Max boost on a modded IHI

[ChrisPerry]

I know that 32-34psi on a stock IHI is all before it goes boom. How about on a modded one? I ported the exhaust housing and installed an aftermarket wheel, I'm wastegated at 30-31psi now, but I get 29 at about 1/2 throttle.

Is the boost limit due to the excessive drive pressure on a stock turbo? Or is it a factor of the rpm needed to reach the higher boost levels?

I'm just wondering if I could raise the boost to 35-36psi safely or just leave it as is.

 

[OregonDMAX]

Personally I wouldn't go over 32, my modded ihi is around 30 and I'm safe and happy, 2-4 more lbs isn't going to do much tbh

 

[Chevy1925]

The issue becomes running it out of its map and chopping the throttle that may cause a surge and snap the wheel off the shaft.

That's said, I've heard of guys running 36psi out of heavily modded turbos. Those have lots of work done to the exhaust side and a 63.5 wheel.

Unless you dyno it, I wouldn't push past 32

 

[gmduramax]

The issue becomes running it out of its map and chopping the throttle that may cause a surge and snap the wheel off the shaft.

That's said, I've heard of guys running 36psi out of heavily modded turbos. Those have lots of work done to the exhaust side and a 63.5 wheel.

Unless you dyno it, I wouldn't push past 32

Keep increasing boost slowly till it blows, build another then run 1psi less than the last :woott:

Seriously though you're getting a lot more exhaust flow so even if you're only seeing 32psi it's probably making more power than before.

 

[ChrisPerry]

Thanks guys, figured that would be the answer. I'd love a few more psi as that would make me almost smoke free, but not willing to blow it up to get there.:thumb:

 

[ChrisPerry]

Keep increasing boost slowly till it blows, build another then run 1psi less than the last :woott:

Seriously though you're getting a lot more exhaust flow so even if you're only seeing 32psi it's probably making more power than before.

It's amazing how much harder it pulls now. Kinda hard to nail down what mod helped the most, but I'm happy for a minute.

 

[hondarider552]

More boost doesn't mean more power.

 

[JRein]

More boost doesn't mean more power.

This is true. For every 1 psi you increase intake charge temp by approx 14 degrees F

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[ChrisPerry]

More boost doesn't mean more power.

This is true. For every 1 psi you increase intake charge temp by approx 14 degrees F

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So stay with 30psi and add NO2 post intercooler for the added temp reduction. :woott:

 

[JRein]

So stay with 30psi and add NO2 post intercooler for the added temp reduction. :woott:

Or meth injection. Pick your poison

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[PureHybrid]

So stay with 30psi and add NO2 post intercooler for the added temp reduction. :woott:

Might want to stick with n2o

 

[Chevy1925]

This is true. For every 1 psi you increase intake charge temp by approx 14 degrees F

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Not necessarily. It depends on where you are in the map of the turbo at a given psi. The more efficient, closer you are to the least amount of heat induced into the air charge. As you fall out of the map/efficiency, temps rise rapidly more from just one more lbs of boost. It's more of a sloped induction of heat over a linear induction.

 

[NC-smokinlmm]

More boost doesn't mean more power.

Yep just heat. My 7 made more power at 26 to 28 psi so I kept it there, probably why my BMW never exploded...

 

[JRein]

Not necessarily. It depends on where you are in the map of the turbo at a given psi. The more efficient, closer you are to the least amount of heat induced into the air charge. As you fall out of the map/efficiency, temps rise rapidly more from just one more lbs of boost. It's more of a sloped induction of heat over a linear induction.

True but even if you're pulling true ambient air @ 70 degrees/14.7 baro and at 100% efficiency, you're still at 9.86 degrees induced at 1 psi.

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[Chevy1925]

True but even if you're pulling true ambient air @ 70 degrees/14.7 baro and at 100% efficiency, you're still at 9.86 degrees induced at 1 psi.

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Never said it wouldn't add heat, my point was you can't stick to a linear increase in added heat. Too many variables and changes in turbos/maps to say that. It's not just a small percentage variance either. It increases exponentially

 

[JRein]

Never said it wouldn't add heat, my point was you can't stick to a linear increase in added heat. Too many variables and changes in turbos/maps to say that. It's not just a small percentage variance either. It increases exponentially

I never said it was linear and only gave an approximation for boost only. The main variable that would change the induced heat would be the efficiency of the turbo at the given boost pressure. Otherwise only figuring at a single efficiency it does stay nearly linear.

Tout = Tin + Tin x [-1+(Pout/Pin)0.263]
efficiency

Example: the inlet temperature is 70 deg F, the suction pressure is -0.5 psig (a slight vacuum), the discharge pressure is 19 psig, and the efficiency is 72%. What is the discharge temperature?

Tin= 70 deg F + 460 = 530 deg R
Pin= -0.5 psig + 14.7 = 14.2 psia
Pout= 19 psig + 14.7 = 33.7 psia
Pout/Pin = 33.7/14.2 = 2.373 (this is the compression ratio)

Tout = 530 + [530 x (-1+2.3730.263 )]/0.72 = 717.8 deg R - 460 = 257.8 deg F= 13.57 degrees per PSI of boost

VS 1 psi at 72% efficiency being 13.7 degrees this being the reason I have the approximation I did

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[Chevy1925]

This is true. For every 1 psi you increase intake charge temp by approx 14 degrees F

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I never said it was linear and only gave an approximation for boost only. The main variable that would change the induced heat would be the efficiency of the turbo at the given boost pressure. Otherwise only figuring at a single efficiency it does stay nearly linear.

Tout = Tin + Tin x [-1+(Pout/Pin)0.263]
efficiency

Example: the inlet temperature is 70 deg F, the suction pressure is -0.5 psig (a slight vacuum), the discharge pressure is 19 psig, and the efficiency is 72%. What is the discharge temperature?

Tin= 70 deg F + 460 = 530 deg R
Pin= -0.5 psig + 14.7 = 14.2 psia
Pout= 19 psig + 14.7 = 33.7 psia
Pout/Pin = 33.7/14.2 = 2.373 (this is the compression ratio)

Tout = 530 + [530 x (-1+2.3730.263 )]/0.72 = 717.8 deg R - 460 = 257.8 deg F= 13.57 degrees per PSI of boost

VS 1 psi at 72% efficiency being 13.7 degrees this being the reason I have the approximation I did

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If you are going to post like your first post, you need to add in like you did in that last post or people will take it the wrong way. This forum is all about leading guys down the correct informational path.

I know the formulas but thank you for posting so others can understand that don't know. :thumb: