[bornloser_182]

Hey all i am trying to tune my grimmspeed 3port ebc right now and i have read that the mechanical limits of the stock evo x turbo is peak 28psi holds 25 psi then tapers to 20 psi near redline. is there a way to get the stock turbo to boost 25 psi all the way to redline? maybe change the WGA?

mods are
turbo back exhaust
no cat
intake
hardpipe
grimmspeed ebc
cobb AP

 

[hollywood_X]

All you will gain by doing that is knock and a busted turbo. Personally I have found on the stock turbo and pump gas 26psi tapering to 18-19 by 7500rpm yields the best results if you have your timing set accordingly. Anything else is pissing in the wind really.

 

[bornloser_182]

why does holding 25 psi to redline not gain significant power on pump gas? is it not possible to pull enough timing to not get knock with 25 psi at redline?

 

[joey]

Cause the stick turbo just can't do it. Search the forum. There are already many threads about this

 

[bornloser_182]

yeah i already understand the stock turbo cant do it. now im asking if holding to 25 psi doesnt help even if you could hold 25 psi to redline (ex. upgraded turbo).

 

[WraithX]

On a bigger turbo it's fine because you're hitting and holdin target boost/tq levels...regardless of
Where the turbo starts (20-25-28-30-40-50000 psi) its going to rapidly taper off as the engine consumes more air than the turbo is able to put out. Start at 25? Will taper to 18-19. Start at 28? Same thing. Start at 20? It'll be a flat TQ curve but still. Youre better off with a curve thats 25->19 than 20->19.

 

[KickAss]

yeah i already understand the stock turbo cant do it. now im asking if holding to 25 psi doesnt help even if you could hold 25 psi to redline (ex. upgraded turbo).

Holding to 25 on stock turbo can only be achieved by over-revving the turbo beyond its capacity, thus shortening its life exponentially.

Holding 25 is possible on an upgraded turbo, but you will not spool as fast as the stock turbo, even if your upgraded one was a super duper unicorn ball bearing turbo.

 

[WraithX]

Holding to 25 on stock turbo can only be achieved by over-revving the turbo beyond its capacity, thus shortening its life exponentially.

Holding 25 is possible on an upgraded turbo, but you will not spool as fast as the stock turbo, even if your upgraded one was a super duper unicorn ball bearing turbo.

Revv it high enough and the thing will fucking tear itself apart.

 

[WraithX]

Revv it high enough and the thing will fucking tear itself apart.

Psi is very different at different RPM.


Accidently self qupted instead of modifying. Damn iPhone.

 

[KickAss]

Revv it high enough and the thing will fucking tear itself apart.

Yeah, I forgot to add "and possibly killing it" at the end of my first sentence there.

 

[nkbourgeois]

On a bigger turbo it's fine because you're hitting and holdin target boost/tq levels...regardless of
Where the turbo starts (20-25-28-30-40-50000 psi) its going to rapidly taper off as the engine consumes more air than the turbo is able to put out. Start at 25? Will taper to 18-19. Start at 28? Same thing. Start at 20? It'll be a flat TQ curve but still. Youre better off with a curve thats 25->19 than 20->19.

I hold full boost (28-29psi) through 8k with no taper at all.

 

[hollywood_X]

I hold full boost (28-29psi) through 8k with no taper at all.

On a stock turbo?

 

[nkbourgeois]

no, on a bbx, but as im sure you know thats a stock housing. I think i misread wraith's comment to mean all turbos will have taper.

 

[hollywood_X]

no, on a bbx, but as im sure you know thats a stock housing. I think i misread wraith's comment to mean all turbos will have taper.

Oh I was like WTF lol
The upgraded stock frames have machined out turbine housings and much larger wheels so most can hold good boost.

OP: one thing you need to realize is PSI isn't directly proportional to power. PSI is just back pressure on the turbo forcing the air through, that why cams and larger valves allow you to make more power with less boost. It's also a good way to spot a real tuner vs some hack. Real tuners will find the spot where a turbo is moving the most air volume without adding heat to the charge and then increase timing to make the best power.

The guys who just weld the waste gate shut and drop the timing aren't making good power they are just producing numbers and knock.

 

[KickAss]

@HW, wouldn't you say that when you consider a given engine configuration, and just speaking about a turbo swap, PSI would indeed be a good measure for calculating power? The whole point becomes moot as soon as you start touching ANYTHING on the engine from Cams to displacement.

 

[hollywood_X]

@HW, wouldn't you say that when you consider a given engine configuration, and just speaking about a turbo swap, PSI would indeed be a good measure for calculating power? The whole point becomes moot as soon as you start touching ANYTHING on the engine from Cams to displacement.

You would have to be comparing nearly identical set ups to count PSI as power, and they would have to be on the same elevation with the same barometric pressure.

 

[01cbr929]

OP, you need to learn how turbos work at a deeper level to understand their limits... and what happens when you try to exceed those. It's can flow well enough to support a high boost level at a high rpm, in contrast a big snail can't make full boost of idle. Everything is a compromise. When you force the turbo to hold higher boost levels you start making a ton of heat... just blowing hot air. Just to name a few.....

 

[WraithX]

no, on a bbx, but as im sure you know thats a stock housing. I think i misread wraith's comment to mean all turbos will have taper.

Meant Stocker, sorry.