Daz WRX

In my understanding there are a total of 3 cats on these cars..
Center cat which I have now replaced, this had the lambda sensor on and is still in place on the H&S pipe.

Downpipe cat which has another sensor, does this sensor have anywhere to go on decat pipes?

Uppipe precat again with another sensor,does this sensor have anywhere to go on decat pipes?

CEL fix solves the problem with the downpipe right?
What about the up pipe sensor WTF happens?

Cheers
Daz.

easyrider

Id be interested to hear the answers to this also.

Top.

Ninnybobs

I have a CEL fix for the Up-pipe for sale if that help.

Cheers

Martin

Steve vRS

The up-pipe has a exhaust gas temp sensor. This remains in place but is prone to failure. I think a 2kOHM resistor placed accross the plug solves that (check search for hard and fast info).

The downpipe doesn't have any sensors.

The front centre section has a second lambda sensor (the first and most important is in the exhaust manifold). This is the one that the CEL fix counters as it thinks the cats have failed when the downpipe cat is removed.

Steve

Buzzer

Steve is indeed correct

You will find with a de-cat up pipe, the sensor will probably fail and burn out due to the heat generated through not having a cat. In this instance when replacing the up pipe it is worth putting an EGT (Exhaust Gas Temperature) gauge in its place (as the cost is in the removal / replacement of the up pipe so it makes sense to do it now

Remember that when the CEL is cleared to compensate for this failure, nothing will monitor your EGT other than an after market gauge probe and gauge.

Daz WRX

Cheers guys,
So the uppipe is going to be an **** to sort out and an **** to prevent CEL errors or completly ******* the sensor.

Downpipe is the definate then which doesnt actually have any sensors on but will cause CEL errors due to the new readings on the lambda sensor in the centre caused by not having the cat.
Cel fix sorts this out.

Is that all right?

Cheers
Daz.

[Edited by Daz WRX - 11/11/2003 10:00:42 AM]

Buzzer

By Jove the boys got it

Remember that the up pipe will give you the best performance gains out of the 3 sections to replace

Daz WRX

Thought as much.
Who told you how old I was

ZIPPY

If you get your car re-mapped (Ecutek) you wont need a CEL fix as the code(P0420)is removed in the map and the readings for the EGT sensor (UP-PIPE)are adjusted and then you shouldnt have any problems with that either.

Zippy

MadGrip

sorry to hijack the thread , but I'm getting a downpipe & up pipe fitted soon on a MY01 WRX. What sort of gains in power / noise should I expect ??

Phil

Daz WRX

No probs Mad, I'd be interested to know.

Buzzer

The whole setup is around 35 BHP

There is a little confusion of which parts give the best performance but i would put it as follows (in round figures)

Back Box 5 bhp
Mid section 13 bhp
Down pipe 12 bhp
Up pipe 5 bhp

The most noticeable difference will be the mid and down pipes as this will give you the feeling of the added umph we all like. Dont confuse the high cost to performance ratio of the up pipe being done as a costly mod for little bhp gain. The turbo spools up much quicker and kicks in much sooner giving IMO just as much "feeling" as the mid and down pipes combined.

A highly recommended experience indeed

MadGrip

looking forward to it already

got the parts sat in my garage , hopefully getting fitted next week

Phil

Daz WRX

Me neither

Got yah KL as well Mad arent these recommended with the setup?

Daz.

MadGrip

not got one yet.. but maybe santa will bring me one..

got the pipes as a birthday prezzie

all free so far.. well pleased

Phil

ZIPPY

Guys dont bother with a KL unless you are going for major increases in BHP,the 50 Bhp gains with an exhaust dont warrant the KL, and also they look cr#p.

Zippy

Nathan L

As Steve above says if you want to remove the EGT sensor from the up pipe it's easy.

Instead of screwing the sensor into the decat section un plug it a little further along the wire and put a bung in the sensor hole.

Then place a 2.2 k ohm resistor in the plug that's left for the sensor and bingo no CEL.

The EGT reading is not used by the ECU for anything and as long as it sees a constant reading it will be fine.

Nathan..

Chris L

Just for your information. I've run this type of setup on my MY01 for nearly two years now (and in excess of 30000 miles covered). Currently, I have the Scoobysport (original Hayward & Scott design) downpipe, mid sections and back box. There is a very noticable gain in both power and torque - also sounds a lot better

CEL fix works a treat. I had one problem with the CEL coming on about a week after I had had the exhaust system fitted. Pete reset this and it has never happened since.

I did suffer an EGT failure about 6 months ago. Which I managed to get replaced under warranty (don't ask ). Interestingly enough ,the dealer who I spoke to had said that there had been EGT failures on both standard and modified MY01s (roughly 50-50 if my memory serves me right). So it might not just be the fact that you are running a partially or fully decatted exhaust system. It is quite possible that there was a dodgy batch fitted at the factory.

Setup is highly recommended and I'm always getting comments about it - I got stopped in a petrol station by a guy when I was coming back from the rally on Monday!

Also good for setting off alarms in car parks

Chris

hades

Many people I've spoken to say that you're just as likely to kill an up-pipe EGT probe with a standard set-up as with a decat; e.g. I'm sure Pete Croney has told me this. The cat will actually generate localised heat, so your EGT at the sensor should be lower with a decat up-pipe. As stated above, 2.2kOhm resistor, just pushed into the socket will work as a CEL fix if it fails. A cheap fix for the other CEL (0420) is here .

I always say it's worth porting your headers if you're doing the up-pipe, as you have to take them off anyway. Do a search on ported headers if you want to find out more.

Buzzer

Hades

But the EGT is placed just after the Cat which will soak up all the heat.....hence all the heat shields.

De-cat will allow the full flow of heat directly onto the EGT, surely?


Pete

(apologises for calling hades surely)

LoFi

My understanding is that if boost is left standard the EGT at the sensor in the decat up-pipe is lower than with the cat. The cat in the up-pipe heats up very quicky (it's only there to lower emmission in the first few mins after start up) and the gas exiting the cat is actually hotter than when it entered due to the heating effect of the cat restricting flows. However, Chris L is right that EGT sensor failures happen to both modded and non-modded cars. There was a time when several cars on here lost theirs at the same time, similar age cars, mine included.

Of course any sensible person who had a fully decat car would have a remap and therefore run more boost thereby raising EGT again.

Piers LoFi

hades

I'm not sure about heat due to restricting flows (need someone who remembers fluid dynamics better than I do). However, a catalyst works by lowering the activation energy of an exothermic reaction. Exothermic = produces heat. Therefore, you would get a heating action on the gas from the oxidation of unburnt hydrocarbons, Carbon and Carbon monoxide. I think?

Daz WRX

Cheers for all the comments guys, when I get the de cat I'll just put the EGT back in, if it fails after that then 2.2K ohm resistor it is.
Oh and the 26 pence CEL fix for the DP.

Daz.

JIM THEO

If your theory is right then after decatted up-pipe you should see lower EGT.
On the other hand I believe exhaust gas speed even in lower temp is what destroys the sensor gradually rather high temp itself!
JIM