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okay, new info so once again: twin or single?


chris_bramley
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I have been planning on getting a single mod for a while, a t74 or like from BL.

 

however, I'm told the twin is actually more powerful if set up right; apparently if you have a reasonable turbo like a t40-ish size for the primary and a t74-ish for the secondary, set up so each turbo feeds 3 cylinders, this is supposed to produce more power and response. I guess the first one would have to have a very short band and then the second would come in, ooh, I dunno... 3.5k? It would need to have a big band to run a lot of power for long acceleration, I would think.

 

I'm guessing here, I don't know huge amounts about this. If I did, my second turbo would be working properly NOW!

 

This assumes you can fit a t74 as the back turbo... and god knows how you'd program it all in, but that would in theory take care of low end 0-60 on the smaller turbo and then the bigger would spin in as the first one reached peak and give top end at high revs.

 

Is this viable, doable, and ridiculously expensive? Is it worth doing? or are people so enamoured now of the room and slapping just one big'un in that it's the best way to go?

 

Just thought I'd see what people think, expert opinions and constructive crisicism welcome.

 

C

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If you want more power, you wanna go single mate, you can get uprated twins, but they are much more expensive. I'd say go with a t67 you have a manual, or a t61 if you have an auto, these make awesome road cars. Anything bigger on the road is overkill, an you'll have alot of lag.

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After TDi bolted a pair of Garrett GT25/10's to a UK Supra and HKS used a pair of GT25/30's to a USA Supra and ran both cars with their turbo's in sequence, a pair of mental Aussie's decided to go one better and made a compound turbocharging system, using a small turbo (like a T3) to spool first, feeding from 6 cylinders, then transfering the work to a bigger turbine (like a T78) to do the mid-range, and then both working togeather at the top end.

 

Several things.

 

No-one knows who owns the UK car. TDi insist it was still using the GT25/10's 18 months ago, but to the best of my knowledge the owner isn't a member of either this forum, or the other British Supra forum.

 

The 'HKS' car, which was featured in two magazines blew it's second turbine a few years ago. The owner decided if he was going to spend $$$$'s fixing it, he wanted more BHP and fitted a big single. The biggets problem with the HKS car was that there was no pre-spool for turbine#2, it is thought that the shock of it coming online at 3000rpm probably killed it over the years.

 

The Oz car does run, but it's a one-off, with lots custom fabrication parts (some bits were off a washing machine though!). The GT25 based cars only had adapter plates for the turbo's to be mated to the stock manifold. I don't know if the TDi car has pre-spool or it their car is stuff of fairytales, as they have only released three pictures of an engine bay and sod all else.

 

Using a small turbine for cyls 1,2,3 and a big one for 4,5,6 wouldn't work- you'd max out the little guy before the big one got going.

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