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Discussion Starter · #1 ·
I just got new build up and running and am having trouble getting it to not fall flat on its face from 1500-3000 rpms free revving or driving.

My build is a drag only built.

It is 4.6 2v. Carbed running alcohol fuel blow thru with vortech v2. with pulley for max output.
Full built forged bottom end. PI heads. comp stage 5 cams.
1 step colder plug (tr6's)
Boost ref fuel reg.
MSD 6011 IGN. with prodata software that I use to write the timing/map curve
New MSD coils, crank, cam sensors.

I cant seem to get any kind of good crisp throttle response.
Ive tried 2 different carbs and no change.

I set initial curve at 20 degrees and started pulling 1 degree per lb of boost at 3 psi.

Ive tried more and less timing with no success.

My wideband shows going lean if I stab throttle and it falls on its face. Which I would have said would be carb issue but there was no change with different carb.

Am I missing something?
Any suggestions would be much appreciated. This is my first forced induction attempt so I may be doing something wrong.
 

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That sounds like a lean condition and not a timing problem to me. If it really falls on its face, then it's probably very lean. When I first started tuning my twin turbo car, it was not transitioning out of closed loop fueling at WOT. The car would go very lean, immediately fall on its face, then produce a very loud backfire. Your proposed timing curve sounds reasonable, and should not be the cause of the issues you're having.
 

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Discussion Starter · #3 ·
I’m glad u came up with that response! After some investigation what I believe is the culprit is my intake. It is a fuel injected intake that I converted to accept a carb. I think the fuel is puddling in the bottom of intake plenum instead of being dispersed properly... until it reaches enough boost pressure to force it into each intake runner. I’ve verified everything else is plumbed correctly and that the tune is operating correctly so I will see if the new intake I just ordered fixes the problem.
 

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Keep us posted on your progress.
 

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Discussion Starter · #6 ·
Update! After swapping over to a new intake it solved the issue complete. Upon removal of original intake we found pooling of fuel in the plenum. It's pretty eye opening to the sensitivity of everything!

It made it to the track over the weekend and did pretty decent. No full passes yet due to lean condition.
 
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