6152 housing????
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Unless it is specified during the time of order placement, it will be built with a .63 A/R housing.
I agree, on a stock heads and cam car, the .63 is the right choice. The .85 would be for a combination that has heads, cam and has already reached the maximum potential of the turbo when equipped with the .63 A/R housing. One thing to remember when it comes to A/R selection is that typically when going with a larger A/R ratio, there are two areas that it will either hurt or improve.
These are:
1. Will raise the power curve higher into the Rev range. This can possibly hurt a stock heads and cam equipped car, but help one that has heads and cam, and especially on a larger CI stroker.
2. Will free up back pressure when running very high boost levels. But will require a higher stall converter in order to spool up the same as the .63.
On larger CI motors, including stroker 109s and Stage IIs, you will need the larger A/R ratios in order to keep the back pressure to tollerable levels. A typical rule of thumb when it comes to back pressure is a 2:1 ratio. Once you reach this level, a change will need to be made. Ex: Readings of 60psi of back pressure measured just before the inlet of the turbine housing to 30psi of boost pressure at the intake, it would be time to change something. This could be a turbine housing A/R swap, or upgrading the entire turbo. Other changes like increasing the size of the downpipe and exhaust system will help as well. Remember, air in, air out. I always spec'd a .63 A/R housing on street driven cars, even some applications that had heads and cam on stock CI motors, unless it was a purpose built race application and the customer would have the correct torque converter.
One more secret, when it comes to the Ball Bearing equipped turbos, in some instances, you can get away with running a larger A/R ratio. Ex: TSL combos and the GT4276R turbo with the 1.28 A/R T4 inlet Garrett housing. You would think that this A/R would be too big, on the contrary, with the right converter and 274 CI to play with, spool up is incredible. Some have even run the 1.44 A/R housing with great results. This opens up a huge playing field with regards to maximum boost you can run vs back pressure on this certain combo.
Hope some of this helps.
Patrick
I agree, on a stock heads and cam car, the .63 is the right choice. The .85 would be for a combination that has heads, cam and has already reached the maximum potential of the turbo when equipped with the .63 A/R housing. One thing to remember when it comes to A/R selection is that typically when going with a larger A/R ratio, there are two areas that it will either hurt or improve.
These are:
1. Will raise the power curve higher into the Rev range. This can possibly hurt a stock heads and cam equipped car, but help one that has heads and cam, and especially on a larger CI stroker.
2. Will free up back pressure when running very high boost levels. But will require a higher stall converter in order to spool up the same as the .63.
On larger CI motors, including stroker 109s and Stage IIs, you will need the larger A/R ratios in order to keep the back pressure to tollerable levels. A typical rule of thumb when it comes to back pressure is a 2:1 ratio. Once you reach this level, a change will need to be made. Ex: Readings of 60psi of back pressure measured just before the inlet of the turbine housing to 30psi of boost pressure at the intake, it would be time to change something. This could be a turbine housing A/R swap, or upgrading the entire turbo. Other changes like increasing the size of the downpipe and exhaust system will help as well. Remember, air in, air out. I always spec'd a .63 A/R housing on street driven cars, even some applications that had heads and cam on stock CI motors, unless it was a purpose built race application and the customer would have the correct torque converter.
One more secret, when it comes to the Ball Bearing equipped turbos, in some instances, you can get away with running a larger A/R ratio. Ex: TSL combos and the GT4276R turbo with the 1.28 A/R T4 inlet Garrett housing. You would think that this A/R would be too big, on the contrary, with the right converter and 274 CI to play with, spool up is incredible. Some have even run the 1.44 A/R housing with great results. This opens up a huge playing field with regards to maximum boost you can run vs back pressure on this certain combo.
Hope some of this helps.
Patrick
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