Scott Turvey

Don't know if this is better off here, or in the tuning forum... I will post a link there back to this one, but I'm sure the admins will chime in if I've goofed. Anyhoo...

Hey all you deep-thinkers here is an odd one I came across yesterday...

Background:
Dude drops off his '98 F-body SS to have the tune checked. Car has had engine rebuilt several months/miles (5-10K as I recall) ago and now allegedly contains upgraded crank, rods, pistons, cam and heads. Also had the PCM tuned for said upgrades. Don't worry about the exact details quite yet, just follow me for a moment.

So, I take car out for spin (figuratively speaking) and the ol' butt-o-meter says this car's anemic. No, anemic isn't quite accurate.... that would indicate there's still a pulse. This thing has throttle response like I haven't seen since the time my high school buddy tried to do a burnout in his '66 VW van but had forgotten to release the parking brake first.

Gee, I love visualizations.

Seriously, I exaggerate to make a point; this car just doesn't have any beans.

Results:
So I strap on the chassis dyno (Dynojet 224x), EFILive v5 and get a baseline. Result; ~285 RWHP (oddly, don't recall the TQ at this hour. Have to take a look at that in the morning).

So I delve into to EFILive and take a gander at the obvious things, MAF, MAP, TP, timing, O2 voltages, knock, fuel pressure, the usual. Everything looks smashing. The throttle is fully opening (visually verified as well) the MAF and MAP indicate it's pullin' air throughout the pull, the ADV and KNOCK look dandy, V's are right on track, and the fuel pressure is consistent. Hmmm, I'm sure as hell not going to doing anything worthwhile here, so I close out and do 20 or so look-see's underhood/car. Everything looks solid, no kittens or small children stuck in the belts, and the drivetrain appears to be solid and bind-free with no sign of anything goofy like dragging brake pads.

I'll give you the Reader's Digest version on the next several pulls, they're the same.

Additional Info:
Okay, now I'll expand on the engine guts as relayed to me by the owner, who has paid what sounds like a believable amount to unnamed vendor for said modifications"

Forged crank
Carillo Rods
JE Pistons
2001 Z06 cam
Stage I heads
Dyno tune.

I don't know the CR of the pistions, nor what "Stage I" heads mean in this installation. Neither does owner, he was busy working *** off to pay for this.

Car had been baselined pre-grenade at 303 HP unknown amount of time previously
(Oops, additional relevant info: builder/tuner unfortunately passed away some weeks after rebuild was completed. This obviously precludes gaining additional info from this source).

Observations:
1. Not having ready-access to source of modifications complicates things.

2. WTF? You have a powerplant that "reads" on-the-money from the diagnostic viewpoint, has been put together with "good" pieces, yet nets out worse than when the thing rolled off the line years ago.

3. This is apparently backed-up by the pre-rebuild dyno of 303 HP (pretty much in the groove for an engine of that era).

4. No apparent external issues (fuel pressure/delivery, air restrictions, or above-mentioned organic interference).

Thoughts/Opinions:
1. After noodling on this for some hours, I think the next move is going to be a compression check. This will provde insight as to the cylinder pressures being created and thusly; some guidance as to the targeted CR, or if there's something ugly afoot.

2. Additional perusing of the logs is order, perhaps there are some nuggets in there I haven't picked-up on yet.

Conclusions:
Other than it now appears I don't know everything; none yet. (Damn, looks like those comments from my family and friends that start with "Look, you pompous, arrogant know-it-all, did it ever occur to you...." might not have been just the good-natured, funny way people talk to each other Mom always told me it was. As a matter-of-fact, there might even be something to the stuff that shock-therapy lady keeps mentioning about not constantly playing with my medications.)

Seriously, any ideas or previous experiences anyone has, I would be interested in hearing (about the engine problem, you funny-guys).

I'll definitely report in on progress, thanks for reading all the way down to here.

Viper

iTrader: (6)

Leak down test as well. Make sure the valvetrain is setup right.

Camaroholic

iTrader: (1)

Compression is what I was thinking as well. Like Viper said, could be a poorly set up valvetrain.

How did the engine *sound* mechanically (not the exhaust, the engine)? Reasonable valvetrain noise, or mom's old sewing machine?

99 Black Bird T/A

iTrader: (4)

Maybe they messed up and stuck a stock LS1 back in the car.

Is that a possibility or do the tuning mods rule that out?

Mike Norris

iTrader: (10)

My first guess is the cam timing is off a tooth. We had a 2000 SS come in after a bunch of local club members did the install and came back to me for the tune. Actually made less power than pre-cam and all indicators as far as PCM readings, A/F, etc. looked good. The guys have done several installs before and this one just got past them as they found after going back into the front cover to do another cam swap thinking the cam was ground improperly.

This is easy enpough to check for sure, but do the leak and compression test like mentioned above before to be nothing is WAY off. Hope this helps.

Mike

J-Rod

The cam sounds like a good thing to check. Also, I'd look @ the 2002 Z06 cam, as by comparison when driving the two it feel like you throw out an anchor when going from a 2001 to a 2002. You probably have one laying around and its an easy gain.

Also, are there any drivetrain issues. Bad torque converter, etc... which could be reducing power?

