de-cat over boosting

[jayssupra]

hi

can anyone help me i have just removed 2nd cat of my supra still got first one but car hits fuel cut is this normal on j spec tt, just bought turbosmart fcd but not sure what boost i am running at because the turbosmart fcd has a tap to change fuel cut, so because i do not what to over boost car i do not what to turn tap to much car is great in 1st 2nd and 3rd but top end of 4th i hit fuel cut again should i turn tap some more or change fcd for a electric one witch you wire to the ecu if so can anyone tell me whitch ones are best.

[Nic]

Yes removing 1 or boths cats will usually increase the boost pressure on a J-spec Supra. The cats are quite restrictive and so help to regulate the stock boost limit. The stock fuel cut is around 1bar so you are obviously going over this limit at the moment.

Do you have a non-standard exhaust fitted? The stock exhaust is also quite restrictive and so most aftermarket exhaust will also cuase a rise in peak boost pressure.

I'd suggest the following:

1. Fit a boost gauge, this is vital, without one you do not know what boost you are making, which is the problem you are facing at the moment. Mechanical boost gauges are relatively cheap, electronic ones are more expensive but offer other functions such as peak boost, overboost warning etc.

2. Once you have the boost gauge fitted you will be able to adjust the Fuel Cut Defender to say 1.2-1.25bar.

3. If you are still hitting fuel cut once the FCD is adjusted, then you should fit a restrictor ring in the exhaust. This is basically just a plate with a hole in it that bolts into exhaust, to limit peak boost. Contact Chris Wilsom SEE HERE (http://mkivsupra.net/vbb/member.php?u=54) for contact details, Chris can supply restrictor ring to roughly the size you'll need.

Let us know how you get on.

[Nic]

Just re-read your post I would suggest fitting an electronic Fuel Cut Defender, see Thor in traders section, they do their own FCD that many members here use. It will raise the boost cut limit to 1.25bar (rather than remove fuel cut altogether, which other FCD's do.) I think they call theirs VFCC.

[jayssupra]

thanks for the advice will check out thor racing and will let you no

[dude]

you deffinatly need a way of telling what boost you are running dude , invest in a decent guage as ive seen plenty that are way out , a nice feature is peak hold as its not as easy as you think to see the max pressure hit unless you are on a straight quiet road .

Dude :cool: