tmoney223

iTrader: (2)

I have everything in my sig and PRC 225cc heads.. The question is at 1500-2500 RPM's at steady throttle it feels like its jumping forward or surging, if that makes any sense... Is this due to the cam being so big or is it still a tuning issue..AFR is around 13-14.. And I'm not the tuner just trying to get an idea what could be doing this..thanks

redtan

iTrader: (5)

It's a little bit of both...that certainly a pretty health cam even for a 370, but tuning it to perfection will surely help.

AFR is ok, might need more timing to help with the surge. Although I doubt you'll be able to tune that cam to be running 100% smoothly at those RPMs.

tmoney223

iTrader: (2)

Yeah the cam is pretty big because I'm throwing a 250 shot on it..yeah my tuner is pretty picky about making it perfect which is cool by me..lol..and I kind of figured there will be some choppiness down low just didn't know if it was going to be that bad...thanks for the info and il keep putting updates if I have any more problems..

decipha

As stated give it more timing and if you hadn't already, give it more IAC airflow (dashpot), that will eliminate most low load bucking issues

sweet-94z28

iTrader: (30)

To get it smoother, I would try to make all of the timing in that area very linear/smooth in transitions so that way the timing does not bounce. Then I would possibly pull a little fuel and lean it out a fuzz.

I'm assuming the tune is open loop speed density as well?

salemetro

iTrader: (5)

I'm glad Tmoney asked this, as I've never tuned a car with this much cam in it....and was curious myself. It's a pretty darn lopey ride down low! lol

The car logs to within 2% of commanded AFR throughout the entire VE table up to 4k.....currently in SD mode. I spent a great deal of time on the VE tables to make sure it was right (steady state capable dyno), and the car sees roughly 30-ish* in the low rpm (1600rpm) cruise regions currently. I have commanded as much as 50* through the VCM controls to see if it would smooth out...with minimal, if any improvement. I have not yet had time to power tune the timing tables overall, but regarding the cruise regions.... I'm left with the conclusion that this is as good as it's going to get with an M6 car, but would not be much of an issue with a stalled A4. I'm currently logging/working on the idle....RAF,ADAPTIVE, ETC...

I welcome others thoughts and experiences.

ctd

iTrader: (1)

salemetro, what tuning software are you using?

I've had some luck with going the other way with the timing, maybe in the 21-24* with no transitions between the idle & timing tables or rpm columns & dyn/cly/air rows.

salemetro

iTrader: (5)

I've gone as far back as 18*..car absolutely hates it. More timing is definitely better here. I've also commanded fueling on both sides of Stoich....car definitely prefers a tad lean here at cruise in these regions. Idle and main spark tables match. I'm using HPT.

ctd

iTrader: (1)

I'm sending you a PM with my email.

jimmyblue

iTrader: (11)

First thing is, at low RPM the indicated AFR is not the
AFR "in the hole". With a big cam the exhaust gas has
excess oxygen in it at low RPM and the meter reads
lean as a result. So tuning to a number makes the
actual AFR where it counts, rich. And rich makes idle
RPM response slow which destabilizes the idle RPM
control loop.

More spark gets some of this back, but too much
more can put you on the wrong side of adaptive
spark, past MBT and this is "positive feedback"
which again can be destabilizing - especially if some
of the stock table stupidity is left in place. Your
sum of max adaptive underspeed advance and
table advance has to remain below MBT (which
you don't know other than by results) advance.

The effects of overlap air also spoof the NBO2
sensors and push closed loop fueling rich. This
has to be addressed separately, as does the effect
of long tubes on sensor response.

tmoney223

iTrader: (2)

Thank for all the feed back guys I know my tuner appreciates it also!!

salemetro

iTrader: (5)

Interestingly, in the areas that are at fault (55-65kpa @1200-1600rpms)....the fuel trims are PULLING fuel like mad....but only in those areas. Everything else around is seems to be workable/tunable in the VE tables. I'm not sure why it just keeps pulling fuel. I've actually gone as far as pulling out fuel based on what the trims are doing....and it just continues to pull fuel. Eventually, it get's to the point that it appears obvious to me that the car wants more fuel....even though the WB and trims are showing "rich". I've tried commanding more fuel in the VCM controls, and am able to get it to smooth out a bit (chop never entirely goes away)...and played with timing as well.

At this point I'm not sure how I'm going to be able to keep it in CL below 2k, as the trims will just keep pulling fuel based on skewed data from the O2s.

But I'm still searching!

I'll try to post a log file either tonight or after I get back in to town next Wednesday.

salemetro

iTrader: (5)

So....solution found. 3 words....anyone have a guess??? Yep, you got it....corrupt tune file.

Off all the things...i've had issues with bad files before, but not like this one. So...long and short of it is, Tmoney has his car back...albeit in SD mode, until I can finish the tune when I get back next week. I was able to finish the VE table to 4.4k, and he's got a low rev limit, and anemic timing right now. Im looking forward to seeing what it'll put down when completed....but for now, he can throw some miles on it. Thanks for the input folks, but it looks like all is on the upswing now