legacycentral bbs

inspired by a dual charged sti pic i saw over at the soc i began thinking of how i could make it work. i figured out everything except for one thing. pressure equalibrium.

bascily the problem is if you plumb the compressors to Y into the same pipe before the throtle body the supercharged air may want to go back into the charge pipe from the turbo and vice versa when the turbo is spooled if you spool the turbo higher than the supercharged air.

so i figured you could take care of it by dual throtle boddies placed next to each other so the air would be segrated until they reached the manifold. but both the tb's woudl be open at the same time creating a similar problem.

thoughts???

check valve

Don't these types of setups usually turbocharge the air going into the supercharger?

Steve

it would be useless to turbocharge the air going into a roots blower because it compresses ambient air the same way it would compress compressed air. that and the point is to bet boost in as soon as possible reducing lag.

unless of course you set it up twin scroll style on the turbo using the superchargers compressed air to spool it but that would kinda defy the point too.

check valve wouldnt work but the benz supercharger has a electric clutch that could be used to swich the charger off after the turbo spooled but you would still have the equalibrim problem with the open pipe which you could techicnaly close with a throtlebody type dealy with an ecletrical servo motor for an rc car or something that activated in sync with the ecectric clutch.

but also wouldnt sequential twin turbos have this same problem too if one was bigger than the other and they were running different amounts of boost.

I think Steve's right -- the compressors are generally plumbed in series, and the supercharger is shut off via a clutch once the turbo is spooled up.

what about just going with a twin scroll setup?

the way roots is designed thought doesent alow flow through. and using it to spool the turbo is stupid.

twin scroll is cool but im not sure of if its just headers or if its a spesfic type of turbo. plus its not uniqueish.

i was thinkin somehting like this


but im woried about the supercharger fighting the turbos. before the turbos are able to spool

Why a Roots blower? Vintage Bentley fix?

Steve

hm, nice in theory. cramped in execution. Where do you propose to put all these goodies?

I'm willing to bet that super is on a clutch as mentioned earlier. There are many old MR2's that have this setup, it goes super into turbo into intake manifold.

That is an electric clutch SC, you can see the two wires leading into it.

mount it like this

so you think the sc will fight the turbo???

I dont see you having enough space for that

twin scroll is definately unique. How many cars do you know with a twin scroll turbo? I can think of three. It needs a manifold and matching turbo in order to work. Also on our cars you need the new style oil pan.

I don't want to rain on your parade, but I think your time, energy and resources would be better spent on a top-notch, well-matched turbo and high end supporting mods. Much more efficient, compact, and less complicated so less things can break. I was out at Archer Racing the other day and they had an SRT-4 in there that had a custom unit from garrett with dual ceramic ball bearings that he said started to spool about 1800 rpm, and is equivalent to about a 20g. Little steep at $4800, but one bad-ass turbo. That neon was making about 440 to the wheels.

But hey, if you are that ambitious and want to have a really unique setup, more power to ya. I will say that I do like being different, that is why I've decided to stay with my 1g legacy.

Just my $.02

this setup will be in a wrx so space wont matter.

one of the more main reasons we want to do this is because his turbo is really big and doesnt spool till 2nd gear but makes tons of power. its an auto too so the max is a brake stall of 4800 for launches. that equates to about a 13.xx at 135 mph on the strip. we just need to get it off the line.

we are gonna build a twin scroll header for it but we still need to find a matching turbo for it. also we need to get it custom cliped for more top end without suffering on the bottom. finding a turbo alone for less than 3k at that level is gonna be hard (and i laready know where to get one for more than above said price). so a supercharger is a little more cost effective.

two words:

Anti
Lag

true.


BUT THAT DOESNT ANSWER THE QUESTION.

yes it does. Type up a list for us why you want to do this setup.

FWIW, roots style superchargers can only be about as big as the m62. Larger (like the m80) and the mass of the screws prevent it from revving very high. Seems like the first thing to do is see how well supercharger X will flow, hooking it up in series would sure be a lot easier.

I'm not to knowlegable on AT's, but can't you load the engine by standing on the brakes?

I think you should do a little more research on clipping turboes.

Some of my friends have told me about nitrous systems that can be set up to shoot just at low rpms till your monster turbo spools up. Might be simpler and much cheaper.

I've never liked the idea of nitrous, but at the strip it really doesn't matter

While the supercharger may be "cost effective", I have spent about $1000 on the charger and setup alone, and about 100 or more hours fine tuning it. It didnt take long to actually get it to work, but to get it to where it is today I have ALOT of time into it.

Oh yeah, the other option would be twin supercharger, which theoretically, on my setup, put about 14 psi into the motor at 2000 rpm and about 18 at 6000 rpm. With a little work you could hit 20-24 psi instantly. Or so it would seem. All it costs is money.

Ah, I see. Maybe it would be also be possible to go with a sequential twin turbo setup that was actually mated correctly and ran correctly. Using some form of control you could have it where the small turbo would have a really large external wastegate (like the size of the exhaust) that led right into the large turbo. So once the large turbo starts to spool you open the wastegate and it gets all the exhaust flow. Course you would probably want the exhaust piping to flow to both turbos and just have the wastegate plumbed in between the small turbo exhaust and the large turbo exhaust. It would take some creative thinking but it could work.

azn2nr wrote:this setup will be in a wrx so space wont matter.

space ALWAYS matters.

the more main reasons:
turbo is really big and doesnt spool till 2nd gear
max is a brake stall of 4800 for launches
we just need to get it off the line.

twin scroll header...
but we still need to find a matching turbo.
get it custom cliped, more top end
without suffering on the bottom.
less than 3k
supercharger is a little more cost effective.

There. I made your list for you. Care to add any other reasons before you get educated?

douglas vincent wrote:While the supercharger may be "cost effective", I have spent about $1000 on the charger and setup alone, and about 100 or more hours fine tuning it. It didnt take long to actually get it to work, but to get it to where it is today I have ALOT of time into it.

Not to mention, a motor in the process too.

azn2nr,
no offense buddy, but it will do you well to use your head for more than desperately trying to fight off the good advice people are providing you. the immediate answer to your question was the first freaking reply: "check valve." you need a high flowing check valve (like a reed valve, or perhaps a well-machined throttle body that you can actuate by pressure) to prevent the "equilibrium" problem you are talking about.


also if you guys are looking into sequential turbos, ford powerstroke diesel engines have this thing called an "exhaust backpressure valve" that might work better than a large wastegate. the powerstroke valves are just thick butterfly valves. they are designed for reasonably high heat-- they are placed right at the turbo outlet on these diesel engines. wastegates don't really open much so one would compromise flow quite a bit. 1 or 2 of these EBV's might do the trick. there's actually one on ebay right now for sale separately from the turbo if anyone wants to mess with one. also another thing to worry about is "pre-spooling" the 2nd turbo so it doesn't snap from 0rpm to like 100,000 in a split second. maybe another EBV would help here...