following from the Anti-lag thread, 30psi.
Turbo Mini Forums

Not wanting to start a row, but asking a genuine qustion.

Tom suggested that 30psi is impossible or pointless due to air temps, and intercooler requirements.

I tend to disagree. If the turbocharger was suitably sized, then air temps will be high, but not as high as to pose a major problem to any decent intercooler.
Yes, something like a baby T2 is NEVER going to do it and would be totally pointless and daft to even think about it, but that doesnt mean there are turbos out there that arent capable, and capable of doing it efficiently. They could even spool up pretty quickly. Modern ball bearing turbos are pretty damn good.

You can just easily have 2 different turbos. One might make ( just numbers plucked from the air ) 10psi with say 50degC air temps, and another 20psi with similar temps. Just depends if its running within the efficient part of its compressor map.
Although boost is totally dependant on how restrictive the engines breathing is too.

As for CR required, all engines seem to vary. Ive put Subaru engines together that will run 30psi on 8.5:1 and and still using sensible amounts of advance on pump fuel.
Cossies also used to run really low CR's to use big boost. They dont seem to these days though. The trend is to run highish CR's and boost.

Is the Minis combustion chamber so bad, that it would need a super low CR to achieve high boosts ?
My own would run 1.5 bar, but it did seem to struggle to hold it once past 6500rpm, although it did stay very close to target. I did try more once or twice, but it just didnt seem to be able to make more. Never looked into why, but possibly exhaust housing too restrictive. I was still running about 24deg static on 7.5:1 CR. Based on that, I'd be sure I could have run more, if I could have made it.
I doubt it was because my compressor was too small, as its fairly big, certainly for a 1300.

There are Starlets out there making incredible power, and also running high boost. They are better engines, but still only 1300ss in many cases.
Highest I seen was a Starlet in NZ, making 345bhp at the wheels with a GT2835 blower. It runs 11's from what I remember, and was still a road car.

I'd say 30psi is very possible with the right turbo. All it needs to do is shift enough air, which is easy.
One way or another fuelling, ignition and intercooling could be sorted to allow the use of 30psi.

But is the engine just not capable of withstanding it ?
Is the exhaust layout ( including factory turbo manifold ) too restrictive ?
Or is the inlet tract simply too restrictive ?

Or is it all of the above 3 things ?

Is anyone using any modern ball bearing turbos ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I have to say i can see exactly what you are getting at and i dont see why a modern turbo charger can achieve the boost figure easily.

But honestly how drivable will it be, i dont know much about garratts GT turbos of other makes or charger

but surely to be effiecent at 30psi and maintain high volume of air movement at say 6500rpm you would be making some serious comprimises at lower boost figure and for normal driving? So would it really be worth it for a boost figure that would in all honesty probably destroy the engine and give the gearbox a real hard time!

Edited by SumpNut on 28th Aug, 2005.

I agree drivetrain and making use of the power are also very important, but was aiming more at the engine, as some seem to think it cant be done.
It may be pointless as you cant make use of the power in most cases though.

Some of the BB turbos have very wide operating ranges, and do spool up pretty fast, and maintain all the way to redline.
They are a bit more expensive, but Im surprised nobody has tried any yet ? or have they ?

or perhaps the benefits of a full BB cartridge on a smaller turbo arent as pronounced as they are with a big turbo ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I am certain people have tried 25 - 30psi+, not myself certainly.

I seem to remember phil melting something at 24psi...

I think turbo tim is running 2bar of boost

Team Racing

I am Jim, but I think I need to change my exhaust turbine housing from what I've been reading, I'm still using the old 0.25ar housing, Its producing too much heat rather than more boost, too ristrictive.
This is my next mod on the turbo

16V project underway

I think that 30psi as a figure is certainly achieveable.

However given the inherent frailties of the A series powerplant, I think that there are better ways of making increased power than to keep on running more and more boost.

Miniwilliams/Giallofly et al have proved that 190-200bhp is possible using 1293 as a basis, for more power than that, I personally would be looking towards a larger capacity engine, maybe using a stroked crank to give increased torque at the expense of high revs, which with the a series three main bearing crank, are better off avoided if we can help it.

Looking back at the high output Cosworths of the early to mid nineties, the way to go was towards a soft turbo approach and larger capacity. The most impressive car I have been in was a 2.4 Cosworth using 12psi of boost, just above standard boost pressure (10psi). Although it was still noticeably turbocharged, the combination of increased capacity, higher CR than on other motors, and less savage transition onto boost, made the power delivery much more linear, and in a RWD car, more useable. This car was built by the Brooklyn Rallyesport dealer in Redditch, who also built the "Pink Panther" Cossies that competed in the British Rally Championship in the early nineties.

