Engine Simulation Software
Turbo Mini Forums

I've been playing with some very interesting software.

Here is a video with a contribution from Vizard.

http://www.worlddragracing.com/downloads/U...TBHP_F_800.html

I've simulated the 998Ti engine. I have confidence in the results as the torque curve generated by the software has that very strange plateau that my engine exhibits. I now know what causes it :)

Here are the results at 6000rpm.





You can clearly see the impact of the charge robbing and also problems with the siamese exhaust port that causes the poor VE on the inner cylinders. Most notably, the VE of the outer cylinders is in the region of 10% higher than the inner cylinders. This is caused by charge robbing, even with a moderate cam, and the exhaust pulses in the siamese centre port.

Now we know the problems, in theory, we can work to overcome them.

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."

so im guessing with this, you could change cam specs etc and see how it effects the charge robbing and maybe find away to reduce/overcome it?

Why is the exhaust pressure dropping so much with both valves closed in the centre port compared to the outer ones?

Is this is looking at port flow or valve flow?

If port flow, it'd be nice to see two exhaust pulses on the bottom one, I think? Edited this bit

Edited by wil_h on 19th Jan, 2011.

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

The centre siamese port together with the short length of manifold runner to the turbo causes a shock wave on this particular engine.

Each of the above graphs represents pressure and flow at the valve of one cylinder. Inner and outer cylinders exhibit very similar characteristics.

So I took the model, added a modified head, scatter cam, GT17, better intercooler and then played with manifold runner lengths.

These are work in progress but so far I've found another 30hp from the same boost.





On the outer cylinders I now have higher inlet pressure than exhaust. On the inners they are closer. Charge robbing is still happening though.

Now the contentious bit :) VE on the inners is 95%, on the outers it is 105% !!!!! Simply by tuning runner lengths to get the peak of the inlet pressure wave to coincide with the trough of the exhaust pressure wave.

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 wish my brain wasn't so feeble!

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

So, how does you current 'in-progress' manifold fair?

Interesting to say the least. What happens to the power/torque when not a peak power? as I presume that the pulses only work for 'resonant' rpms and you have tuned for 6krpm and presumably harmonics therof.

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

The above is for the in-progress manifold. I got the highest hp figures with the turbo in front of the grill! I've had to compromise a little by placing the turbo by the head, but I can see gains at around 4k to 6k. Peak was at 7.5k, now it is at 7k.

Surprsingly the torque is not at all peaky. Peak torque is at 5000rpm.



All purely theoretical of course.

Edited by Paul S on 19th Jan, 2011.

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."

Interesting comparsion of VE on the inner and outer cylinders after optimising the inlet and exhaust manifold runner length on the 1293 with the Pierce head, GT2056, Ph2 ish cam etc.



It seems to be difficult to overcome the charge robbing and the effects of the siamese exhaust port on the inner cylinders. However, overall, it's flowing nearly 30 lb/min at 8k.

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."

that graph looks very similar to a graph about manifold lengths i was reading last night...

What about a twin scroll turbine housing and use it to separate the exhaust manifold tubes ?
Feed 1+4 into one side and 2+3 into the other ?

They are starting to become available in smaller units now.

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

to elaborate on my comment above,

below is what I was refering to, its a test for intake lengths, but from what I have read should have similar results as variations in exhaust runner length,

Thats very interesting.

It confirms, to some extent that the Area/Length ratio determines the shape of the power curve. The A/L ratio is the significant variable in the Helmholtz equation.

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."

Sooo,

what happened when you simulated with exhausts longer than your long optimal front bumper length? did the VE start to drop again,

Improve a little at the bottom end but dropped away drastically at the top.

In fact on the 1293 with the big turbo, head and cam, the optimum length is up by the head. I could gain a couple of bananas by increasing the diameter of the centre pipe by a few millimetres.

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 with you on this one.

All very clever stuff lads!

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

Would anyone like to know the difference in average exhaust gas temperature on the outer and centre ports on a simulated high spec NA 5 port engine?

Contentious, so if you don't want to know, I will keep it to myself.

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."

Go on then. I kind of understand what you are illustrating, so it would certainly be interesting. I think it's only contentious to you though...

Go on then Paul.

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

That's very interesting!!!

and that's pull my gutts...

So is this soft ok to modulate a 5 porter?

It seem so,then the information given here have gold value, is there is a trial version as engine analizer pro from perf trend?

You pick up my interest, that's long time we didn't have a so good post in TM.

Thanks Paul!...again guttss...

120 deg c

Joe, that's close.

129.6 Deg C.

Fab,

Thanks, glad you appreciate it.

The software that I use is OEM and not in the public domain, but there are similar available.

Edited by Paul S on 26th Jan, 2011.

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."

It seems that once you know the difference in temps between the exhaust ports for a known configuration they track by a similar amount for the same chamnge in AFR.

the centre exhaust runner is 129 deg c hotter than the outers?

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

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 need to get my head round this and how the thermocouple would work in practice. Frequency response of the probe etc.

What is the maximum seen in inner and outers. Do you have a graph of how they vary through the cycle?

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