The dyno guy thinks It's the distributor. What do you think?

 

Sorry about the size.

 

That is the worst looking dyno chart I've ever seen. Something is definitely up, either with the dyno or the car.

I would think if it's running as bad as the graph suggests you would be able to tell.

 

OMG....... .....that IS an ugly chart !!!



OK.....what kind of car (year?/engine?) and what mods do you have?

KW

 

Is this the first time you've run it on a dyno? Is it a new engine build? How's the tune? Do you have any scanners/tuning software available to you?

 

If those runs were done in numerical sequence, I'd guess you came in with fouled plugs and the first 4+ runs were successful in 'blowing her clean'.
My '66 327 (10.5 cr) would run like that on leaded gas. Took 4 or 5 blasts to ~6K to clean it up; or run the old Amoco lead-free stuff. A good long highway run at 70mph (>3k rpm) would clean it up too.
My '95 Corvette drives a little like that after the wife puddles around town and then I get behind the wheel.
Let us know what you find and good luck.

 

Spark knock can make your graph look like that too, but you'd probably hear it if you were getting knock.

 

"Something is definitely up, either with the dyno or the car."
just before my car we dynoed a Friends so we know the dyno was working good.

"OK.....what kind of car (year?/engine?) and what mods do you have?"
85 388 CI, vortec heads, supper ram, headers, chip from Jesse, 6 speed,

" Is this the first time you've run it on a dyno? Is it a new engine build? How's the tune? Do you have any scanners/tuning software available to you?"
The engine is 2 years old but this is the first time on a dyno. The a/f mix looks good( I'll post it latter). No tuning equipment, my Autox ray took a crap on me."

If those runs were done in numerical sequence, I'd guess you came in with fouled plugs and the first 4+ runs were successful in 'blowing her clean'."
The timing was off for the first couple runs (the really bad looking ones) but the last 4 still look bad.

"Spark knock can make your graph look like that too, but you'd probably hear it if you were getting knock."
I would not be able to hear it but I'm sure some one there would have heard it. But that does not mean the sensor did not think it heard knock. With a scanner I would be able to look for the knock count.

The distributor is the original 23 year old 150,000 mi unit, it would not be a waste of money to replace it with a new small cap unit.
Thanks,
Dave

 

So you've been driving on this engine for 2 years now? Looking at the dyno it would be pretty easy to tell that something is wrong...how has the car behaved wen you're driving it? When you took it to the dyno did you notice anything "off"?

 

This is the A/F graph.

"So you've been driving on this engine for 2 years now? Looking at the dyno it would be pretty easy to tell that something is wrong...how has the car behaved wen you're driving it? When you took it to the dyno did you notice anything "off"? "

The car ran fine last year. This is the first I had it out this year. Over the winter I installed headers but never had it out, It's for racing only. It has a miss that's just noticeable. Hopefully this week end I can get some time to look at it. I'm thinking theres a wiring problem some were. Most likely a wire touching the headers.
Dave

 

A/F chart should hopefully bring some answers from some more knowledgeable guys. Curious to see what causes this.