Higher boost after rebuild

[SquadXX]

Car is a 2000 with paxton, triple pump fuel system, ported heads, blah blah blah.
I recently had my engine rebuilt (because the crank snout snapped of (still trying to figure that out)) to the same specs (510cc) and now its running more boost. Prior it was running 10lbs and now its running 14-15lbs? Not to mention HP only increased by 8. Curious as to why? Nothing was done to the heads except new valve seals, etc. but no additional porting.

 

[treesnake]

Car is a 2000 with paxton, triple pump fuel system, ported heads, blah blah blah.
I recently had my engine rebuilt (because the crank snout snapped of (still trying to figure that out)) to the same specs (510cc) and now its running more boost. Prior it was running 10lbs and now its running 14-15lbs? Not to mention HP only increased by 8. Curious as to why? Nothing was done to the heads except new valve seals, etc. but no additional porting.

Do you by chance know your compression numbers in each cylinder before and after the rebuild?

Possibly your old engine had some piston blow by and your waste gate was set according to this.
I am assuming you have new pistons and rings. That combined with new valve seals would create better compression seal in each cyl..
More piston compression and old waste gate settings would create more boost ....IMO

Did you recalibrate your ECU with the new engine? How is your AFR?

 

[SquadXX]

I don't know the compression numbers before and after the rebuild but your logic makes sense to me. AFR is 11.7 and yes the car was retuned.

 

[Hostile]

Guys
CR has nothing to due with boost, boost is intake pressure and
CR is ratio of cyl. volume to combustion chamber volume.


Skeeter

 

[treesnake]

I am relating this to the exact same situation I had with my Gen 2.....

 

[SquadXX]

So i found out one of my heads had a hole in it (which i just had repaired after this higher boost situation). Could that have been leading to higher boost?

 

[speedracervr4]

Where is the hole?

 

[v10viperbox]

So i found out one of my heads had a hole in it (which i just had repaired after this higher boost situation). Could that have been leading to higher boost?

Boost is boost. More then possible that you are actually dumping 14psi into the motor but only 8 psi is actually getting to the piston everything else is going out the hole.. Weld the hole up in the head and give it another go. A 30% increase in boost should show a heck of a lot more power then 8hp

 

[dester243]

Different camshaft? Timing chain off? Just a guess.

Boost is boost, but if the valve timing is off, it can increase or decrease the amount of boost "held" in the intake manifold.

Did you change any pullies or anything? Maybe the old setup the belt was slipping and now with a new belt it's holding more boost? All weird scenerios but it doesn't explain the lack of power it's making after a rebuild. If you went with lower CR pistons that could explain the power between the different amounts of boost.

 

[v10viperbox]

Different camshaft? Timing chain off? Just a guess.

Boost is boost, but if the valve timing is off, it can increase or decrease the amount of boost "held" in the intake manifold.

Did you change any pullies or anything? Maybe the old setup the belt was slipping and now with a new belt it's holding more boost? All weird scenerios but it doesn't explain the lack of power it's making after a rebuild. If you went with lower CR pistons that could explain the power between the different amounts of boost.

Boost is boost, but you are right. What camshaft are you running and have you checked the camshaft indexing and timing. any AFR numbers