Sorry this post is so long, but I wanted to be sure I included as much tech info as I could. I've been driving my 383 stroker for a few weeks now. There are 2 nagging problems with the tune that we can't seem to straighten out:

Low speed driveability (occasional stalling when slowing to a stop; when it doesn't stall, it "hunts" for idle speed...down to 500RPM, up to 1,100, down to 600RPM, up to 1,000 until it "settles" at ~950 RPM idle: also, when starting cold, it surges up & down the RPM range for about 2 minutes, before settling out to idle speed)

Running fat.....so fat, even with my shop overhead door halfway open (16' X 8' door!), after about 1 minute, your eyes start to burn and water...you can smell the raw, unburned fuel blowing out the exhaust.

We've data logged LOTS of misfires...if I remember correctly, P0300 multiple cylinder misfires (?)

The guy that's doing the tuning for me is about to go on Valium...he's trying everything he knows, and has spent HOURS and SEVERAL sessions doing his best to get good low-speed driveability.

The speed shop I'm working with (the owner assembled my engine) is very reputable, ESPECIALLY when it comes to LSX-series engines. We are having one, fundamental defference of opinion: he says the car is not running fat...it will run rich because of the lumpy cam grind, and leaning it out is not an option. I disagree. Also, since my engine was installed and running, the speed shop owner has been hearing some bad press about the type of Total Seal rings he used. They are the most expensive, top-of-the-line rings from Total Seal, and he has heard that engines fitted with these rings are suffering from excessive oil consumption....up to a quart every 400 miles, in some cases. They make a ton of power, but I'm not willing to live with that kind of oil consumption.

As far as the low speed driveability issues, I'm convinced that it has something to do with the IAC. It's either not following the throttle body butterfly correctly, or the piston is not staying open far enough when the butterfly closes, thus not allowing enough air in for smooth idle.

I know I'm leaving some power on the table running fat. I'm also sick of stinking like gasoline everytime I drive the car. Under load, and at WOT, it pulls like a freight train, and makes power light years ahead of the 346 stock engine, but I know there's more power to be had by leaning it out, and the low speed driveability is driving me nuts. Even without a dyno tune, the car should be running better. I'm afraid the guy who is doing my tuning will soon run out of options, so I'm looking for suggestions as to what we might try to get acceptable low speed driveability, and lean out the AFR. Any Ideas?

Here's what we've done:

Tuning done using HPTuners; tuning done using wideband 02, which displayed the AFR at 14.7; unplugged MAF and ran using speed density tune.

This is my set-up'02 WS6, M6)

LS1 (LS6 block) 383 stroker build components:

block torque plate plateau honed & internally balanced, hot tanked

Diamond Racing custom flat-top forged pistons; 3.905" bore

Eagle 4340 forged 4.00" stroke crank

Callies Compstar forged H-Beam (6.125") rods w/ARP 2000 rod bolts

Total Seal rings; gapless top ring, napier oil, std. oil (1.5mm x 1.5mm x 3.0mm)

Durabond coated cam bearings

Federal Mogul main bearings/Calico coated

Clevite H series rod bearings/Calico coated

ARP main/head/header studs

FAST 90mm intake

Custom billet 90mm throttle body

AFR Mongoose 225CC heads

Cometic head gaskets

Kooks stainless long tube (1-3/4" primaries) headers

Kooks ORY

Magnaflow stainless cat-back

Comp custom grind billet cam; 234*/240*, .598/.609, 112* LSA

ATI 10% underdrive harmonic balancer

FAST 36lb injectors

NGK TR55 plugs

MSD 8.5mm plug wires

SLP lid

OEM de-screened MAF

 

Sounds like a strong combo. Your setup is not too radical at all. If your VE table is close (around 14.5ish) and you got your idle tables setup correctly, you really shouldn't have any major issues.

As for the fuel smell, it comes down to: VE table not tuned right, MAF table not tuned right, not enough timing at idle, and the big one is NO CATS.

What WB 02 are you using, the dynos or one that plugs into the HP Tuners box?

Misfires are normal and need to be tuned out.

Bill

 

Your idle will be RAF material. Tune that and you are well on your way to a stable idle.

Adjust spark and fueling using bidirectional controls until you get idle lean and smooth (assuming open loop) or just adjust timing in closed loop as best as possible.
You might need to look at cracker settings, decay etc as well to help IAC down to idle rather than dropping the lid on it.

Maybe your guy is good on engines but not quite as good on the tuning?

 

I vote for a vacuum leak or a RAF issue, as ringram said.

 

We're using an Innovative wideband 02 sensor. Aside from checking the seal between the intake manifold, and the heads, where else would you check for vacuum leaks? I was told a vacuum leak would cause the engine to run fat. What should my timing be at idle?

Another wierd thing happens, too. While I still had my stock engine, I installed an SLP traction control reversal module. We tuned the T/C out, but sometimes when I start the car, the TCS light comes on, and I have to turn it off. This happened a few times while we had HPTuners running, and it showed a wheel speed sensor fault.