Are there any exhaust issues (plugged cat), bad exhaust components which could be causing issues.

On things like this it can bea real annoying because you have to assume everything is wrong, and eliminate them to find the culprit. Since the motor is a "built" motor that means checking the dead guys work...

Good luck and let us know what you find...

BTW, I enjoyed the commentary.

Scott Turvey

Ahh yes. The cam timing was mentioned by one of the guys around the dyno. Forgot to make a note of that, but your post fixes that.

I'll probably get a chance to look at it tomorrow, right now it's back at the owners house (not a happy home at the moment)

Slowhawk

iTrader: (12)

I had a customer come in with a came off a tooth and did notice that the midrange was stronger but top end dropped off fast...I would geuss the Leakdown and valvetrain setup.
Had another customer come by and push 310rwhp with a Hotcam and exhaust.Within a year he found out the cylinders were shot..

FEAR THE LS1

iTrader: (1)

Any work done to the drive train... transmission.. rear end..?

Just thinking that for the car to move/dyno the engines power has to get to the ground, something could be awry motor back.

Keep us posted, this is interesting. Could be he don't have the parts installed he thinks he does.

Lee

Nine Ball

iTrader: (38)

I've seen three cases of similar happenings locally.

1. The first one was simply a bad MAF. On the tuning/diagnostics readouts, it appeared to be working, but obviously it was not reading correctly. No SES codes either. Swapped that MAF out with a screenless stock MAF and picked up about 25 rwhp. The previous MAF was old and kind of dirty on the elements.

2. The second case was plugged up catalytics. Big restriction there. The car had high mileage and the owner was probably using crappy brand gas. I could barely see any light thru a cat when we cut it off. lol

3. Third case was a poorly built engine. The piston/ring combo was slightly too large for the cylinder, which caused severe scraping on the inside of the cylinder walls. Thats alot of friction! The valve seats were poorly done, and they were not sealing properly, and the valvesprings were floating past 5500 rpm. What a mess, some people should leave engine building to the experienced shops.

You might also check the O2 sensors. Sometimes they go bad and still "act" like they are working properly in the eyes of the diagnostic scanner.

Scott Turvey

He's added a big panhard bar for autocrossing, but that's it in the drivetrain. as far as your comment about him not having the parts he thinks, me thinks that's the case also. The first thought, which I should have included in my original post, was that there is a mismatch of parts in there. We'll do the easy stuff first, then go into the motor if nothing obvious shows on the compression test.

Scott Turvey

Thanks for the ideas. let me asnwer each.

1. Bad MAF - Possibilty, we'll swap and check.
2. Plugged Cats - Nope, everything was clear there.
3. Poorly built engine - Definitley the leading candidate
4. 02 sensors - Okay here too. There actually in very good shape.

Pro Stock John

iTrader: (34)

Funny commentary, my Tahoe is pretty slow with the parking brake on.

Good list so far, I will put my list up:
-bad maf; ported goofy maf (not so rare)
-bad tps sensor (not so rare)
-bad crank sensor (rare)
-pcm in reduced power mode (check and look at timing tables)
-too much lifter preload
-cam off a tooth (can affect base timing by what 20-23 degrees?)
-heads are junk, maybe just have a teensy bit of bowl work

A stage one M6 car should hit at least 360rwhp thru headers.

Texas Terminator

cam not degreed right?

gremlin in the oil pan?

NataSS Inc

iTrader: (9)

Damn......what a mess. I vote for the gremlin.

Ragtop 99

iTrader: (7)

maybe I missed it, but did you have wideband O2 readings at WOT or are you just going by the O2 sensors? I'm curious whether you experimented with the tune by trying to lean it out and see if it picked up any power or just ended up with KR.

Was this an A4 or M6? That's real low for an A4 and miserable for an M6

Reckless

iTrader: (9)

Well the 9:1 cr motor I built for my old turbo application still dynoed in at 370 to the wheels with Stage 1 heads and a small cam through a TH350 and 12-bolt. I doubt the compression ratio is the culprit. The above suggestions look like good starting points. Have you checked the line pressure in the tranny? Could the tranny be slipping?

Scott Turvey

Nah, It's a manual.

slik98z

thats why i hang around a shop or stop by frequently if im having work done. cause if theydont do it right or put in a bad part, im gonna weld their *** crack shut. what got me started on working on a ls1in a friends garage (a 99 m6 1le) was a intake, cam and long tube install. even with out a tune, all together it was a bit rough but still had a very very nice increase over his previous set up.

sounds like the dood got dupped. tell him to tell those ****** that did the previous workon his car to suck on his bean bag, give him a good price on installing that ****, he gets his car back running how it should be, and learned his lesson about taking his car to just any shop, you make some dough and get kudos for helping build another sick ls1...everyone wins....so where do i sign up? ill be the honorary bitch slapper
~T

Scott Turvey

I agree that would be the normal route, but like I mentioned in the post, the dood that did the original work had the bad fortune of dying shortly after doing this guy's work, and there isn't really anyone for him to go after now (one-man shop). At this point, it could be the components are correct, but there was an install goof that obviously never had a chance to be remedied. The car owner hasn't really expressed any ill-will to the mechanic, just bummed he is in this state after al the $$$ and the fact it's going to take more to finish it.