Turbo Motorcycle Surging Problem

[presbychuck]

OK, A brief history. I turboed the bike several years ago and ran blow through carbs with great success, but wanted to do the EFI thing. Went with Microsquirt but did fuel only and had an excellent running machine for some months. THen I decided to go with timing as well. Long story short, I messed up my good tune, accidently destroyed every backup in a crash (automobile crash that destroyed the laptop, not just a computer crash) and cannot seem to find my way back. I was unsuccessful getting the timing to work and have gone back to stock ignition to try and reclaim my tune. However, while I've managed to get the bike running pretty well again, I have a serious surging issue that seems to occur at light and decel throttle settings (but the bike idles well). I calibrated the TPS a few times with little change and then replaced it to see if it was badly notched or something. But, No joy.

THe bike runs well wide open, and while surging at cruise the AFR guage is jumping from roughly 12.5 to 13.5. Having read many postings in which the accel enrich circuit seeme d to be the culprit I think I have disabled it as well as automatic Mixture Control in an effort to figure it out. But the surging remains. THe bike takes off and at WOT it runs like gangbusters, but at cruise or very light throttle applications it surges, even under decel. Here's my current msq, but I donlt have a current log file. Please help if you can.

[Bernard Fife]

pc,

I wasn't able to open your MSQ.

Surging usually means a lean condition. This can be due to too little accel enrichment, or too lean a VE table.

To check the accel, with the bike not moving, and in neutral, rev the engine at different rates. It should pick up smoothly, with coughing into the intake. If it does 'cough', then you need more accel enrichment at the speed you were opening the throttle. I generally start with a very fast opening and tune the top accel bin, then work my way down.

Also, make sure the MAPdot and TPSdot thresholds are high enough that they aren't triggered by noise during steady state conditions (examine a log to see if this is happening).

For the VE table, the surging will occur at steady speeds and loads. It will feel like someone is alternately pushing then pulling the bike. This can happen if the area of the VE table you are using is too low, or too 'rough'. So you might need to raise and/or smooth it there.

EGO feedback can also do this if it isn't configured or tuned optimally. Try turning it off (set 'Controller Step Size(%)' to zero) and see if that help.

Lance.

[presbychuck]

pc,

I wasn't able to open your MSQ.

Surging usually means a lean condition. This can be due to too little accel enrichment, or too lean a VE table.

THis was actually my first thought and what I really expected it to be. I've had difficulty with the accel wizard from the get go.

To check the accel, with the bike not moving, and in neutral, rev the engine at different rates. It should pick up smoothly, with coughing into the intake. If it does 'cough', then you need more accel enrichment at the speed you were opening the throttle. I generally start with a very fast opening and tune the top accel bin, then work my way down.

Even with EGO off and the AE configured to do nothing I have an excellent idle, smooth and crisp accel with no coughing at all... then when under a light load (i.e. cruise condition) it commences the surging as you describe, a pushing and pulling effect. I guess if I wanted anyone to be able to open the file I needed to include that I am running the megasquirt-II.ini.2.890 code. However, in the MSQ file those are not shut off I do not believe.

Also, make sure the MAPdot and TPSdot thresholds are high enough that they aren't triggered by noise during steady state conditions (examine a log to see if this is happening).

OK, this sounds like a good plan to me. I've struggled with how to fill in the blanks on this table anyway. The problem just suddenly came up after trying to go with ignition as well and now I am fighting it despite reverting back to what was a well functioning ignition tap.

For the VE table, the surging will occur at steady speeds and loads. It will feel like someone is alternately pushing then pulling the bike. This can happen if the area of the VE table you are using is too low, or too 'rough'. So you might need to raise and/or smooth it there.

It seems to be pretty smooth looking at the numbers, and my AFRs are all indicating on my gauge the 11.8-13.8 range. When the surge is occurring, the needle is jumping between 12.5 and 13.5 for the most part... of course the actual AFRs could be farther away with the needle lag time making the discrepancy look far less. Fattening it up is an easy enough check to see if it makes a difference. I'm also wondering if my LC-1 has perhaps taken a disliking to me.

EGO feedback can also do this if it isn't configured or tuned optimally. Try turning it off (set 'Controller Step Size(%)' to zero) and see if that help.

Lance.

Hmmm. I thought I just turned this off by disabling it. I'll have to go back and check on this one.

[presbychuck]

THanks for the help Lance,
I finally got to work on it yesterday and was able to disable all autocorrecting and the accel enrichment and set about getting a better base tune. Just shutting of the accel stuff eliminated the surging, but I felt the table probably was too lean in places anyway. So, after getting the VE table fattened up a little I used my laptop and TUner Studio on autotune to clean it up, which seems to work much better for me than letting the Microsquirt do it. Still a little fat in a few spots, it was running well without any surge and I decided to try to turn the accel enrichment back on to get that rebuilt... but I am struggling with it. Not so much with HOW MUCH fuel to add, but with setting the sensitivity of when it's going to add something.

I currently have it set like this and it is far too sensitive.

Throttle Position vs Manifold Pressure is TPS driven 40%
MAPdot Threshhold 50 Kpa/sec
TPSdot Threshold 50 %/sec

Any suggestions?

Other than this issue the bike is running very well and performance is back. If I can just get the accel enrichment smoothed out it will be marvy.

Then it'll be back to trying to get ignition working on it. THanks for the help again.