Torque/VE
Turbo Mini Forums

Right,

I'm trying to get a flat torque curve on the next version of the 998Ti. If possible all the way up to 7500rpm.

This curve shows typical 1275 turbo torque characteristics:



(Thanks to legrandfromage for this)

What do we think is causing the torque to drop off so quick? I believe that they are all cammed for peak torque at higher revs.

Is it due to turbo back pressure, wrong cam, cylinder head? Or is it something else?

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."

poor boost control paul in mine..

have a look at my curve on 12 psi 167 bhp...the boost was much more stable.

pop up the boost curves as well ..in fact the sot rating is a better rep of the real curve eff wise..

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

Here is the corresponding boost curve:



I can see what you mean.

This is my torque curve. Despite being lower, it's pretty flat until the rev limiter comes in.



and the associated boost curve:



Curves courtesy of Robert.

I think that there is more to it than just boost control.

Edited by Paul S on 28th Sep, 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."

Could it be sorted fuelling? whether it be Fuel Injection or clever use of the choke?

Could be. All the 1275s were getting richer as the revs went up.

But the drop in torque is so drastic. It you take Ron's torque as being representative of the bunch, torque drop from 175 to 100 with only a drop of 1350 to 1200 in MAP.

Fueling may account for some of it, but I think it is more to do with a drop in VE.

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."

heres my 12 psi run ,see how the torque curve follows the boost a bit ..




the torque drop off on engines where the boost stayed level , can be due to a multitude of factors .

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

Mine was dropping off due to turbine back pressure.

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."

better one




i think mine was getting leaner wasnt it ?

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

I think the TT is looking pretty flat, the only reason it suddenly falls away is the rev limiter. Holds boost too.

Maybe a 266 would help a bit towards the limit as the MG cam has reached its peak.

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

Is this the correct lambda curve?



Looks pretty flat to me.

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."

Edited by robert on 28th Sep, 2010.

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

On 28th Sep, 2010 Paul S said:
Is this the correct lambda curve?



Looks pretty flat to me.

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

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."

Its almost like the dynamics of the turbo need to change throughout the rev range.

yes but ... you can have a stonking big valve head , ideal cam to suit ,then run a r5 t2 and have it all nose dive at 5 k ,the turbo can definately do it in ,just as well as anything else .

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

Naive solution :
modulate boost à la Metro turbo to get you flat curve ?

like 12psi setting up to 4,5K, then 15 up to 5,5 and so on.

But maybe you will have trouble finding a turbo that boosts early and can get up to very high boost

Edited by Advantage on 28th Sep, 2010.

Rusty by nature

i think the trq graph is a bit misleading ,ill make a zero scale one ..

here we go ..

Edited by robert on 28th Sep, 2010.

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

a flat boost control limit will still show the characteristic curve of the cam, so increase/ decrease boost to flatten out the torque curve.

3d boost control is helpful

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

My engine on that day was running rich through the whole range as it was low on boost due to a pikey boost control!

My engine also had a standard head only fettled to lower the compression.

Ron

On 28th Sep, 2010 sturgeo said:

On 28th Sep, 2010 Advantage said:

So if you don't want your torque to drop, let your boost go up

Hmm, bit of a hijack but I like the sound of that, would it work?
With ebc you could increase the boost under certain loads, therefore not increasing torque (aka kill std gearbox) but just keeping the level up to get the flatish curve all the way to the red line...

Edited by Paul S on 28th Sep, 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."

Sturgeo, you have been quick !

I edited this because I thought I was being pedantic !

Rusty by nature

=Paul S,28th Sep, 2010


EDIT: 8 degrees more advanced pushed up the whole curve, so is ignition that significant?

Edited by robert on 29th Sep, 2010.

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