Red-Rx7

{CLICK ME}

Looking at the turbo, it has a second ring at the intake. In trying to figure out what it is, someone mentioned it was an "anti-surge" housing.

I did a search, and didn't really find anything. One post, someone mentioned that this helps the efficiency of the turbo in the upper end of the compressor maps. I was hoping someone could elaborate on it. Also, someone mentioned that a different sound is produced? What kind of "sound" are they talking about?

Any information would be great.

Thanks,
Mike

'//icked

I can't help you out but... I WANT YOUR CAR. AWESOME! Good luck man; it looks like it will be one sweet ride when you get it done.

frode

hades

iTrader: (4)

not to get off topic but where in Kansas are you located? I am at Manhattan, I would love to come see your car if you where fairly close.

$150FC

to your car.

I have seen that on various other turbos. What turbocharger is that?

AFAIK all it does is makes more noise. I have seen it on T51 KAI (i think), some other big-frickin-turbos. I do not know if it affects efficiency.

Barwick

you just wanted to post a picture of your 20B

RETed

That ring don't mean jack.
It's just a way to mount a larger diameter hose/pipe/intake onto the compressor housing.
The turbos were initially for huge diesel truck applications, and I think they all used 4" inlets, and these turbos have smaller < 3" compressor wheel impellers.
It's funny they couldn't transition is nicely.



-Ted

peejay

Then why did Holset make a big deal about redesigning the ring for a broader map?

One would think that with a name like "anti surge" that it would benefit the *low* end of the map, where surging takes place...

RICE RACING

What he said

Its to reduce pressure loss via running oversized air delivery pipes.

peejay

... which would mean trying to run at a higher pressure ratio for a given boost/flow, which would mean more likely to run into surge.

Gotcha.

Red-Rx7

If I wanted to do that, I would have started a thread stating, "contracting (in 2004) the ultimate rotary going into an FD - help me design it ". Then I would have put my pictures in there from my accomplished date of 2004.

Red-Rx7

Thanks. So essentially, that ring is what is considered "anti-surge", but it doesn't do ****. And it makes no difference in sound?

RETed

Do you care how your turbo sounds?

-Ted

Red-Rx7

Damn right. Whoot Whoot!

Lil Sis and Bub Rub promising me my certain noises there RETED. I would hate to be surprised, thats all.

Carl Byck

Ignorance is Bliss TED . Do a search on the Garrett site. There are quite a few Supras running the anti surge cover, it does sound like a T51, and it does improve the surge line a bit. However, it also creates ~150-250rpm more lag in the process. One thing to consider is that the turbos it is available on(at a ~250.00 premium) are not ones prone to surging on either Supras, or 7s, so except for the sound, it does not make sense on those two applications. Red RX, make sure you say thanks to all your "experts"

Red-Rx7

Thanks for the information Carl.

Not sure what you ment by "thanks" to all the "experts" though?

I had quoted Teds thread which spawned the other replies. My origional "thanks" was global, otherwise it would have read, "Thanks {INSERT NAME}".

But Mr. Byck, thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks thanks. Check under your name. Is that what you want?

Zero R

iTrader: (1)

Red, I think Carl is referring to Ted being the so called "expert"on this, you know it was kinda like directed at him.

Carl Byck

YUP, my opinion is free no thanks needed. TED, you used to be my hero, what happened??? I guess that was in ~ '93...

RETed

Okay, want to explain the definition of "surge" then?


-Ted

RacerXtreme7

iTrader: (2)

Carl is correct, and the sarcasm was funny albet at the expense of another.

It’s called a "ported shroud" and it’s not just a bigger adapter for larger turbo inlet. Doesn't it look a little complicated for just a manufacture to be too "lazy" just to make it bigger? The ported shroud is more costly then to just add a smooth bell mouth.

The ported shroud is to combat surge when the turbo is at the upper limits of producing boost and flow (choke flow). A proper ported shroud also has inducer bleeds (small slits near the compressors impellers that bleed between the inner and outer shrouds). The bleed is were the "cool" sound comes from. It can be described as a siren sound when the turbo spools instead of the usual high pitched whistle common to standard inlets.

Most people will NOT run their turbo's so high in the pressure ratios (25 + psi) for the ported shroud to be efficient, (especially on rx-7's) and it hurts every were else except the upper limits. So, in essence its a effiency sucker which makes cool "noises" unless your running insane boost levels.

https://www.rx7club.com/showthread.p...=ported+shroud

Discussed in that thread a little, you can see the “bleeds” in the close up pics in there also.

