Twin turbos and ~500rwhp.

[chrisBoid]

I was musing today about where I want to head with my performance modifications and a few questions came up regarding possible turbo setups.

I like the twin setup because I like having the power early.  Moving to a big single (e.g. T51) sacrifices that low end power.
Having a medium size turbo (e.g. 2835) that spools faster sacrifices top end.

Soooo, why not have twin medium size turbos?  Fast spooling (compared to the big snail) and a big hit.

Is this sound reasoning?
Is the only thing that stops people doing this the obvious price tag comapred to a big single?
Am I worrying over nothing in regards to the spool up time of larger turbos? - When does a T51 come fully on line - 5000rpm?  What about a 2835?

I\'ve read about an FD running twin 2835\'s that produced 478rwhp (with street port).

Ta.

Chris.

[chris]

I have twin mediumish singles on my 96 fd, see attached thread. :-) which has been dynoed at 405 rwhp!

I would say it has been a pain in the @rse plumbing them and getting sufficient clearence, but it seems to give the desired result.


http://www.mazdarotaryclub.com/forums/showthread.php?s=&threadid=11785

[Shark]

I agree with you Chris and personally like the twins, but a single would be more economical if that is a factor in your mind.  With the right porting I would think that you would be able to spool up a big single turbo earlier than 5krpm but doubt it would be any earlier than 3k.

Again I\'m guessing here, but I would guess that big single would also be cheaper.  medium twins would mean a lot more complexity in the plumbing (especially if you want to keep them sequential) and perhaps more tricky space issues.  Issues in my experience invariably don\'t go away till you throw yet more money at them.

Gregor

[chrisBoid]

It was this setup which got me thinking: -

http://www.urbanracer.com/articles/anmviewer.asp?a=843&z=16

chris : I assume yours is non-sequential?  How do your hybrid\'s compare to the standard Hitachi\'s in the FD?
Comparing your dyno sheet with mine regarding spool up: -

Revs : hybrid (non-seq) (rwhp) : Hitachi\'s (seq) (rwhp)
2500 : 50 : 70
3000 : 100 : 110
3500 : 125 : 150
4000 : 180 : 170 <-- hybrid\'s overtake Hitachi\'s and power off into the distance...

That tells me they spool up pretty quick.

Do you have any pics

[cruiser]

Problem with spooling two bigger twins is the flow of the engine. It just doesnt flow enough to spool them faster as the equal sized(2x) single turbo.

[bnaellis]

I think you can have the best of both worlds with turbo spool up and good tope end power with a single turbo. Depends on the whole package.
The white single turbo I had was a to4r turbo with.84 a/r housing.
max power was 424 rwhp running way to rich still.
2500 rpm 60 rwhp
3000 rpm 100 rwhp
3500 rpm 135 rwhp
4000 rpm 180 rwhp

which is pretty much the same as you guy\'s

rgds

[chrisBoid]

It seems that the first 4000rpm are the critical ones, but as you say Brian, they are all pretty much the same up to this point.  I\'d like to see the dyno results for the twin 2835.

I\'m feeling more confident about the single turbo as the best all round route to go down.

[<--rYaN-->]

You after this sort of thing??

http://www.rx7store.net/index.asp?PageAction=VIEWPROD&ProdID=885

[chrisBoid]

Yep, that\'s the kind of thing, good find!

[jetpilot]

Hi Brian
Just out of interest buddy, was or is that engine ported, and what kind of boost is that running.
Thanks

[iaint]

Originally posted by <--rYaN-->
You after this sort of thing??

http://www.rx7store.net/index.asp?PageAction=VIEWPROD&ProdID=885

Mmmm, less than £2k at current rates!  I\'d think that the downpipe might not fit on a right-hand drive car though...

[John Yorke]

Quite honestly I think a well set up single [read well tuned] is by far the best way to go, there are a number of peeps who have had a go but unless you run them sequentualy you wont make any low down grunt, and, we all know about the rats nest and resultant problems that come with it. I cant see a medium pair of twins spooling up much faster than a good sized single, besides look at all that extra weight and engine bay bling you would have to polish:rollin

[20B_boy]

http://www.rx7store.net/index.asp?PageAction=VIEWPROD&ProdID=885

For 400 at the wheels I\'d just go with a single HKS or Trust kit or a GT35R. Those twins probably look cool but I cant imagine they are going to spin up any faster off one rotor each than a single of greater size being pumped by both rotors? For all that hassle I\'d want bigger HP potential too personally

[bnaellis]

Originally posted by jetpilot
Hi Brian
Just out of interest buddy, was or is that engine ported, and what kind of boost is that running.
Thanks

Yeah engine is well ported. it was 1.1 bar when it was dyno\'d but it\'s now mapped to 1.4 bar

rgds

[AVENGE]

A good twin set works better than a big single in my opinion and ive ran both. For a big single to work up top it has to run a big exhaust housing, around 1.06 or 1.22 Q trim, which means no matter how well tuned it is, you wont see boost below 4500rpm. Drop the exhaust housing size to bring boost on early and you will just strangle it up top.

We went to a twin 700hp [gt35] roller bearing set up with relativly large .63 exhaust housings, it still boosts much earlier than the single and has similiar top end. For a streeter i would run smaller exhaust housings on a twin turbo set up.

Marty