4 bolt question

[Super6]

Figured i would try here first. what are the advantages of going to a 4 bolt turbo or disadvantages? i have stock headers and if i go with a 4 bolt turbo has anyone cut their 3 bolt flange off and put a 4 bolt on? i know of an adapter but would like to weld it on. thanks for any help................Bob

 

[RUQWKNF]

Pros are decreased back pressure, when going from a 3-bolt Buick housing to a T4 Tangential v-band style housing. If your car is setup to spool up a .85 A/R 3-bolt housing turbo with a decent sized turbine wheel (P-trim or GT-Q) and high stall converter, then switching to a T4 .68 Tangential would be a no brainer. Spool up should be maintained. However, if you had a smaller turbine wheel equipped turbo say like a TA-49 thru TE-60 with a .63 A/R 3-bolt with a 3000 stall and you stepped up to a T4 .68 Tangential, you might have some lag issues. Another pro is increased flow potential when you start trying to max out the turbo with high boost levels.

Cons are having to convert your flange on the header from 3-bolt to 4-bolt, as well as doing away with the factory style adjustable wastegate and having to go with an external wastegate mounted somewhere on the crossover pipe. T4 Tangential housings have a 3 5/8" OD v-band flange for the downpipe and have no provision for the internal flapper valve assembly.

If you have reached the limits with a 3-bolt style turbine housing, (Ex: PT76 GT-Q running at 32-35psi with a 3-bolt housing) and have verified with a back pressure gauge that your back pressure is higher than a 2:1 ratio, then switching over to a T4 Tangential style housing will significantly help relieve the back pressure. At this level, you can also upgrade the turbine wheel. In the example given, to a GT-S wheel which is worth about 100 extra fwhp. I don't recommend using a 4-bolt On Center housing. More restrictive at high hp levels than the 3-bolt style.

HTH a little.

Patrick

 

[turbo buicks]

I don't recommend using a 4-bolt On Center housing. More restrictive at high hp levels than the 3-bolt style.

oh man, i bought a 72 Q w/a on center 4 bolt exh housing. how hard/costly is it to change and will it make THAT much of a difference?

 

[RUQWKNF]

Turbine housings are priced in the $175.00 - $225.00 range. You'd have to call PTE to get current pricing. However, they do not offer a turbine housing for the older style "Q" trim wheels. Those were discontinued a long time ago. Tangentials are only available for the newer GT-Q turbine wheel. There is a very big difference between the two wheels, and you have to know which one you have before you can order a turbine housing. One housing will not work with the other. Depending on how much play/movement you have with your current downpipe, it might be as simple as cutting the round 4-bolt flange off and welding on a new v-band flange. Then simply pull the downpipe forward by about 1/4" - 1/2" and clamp it to the turbine housing. I have seen as much as 75-90 fly wheel hp gain when someone went from an On center T4 housing to a Tangential T4 V-band setup. The easiest way to see a difference would be if you had a back pressure gauge installed just before the inlet of the turbine housing and could data log or take readings. The centerline of the turbine housings' discharge on the On center vs the centerline of the turbine housings' discharge on the tangential housing is about 1/4" to 1/2", the Tangential would move the turbo forward slightly if mounted in the stock location/orientation. IMHO, it is definitely worth it. I always tried to sell a Tangential style housing vs an On Center style. On Center style housings are typically used on applications that have very little room to mount the turbo/turbos. Such as your twin turbo Mustang appilications. If you hold both up and look at the inlets on both turbine housings you can see where the exhaust on the On Center style housing has a very small area to pass through then make a very sharp wrap around bend before it hits the turbine wheel. The Tangential setup has a nice smooth and wider opening, letting the exhaust make more gentler curve around the housing before it hits the turbine wheel.
HTH

Patrick

 

[Super6]

Ruqwknf

Thanks that is what i needed....i sometimes get ahead of myself on this car but i try to buy once. thanks again....................................... Bob

 

[Hot Air]

What is the Turbonetics equivalent (3 bolt) to the Precision PT76-GT-Q?
Conrad