Fuel Cut Defender For 7mgte ????

[spastic 7mgte]

hEY GANG

Ive just bought a new FCD for the 7mgte, does anyone have any idea on how,what and where to wire this thing up. Everytime I try and boost her up a little, the Fuel Cut Off kicks in - Ive just gotta get this FCD to work !! Any tips would be much appreciated !!!! Thanks

[suprra_girl]

what sort of fcd did you get? hks, greddy etc?

http://supra.co.nz/fcd.htm

[lethalwithasupra]

does a fcd remove the top speed fuel cut thing or does it just let you run more boost out of your turbo ?

[suprra_girl]

fuel cut is initiated by the computer when too much airflow is introduced to the engine (cuts fuel)

when going really fast... that's called speed

and when you hit a cut at speed it's called speed cut in which case you need a speed limit defencer

[rnoswal]

If I am going to increase the boost and I will eventually, how do I defeat that sensor?


Russ

[suprra_girl]

well that depends

some ppl like to just get a boost controller on there and turn it up silly and have no fuel upgrades to support it therefore when they stick on the fcd they end up running a bit lean and then boom! funs over

other ppl are prepared for a fcd and buy a walbro pump and raise the boost max to 12psi (depending on what mods) and install a fcd and never alter their boost controller

basically you need to tell us what mods you have in order to suggest when you need the fcd and what boost you can run as it varies alot
if you have a dyno nearby that would be even better but not everyone has those
or if you have spare money to burn buy a wideband so you can keep an eye on it

[rnoswal]

Well no mods to speak of yet, but I will in the near future. That is why I was asking about the pressure sensor. I notice there is on on the driver side engine compartment between the fender and the top of the shock tower. Does this sensor just measure fuel pressure and if it drops too much then it shute the engine down to protect it? And if so is that how you can make it stop cutting the engine just by adding a walbro or other high volume pump?

According to my aftermarket boost guage I am right at 10 psi. I played with the adjuster and got more boost but it didn't take long for it to shut the engine down for a few seconds. I know the stock turbo and wastegate won't go much past what I am putting it at and I know I need a better head gasket, etc..... but I am very curious about why and how the sensor shuts down or limits the engine if you over boost.

I thought it might be sensing the boost level, but now I wonder if it is a fuel pressure sensor or does it measure the boost and the need for fuel. If it doesn't sense enough fuel for the boost given it, is that why it shuts down or acts like a rev limiter.

I guess I am asking then, if I put a walbro fuel pump in it and then turned the boost up, would it continue to shut down or does that fix that problem. Blowing the engine up not withstanding I mean.....lol

Thanks

Russ

[suprra_girl]

fuel cut all happens in the air flow meter

the airflow is changed to a frequency of hz
when the frequency hits about 1500hz fuel cut is introduced
so basically when a certain amount of airflow comes thru the afm tells the ecu and the ecu spits the dummy and throws on fuel cut

the only way to stop the ecu from laying on fuel cut is to trick it by telling the ecu there is less air getting in (i.e fuel cut defencer)

fcd's clamp the signal at about 13-1400hz and the ecu never knows how much air is really in there
which is why you have to be really really sure you have the fuel available to compensate what the ecu doesn't see

example
lexus and 550cc injectors

you put on a lexus afm and now your car is getting 25% more air but the ecu doesn't know it is... it sneaks in thru the side chamber
the stock ecu is still delivering fuel for the air it can only see thru the main chamber.... suddenly you are 25% short on fuel.... if you go wot on this you may very well damage your engine
so to fix this fueling problem you add 550cc injectors and it's all evened out again

also there is no fuel cut as the ecu doesn't see the 1400 or 1500hz ever again (till 25psi or so) as the extra air is sneaking thru the side (so it's another fcd of sorts)

lemme know if this needs further explaining

[rnoswal]

No, you covered it just right. What you said makes sense and now I know the directions to go with this car. I knew about having to get bigger everything, don't say anything....lol, but the fuel cut was bothering me as to where and why it was happening.

So as a start I will look for the Lexus afm. It would have been so much better if Toyota would have done that first. Should the Lexus afm just plug right in, except for needing the bigger connecting hose?

Thanks

Russ

[suprra_girl]

yep the lexus is a bolt on

if your accordian hose is old and plasticy it will more than likely break when you try to put it on
so find a really really good condition one that is still actually rubber or buy a new one, least you know you won't break the hose and then break ur turbo coz the hose broke