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Old 01-07-2013, 08:10 PM   #1
randysubie
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Default vf 52 lbs?

how much boost can the 2.5 bottom end handle safely
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Last edited by randysubie; 01-08-2013 at 07:29 PM.
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Old 01-07-2013, 08:11 PM   #2
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All Of It
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Old 01-07-2013, 08:17 PM   #3
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Quote:
Originally Posted by randysubie View Post
how much boost can a 52 handle safely
More than you should ever care to run it at. More than your bottom end will approve of. More than would be efficient for making any power than lower boost.

No reason to go to its peak.

The question you want to ask is about your motor, not your turbo.
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Old 01-07-2013, 08:42 PM   #4
424wrx
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ive been at 22 psi for 2 years. no issues at all.
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Old 01-07-2013, 08:46 PM   #5
Slimsti
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30 all day
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Old 01-07-2013, 09:27 PM   #6
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On e85 23
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Old 01-07-2013, 09:34 PM   #7
randysubie
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Originally Posted by 424wrx View Post
ive been at 22 psi for 2 years. no issues at all.
what kind of power and mods do you have, how many miles?
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Old 01-08-2013, 05:46 PM   #8
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Quote:
Originally Posted by randysubie View Post
what kind of power and mods do you have, how many miles?
vf-52 turbo, ptp turbo blanket, tp stage 3.52 tune, grimmspeed ebcs and aos, forge motorsports bpv, perrin catted downpipe, borla catback, tomei el headers and uppipe, perrin cai, perrin tmic, rallitek swaybars, avo endlinks, racecomp/bilstein cup kit with yellow springs, racecomp lowering camber plates, cs style side skirts, jna front lip, kartboy ss, 22b shift knob, rota tarmac3 wheels and re11 tires
never been dynoed. burns no oil. 52k miles today. still on stock clutch and brake pads.
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Old 01-08-2013, 06:38 PM   #9
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lost as to the proven power......

dont they teach reading comprehension anymore?

op.....33psi, stock rods, no need for a tune, just get a fuel pressure regulator. let us know how it goes
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Old 01-08-2013, 06:56 PM   #10
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On a small turbo, the turbo regulates it's own boost to some extent. Look at the dyno databases like Cobb or EFI logics. The vf39 / 48 / 52 plots will show boost go up, then taper. On these plots peak power is usually ~16-18 psi, even if the peak boost is 20-25 psi... that's because the turbo ends up running out of flow at high RPM.

So boost only really affects midrange torque. Peak power is going to be the same at any boost level over ~18psi. Running 25 psi in the midrange is possible and even plausible if you tune for it. I know there was a rally guy who wanted max midrange and was tuned with the wastegate welded shut. Not recommended on a stock block, but doable on the right fuel with a built engine.

The max flow of a vf39/48/52 is what it is. "more boost" doesn't equal more power in this situation. Also, the turbo isn't what you need to be worried about, it's the engine.
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Old 01-08-2013, 07:02 PM   #11
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Quote:
Originally Posted by bebesito21 View Post
lost as to the proven power......

dont they teach reading comprehension anymore?

op.....33psi, stock rods, no need for a tune, just get a fuel pressure regulator. let us know how it goes

Don't forget to replace your battery, automatically helps the ecu adjust to the turbo
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Old 01-08-2013, 07:02 PM   #12
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So many replies. The second reply is the only one needed.
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Old 01-08-2013, 07:24 PM   #13
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Quote:
Originally Posted by Concillian View Post
On a small turbo, the turbo regulates it's own boost to some extent. Look at the dyno databases like Cobb or EFI logics. The vf39 / 48 / 52 plots will show boost go up, then taper. On these plots peak power is usually ~16-18 psi, even if the peak boost is 20-25 psi... that's because the turbo ends up running out of flow at high RPM.

So boost only really affects midrange torque. Peak power is going to be the same at any boost level over ~18psi. Running 25 psi in the midrange is possible and even plausible if you tune for it. I know there was a rally guy who wanted max midrange and was tuned with the wastegate welded shut. Not recommended on a stock block, but doable on the right fuel with a built engine.

The max flow of a vf39/48/52 is what it is. "more boost" doesn't equal more power in this situation. Also, the turbo isn't what you need to be worried about, it's the engine.
thanks, so what kind of power can the engine handle reliably? i was thinking of stg3-3.5 w 20-22psi and can anything be done to increase top end power without upgrading turbo
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Old 01-08-2013, 07:49 PM   #14
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Reliability decreases as power increases. Just because people get 50k miles on more power doesn't mean its still as reliable. Stock motor? Plan on a new engine if you want to play...
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Old 01-08-2013, 08:03 PM   #15
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Quote:
Originally Posted by randysubie View Post
and can anything be done to increase top end power without upgrading turbo
only pretty small gains from stuff like header, external wastegate, etc... In the end you might spend a couple thousand on 5 or 7 HP.

