Stuarts Overboost/FCD note

> > What is wrong with my 89?...........just recently out of nowhere my car is
> > hitting some sort of a Computer cut off!!!!!!
> >     Just today i was in second gear and going around a turn ......when i
> > punched it.....My Evc is set at .72<------which is what like 11 psi
> > maybe!!!!.......but the boost didnt even have a chance to reach 11psi io dont
> > think.........Anyway the car felt like it shut off and engine light came
> > on......The light goes off within 4 seconds and when i turn off the EVC i can
> > totallt hammer it and it is fine.......i havent tried to do it with the Evc
> > on again because i wanted to get your opinions
> >             If i cant figure this one out i am selling the thing(Supra)
> >                    Please help......Mark
> > Is the fuel cut range that CrAzy......or maybe since it is getting hotter out
> > it cuts sooner?
>      try setting the evc to .61 (~9psi) or something equally safe.
>    The factory spec for the fuel cut is something like 10.2-13.8psi
>    11 is within that range, so maybe you have one of the sensitive ones.
>    setting it to 9psi should let you know.  Changes in weather shouldn't
>    affect the fuel cut point, but they might affect the pressure readings
>    that the ecu is getting and it effects how fast the turbo builds
>    pressure and a million other things.  Set it to .60(8.7), run it up,
>    set it to .65(9.5), .70(10.3), .75(11psi) and so on until you hit fuel
>    cut.  Watch for spiking, and try it in different gears not just 3rd.
>    All else fails, order a FCD for $109 from CAP.

the fuel cut is *not* from pressure, it is from intake air mass. as you get colder/denser air outside, the air mass at a given 'boost' pressure gets more, so you will fuel cut earlier!

fuel cut is *not* boost related!

I believe that the *actual* reason that toyota puts it in is *not* to annoy people, or limit your boost, but simply that their air mass sensor does not correctly read air mass above a certain amount, so they stop, rather than risk running too lean from a bad air mass reading (there are also fuel injector issues, etc..), this is also why some cars do it at different levels, it is simply your air mass sensor 'panicking' as it can no longer accuratly measure the air mass.

a FCD does not help, it is a *very* *bad* *thing* without fuel/ECU changes, as it simply stops the air mass reading from going above a set limit, so your ECU stops putting any more fuel in, and you start running real lean, real fast, then you engine blows up (well... could after a while..), a FCD is *no* a fix to anything, a bigger/better air mass sensor (eg: lexus), other sensor (HK$ VPC)m injector size changes and ECU changes are the only way out.

or, just lower your boost a bit in cold weather, you are not loosing power, you just need less boost to get the max power in the cold, think of it as a holiday for your turbo! (remember, HP is related to air *mass*, not boost pressure (well, not much..))

>      no, it's not a fix, but it'll stop him from hitting fuel cut *grin*
>      I don't think anything over 10psi is a good idea without adding
> fuel system upgrades (at least remapping the ECU or something with an
> equivilent effect).  But he isn't really pushing it too much, he's just
> got rather sensitive fuel cut parameters I guess.
the important factor is:

with a FCD installed, over the 'cut point', no more air is sensed, therefore no more fuel is injected (assuming no fuel/ECU mods), therefore you get progressivly leaner, but no more HP (well, very little more), and overheat/stress your system! (the ignition with retard wildly to avoid the detonation, hopefully!!!)

remember, over fuel cut, with a FCD, no more fuel is injected! (by the stock ECU..)