Black Arrow

I`ve installed the LR fuel rail. After the install, I got a pulsating, knocking sound inside the car. The sound follows the rpm, but goes away around and over 3000rpm and goes away when fuel cut is activated, though its very high at idle. It had to be fuel related! I checked the fuel-pipes that goes under the car (from the fueltank to the fuelrail) and the problem is that the LR fuelrail creates a hard pulsating stream of fuel in the 10mm fuelpipe. The pulses in the fuelpipe is actually so hard that the pipe is knocking at the chassis, some place the fuelpipe is laying close to the chassis. This is making a high irritating knocking sound inside the car.
I quess I always could find out where the pipe is knocking at the chassis, but should it be like this? Should it be that much pulsating fuel in the fuelpipe? If I crab the pipe with my fingers, I can easily feel the pulsating fuel. Very good indeed.
Can this harm anything, is there something wrong with the LR fuelrail or is this like it should be and I just need to make some clearance between the chassis and the fuelpipes?

Thanx! (and sorry my bad english writing..)
Thomas

pikey7

apparently it does do that. I just fitted one myself and have the same thing.

There is a thread somewhere on either the turbo board, or the main 944 board where someone (Ski?) isolated as many points where it was knocking as possible. I think that's the only fix though.

Black Arrow

Thanx! Found the link to the thread!

ehall

Glad you found it. I have read a good deal about this being a normal condition in their fuel rail. Do you guys remember or know why?

NZ951

I know SFR was looking at making a billet fuel rail, I wonder if he has any ideas about the noises. It seems most everyone has this problem with the LR one.

Black Arrow

Tim doesnt even reply on my emails, so I dont think I`ll try to get some info from him about it. Maybee you can?
Anyway, its just some minor mod with the LR fuel rail to get the knocking sound away. Got a long and good email from Dave@LR on what to do about it.

Ski

Several things help in making the noise;

The Marren damper is not really a damper as the fuel does not hit a diaphram before it exits the rail, therefore you are prone to pass on the fuel vibration from the opening and closing of the injector at low rpm. This leads to the second phase of the noise, the pulses by the fuel pump, which will transmitt a bit of that noise IF the feed or return line have any contact with the body.

You can reduce these by installing the rubber hose that Dave offers and checking the hard line back to the fuel pump for body contact. The previous changes will reduce the noise up to 35-50% depending on the size of injectors. My 65's were louder than jwl 52's. He rigged up the old damper in the fender well and his car is silent. I did the above changes; you can hear it in the garage, windows up but if you just barely turn up the stereo or windows down outside, it's gone. Also, when driving the car, it now seems to go away before 2000 rpm.

I put a laser temp gauge on the old rail vs LR rail - the fuel is about 15-18° cooler with the LR rail, just a tid bit of info. HTH anyone

pikey7

And it said.......?
TIA!

Black Arrow

Almost the same that Ski mentioned, and added with some others things to do:

1. check the fuel lines. get the steel line away from the chassis.
2. get some small o-rings that fit over the end of the fuel injector. there could be metal on metal contact where the injector is sitting in the intake. that can give a knocking sound.
3. depending on how the inlet line is positioned can make a difference. Try loosening
the front "U" connection at the rail inlet, and clock it differently, a more relaxed position, then tighten.

Thats in short terms what he said

Havent realy found my knocking-spot yet though...! Its knocking like H***, but nothing I do is doing any good Will search more tomorrow!

pikey7

Good man. I'm gonna live with mine for the time being (it makes a conversation point!), but it's good to know if I change my mind!