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Author Topic: Can you run a 2510 and a T78?  (Read 671 times)

ph1

  • Guest
Can you run a 2510 and a T78?
« on: June 10, 2001, 03:09:12 AM »
SkylineUSA
Registered User
(5/26/01 8:26:09 am)
Reply  Can you run a 2510 and a T78?
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 Anyone running a 2510 with a t78? Theory being the 2510 will spool quicker, then when that runs out the T78 will be at full spool. Any thoughts on this? Would it work?
 
hipogtr
Registered User
(5/26/01 12:51:11 pm)
Reply  Re: Can you run a 2510 and a T78?
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 Mmm... Can't say I've heard anybody try something like this before. I'm assuming you're aware of the size differences between these 2 turbos?

Possible reasons why it isn't such a good idea include: turbine backpressure, heating air charge, reversion, etc. Assuming standard exhaust routing, by the time you get the T78 in the zone the 2510 will be so far off the map that you'll be replacing it from bearing failure.

Hope this helps.

Cya O!

SPOOLIN!


 
EVL BUNNY
Registered User
(5/26/01 5:02:45 pm)
Reply
  Re: Can you run a 2510 and a T78?
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 same kinda thing on the subaru tractors =P
small feeding the large.
maybe why the primary turbo always claps out on them.

for the price of a t78 you could go twin t3/t4
to your own specs of cause =)
then your car would pull harder then a bald man at a peep show

 

I LIKE MAKING THE TOAST...
 
rowdyrotary
Registered User
(5/26/01 9:43:59 pm)
Reply
  Re: Can you run a 2510 and a T78?
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 thats the idea of a sequential set up, unless it is set up right to pull 20psi all the way from 100rpm above idle all the way to redline, sequential systems are a nightmare, always blowing vacuum lines and all the other associated stuff that goes with them
 
Blaup
Melbourne Ozzy Admin
(5/27/01 11:43:14 pm)
Reply  Re: Can you run a 2510 and a T78?
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 What about anti lag as an alternative to get good response, use say methonal and an injector or 2 if its a gtr to dump some in the pipe to keep the turbos spinning, of course you need a suitable ecu to control this.

Its possible to time the 2 injections for a twin turbo setup like gtr so that they cancel each other out sound wise, well help anyway so less popping like the rally cars.
Then you could just run 2 x 3037's or if thats a bit large run 2 x 2535 or 2540's

E

 
SkylineUSA
Registered User
(5/30/01 1:42:28 pm)
Reply  Thanks guys
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 I was just wondering if it would work. I guess it would take someone with a lot more experiance than what I have to be able to set it up right. Oh well, it looks like I'll go the 2535 route like Blaup suggested. Thanks again for your inputs.
 
MarioGTR
Registered User
(5/31/01 11:25:03 am)
Reply  Twin turbo / different sizes
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 SkylineUSA:

No, it doesn't work properly and with turbos of that magnitude, you'd split the crank with the load differentials.

It is far too complex to go into all the reasons why it isn't feasible, suffice to say that if you really wanted to do it properly, you'd have to go to a proper sequential or even staged setup.

That said, it would be very difficult to design and implement such a setup on something like the RB26DETT - there just isn't enough room for the additional piping, etc. that you'd require.

Mario.


 
SDU President
SDU Club Prez
(6/2/01 10:39:07 pm)
Reply
  Re: Can you run a 2510 and a T78?
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 Mario

We could make this work !!!!!!

It would require some ingenuity but I can see no reason why not, the 2510 might be a bit small but otherwise ok.

It would require the use of a closure flap or trap door.

If we ran all of the exhaust gases through the large turbine and then out its dump pipe into the smaller turbo, this would begin the spooling of the large turbine and drive the smaller turbine to actually make boost.

No waste gate would be required on the small turbine because the secondary / larger turbines wastegate would be vented away from the small turbo.

