Alvin

Do you ahve the dynojet runviewer files? I thought you mentioned that..

If so email them to chips@pcmforless.com

JB666

I'm saving them to my memory key tomorrow at lunch time. I'll email them to you right after that.

Thanks for any help on this issue guys - I'm just really pissed off that I dumped mega money into this, to get these results. Hopefully it's a "quick fix"

Alvin

No problem, i'm going to be out of the office from 12-4 tomarrow EST. I'll be happy to get JPG's out of the files for you and offer my advice.

JB666

Thanks again.

What I might do, is stop by on my way to work and grab the file - That way you can have them early.

DieL

check for simple things. check your throttle body cables have been adjusted properly. if not at wot the throttle may be less than fully open and that will exactly do that.. power drop above 4500 rpm.

i know cuz i had this problem when i changed a throttle body. they didnt adjust the cables and it ran awesome until high rpm when it would fall flat on its face.

gluck.

JB666

Good tip - I haven't checked it since the motor was done

Draven

Hope you get it worked out Jeff. Can't wait to run against you at NED. ; )

96dblblack

You have all the parts to make some nice power. I am sure in the next day or two with all our input plus talking to the installer and tuner, you will have a great running Vette. I can feel your pain, since the cam install on mine I am having problems with my stock lifters. I thought I might but wanted to get the cam in. So I put the cam, valve springs and new valve seals onlong with a extreme duty timing set. I now know that I should have done at least the upgraded lifters in also. Oh well live in learn and I look forward to them and the roller rockers. Keep the faith and all will work out for the best. This is just part of being a car guy.

FD2BLK

Two things I can see, You need data logs so we know what is going on duringthe pull from the ECM's point of view and we need the dyno charts to see exactly what you are describing as chopy. Alvin knws a hell of a lot more then I do but if it is chopy it is probably valve train or ingnition related not Tune. I have seen mine a bit chopy and adding a little bit of timing cleaned it right up but it was anly a small varitaation in the graph for the 5-6k range. You can down load TTS data master and run it 20 times for free if you can find a cable to log data with. I wish you the best but untill you get some data you realy are shooting a bit in the dark. One more note your A/F is not way lean and I would be a little woried if my Dyno operator made that statment to me. I un my car at 13:1 but 12.7:1 is a very good A/F ratio if you want to stay on the concervitive side of things.

tjwong

I had a customer with a 95 LT1 car with Long tubes, Comp 305 cam, Ported heads and when I first tested it, the car was a pig. He had other issues other than a tune that could even come close to fixing it. This was a few weeks ago. He came in and the car was running even worse, my TECH2 would show spark retard at even idle. Also it would backfire if the throttle was blipped, or during driving under certain conditions. I disabled the knock sensors that detonation was real. To make a long story shorter, after days of ripping my hair out. I found that the comp cam had a dowel pin that was over .750" long. I shortened it with a Dremel tool and after that the car ran fine.

I am not saying that this could be your problem. But you mentioned jagged torque and Hp curves, which is indicative of, knock retard, valve float, plugs or other ignition related issues. I have a Mustang dyno, with its software I can zoom in on the power curves and see peaks and valleys, using an ignition scope with freeze frame capabilities I can pinpoint ignition related problems by reviewing the scope and dyno curves.

Also fuel delivery can be a problem as well causing a steep dive in the power curves. I can't begin to tell you how many cars I have had on my dyne that has had fuel delivery issues. What was the WOT air fuel ratio? Was it around 13:1 or less through out the dyno pull? If it was then the fuel issue is moot.

KR can be either real or false, if its false KR and the sensor "hears" noise the PCM will retard timing. If you suspect false KR, then check for any mechanical interference. By this I mean check for anything that can be rubbing or hitting the header tubes when the engine torques over. The customer I was refering to also has Exotic Muscle headers, his passenger side tubes hit the cross member and the frame rail at a couple points. This can cause false KR any time the engine torques over enough. Also check to make sure the motor mounts are in good shape, soft motor mounts often can cause problems such as this. How tight was the knock sensor torqued down to? If it is too tight, it becomes hypersensitive. The torque for the sensor should be no more than 14 ft/lbs.

