This idea may be a little crazy, but i think it leads to an interesting discussion.

Say you have a nice shortblock built for boost, and you wanna go with some twin turbos. and just for example your engine lags a little but has a great top end with two 77mm's, and two 72mm turbos boost right away but dont provide much top end. . .

could you connect the airways before the turbos (to equalize pressure) and run a 77 and a 72? one turbo to get the boost started down low, and one to carry the car through the top end. get that nice full power band.

discuss. .


EDIT: Here is a crude MS paint rendition (i have a laptop, so i drew this with a laptop cursor pad!) i don tknow why its so small, i drew it much larger!

 

Yes, I believe that you can. I think they do that with diesels a good bit.

 

yeah i knew they did that with some hardcore sequential turbo setups, but im not too knoweldgeable about diesels

 

http://www.atsdiesel.com/ATSWebsite/HIWCompounds.asp
http://www.internetage.com/cartercopters/writeups5.htm

a google search produces all kinds of information. BTW, your looking for Compound Turbocharging.

 

that looks like a great idea! how much preusre do you have to be running for this to become effective???

why isn't this used more on petrol engines???

Chris.

 

very interesting, i want to see how this can be applied to gasoline engines. thanks guys

 

This sounds like twincharging...Using a turbo and a roots blower. Roots get the bottom-end torque, and looses all it's efficiency just as the turbo spools up.

Sounds like it could work, but may be a pain in the *** to tune.

 

if anything wouldn't it be easier to tune considering there is a more equal amount of boost along the rpm range?

 

oh.. trust me.. it is

 

come on H8 LUZN spill the beans! hehe

also wouldn't the smaller turbo be a BIG restrictioninthe exhaust trac??? or can you forget about the 2:1 presure thing when using two turbos???

still be nice to see!

Chris.

 

Since you'd be joining the 2 sides of the exhaust and then splitting them again before the turbos, when the smaller one begins to be a restriction it would just push more exhaust to the larger turbo.

I don't see why this would offer any tuning issues. Both sides would feed in to the intake and become equalized. The only concern that comes to mind is that if the small turbo is too small, then the big turbo might want to push back against the small one's impeller creating reversion.

 

I believe that is the setup that many older twin-turbo imports like the Supra TT and 3000GT VR4 used. The idea is a good one, and works well stock, but once you start modding I've heard that tuning them can be a headache.

Hence the reason many Supra TT guys switch to a single turbo once they start making significantly more power over stock

 

form the stuff i have seen on deisel engines they run the exhaust "outlet" of the small turbo into the exhaust "inlet) of the big turbo! so you have a little turbo in the way of a big one! dont you????

as for the little turbo, well it will just be preusring preusrriesd air wont it????

there must be a reason why this stuff insent used more! i just dont know whatit is! lol

i thought the main reason for the supra guys going for a big single (or big twins) was flow???

Chris.

 

One of us misunderstood the original post then. I thought he was describing a situation where the exhaust is joined, then split before entering the 2 different turbos. What you just described is simply sequential turbocharging.

 

yeah hes describing sequential turbocharging, which i was aware of. i was describing them on the same air way but next to each other.

example relating it to an electrical circuit

if sequential turbocharging is a sequential circuit (with the turbos being the resistors). . .then what im describing would be a parallel circuit. does that clarify this at all?

 

Right. My <i>guess</i> then is that this configuration would not result in any tunability issues.
I see no reason why this might not work pretty well. Although it does seem like it might be hard to package and plumb.

 

it would be an involved process to plumb, but iv seen an 8 turbo small block before, which proves that almost anything can be plumbed

 

You stole my idea

With the turbines only connected on the intake and not connected at the exhaust side,there would be some variation in power between the bank where the small turbine and the big one

I have been thining about the Cam and valves setup,woulden´t i need a diffrent valvespring seat pressure on the bank where the small turbine would be because of diffrent back pressure in the exaust?

What about the exhaust lobe on the cam on that same bank?

 

no the pressure would be equalized

 

Why would you say that???

The small one can´t exhale as much as the big one so there must be more backpressure where the small one is