Dyno question
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,790
Likes: 0
From: Carrolton TX
Dyno question
I just Dyno'ed my car today and we noticed about a 30 HP loss\negative spike around 5.6K. Has anyone else seen this? One theory was a problem with the coil packs. One suggestion I got was to put about 4 gallons of 104 Octane and drive it hard for a few days to see if the PCM would relearn.
My car has 21K on it and only has the Vortex Ram Air and Titanium exhaust. Anyone else see similar behavior or have ideas?
Thanks.
My car has 21K on it and only has the Vortex Ram Air and Titanium exhaust. Anyone else see similar behavior or have ideas?
Thanks.
Burning Brakes
Joined: Dec 1999
Posts: 1,121
Likes: 0
From: Atlanta GA
Re: Dyno question (Superj)
Sounds like knock retard. Check your spark plugs. Also if it goes away with 104 then it's probably real knock and you might want to try the decarb process. If it doesn't go away with 104 then it's false knock. An ATAP would be helpful also.
Le Mans Master
Joined: Apr 2001
Posts: 5,331
Likes: 39
Re: Dyno question (Superj)
This was Steve Cole's response when I posted this last spring. Mine had the same dip.
"Since I'm not looking at the graphs in question I can only give you guys general information. If it's a sharp dip then tapers backup it knock retard. Sometime you will not see it on the A-tap as the scan rate is to slow on a dynojet type dyno. If you check it on the street it will show up. If the dip is more of a wave shape then it's the plugs breaking down. Try new plugs or closeing the gap in the plugs some. AFR is not the problem as the PCM integrates between points so there is no sudden changes! The little black puff as someone mentioned is almost always knock retard. ------------------Steve ColeEngineering ManagerTTS Inc. "
"Since I'm not looking at the graphs in question I can only give you guys general information. If it's a sharp dip then tapers backup it knock retard. Sometime you will not see it on the A-tap as the scan rate is to slow on a dynojet type dyno. If you check it on the street it will show up. If the dip is more of a wave shape then it's the plugs breaking down. Try new plugs or closeing the gap in the plugs some. AFR is not the problem as the PCM integrates between points so there is no sudden changes! The little black puff as someone mentioned is almost always knock retard. ------------------Steve ColeEngineering ManagerTTS Inc. "
Drifting
Joined: Oct 1999
Posts: 1,272
Likes: 0
From: Gaithersburg MD
Cruise-In II Veteran
Cruise-In III Veteran
Re: Dyno question (Gary2KC5)
This is typical of a stock LS1. Mine has it, too. As did all the other stock heads and cam LSI's that I have seen at three different dyno days.
Even GM Dyno chart on the Corvette Museum website shows this dip. This chart is shown in the Z06 comparison area. The Z06 has no dip in it.
I don't pretend to know why this is. I have Autotap'ed my car and have picked up almost no knock retard, occasionally in 3rd or 4th at WOT.
A good set of heads and a cam with a little tuning will take the dip out. :D
Even GM Dyno chart on the Corvette Museum website shows this dip. This chart is shown in the Z06 comparison area. The Z06 has no dip in it.
I don't pretend to know why this is. I have Autotap'ed my car and have picked up almost no knock retard, occasionally in 3rd or 4th at WOT.
A good set of heads and a cam with a little tuning will take the dip out. :D
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,790
Likes: 0
From: Carrolton TX
Re: Dyno question (MMarquez)
Is this an A4 or M6? Also Autotaping the car on the dyno would help. :)