3 Bolt Turbo-When Does It Become A Restriction

[SCOOBY DOO]

When does the 3 bolt turbo become a restriction?

 

[kjizzle]

Basically when the opening is too small to allow proper flow, when the backpressure exceeds a certain ratio. In practice, that's like 700+ HP with a huge turbine wheel. The stock 3-bolt is perfectly fine for the VAST majority of people.

 

[Mr.Spool]

When does the 3 bolt turbo become a restriction?

When you are making serious power.3bolt ex housings have been mid 150s in the 1/4 and 8 sec ets.even .63 are good for 9s@140mph .red a made 900rwhp with .85 3 bolt bp was 1.5 to 1

 

[forcefed3.8's]

I have gone 157mph with a .85 3 bolt @3400lbs. With a converter adjustment I am certain it will go 160. There are other considerations. If you have an intercooler with high pressure drop, you will hit a wall sooner.

 

[dank GN]

Okay just becuse ppl have done it with a 3 bolt is it better to run a 3
Bolt ? I belive you would see less back pressure with a 4 bolt which would make the turbo more efficient therefore making a 4 bolt a better choice . And of course this is for a mildly modded car .

 

[forcefed3.8's]

Okay just becuse ppl have done it with a 3 bolt is it better to run a 3
Bolt ? I belive you would see less back pressure with a 4 bolt which would make the turbo more efficient therefore making a 4 bolt a better choice . And of course this is for a mildly modded car .

Not from what I have seen on my car. When i hit the wall amd cant make anymore power with boost, then a turbo capable of making more boost will be beneficial. My 7168 was done at 28psi. If I added a turbo with a larger turbine and a compressor that is capable of efficiently making more than that, then I would see huge gains. There is probably slight gains at 28psi and under. Once the pressure ratio is close, then there will be nothing to gain. 99% arent close enough to see a gain.

 

[dank GN]

Not from what I have seen on my car. When i hit the wall amd cant make anymore power with boost, then a turbo capable of making more boost will be beneficial. My 7168 was done at 28psi. If I added a turbo with a larger turbine and a compressor that is capable of efficiently making more than that, then I would see huge gains. There is probably slight gains at 28psi and under. Once the pressure ratio is close, then there will be nothing to gain. 99% arent close enough to see a gain.

So what times where you hitting with that 7168 @ 28lbs? I have the same turbo and am actually waiting for my T4 .96A/R turbine housing to show up for these new headers I just received

 

[Mr.Spool]

Okay just becuse ppl have done it with a 3 bolt is it better to run a 3
Bolt ? I belive you would see less back pressure with a 4 bolt which would make the turbo more efficient therefore making a 4 bolt a better choice . And of course this is for a mildly modded car .

You need the right amount of bp not the lowest.there are lots of times when you can oversized the ex side and go slower

 

[dank GN]

You need the right amount of bp not the lowest.there are lots of times when you can oversized the ex side and go slower

I'm pretty sure the stage heads won't have problem seeing the Indy turbo I have and seeing how big that is lol

 

[forcefed3.8's]

So what times where you hitting with that 7168 @ 28lbs? I have the same turbo and am actually waiting for my T4 .96A/R turbine housing to show up for these new headers I just receivedView attachment 310185

I was running a precision 7168. Not the same turbo. 8.64@157. I just went 8.54@158 tonight with a 7270 3 bolt.

 

[Mr.Spool]

I was running a precision 7168. Not the same turbo. 8.64@157. I just went 8.54@158 tonight with a 7270 3 bolt.

What kind of rpm are turning?

 

[forcefed3.8's]

6100 to 6600, I need to tighten the converter and shift at 6100

 

[V6sleeper]

I was running a precision 7168. Not the same turbo. 8.64@157. I just went 8.54@158 tonight with a 7270 3 bolt.

Which slic were you running?

 

[Mr.Spool]

6100 to 6600, I need to tighten the converter and shift at 6100

I'm going to take your word on that.i thought you would be looking to spin it higher not trying to drop rpm.are you running stage motor with stage heads?or stage motor with champion heads?

 

[forcefed3.8's]

Which slic were you running?

Red Armstrong slic

 

[forcefed3.8's]

I'm going to take your word on that.i thought you would be looking to spin it higher not trying to drop rpm.are you running stage motor with stage heads?or stage motor with champion heads?

Stage block, champion heads. The 3 bolt chokes rpm with back pressure.

 

[SCOOBY DOO]

Rob, I assume you're staying with a 3 bolt to keep the car class legal?

 

[Mr.Spool]

Stage block, champion heads. The 3 bolt chokes rpm with back pressure.

Awesome.

 

[434nova]

Stage block, champion heads. The 3 bolt chokes rpm with back pressure.

Are you using R heads or regular Gn1 heads.

 

[forcefed3.8's]

I can run a 4 bolt in TSM, but the 3 bolt has become a personal challenge to hit 160mph.
I have GN1R Heads. Plenty of power left in the head. I figure with a converter adjustment, 8.4x is possible. And there is a little boost left in this turbo.