Decat Question

[tonyhawk]

At present I still have the front cat in my exhaust (the middle one has been replaced with a the through pipe), but I've been told that the back pressure created by the cat is used by the turbo's to prevent over boosting, is this true?

 

I have an HKS EVC controlling my boost, so I would have thought that a full decat would be ok?

 

Any thoughts?

[hadyn]

If your car is a jap spec, you'll need a restrictor ring once you remove the other cat to make sure the car doesnt boost past 1.2bar

[tonyhawk]

But I thought that's what the boost controller was doing?

[hadyn]

Your b.c. can only raise boost, not lower it. Hence it will always be at a minimum of the pressure set at the actuator. So if you fully decat you might be hitting 1.2+ bar or you might not. It depends from car to car

[TT-DEK]

HI Tonyhawk. Dodgy here. Sometime next week my sooop is going to Chris Wilson to Decatt and put restrictor rings in!. Mine is a JSpec too and is correct what is said? Also cold plugs required and fuel cut defender, and new fuel pump. Should give an extra 40/50 BHP! Will let you know when done.

[Steve]

Hadyn is totally correct on this one.

Gold star for you:clap:

[tonyhawk]

Thanks for all the responses.

 

Is this 1.2 bar limit required to stop damage to the turbo's?

 

If so, then as mine have been rebuilt to take more than that (1.5 bar according to the engineers who did the work), do I still need the restrictor ring? If you look at my car's spec, you can see that I have also upgraded the other bits (although not enough fuelling for 1.5 bar yet), so I'm not sure what to do.

[chilli]

Yes the 1.2 is a good safe limit for standard turbos. It depends on the full spec of your rebuilt turbos but unless your turbos are decent hybrids then I doubt it's worth going over 1.2 bar. It starts to be diminishing returns as although they may not fall apart, they are starting to outside of there efficiency range anyway...

 

If your sure of the spec of the turbos then you might want to go higher than 1.2, if you can't 100% verify their spec I'd personally run at 1.2 max.

 

Edit: just read your spec, says "hybrids" so they may be ok, but thats a generic term really, depends what they are. Dont forget the fcd and you will def need a fuel pump upgrade to, to be safe.

[tonyhawk]

Thanks for that; I do have a Walbro fuel pump, and an FCD, so fuelling wise it should be able to take it. The turbo's were both fully re-conditioned by The Turbo Clinic; the ceramic blades were replaced with steel ones, with both compression and exhaust wheels having been enlarged (and properly balanced), as well as all serviceable parts being replaced.

 

When I asked what pressure they would now provide, I was told 20/21psi (1.5bar)

 

Your b.c. can only raise boost, not lower it

 

But the BC dictated the level of boost, and when I change to the lower setting, then boost is limited to 1 bar, so surely that suggests the BC can limit boost?

 

I apologise for my questions, my technical knowledge is patchy, good in some places, but extremely lacking in others

[Scoboblio]

The boost controller can limit the boost to 1 bar at the mo because you still have the front cat in to control it... so 1 bar is probably the lowest you can run right now. When you take the front cat out the lowest possible boost will be raised, probably above the safe 1.2 limit unless you fit a restrictor ring.

[tonyhawk]

Ah, I see, that makes sense; ta.

[Clarkey]

Don't raise the boost above 1.2. Assuming you have a J-Spec car. You don't have the supporting mods to go any further .. on those Hybrids

 

Correct me if I'm wrong .. techie people.

 

Bigger injectors,

A decent FMIC to keep those EGT's down

A fueling computer to control the injectors

 

1.4 Bar would be the maximum, I think .. because of the EGTs.