At the surface, the fluid is actually not moving, and from there the speed of the fluid increases as you move away from the surface.

In this instance of a needle in a needle jet, there are two surfaces and the important dimension that will come up later (maybe I should do it now) is the circumference of the boundary.  A needle with 2.50mm diameter has a circumference of 7.85mm, and the needle jet with 2.68mm hole has a circumference of 8.42mm, giving us a total boundary layer surface width of 16.27mm which the fuel is flowing over.

Compare this to the 152 main jet, who's circumference is 4.77mm and you can see that the needle/needle jet combo has 3.4 times the surface width of the main jet.  Why is this important?  Well, in the comparison and calculations to come, you can calculate the flow area of the main jet and from that deduce when the main metering device (ie, biggest restriction) moves from needle in needle jet to main jet.  Except that the boundary layer will impact here to some extent, and comparing the two jet systems has to allow for the impact of the boundary layer of the needle/needle jet system causing a greater restriction and thereby, in reality, giving a smaller comparative calculated flow area as compared to the main jet.  ie, the needle in needle jet will remain the main metering device to a higher throttle opening (slide lift) than the numbers suggest.

So, to be clear, this is a number of some use, to be used with some notion of the fact that it's not totally realistic, in the quest for some ability to compare needle and needle jet combinations.  

Compounding this is the fact that the K5 has 3 clip grooves and the K18 and K20 4 means the grooves are in different positions and therefore the relative position of the needles can vary there also.  With the K5 needle and clip fitted to the second groove, there was 56.5mm of needle protruding below the slide, and 50mm of needle inside the needle jet.  With a 40mm carb, and realistically 39mm or a bit more of travel from idle to WOT, this meant that the needle taper would become active around 1/3 throttle opening, and anything under that throttle opening would be controlled by (in order from closed throttle) mixture screw, pilot jet, slide cutaway and needle root diameter/needle jet diameter.  Next time you're out on your Sport 1100 carby mark the throttle and take a glance to see how much you're using.  1/3 throttle is fair acceleration at any speed under quite a bit too fast for licence.

The following piece of the spreadsheet shows the needle diameters, calculated flow area and % comparison between the jetting set up.  Original is the Moto Guzzi spec - K18 with 266 needle jet.  1 is the "as delivered to me": K20 and 268.  2 is my starting point: K5 and 265.  3 is my first revision: K5 and 266.  4 is my finishing point: K5 lowered 1 groove to the first and 266.

The highlighted areas are the approximate effective range of operation that will be used on the PHM40.  The green area is the "non main jet" section and the yellow the "main jet" section.  Apply the aforementioned disclaimers from above as required.  I'd say the needle/needle jet to main jet transition is around 2/3 throttle.

You can see how much richer than std the K20 and 268 is, and the spark plugs did reflect this.  The bottom line of the % comparison is the one of importance though, as that's where I ended up, and it shows how much richer then leaner my final setting of K5@1 and 266 was.

The spec for my first step was the previously fitted 60/3 slides, K5 needle with the clip in the second groove (K5@2), 265AB needle jet, 152 main jet and 60 pilot.  The airbox had previously been removed and replaced with these pod filters that I generally don't like.  There's no rounded transition internally into the inlet, and I don't think they flow that well either.

On the road for the first ride, it was quite flat at very low throttle and rpm - there was a real dead spot around 2,000 rpm.  It really came good around 2,800 rpm and up into 3 - 3,500 rpm.  On a moving with/through traffic roll on it felt a touch flat again, but rather nice anyway.  Based on those two feelings, and the fact that having marked the twist grip showed that nearly any riding within any confines of traffic had the throttle less than 1/4 open, I went for the needle jet as the first change.  This is the opposite of what I usually do to a 900 Ducati - SS, MHR - with PHM40, where going from a 265 to 264 needle jet cleans them up very nicely on cruise.  I was after a similar minor change here, just the other way.

Ride two with K5@2 and 266 was nice.  The roll on from 70 km/h (probably less than 1/8 throttle) with 1/4 - 1/3 throttle opening was lovely, and the very low speed pick up was better.  Still fairly awful to ride under 2,800 rpm though, compounded by the clunky box and gearing.  Then I went up from 60 to 62 on the pilot, which richened the bottom without making any real difference to how it ran under 2,800 rpm.  It's a very odd feeling - if you hold the throttle constant and let it accelerate in first gear from 2,000 rpm up, the change in drive around 2,800 makes me think there's a spark advance influence here also.  I don't believe it's just mixture.  Going back to 57 pilots confirmed this - there was a bit of flatness around 2,500 rpm when cold, but once warm was no better or worse that with 60 or 62.  ie, still crap.  Idle mixture screw settings for around 5.5% CO were 57: 3, 60: 2 7/8 and 62: 2 5/8 turns out.

