HOW MUCH PSI FOR 500WHP?

[basslover911]

Hey guys,

How much psi is needed for these 1uz engines to get a good 500hp (which is what the stock internals take right?).

Also, what do you need to replace in order to go higher (not that I want to, but just curious; like 700-800hp).

Thanks!

 

[91_4x4runner]

That's a fairly broad question... the amount of boost needed to generate a certain amount of power depends on tons of factors (altitude, temperature, etc).

I'm no expert, but I can say that cooler air allows for better combustion, meaning that it would take less boost to generate more power with an intercooled setup than with a non-intercooled setup, or even less boost by geographic area. At sea level it might take 15psi and at 6000 ft, it could take 20psi (again, I know next to nothing about the subject overall).

The point I'm trying to make is that there is simply no precise measurement of how much boost it takes to generate 500 horsepower. Even if you could derive a formula of what amount of boost should generate at given temperature, elevation, humidity, with given displacement, perfect AFR, etc, it'd still be different than a real-world measurement.

 

[morris]

With the VVTI it is about 15 psi intercooled, but I wouldnt try for 500rwhp with the stock engine.

 

[JBrady]

Look at a compressor map.

50 pounds per minute mass flow is right around 500hp.

Notice that 50 pounds runs from very low to very high PSI (boost)

Mass flow is just that MASS FLOW.

If you improve the flow of an engine (better ports, manifolds, cam timing, etc) you will flow more mass at any give pressure.

The 98+ VVTi engines flow more than the 90-97 engines. So, it will take more pressure on an older engine than the newer engines to make your goal.

David (Lextreme) made 325rwhp (430hp flywheel) at 8psi on his old "system". That would be 430 /(14.7 + 8) = 19hp/psi boost. So, on his old "system" you would need 12psi of boost. Of course there are other variables and this assumes nothing would be choked at the higher boost.

Now, if you take this "system" and improve the flow... you could make that 500hp at 10psi or even 8psi (or less).

 

[JustenGT8]

I'm making around 530rwhp on 17psi thru 2 K27 compressors....stock 10:1, comp ratio to give you a rough idea.

As has been said though, will depend on a swag of details right down to ignition advance so a bit of a 'how long is a piece of string' question.

 

[4000GT]

How have you done you IC pipe routing and intake Justen? I think I will go for an IC and WI instead of just WI now...

 

[JustenGT8]

temp thread hijack...sorry mate you mean "new" intake and new IC routing? If so nah still mulling over what way to go next.....trying to find a dead VVTi UZ to throw all my good bits in so at this stage just happy with 400 odd rwkw as is. Having said that though, once the engine etc is out for the clutch change who knows what'll happen

 

[JBrady]

Look at a compressor map.

50 pounds per minute mass flow is right around 500hp.

Notice that 50 pounds runs from very low to very high PSI (boost)

Mass flow is just that MASS FLOW.

If you improve the flow of an engine (better ports, manifolds, cam timing, etc) you will flow more mass at any give pressure.

The 98+ VVTi engines flow more than the 90-97 engines. So, it will take more pressure on an older engine than the newer engines to make your goal.

David (Lextreme) made 325rwhp (430hp flywheel) at 8psi on his old "system". That would be 430 /(14.7 + 8) = 19hp/psi boost. So, on his old "system" you would need 12psi of boost. Of course there are other variables and this assumes nothing would be choked at the higher boost.

Now, if you take this "system" and improve the flow... you could make that 500hp at 10psi or even 8psi (or less).

I believe this thread was originally 500hp not whp. (Title changed?) My above calcs are for 500 flywheel hp.

Using the same math would give 325/22.7=14.3whp per absolute PSI
500/14.3 = 20.3psi gauge (35psi absolute)

JustenGT8 made 530whp at only 17psi gauge (31.7psi absolute)

Of course his application is a lighter car with a manual transmission that probably is closer to 15% drivetrain loss where as the LS400 is probably low 20% range for loss (I generally use 22%). Then of course there is the question of efficiency that would favor his car as well.

 

[Boosted2.0]

It depends on a lot of things. Air temp, turbo or SC used, head flow, exhaust flow etc. If you have a fully P&P head with oversize valves and bigger cams you will make the same power at considerably lower boost than someone else with the same turbo due to the change in VE.

Not to be insulting, but this is a silly question. You either have a power goal or you don't. If you have a power goal then you size your turbo(s) or SC appropriately and you run whatever boost is required to hit your goal.