So then.... now i have decided the spec'C' is staying in the garage im in need of a few new mods... the main being 400bhp....

What are my main needs???? An engine re-build to be safe??? turbo etc???

 

Without being an expert on the Spec C, I'd say you'll get there a lot easier than most

 

18 or 20G turbo, remap, ported headers, Decat

 

That would turn out to be expensive.

I think Powerstation do some twin scroll turbos capable of 400bhp.

Personally I am greedy, if doing a turbo swop I want 420-450bhp but then you are into more lag blah blah which I don't want.

 

mmmm So all i really need now is a new turbo and some ported headers??? or could i just get a turbo capable of 450ish...

 

one word: drivability..!

If it's a daily driver then chasing figures is not the way to go. As said, big bhp= big turbo= more lag= less drivability..

IMHO (genuine) 350 ish with good response makes for a quicker road car than 400+ with poor response.

 

have a look at hols \ Bob Rawles thread in projects

 

maybe try a custom made hybrid, i believe scoobyclinic delveloped one for there sc450 engines, might be an option to look at a custom roller bearing turbo to keep spool up times quick

 

not my daily driver....

Didnt think 400 would make much difference as its already 350 fairly easily...

 

the headers on your car are stainless steel equal length so there is no need to port them, i also think its hard to find a better set in the aftermarket ones ??? you really just need injectors, hybrid twin scroll and maybe a good fmic and filter plus the dreaded remap

 

best i get looking for a few items then....

 

Steve,

what hybrid TS blower makes a comfortable and genuine 400bhp?

Spec C, the turbo is your real concern here, the exhaust housing is limited to about where you are at present and to make a genuine 400bhp you'd also need larger injectors and ideally an adjustable fuel pressure regulator for better atomisation of said fuel - I see no need for a front mounted intercooler unless ofcourse you're looking at extended track use.

 

Will defo be in contact soon zak... Front mount might be needed then as i do enjoy a good track day....

 

I would take a look at the webmasters and Bob Rawle threads of this site. They will both be full of useful information for you.

 

im in the process of reading said thread..... just taking time.....

 

so then which turbo.....

 

There isnt a twinscoll yet mate that will offer you the 400bhp potential.

Youre limit is 360 with what you have

You need to either go single scroll TD06 20g (49lb compressor wheel) or bigger or wait for someone to get off their *** and manufacture uprated twin scrolls

 

The restriction seems to be the exhaust housing. As the compressor side can be mated up to what single scrolls have. Just needs someone to start casting a bigger exhaust side to take a bigger wheel. By doing this though it is more than likely to give more lag.

When talking to Iain Litchfield when he was developing the T25 it really is a trial and error process with turbos and the proof of the 'pudding' is trying it on the car rather than going by turbo manufacturers ratings as they always seem to be a very 'rough' guide.

APS have brought out an interesting rotated twin scroll but I would not fancy being a guinea pig for it See thread below;

https://www.scoobynet.com/drivetrain...in-scroll.html

 

Zak's right. Trying to get anywhere near a reliable, "genuine" 400bhp out of the twin scroll turbo is just unrealistic, as the TS exhaust housing just can't take the flow, or the heat, and starts cracking.

Currently, the best solution is to convert to a single scroll, but to retain a twin up pipe to the turbo.

Edited because I thought I was on 22B.com (it's late !), and Shaun would have killed me for talking about a product


Mark.

 

Litchfield and Powerstation are about the only two suppliers who can provide anything off the shelf quickly.

You could get something along the same lines as Shaun, or even try one of the units designed for the first T25's.

The ideal solution would be a GT30 garrett centre in a bigger exhaust housing, but as Mark has stated, everything is a compromise and you would gain a little lag.

Stevebt had his unit modified, using a Spec C core if you wanted to PM him, but again I think the hot side was the limiting factor. He has now gone for a Garrett.

I have gone a different way to Shaun, by trying to eke as much as I can out of the VF37 standard unit, using ancilliary parts. Im very happy with the results and lack of lag, but there will be no more to come, until a bigger turbo.

Im staying with what I have for now as its so nice to drive and the power is always there (also I currently have 3 bathrooms to pay refurbing on ), but I may look again in the new year.

 

What injector size does the Spec C have std. I thought 550? in which case 400bhp would be achievable.

Should need around 560cc's fuel flow per injector for 400bhp, so at say 4 bar fuel pressure 550's should flow closer to 630cc's. enough for a bit of leeway I'd say.

Std intercooler would do as well. Just need a turbo up to the job

Dave

 

My car ran out of 'duty' on the STI injectors at around 370Bhp. The STI top mount started to struggle with the heat from the standard turbo at that BHP. But the main limiting factor found was the injectors.

We got a bit more by adding water injection, which makes the car richer at the same time, but not by a huge amount.

I now have 650's fitted, which I would recommend for anyone looking for more than 380.

Remember, that is standard VF and not some hybrid! (20g/GT30 etc), as the extra flow will bring power on its own.

 

Sometimes a pic is worth a 1000 words, easier than explaining..

Lateral twinscroll/Garrett kit.

 

So would that be my best option???? to swap???? rather new to the Higher end bhp....

 

David,

Do you know has this been tested and how does it compare to a comparable single scroll.

Looking at the pipe the gases are meeting each other just before it then goes into the turbo. Could that not mean even less efficiency than the single scroll set up as the gases have caused turbulence. On the single scroll the gases meet as soon as they come out of the headers so have chance to be less turbulent by the time it gets to the turbo.

IYSWIM.

 

I would just like to point out that I didn't design the kit, but I am stocking it.

With regard to the turbo's, there just isn't a suitable alternative twin scroll housing currently available.

I have heard of some people offering bigger twin scroll options, but the only Garrett twin scroll housings of a suitable size are from diesel turbo's, and these housings have been tried, and tested for similar applications, and crack over time, due to the heat generated from a petrol engine.

Whether it be this, or another single scroll conversion kit, currently I think it's the only way forward for 400bhp +


Mark.

 

Thanks for reply Mark.

I never realised a diesel turbo exhaust housing was made of a different material mix to a petrol version turbo housing. Well, they say you learn something every day.

 

The twin pipes have been kept long to keep the gas speed high, and the transition to single pipe has been kept a smooth as possible.

There are several inches of straight pipe/turbo intake to smooth flow before the exhaust wheel.

It's hard to exactly compare the twin scroll conversion set up, to a single scroll set up "like for like", because the IHI, and Garrett GT series exhaust housings are not identical in size, or flow, but it would appear that the twin to single scroll conversion is faster spooling.

There will be more testing of different turbo spec's, but the cores will be based around the MD321H, & T series bolt on turbo's, which cover 400-450bhp.

Mark.

 

So my best option is to revert to a single scroll for 400ish+ish
think im getting there....

 

Go for the up-pipe above and start a project in projects thread. If it works well all us other twin scrollers can play follow the leader