I like the power the cam delivers, but I've found I really have to keep the revs up in each gear, or she goes to buckin' and fartin' like a gray mule. No more letting out the clutch in traffic, and easing along smoothly in 1st gear. Assuming I get the tune correct, will the fuel stink from the ORY settle down somewhat? If not, I'm going back to a catted y-pipe.

The guy who is doing my tuning is not the same guy who wrenched my engine. He's tuned just about every car in our F-Body car club, but the vast majority of them are power-adder cars. I think this might be his 1st go at an all-engine car. He knows what he's doing, but is stymied by the idle problems (stalling occasionally during decel, and "hunting" for idle speed). Even though the AFR was reading 14.7, why does the engine run so fat? Assuming the tables are all correctly tuned, could I have a bad sensor somewhere, or would the HPTuners diagnose and display that?

Also, when idling at operating temperature, I have to use a lot of force to get the oil filler cap off. When it comes off, it makes a LOUD hiss. It's not pulling air in, but blowing it out. I checked the PCV valve, and it's working okay. Is this an abnormal condition for a high compression (11.2:1) engine?

What the heck is RAF?

Thanks for the help...I know next to nothing about tuning.

 

Sounds like the lower area (0-1200 rpms) of the VE table is way rich. For starters, I would reduce that area by 10%. This should help but is only part of the fix. It also sounds like you need to open the TB set screw a little more and reset the TPS (Throttle Position Sensor). There are several idle parameters that need adusting based on your comments, but start there and see what happens.

 

try adjusting you base running airflow its under your idle airflow tab should straighten your problem out.oh and if your in buffalo im only about 45 minutes from ya in dunkirk,mine pures like a kitten with a bigger cam than that

 

I have a 99 camaro with a 383 , auto trans and a 236 @ 600 " cam. I also had the same issues you have with the idle and stalling. My tuner and I were puzzled. The other day the car would not idle at all and was giving a maf code P102. I scanned the car and sure enough the maf was dead. I changed it out with a slp unit and it was still dead. I found a blown fuse, replaced it and the car is fixed. The old gm unit was working but must of had some kind of error with the signal it was sending to the pcm. I read that you tried sd tunning, but you shouldn't need it for your combo. Try a new maf. It worked for me. I looked for vacum leaks ,bad grounds etc. Oh by the way my ltft's went from a neg. 7-8 to a postive 3-4 with the new maf.

 

Pig rich, & hi crankcase pressure, does not bode well for ring seal.
I'd do a leakdown, and see if you have washed the rings out...

 

I was told that I was running negative crankcase pressure, and that some hi-performance guys even install vacuum pumps on their engines. I'm kind of reading between the lines here, but are you thinking that because it's running so fat, the rings "scrubbed" my cylinder hone?

The wrench who assembled my engine is insisting that we drop the engine again this winter (Oh God!), tear it down, and replace the rings with Total Seal's next step down in price rings. Even though I put the car away every winter, I am NOT looking forward to dropping the engine again.

"It also sounds like you need to open the TB set screw a little more and reset the TPS (Throttle Position Sensor). There are several idle parameters that need adusting based on your comments, but start there and see what happens"

The tuner thinks the throttle body needs to be drilled. It's a custom-built, 90mm Roberts (I believe that's the name) billet aluminum throttle body, and the tuner says that these come with whatever hole it is that needs to be drilled out, undersized. By resetting the TPS, do you mean through the HPTuners software, or should I have the upper/lower resistance measured and recalibrated?

I have been reading everything I can get my hands on about tuning. Bejabbers! The PCM takes inputs from so many sensors to decide how to "run" the engine, I don't know how you guys figure out where to even start! For instance, I've read the following things that have to do with the symptoms the engine is displaying:

THE ENGINE STALLS DURING DECELERATION

"Leave the IAC slightly open during part-throttle stages. This way, when the throttle eventually closes, the IAC piston is in position to keep the engine running. Then, have the EFI calibration cycle the IAC piston closed, then opened, to prevent the idle from surging when the throttle is closed dramatically."

THE ENGINE IDLE SURGES RANDOMLY

"This issue involves up to seven (!) different tables in the aftermarket calibration. They include the fuel,spark, IAC step, throttle follower (opening), speed of the IAC adjustment, coolant temperature, and more. Correcting this issue is what calibrating is all about."

Duh. That's the problem with tech info about tuning....they assume you know what all the techno-speak is about, and that the information makes perfect sense to you, because you've already tuned dozens of cars. I have a good, fast laptop, and I can afford just about any tuning software package out there, but I wouldn't dare try it unless someone who REALLY knew what they were doing, taught me first.

 

try adding some timing around your idle speeds and adjusting the RAF. I had the same problem on my set-up and now my car chugs along in first at 1500 rpms w/o bucking.

 

did you ever get to the bottom of it???