How much boost by what RPM???

[Suprapowaz!(2)]

Throughout the years I've heard many people claiming they get "X" boost by "Y" RPM. My question is how do you know? Is there some kind of "industry standard" of test those claims? Are you supposed to roll at 1000RPM in 5th gear then floor it and see what it does? Perhaps 3rd gear from 1000RPM? Are some of these claims from looking into a datalog that was just done, or eyeballing it?

How do you guys perform and confirm this test?

 

[hvyman]

There is no set standard. All depends on the turbo, turbine housing, engine size, and boost pressure.

 

[Backlash2032]

He's asking how people get those numbers. I know I get full boost by around 2500-2700 in first gear, stock CT, but in 5th I get full boost by 2200.

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[Suprapowaz!(2)]

I understand all of those variables are going to affect a turbos spool characteristics. What I wanted to know if there was some kind of real method of performing the test. If I claim to make 12psi by 3200rpm with a T4 60trim I'm sure people would like to know how I got those numbers. In my case it would be by making a pull from 1000rpm in 5th gear, and verifying it by looking at a log.

Some people may try to look at their boost gauge and tach at the same time and verify it by that method. They also might be making a pull from 1k rpm in 3rd gear.
I just find it hard to believe some peoples claims I've heard throughout the years.

 

[Suprapowaz!(2)]

He's asking how people get those numbers. I know I get full boost by around 2500-2700 in first gear, stock CT, but in 5th I get full boost by 2200.

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This is what I'm talking about. You'll hit boost quicker in one gear vs. another. So what's a "fair" gear to make this test in?

 

[MNBmk3T]

I would think 4th would be the most fair gear to make this test in as 4th gives you a 1:1 drive ratio.

Just my .02

 

[Suprapowaz!(2)]

Yeah, that's why guys dyno in 4th. Forgot about that.

 

[DeMoN2318]

I understand all of those variables are going to affect a turbos spool characteristics. What I wanted to know if there was some kind of real method of performing the test. If I claim to make 12psi by 3200rpm with a T4 60trim I'm sure people would like to know how I got those numbers. In my case it would be by making a pull from 1000rpm in 5th gear, and verifying it by looking at a log.

Some people may try to look at their boost gauge and tach at the same time and verify it by that method. They also might be making a pull from 1k rpm in 3rd gear.
I just find it hard to believe some peoples claims I've heard throughout the years.

I idle at 13psi :naughty:


In all seriousness, I use the eyeball method in 1st

 

[IndigoMKII]

Using 1st is fine for the smaller turbos(CT, gt28 etc etc) because there is enough load to get them moving in 1st. When you get closer to 60mm wheels and such, 1st is not enough load to provide an accurate boost at RPM.

If I ever say I got X boost at Y RPM, mine is normally loaded in 3rd gear by doing a 1k roll on.

 

[super51fan]

To compare you should use 4th gear with manual and 3rd gear in auto. Same 1:1 ratio.

I guess that the auto will kick down to lower gear at wot. Unless you unplug autoecu.

 

[QWIKSTRIKE]

Using 1st is fine for the smaller turbos(CT, gt28 etc etc) because there is enough load to get them moving in 1st. When you get closer to 60mm wheels and such, 1st is not enough load to provide an accurate boost at RPM.

If I ever say I got X boost at Y RPM, mine is normally loaded in 3rd gear by doing a 1k roll on.

I have made 15lbs of boost in 1st gear with my GT4067r 272 BC cams by 4500-5000rpm's. How do I know I roll at 1000rpms and then floor it and when I hear the 15lb wast gate opne I check the RPM at that very moment. I have checked the Boost gauge when the waste gate opens and it opens at 15lbs, and its a 15lb spring in the gate. That's How I have verified this.

 

[IndigoMKII]

I'm not saying you can't build boost in first with a bigger turbo, it has to do with load on the engine.

 

[Nick M]

I would think 4th would be the most fair gear to make this test in as 4th gives you a 1:1 drive ratio.

Just my .02

Sure, as long as you exclude diff ratio. You are not one turn to engine for one turn to tire in any gear.