stoich

[kev_rm]

I'm running a wideband and I swear this motor will not run well at 14.7:1. It burbles at anything over 14:1. Idle is best at 12.8:1, which is to be expected, but I need to run closed loop 14.7:1 cruise because I have a cat - the motor just does not like that lean of a mixture it even at 3000rpm under zero load.

 

Edit: Did run fine in closed loop mode before MPI..

 

Anyone else running MPI have this issue?

[jr_ss]

Turbo motors do not run stoich. They are all rich to compensate for boost. What reason do you need to run stoich for anyways? Just have it run to the closest to stoich it can and let it be.... I haven't got a wideband yet, but hopefully soon I'll be getting one.... Mine runs about 2 bars rich at idle and about 3 or 4 under boost...

[mikec]

Stoich gives the best emissions (cat is most effective at stoich) but a little rich gives more power and is pretty much essential on-boost to avoid detonation.

 

For a stable idle, many cars to run rich as well... stoich doesn't work quite as well at very low RPMs and when the cylinder air volume is low thanks to closed throttle plates. There isn't much air/fuel molecules in there to burn! Unless you get a REALLY GOOD spray pattern (good fuel mix) at idle you'll need to be a bit rich. For part-throttle cruise, stoich is the target to get good emissions. You don't need to be rich at part-throttle cruise to get a good burn; if it weren't for emissions running a little lean for more MPG is the way to go.

 

Potential reason your car doesn't like stoich at cruise: uneven injector flows, poor fuel mixing, etc. One cylinder might be leaner than others for some oddball reason (bad injector, mismatched injector) or way richer... but your wideband sensor is averaging the 4 cylinders to a final reading. This hides a bad cylinder. Try running stoich at cruise for a while - go for a half hour drive where you can maintain a steady speed without stop and go crap. Pull over and quickly shut down, then read the spark plugs. They ought to look the same... if one cylinder has a different air/fuel ratio it'll show up on its plug.

 

mike c.

[ESIrType?]

I don't see where cruise and boost is an issue. While cruising, your engine should not be boosting. So in a sense it's acting as a NA engine. I would think you would beable to lean a certain RPM/KPA range out for cruising. I'm not really sure why it doesn't want to run at that range. Mikec has some good advice though!

Are you running a MegaSquirt also?

I wonder if rising the fuel pressure a little to may help. What is your fuel pressure at idle?

 

Shawn

[kev_rm]

All - not talking about running stoich at boost here, talking cruise. I am running 12-13:1 at anything over 150kpa or 75% throttle.

 

mike - good stuff. I was thinking along these lines as well, and I will check it out. Theoretically injectors are matched (Racetronix) but I will do fresh plugs plus a cruise to verify it's not one cylinder. I can also check the injector signals to make sure nothing is goofy on the megasquirt side.

[Tom_Cat]

Some things I can think of.

 

What is your “EGO step†set at? Anything over 2% may cause it to over shoot its trip voltage by a very large margin.

 

What is your “EGO count†set at? Every 22 ignition events works best in my car.

 

Try 4 injections per cycle, this will help with the idle and you may need to readjust the “Required fuelâ€. Remember a cycle is two turns of the crank (or four ignition events) not one, so you would have one injection per ignition event. :wink:

 

Set the EGO trip voltage to .4V (2.5v for wideband), I run mine at .2V with no problems.

 

If you are using the Wideband for the EGO make shire it is set to Wide Band on the “enrichments page†in your tuning software.

 

If I rev 3K in neutral and the EGO kicks in my RPMs go up and down by about 300, on the road I can’t tell when the O2 is online.

 

Hope this is of some help.

Tom Cat 8)

 

PS. Can you get a data log? With the log you could see exactly what is going on when the car acts up.

[88whitestarion]

I don't know if any of you have an EGT gauge, but if you do, you have probably figured out that these engines liked to be bathed in fuel, even at idle and cruise.

 

I don't know what it is about these engines(or at least my setup), but anything above the 12's (especially at cruise) will cause the exhaust temps to go up about 200 degrees F. This extra 200 degree is where the turbo and header start to glow. I have advanced and retarded the timing and it doesn't seem to matter. The only thing that keeps the cruise exhaust temps down is running rich. The funny thing is, it runs very well in the 11's to low 12's AFR. I decided to quit fighting it and just run it there.

 

Dave

[eeaston]

I don't have any suggestions, but I can tell you that my engine will cruise at 16:1 with only very slight surging at low RPMs. I idle around 13:1 just fine at 7-800 RPM.Definately try logging and see what conditions cause trouble.

[88whitestarion]

I don't have any suggestions, but I can tell you that my engine will cruise at 16:1 with only very slight surging at low RPMs. I idle around 13:1 just fine at 7-800 RPM.Definately try logging and see what conditions cause trouble.

