HPS street manners

[karolko]

How big of a difference would a HPS sized turbo be compared to a HPQ?

My goals are a 9 Second car but it needs to be completely streetable. I am using nitrous to help spool on the street and i am debating between a 70, 72 or maybe a 4276.

Thanks guys.

Adrian

 

[Eticket]

An HPQ is a 68mm Turbine wheel versus an HPS 75mm turbine wheel. The size makes a good bit difference in power and on a 70mm turbo, the HP difference is rated atA a conservative 35hp, but the spoolup is greatly affected and the HPS isn't available in a 3bolt config.

The spool up would be even more slow on the GT4276, although the power is awesome if you can use it. Even stroked 109 motors just don't have the cubic inches to use that much turbo (unless you really are shooting for 8's).

On a 109 block car, a 70GTQ/HPQ ball bearing is the way to go if you want streetability and power to run 9's.

Anything bigger and you're just playing the turbo envy game. I know you're using nitrous to spool it, but get a good converter and you won't even need the nitrous.

I like to use the rule of thumb - buy the smallest turbo you can buy that is about 50hp more than your target.

 

[Rell87]

Hmmm???? I have a Dual BB 74mm HPS I just put on my car (3400 stall)... Are you saying it won't run as good as my 70 mm I previously had on the car? I have a off center stage 1 motor. www.cardomain.com/ride/2308509

 

[Eticket]

Rell87,

Did you read what I wrote???? My comments don't say anything like that at all. All things being equal, your 74HPS (probably) will make more power than a 70mm (IF YOU TURN IT ALL THE WAY UP!)

HPS's are supposed to make more power - they should with better turbine flow. Yours is a stage motor with 4 bolt turbo right? Quite different than the 109, 3-bolt limitations.

Adrian wrote - wanting a 9 second capable car that is completely streetable.

 

[Eticket]

Nice car by the way..

 

[karolko]

Ya i have a 235" 109 block, but i am running a 4 bolt header setup so the option to run the HPS is there for me, but would it be worth it at the potential cost of streetable manners.

 

[Eticket]

Since you have a 4 bolt options.. you're going to have to decide on what you want to give up.

Both will make the power for 9's. If you don't care about "ultimate" power than I would recommend the GTQ for spool up purposes.

Other factors are if you're going ball bearing or not.. what type of stall converter you're using.. what exhaust housing to go with.. etc..

If you want "big block" type of response, then a 67 GTQ 4 bolt will even get the job done - no nitrous needed. but it won't make the MPH that a 70mm will.

The turbo selection should ultimately be made by your dealer. I have at least one to recommend, but can't do that publicly. email me for details.

 

[Rell87]

I know it will make more mph/power with the boost turned up but to tell the truth 90% of the time I'll be driving on the street running 15-16 psi on 93 octane. It's going be what it's going to be I just wanted to pick your brain and see what was your opinion about it. Do you think the 3400 stall would be fine?

 

[Rell87]

Yeah it's a stage 1 with a four bolt turbo.

 

[Eticket]

Rell87,

I really don't know to be honest. Going to the dyno or track would be the only way to tell. Someone really needs to look at a compressor map to see what it would do "in theory". I can't see that you're going to notice much difference at that boost level.

Alot depends on your CR, cubic inches, heads, cam, and ultimately tuneup.

From my limited experience - against 3-4 different stage cars I've been around, the 4 bolts do react much better on turbo size changes in that range -given that they were all big cubic inch, good flowing heads/cam combos.

I would say either way that you have enough power for anyone on the street.