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

[cyber2213]

Hello everyone ... thank you in advance for the help that you give me ...
I am the owner of a 911 3.0 RSR replica as the original:
Amended RSR 3.0 MFI, high throttle bodies, gears light distribution, Mahle pistons and cylinders (11.3:1 compression), RSR flywheel, pressure plate light, RSR camshafts, oil pump 3.3 turbo heads are 3.2 amended 42 / 43 valves, sports clubs, valve guides Bromo - Beryllium, eilbach valve springs, titanium retainers, 3.0 sc distributor twinPlug amended, ALL THE BEST ...
The problem is that there is a huge gap in power at 4500 rpm ...
How can I do to eliminate this gap in power and torque?
Thanks to al

[john walker's workshop]

you may need to run it on a dyno to duplicate the problem and analyze the results. that stuff takes some time to dial in.

[cyber2213]

on Dyno resul :
28kgm @ 6320rpm
247,2hp @6320rpm
tomorrow i will go on anthor dyno to do another test..and after i pubblic result..

[dicklague]

There is no simple answer with MFI.

You may all this already, so bear with me.

You start by doing the CMA routine. This stands for Check Measure Adjust and is contained in a Bosch MFI manual. there is a PDF of it somewhere on here I believe.

there are a couple of great MFI threads on this site and some research by Pelicanites much more knowledgeable than I am. Read them all. Ask questions, and read more.

Before you do any MFI adjustments, the routine is to make sure the valve adjustment is perfect. Make sure the compression is good. Check and adjust the timing. them move on to the basic settings on the pump and the airscrew adjustments at each stack

Then use a modern AFR instrument such as one of the items sold by our host. With this engine I would install it permanently. You have to install a 18mm bung in the exhaust system for the wideband oxygen sensor. Then start tuning.

I have a 2.7 MFI RS replica and have really gotten it to run well using a Daytona Sensors Wego IV. this unit logs 2 hours of data from the sensor so you can compare RPM and AFR and analyze what is going on.

[I am a bit biased because I sell the Wego IV to Pelican, but would not endorse or sell it if I did not think it was the best value on the AFR market.]

Any good wideband AFR will work, but data logging and RPM measurement are very important. some units some even do MAP.

I had a lean spot between 2800 and 3200 RPM and was able to tune it out with the above process and lots of trial and error.

If you are running on a dyno they should have AFR as part of their instruments. If not they need to be measuring this to set up an MFI system properly.


I am sure you will get lots of good advice here on MFI......there are lots of very knowledgeable MFI people here.

[RWebb]

be sure you have the right space cam

one guy built a MFI dyno - hope you don't need that degree of analysis

[cyber2213]

how can i do valve adjustment???????

[tharbert]

Take a look at this and this.

By the way, I used to live in Comiso. Sicily is a wonderful place.

[Jim Richards]

Originally Posted by cyber2213

3.0 sc distributor twinPlug amended

I wonder how the advance curve of an SC dizzy compares to what's expected for a 3.0RSR engine. Also, have you looked at your timing as you rev the engine up past your flat spot around 4500 rpm?

As RWebb mentioned, do you have the correct space cam in the injection pump for the RSR?

[cyber2213]

i think that valve adjustment is refer to MFI...

[dicklague]

Valve adjustment on engine. Make sure everything in the engine is up to spec including timing and valve adjustment and before adjusting the MFI mixture.

[cyber2213]

[cyber2213]

valve on engine is perfect...10 to intake 15 to ex..

[cyber2213]

???? Pls Help---

[smokintr6]

That dyno graph by itself is not very helpful. You really need to get an Idea of what the air fuel ratio is. Ask the dyno shop to measure and print lambda or air fuel on the chart. It would also very helpful to see a timing curve. Also, you didn't mention any bottom end modifications on that engine... I'm not so sure that I would be pulling it to 8,000 RPM It certainly isn't making more torque above 7200 and it looks like the horsepower is trailing off as well. There's probably no need to run it that hard, especially while you're diagnosing problems much lower in the power band.

-Ryan

[356RS]

I agree with the importance of an accurate air/fuel ratio reading with the dyno chart. I have built/modified a few MFI pumps for RSR spec engines and the challenge always seems to be a very lean area from around 3000 to 4500 engine rpm on the dyno. Not saying this is whats happening with yours. We really need to see some A/F ratios.

[cyber2213]

bottom end modificate:

[cyber2213]

ok i buy wideband tomorrow i install in my car....but i think in 4000-4500 rpm is too rich...and i don't understand why...many thx for help...

[Steve@Rennsport]

Well sir,........it looks like your FI pump needs some fine tuning, but I must say that this is what an RSR-cammed engine looks like,....

Having owned and raced these things, they make no power below 5K. With a properly setup pump, they have a good usable working RPM range between 5K and 8K, which is darned good for a racing engine.

[cyber2213]

for mfi fine tuning can you help me?

[cyber2213]

i don't understant why i have only 28.1kgm and 247.1hp!!!!!!!!