With the 152 mains fitted, the jetting I was running, with open pipes and pod filters, was the same as it was when the bike left the factory with the exception of the K5 needle.

Next was the trip to the dyno, to get some hard numbers and try out some inlet ideas.  We ran it as it was, then removed the pods, tried some other little filters that I didn't think would be any different (they weren't), then fitted the ram tubes and Uni filters.  After the WOT tests were done, we ran 1/8, 1/4, 3/8, 1/2, 5/8 and 3/4 throttle runs to check the mixture.

First up, pod filters versus no filters.  Not sure what the dip around 7,500 is about.  I'm don't know how much raising the float levels from 21 to 18mm would have changed the mixture, but I had also already gone down 10 numbers on the main jets (162 to 152) before I went to the dyno, and it was still running 12:1 or fatter.  Getting rid of the filters certainly helped.  The leanness at the start of the run happened for all runs over 1/4 throttle pretty much, but you know and ignore that.

(digression) One thing that did come to mind here is the shape of the air/fuel curve.  Years ago I dynod a Magni, which had an over 1000cc LM4/5 engine (no idea specifically) fitted with PHM40 carbs and it had an air/fuel curve that tapered from lean to rich and made jetting a bit of a mess.  With the 175 mains it came in with it would kill the engine if you held it open from 4,000 rpm - at 6,500 to 7,000 it would shut down, then come back.  I figured it might be momentarily fouling the plugs.  Dyno showed OMG rich - off the scale (under 10:1) by 3,500 rpm.  148 mains fixed it, but the mixture tapered in a straight line from 14:1 around 3,500 rpm to 12:1 by 7,500 rpm.  My suspicion was air bleed sizing, which is not a variable in Dellortos.  So I was worried that we might see a similar thing here, but also curious that the fact these carbs were made to suit this engine size and rpm range may mean they were different internally to whatever variant of PHM40 was on the Magni.  Which is the inevitable incidence of "what you don't know you don't know" raising its oh so welcome head.

But the air/fuel curve is somewhat similar to what I see with the Ducati 900 motors and FCR41 carbs - a lean rise in the midrange and somewhat richer either side.  The FCR39 are better (flatter curve) in that application for a 900, but gave a similar shape curve on my 750.  Just another aside.

Anyway, back on track we go.  Pod filters in red, no filters in blue, 152 main jet on both.

Next the trumpets went on without filters.  My hope was that they would help, which they did.  The dip in the curve around 4,500 has moved down a couple of hundred rpm with the extra length, but it's still there.  My Sport 1100i had a similar dip, and the easiest common element to apportion blame to there is the camshaft.  Not that it's a bad cam.  I believe it actually came from Crane.

No filters or ram tubes in red, ram tubes without filters in blue.

The only decent air filter option I had found for the ram tubes as was were the Uni Filter socks.  I did think that you could weld a flat strip to the ram tubes on the leading edge of the bell for a large K&N or the like to clamp to, but in the interests of not spending any more money than needed on parts that may not be used we went this way.  Happily, they worked.  No filters red, filters blue.

This gave us a WOT before/after result as below.  Rather relieving and satisfying, as it turns out.  The mixture leaned off to around 13.5 at 6,000 rpm, so after I got back to the factory I went up from 152 to 155 on the main, which I think helped a little with the roll on at 3,000 rpm too.  Realistically, you don't ride these things by nailing it full open at 3,000 rpm, but it's nice to know it will do it and just pull.

The air/fuel traces from the part throttle runs mostly showed the same consistency in curve shape to the WOT runs, which again must be due to camshaft and maybe exhaust design.  We didn't record a run under 1/8 throttle, but with it bumbling along on the dyno at 2,500 or so rpm it was even richer, under 12:1.  This was with 62 pilots, and both Dave and I were sceptical of how much impact a one or two step leaner pilot would have.  But, as is the case with carbs, you only have so many ways to fix an issue, so later I went to 57 and, as it was no worse, left it there.  Low speed and throttle like this is controlled by pilot jet, mixture screw setting, slide cutaway and needle root diameter.  Fixing it can either be a lucky guess and succeed, or many hours of trial and error.

