FI Problems/considering Weber Options

[Chuckster]

I have been a long time lurker at Rennlist but there is very little discussion on teeners. I think I have found a home for 914 discussion. I would like to thank Geoff for turning me on to your BBS.

This a 914 2L that I hope to use for ITA. The engine is stock and needs to remain stock to keep me legal for SCCA. I realize Webers are technically not legal.

I posted on Rennlist a discussion on switching to Webers. I will just re-post here my FI problems:

The car is leaning out at higher RPMS. I have changed the FI harness, computer, new TPS, put in new injectors. Have put in a known good atmosphere meter. The head temp sensor is on variable resistor so I can fine tune the air-fuel mixture. I have disconnected this and inserted a resistor substitution box. At idle and the resistor box set at say 200ohms the car runs fine. Under heavy load the car begins to get leaning out popping and also begins to miss. When I put in high resistance (2000 ohms) the car runs very rich at idle and under load runs strong, no missing up to about 5000rpm.
5000rpm is my redline so I dont care if it misses at higher than 5000rpms.

I have had lots of help on all these diagnostic tricks including changing the trigger points checked the fuel pressure it is steady if a bit low (29.5psi) through heavy load.

I and others have torn this thing apart so many times, I cant remember if I have checked some simpler things such as the little injector rings at the head. This very well could be the problem. But honestly cant think of anything else to do or check.

I have access to a test carb. off of a '70 914 and will try that. If this fixes the problem, I will put the carbs on. Something my sister thought of which was a crimp in the fuel line. I suppose we could have good pressure and not enough volume.(?)

I do appreciate the input. Any thoughts or experiences would be great. Someone else mentioned the duel 40's. Which does seem to be the set-up.

Thanks again for the suggestions.

Chuckster

[Chuckster]

Thanks again Geoff for turning me to the 914club.

I have been reading all the interesting discussions on this BBS. Great forum!!!

As I understand what adjusts the A/F at idle is the knob on the ECU. Which is the stock ECU for a '74 2L. The CHT is what tells the ECU what temp the motor is and if cold, sends high resistance that richens the mixture through out the RPM range. Generally full rich is around 400ohms. Forcing it read even higher resistance riches the mixture even more.

The MPS is also stock and I replaced with a known good one. The result was no change in the lean popping problem.

This motor is dead stock no special valve springs and I dont run it past 5000rpm. The lean popping seems to happen under load only. If I rev the motor to 5000rpm no problem. Until I put it in gear and accelerate.

Now adjusting the MPS is something I have not consider. What can I do there.

Jeff I will read very carefully this test chart.

I really do appreciate the input. This is a very well informed BBS.

Thanks again everyone.

Chuckster