Help with decat on a TII

[no_boingers]

Hi chaps,

If I replace either or both of the cats on my FC TII with a de-cat, do I need to do anything else?  E.g. do I need to remap the ECU? I don\'t really cane it so can I get away without an FCD?

What do I do with the aux air pipe - leave it open to atmosphere or blank it off?

Perhaps most importantly, what effect will the decats have on the CO & HC emissions? (remember this is a TII not an EGI )  MOTs are already stressful enough and I don\'t want to increase my worry!

[B.Martin]

I was told you need to port the waste gate and got a new actuator; someone till be along to confirm this I\'m sure

[L18M]

if you dont cane it then why de-cat?
not beneficial and just spending more money.

if you de-cat and drive like a grannie should be ok. if u cane it then will most likely get boost creep / boost spike.
hence port the wastegate

fcd is if u want to run a bit more boost, but if u driving miss daisy then you prob wont hit full boost anyways.

[grinder]

Humm this is an interesting one

i thought that once you decatted you HAD to run a FCD

But my white cab has been decatted and runs no FCD and pulls fine etc..

So im not sure , if you decat it fully AND run a cone filter .. thats the time for the FCD ?

and the air pipe - i just left mine venting into the air under the car

[L18M]

stock boost is what .5 /.6 bar? once it hits this then the ecu will cut fuel to prevent further boosting.

fcd will prevent the ecu from cutting fuel so u can run unlimited boost. if u running .9 bar the ecu will assume you running boost at just below the fuel cut point.
you run the risk of running lean with fcd, as stock ecu is not mapped for more than stock boost (i think prof proved this in one of his threads). so means running aftermarket ecu that is mapped for .9 bar boost.

decat allows for free\'er flowing exhaust so turbo will spool up faster so where originally with cat, you might hit fuel cut at 7000 rpm at .5 bar (for example), with decat it will spool quicker so you might hit .5 bar boost at 6000rpm then fuel cut will kick in.

same with free\'er flowing air cone.

thats my understanding anyways.

the other pipe, just put a breather filter (baby mini air filter) on it will be fine.

[dthebuk]

shouldn\'t need to port the wastegate with just a decat. If i were I\'d just decat it and fit a chipped ECU(or fcd, preferably the ecu though). Keep an eye on boost pressure and if it rises above 0.9 bar look into porting the wastegate or running a leaking BOV. Porting the wastegate is quite long and if you\'re waste gate spring is no good, it\'ll open prematurely and increase your spool time. If you could fit a new stock spring you\'d probably be alright, not sure how easy they are to come by though.

Not really clued up on emissions, you could always run the air pipe into the exhuast somewhere to help trick testers, not sure how well that\'d work. If you\'re not using the air pump then remove it. It will free up a few horses and may even help emissions!

[no_boingers]

Thanks for all your replies.

if you dont cane it then why de-cat? not beneficial and just spending more money.

Because the existing cats are shot.  Replacement cats = £600 + £750 = £1,350.  Decats = £70 + £80 = £150.

if u cane it then will most likely get boost creep / boost spike.

\'Scuse my thickiness but what is "boost creep"?

if u driving miss daisy

I keep my speed thrills for the race car.  Besides you can\'t pose if you\'re going too quick :p  
I\'m not a great fan of turbos - the last thing you want on a wet country lane is the turbo kicking in halfway round a tight bend - although the stock TII is a lot smoother than most.  Of course if all you want to do is drive quick in a straight line... :mmmm  But I digress...


Okay so no FCD or remapping or wastegate/BOV mod, breather on the aux air pipe, max boost may be at slightly lower rpm, CO will probably be ok, HC may well go up.

[B.Martin]

\'Scuse my thickiness but what is "boost creep"?

This is when the car boosts more than is mapped for, thus not having enough fuel input and potentially leading to run lean and then very bad things can happen :rolleyes:

[no_boingers]

OKIC ta.

What are "very bad things"?  It runs lean = combustion chamber temp rises = ??

[B.Martin]

Engine dies due to lack of fuel, i\'m not sure the ins and outs but i know the RE likes to run rich on fuel. I\'m sure someone can explain later, but if your not thrashing it and you have an AM boost gauge you can keep an eye on i wouldn\'t worry to much.

[TiddlesRX7]

You should be fine just de-catting it. Don\'t worry too much. If you do find yourself hitting fuel cut then get an FCD. A chipped ecu will be too much for a stock car as they generally are set up for a full decat system, modified intake and front mount intercooler.
As above porting the wastegate is a bit overkill also for what your doing. If you were gonna modify it further down the line then yeah go for it but its a big ish job to do just for the sake of it!

Ade

[B.Martin]

Have you ported your wastegate Ade?

[dthebuk]

Because the existing cats are shot.  Replacement cats = £600 + £750 = £1,350.  Decats = £70 + £80 = £150.

Jap downpipes and cats (good upgrade) usually come up on ebay for about £30. If its a UK car that you have you\'re likely to have 2 cats (jap cars only have one). One is in the dowpipe and one is further down the exhaust. If you\'re still running the stock downpipe you wont have any issues with boost creep etc

[no_boingers]

Yes 2 cats at the mo.  I probably only need to change the main cat sooner than the downpipe.  I\'ll keep an eye out on ebay.  Thanks for your help.

[Brett]

Fit an FCD, fuel cut is not good for the engine.

Also, check the wiring of the fuel pump as this can lead to woe on a lot of FC\'s.

Ideally you want to get a boost controller, or possibly fit a restrictor in the down pipe.