There would have to be a flap in the pipe between the large and small turbines to allow the larger turbine to "breath" at higher RPM.
This could be made to open slowly at a specific boost pressure by use of a line restrictor.

It would work.

Or then again you could bolt on a supercharger and have boost from 1000 RPM all the way to the redline.




Rob Bryan
Club President
Skylines Downunder Car Club Inc.
 
R U NUTS  
Registered User
(6/2/01 11:40:52 pm)
Reply  Re: Can you run a 2510 and a T78?
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 hi rob,

just wondering, from ur perspective view, which one is really the better solution when dealing with this problem, installing a nos, or da "flap" or a supercharger ?? cost-effective, drivability and reliability ? how bout "anti-lag software" ?
 
MarioGTR
Registered User
(6/3/01 2:40:41 pm)
Reply  2510 and T78
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 Rob:

Sorry, but it would not be that simple. You have to remember that:

The turbines must each receive not only exhaust gasses to drive their respective impellers, they must also have outputs that go via the intercooler into the surge tank (inlet plenum). This would induce reversion into the slower spooling turbine akin to extreme surge.

Even if you have a 'flap' that closes off the input (to the intercooler) from the larger turbine, you would need to vent the compressed charge somewhere (ie: waste all that energy). Not only that, you'd be robbing the secondary turbine from the heat required to drive its impeller and incurring a far greater loss through backpressure by attempting to drive two (subsequently smaller from your example) turbines from the same exhaust charge.

Allowing one turbine to spool before the other and using wastegate bypass to drive (and attempt to control!) the second turbo, regardless of size, would also mean a distinct flat spot during the pre-spool stage (prior to swap) of the secondary turbine. The only way to eliminate this would be to go to a direct sequential setup (ala VSV on the TT Supra) which would have copious amounts of piping to achieve the required effect (there is nowhere near enough under bonnet room to do this).

In the simplest case, in order to run two turbines of different size (or even different A/R housings on the exhaust side) in a twin setup, it would mean that you'd have to forgo any form of crossover post engine, prior turbines, which would induce uneven crank loading and in extreme cases, crank deformation or even failure.

Assuming the difference between the turbos is very small (in one example I have tried, primary was 0.64 A/R and secondary was 0.71 A/R) the loading differential was still excessive, but nowhere near as damaging as the surge that was induced through the secondary compressor due to the primary achieving full spool and literally forcing the secondary to stall.

Simply put, it is simply not feasible to run two different sized turbos in a conventional twin setup. Others have also tried and come to the same conclusion. Basically, if it was achievable, you can bet that everyone would be doing it.  

Before someone jumps in to mention staged turbines (as used in tractor pulling contests, etc) keep in mind that these guys have massive engines with huge amounts of exhaust charge to work with. The little RB26DETT simply doesn't provide the amount of energy in the exhuast gas (especially down low in revs) to succesfully initiate spool in both turbines.

Mario.

 
SDU President
SDU Club Prez
(6/4/01 12:31:58 am)
Reply
  Re: Can you run a 2510 and a T78?
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 Yes, No, maybe.

The outlet from the primary turbine would require redirection to a non pressure area such as the Secondary turbine intake.
This would be triggered at the same time as the transition flap which closes off the flow to the exhaust housing of the primary unit.

Exhaust gas generation is directly proportional to power output.
This is why many people use NoS as a pre-spool.
The earlier the engine produces boost on the primary turbine the faster the secondary unit will reach boost thresh-hold.

Exhaust turbines are not driven by heat, they are driven by exhaust gasses.
Last year I replaced the turbines on a 60ft cruiser that had the turbines running about 1.8 meters from the engine.
The manifolds where jacketed as per normal marine systems.
The engine ran 2.8 Bar of boost all day at 2800 engine RPM
and the turbines never ran above 300 deg C.

But I will admit this is starting to sound more and more like a staged set-up rather than a dual driven system.
And the under bonnet space issue is a definite problem.




Rob Bryan
Club President
Skylines Downunder Car Club Inc.