While watching some skyline drag videos on US soil i've noticed that they have an extremely high pitched sound when spooled as conpaired to their Japanese counterparts. So i desided to try and figure out what changes the sound of the turbo. I'm assuming its due to the diffrent turbos the two scenes use. Typicaly japanese tuners stick to Greddy turbos which, as we all know, are old as rocks. While american tuners use newer HKS or garret units.

I've come up with two things, Anti Surge Compressor covers and Forged Billet Compressor wheels. I know that the billet wheels use thinner fins that whine like something mean, but how many garret/hks turbos use these? i'm sure not many. So my next guess are the Anti Surge covers. Dunno how it would affect the sound tho.

Anyway i know the rx7 community hasn't used as broad a range of turbos as say the supra community but i can't register over there for some reson .
So what do you guys think?

 

MM.. I switch from T04R to T04Z.

About the sounds. yes T04Z is a little louder when come to spooling. but not that loud as you heard from GTR...


I guess is depend on how fast turbo. on GTR you will see some thing like 1.5-2.0KG. On rotary mabe 1.5KG MAX.....

 

Anti-surge housings whistle.

-Max

 

From my jet engine turbine class, I learned that the sound DB and pitch are due to the difference of the still air, and the accelerating air. SO the bigger the mouth, and the surface area of the accelerated air, the louder it is, and the more concentrated the surface area of the accelerated air is, the higher the pitch. I removed my filter and installed an AIR HORN on my To4B 60-1 and it was louder than lets just say an open turbo...which wasn't much louder than with the straight pipe and Bonez intake. Any one else have anything to add?

 

my wastegate is too loud...I've never heard this whistle everyone talks about.

Also, my IC piping is as short as possible (being I have a SMIC)...does anyone think it is a good idea to run an anti-surge housing, since the shock wave has less distance to travel?

Next question: How exactly does this housing protect against compressor surge? or is it not compressor surge its protecting against?

 

None of the big turbo talkers can explain how this works? After further review I've kind of ruled out, this can in any way protect against compressor surge.

I'm assuming this protects against the surge limit on compressor maps...anyone have any ide how? Anyone care to explain that surge line on the compressor map? Is it when is outspooling itself...what's the damage?

 

Anti-surge covers just allow air to be reciculated at the compressor in the loosest and probably most poorly described way. I belive the benifit is a lower surge limit. I have read a few times and seen video's of cars with anti-surge housings and they are always much louder than a similar/same turbo w/o the anti-surge housing


-Jacob

 

Anti surge covers are designed to broaden the compressors map on the left side of the map (surge line). There are air bleeds cut into the inlet just behind the compressors inducer blades. As the turbo surges, it allows some air to escape through these small slits and they recirculate back into the inlet again. These housings do hurt overall effiency when compaired to a "standard" type compressor housings with a smooth bell mouth (like a T04S comp housing) to gain effiency near its surge line. These comp housings do make a LOT more noise (whistle sound) then a normal comp cover. Surge is wheen the turbo is pumping more air then the engine is willing to injest. Theres not too many turbo combinations that will have a turbo surging on a rotary to need these anti-surge housing. Its just a noise maker. The few combos that would need them is twin small turbos (when the turbos spool so fast they actually out flow the engines ability to inhale it all) or during part and closed throttle situations when throttling back from a high rpm/high boost load. Perhaps another situation when one is needed is maybe during a nitrous assisted trans brake luanch.

~Mike...............

 

I thought Surge was when, in light throttle applications, following full WOT, that the manifold was presurized to a point that caused the compressor to stall. In other words, the exhaust energy in these light throttle applications is not enough energy to keep the compressor spinning against the back pressure in the manifold, this causes the compressor to stall intermittently. This is the reason that a BOV can help regulate surge problems. The slits operate as you described, allowing excess manifold pressure to be vented. That is my understanding, please feel free to educate me Carl

 

My HKS 51R is very loud. It's anti surge deal that makes it noisy.

 

Carl - you are thinking of a different type of surge...that yes, BOV's eliminate.

RacerXtreme hit it on the head...although that means my compressor housing is not a true anti surge, or not the latest and greatest because there are no holes behind the blades. <--which makes sense...so WTF is up with my compressor? and true 3" inlet with a 4" filter adaptor??? if that's the case...I will have to have a word with my turbo builder

 

A lot of the time you can't even hear the turbo over the gear noise of a race transmission.

Does the high pitch whine vary directly w/ tire speed (trans) or expodentially w/ load (turbo)?

I noticed this first on a drag Silvia w/ a dogbox

 

The anti-surge housing on my SR Motorsports turbo is just like yours. No holes in it either, but it does make a crazy whistling noise when spooling.

 

Here is mine.......my holes go all the way through.

 

^yeah, I've heard that turbo in video's...pretty nasty.

I need to plumb my WG, turbo noises are more pleasant than fawking dumping exhaust gas off manifolds...imo

 

What cover choices are there for a GT35r? I think i've only seen the t04s and the non-ported "anti surge" cover.

Also i haven't seen much talk on compressor wheels. Why aren't more wheels being made from billet aluminum? I mean considering how many CNC shops are popping up you'd think there would be more then that one turbo the supra shops are offering.

 

Actually if you look closely you'll see the cuts in the housing between inner and outer blades.

Some Supra guys have actually made an adapter to cover/disable the anti surge opening and picked up ~30-40rwh in a 800-900rwh set up......

 

I believe the way HKS did the anti-surge on the T04Z housing was to improved the flow but still have the benefits of anti-surge.

 

The way I have seen them on the GT turbos is like a velocity stack pressed in that connects the inner and outer rings of the anti surge housing with a gap right in front of the compressor for the anti-surge flow.

 

Yes we have and picked up a "little" more hp than that. That is a typical # but have seen as high as 50-60 rwhp and a 300-500 rpm spool gain. We've actually done a twin turbo chevy with GT47's and picked up over 150rwhp......but he was already in the 2300 hp range. He picked up a considerable amount in spool as well. He's a big racer in the PSCA crowd so as you can guess we've gotten alot of business just from his car. People were rather shocked to find out you could pick up so much power without major work.

 

So who can make such a things for my GT40r? I get 20psi by 4300rpm in 3rd gear. My Racelogic could use more of a work out with 200+rpm quicker spool!

Tony

 

Shoot me a PM....we do these all the time. The turnaround time on them is about a week. You send your compressor housing in and we mod it and send it back to you. We've done most of the ones you've seen or heard about on the Supra's. We've really got it down to where it looks great and performs great too.

 

silvr94r2: Any pics of this mod availabe???

I guess if you have an engine/turbo combo which does not surge then there's no need for the anti-surge cover.

Wow !! 300-500rpm in lag increase with the anti-surge cover !!!
that explains the small delay in boost between shifts.

JD

 

The lag i stated was with some of the combos we've seen. It really differs for each car depending on setup. We haven't done an RX7 yet other than mine but it hasn't been tested. I really would like to get someone with an RX7 to try this out and see what kind of effects it'll have on a rotary.

I don't doubt that it won't do some good.....i'd just like to see exactly how much compared to the cars we've done so far.