Help, only dynoing 300RWHP

[rhipsher]

Originally Posted by Locobob

Here is a dyno of a 91 before and after porting, no headers. If you compare this to your dyno you will note that yours is down on power over the whole rpm range - not just at the top. So whatever issue you are having is effecting the whole curve, probably not a collapsing air duct as that usually just shows up at the higher rpms.

Hum! interesting to see the difference between Locobobs dyno results and my dyno results with top end porting an my totally stock exhaust. Bobs increase shows up at about 4200rpm,s. And the increase in my dyno shows up right from the beginning all the way up. Interesting to see how different they are. I'm not sure which results are more typical. I guess it all comes down to porting technique.

[Hog]

Originally Posted by rhipsher

Hum! interesting to see the difference between Locobobs dyno results and my dyno results with top end porting an my totally stock exhaust. Bobs increase shows up at about 4200rpm,s. And the increase in my dyno shows up right from the beginning all the way up. Interesting to see how different they are. I'm not sure which results are more typical. I guess it all comes down to porting technique.

was there any ECM tuning done to your combo at all, or is it simply the porting alone that is accounting for the difference?
I see that your PE mode A/F ratio is quite different between youir pulls, it would be interesting to see Locobobs A/F ratios as well.

peace
Hog

[rhipsher]

HOG there was no tuning done at all. That was simply the result of the top end porting alone. Corey simply laid down the before porting run done 4 years earlier over the after porting run so I could see the improvement over the before porting run. Im still running stock cats and exhaust which doesn't compliment the top end port at all. Once I get the proper headers x pipe and a more free flowing exhaust system with a fantastic Corey tune I'll be curious to see what kind of numbers it will produce then. But even with stock exhaust, top end porting makes a difference either way
But back to the reason your car is only producing 300. It could be so many different things. If you haven't already, pull the codes. They will help isolate the area to focus on. Wether its a fuel problem or secondaies not working properly. O2 sensors or cats failing. Start there first.

[rhipsher]

On my AF Corey said I was running lean. I expected to be running rich if anything.

[Locobob]

Originally Posted by rhipsher

HOG there was no tuning done at all. That was simply the result of the top end porting alone. Corey simply laid down the before porting run done 4 years earlier over the after porting run so I could see the improvement over the before porting run. Im still running stock cats and exhaust which doesn't compliment the top end port at all. Once I get the proper headers x pipe and a more free flowing exhaust system with a fantastic Corey tune I'll be curious to see what kind of numbers it will produce then. But even with stock exhaust, top end porting makes a difference either way

I'm thinking the different A/F ratio's have a lot to do with the lower rpm gains, I've never seen intake porting pick up much below 4K. Porting should lean things out a bit although your A/F curve seems extreme. Hmmm 4yrs apart.... ethanol maybe?