Bad tune, or engine at its limit?

[Dirtybob]

Most weather stations report corrected (to sea level equivalent) barometer. You need to uncorrect that reading or factor in for track elevation.

I would say you have good heads, unfamiliar with the superram but it's got to be better tan the stock long-tube tpi. Wouldn't suprise me if your car pulls close to 6k before laying down. My stock (iron headed) LT1 with the wimpy little cam turns 5500+, I went as high as 5750 but no improvement vs. 5500 (shift completion rpm - auto trans).

13.1:1 afr and 30 deg timing has worked well on my car (apples vs. oranges), yours may like more timing.

[90Vette]

Hmm. Well, the track was only at 70' elevation, so I can't imagine that correction would have thrown stuff off too much. But good to know for the future.

The Superram is waaay better than TPI, but it isn't meant to rev high. On a 383, everyone I've seen is shifting in the 5000-5500 range.

Did you tune that with a dyno, or have you tweaked it with trial and error at the track? I think mine could take a bit more timing, but on the street it's hard to see if changing timing or fuel helped or hurt. I'm also a bit paranoid about knock - as a newbie, I am not familiar with what it sounds like (I've watched videos, but it's not the same). I've been getting lots of knock counts at lower RPMs which I've attributed to false knock, so it's hard for me to tell if knock counts at WOT could be false knock or if it's the real deal. I don't want to risk adding in timing, datalogging a run or two, and hurting my engine from detonation.

[Dirtybob]

Did you tune that with a dyno, or have you tweaked it with trial and error at the track?

I baselined it with the butt dyno and then finished tuning at the dragstrip.
I saw more kr on the street than at the track (varying conditions vs. WOT all the time). Going from light throttle cruising in 3rd gear around 50 mph to full throttle downshift (into 2nd) will still carry a bit of kr beyond burst knock - sometimes. Was able to run timing up to 35 deg with 93 octane and no (WOT) kr, ran the same ET/mph/60' as 30 deg advance on 10% ethanol 87 octane (also kr free). Car is a daily driver so cheap gas is a bonus. Worth mentioning that w/e pos opti I have is probably not indexed correctly from the mfr. - there are some timing light discrepancies. I quit worrying about it and just tuned it for what it wants. Small amounts of kr had no effect on ET/mph/60' but I tuned it kr free to be safe. Progressively leaned out PE afr as far as 13.5:1, sweet spot appeared to be about 13.1:1.
stock 178k mile motor '95 Roadmaster, 3.42s/posi, ebay headers. 4450# as driven. 14.66 @ 92.5 - 2.045 60', 1800' DA. Needs more power (and a diet lol) plus a real (not a 12") torque converter...
http://magic-photos.com/2011/Fri%20F...s/DSC_0306.JPG

I would say if you can't hear it rattle (assuming your car isn't obnoxious loud), and the knock counts are minimal, you are at low risk to hurt anything. Have you tried higher octane to see if kr is reduced?

Edit: headers will amplify valvetrain noise - but you probably already know that...

[90Vette]

So you tune based on knock retard, not knock counts? With your current tune, around how many knock counts are you seeing in a short (say 30min) drive?

How quickly do you ramp up to your full 30°? As you can see on mine, I don't reach the full 34° until 4800 RPM, so at say 3200 I'm only at 27°.

Did you find that optimum AFR just by what was fastest at the strip? Did you play around with timing at all at the different AFRs?

My car's fairly loud, but not bad. The Corsa mufflers seem quieter than Magnaflows/Borlas/etc. It has a bit of a rattly noise at low RPM and high load, but I'm 90% sure that's just transmission noise (knock sensor doesn't pick anything up). I'd been running it on 91, but since I drove it out to the east coast I've been using 93 octane. I haven't been able to take it to the strip out here, but it seems to run the same. Looking at my datalogs, the occurrence of low-RPM knock doesn't seem to have diminished, and I was/am seeing WOT knock so infrequently it's hard to say if the 93 made any difference.

Actually, I'd forgotten that, but the low-RPM knock was there before I did the header swap.

