does boost effect turbo spool-up time?

[iceiso]

i know i posted this SOMEWHERE but i can't find it. thanks for replies!

[PWMAN]

A turbo takes longer to get to higher PSI's, so if your definition of spool time is the time it takes to achieve full pressure-then yes is the answer to your question.

[iceiso]

what about the same amount of pressure. ie...

low boost-(2 psi, 2k rpm) (4 psi, 2.5k rpm) (6 psi, 3k rpm)
high boost- (2 psi, 2k rpm) (4 psi, 2.5k rpm) (6 psi, 3k rpm) (10 psi, 3.5k rpm) (12 psi 4k rpm)

is that what it is? they take the same amount of time to boost to the same RPM but it takes longer to get to full rpm on higher boost?

[PWMAN]

Originally posted by iceiso
they take the same amount of time to boost to the same RPM but it takes longer to get to full rpm on higher boost?

They do take the same time to boost to the same RPM, but it takes longer to get to full boost if the pressure is higher- meaning at a higher RPM
Like what you said (2PSI@2K RPM, 4 [email protected] RPM etc) With only running a Wastegate set at 6 PSI it will stop providing more boost than 6 at 3K RPM (going by your chart you made) and will stay at 6 PSI even with more RPM. If set at 10 PSI it will stop at 4K RPM and not go any higher with more RPM, but it take 4K RPM to achieve 10 PSI.
I hope this makes sense to you, if not just say so.

[iceiso]

right, i think i get it. alright, so to clarify...

true/false-up until the time that low boost stops increasing, high and low boost make the same amount of boost at the same RPM. THEN, high boost keeps on increasing. so, pretty much, high boost just increases for LONGER.

[PWMAN]

Now you got it!

[iceiso]

hahaha, aight, thanks for helping me out. since it looks like you know your stuff, i'm gonna ask another question instead of starting another thread, maybe it's relevant?

why do people say that t3/t4 is useless between 6-10 psi?

[PWMAN]

Well the T3/T4 turbo is pretty big for a 4 cylinder. And 6-10 PSI is not very much boost. So you would be better off getting a smaller turbo like a T28 that will spool quicker and give you more boost at lower RPM's. Like a T28 will run out of steam at like 15 PSI, so if you want more than that you need to step up to a bigger turbine housing that will be able to pump more air. The T3/T4 is not useless, it's just not logical or necessary to use for such low boost.

[90gs]

how do the turbo #s work.. i dont get it.

t72 is huge?
t3/4 is too big for a 4 cylinder?
t28 is small?

shouldnt it follow in order?

[iceiso]

also, another kinda irrelevant question...

i'm traveling 75 @ 3000 RPM on 5th
i'm traveling 10 @ 3000 RPM on 1st

which uses more gas? does speed/gear have an effect or does only RPM?

[PWMAN]

Originally posted by 90gs
how do the turbo #s work.. i dont get it.

t72 is huge?
t3/4 is too big for a 4 cylinder?
t28 is small?

shouldnt it follow in order?

It's a different brand of turbo. When people talk T3 and T4, thats Garret turbos. It's the most popular brand. T25 is generally the smallest, T4 is the biggest turbo you want to use on a 4 cylinder. The T3/T4 is a Hybrid turbo, it uses the exhaust housing of a T3, and the compressor housing of a T4 - this way with the smaller exhaust housing it spools quicker, and with the T4 compressor it pumps more air(CFM).

T3/T4 is not to big for a 4 cylinder, it's just not justifyable to use for low boost applications because it takes longer to spool up as apposed to a T25 or T28.

[PWMAN]

Originally posted by iceiso
also, another kinda irrelevant question...

i'm traveling 75 @ 3000 RPM on 5th
i'm traveling 10 @ 3000 RPM on 1st

which uses more gas? does speed/gear have an effect or does only RPM?

I would say 75 @3000 RPM because your putting more load on the engine, and so it's going to use more gas. Gearing has somewhat of an effect, like for example: If you are going 75, your going to have to give more pedal to accelerate VS if you are in first gear going 10 MPH it requires way less pedal to accelerate-because of gearing.

[ssshhhh (_burn_)]

what everyone has to realize is that size and quality of ALL of your parts make spool up and psi different. my ball bearing 61 (equivilant) with my equal length manifold spools 10 psi before 4000. its because its ball bearing and i have the best flowing street manifold ever built. if you run a shitty manifold that effects your spool-up. what u also have to remember is that 10 psi on a t25 isnt the same as 10 psi on a y2k or a t61. take a look at some flow charts from the turbonetics webpage

[PWMAN]

Originally posted by ssshhhh (_burn_)
my ball bearing 61 (equivilant) with my equal length manifold spools 10 psi before 4000.

I was just using 4000 RPM as a number, nothing accurate about it at all. Everything you said is true but I didn't want to get into all that.

[ssshhhh (_burn_)]

Originally posted by PWMAN


I was just using 4000 RPM as a number, nothing accurate about it at all. Everything you said is true but I didn't want to get into all that.

o i know i wasnt responding directly to that. i was just using my car as a reference.