Twin turbo.....which ones???

Would there be any benefit to running two turbos on a 16v motor? Looking at Rich's RX7 build just got me thinking. Could you run a small turbo then a big turbo (compound), or indeed one turbo per 2 cylinders?

so as not to confine this to 16vs, I've seen twin turbo setups on 24v VRs, so what would be the advantages/disadvantages on the 2.8/2.9 (12/24v) as well?

Somepicsof a twin turbo set up on an 8v crossflow longitudinally mounted in my RWD Mk1 that I may get to finish one day

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Long and short if you are going to run 2 turbo's you are best of running 1 per 2 cylinders of identical design and using the intercooler to mix the charge. This way you can get 2 small turbo's to produce 1 bar each giving a compound charge of 2 bar.

The benefits fatter torque curve with quicker spool up providing you get the maths right. Without a restriction of hp at the top end due to a small exhaust housing. Is it worth the hassle if you got the know how it can be fun.

Here's a 1.8t with 2 turbo's recently upgraded the engine and now making 635hp (first car on the page)

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Holy sh1t

blimey..

I don't think we should have started this forum, I'm getting silly thoughts now...

I'm liking the quicker spool and fatter torque curve though. Do you think there would be enough room behind a 16v in a Corrado for two turbots? I guess you'd need to calculate the turbo spec based on a 1 litre engine then, given that it each turbo is only driven by 2 cylinders?

^^^ lol have a look at the pics of the hulsen tuning setup be much the same so will give you a good idea of space

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As for working out the turbo size not as simple as that as you have to keep in account rpm and cylinder head flow not just cc. I opted for 2 x renault 5 T3's. I believe Carlo Hulsen went for a T2 equivalent of a saab originally

JNLRacing wrote:As for working out the turbo size not as simple as that as you have to keep in account rpm and cylinder head flow not just cc. I opted for 2 x renault 5 T3's. I believe Carlo Hulsen went for a T2 equivalent of a saab originally

What block are you using there then? looks like a 2ltr! And how come you went for 8v xflow? What CR?

using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.

Oh right sounds interesting have you used forged pistons? 2 bar sounds like a lot for cast but then you never know what they are capable of when mapped correctly. I'm using cast in my 2ltr 3A counterflow G60 engine and would be interested in your views on cast v forged.

JNLRacing wrote:using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.

I reckon you need to do a build thread

mrbeige wrote:

JNLRacing wrote:using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.

I reckon you need to do a build thread

\

I second that motion.

lol on the build thread it was one of the original build threads on E38 that kicked the trend of on there. The thread fizzled out as I stopped work on it 2 years ago. As business got too busy. It's currently being partially started again as i decided to make some chassis changes to it. It'll be one of those cars that will be done when it is and when it is people will wonder where it came from

However if you are interested I'll post a link in the build thread section to where the photographs of it are up until 2yrs ago.

As for forged vs cast

Rods are pauters and pistons are forged wiseco's. Personally wouldn't go much above 280hp/tq on cast although 325 has been seen reliably on old yank motors with an additional shot of 250hp of nitrous before the rings let go on one of the cylinders.

Link would be good. So why the kr crank in a 2ltr? I take it your using 83mm weisco G60 pistons and 136mm length rods?

Rods are 144's with custom spec pistons but yes 83mm.

Originally I was going for 2 litres to get some extra torque but once I mathematically worked out the engine flow vs the head flow at different rpm levels I realised that the small capacity increase wasn't going to be worth it and I was better of going solid lifter with a high rpm high lift cam for max power.
As the block was already prept I just changed the crank and ordered the corresponding rods and pistons of my choice.