[Dwain]

My setup and numbers are in my signature. Im trying to keep the car in the same power range but reduce lag and increase down low power. I essentially want it spool instantly. I currently have an On3 Journal Bearing 76mm with the .96ar housing. I am going to swap it out with their BB 67mm. Since I already have a .96ar housing I am thinking of ordering the 67 with the .68ar just to experiment. Im only running 6lbs of boost on the 76 so I am below the efficiency range for sure. I think it should be better with the 67. Thoughts?

 

[KEVIN$]

Change it..

ks

 

[5.0thunder]

I'm surprised your 331 isn't spooling that turbo honestly. large hot side tubing diameter? I would have thought a 65mm turbine with a .96AR would nearly choke that thing.

That said, the new turbo would definitely have a little less rotational inertia so it should spool quicker that what you have.

 

[Dwain]

The 331 spools the turbo, i just want faster spool. One thing to take into consideration is I live at 6500ft elevation so that also slows things down. I think the exhaust cross over pipe is 3 inches but it may be 2.5 inches. I honestly dont remember now. Ill have to measure it. When I look at it, it looks like its 3 inches. The charge pipe from the intercooler to the throttle body is 3.25 inch to ensure I never outgrow it and dont peg the hpx maf. The downpipe is 3.5 inches with a recirculated wastegate.

Also, im not 100% sure on the exhaust side of the turbo. The inducer on the exhaust is 74.5, the exducer is 65 on both turbos. I always go by the smallest number since that is the size of the outlet.

 

[JFraser27]

For what it’s worth, I just did what you did but with the stock 70mm turbo (.96AR) to an old version of the 67 BB turbo with a .81AR. I have a stock bottom end 5.0 with some GT40x heads and intake. What a difference that turbo made. I run a 6lb wastegate spring and the car is a blast to drive. Spools way quicker then before and pulls hard past 6k. I called On3 and they told me the exhaust housings are interchangeable between my two turbos if I felt like the .81 was running out of steam at the top end. I’d do it. He said they have ran that 67mm turbo in a 347 and it ran awesome. Spools instantly basically. If the only two options are .68 and .96 I almost would go for the .96 for your 331 and I think the BB turbo itself will make up quite a difference. You could always call them and pick their brain. The guy I talked to was very helpful to say the least.


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[pkstang]

The 331 spools the turbo, i just want faster spool. One thing to take into consideration is I live at 6500ft elevation so that also slows things down. I think the exhaust cross over pipe is 3 inches but it may be 2.5 inches. I honestly dont remember now. Ill have to measure it. When I look at it, it looks like its 3 inches. The charge pipe from the intercooler to the throttle body is 3.25 inch to ensure I never outgrow it and dont peg the hpx maf. The downpipe is 3.5 inches with a recirculated wastegate.

Also, im not 100% sure on the exhaust side of the turbo. The inducer on the exhaust is 74.5, the exducer is 65 on both turbos. I always go by the smallest number since that is the size of the outlet.

i'd strongly suggest running an EGT setup and ideally measure before and after any exhaust housing swaps

 

[boostup89]

I wouldn't change anything until you get it running on E85. Also at only 6psi on E85 I wouldn't pull any timing. Anything over 6psi I'd pull .75°per psi. Your going to be burning 30% more fuel, so your exhaust volume will increase.

I absolutely maxed out a Turbonetics 72/68 BB with a .96 turbine on a SBE 302 on E85.