 

Do you know what your EGT's are running when cruising? I am just asking because it appears we are running similar set ups. My engine temp never gets hot, but my exhaust temps run hot enough to cause the turbo and header to glow when I try to run in the 13's and leaner range.

 

Also, what kind of header are you running?

 

Thanks, Dave

[eeaston]

I haven't got EGTs yet, although I did install bungs in each runner when I built the header. The header is an equal length job I built from schedule 40 stainless.

 

I expect that my EGTs are probably fairly high as well. You have to remember that you cannot burn more fuel than 14.7 so with anything richer the excess fuel just becomes expensive(but necessary under boost) coolant.

 

What EGTs are you seeing?

[yokomo]

Do you know what your EGT's are running when cruising? I am just asking because it appears we are running similar set ups. My engine temp never gets hot, but my exhaust temps run hot enough to cause the turbo and header to glow when I try to run in the 13's and leaner range.

 

Also, what kind of header are you running?

 

Thanks, Dave

 

 

mine seems to be at 600-650 celcius crusing

and around 750-800 C if im on it a bit. ive had it hit 850C and my EGT warning light came on!!

 

my exhaust housing will glow also.

 

am i i too lean???

 

also with the fuel map i have right now, feels like i just run out of power at 5K rpm. then agin i havnt reall fooled with it, due to my lack of knowledge using megatune, im a stand-alone bafoon! :evil:

[88whitestarion]

I like to keep my EGT's at 600 C or under when crusing around at 30 to 45mph. EGT's near 700 for any extended period will cause the header and turbine to glow and I'm concerned about damage to the header and turbo.

 

At idle, and after the car is fully warmed up and has been driven for awhile, the temps will slowly go down to around 475 C after idleing for a few minutes.

 

Under full boost they have never been over 700 C.

 

Becareful, anything in the 800 C range sound extremely hot to me.

 

It also depends on where you have your sensor probe. I have mine in the top of the downpipe. If you have yours located in the exhaust manifold, your readings are probably going to be a little higher.

 

If I try to run in the 13' or leaner range when cruising, the temps spike up to 675 or so. That's the glow zone, and I don't care to run there. So, to be safe I run mostly in the 12's at idle and cruise.

 

I might try a water injection system to see if I can run a leaner A/F and still keep the temps down. Water is definitely cheaper than $5 a gallon 112, which the only gas I run.

[conquestpa]

If you have a wide band O2 sensor do you still need a EGT sensor? Or can WB02 usually do EGT?

 

:?:

[kev_rm]

Potential reason your car doesn't like stoich at cruise: uneven injector flows, poor fuel mixing, etc. One cylinder might be leaner than others for some oddball reason (bad injector, mismatched injector) or way richer... but your wideband sensor is averaging the 4 cylinders to a final reading. This hides a bad cylinder. Try running stoich at cruise for a while - go for a half hour drive where you can maintain a steady speed without stop and go crap. Pull over and quickly shut down, then read the spark plugs. They ought to look the same... if one cylinder has a different air/fuel ratio it'll show up on its plug.

 

mike c.

 

BINGO. #4 running rich. It's a major mystery at this point as I've swapped injectors, swapped injector wires, and checked the compression relative to #3 and it's all good. Stumped.

[ESIrType?]

[

BINGO. #4 running rich. It's a major mystery at this point as I've swapped injectors, swapped injector wires, and checked the compression relative to #3 and it's all good. Stumped.

 

Possibly a dirty ground/signal? Maybe a bad wire with high resistance on it?

 

Shawn

[mikec]

Try a few basic/simple tests:

with a helper holding the throttle constant at around 3000 RPM... listen to each injector one by one. Use a mechanic's stethoscope if you have one (5 bucks at Harbor Freight) or a long screwdriver or metal rod held close to your ear. See if the "clicks" from injector #4 sound any different than the other injectors. If so, it's ECU caused. Sounds the same? Good... sortof. gotta find some other source of the problem. Another way to check injectors: get a 0.47 microfarad capacitor (often abbreviated "uf" where the "u" is funky) rated for 50 volts or more, a 1000ohm resistor, and a in-ear earphone bud. Wire all three parts in series:

use the "" ends as probes and hook them to the two leads for your injectors... you'll be able to hear the on/off pulses from your ECU. All 4 injectors should have the same frequency and should sound about the same at any given RPM. (note: not all earphones have +/- (center/outer) leads... the polarity really doesn't matter)

 

Eyeball the cyl head for anything obvious.., intake/exhaust rocker arms swapped by accident? Unplug the brake vacuum booster hose and plug the port in the manifold... see if something is drawing off a lot of air from the #4 cylinder intake runner.

 

Verify decent spark at that cylinder too... good wire, not arcing to some other ground (run engine in the dark and look for glows), plug is tightly screwed into cyl head, etc.

 

good luck

mike c.

