Choppy dyno readings.
Thread Starter
Teching In
Joined: May 2005
Posts: 11
Likes: 0
From: Acworth, GA
Choppy dyno readings. I know I don't post here much, used to post about buddy's cars but now I just got a '97 Z28 from a freind who decided he wanted a truck more than a car. It has some issues, oil leaks, barley ran when I bought it, did a tune up and has a new opti-spark. Here's the specs:
1997 Camaro Z28 LT1 w/4L60E Auto trans 105K miles.
Stock longblock/trans/converter/rear end (10-bolt 3.23 gear)
Moroso CAI
Ported+Descreened MAF
TFS Elbow
Airfoil
160* T-stat
LT4 Hotcam kit
Hooker Supercomp 1 3/4" LT headers
crappy exaust shop o/r H pipe (cut on pipe, welded the other to it)
Cutout
Flowmaster Muffler
OBD I conversion tuned by Brian at PCM4LESS
As you can say, it's choppy. It seems to have a fuel issue, the pump does not prime well at all. I have to turn the key on and off several times before cranking or it takes a long time for it to get started. If I prime it several times, it fires the way it should. I was looking at the GMS 255LPH, $125 at Summit. However, I have a 90 Mustang with a EFI Holley 255lph pump and a 190LPH, which I am converting to carb, I am wondering if I can use it.
1997 Camaro Z28 LT1 w/4L60E Auto trans 105K miles.
Stock longblock/trans/converter/rear end (10-bolt 3.23 gear)
Moroso CAI
Ported+Descreened MAF
TFS Elbow
Airfoil
160* T-stat
LT4 Hotcam kit
Hooker Supercomp 1 3/4" LT headers
crappy exaust shop o/r H pipe (cut on pipe, welded the other to it)
Cutout
Flowmaster Muffler
OBD I conversion tuned by Brian at PCM4LESS
As you can say, it's choppy. It seems to have a fuel issue, the pump does not prime well at all. I have to turn the key on and off several times before cranking or it takes a long time for it to get started. If I prime it several times, it fires the way it should. I was looking at the GMS 255LPH, $125 at Summit. However, I have a 90 Mustang with a EFI Holley 255lph pump and a 190LPH, which I am converting to carb, I am wondering if I can use it.
TECH Enthusiast
Joined: Sep 2004
Posts: 564
Likes: 0
From: Omaha, NE
A choppy graph such as that is usually caused by some tire or driveline imbalance. Usually we bring this to the attention of the vehicle owner, then smooth out the graph for more realistic average dyno readings. Most dyno software has this capability. Obviously, not smoothing the graph will cause higher then actual readings which we see posted often.
