First, a link to the dyno graph.

edit: will post the img asap.

What in your opinion would be causing the break up at high rpm?

The motor is a 81, 79 carb/intake manifold, base timing, header, exhaust with mazdacomp muffler, k&n, stock porting, etc.

Thanks for any info!

 

I can't open the graph.

its a .wtdr

 

When I did my dyno day, I adjusted fuel pressure with the Puro-crap in half pound increments. It liked 4 lbs., it did not like 4.5 lbs. It did the high RPM stuttering just like you said and we cut the run at 6800RPM. It was going to 7500 RPM before... The HP difference at peak was 113 rwhp for 4.0 lbs. and 96 rwhp at 4.5 lbs.!!

 

Now Mar3, you know that it it had been a Carter Fuel Pump, you would have made like the Magic 170hp on that 12A

 

I believe that I am having a similar problem between 4-5k rpm. Seems to be too rich on the emissions dyno. Just got fuel computer, will hopefully be fixing it next week.

 

Ouch...oh, wow...I guess that's better than getting an infamous DF graphic!! Cold-blooded, maihn...

 

So you don't feel left out..

 

Ok, here's the graph.



Car also has a holley pump (red iirc, not 100% sure, I'll ask the owner) and a good fpr with an accurate gauge that doesn't sit in the car, but plugs into the line for changing fp only when needed.

 

to the top.

 

ttt any help/suggestions after seeing the graph?

 

looks like the plugs are missfiring.

this is actually the first dyno of a 12a i have ever seen.

carl.

 

Spark breakdown at high rpm is usually caused by a faulty leading ignitor.

Gosh, I sound like a broken record.

Cheers Sue

 

i'm confused the a/f ratio remains constant yet the power graph is jumpy, weird. wouldn't a missfire cause the a/f to change since there would be some unburned gases causing false readings? Dave do you have EGT's in the car?

 

I agree, the AF should be choppy as well cause of the extra oxy in the exhaust. I dunno wut caused that. Oh and one more thing. Dammit Carl!