Having your cake and eating it as well...

[Guest]

is a 37 a twin scroll turbo?

[funkytown]

 sti8u said:

is a 37 a twin scroll turbo?

yes as is the vf36, the 34 and below are single scroll.

[Guest]

aw sweet as.thought so vf37 is off a v8 v9 correct?

[funkytown]

the vf37 is on the v8 sti, and the vf36 is on the v8 sti Spec C. Im really not sure about the v9 sorry. I would think it the same.

from above: see GC8E2DD's comments, the vf30 is on the v7 sti, and the vf34 on the v7 sti spec c. If you take the rear housing off the vf36 and put the p18 single scroll housing(off a vf30 or 34) on it you basically end up with a vf34. I.e common understanding is the compressor side, and CHRA of the vf36 and 34 are nearly identical.

[Pappu1]

 gmeago said:

Got a curve for the VF22?

Wouldn't mind seeing where the torque drops off

Pretty please

[Guest]

I don't have one of a vf22 or td05.

If someone has one for a rolling road i can do a comparision.

[Guest]

The main reason for the torque curve fallling over up top is due to the stock suby turbos not being able to hold full boost all the way to redline. Eg its pretty standard to see them hit 18psi then tail off to 14psi or less at redline.

There is a number of other factors behind this and some things can remedy it slightly, but even with almost free boosting the turbo (with link G4 boost control) they can't hold 18psi all the way to redline. as things like exhuast manifold pressure etc all effect how well a turbo holds boost.

[Guest]

I agree they like every other turbo run out of capacity in the end.

On a 2.0 litre engine 18psi @ 7000 rpm the airflow needed is something like 530cfm - and thats more than any subby VF turbo can flow.

A nice little quote

"Typically a turbo will tell you that it's getting closer to its flow limit as the discharge pressure falls. This is normally the result of the back pressure coming up and blowing the wastegate open against the force of the spring. It's a little hint, ignored at one's own peril. You can ramp the wastegate duty up to try to get the full flow from the compressor, but it is wise to do so cautiously! If it doesn't hold boost easily, it's because something's not quite right..."

[Pappu1]

thats more cfm than a vf22 lol

[funkytown]

 pappu said:

thats more cfm than a vf22 lol

which is why those than know a thing or two say dont push more than about 17-18psi through a vf turbo. They can't take it and From above "If it doesn't hold boost easily, it's because something's not quite right..."

[nt_a_foz]

 funkytown']

[quote name='pappu said:

thats more cfm than a vf22 lol

/quote]

which is why those than know a thing or two say dont push more than about 17-18psi through a vf turbo. They can't take it and From above "If it doesn't hold boost easily, it's because something's not quite right..."

but bro mine runs sick as when i crank my tap up to 25psi it boosts hard bro, screaming for the bitches... : haha

[funkytown]

 nt_a_foz']

[quote name='pappu said:

thats more cfm than a vf22 lol

/quote]

which is why those than know a thing or two say dont push more than about 17-18psi through a vf turbo. They can't take it and From above "If it doesn't hold boost easily, it's because something's not quite right..."

but bro mine runs sick as when i crank my tap up to 25psi it boosts hard bro, screaming for the bitches... : haha

haha let me qualify that with my comment referring more to single scroll turbos than the twin scroll.

eidt: whoops pushed modify not quote lol

[nt_a_foz]

 funkytown']

[quote name='pappu said:

thats more cfm than a vf22 lol

/quote]

which is why those than know a thing or two say dont push more than about 17-18psi through a vf turbo. They can't take it and From above "If it doesn't hold boost easily, it's because something's not quite right..."

but bro mine runs sick as when i crank my tap up to 25psi it boosts hard bro, screaming for the bitches... : haha

haha let me qualify that with my comment referring more to single scroll turbos than the twin scroll.

eidt: whoops pushed modify not quote lol

lol i jwas just taking the piss out of the bros that go on about how mean htere sti goes on 25psi lol

[WRXONP]

I dont want people taking my post the wrong way and im not in any way making an arguement BUT my VF23 running an external waste gate hit peak boost of 16.8 and held 16.2 to 8000 RPM. I believe the internal is what makes the boost taper back ? I may be wrong though ? And im only using a bleed valve too . Getting a EBC in the coming weeks which should work even better

[funkytown]

read this bit again WRXONP

"You can ramp the wastegate duty up to try to get the full flow from the compressor, but it is wise to do so cautiously! If it doesn't hold boost easily, it's because something's not quite right..."

you are artificially trying to keep the gate closed - so its a moot point. They don't hold that boost easily at high RPM.. fact.

i'd love to see the graphs for taking a vf23 to 8k rpm - why you would want / need to i can't fathom

[Pappu1]

 WRXONP said:

