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5kCSTQ - Free Horsepower (almost)
An update on my 5kCSTQ boost improvement project ...
You may remember I said something about getting some stronger
wastegate springs wound a few weeks back. I had a dozen of these
springs wound at a local spring shop - the setup charge was such
that one spring would have cost me about $50, while getting a
dozen wound cost me $110. The answer was clear, have them do a
The results after playing around a bit: the car now runs 1.6 bar
on the dash readout, and about 11 PSI on a guage with the new spring
installed without any extra shims.
To get it to do this also takes an extra ground wire that I'll describe
for you. Earlier I mentioned that the ECU cut off the fuel pump whenever
it saw about 1.5 bar on the readout. It turns out that what the ECU is
controlling is the ground for the fuel pump relay. On my '86, this is
terminal 47 on the relay board and pin "T" on the fuel pump relay. at
the multi-pin connector on the ECU this is terminal 21 ... which if you
are like me you won't be able to figure out which wire this really is
since nothing is marked at the ECU connector. The wire you want at the
ECU connector is brown with a green stripe and is third from the end of
the connector. You should be able to check this with an Ohm meter
when the fuel pump relay is out of it's socket on the relay board,
you will see "0" Ohms between terminal 47 on the relay board and the
wire terminal on the ECU plug.
Providing a ground to this wire keeps the ECU from cutting the fuel pump
when the ECU thinks it sees overboost. I'm going to rig this up through
something that only grounds the wire when the engine is running, so that
the pump will shut off if the engine quits.
Putting a 4mm shim under the spring base in the wastegate cap gives
a reading of 1.7 bar on the dash, and about 13 PSI on the guage. I'm
still experimenting, and will ramble on at some length later.
Needless to say, the car runs a *whole lot* better <<!>>
Anybody interested in one of these springs, I'd like $15 and I'll pay
the postage in the US. Email me your address and I'll ship you one.
Charlie Smith firstname.lastname@example.org 614-471-1418
Columbus, Ohio USA
4 wheeled fleet: 2 wheeled fleet:
86 5kCSTQ 92 Ducati 851SP 851cc
69 Porsche 911S 3,200cc 95 BMW R100-RT 1,000cc
81 VW Diesel Pickup 62 BMW R27 250cc