This is why vf dynos are funny, one shop claims 280 WHP and one shop claims 350 WHP and both are maxed out vf turbos on pump gas. People who know what's up realize that this is a difference between dynos know that there's no more than about 20 HP difference in vf setups. People who don't understand how different dynos are will drive themselves crazy chasing the 350 WHP number when their shop uses a lower reading dyno. Variation in dynos is way bigger than the variation of 20 different setups of a given engine+turbo on the same dyno.
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Old 01-08-2013, 08:06 PM   #16
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Originally Posted by Concillian View Post

only pretty small gains from stuff like header, external wastegate, etc... In the end you might spend a couple thousand on 5 or 7 HP.
That's why number hunting is stupid.

Because that 7whp is only peak where the added power under the curve and at non peak points (hey like high rpm!) will show significant gains.

You may gain 7 peak but 20whp 600 rpm higher.
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Old 01-08-2013, 11:06 PM   #17
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Quote:
Originally Posted by 424wrx View Post
ive been at 22 psi for 2 years. no issues at all.
22psi PEAK

Probably barely over 15psi by redline.

Quote:
Originally Posted by Concillian View Post
On a small turbo, the turbo regulates it's own boost to some extent. Look at the dyno databases like Cobb or EFI logics. The vf39 / 48 / 52 plots will show boost go up, then taper. On these plots peak power is usually ~16-18 psi, even if the peak boost is 20-25 psi... that's because the turbo ends up running out of flow at high RPM.

So boost only really affects midrange torque. Peak power is going to be the same at any boost level over ~18psi. Running 25 psi in the midrange is possible and even plausible if you tune for it. I know there was a rally guy who wanted max midrange and was tuned with the wastegate welded shut. Not recommended on a stock block, but doable on the right fuel with a built engine.

The max flow of a vf39/48/52 is what it is. "more boost" doesn't equal more power in this situation. Also, the turbo isn't what you need to be worried about, it's the engine.
^This.

And most of them aren't even at 18psi by redline. More like 15-16psi.

But it does depend some on what mods you have (better flow will actually have lower boost at redline).
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Old 01-09-2013, 06:58 AM   #18
424wrx
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yeah im at about 15-16 by redline. its erics map. you can only push soo much air until its equalized.
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Old 01-09-2013, 10:05 AM   #19
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Just pull the vac line off of the waste gate actuator and find out.
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Old 01-09-2013, 10:26 AM   #20
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Quote:
Originally Posted by Leafy
Just pull the vac line off of the waste gate actuator and find out.
haha! sounds harmless
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Old 01-09-2013, 07:26 PM   #21
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Quote:
Originally Posted by xluben View Post
And most of them aren't even at 18psi by redline. More like 15-16psi.
I didn't say redline, I said at "peak power"
Peak power will happen at a lower RPM than redline on a vfxx 2.5L.

So we're both correct.
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Old 01-09-2013, 08:53 PM   #22
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You probably don't want to do much more than a downpipe, up pipe, EWG, EBCS, and intercooler on a stock motor. At least if you value reliability. Or you could go beyond and just not tune to the full potential.
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Old 01-09-2013, 08:57 PM   #23
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Oof....don't even want to touch this thread with a 10ft pole.
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Old 01-09-2013, 09:20 PM   #24
424wrx
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Oof....don't even want to touch this thread with a 10ft pole.
you said pole.
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Old 01-09-2013, 10:05 PM   #25
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On pump gas, you can't make enough power to break the bottom end. You will just blow up the rest of the engine first from knock.

This is such a ridiculously vague thread where 50 answers could be given, and they'd all be correct within their own context.

Short answer is yes.

Longer answer is you're limited by the fuel type in terms of how much boost can be used. Heck, you can throw extra boost and see zero gains if the engine is flow restricted (intake, manifold, cams, heads, up pipe, down pipe, remainder of exhaust, yada yada yada). On 91 octane, you should be able to use around 21psi, give or take. At some point you just won't see more power even if you add more boost. At some point you will find yourself having to cut timing to allow more boost. Eventually you won't see any more torque nor more hp. Torque is fuel type limited. HP is flow limited.

Also, I will HIGHLY suggest you pay money now and take apart the engine and toss in forged pistons. You WILL break piston #4. It will just happen if you plan to continue modding, tuning, and playing with the car. It just happens because #4 runs more timing and is always the first to see detonation. The ringland will fail, and you will need to rebuild the engine. Maybe it's not bad. Maybe you don't need to fix the giant scratch in the block or get metal debris out of the oil. It's just easier and cheaper to be preventative. It's easier to pop pistons out than it is to tear down the whole engine.

In terms of wanting more boost, you should be looking at a couple things: E85 and a different turbo, maybe a GTX3071 or something, you know, something that's designed for high boost applications. The E85 is just cheap race gas, great knock resistance and will allow you to run a good deal more boost and push timing. +100 ft-lbs is pretty common. As long as you have a turbo and supporting engine hardware, that also translates directly to HP gains too. The downside is most folks including you very likely won't have that supporting stuff, so you'll still see mild peak HP numbers due to air flow limits but a big bump in midrange torque.
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