Bypassing Fuel Cut Mechanically

LegacyT · Post by **LegacyT** » Thu Jan 02, 2003 7:10 pm

I read somewhere on I-club that Fuel cut can be bypassed machanically on a legacy turbo by inserting a one-way check valve between the Map sensor and factory boost soleniod. Anyone done this? What if I have a manual boost controller? How do I hook it up then?

Thanks,
Mark

morgie · Post by **morgie** » Sat Jan 04, 2003 5:55 am

you dont connect that on the hoses of the manual boost controler, you connect that to the hose that goes from your intake manifold into the pressure meter/sensor, situated just over the solenoid.

essentially (according to what i've read from www.autospeed.com .. the site is down for now so i can't do copy/paste), you just insert a "T" in front of the pressure sensor and insert a one-way valve on that extra outlet ...

the OneWay valve is to let the pressure sensor work properly when in "Vacuum", and let the air go out when on boost, so the pressure sensor doesn't see all the pressure.

vrg3 · Post by **vrg3** » Sat Jan 04, 2003 6:24 am

Be careful if you do this -- the ECU has more than one use for the MAP input. It does use it to decide whether or not to cut fuel, but it also relies on the pressure information for closed-loop boost control, for boost-dependent ignition retard, and to richen air/fuel ratio when under boost.

LegacyT · Post by **LegacyT** » Sat Jan 04, 2003 4:55 pm

So you tap the vacuum line that runs from the nipple on the intake manifold to the right hand side of the brown map sensor, right? I have my boost guage tapped onto that line and there's also a vacuum line tee'ed off which goes to the charcoal canister, do I put the one-way check valve between the tee off to the cannister and the map sensor?

Thanks,
Mark,

morgie · Post by **morgie** » Sun Jan 05, 2003 7:17 am

ok, here is the stuff from autospeed.

The easiest and cheapest way of defeating an overboost cut that works on a pressure signal is to drain away some of the pressure via a T-piece and a one-way valve. The one way valve stops air being sucked back into the line on vacuum (and so means that the sensor still measures off-boost signals fine) but still lets air flow out of the line when the car's on boost, reducing the level of boost seen by the sensor. Suitable one-way valves are often found in the emissions plumbing of cars - check wreckers. Total cost should be under a few dollars.

LegacyT · Post by **LegacyT** » Sun Jan 05, 2003 1:31 pm

OK, I figure the brown thing is the map sensor, anf the blue is the boost soleniod but what is the black thing that the line connects to? Any clues. I'm gonna cautiously fiddle around with this stuff when I get my new fuel pump in so that I don't blow the thing up

Thanks,
Mark

morgie · Post by **morgie** » Sun Jan 05, 2003 7:46 pm

I've had a look at this 1-2months ago and... the MAP seems to be the black thing, the brown thing looks more like a electric valve or something... Air comes in , then exits throught the black cylinder or via the other hose...

that's my opinion.. may be wrong

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Bypassing Fuel Cut Mechanically

Bypassing Fuel Cut Mechanically