Horsepower differences between S and H cover

[434nova]

Has anyone done any testing on hp differences between a S cover vs a H ? What is the larger H cover worth over a S cover on say a 700 rwhp combo.
S cover = 4 inch inlet 2.5 inch outlet
H cover = 4 inch inlet 3 inch outlet

 

[Mr.Spool]

There is power there on a buick for sure especially when the turbo is pushed real hard.

 

[forcefed3.8's]

The S cover has the same diffuser as the E cover. Only difference is inlet and outlet, no HP difference from the E to S, just looks. To get the most out of a 67mm compressor wheel and larger, you would want the H cover for sure.

 

[V6sleeper]

I've used both in a 62mm application never noticed any seat of the pants difference

 

[Mr.Spool]

Billet 64 and up with a strong combo pushing things the big cover def helps.

 

[marleyskater420]

I've seen dyno sheets of Supras making 1,198rwhp using a S cover with a 74mm compressor wheel.

Would they have gained anything by going with a 3"? I wish they would have had the opportunity to try it and see.

I think the real question should be more geared towards orifice theory flow, and how much air can a 2.5" outlet flow at the average operating temperatures of the turbo?

 

[forcefed3.8's]

I've seen dyno sheets of Supras making 1,198rwhp using a S cover with a 74mm compressor wheel.

Would they have gained anything by going with a 3"? I wish they would have had the opportunity to try it and see.

I think the real question should be more geared towards orifice theory flow, and how much air can a 2.5" outlet flow at the average operating temperatures of the turbo?

Its not the outlet size, it is the size of the diffuser.

 

[marleyskater420]

Its not the outlet size, it is the size of the diffuser.

Yes, you are right. My bad.

 

[434nova]

I always wondered why precision only makes the 6466 in a ported S cover and not offer it in a H cover? I’m running a E cover te45a now so there is no difference in size between the two? Maybe the small cover is why people say the most they can get from a 6466 is about 80lbs a min.

 

[Mr.Spool]

I've seen dyno sheets of Supras making 1,198rwhp using a S cover with a 74mm compressor wheel.

You need to understand that is a whole different animal from a 109 with a different rpm range.turbos that make power on high revving imports struggle on buick motors and rarely make the same power.

 

[marleyskater420]

You need to understand that is a whole different animal from a 109 with a different rpm range.turbos that make power on high revving imports struggle on buick motors and rarely make the same power.

Airflow is airflow.

We are talking about what the turbo itself can produce, not the engine that it is pushing air into.

At least that is how I am interpreting OP''s question ; "Do these turbos make any difference in horsepower between these two compressor covers?" instead of "On a Buick, do these two covers make any difference in power on the same turbo?" (which I still would say is a function of the turbo's output, because if one of the covers allows for more airflow, unless you have reached the dynamic limit of flow for the orifice size of the cylinder heads, you would still make more power)

 

[Mr.Spool]

instead of "On a Buick, do these two covers make any difference in power on the same turbo?" (

That's exactly what he is asking which is why he asked the question in regards of combos at or above 700rwhp.he is talking about a buick.

 

[Boost231]

I agree, thats like me going to the Honda form and asking a question about my cummins..

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[Mr.Spool]

We are talking about what the turbo itself can produce, not the engine that it is pushing air into.

We are talking about a buick 109 700 rwhp or better with a turbo.

 

[marleyskater420]

That's exactly what he is asking which is why he asked the question in regards of combos at or above 700rwhp.he is talking about a buick.

Fair enough.

I know a 2.5" outlet has supported 1000rwhp on a Buick.

Too bad we can't send some turbos to a shop to do some back to back testing on an engine.

Without any real back to back testing, how could we answer his question?

I agree, thats like me going to the Honda form and asking a question about my cummins..

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or like asking if a shop keeps custom made-to-order parts right on their shelves?

 

[Mr.Spool]

Fair enough.

I know a 2.5" outlet has supported 1000rwhp on a Buick.

Too bad we can't send some turbos to a shop to do some back to back testing on an engine.

Without any real back to back testing, how could we answer his question?



or like asking if a shop keeps custom made-to-order parts right on their shelves?

I have swapped and pushed a lot of turbos on these 109s and every time I go to the bigger cover when the car is turned up it doesn't fall off the boost cliff.now this is not for the guy that runs 20psi of boost with no timing in the motor or running 10sec passes .for most guys the smaller cover will work really good especially in the fitament area.i believe bison has tested quite a bit on the covers and I remember seeing some threads on them.

 

[Mr.Spool]

Red Armstrong also saw Rwhp gains on the bigger covers.

 

[434nova]

Yes I was hoping Bison would chime in as I read some of his post where he said he seen gains from the bigger cover.

 

[forcefed3.8's]

Red runs the original Garrett S cover. It has a larger diffuser than the current Precision S cover.

 

[Jerryl]

Has anyone done any testing on hp differences between a S cover vs a H ? What is the larger H cover worth over a S cover on say a 700 rwhp combo.
S cover = 4 inch inlet 2.5 inch outlet
H cover = 4 inch inlet 3 inch outlet

I am no expert and will share my thoughts:

I doubt there would be a difference on a 700 whp setup, especially if the cover is not the restriction.

There are lots of turbo vendors in the world, but very few can confirm performance on a Buick, with a specific combo, for a specific HP target. Anyone can say "yes/no", but . . . . . .