Torque/VE
Turbo Mini Forums

I believe the run that produced more power was actually on less boost

What he ^^^^ said. The logs from the MS confirm it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I have a theory. A little tenuous, but worth a thought.



See how both the GT17 equipped cars, Robert and Ben, peak higher and later. I think that can be attributed to the improved performance of the GT17 over the T series turbos, particularly in the turbine design.

If you look at the others, Mark's is a 1380 and peaks first followed by Ron and Kean. I think that although my 998 hit the rev limiter, it probably had hit peak and was dropping anyway. Bens 998 starts to drop away past 6000rpm as well.

So the theory is that it is a velocity based issue, more than likely on the inlet side.

Do you all use the MT inlet manifold?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Is it not an exhaust side limitation?

You can wind the boost up to get as much in as possible but this
doesn't improve the exhaust situation, at higher speeds the
exhaust isn't properly emptying the cylinder so you get a massive loss in torque?


Nial.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Is this to do with the mis-match in valve sizes, or is it the manifold/turbo restriction?

Do many other heads have the mis-match in valve sizes that the A series has?
Do you get the same problem with an 8 valve head?

If you know you can get all the air in the inlet you need is it worth
leaving that standard and trying to increase the exhaust valve as
much as possible (what are the options here)?


Nial.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Sorry meant 8 port heads.


Nial.

Similar problem with the 8 port heads but it is far more proportionate to boost.

This is the thread containg all the RR graphs from last year. Saves me keep having to search for it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yep I use the metro exhaust manifold and a maniflow exhaust.

im using the metro turbo inlet and ex . then 53mm downpipe. 36/31 valves .
have a look at matts curve paul .hes on a t3 and its a v similar shape to mine..

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

The drop in ve is supposed to be tip/manifold pressure induced.

when you're looking these graph, the gt17 with his special lpt turbine hasn't the grunt of old trubines but is more efficient flow wise, so release more power.

Compare blue torque curve and green one, they're both ending around the same value, various test have shown that pass a certain value,which is around 150/160 bhp turbine wise and around 175 bhp std exhaust manifold wise is just too restrictive and track exhaust gas in the combustion chamber.
Other ones have shown that even with a turbo on his back an a serie like to have around 31° timing to make full power and this can give around 10 bhp, over 27° timing and transfer a 24° timing in an animal.

Then you have nowadays new turbines choices, for a 998 I would use latest borg/ihi mitsu k03, tf/td35 series, which will have low inertia and high flow ( lookt at an s4 turbine wheel)/
exhaust mainfold: a std metty manifold will not restrict your power,but a nicely bent trhee into one should help.An mpi cam to control inlet events easily, highish cr..play a bit with boost to linear your torque curve and you should have it.

hum,

I', just thinking if you retard the ignition 8 deg is it likly to increase the torque at 3000-3500 like in that graph...

I think yes, the the burn/ expansion will be later so when the engine is turning slower the peak pressure is later where the the leverage angle is more, but a lot of the energy is wasted, blah blah blah.... makes sense in my head though...

can you tell i've been dringing again Paul!

could it be the speed of the burn staying the same but the time to extract the useable power is halfed (say 3k to 6k)

advancing the ignition as the revs rise would gain torque as more is burnt by the time the exhaust opens? Or moree burnt by half stroke..higher pressure

Yes i moved to the darkside

Instagram @jdm_brett

Intercooler efficiency?
Raised IAT/ACT's or whatever you want to call it

Just thinking about manifolds.

If you plonked any of the turbo manifolds we use on an NA engine you'd expect a drop in power compared to an LCB, so there is some restriction.

However, in our case, there is a further restriction beyond the manifold in the shape of a turbo, so the manifold is not the most restrictive part of the exhaust system. so in my eyes any improvements you make to the manifold will be pointless as you still end up at the same restriction.

At the top end of the rev range the waste gate will be open, can these be made more efficient?

I think Pauls comment on the efficiency of the 17 turbine is relavent.

My personal opinion is that some of the graphs above show reasonably well optimised engines with minimal drop off in torque and way better than an NA motor.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Edited by Paul S on 1st Oct, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

OT but where did you get your GT17 from Paul? What was the pricing like?

If something is worth doing, it's worth doing half of.

Well, results on the rollers at the weeknd for the Sprint might be interesting then as it has a non-metro manifold. also I run the 266 cam.

I'm sure Steve squeezed 29mm ex valves in my 295 with inserts.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

ebay. M5 Saab Centre. £350 plus postage. Just a one-off I think.

Best price I've seen recently for a new genuine Garrett. Confirmed by seller as such in writing. We will see.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Cheers Paul.

TBH I will prob stick with the delivery mile GT20 I have. However I have been so impressed with the GT17 figures that I have found my interests wandering.

If something is worth doing, it's worth doing half of.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Well If I blow the head gasket tomorrow you'll be able to have a good look!!!

Otherwise Steve is the man to comment

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Not sure that the 29mm exhaust valve will gain much over the 26.5 due to the shrouding. The gap between the chamber wall and valve gets very restrictive, with a lot less area than the curtain wall.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."