what is a race cover?

[rattlindodge]

I dont know what one is? Ive seen some turbos for sale with the race cover?

 

[Muddin_dude06]

Its a compressor housing cover that has a higher AR ratio, it essentially does the same thing a larger AR turbine housing by removing restriction so higher flow can be achieved.

 

[bbtank45]

... commonly mistaken for a velocity stack

 

[shiftycapone]

:what:

 

[VTECSTI]

... commonly mistaken for a velocity stack

velocity stack:

just to clear things up.

 

[MD-LUCKY]

Exterior difference:

Racecover on the left (s300), regular cover on the right with silencer ring (hx40 compressor housing).

 

[YOUNG GUNS15]

Good info here, bout halfway down the page it talks about different A/R setups for street or strip ect.

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html

 

[LReiff]

Exterior difference:

Racecover on the left (s300), regular cover on the right with silencer ring (hx40 compressor housing).

Then a silencer ring will make any cover a race cover? The borg cover just has it incorporated, kinda like the 6.0L powerstroke turbo cover, sure it flows more air....

 

[NickTF]

The way it reads to me is this: The larger A/R compressor housings (race covers) may not work as well at partial throttle low boost scenarios but start to shine at max throttle compressor moving out of it's map territory. I would assume it does this by extending the map of the compressor to working better at higher pressure ratios due to less restriction (what muddin said) but i'm not positive. Everything you read which is common knowledge posted on the internet says that smaller a/r is better for higher boost which is what our diesel motors like.

It seems the race covers produce more dramatic results on higher rpm lower pressure scenarios often achieved by gas motors. Again, this is all my guess on the subject.

 

[nwpadmax]

Lower A/R = favors pressure ratio, at the expense of max flow.
Higher A/R = favors flow, at the expense of pressure ratio.

Lower A/R kinda rotates the map counterclockwise around its center. Raising A/R kinda rotates it clockwise...to use a simplistic view.

As Nick said, the gassers rarely need that much pressure ratio, so big covers are the rage there on those big 101s and 106s and 114s (!). Those guys are moving hellatious amounts of air...makes our stuff look weedwacker-ish.

However with diesels it's more of a balancing act depending on how you're setting up how you want the engine to run.

Hope that makes sense.

Other things you may or may not see on a "race" cover (depending on who's philosophy you subscribe to) is the bellmouthing of the inducer bore and or deletion of the map width enhancement groove.