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Feedback on first ever tune for a 91 Speed Density TPI L98
I am using the EBL P4 Flash ECM with What's Up? Display for VE learns and data logging (I haven't figured out how to data log yet). I have an AEM Wideband with 0-5V data input into the ECM for VE learns and logging.
The Engine is a 355ci SBC with 10.8:1 compression and stock L98 heads milled down 0.010". Comp cams Computer Cam grind number 266HR-14 (210/220 @ 0.050" Duration, 0.500"/0.510" Lift, 114 LSA). SLP 1 3/4" shorty headers with a custom built Y-Pipe (2 1/4" to single 3") and open exhaust at the end of the Y-pipe. Hand ported Plenum but stock TPI intake other than that. I have an AFPR running 48psi and I have the base timing set to 12 deg BTDC (which it ran best on before I had a programmable ECM and was just using a cheap scanner to look at Knock counts)
Using the supplied base BIN: EBL_P4_3005.BIN I did about 6 VE learns using the WBO2 as the input device to learn. (Figured it was better than using the BLM and the NBO2)
I got some choppy VE tables that I then learned how to smooth using information on this site. (I haven't ran this new table yet)
Spark retarding seems to happen the most at around 60 MAP/2000rpm and 2200rpm and around that area. (I had the base timing in the BIN set at 6 deg BTDC even though the dist was actually set at 12 deg). I then set the Base timing in the BIN at 10 degrees BTDC (distributor still set at 12) and had almost no spark retarding.
I'll post some pics of the What's Up? readings and the VE tables from TunerPro in a second from my phone.
Just looking for feedback on what I should do different. Sometimes my AFR goes really lean at light cruise (17-19) and I'll get off the throttle and come back and it then reads 14.7-ish. Is that lean ok for a lean highway cruise? Also, my stock ECM shut off the injectors on decel when I manually downshifted my ProBuilt Stage 3 700R4 and now it doesn't I'd like to enable that feature again.
Any feedback is appreciated. For reference on my technical ability: (might matter in your depth of answers) I'm a MOPAR dealership tech for over 15 years and also taught Engine Management Systems at WyoTech for 5 years. I was a Smog tech in California as well. I'm VERY good at fixing things back to OE specs but this is my first foray into tuning. I used to just bolt stuff on and try and work around the stock tune with other methods.
Thank you. Here are some pics of my data and tables: This is the spark retarding with 6 extra deg of advance the ECM didn't know about. After pulling 4 degrees of timing Low speed VE tables before smoothing but after 6 VE learns Low speed VE tables before smoothing but after 6 VE learns High speed VE tables which didn't change much on VE learns High speed VE tables which didn't change much on VE learns Spark advance tables which i haven't touched Spark advance tables which i haven't touched Low speed VE tables after smoothing
Re: Feedback on first ever tune for a 91 Speed Density TPI L98
Originally Posted by ULTM8Z
The smaller cam builds more dynamic compression which can exacerbate knocking when you have high static compression.
Correct me if I'm wrong, but a "smaller cam" would be more Volumetrically Efficient at lower RPMs where bigger cam is losing dynamic compression due to valve overlap and intake charge going right out the exhaust but at higher RPM the big cam is more efficient at filling the cylinder and is building more dynamic compression there right?
I chose this "smaller cam" 15 years ago when I lived in California and the car had to pass a smog test on a 5 gas analyzer on a dyno. I also had a P600B Procharger with a CARB E.O. number on it that was smog legal and was under the impression that with forced induction you do not want lots of overlap because it just wastes boost as it shoots right out the exhaust valve during that overlap and you don't need the exhaust exiting the cylinder to help draw in the intake charge because the intake manifold is under pressure.
Re: Feedback on first ever tune for a 91 Speed Density TPI L98
Originally Posted by ULTM8Z
The smaller cam builds more dynamic compression which can exacerbate knocking when you have high static compression.
also, I came up with the 10.8:1 static compression due to the fact the stock heads are milled 0.010", I have 0.030" more bore being compressed into the same combustion chamber and also the Speed Pro pistons PN: L-2256F 30 are listed at +6.10cc of piston volume. The Fel-Pro head gasket i used, 7733PT2 is listed as having a compressed volume of 8.541cc. Oh whoops.... I just re ran the calculations. Its 10.05:1. That sounds correct considering the stock compression ratio is like 9.7:1. My mistake!
04-14-2022, 04:07 PM
