Fuel enrichment

[Joe Craven]

I took my new 77 1.8 Rabbit out to the track and it felt down on power and seemed to run lean as the rpm's neared 6K.

A little background, I race the Rabbit in NASA GTI Cup and the 77 is legal with the GTI spec parts. The shell had been rewired for the newer motor along with the engine computer. The drivetrain is out of 83 GTI which I recently wrecked, hence the new shell. The motor was fairly fresh and a front running motor.

There were a couple of electrical connections that were missing, including the wires to the full throttle switch and the wire connection to the rectangular box on the front of the motor where the braided fuel line runs through. I think that device is a fuel pressure regulator.

I'll be working on the car this week and trying to figure out what's up. Which pins on the computer are the ones which are connected to the fuel throttle switch so I can fab some new lines or perhaps just put in a cockpit switch? Should I be concerned about the other connection to the what I think is a fuel pressure regulator and what does it do?

Thanks

Joe

[This message has been edited by Joe Craven (edited September 16, 2002).]

[Bill Miller]

Joe,

I'm not sure what pins are for the FTE switch, but you can probably find it in the Bentley.

I'm surprised that there's no connection for the control pressure regulator though. All the FI cars from '76 on had them, even if they weren't using the lambda sensor. I'm honestly surprised the car runs right at all w/o this connected. Did you swap the whole harness out of the donor 1.8 car? I'm guessing your '77 was a carb car to begin with.

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MARRS #25 ITB Rabbit GTI
SCCA 279608

[Joe Craven]

I bought the car w/o engine although I know there was a FI 1.8 in it last year. The wiring harness is as delivered and I do not know too much about these VWs. Originally, I didn't have the wire connected to the frequency valve and the motor ran but was a little difficult to start. I went to the junk yard this weekend and got the wiring connectors so I can at least wire them into the computer if this is necessary.

Thanks for your help.
-Joe

[Bill Miller]

Joe,

You really want this stuff working right. I'm not sure what the 'open' fuel pressure is w/o the wiring connected. Ok, just checked the Bentley. The connection is for the electrical heater that prevents the system for operating at excessive fuel pressure for too long when the engine is cold. The purpose of the control pressure regulator is to maintain a constant pressure at the injector nozzle (and presumeable a consistant spray pattern), at variable delivery rates based on the position of the air flow sensor plate. That part of it seems to be a purely mechanical system (at least w/ the early CIS cars).

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MARRS #25 ITB Rabbit GTI
SCCA 279608

[nascarvw]

THE FTE SWITCH IS USED TO TELL THE FREQUENCY VALVE TO INCREASE IT'S DUTY CYCLE.YOU CAN BYPASS THE FTE SWITCH AND PLACE A TOGGLE SWITCH ON THE DASH.JUST LABLE IT PIT/TRACK.THIS WILL TELL THE K-JETRONIC TO GO FROM THE NORMAL 50% DUTY CYCLE TO THE 70% CYCLE.AS FAR AS THE 12 VOLT POWER SUPPLY GOES, (TO THE PRESSURE REGULATOR) JUST RUN A 12 VOLT KEY ON POWER SUPPLY WITH A GROUND AND YOUR ALL SET.YOU MUST TEST BOTH THE CONTROL PRESSURE AND THE SYSTEM PRESSURE TO DETERMINE IF THE SYSTEM IS UP TO SNUFF.IF YOU HAVE QUESTIONS ABOUT THIS SYSTEM STU AT BSI KNOWS THEM WELL.HOPE THIS HELPS.

[Joe Craven]

Thanks guys, I know exactly where to start. The extra connector from the salvage yard will come in handy. Hopefully, I'll find that the FTE wiring isn't already jumpered and that'll be the reason for my lack of top end power.