383ss

iTrader: (14)

this is on my 383 stroker. dyno'd with open headers with 15" extension, short-belt and no filter, on 28" slicks with 30 lbs of air in the tires. cam is 236/232 112 lsas .602/.575 lift. RMS Stage II heads.

only bad thing is that the 78mm was taken in feburary in 54 degree weather. it was 94 today here.... the red one is 90mm,

needless to say, I am NOT happy with these results this is a drag car, no top end HP gain sucks ***. I have no idea why it gained THIRTY rwtq down low though

theblur98ss

iTrader: (71)

Hmm this is a test I've been waiting to see. What were both sets of number corrected? Was your a/f monitored on both runs? I'm curious if any tuning is needed with the 90mm setup. Did you have any numbers with an LS6 intake previous?

383ss

iTrader: (14)

yes, these were corrected numbers. previously I had done back to back dyno testing of an LS6 vs the 78mm, BUT I had 3" duals with an X-pipe then. these are the results from then.

https://ls1tech.com/forums/dynamometer-results-comparisons/142454-383ci-78mm-lsx-results.html

383ss

iTrader: (14)

oh ya... A/F ratio. with the 90mm LSX it was running a little rich at 6krpm+ about 12.8:1 finishing at about 12.5:1 at 6500. the 78mm results were a little lean at 13.8:1 straight across... don't remember why we were that high then

we did NO tuning with the 90mm. I really don't think it needs much if any either.

YsoFast

Would this mean that the heads are maxed out and not able to use any more air? (Just thinking out loud)

SScam68

iTrader: (20)

so the exhaust setups are different as well, from the 78 to 90mm?

383ss

iTrader: (14)

no, exhaust from 78 to 90 are the same.

from ls6 vs 78 both had 3" duals with X-pipe

then I went to open headers with the 78 and picked up 15tq and 10 hp

this dyno is with open headers, same setup. 78 vs 90mm

Van5150

In the old days, they had a formula that told you the max CFM you needed for carburation. Could we be at the max limit the motor needs?

Beast96Z

iTrader: (21)

Even though the number are corrected, hot weather is still going to make less power. I would also think some tuning would be neccisary when going to the larger TB. It amy not need much, but sometimes the smallest things make the biggest diffrence.

CHRISPY

I think tuning would be important and the weather (correction) could make a difference too.

I am glad to see such nice gains with the 78mm version though over the LS6.

were you running a stock ported throttle body?

383ss

iTrader: (14)

was running a 80mm BBK with the 78mm LSX and LS6

gator's 99TA

iTrader: (2)

dang this is a weird result. i really think the dynojet software can not compensate for heat and humidity like out in the midwest (or florida ) but there is probably more in the tune. i would think that with your stroker motor and heads that the motor could really use the increased capacity of the cfm.

CHRISPY

What did you dyno with the Ls6 versus 78mm FAST?


Chris

383ss

iTrader: (14)

that is in about the middle of the page... look up about 5 posts

verbs

I guarantee the weather ate up at least 10rwhp.

GrannySShifting

iTrader: (10)

are you for SURE getting the TB blade opening 90 degrees and reading 100% tps?

When they dont open all they way the more rpm you turn the more it hurts it

CHRISPY

oops just saw it thanks man

Mike K.

This alone could explain alot. Your a/f was alot different although I agree with you that the 12.5 current a/f is alot better than the 13.8,,, but this could be why you are not seeing the top end gain. You did get alot down low that so at least it wasnt a total loss. It would suck but you could always put the 78mm back on and see what it does in hot weather with the same a/f.

383ss

iTrader: (14)

well, I don't still have a 78 or access to one. I was just trying it out for a local shop... considering the A/F, it could be 10rwhp on the top end I guess. yes, I am SURE it is opening 100%. I had that problem on initial install and fixed it.

Cobraeater

What is your lid and maf and tb combo?

I mean is your lid and maf still at 75mm and what kind of 90mm tb do you have?

If your lid and maf are still 75mm and you have a 90mm tb and intake then I can see why you didn't gain anything over the 78mm lsx since you would still be flowing only 75mm of air.