3 bolt pt70-1 vs 4 bolt pt70

[chiken]

how much of an advantage is the four bolt compared to three bolt? i am rebuilding my motor to run in the 10's and im not sure if i am going to use the stock or terry houston headers.

 

[RUQWKNF]

Hello.
We rate the PT70-1 3 bolt turbo at roughly 785hp maxed.
We rate the PT70 four bolt at roughly 830hp maxed.
Recommended stalls are 3300 and 3400 for the PT70-1 and PT70 four bolt. 10 flat for the 3-bolt (some have gone faster) and high 9's for the four bolt. If let's say you are building the car to be legal for TSM class, then the real trick piece is the PT70-1 with the Q-trim option. This is the killer turbo for that class. Maxed out and ported stock headers would be ok, but the ultimate would be the Houston headers.
Hope some of this helps a little.

Patrick
Precision Turbo & Engine
Sales & Tech
219-996-7832

 

[Scott231]

Also note that in TSM, you have to be running a 3-bolt turbine housing.

 

[chiken]

thanks for the info guys

 

[REDS HOT AIR]

i gotta garret housing on my John Craig built 70 turbo and it seems to have real good spool and once i get to track with my new injectors we'll see how it holds it back for mph but im thinking it'll be fine

 

[TType85]

I have a John Craig LT-70 with a Precision .85 exhaust housing and with a 3500 stall 9" NL the car spools great. I think it should be good for 10's

 

[Scott231]

You may want to note that as of a few months ago, if you bought a 70-1 from Limit Engineering you got the 4" inlet/2.5" outlet compressor housing whereas the Precision piece is 4"/3"...if that matters to you.

 

[REDS HOT AIR]

mines 4" inlet 2.5" outlet which is perfect for my 2.5" i/c plumbing

 

[Nashty]

I used to run a 3-4 bolt adapter on my PT-70 till I installed ATR headers. The difference is significant in cross section. In theory, your exaust should be hitting the wheel at a lower velocity and higher pressure assuming the same flow. Because of the ATR design, this is more likely than not happening on a 4 bolt turbo. If the restriction is past the turbine inlet then the difference is less significant. That would mean more if you were using a .63 vs. a .85 housing. I doubt that you could see an actual 45 hp difference but I've never tested them. One nice flow benefit is the wastegate isn't at the turbo which is an idiotic idea that was done for packaging and cost considerations.

I've ran 131 with the 4 bolt turbo @ 25psi. It spools fine too.

 

[Louie L.]

Patrick,
Im thinking about purchasing a 70 turbo. I was informed against a "Q"trim wheel on a small motor, and that it was more for larger displacement motors and i would not realize any gains from it and a 'P "trim.

From your statement that does not appear to be the case.Can you share more info on this?

Thanks

 

[lazaris]

On the Exh side IMO it all comes down to back pressure. If you can keep it to a min which I believe is anything under 2x your inlet boost you doing ok. Wether its a larger exh housing or a larger exh wheel all of which effect different characteristics of spool and response. If your anywhere near 2-2.2 hp per cubic inch your engine is living on the exh. Just ask Judson Massingill.