• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

how much boost??

N

nyls1346

New member
i currently have a 3.0" pulley making 11psi and im thinking about going to a smaller pulley its a ported gen 3, how much boost do you think ill pick up per inch

thanks
 


How much timing?

What AFR?

mod list?

More boost might be a waste.

The traditional rule of thumb was one PSI per tenth of an inch.
 
moar heat.

efficiency in that range is 50% or less which means not only does the blower take more and more power to turn it, but it also generates more heat.
 
i am running e85 so it will react a little different than gas but im currently running 16* of timing and my original plan was to get on the dyno and dial it in and add more timing till i hit my peak torque and back it down a couple degrees

I also have a spare ls1 throttlebody and maf, i was thinking about slapping on, you think that will effect my boost level
 


When you reach a certain point in the efficiency of the blower you'll actually lose power going to a smaller pulley. Before you start losing power, you lose gains, quickly. Going from a 3.8 to a 3.4 could give you 20whp... but going from a 3.4 to a 3.0 might only give you 5-10whp, depending on your setup of course.
 
nyls1346 said:
i am running e85 so it will react a little different than gas but im currently running 16* of timing and my original plan was to get on the dyno and dial it in and add more timing till i hit my peak torque and back it down a couple degrees

I also have a spare ls1 throttlebody and maf, i was thinking about slapping on, you think that will effect my boost level
Click to expand...

while e85 is different as a fuel... it has nothing to do with the efficiency of the blower??? you will see peak performance (depending a little on flow mods) at around 12-14 psi... anything past that will be inefficient and will not net you any gains on e85 OR regular 91....

plus on e85 (and any fuel for that matter) timing>small pulley/pig rich... ESPECIALLY on e85....
 
Because ...unless he's in the Rockies.. a 3.8" pulley usually averages 8psi. Now factor in that it's winter and air is colder and denser for most of us. Call it 9psi at wot. Drop down to a 3.4" on a stock motor and you'll have plenty of restriction against flow. This creates plenty of boost backing up in the lim. Most guys see about 15psi on a 3.4 with an M90. He's talking 11psi on a 3.0 and what would he have if he went lower. Well there isn't much lower for him to go and how long can you strap a 3.0 onto a stock engine before the kaboom happens. Not tooo long. :th_winking:

Hence... I asked about mods to best understand the setup and the goal.
 


misunderstood what you were saying Bill sorry...

hes gotta be camed/heads to see that cuz Im ICd with rockers and see 12-15 (depending on the day) Im guessing
 
Add some timing, if you can get up 3-6* over stock on the current pulley and you are heading to a dyno anyway, then pulley down and run both configurations to compare at the dyno. I'm guessing you have larger injectors and at least headers if you're running a 3.0 now on ethanol...
 
i bought the car with these mods headers,cai,exhaust,3" pulley and there seems to be a mild cam in there but i dont know the specs, i measured the lift as close as possible with a dial indicator on the rocker arms

i ported the blower and opened up the lim, added 60lb injectors, and switched to e85 now
i was making about 13psi before i ported the blower and lim

btw whats your take on swapping the tb and maf, will i see much gain
 


ya not sure on the cam but yes i ported the gen3 blower and opened the lim..
like i said, before i ported the blower i was making about 13psi and now im at 11psi
and the rockers look to be stock
those lift numbers might be a little low because i measured it from the top of the valvespring retainer and i guess its possible the hydraulic lifters compressed a little when i was turning the engine over by hand
 
You must log in or register to reply here.
Back
Top