93 LX Notch, 427 Sbf, N/A, PIMPxs

Hello Steve, all,

I've been following your thread in the background over many months, knowing that eventually I'd get away from the A9L w/SCT burn in order to help me get a better handle on doing my own tuning. Yourself along with other members have helped me with what I consider a pretty decent start as far a my very novice tuning expertise is concerned. I and many others can't thank you enough already for your time and knowledge throughout these threads. You've probably saved many engines! I settled on the PIMPxs, and so far it's been a fantastic decision!

My concern is with lean hot starts, ie. gas station fill-ups etc.... I've got my VE tables fairly close with the help of the auto tune function and manual inputs while reading logs. I have my a/f at around 13.5 at idle, 14.7 at cruise, and I'm still working on WOT with the goal of getting it to around 12.5 (still a work in progress).
So far I'm pretty close right now to my desired values, that's until I turn the car off for any less than 1 hr. When I restart the car after a short cool down, the Idle will be around14.5-15.5 and will hunt slightly for the first 10-15 secs, oscillating a few hundred RPM's (not stalling or even close to stalling). It eventually settles down to around 14 at idle, but will cruise around 15.5-16.5 on the a/f gauge (I just calibrated the gauge once again this week). It does eventually settle in to my desired values after about 5 mins or so of driving. Another odd thing I've noticed is when I start to get the a/f gauge doing the hot start lean issue as described above, most of the times I turn the car off and restart it immediately and the problem will sometimes disappear.

I thought the fuel lines and subsequently fuel rails may be getting heat soaked, so last week I put heat wraps around any line that would come anywhere close to the header. This made little to no noticeable difference. I started fiddling with the ASE, but honestly I just don't know enough to trust myself messing with that at this point. I'm still very much learning this system, and mostly can understand what you're describing when working with others on their tunes in this and other threads I've come across, but I'm still very much a green/noob. Was wondering if you could find time to have a look at the tune to see if anything abnormal stands out? Also, possibly steering me in the right direction in regards to this hot start issue.

I've attached my tune along with a short log of cruising and a couple short WOT bursts. I'll attach a hot start log in the very very near future. I haven't gotten around to logging this hot-start issue just yet. I'll post one up soon.



93 LX
Boss 351w block stroked to 427cid
Edelbrock Victor Jr heads (port work, springs upgraded)
Super Victor intake (port matched)
90mm Throttle Body
Comp Cams custom grind, .629" intake, .626" exhaust, 242 - 250 dur
44lb Accel Injectors
255lph in-tank fuel pump
-8an feed, -6an return
Pressure regulator set to 40 psi with vacuum unhooked
Astro A5 (auto next year)
3:55
PIMPxs ecu
LC2 wide band

Hi Steve, and thanks for the reply, very appreciated! I have the IAT about 8" away from the throttle body atm. I inserted it into the Anderson (rubber) 90deg elbow in order for heat soak to not be an issue. My intake air temps have never read more than 110degs parked after driving, and quickly moves down between 75-85 degs once the car has been re-started. I'll look at the ASE MAT Correction and disable it as you've suggested. I'll get a hot start data log posted soon.

Got it. Gonna be out of town till Tuesday , but I'll give that a try first thing when I get back.

Got back earlier than expected, so I had an opportunity to do a short data log of a Hot start. I adjusted the ASE 6% and the ASE Taper 10% at the CLT 180 deg and blended it in as best I thought. I actually had to do 2 hot start logs, because the first attempt was perfect, and it didn't do the lean A/F or act up at all. So, just to see if it was an anomaly I did it a second time, and this is the log I've attached.

Although it did act up and go lean on this log, it wasn't as severe as in the past prior to adjusting the ASE. So it's definitely indicating that I'm going in the right direction. Very happy about this! Attached is the Log from the 2nd Hot start attempt (with issues), also the msq at the time of the log.

Thanks again for doing this...

Hi Steve, my compression is 10.7:1 static and you're right I think my cruise (1700 RPMs) timing was low, so I bumped it up a couple of degs and utilized the smooth cells function on the timing table. I did the same in my VE table as well for the tune you sent with the small AFR/EGO Control tweeks. I loaded it up (thank you very much for doing this!) and took it for a small drive and logged.

The car feels good TBH. It idles very close to my target without oscillation, and my cruise AFR's seem to be anywhere from 14.5-15 on a level road at a steady state (the log needed to be longer to properly demonstrate this). I did a Hot start (not logged) and it was perfect this time. Definately moving in the right direction.

Your fuel table needs work, you never reach your target AFR in cruise. This will require some tweaking, I can show you how to do this and check it in a datalog if you like. Looks like a great start.
I'm not certain if I'm doing it right/efficiently or not, but what I've been doing for my WOT A/F ratio was going into my log and doing the math equation you spoke about for adjusting the A/F ratio.

Have AF/Target AF= ?? Multiply VE in desired RPM and Kpa by ??. If there's a better way I'd love to learn how, absolutely.

Short Log and Msq with AFR/EGO Control tweeks.

Thanks again....

I had a look around for some better examples of timing tables for a N/A motor somewhat close to what I'm running. I ended up adjusting my timing table again tonight. It looks better, and my cruise timing was bumped a fair bit. It's still somewhat conservative for mostly running 94 octane. I have run 91 on occasions without issue, but prefer the 94.

a91what said:

I ran out of time tonight to review your progress, but from glancing at the timing table you posted it looks like your in the right direction, I would err on the side of caution in regards to WOT timing at your comp ratio.... I would hate to see a tank of bad gas end your fun. Stock a9l ecu with 9:1 comp and 87 octane 28* total. most guys get pinging with 32* total and have to run premium fuel.

Click to expand...

No problem, I'm just very appreciative that you're even looking at it, and offering your advice and knowledge. BTW, the AF gauge seems to have become somewhat noticably more stable at idle than before. It appears the AF/EGO Control changes had a positive effect on that perhaps. Also, I'm taking your advice and backed off the WOT timing a bit.

Will do, thanks for your help.