The richness of the over 1/4 throttle runs was the reason for dropping the needles from the second to the first groove.  I did that and the main and pilot jet changes after leaving the dyno (a dyno session without being covered in petrol, oh the joy), so don't have any confirmation on effects of the changes.  But it felt better on the road.

Red is 1/8, blue 1/4, green 3/8, orange 1/2, dark blue 5/8 and brown 3/4.  Olive is WOT as a comparison.  The fact that any more than 1/2 throttle below 4,500 rpm gets you no more power is something I didn't notice beforehand, and now I'm curious if there's anything more than a change in engine noise with more throttle in that rpm range.  Dyno says no, but then it is just a dyno.

The final ram tube and Uni Filter sock fitment came out as below.  I cut the LH filter and spring down by 30mm to allow for the cylinder offset and to have them both ending at about the same point over the frame cross tube.  I used 33-57mm clamps to hold the ram tubes to the carbs (I actually had to open the ram tubes up a little with a flap wheel to get them on the carbs, but you need to be sure they're not going to bail once out and about) and 52-76mm clamps on the socks.  Given the trumpets are tapered where those clamps fit, and clamping oiled foam is like catching an eel (as good a reason as any to quote the great Mojo Nixon: "I'm slicker than two eels f***ing in a bucket of snot"), so who knows how well that'll work out long term.  Undoubtedly I will be informed.

The filters come with a zip tie to hold them on, but it's a bit low rent for an external fitment.

The final result is nice above 2,800 rpm, but it's a fairly unpleasant bike to ride under that (which in second gear is 50km/h) and exaggerated by the clunky gearbox.  This was made very obvious when I road tested a 1000S after servicing at the same time.  The 1000S, which has similar PHM40 carbs and different, but similarly large camshaft, was a joy at low speed.  It'd pull away from almost idle happily, and from memory it was running mostly std jetting (K19@3 and 268AB) with not too loud mufflers and maybe similar little mesh pods.

This prompted me to look at a couple of things, namely ignition system and gearing.  

The 1000S had an original distributor and Dyna controller.  As a side note (another one), when I first saw this 1000S for a big service some years ago, I checked the ignition timing and it had 20 or so degrees advance across the range.  A locked distributor from a previously fitted electronic ignition (before this owner's tenure) like a Lucas Rita maybe, which didn't require the centrifugal like the Dyna does, as the Dyna simply replaces the points system to trigger to coils.  Parts for these distributors are so hard to find it was easiest to buy a complete s/h distributor.  A set of LM4 advance springs and away it went.  Wasn't as responsive down low as before due to the lack of advance under 2,000 rpm or so, but better above it.  I thought it was pretty funny, I guess someone figured 20 degrees was enough to make it work.

Anyway, it ran so much better at low speed than the Sport 1100, with more rpm at any road speed, that I thought I'd check the gearing.  Turns out everything is different - primary drive, gearbox and rear drive - as below.

So the Sport 1100 gear ratios are all higher and closer together, the final drive ratio is taller, but the primary drive ratio is shorter.  Overall ratios are still quite a bit taller though.  I know the gearing came from the Daytona, which was theoretically geared for 270 km/h at 9,000 rpm, and the racing bikes would have gone that fast.  But I still don't see the need for the road bike to have such a close ratio box.

The Daytona and Sport 1100 don't have a cush drive in the rear wheel either, so it can be quite abrupt on the on/off and the low speed baggyness only exaggerates that.

To get an idea of what can be done final drive wise, see below.  I rang Mario at Thunderbikes to see what diff ratios could be swapped in, and Mario mentioned an 8/35 gearset from a V7 Sport (I think).  From 8/33 to 8/35 is about 6% change, whereas 8/33 to 7/33 is 12.5%.  6% sounds pretty good.  I had also thought of swapping in a 17" rear wheel from the later bikes - Daytona RS, Sport 1100i, Centauro and the V11 series all use the same wheels, 3 spoke 17" with the same disc mountings and a cush drive in the rear.  Comparing the tyre sizes on a few manufacturers web sites didn't show a great deal of difference in the tyre diameters - 650mm for a 160/60ZR18 and 630mm for a 160/60ZR17 - about 3%.  As the Sport 1100 and Daytona wheels are a different spoke pattern (which looks better imo), you'd need front and rear wheels to keep it matched.

Looking back at my Sport 1100i, I don't recall the gearing being something that I really thought about.  But the low speed manners were much better.

