3.0 CIS Kjetronic fuel distributor upgrade / more fuel

[florent78]

Hi

I rebuild my engine with a more powerfull setup
high compression piston
schrick camshafts
twin plug
etc ....

my tuner is working on the engine to try t get the max from the CIS
please ... I know later I can achieve much more with PMO or EFI ;-)


this tuner is works for years on rally engine with carbs and pmo (not only 911)

regarding the AFR, we need some more fuel to get better performance

testing with the WUR adjustment and pressure control on the head have been done, but results are not good

so we are looking a way to give more fuel to the engine


is it possible to rebuild the fuel distributeur and adjust it to deliver 10% or 20% more fuel ?

any reputable company to do this ??


I will appreciate your help and feedback

thanks
Florent

[turbobrat930]

Send Brian Bodart (Rarly8 on these forums) a PM. He is the 930 CIS goto guy. And if he can not help you, chances are, he will know who to send you to.

[Trackrash]

This has been discussed. Not sure if it was here or on Rinnlist. I guess it was so long ago that it doesn't show up in a search. Hopefully one of the moderators will know.

[florent78]

I find a local tuner focused only on Bosch Kjet L jet etc ... upgrade

my tuner had a long discussion
he seems to know what he's doing and good reputation

they validate together the increase (10-12 %)

the guy will do a chart before and after so we can check

and the AFR / lambda will be the final judge


we are currently at 235 HP

and the car can gives more ... but need more fuel

I will tell you

[Walt Fricke]

You can deliver more fuel by raising the system pressure by adding shims to the regulator in the FD. You can deliver more fuel by adjusting the mixture screw, though you have to be careful not to make it so rich at idle too that it won't idle adequately.

You can lower the warm control pressure in the WUR by raising the big plug so the FD presents less pressure countering the rise of the fuel plunger to the slots.

The six differential pressure diaphragms can be adjusted with their adjustment screws, though usually one only adjusts them so each fuel injector discharges at the same rate as its brothers and sisters.

I have trouble envisioning anything you could do directly to the FD, like making some passages larger or something, which would be at all practical.

[florent78]

My tuner already tried to "play" with those parameters

but if go on the full charge direction
after idle and warm up is not good any more

he works on Kjet since many years so the only option available in my case is to increase the full charge fuel delivery

for information they push until 5.2 bars but no significative improvement

my head is rebuild this week

next week I expect first results


we will see

[infraredcalvin]

No personal experience, but these guys are mentioned in the forum often for mods:

CIS Flowtech - Rebuilding Bosch Fuel Distributors & Warm-Up Regulators

[JFairman]

The only good thing about CIS fuel heads is they fit in your hand so you can see how far you can throw one of the miserable things...

yeah, I've hated bosch CIS since the first time I saw it and had to waste time and money buying special tools and screwing with it over 30 years ago in BMW's... and they only get worse.

[florent78]

the guy did not upgrade the piston

he check the distributor
good state
not leaking
no rust inside

my distributor can be set up
so initial result
105 ml per injector

final result 130ml per injector


my tuner will test it and we will see if it's enough for the lambda or if we need to do a hardware mod to increase de quantity

we will see next week

[JFairman]

Your guy doesn't have a machine set up to enlarge the tiny fuel plenum chamber around the metering slits in the control plunger cylinder or the 6 orifices above the diaphragm or the experience that goes with figuring that out.
Larry Fletcher of CIS Flowtech does so just send it to him or enjoy chasing your tail in endless circles and paying your guys meal ticket till your broke and dizzy.

[florent78]

Sorry you are wrong

He was just able to achieve the increase the tuner asked for without modifying the cylinder

I pay 100 dollar for the full set up plus wur
And calibration

If it s not enough
He can do the modification

Again
Everything is checked with values and afr

So it s definitly not the amateur world