Ive been contracted to do a very unique project for a serious customer that requires an unusual setup. the project will use dual garret ball bearing turbos, however the turbine has to be very small, like t25ish, and absolutely must have an external wastegate.
the compressor has to be able to support 400HP, preferably more.

it doesnt look like any of the smaller GT series turbines are externally gated, so i need to know if any small, externally-gated housings from any other series will hybridize with the GT center section?

i would try hybridizing holsets or schwitzers if it were mine, but the customer demands ball bearing CHRA's. please dont post just to say 'what a dumb idea..'

thanks for your time
mike

 

anyone?

 

PM Sent.

 

400hp from a t-25? or 400hp from 2 t-25's? This project is not inpossible but might have some difficulty meeting your customers wants and needs. TUrbo elements should be able to help you with their knowlege of F/I

 

T25ish hot side, coupled to a massive compressor, preferably capable of 500 per compressor. F1 is along the right lines of thought.

 

Why not consider the GT2871 and weld the flapper shut and run an external wastegate. You should be able to get close to 400 and have very quick spool. If you miss match the compressor and turbine too much you are going to cause other problems and not have a very effiecent turbo.

 

other problems such as?

if the compressor is rapidly spun to its preset boost pressure and then the manifold is effectively drained of excessive pressure by an adequate wastegating arrangement, how would the compressor be inefficient? i believe trying to make a midsize turbo push big power would be worse.

 

GT2540R. Made 400whp and 335ft-lbs on an SR20DET at 19psi on pump gas

http://www.freshalloy.com/site...vapor/

 

Well for instance my buddy had a shop build him a custom turbo using a GT40 Compressor wheel and some small turbine wheel, sorry I don't know the specs on it. He runs two external 40mm wategates and his car made 856whp but after a short drive with no boosting it overheats. They tried tuning it to a more reasonable 22psi and made 542whp and yet it still overheats. This is with a very conservative tune. He was told the small turbine wheel had to spin too fast to create the boost of the larger compressor wheel and it caused more heat. Also since the wastgates don't open until full boost is reached that small turbine is holding back all the exhaust. Thats why even at part throttle he had overheating problems. If he is dead set on twins I don't think you could choose a better turbo than the smaller 2871. Quick spool and can make good power. Thats just my 2 cents. Good luck either way. The 2540 has made some great power but its also been said to be mismatched causing slower spool than other simalar turbo's.


Modified by TS4L at 4:58 PM 6/28/2006


Modified by TS4L at 5:01 PM 6/28/2006

 

hmm.. valid points i hadnt given much thought. ill definately have to add water cooled CHRA to the list of must haves..

thanks alot

 

Anything to help another car guy! Please let us know how this project comes out and good luck to you in your build.

 

going back to your friend.. youre saying that the engine overheats correct, not the turbocharger? did the turbo have a tendency to burn the oil or anything like that?

if your friend was running a digital boost controller that would hold the gates closed until full boost. he would be best to disable the controller for street driving so that the springs are allowing the gates to crack open prior to that, bleeding off exhaust heat. i wonder if the timing being set "too conservative" could have been igniting the charge while it were in the exhaust manifold?


i guess we'll consider ceramic coatings and increased cooling capacity in this setup. i promise that it will be different than anything conventional. we're looking for an old Indy turbo era engineer right now, prior to solidifying the design.

also it would be nice to find an insider from garrett/honeywell or an engineer with turbocharging in his background.

 

He is using an electronic boost controller but even shut off it and at low boost it gave them problems. They ended up changing the exhaust housing to a slightly larger housing and were able to get it tuned again at 22psi and not have any problems. They obviously lost some spool but made about the same power. I think if properly matched you could make something that will work but it will still be far from efficent.

Personally I would look into the twin scroll turbos as they net very quick spool and then can open up and still flow enough to be efficent. Dent Sport garage is using one on there 240sx and it spools super quick and makes good power.

Good luck on your project!

 

id love to, but you really cant route 3 cylinders evenly between a split scroll, and im not up for experimenting on the outcome of the imbalance on a customers car.

 

if its small and bb then its a t28, i have one on my civic and love it. spools so fast it doesnt feel turbo, much more like a supercharger, the only thing you can do to make it flow more is get a larger t3 compressor housing for it. thats what i did and it opened up a hole new power band, tha twin t28 set up will yeild 400 properly done. having the larger housing i have noticed heat soak problems a few time after long hard drives. the t28 is a t25 exhaust side paired to a t3 compressor.

 

glad to hear your setup works well. we're looking for 400-500 per turbo though