I personally see this as the way forward, that is my opinion, but if 30psi is the goal, I am sure it could be made to work.

As Dave mentioned earlier. The goal is not psi, the goal is horsepower. I guess given 3:1 compression, 30psi would be a doddle.....

Thats strange tom I'd go with the other of getting more power...

High revs, more boost, less peak-torque but a huge spread of a wide rev band. This way you exchange revs for torque and so the thing that tears your gearbox apart is reduced.

Ford use a similar idea on their Rally Focus... the output speed is nearly doubled (iirc) as it entres the drive train to reduce the loads on the box and diffs.

Alex

AlexF

Thats the way Ford went, but consider the Peugeot and Citroen method.....

Loads and LOADS of torque, and reputedly only a 4 speed box as the ratios can be that widelt spread due to the torque output.

And look who is cleaning up in the WRC currently....

touche!

I'm still going to try high revs as our gears are like cholate!

Alex

AlexF

Maybe you should change your gears then :)

My gearbox which was helical when I got the car was in very good shape after at least 6 years of abuse on the strip, road and trackdays.

I don't think they are as lousy as we give them credit for :)

nither do I vegard... I run helicals in both of mine... and no real problems...

but I run low power most of the time in the road car and the race one does little mileage...

at 20psi I expect things would be very different,

Alex

AlexF

I would like to try more than 16psi but my turbine housing won't allow me to... 16psi is ample for a sub 14 sec 1/4 in a full-weight mini - if I want to go faster, I can.

I don't really want to go hugely quicker though (although a little more so would be better). My aim is to achieve even more with what I have - ie injection and optimising ignition. Cam timing / duration is another place where I haven't even begun to investigate - I believe backpressure and overlap are pretty critical to each-other, and needs looking into.

As regards 30psi - if anyone wants to do this, fine crack on and do it. I don't see what is so fricking clever about putting together a 7.5:1 CR engine, a stock cam, and a huge turbo, 25 degrees fixed and running the (new) fabled 30psi... That's not to take away from anyone who's done this (RELIABLY) but I'ts not exactly going to set you any record lap or strip times without the aid of laughing gas.

I had an offer on a BB turbo from a contact in R&D at Garrett previously, but the smallest turbine he could put onto this particular core was a 0.64... No thankyou! If I wanted to go the BB way - I understand the S14 core is the place to start, but like I said - there is plenty more power and times to come from other places before then. Never say never, but I'm happy with the response of my smaller turbo - and I'm sure that there is planty of scope within the T2_ stable for 30psi if i was so inclined to seek this as my only target.

Edited by turbodave16v on 29th Aug, 2005.

So why would I want a t2 if you cant run over 16psi? May be enough for you, but is it enough fot others? If you don't want to go much quicker then you probably have a good setup for the road, minamal lag and medioka power. I would rather have a bigger turbo that can take more boost and have anti-lag. Then you got big power no lag no compramise.

At the end of the day, there is no right and wrong, each to their own. You want your car drivable, I want mine quick. You just gotta do wat ya wanna do, simple.

Its only a bit of metal. If it blows it blows!

http://www.putfile.com/mini300bhp

oh - my mistake... My turbine won't allow more than 16psi as it's cracked (I can disconnect the pipe to my actuator and it quits at just under 17psi). Believe me - I can run a lot more boost with my turbo - should I wish (and once i replace that turbine!!!!)LOL!

Edited by SumpNut on 29th Aug, 2005.

Dave,

I read somewhere that Garrett are doing a lot of research into VNT technology for petrol engined turbochargers.

Does your mate in R&D know anything about that?

I believe the problems with VNT on a petrol engine are the high EGT's involved. On diesels its a doddle, as they run much cooler, but petrol isnt so easy, although if they do get them working, it would be a major development.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Variable geometry turbo's for Gasoline (petrol) were first used succesfully by Garrett in the late 80's / early 90's in USA production vehicles, so FAR from brand-new technology...
None of the turbo manufacturers seem to be pursuing this technology for gasoline anymore though - as Stevie says, the extremes of EGT's require very expensive (and exotic) materials. conversley, almost every diesel nowadays has variable geometry. One of these could probably give reasonable results on an a-series - but watch those EGT's!

Someone on here is trying a VNT on their mini - who was it?

Edited by turbodave16v on 29th Aug, 2005.

I think mike is using a vnt turbo, not sure if its running yet

Team Racing

Doesnt blown_imp run a vnt trubo?

I read an article a couple of months back, and it was about Garrett wanting to develop small VNT chargers for small european petrol engines.

I just can't find the link to that page anymore- bloody annoying!

Andy

Edited by Andymini on 29th Aug, 2005.

well said that man