I dont want people taking my post the wrong way and im not in any way making an arguement BUT my VF23 running an external waste gate hit peak boost of 16.8 and held 16.2 to 8000 RPM. I believe the internal is what makes the boost taper back ? I may be wrong though ? And im only using a bleed valve too . Getting a EBC in the coming weeks which should work even better

yea bro saw ur graph and 16.2psi at 8000rpm is what the dyno said..

anyway, hmm who can calculate what cfm its doing at 16.2 psi at 8krpm tho?

perhaps its within vf23..lol i dunno as not sure how to calculate that figure eh.

edit:

lol who runs their stock sti at 25psi?? im sure the internal gate wud never allow that lol

i never went past 15ish at redline so not sure what psi the internal gives up... ???

[WRXONP]

Bro dont get all anal over it and have a hernia aye ? The first dyno run I had he took it to 8k . Then he asked me where I rev it too and I said 7k . . . And I run an open waste gate with a basic bleed valve . And believe me the waste gate is no where near shut ! ! Its not getting close to shutting in the higher RPM. I hate it how you guys talk to me like shit aye when im simply giving an input . . . . .

[funkytown]

not giving you s*** at all mate, so simmer some.

just pointing some of the facts and known behaviours of vf turbos, as was qwerty.

EGBP is quite high on factory subbie turbos at higher revs. What you have done is artificially got round that as such, and caution should be exercised, as per the quote.

[Guest]

 WRXONP said:

I dont want people taking my post the wrong way and im not in any way making an arguement BUT my VF23 running an external waste gate hit peak boost of 16.8 and held 16.2 to 8000 RPM. I believe the internal is what makes the boost taper back ? I may be wrong though ? And im only using a bleed valve too . Getting a EBC in the coming weeks which should work even better

my old vf22 did the same but it went upto 18psi then dropped down to 16.5 or so on the speedtech dyno... i have never seen my turbo dropped down below 14psi before this is without a boost controller...i still got my print out somewhere

is ashame i didnt get a chance to see what the vf37 get with my current mod

[Guest]

 WRXONP said:

I dont want people taking my post the wrong way and im not in any way making an arguement BUT my VF23 running an external waste gate hit peak boost of 16.8 and held 16.2 to 8000 RPM. I believe the internal is what makes the boost taper back ? I may be wrong though ? And im only using a bleed valve too . Getting a EBC in the coming weeks which should work even better

I can only read the dyno plot you posted up - and on that it is not running 16.2 psi to 8000rpm. At best its doing 15.8 @ 7000rpm.

Yes the EBC should work better.

What is happening is the exhaust gas backpressure (egbp) is so high it is blowing the wastegate open. Your external has a higher spring rate than a std vf so it takes more back pressure to open it.

A good ebc or ecu (aka link g4) can also overcome the problems of the wastegate actuator spring being over whelmed with variable wastegate duty vs rpm points.

At the end of the day you can play with higher spring rates or higher wastegate dutys only so much.

The fact when you have a high egbp opening up the wastegate tells us the turbo is starting to struggle. Its having to spin very fast indeed to supply the flow of air. To spin the turbo that fast you need a high exhaust gas differential across the turbine.

Two things are going to limit power from here on.

The compressor is running so fast its heating air so much you lose alot of the benefits of extra boost.

Running higher egbp will choke your engines volumetric efficiency and it will not make any more power no matter how high the boost is.

[WRXONP]

Aw cool thanks for the explanation . . . But u cant argue that some bloody good boost control for a bleed valve aye ha . . .

[WRXONP]

Al though maybe a little of topic . . What do you guys think of TDO5 20G ?

[Guest]

We also need to differentiate between boost and flow.

An engine that does not work too well, has poor volumetric efficiency (VE). Some setups (engine, intercooler, intake , exhaust combo) are better than others.

You can have a car that makes 200kw @ 18psi and another thats working really well makes 240kw @ 18psi

The car making 240kw is flowing a hell of a lot more air. So the turbo is working harder.

When i made the calculation of 530cfm i was using a VE rate of about 97%

If you change the VE to 80% then you only need to flow 440cfm - which most VF turbos will do.

So you can have one car the owner will say - vfxx great turbo holds say 20psi boost to the redline.

Another car thats more efficient and making more power can only do 17 psi. Same turbo.

[Guest]

 WRXONP said:

Aw cool thanks for the explanation . . . But u cant argue that some bloody good boost control for a bleed valve aye ha . . .

The result was a good one yes.

[Guest]

 WRXONP said:

Al though maybe a little of topic . . What do you guys think of TDO5 20G ?

Its a bigger turbo - higher boost threshold but will make more power if u get a good one.

Sadly there are quite a few cheap chinese copys that are not as good. So results vary.