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

in2twins

In essence, Surge is when the pressure on the compressor side is greater than that on the turbine side, causing the turbo to "stall", or become unstable. The two most common surge inducing situations are when the throttle plates close between shifts creating transient surge(made up term). the second situation occurs when you were at high boost(full throttle), and you move to just enough throttle to maintain your speed. In this second situation, which is the one the shroud tries to mitigate, there is alot of pressure on the compressor side from your "pull", and then very little exhaust energy to balance it due to being at part throttle. A common time for this to occur would be on a road race course, you have just accelerated down the straight, you tap the brakes to set the car(throttle plates closed, initiating surge), and then use just enough throttle to maintain speed through the turn(moving suddenly from full to very light throttle). So that is my version, I could have simply copied the Garrett explanation, but I felt a couple real world(over simplified) examples would be more helpful(if a little less accurate). Thanks, Carl

RacerXtreme7

iTrader: (2)

Ok, just trying to clarify this further for those who are interested, but in all anyone running a turbo rotary really doesn’t need to know about a ported shroud unless you intentionally run a non-proper sized turbo or come up with a widget that makes the turbo spin up insanely fast. or...... you just wanna know were that "cool" sound comes from

Compressor Surge...........

To explain it simply is when a compressor is producing too much air flow/pressure for the engine to ingest. The pressure builds in the intake system to the point were the air leaving the compressor stalls and then backs up into the actual compressor wheel....... the pressure is relieved when this happens then it begins to build again to the point were it stalls then backs up into the compressor again... this is surge and can be heard if severe enough as a "whooomp whoomp" (can also be heard on mal-adjusted BOV's as fluttering instead of one whoosh or one whistle sound). If you look at any compressor map you can see it’s the line on the left of the map island. Like I said, basically the compressors pumping more air then the engine can ingest. This is why it’s important to size a turbo to your engines ability to ingest air. Surge wreaks havoc on turbo thrust bearings and the resonance that’s created can actually break off compressor blades from the back and forth movement or loading and unloading.

Some turbo diesels experience this for several reasons (mostly talking about Power Stroke Fords or other smaller trucks).The most common is the turbo spooling too fast. YES too fast…. Its producing more flow and pressure ratios that are too great for the engine to ingest. This usually happens at low rpm when the engine ingest less air. It could be because the owner put a really free flowing exhaust and intake and the turbine naturally spins up faster, but too fast and the engine isn’t able to keep up till its rpm’s increase thus swallowing more air and now better matched with what the turbo’s putting out. Also more proan on diesels because they are heavily loaded… and some times at full throttle (full throttle on a diesel is just full fuel flow, there’s no actual throttle butterfly) the engine can be held back from accelerating to higher rpm’s do to pulling such heavy loads. This full throttle is producing sufficient exhaust energy to spin up the turbo to target boost setting, but the transition from making more boost to the engine revving up enough to ingest it hasn’t happened. This is a less problem on passenger cars because they’re not loaded in such a way. As the turbo makes more boost a result is the engine accelerating and ingesting more keeping up or even surpassing the turbo flow out put (lag) or at some point the turbo running out of “puff” ands falls out of effiency pumping hot air (seen as a loss of boost at high rpm’s).

Ported Shroud...........

The ported shroud in essence acts like a passive bypass valve. It recirculates some of the air that’s stacking up at the compressor inlet during surge. The air bleeds are a part of this system. The air bleeds also make the "siren" sound when the turbo spools..... this siren sound does NOT mean your compressor is in surge. Infact the siren sound means the bleeds aren’t bleeding in the intended way of buffeting surge, but the sound is a siren sound because the bleeds located at the tips of the inducer blades. The blades spinning by these open ports chops the air up and makes the "cool" noise. During surge when the ported shroud and air bleed are working, there’s no siren sound anymore but just a standard inlet sounding high pitched turbo whistle. i need to mention also, because this buffeting effect a ported shroud does broaden a compressor range. But this range is broadened near the surge line (were it doesnt matter on most cars) and its at an expense of effiency everywere else on the map. As I said in another thread, why loose points of effiency on the fat part of the map islands (were your trying to stay) at the expense of surge buffeting that you'll never see? Cool sound I guess. HKS gets a little bit of the best of both worlds with their slightly smoother inlet and smaller shroud.

super big industrial centrifugal compressors actually have a bypass valve built into the system so when surge happens, they simply recirculate some flow coming from the compressor discharge back to the inlet. The ported shroud on a turbo does this passively useing some of the surge to work. Some aircraft turbine engines have ported shrouds also on their compressor inlets that work very similar to the turbo charger's ported shroud.