[Dirtybob]

So you tune based on knock retard, not knock counts? With your current tune, around how many knock counts are you seeing in a short (say 30min) drive?

with the exception of sometimes seeing lingering kr after forced downshift/throttle stab, the only knock counts I see are at startup.
I am talking about following father time up the interstate on ramp and he wants to merge with 80+ mph traffic doing 45. Stabbing the gas and passing gramps will occasionally generate counts/kr. I think it's an artifact of lugging while the trans decides to downshift plus the burst knock function. I don't drive it like that much and will manually downshift to avoid lugging the motor 99% of the time.

How quickly do you ramp up to your full 30°? As you can see on mine, I don't reach the full 34° until 4800 RPM, so at say 3200 I'm only at 27°.

laptop temporarily down - IIRC it's all in b4 3k rpm.

Did you find that optimum AFR just by what was fastest at the strip? Did you play around with timing at all at the different AFRs?

actually tuning for consistency while looking to improve ETs too (and keep respectable mpg). A lot of back and forth on timing and afr in the beginning. Timing first, then afr, then back to timing - lather rinse repeat.
I bracket race the car so finding that last .05 sec. doesn't mean a whole lot to me. It's slow and I know it, FWIW I don't need this car to ever go quicker than 13.50.

My car's fairly loud, but not bad. The Corsa mufflers seem quieter than Magnaflows/Borlas/etc. It has a bit of a rattly noise at low RPM and high load, but I'm 90% sure that's just transmission noise (knock sensor doesn't pick anything up). I'd been running it on 91, but since I drove it out to the east coast I've been using 93 octane. I haven't been able to take it to the strip out here, but it seems to run the same. Looking at my datalogs, the occurrence of low-RPM knock doesn't seem to have diminished, and I was/am seeing WOT knock so infrequently it's hard to say if the 93 made any difference.

Actually, I'd forgotten that, but the low-RPM knock was there before I did the header swap.

trans or valvetrain noise, mine does the same thing. 99% sure its just valvetrain racket on mine...

[90Vette]

I am talking about following father time up the interstate on ramp and he wants to merge with 80+ mph traffic doing 45.

Hahaha that killed me.

Maybe I'll try bumping up timing leading up to my max. Although it doesn't feel like it needs timing there - torque feels pretty strong until it seems to run out of steam at around 4500.

How many runs do you do to check for knock? Do you make changes between every run? Because I'll increase timing and not have it knock until I get a single count on maybe my fourth WOT pull. It makes me kind of unsure when I can call a certain timing map safe.

Also, unrelated but have you messed with startup enrichment at all? Ever since I came out to the east coast, I've been having problems with it running really rough and surging at part throttle (especially when I first add throttle) until it warms up. Only seems to happen when it's dead cold. I'm wondering if it's related to the humidity, because I don't remember ever having this problem out in CA. Unfortunately I don't have time to hook the wideband back up, but I've been playing with startup enrichment to try to make it better.

[Dirtybob]

I tuned for knock on the worst 90+ degree, high humidity (crap air) days that I could. Street driving because it doesn't knock at the track. Maybe collect 2 hrs of data over a couple of days then check it. Variety of driving conditions, lots of flogging the car. Trying to generate worst case scenario if that makes sense.
Haven't touched startup enrichment, haven't needed to (besides the headers/home depot intake the motor is stock).

Surprising to me that you say the motor "seems to run out of steam at around 4500".

Back in 1992 I had an '87 IROC Z (305 tpi/auto/3.27 rear gear) that I swapped in a 350 crate motor originally for a 1/2 ton pickup (opportunity swap). Edelbrock headers/3" single and a 204/214 .465 hydraulic flat tappet. Bumped fuel pressure to 50 psi and used the stock 305 injectors. Had a buttload of people tell me it wouldn't work but it did. Ran 14.50s with 1.8/1.9 60's and I drove it everywhere and so did the old lady. Shifted at 5k rpm and broke the pos 7.5" rear three times, would also shred the rear trans/front torque arm mount with regularity.
Best it ever ran with the 305 was 15.9x...
paid AS&M for a "custom chip" that killed my gas mileage but did fix a slight 'hunting' issue I would see at idle. No improvement in ET/mph/60', complete waste of time & money.