6000 rpm +
Turbo Mini Forums

Totally agree with minster.
It's always a big compromise though...

Exactly, its all a compromise and finding what works best takes hours of practical tests, that why Visard spent years researching what works and what doesn't.
phil,
oh and Dave that 3.2 diff you sold me a while back is going great
cheers

so what do we recomend for a turbo, can we adapt things to fit. or remogage the house buy a turbo

follow tried and tested routes...

Avonbar phase 2 / MED T3 cam, modifed head with larger chambers, 1.5 rockers, decent intercooler, sc/cr gearbox, 3.44 / 3.6 diff and you'll be running low 14's all day after a bit of practice!

Sadly Vizard's work is all very old and he didnt do very much work on turbo engines.

Alex

AlexF

didn't say he did, I'm just saying it takes time trying different things to find what works best. just used him as an example.

Read any turbo books and do any research and they will tell you the simple basics of choosing cams and all that

NOt being funny here, but I worked with engine design and turbo selection... so I've read a fair few books. I am familiar with manifold or back pressure.

But I don't agree with what your saying.

If you utilise a turbine housing with a larger area/radius ratio, in order to combat an increase in lag and reduction in response, its essential to decrease overlap. This doesnt mean you necessarily have to reduce the cam duration but as with all factors everything has a knock on effect.

At the end of the day duration is not the issue, overlap is. Even if you ignor the poor responce and poor emmissions from large over lap witth turbos, you are still waisting charge and reducing the charge density...

or you could think of this in terms Compression Ratios, Over lap reduces your CR, which can both be a benifit or a problem depending on what your Static Compression Ration is set to.


Alex

AlexF

overlap reduces your CR? how? the effective compression ratio is affected by the closing of the inlet valve on the compression ratio. Yes you can use this to effectively lower or raise the effect CR.
do you mean its effected buy the amount of charge that enteres the cylinder, effected by the opening of the exhaust valve during the overlap period

I'm not being funny either its just that this is what I have been taught and learnt over the years

"If you utilise a turbine housing with a larger area/radius ratio, in order to combat an increase in lag and reduction in response, its essential to decrease overlap"

Not always...

Anyway, 'lag' isn't just a factor of the turbine, but the volume of the compressor to valve volume, compressor used, etc, and i believe should also encompass the intertia of the shaft assy aswell...

In reality though, i think you two are talking about the same thing, but in a different language to each other!

Crack a can and we'll discuss at Avon...

Edited by turbodave16v on 9th Jul, 2004.

largeror smaller tubine, larger or smaller compresor, we still dont no what the the answer is, or do we, in the pursuit looking for more power, enjoyment????????? i dont want to spend my hard earned cash on hybryd turbo, so whats the answer, KISS ? keep it simple stupid

The answer depends on what you want... more power will always need a bigger turbo, a t3 flows more air for the same psi than a t2...

but for road use a t2 is a far better match than the t3!

The ideal would probably be a t25 hybrid... but no one has tested one of those!

Alex

AlexF

So you are saying that a 60 trim T2 does not not flow more air than a 40 trim T3?

I'm not so sure...

I cant find my t2 comp maps...

I'll keep looking and get back to you with figures on that :)

Alex

AlexF

Don't worry about it, was only trying to promote a response (it was the 1664 typing not me!!!)

I can't be arsed looking at the maps, but know the 60 trim T2 is on the 1800cc Nissan Bluebird - an engine that needs a greater flow than the 1300 metro with it's 40 trim... Metro runs 7 psi, the Nissan ran 8psi as i recall... Pretty similar (neither intercooled) aside from the engine dispalcement...

my understanding of makeing the engine to rev, is suficent air, corect fuel mixture. proper ignition. no valve bounce, as i have a decent cylinder head, phase 2 cam, valve springs good enough 8200, std turbo distributor good nick, but is the turbo holding it back

No the turbo will not limit the engines power range. Just like a naturally aspirated engine to raise the power you need to improve the breathing of the engine, I.e. cams and head work.

raise the maximum power engine speed should i say!

so can we say were making progress, ?

is a standard turbo distributor ok for high revs high bost

Yeah, you'd have to limit the maximum advance depending on how much boost you run, you require roughly 1 degree less advance for every 1 psi more boost.

going have to think about this a bit more, cheers minster

The distributer is easy to modify, I think in order to raise the useful power band though you'd need quite a sporty cam. As per a NA engine

I'm not overly convinced you need 'as much' cam for a given max power rpm (compared to a nat-asp) though...

When i get my dyno i'm going to figure all this out!

LOL wanna go halves on one Dave?

Alex

AlexF

You will need the same spec head cams etc as you would for a naturally aspirated (within reason!) As max torque is reached when the head etc becomes a restriction, with or without boost.

I ran mine on the rollers with and without a turbo and it produced virtually identical power curves save for the turbo engine being 40 bhp higher up.

Max torque 5000rpm, max power 6900rpm same for both turbo and naturally aspirated.