[Vanishing Point]

That ear phone thing is cool Mike I need to make one of thoughs. 8)

I dont remember my MGsquirt stuff, but are your injectors batch fired?

Anyways I would switch the injector and retry, if you have the same problem in that cylinder then you have a bad injector. Sounds like a new setup so who knows.

If #4 is still the problem then you have a fuel supply issue to the other 3 or a vacum leak or air supply problem.

Hows the idle?

A vacum gauge may give a clue. If its low less than 15"hg it maybe a sign that you are getting air somewhere else to feed 1-3 and starving 4.

Another quik check is to spray carb cleaner around at spots on the intake and listen for an rpm change. Also check vacum hoses and brake booster.

If the MGSquirt is batch fired you can pretty much eliminate the ecu or tuning causing a miss match.

On last thing when you pull the injectors make sure nothing is blocking the spray pattern.

Tony

[Boosted_One]

Dunno if it helps but my ride loves to idle about -12.5'ish

 

I run leaner (by design) on light accell and off accell...it doesn't matter if you run lean on a super light high vaccum load.

 

Under boost I see about 12.3 - 11.4 and it never skips a beat.

 

Just some of my paramters that my motor likes.

[heefner]

I like to keep my EGT's at 600 C or under when crusing around at 30 to 45mph. EGT's near 700 for any extended period will cause the header and turbine to glow and I'm concerned about damage to the header and turbo.

 

At idle, and after the car is fully warmed up and has been driven for awhile, the temps will slowly go down to around 475 C after idleing for a few minutes.

 

Under full boost they have never been over 700 C.

 

Becareful, anything in the 800 C range sound extremely hot to me.

 

It also depends on where you have your sensor probe. I have mine in the top of the downpipe. If you have yours located in the exhaust manifold, your readings are probably going to be a little higher.

 

If I try to run in the 13' or leaner range when cruising, the temps spike up to 675 or so. That's the glow zone, and I don't care to run there. So, to be safe I run mostly in the 12's at idle and cruise.

 

I might try a water injection system to see if I can run a leaner A/F and still keep the temps down. Water is definitely cheaper than $5 a gallon 112, which the only gas I run.

 

My car idles at 800 and I have the probe at the exit of the turbo in the top of the down pipe (sounds like the same spot). Under full boost WOT I've seen 1500 on that probe and 1750 on the probe in the manifold tube at number 4 cylinder. I can't believe you car never sees above 800 WOT. Maybe they are different sensors.

[kev_rm]

I think fuel is a red herring. I've swapped injectors, injector bank wires (the megasquirt is BANK fired, 2 banks), eliminated the vacuum port on #4, checked the plug wires, done a compression and leak down test, checked the injector sound with a stethescope. I think the plug being black is caused by oil as it has definate oil residue after 5 minutes. Since compression and leakdown are excellent, guessing valve seal. This, however, does not explain why it won't run well at 14.7:1. Perhaps I'll double check my wideband with a narrow band.

 

This is frustrating.

[kev_rm]

I can't believe you car never sees above 800 WOT. Maybe they are different sensors.

 

Maybe they are different units

 

800C = 1472F

[eeaston]

Kev-

What WBo2 are you running? I found out that the display for my Tech Edge unit is terribly inaccurate, I have to use the numbers from megatune and my datalogs. Is there any way you can check your meter against a known good one? When my display reads stoich, the actual is close to 17.5:1.

[Boosted_One]

Kev-

What WBo2 are you running? I found out that the display for my Tech Edge unit is terribly inaccurate, I have to use the numbers from megatune and my datalogs. Is there any way you can check your meter against a known good one? When my display reads stoich, the actual is close to 17.5:1.

 

My tech edge was right in the window as my dynos WB O2.

 

I use the Tech Edge display and the Tech Edge ECU.

 

Wonder why yours is so far off???

[kev_rm]

I'm running plx m300, new sensor. It was off from the wideband at the dyno, but I have a cat. It's easy enough to check with a narrow band sensor, I still have the upper bung.

[eeaston]

Kev-

What WBo2 are you running? I found out that the display for my Tech Edge unit is terribly inaccurate, I have to use the numbers from megatune and my datalogs. Is there any way you can check your meter against a known good one? When my display reads stoich, the actual is close to 17.5:1.

 

My tech edge was right in the window as my dynos WB O2.

 

I use the Tech Edge display and the Tech Edge ECU.

 

Wonder why yours is so far off???

 

Some tolerance error. They have instructions on how to bias the units output to compensate for the display error, but then the MS logged readings would be off. I'm pretty disgruntled about the whole mess. Their new units use a digital connection to the display so there can't be an error there, but there's a long thread in their support forum about the problem. I need to find a calibrated unit and just verify the MS readings. SUPPOSEDLY the output of the unit is correct, but I'm still leary. And I was wondering why I had severe detonation at richer than 13:1.