I doubt that Bryans tune can be the problem. But I can also say that when a PCM has been flashed over and over. I have had one or two where something gets corrupted in the file, and in those cases the car ran like crap. To solve the problem I would reflash the PCM with a GM file using my GM Service programming system. Then extract the file from the PCM and editing that file and reflashing the PCM again.

JB666

My AF started up around 14.1 - 14.2 and ended up (by 5500 RPMS) at 12.7, so apparently I am where I want to be?

tjwong

12.7:1 AFR is fine for WOT on a normall aspirated engine. I tune for 12.5 across the RPM range from 3500 to the test redline. Some say there is a bit more power at 13:1 which is probably true, but I feel its a bit safer at 12.5:1.

steve40th

Sounds like iginition. New Optis due break, especially if a camshaft dowel pin is wrong, like TJWONG said. Doesnt take much to ruin an Opti.

briannutter

TJ's thing about the knock sounds accurate if you're saying the curve is erratic. my STOCK engine was pulling timing w/ 92octane before I put the 160 degree thermostat in. If it's smooth up to a certain rpm then "drops off", I'd check the seat pressure. 80 lbs of pressure will nose over between 5100 and 5500. it will nose over for about 500rpm before the valve float is audible. Put those things at 120-150 lbs (stay out of coil-bind). If it fixes it,-great. if it doesn't-you would have needed to do it later to explore past 6000rpm anyway.

AGENT 86

Hope you get it solved soon Jeff

Nathan Plemons

JB666 has tried to contact me about this but I just got it this morning. Here's my $.02.

First based off of the numbers he sent me, here are the graphs.



A/F needs some work but I've certainly seen worse. Even if it was dead on though I don't believe that would fix the problem. Notice how smooth the torque curve is? Where's the 3500 RPM jump in torque that the long tube headers are supposed to give him? Where's all the upper RPM horsepower that those cylinder heads are supposed to give him?

This thing should pull like crazy until 6500 RPM's but as you can see it's done at 5250. As it is though the graph is very smooth so I don't think it's ignition related. If I was a gambling man I would say the smart money is on the cam being out of time. I know this from my own experience as well as that of GlockLT4 who had very similar issues. The car should make more power than it is making now with NO tuning if everything went right on the install.

I don't care how good a reputation the builder has, mistakes happen. I did the same thing on my car and I swore the cam was in time, I saw it with my own eyes. When I took off the timing cover though I found it a tooth off. I never dyno'd it in this condition and it did run OK. I didn't realize exactly how down on power I was until I went out to the track and could only run 102 MPH in the 14's when I had previously been 12's.

EDIT - Also note that as it sits you can't look at this A/F ratio as any kind of indiction of Alvin's ability to tune. If the cam truly is out of time it will throw everything way off. If you straighten the cam out the A/F may well fix itself.

I don't think this is actually happening here, but Alvin can attest I'm sure to the fact that many people will blame the tuner for mechanical problems. I know I can't tune out a mechanical problem, I don't know anybody who can. Unfortunately the tuner is only as good as what he has to work with.

Alvin

Actually Bryan is the one who does the tuning on those and they are especially deadly assuming the MAF is in good shape. My work is a bit harder because I specialize mostly in speeddensity. In speeddensity a set of headers before and after can serously lean the car out as much as a point...

It just means that I have 5x the library files that Bryan has to keep...

VR'92

Yeah I say cam tooth or it is possible the opti has rotated on wrong.

Redeasysport

There was a forum members car that was written up in Vette mag and had the same combo.Did somewhat like what your is doing he went with a Dynaspark and it all went away.The opti was miss firing at higher RPM's.
http://forums.corvetteforum.com/show...78&forum_id=48

pkincy

This was one of my thoughts also. However all we have to go on so far is the owner's hysteria.

We don't know any details, can't see any logs of the motor or the dyno run; so we are only scaring people by even participating in this thread to this point. Hopefully the owner will get some proper logging software and post that along with the before and after dyno runs.

Even without the logging software most Mustang dynos have a 4 gas analyzer built in that is logged with the run that would be very helpful.

I am almost thinking that the dyno itself coulda been having intermittents. Based on the only definitive information we have to date: that the car "runs great". If it runs great, I would surmise that means it is pulling past 4800 rpm. Yet the dyno run belies that fact. So we have as much chance of it being the dyno as we do the car at this point.

Perry