The table below is calculated speeds at 8,000 rpm for each gear.  This bike has had the fairing removed, so as a naked I don't think 240 km/h will be required.  With the power peaking around 7,000 rpm, I don't know if it'd pull 8,000 rpm in top gear anyway.

Changing the final drive ratio, keeping in mind this is a 70,000 km old rear drive, will no doubt involve a rebuild, so as a job you'd be allowing $2,000.  Going to a set of 17" wheels, with a new rear tyre, would probably end up somewhere near that too.  Not a cheap gearing change.  And I'd probably want a wider spread gear set in the gearbox too, just to make it nice.

The next point of thought is the ignition system.  The Sport 1100 got the Marelli Digiplex system, which was also fitted to the late carb model California and Nevada as well as the Ducati 906 and 1990 900SS.  The Ducati workshop manuals give advance curves, but the Guzzi manuals don't.  To me, it feels like this system has a rapidly increasing advance curve coming up to 3,000 rpm, as the character of the engine just changes in a few hundred rpm.  I did put some marks on the ring gear teeth so I could give it a rough check, and it didn't seem too bad, but maybe it just wants more.

More advance can make a real difference, especially to low speed response and smoothness.  I tend to add quite a bit to lots of the spark advance maps when I'm playing with the fuel injected bikes just because.

It is possible to replace the Digiplex with an Ignitech to give control over the advance curve, but another concern, based on what we've seen with the Breva 1100 and 1200 models, is that more advance around 2,000 rpm or so can make them hold up on the return to idle.  So maybe they found that issue back in the day with the Sport 1100.  Fitting an Ignitech and setting it up, especially if you add a MAP sensor to allow extra part throttle advance via a 3D map, would run to at least $800 I'd think.  So more possible fixes, but none of them cheap or guaranteed.

Wednesday, May 17, 2017

Dellorto PHF PHM pump ramp profiles

I have a Guzzi Sport 1100 in to attempt to tune, and in going through what had been changed and what effects those changes may have had, I found some specs for the pump ramps on the PHF and PHM slides.  So, the obvious thing to do was make a graph comparing them all.  It makes much more sense in a visual form for me.

The starting point is nominally the idle setting, but that's not a fixed thing so the actual "when stuff happens" numbers are a bit ish.

The slides are numbered with an XX/Y system, where the XX is the cutaway (in tenths of mm) and the Y is the pump ramp ID (it's just a number).  The cutaways I've seen are 50, 60 or 70, and the slides are /1 to /5.

The cutaway affects low slide lift mixture.  The smaller number has less of a cutaway at the rear edge of the slide, which increases the manifold vacuum transferred to the top of the needle jet (atomiser) and enrichens the mixture due to the greater pressure differential between the top of the needle jet and the fuel in the float bowl.

The maximum pump lever deflection on an old slide I had measured at 5.6mm, so that's the maximum number I used.  The slide travel from closed to wide open is about 1mm less that the carb bore diameter, as at idle the opening under the front of the slide is about 1mm.  Ish.

The Sport 1100 had a /5 std, this one has /3.  Don't know if that's a good or bad thing.  Lots of the 41mm Malossi converted PHM 40 don't have pumps at all, and they're a "racing" carb.  And a trick when you're dyno tuning Dellortos is to pull the pump lever so you don't get any pump shot influence in your readings.  So you can do without them if you're not slamming the throttle open in an aggressive fashion (ie, doing roll on wheelies).  Where on earth is the fun in that you may well ask.  I would.

As an aside of some relevance, I'll add this from the Moto Guzzi Lemans 1000 manual.  It's just so delightfully delusional, and always makes me smile.

Dream on, my man, dream on.

Sunday, March 5, 2017

More Minnie the 400 Monster dyno runs

I took Minnie to the dyno today to see how the 2-1 works.  Not well as it happens - red is the 2-1 curve, blue the previous session with the std headers and Megacycle mufflers.

Pretty much dyno'd how it feels on the road - goes well under 8, no point going over.  I was going to set up one of the previously dyno'd Megacycle muflers to give just the change due to the 2-1 header, but didn't get to it.  I hadn’t revved it hard before the 2-1 went on.  Now that I have a tacho fitted to know how hard I am revving it, I can see that it would have been very unlikely that I was going over 8 anyway.  As such, I really didn't notice the now crap (ish) top end in comparison to the previous set up.  Maybe I need to make a twin muffler mounting bracket for under the tail and cut down the second Danmoto muffler to fit with original header.

