what hp and boost with 2.93 upper

[gteatr6]

I have an 04 cobra with upr cai, mac chamber mid pipe, stock cat back, 2.93 pulley, a diablo mafia, and now custom tune. The car made 431 hp and 427 lbs tq last night. (Thankyou Bob Kurgan) But it was only making 10.8 lbs of boost and no belt slippage at all. Not to worried about the hp since I still have stock cat back, but the boost seemed awful low. Should I try a different cai? Any ideas? Thanks, Rob

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[cobraj]

My HP and TQ was a bit higher with a 2.93.

 

[rexisme]

Ya that seems low, i think mine hit around 13 or something.

 

[nytebyte]

It's the stock cat-back maybe.

My car made 420 with just a CAI and aftermarket cat-back.

 

[Bob_Kurgan]

yes, we would like some idea's on why the boost was low... it had no belt slippage and I have compared many 2.93 setups and they all seem to be about 2lbs higher...

 

[Emil]

Disconnect the stock catbacks and try it. If the boost jumps up then you know it's the exhaust, if not you got to look somewhere else. The good news is it won't cost a thing to try it!

 

[01GTvert]

I'd be willing to bet the belt is slipping a tiny bit. Replacing the belt would be a cheap/easy way to confirm this. The stock/restrictive cat back cause a higher boost #s due to stacking and maybe it is possible to lose 2psi going from 4 cats to 0.

 

[Bob_Kurgan]

I'd be willing to bet the belt is slipping a tiny bit. Replacing the belt would be a cheap/easy way to confirm this. The stock/restrictive cat back cause a higher boost #s due to stacking and maybe it is possible to lose 2psi going from 4 cats to 0.

i can tell you with 99% confidence that there is almost no belt slip.. The boost actually never drops during the run. There is no belt dust AND the belt is VERY tight to my standards..

The only thing that im questioning is that it was a "used" lightning pulley... maybe its not a 2.93 and instead a 3.1?

 

[Emil]

i can tell you with 99% confidence that there is almost no belt slip.. The boost actually never drops during the run. There is no belt dust AND the belt is VERY tight to my standards..

The only thing that im questioning is that it was a "used" lightning pulley... maybe its not a 2.93 and instead a 3.1?

That's a good guess, with my 3.1 I get about 11psi boost with 11.5-12psi in the best case when it's cold.

 

[Racerx66]

How's the clutch?

 

[Bob_Kurgan]

How's the clutch?

clutch is fine..

I dont think the power is in question here, its the boost.. If we were to make 12.5-13 psi like a 2.93 usually does, that would put the power in the 450-460 area. TYpically, on the dyno I use and IN MY EXPERIENCE, every psi of boost is good for 15rwhp and we are about 2psi short.

 

[gteatr6]

I put a new dayco poly cog belt on the car 2 days before I had Bob dyno it. It is a 74 inch belt and was pretty hard to get on compared to a used one that came with the pulley. I have a digital caliper at home. I will try to measure the pulley and see what size it is. I'll assume it should be measured at the belt grooves.