Weird fueling issue w/FAST... ATS corr related??

[JeffB]

I'm experiencing an extremely rich condition right around redline... this causes a miss (i don't have any rev limiter on the car right now)... the dyno's wideband verifies that the afr is flat until the last 100-200 rpms and then it drops like a brick... anwyay, if you look at my log going down the track you can see that i get to roughly the same rpm and MAP in each gear... however, in first gear its showing an injector duty cycle of 95%, in 2nd gear it only gets to 83%, in third its 90%... the gears with the higher duty cycles were missing more... the only thing that is changing significantly is the air temp (starts at 110 F and gets up to 185 F)... my ATS correction table is all 0's... but what does this mean? i'm in speed density mode... does the computer still have a base correction that its using for air temp? is the ATS table just to trim that? or if the ATS table is all 0's do i not have any ATS correction at all?

here is my log:

http://members.cox.net/blownz/0823p3.log

here is my config file:

http://members.cox.net/blownz/camaro9.gct

anybody have any other ideas as to what would be causing this excessive richness? the dyno guy keeps telling me that if it was just ignition related i'd be seeing LEAN not rich... just put on new valve springs (initially thought it was valve float), new distributor, new coil... plugs and wires seem ok...

thanks!

 

[Craig Smith]

The speed/density calculation figures air temp into the equation regardless of what you have set in the ATS correction table. As you asked, that table is in addition to what already happens.

It sounds like as you approach your shift point you are starting to touch a cell in the VE table with a number in it that is way too big.

 

[JeffB]

i know... that's what i thought at first... but actually, when i log VE you can see that the VE is going down right there at the end... my columns slope it down since its past peak torque... i went through several iterations of lowering the VE values in that area anyway and it didn't lean it out at all... this was today on the dyno... the gct i posted wouldn't reflect those changes... again, the main thing that bothers me is seeing basically the same engine conditions (load and rpm) but drastically different duty cycles (85% vs 95%)...

 

[Craig Smith]

Another thing to consider when this happens is your ignition system. I don't necessarily agree that an ignition problem would cause a lean condition. If your ignition can't completely burn what you are putting into the engine, I would expect to see it show a rich condition. You get the boost and the RPM up high enough, it will cause ignition breakdown if the system isn't up to the task for some reason.

It would be interesting to close the plug gap up a ways and see what the results are... if it helps, it tells me you are blowing out the spark.

 

[JeffB]

yeah, the o2 showing rich would be my intuitive guess... however, everyone says that the o2 sensor only senses o2, so if less fuel is burned, there will be more o2 left over... beats me... i will say this, when i spray a 50hp shot of nitrous it doesn't cut out any sooner... if it was just related to not being able to spark, i would expect the "crap out" rpm to drop even more with the nitrous flowing... not trying to sound negative, i definitely appreciate the responses... i've been fighting this one for a while... i'm running non-projected plus gapped at 0.030"... i was running them at .028" before and it seemed the same, i opened them up a bit to improve idle...

 

[Spooled]

Just a reflection after looking at your gct file...closed loop gain is WAY too high. I'd try more like 18 instead of 40. I'd think your corrections are all over the place. ALso, wires can seem ok and are not. If they're not new, i'd change them. They like to cause a slight miss if not in perfect shape.

 

[JeffB]

i don't use closed loop... my sensor is sometimes flaky so i don't trust it...

 

[Spooled]

Oh, ok. What kinda cam do u have in it? What kinda rpm are we talking is redline? It may be that your trying to push the motor outside it's powerband and power is falling off so sharp that you need to drastically lower your VE there to lean it out some. That is...if i'm understanding the problem correctly. Just a thought

 

[JeffB]

could be... the cam is 230/242 .571/.587 114LS... it breaks up around 6400... its a hydro roller cam... my engine builder said he's got this same valvetrain doing 6900 on a non-boosted motor... so take off a little for the boost pushing on the valve and i'd expect to get to 6600 or so... the springs are only a week old... i have a rev kit too that i'm going to install...

there's really two issues here... the one is the miss and that's anyone's guess... but the other issue is how can the ECU be doing such different duty cycles under seemingly the same engine conditions? unless someone can see otherwise from my log, it sure looks like that's what's happening to me...

 

[Spooled]

I wouldn' t take that cam much past 6400. I'd think you would need a little more duration to get it to run well up there. Also, concentrate on what the log does in 3rd gear. Sometimes what it does in 1st and 2nd come and go so fast, the results are less than accurate (especially 1st). Some of that DC in first could be from the added AE fuel. What does the power curve look like on the dyno? Is power allready starting to fall off at about 6300 (before it starts missing?) If so, i'd say your running outa useable rpm. THe heavy hyd roller lifters are what limit rpm. Going to solid will increase your useable rpm. WHen you get much past 6500, i'd definitely recommend lightweight springs/retainers (titanium), along with a rev-kit. I know i'm not helping much but these are just some things to think about. I have a 228 duration at .050 in my 383 and dutweiller said it'd run out at about 6000 or a hair over. I really think your outa cam if you wanna turn it to/past 6400. I'd shift more at 6300 at most. I think you'd have better results. Hope this helps a little.

 

[JeffB]

sorry i didn't see this sooner... i'm making peak/max power at 6300-6350... then 100rpms later its missing and falling off... i have titanium retainers... i'm going to install the AFR hydra-rev kit now to see if that helps at all... i realize the cam isn't optimal at 6500 (though if peak power is 6350 it can't be TOO bad) but i need a little extra rpm to get through the traps... i shift 1st and 2nd at 6300... the other thing is with my setup (centrifugal blower) the higher you rev the more boost you get so you kinda cancel out breathing inefficiencies a little more than a turbo setup with a flat boost "curve"... if i was making 15psi across the entire rpm range (vs. just at redline) i might have peak power at a lower rpm where it breathes better... and i'd certainly have more midrange torque...

 

[Spooled]

Are you sure you have the right springs for the cam? Did your engine builder put those same springs in your motor that he has in his NA motor that runs to 6900. If so, you might not have enough pressure with the boost trying to hold the intake valve open, i.e, valve float. Try that rev kit, theyr'e suppose to really help. It's just like adding spring pressure but it's not pushing down to possibly collapse the lifter. That's about all i can tell ya. Sorry I can't help more. But i think your on the right track. Let me know waht u find out!

 

[bobc455]

I'll second Spooled's suggestion of reinvestigating spring pressure- a valvetrain for an NA car won't work for a boosted car.

This would be especially true if your boost increases with RPMs.

-Bob Cunningham
bobc@gnttype.org

 

[JeffB]

the valve springs are a "secret" brew that my engine builder puts together... all i know is i picked up 35rwhp with the new springs (and about 100rpms) vs. the old springs, so at the very least they are a step in the right direction... seems to confirm that it is valve float related i guess... shows up on the wideband as extreme richness though... anyway, i'll keep you posted on the results...

thanks!

 

[Chyke]

Well

Make sure your o2 is functioing, set your AF table, put it in closed loop make a blast and hit the L key as many times as you can. Right up to and including where its funcky. This should help.. Well maybe... Than take a look at the log.