new reader: L-jet problems - help wanted.

[gofast at ix.netcom.com]

Hi guys - I'm new to this list. I've been going through the archives to see 
if I can find solutions. Seems like a lot of the topics have been hit on 
before. I've been hounding the BMW digest for help, and it looks like this 
is the right place.

Here's everything I know so far. Prepare for core dump...

* I have a '77 BMW 530i that I've been trying to debug with the following:

Engine: rebuilt engine, higher compression than stock (9:5 vs 8.5), 733i 
cam, ported and polished, 30k miles, fresh valve job

Injectors: newly replaced w/ stock injectors- 0.280.150.151

Ignition: Allison XR 700 (replaced points)

New fuel filter.

All gaskets on intake replaced.

Air flow meter: stock meter, bought used, with, I'm sure, a loose/loosened 
spring.

Also have a "new" rebuilt Python airflow meter with the number scratched 
out, so I cant be sure what it is. However, using this makes the car miss 
more than using my older unit.

Timing: set at 1700 rpm.

TPS: I think I set it correctly - top 2 pins close at idle, bottom 2 close  
when idle pins open (load).

I dont have easy access to a professional exhaust analyzer. I might rent one 
this weekend, and want to try and understand as much as I can beforehand.

* Here are the problems and thoughts:

a) With 87 octane fuel, pings at high rpm. Does not ping with 93 octane.
b) AFM all the way lean (screw all the way out)- gives 1.5%-2% CO, too much 
HC - cant pass emmissions.
c) at rpms above 5000, with 93 octane, seems to hesitate (running out of 
fuel?)
d) idle has some kind of miss.

One mechanic has suggested retarding timing to solve a, which will also 
solve b - reduce HC. Another has suggested more advance to reduce HC.
I'm giving up on mechanics...

- Tried more advance last night - still hesitates at higher rpm.

- proffa.cc.tut.fi suggests, in talking about the AFM and injection period, 
that 'if you loosen the spring too much, the flap will be at maximum 
prematurely and the engine will run lean at any higher airflow levels'.  

This might be my problem.

BTW, Have not measured fuel pressure as yet.

Questions:
* How can I set my AFM spring back to stock settings? Is there any 
systematic way that I can measure voltage or something?

* The Bosch fuel injection handbook talks about a rising rate fuel pressure 
regulator as being an l-jet solution. Any cheap sources for one? Pegasus 
Racing Supplies has one (MicroDynamics) 2:1 rate for $300! Any cars come 
with one as stock that I can go to a dealer and get cheaper?

* A number of people recommend adjustable FI regulators. The racing cata 
logs only mention ones for carburated applications. Any thoughts?

* Someone suggested disconnecting the spade connector in the glove 
compartment as an upgrade. This has to do with high altitude usage. What is 
this doing? Which is normal - connected or disconnected?

* My temp guage flickers a bit, once in a while. Is this affecting the ECM's 
calculations? Should I change the water temp sensor?

Thanks in advance.


Samir Shah
gofast at ix.netcom.com
Stamford, CT