I don't have any air/fuel for the original exhaust and Megacycle mufflers, as the bike killed the dyno on those trips.  The rpm and air/fuel were shutting down when we tried to run it.  After the last session I fitted resistor spark plugs, which you need to run with the Ignitech and which all these carby SS bikes (should have) had oem.  I assume that’s what made the dyno control happy.

First runs were baffle in and then baffle out.  I modified one of the Danmoto baffles I had.  It has 12 holes around it, and the total area of the holes was about the same as the muffler internal diameter anyway.  I machined the end cap of the muffler just a little to allow the baffle to slide in, and them machined a circlip groove to hold it in.  Of course, I didn’t have any circlips big enough to start with, so I bent up a round clip from coat hanger wire.  Gotta love coat hanger wire.  As below – without, machining, and with.

Made so little difference you’d have to call it none.  Then I found that the Showa fork spring preload tubes are a perfect fit over the Danmoto baffle, so I slid a tube over, tacked it on then cut off the original end cap.  The internal diameter of the baffle exit is now probably a bit under 20mm.  Again, not a lot of difference, but I ran with it. 

You can hear the slight change in these clips I took in the dyno room.  Not great sound, but definitely quieter with baffle from the bottom.

As expected, it hurt the bottom end a little.  Not as much as I’d hurt the top end though.  Baffling the mufflers usually effects the peak torque more than the peak power, but in this instance that’s a bit hard to see.

It was a bit (fair bit) on the rich side, so I thought I'd try it out without the airbox lid.

It was a bit better power wise, but the mixture change was pretty extreme.  More than I think I've seen before on a 2v motor.  Too rich to more too lean.

Then I tried it with lid, but without the snorkels.  That helped a bit, but still too lean on the needle.

I have some of the original 400ss carb springs, that are a lot lighter than every other OEM Mikuni spring I’ve seen them fitted with.  I might try them, not sure if that'll make it better due to the increased slide opening lifting the needle more, or worse because it'll have less vacuum over the jet and the needles aren't tapered enough anyway.  I do have some jet kit needles that might be the go.  Probably with springs as well - you’d just call that fitting a jet kit.
I rode it back from the dyno with one snorkel fitted and without the baffle.  It felt a bit stronger without it, but the missing snorkel may also have been helping there.

The Ignitech unit I fitted before this dyno session has the same advance as the std boxes.  Well (you know when you make assumptions and then later you think "oh"), maybe I should check that - it should have the same advance.  
I know that from the previous 750 engine testing that lack of advance hurts the top end and can give an exaggerated choppiness to the curve.

This early Ignitech TCIP4 has a delay that increases as rpm climbs.  The newer units (this one I've had since 2005 or so) don't.  I thought I had allowed for it in my curve, but maybe not enough.  I did have the oem boxes with me at the dyno, but my time was pretty much up there and I had to get back to work anyway so I didn't.  One thing I hate about not having my own dyno running is not being able to act on all the things you think of later when it's too late.

So maybe it didn't have enough top end advance, and it was rich anyway.  
Fairly extreme fuelling (well, air entry affecting fuelling) changes didn't make a big difference either, although it did go from too rich to too lean.  The last run I did had the mixture back at 13.5 or so in the crap top end area, so that pretty much rules mixture out.

Although I ran these same carbs years ago when it was a std 600, and I would have thought with a smaller engine it should be leaner due to less suck.  For some of the production years the M400 and M600 are fitted with the same carb spec (same part number).  I did shoot some video through the airbox lid without an air filter fitted of the slide, and it did look like it was lifting all the way up.  I was wondering if it would, given it's a pretty big carb for a 400.  Lots of fuel flying around too.

Through the snorkel hole

As it sits at work now (waiting for a nice day and time to go for a ride, it's pretty hot here now) it has one of the Megacycle mufflers fitted to rule that change out, and I'll put some oem ignition units in my pocket and fit them on the road. I really can't see the exhaust alone hurting it this much, as nothing I've done exhaust wise in the past has, but I'm often wrong.  And I do have concerns that the 2-1 merge isn't deep enough into the V of the original connector.  It may actually allow flow from one cylinder to go back up the pipe toward the other cylinder. Not so bad from the vertical as the pipe in is angled, but from the horizontal it can.  That's possibly an issue and not one I can do a lot about with this header set, especially now they’re ceramic coated.