Question for 4 bolt turbo guys

[fastblackracing]

How much power gain could be expected on a 71 hpq dbb going from a three bolt to a 4 bolt exhaust housing...
considering the turbo to be run balls out.....not interested in gains at lower boost levels. [145+ mph]

And what impact would be had on building boost/launching with no other changes? TIA

 

[GNBRETT]

I wud say not much under a 1000 hp but I cud be wrong..... if not class racing and building a DP id go 4 bolt. I am in a couple months. back pressure mite be less tho. Bison has done testing on this in the past. he wud know best imo.

 

[Mr.Spool]

Are the headers being changed or are you running an adapter?

 

[fastblackracing]

Are the headers being changed or are you running an adapter?

I have not made up my mind.....we may just remove the 3 bolt flange and weld a four bolt on. headers only have about 500 miles on them.

 

[Mr.Spool]

I hear ya,inmo your going to need rpm for a big 4 bolt or you will be relying on the converter heavily.there are so many factors in balancing spool time and flow this thread could go 20 pagesI think it will boil down to you trying it and see if it helps your combo.the bigger turbines and ex housings combo's that I have driven needed either more displacement alot of rpm or plenty or nitrous.there are alot of 4 bolt options for sizing.

 

[fastblackracing]

I hear ya,inmo your going to need rpm for a big 4 bolt or you will be relying on the converter heavily.there are so many factors in balancing spool time and flow this thread could go 20 pagesI think it will boil down to you trying it and see if it helps your combo.the bigger turbines and ex housings combo's that I have driven needed either more displacement alot of rpm or plenty or nitrous.there are alot of 4 bolt options for sizing.

Thanks spool, l am looking into some 4 bolt turbo's and have heard that a 4 bolt housing is worth 40 HP on the same turbo over the 3 bolt....But I have no experience so I am asking.

also wondering if there is anything newer that is better than a 76 gts ?

 

[ttypewhite]

It would pick up maybe a tenth and a mph and a half. The gains would be greater if you had the S wheel on the exh side. The S wheel doesn't fit in a 3 bolt housing as it would stick out. That would be the hot ticket for you to truly maximize the 4 bolt housing. Spooling characteristics shouldn't change much if any at all with some tweaking to your program.

 

[Reggie West]

With your combo you will see some gains from it. I have a 4 bolt on my car and I like it.

I can't quantify it but I can say I have very good spool down low and no problems with backpressure at high boost levels.

I would not try to make any header changes with the displacement you are running now. Stick with what you have there.

Ask USMCTurbo6 on here how my car runs

 

[Mr.Spool]

and have heard that a 4 bolt housing is worth 40 HP on the same turbo over the 3 bolt....

hmm at the same shift points?

 

[bison]

The turbo would have to be limited by the housing to gain. Without any data there's no way to say. Looking at what we have seen now a lot can be gained in reduced drive pressure and or gains in manifold pressure by reducing intercooler restriction which would be especially important if trying to go all in with the turbo.


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[horndog]

The biggest gain is in the reduction of exhaust back pressure. You may go from 2.5:1 to 2:1 or less. if that is the case, you will make your turbo more efficient. May see up to 100HP gain if you have a shitty not efficient turbo with high exhaust backpressure. without exhaust monitors to say where your current backpressure is at is like pissing in the wind and saying it is raining outside.