Choke Flow...............

Simply a restrictive intake. Make the intake bigger = less restrictive. (3" standard intake, then make it a 4" and you lower the choke flow threshold).

I hope this clarifies and doesn’t confuse anyone further. If have gotten any thing wrong, please someone correct me if you know otherwise.

~Mike…………….

RETed

I still think it's BS...

The initial pic shows a turbo with no slots cut into it, so that can't be a "proper" surge?&nbsp; So is it half-assed?

I always though the "ring" on the T51R Kai series turbos were for an insert.&nbsp; I got to check one out up close, but I never examined it under a microscope before it got sold.

The surge line should not even be a big deal if the turbo is sized properly.&nbsp; It sounds like this surge thing is band-aid fix for improper sizing.&nbsp; Therfore, this is not an issue for proper application of the turbo.&nbsp; The surge line is there for someone trying to boost too high on too "small" an engine or too low RPM - neither is very "smart".

If the airflow is surging back through the compressor section, something is seriously wrong with the whole system.&nbsp; I believe the BOV has the responsibility to prevent such an occurance?

If this is such a hot thing to do to turbos, why isn't it done to some of the bigger, big boost turbos?&nbsp; All I see is talk about the ASME funnel...but nothing about this surge crap.

Why is the dimensions made arbitrarily the ID being the compressor wheel inducer and the OD a nice round number like 4" - i.e. TO4E, Garrett GT-series?&nbsp; Shouldn't ideal dimensions be something other than 4" minus inducer?&nbsp; Why is the HKS T51R Kai smoother out and the Garrett design looked like some ash tray?

I still don't buy it...


-Ted

RacerXtreme7

iTrader: (2)

I'm not claiming I invented the internet here, its not my idea nor theory. I'm simply explaining what turbo manufacturers and LARGE turbine manufacturers do to buffet surge. It works, but like anything at a cost. You have to think out side the proverbial "performance car" box and realize that turbo's are meant and manufactured for other applications other then making your car go fast. Turbo's are found on agricultural engines, big rigs, water pumps, and generators etc. that have different requirements and operate in different ranges then a passenger car.

See above......... different applications for same turbo are possible. But yes, on a performance car surge line should be avoided, but like I explained already passenger cars aren’t held at low rpm at WOT. Cars will accelerate when the gas pedal is pressed, if you load your car so badly that the load is so great that you cant accelerate at WOT you need to unhook the building from your bumper. Were a heavy *** rig is towing TONS of weight and going up a gradient it might possibly not be able to accelerate in engine RPM's but the load is there and the throttle is opened producing sufficient exhaust to make the turbo spin up and produce more boost then the motor is willing to ingest. And furthermore, I and someone else already said and explained that the ported shroud isn't applicable to OUR cars nor most performance passenger cars.

I thought you were knowledgeable enough to understand something as trivial as surge. Airflow doesn’t necessarily reverse, but pressure waves and sound waves do. More or less its pressure stacking up to the point it reaches the compressor. The comp is over whelmed and not much pumping goes on relieving pressure (eventually the engine gulps up this stack while the the flow stalls relieving pressure built up) then this unloading lets the compressor do its deal and make more boost which begines to stack up again etc. And yah, if you have AIRFLOW backing up that far something is WRONG and the surge is extremely severe. Your turbo won't be able to handle that.

A BOV ONLY works when there’s a pressure differential on either side of the piston or diaphragm. Such as a closed throttle, your source line is behind the butter fly valve, so when the throttle is closed there’s near 0 boost or vacuum which the top of the piston or diaphragm sees, while the opposite side thats in the intake stream is seeing boost, so the piston move up and relieves the pressure. Opposite when your at WOT (wide open throttle) and both sides of the piston or diaphragm are seeing the same boost pressure but the piston or diaphragm is held shut because spring tension.

See the attached pic, I highlighted the bleed ring in green, YES there is bleeds in that turbo compressor housing. And it’s called a PORTED SHROUD.

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

RacerXtreme7

iTrader: (2)

Pic

BTW, dont trust my pic just ask the guy who started the thread, I can see them in the pic clearly, but I know what I'm looking for.