Big Problem!!! help me..PLS!!

[cyber2213]

The valves are set at .10 (with the tool porsche)
The distributor (dual spark) is set to 28 ° @ 6000rpm
The spark plugs are those of the turbo (because colder)
The gas is 115 octane

italian:


Le valvole sono regolata a .10 (con lo strumento porsche)
Lo spinterogeno ( a doppia accen) è regolato 28°@6000rpm
Le candele di accen sono quelle del turbo (perche piu fredde)
La benzina è a 115 ottani

[cyber2213]

After the final results to the dyno I'm really desperate ..

[cyber2213]

ok.MFI pump adjusted to perfection --- 15 ° Btcd the 4th cylinder
Tomorrow another test on DYNO
After the test will publish the result ..

[cyber2213]

Dyno FAIL...
A/F result
1000rpm 10.2
2000rpm 10.8
3000rpm 11
4000rpm <10
4500rpm <10
5000rpm 11.8
6000rpm 12.5
7000rpm 13.5
8000rpm 15

[cyber2213]

Friends..i need help...

if i advance or retard MFI what changes?????

[Flieger]

If you advance it, it will likely get a little richer on top. You want midrange, though.

The flat spot and rich spot in the middle is a combination of cam profile, valve timing, and exhaust tuning.

RSRs are about the top-end performance.

[cyber2213]

yes but it's too rich at 4500 rpm
why exhaust

[Flieger]

"Tuned" exhausts are designed to make more power by using the pulses of exhaust gas to "suck" exhaust gas out of a different cylinder which fires next. This is easy to achieve on a Porsche flat six. The issue with tuning is that it is a resonant frequency technique. The designer will make it "scavenge" at a particular rpm value. The trade off is that at certain frequencies there will be LESS power than a "normal" exhaust. It is a node/anti-node wave interference pattern. Stock exhausts often trade some restriction and top-end horsepower for a smoother, flatter power/torque curve.

Again, your RSR engine was intended by Porsche to be circuit-raced and live at 8000rpm or more all the time. They made the cam timing and exhaust tuned to work best at these rpms for the most top-end horsepower. In doing this they gave up lower speed horsepower- below 5000rpm probably.

When the "scavenging" is working, it pulls more air through the engine. The mixture goes lean. When it is working against you (at 4500rpm), the new, clean air cannot get into the cylinder. The mixture goes rich. The Porsche engineers designed the "space cam" in the MFI pump to give more or less fuel to make the mixture right at all these places.

Sorry for no Italian, maybe you can copy and paste to Google for translation.

If you are using "RSR spec" everything, then these midrange flat spots sound normal. You will need to deviate from "RSR spec" to get midrange power. If you do that, you will lose top-end horsepower.

The only way to have power everywhere is to have adjusable turbocharger boost and variable valve timing, like the 997GT2 for instance.

Best Regards,

~Max

[cyber2213]

then the cams del'RSR have no progression?
my problem is very big ...
in fourth gear my car can not exceed 4000-5000 rpm step
is not a question of power and the question of giving a certain progression to the car ..
I hope I was clear in explaining'm Italian and is technically difficult to explain in English ...
Rigraziamento all for your enormous availability ....

[Flieger]

RSRs would typically shift just after there power band- maybe 8400 rpm? That is why you need very short, close ratio gears. You should be in third gear at that spot, then the rpms would be higher. Sorry.

See how they keep the revs high: YouTube - Onboard Kremer Samson Porsche 911 RSR

[Flieger]

Can you post the dynop power/torque chart? How bad is the flat spot. You should be able to tune *some* midrange back in so that it is not a complete dog.

911E cams, small intake ports, low throttle bodies, different exhaust are the way to go for low rpm power.

[Flieger]

OK, I see you did post those earlier. I am getting confused with all these threads about the same issue.

I only have the theoretical knowledge. I have not worked on these very exotic cars. You will need someone like Grady Clay or Steve @ Rennsport or Henry Schmidt @ Supertech to help you.

[cyber2213]

Very bad...

[jeffc280sl]

This is a very long and informative post about MFI internal adjustments. It discusses in detail the purpose of the white and black screw adjustments that set the read location for the stylus on the 3D space cam.

I read where you adjusted the MFI timing. Have you adjusted the white and black screws inside the MFI pump?


MFI Pump - Open Heart Surgery

[Flieger]

CAUTION!

Read all the threads about MFI first. Make sure you understand what Jeff Higgins was doing in that thread.

Jeff has a 3.0 with MFI but the cams are set custom for midrange power. He also has a T space cam and pump. That is why he had to adjust the screws to read a different part of the space cam in order to get enough fuel.

Cyber has correct RSR MFI parts- space cam and valve cams. The parts are also very new so there is no wear. He should NOT have to adjust the screws if they were set to the factory RSR settings by his pump rebuilder.

The times you need to adjust the screws are when you are deviating from Porsche's specs. If everything is RSR, he should be fine.

[Flieger]

Here is the proper power curve from Fere's Porsche 911 Story

[Flieger]

Looks like you are missing about 60hp in the midrange. Is your dyno chart from a chassis dyno? What drivetrain loss factor did they apply?

Notice that they did not even bother recording the power below 4500 rpm.

The full 330 horsepower was recorded with slide-valve throttles. With butterflies, it made 315 horsepower and less torque.

[cyber2213]

if you adjust the phased MFI of 360 °????
What happens??

[356RS]

Nothing. Your back to the original timing mark again after 360 degrees on the pump.

[Flieger]

Here is the thread on the engine forum, just to get everyone on the same page.

Porsche RSR MFI regolation