speedydog5

just wondering im at about 5-6 lb of boost on my p1sc1 and about 500 to rear with mustang dyno, if i reduce pully to gain more boost how much will i gain and how many lbs can i go to be safe i,m all stock internals just complete LT,s high flo cats with exhaust and what size pully i,m at a 4.50 now with 5-6 lbs, reason behind this whole question is i have a Shelby Cobra that is at 560 to rear wheels and is talking a lot of smack and just want to be sure i dont have a problem when we line up

PowerLabs

Those shelbies are slow as hell. Its a 4thousand pound battle tank. I've seen them get walked by bolt-ons C6s before.

C5kid

talk to Fartpipe, he had some pretty good runs w/ a GT500 putting down 800+

and he just has a bolt on C6Z, the Slowbra's are PIGS

AirBusPilot

~7% power increase per lb./boost. (Gale Banks statement).

aTX427

Probably more like 20-25rwhp per #

carlrx7

5#'s = 100 hp

PowerLabs

A little less than that since no system is 100% efficient. I bet they are geting it by converting 1 amosphere (14.7PSI) into percent (100/14.7 = 6.8%). I.E. each pound of boost puts 6.8% more air into your engine. Theoretically 1atm of boost would double the horsepower an engine makes in N/A form. In practice its a little less than that assuming no bottlenecks.

Mr.Big

What John said... most of the different LS based F.I. setups fall in this range...

speedydog5

so if i go down to a 4.0 pully from a 4.5 =5.5 psi what would that increase my boost to do you all think and would i have to have the car retuned ??

PowerLabs

Absolutely. Unless you want it to blow up.

AirBusPilot

Plus, Gale was discussing turbos.

old motorhead

Couple of q's. Does the hp per pound of boost go up/down or remain the same as boost levels go up. Would going from 5 to 10psi net you the same hp gain as say, going from 10 to 15psi (assuming timing remained the same)? What effect does a set of ported heads and blower cam have on this boost/power equation? Oh, and there's a guy on the camaro 5 forum pimping a twin turbo setup that he claims is making 795 engine hp with 8psi on a stock LS3 (just intake and exhaust upgrades). I'll save you the figgerin'.....that's about a 45hp increase per pound. Hmmmmm.

AirBusPilot

Consider these rules of thumb or averages. Efficiencies will effect that.

Your camaro friend is dreaming. He'd need twice that boost to make that. I know of some aps twin turbo gto's that made low 700's rwhp at about 16 psi or so. 8 psi will be in the low 500's rwhp.

old motorhead

He's making 581rwhp at 5psi.

AirBusPilot

How do you know this?

gtovan

Also remember, boost is a reflection of restriction. The less restriction an engine has the more it will make on a given amount of boost pressure. I recently had the heads ported on my LS9. Lost 1.25lb. of boost (same pulley before and after) but picked up 30whp.

old motorhead

He has dyno charts. If I had sense enough to provide a link, I would. Camaro5.com. Forced induction section. You can't miss it....if you're interested...

AirBusPilot

Does it show boost level?

That would be unusually high for only 5 psi., IMO. 8 psi I might believe, my experience with twins was on an ls2 (GTO). No dyno for my setup (stock but with custom cam). Through an A4 it ran in the 10's at 133 mph at 11 psi.

Ok, just went and looked.

Nice setup. According to their own numbers, that car/kit is making over 42rwhp per 1 lb. of boost at 5 psi., or about 12%/hp per lb. of boost. That's almost double the power Gale Banks stated you should expect from a good turbo kit.

GeistC6

I made 578whp @ 6.5 pounds through a stalled A6 (TTi Twins).

AirBusPilot

Any motor mods?