Basically this only happens when the car is warming up.

If I hold the throttle at 3% steady (about 2000rpm) during warm up, it gets leaner and leaner, the rpm's stumble then it recovers if I jab the throttle a few times.. but this repeats again if I hold my foot steady...

Easily seen here:


It seems odd because the PW does not change... or at least it appears that way... Are any calculations done that affect PW after the figure we are getting here?

A couple more screenshots may be helpful:
http://stuff.pw.cx/odd%20leanout%20h...%20steady2.PNG
http://stuff.pw.cx/odd%20leanout%20h...%20steady3.PNG
http://stuff.pw.cx/odd%20leanout%20h...%20steady4.PNG

The setup of my EGO sensor is just for informational purposes I think - here are the settings below:


I would have thought if the EGO sensor had anything to do with it though, it would show up in the PW's...

Any thoughts would be massively appreciated This would really help me tune the startup- right now no idea what is going on !!

(MS2 Extra 1.x, 2nd VR circuit, stock CAS, FC coilpacks, Innovate O2 sensor kit from diy)

Cheers!

Paul.

 

well, as the engine warms up, you should be injecting less fuel, because the fuel vaporizes better as the air and intake walls etc heat up. What are your warmup enrichments like?

 

Yeah thats right, however this occurs in about 7 seconds (from rich to lean), and you can see that the coolant temp does not change at all during this time... my warmup enrichments are quite minor - ill get a screenshot tomorrow of those. are you saying that perhaps i am injecting too much fuel? im at quite a loss for what is going on.. (im glad that once it is warm it seems to be fine at least) - perhaps that can help to narrow it down..

 

What kind of intake manifold are you running? You might be wetting-out the intake manifold on the accelerator pump shot and then running lean after you use up that fuel.

 

Might have something to do with wallwetting, although you will only be able to do something about that with EAE or X-tau.

Ken

 

Hmmm ok - this is my intake/throttle body setup.


EFI Hardware / (similar to injection perfection TB on top), then straight down and into the engine.. (I think this is similar to an ida setup). So there are 4x550cc injectors, 2 on each side angled in just under the butterflies.

 

It takes a few seconds to stabilize the fueling, as excess fuel at startup has wet the runners. Tickling the throttle fires accel enrichment shot, re-soaking the walls, which gives another few seconds of decent mixture before leaning out again. Note this effect will be more exaggerated in your install due to the position of injectors as compared to stock. In summary, it looks like the classic lean condition.

It's not clear from your post whether this is actually a problem for you. Does the car warm up fine when you are not holding the throttle open that 3%? If it's also a problem during normal warmup, then play with after-start and/or warmup enrichments to solve.

BTW, map signal looks pretty noisy. Has that caused any tuning difficulties?

 

Thanks for that description renns, makes more sense to me what is happening now!

If I leave the throttle at 0, or even hold it at 3% it just stalls from being too lean, so in order to warm it up currently I have to pulse the throttle. That said, when it is quite cold it is not an issue, it is as it warms up a little now that I think of it.. Once it is closer to normal running temp it seems to be dying - so it must be that the walls are wet and the fumes from that fuel are feeding the engine..

I didn't think I needed it to be so rich, because already it is running quite rich at idle once it has warmed up... perhaps this is just the way it is with this setup.

Yeah the map signal is quite noisy, the engine is extend ported and at this stage can only get a map signal from the rear rotor runner (I do have plans to drill into the front rotor runner and split the vac line, then add a reservoir to smooth that signal. So far with my tuning I have made sure the values are quite smooth, so I have not noticed any major problems caused by this, but definitely when I get into finer tuning I will resolve that.

I will play around with warmup enrichments, and i'm about to read over the megasquirt tuning guide again to help. I guess the engine is more likely to stall from running lean - running too rich is not really a problem? (just on fuel cost)

Cheers!

Paul.

 

I'm definitely paying attention to this thread because my brother is using the same basic setup. Weber mani. with the injection perfection 48IDF throttle body and water/air intercooler that bolts on top of it. I've been really wondering if acceleration stumble will be a problem as well.

 

That section of the map may be way lean, and not normally affect drive-ability, as it is normally only seen when coasting. In fact, in the early days of MS, we leaned the low map/high rpm areas on purpose, as it dropped fuel requirements during coasting. There are other features like over-run fuel cut in new codes that reduce the need for this today. In any case, I'd suggest tuning that area of the VE map once the engine is warm to get a solid baseline. There's no use messing about with warmup enrichments if the base table isn't nailed yet.

Again, tune that area of the VE map when the engine is fully warm. Then move on to the warmup and after-start enrichments. I wouldn't bother tuning this area with wideband readings. Jack the throttle open to a fixed position that gives the 2k rpm target, and then slowly adjust VE bins in that region until maximum engine speed is achieved. This is very easy to do if using an embedded code that returns rpm in 1 rev increments, rather than the rpmx100 values returned with earlier codes. It could be done by ear as well.

The engine will 'load up', and start to eventually sputter and misfire if running very rich. On the other hand, surging and eventual stalling will occur on the lean side. With a bit of tweaking you'll find the sweet spot for your setup. Read up on the inter-relationships between after-start and warmup enrichments. With all the adjustments available, you should be able to tune it to warm up properly with no 'throttle tickling' required.

 

Thanks renns!!! I got it to start now without needing any throttle, and it even idles :P

Basically the crank pulse map was dumping in way too much fuel, so i scaled that back by more than half.

The second issue was that my warmup enrichments were not rich enough.

I think to really get it going smooth now I need to spend some time on a dyno But it's much better now.

One thing - when I let off the throttle from high rpm, the engine usually stalls. My friend Drew said that I need a dash pot, basically to stop the throttle completely slamming closed and starving the engine of air. Do you think this is the way to go, or could part of my tuning be responsible for this too?

Thanks again for the advice, i'm very pleased with the turn key start

 

I usually use the BAC valve in combination with my spark table and VE table to keep the engine from stalling when slamming the throttle shut.

something else that can be done is if you're using overrun fuel-cut, you can make it bring fuel back on at a higher RPM.

Ken