Razor2001

Hi Pete,

After I have fitted my full decatt SS from turbo back I may wait to put the OBDII on until the actual CEL comes on. From what I gather as soon as the CEL comes on I can then hook up the OBDII and the CEL will go away and all will be well. No need to visit dealer etc.

Does the CEL do anything but shut off the light ??? I mean is it harmfull to run the car with the CEL on becuase of full deact from turbo back or only from the standpoint that if something else gopes wrong you will not know becuase the CEL has always been on and you think it is decat related when it is something else ?

Basically does the OBDII do anything besides fool the computer into shutting off the CEL ?

Finally what is your opinion on the heat shield.....replace or not after SS DP installation ?

Cheers,
Ray

Dream Weaver

Razor

IMVHO, I would say wire the OBDII fix in now rather than waiting for the CEL to come on. If not the CEL may come on when you are miles from anywhere, and may not be related to the decat pipe.

I would have thought the CEL would come on as soon as the decat was fitted?

DW

[Edited by Dream Weaver - 7/29/2002 5:58:29 PM]

tweenierob

After speaking to mark at the scoob meet yesterday he stated that his CEL only came on after about 3 weeks of having his decat, it also only came on when constant engine speed was happening, Basically the CEL fix only hides the decat fault and not hiding the CEL altogether... otherwise, how would other faults be shown??
Rob

Razor2001

Hi guys,

Thx for input.

What I am trying to find out is if the OBDII actaully will make any difference to the performance of my car after the CEL comes on. For example will my car run lean becuase after decat becuase the 02 sensor makes adjustments becuase the CAT is gone, but when I put the ODBII it does not make those adjustments becuase it thinks the cat is still there and hence better fueling performance etc ?

Maybe I am just confusing everyone

Cheers,
Ray

Razor2001

bttt

tweenierob

Sorry not much help on this one, understandable question though!!
basically will the ODBII hide the fact that the cat is missing, keeping the fuel levels correct y/n , or does it just stop the CEL coming on with the cat missing...
Rob

tweenierob

Just thinking about it, it would not affect fueling as it fools the ecu into not knowing the cat is missing so it doesnt show the CEL, rather than cutting the signal from the ecu to the CEL,
Does that make sense??
Rob

mutant_matt

Razor,

AFAIK, the CEL "device" (why are you calling it a OBDII (as I'm pretty certain it's not )?) will have no effects on fueling. I believe that the fueling is taken from the front Lambda sensor in the headers and the rear one is to determine if there are any problems with the CATs. Obviously, if you remove the CATs then the rear sensor will complain (as they are not doing their job (by not being there )).

I would put it on straight away so that if the CEL does come on in future, you will know that it *may* be something serious and not ignore it like you may do if you were to assume that it was the exhaust CEL. Ignoring a "real" CEL could be a very expensive mistake (or it could be a very minor problem) but it's best to not take any chances.

Matt

P.S. If you want an expert, why are you calling Pete???

Razor2001

I am still confused....

The last car I had (Mitsubishi Eclipse GS turbo) I removed the CAT. The CEL came on. I took it to the dealer and he said that my car was running lean.

So will my Scooby run lean with the CAT removed becuase the ECU sends less fuel to the engine becuase it senses that the CAT is not workihg properly or that the temps are wrong etc (becuase the CAT is not there obviously) ?

If the above is true will the OBDII not correct the lean problem
but merely enable the CEL to go off ? If so then running the car with the CEL on becuase of CAT removal is no biggy other than if something else goes wrong you will not know becuase the light has always been on....however, if the OBDII makes the 02 or ECU think the CAT is still there then fueling may stay as it was before and hence not run lean ??

Hope not too confusing, just trying to figure out if I need to install OBDII right away or if car will be ok and not damaged if I run it for a few weeks with CEL on before I get around to installing OBDII.

Cheers,
Ray

Razor2001

Thanks for response Matt,

Umm, I thought it was called a OBDII I guess not, anyway it is the little magic box that gets rid of the CEL when you decatt your car

So if it does not affect fueling then it does absolutely zero besides shutting off a little bulb ?

Cheers,
Ray

LoFi

IIRC The magic black box gives the ECU a fake emission reading from the sensor after the downpipe, nothing more. Stops the CEL coming on to tell you the CAT (which you have removed) isn't working properly. The CEL will still come on if the ECU detects any other problems. The fake info the black box is giving has no influence over fuelling, just fools the ECU intot thinking emissions from the CAT are normal (which they are not).

Hopfully Pete will wade in shortly . . .

Piers LoFi

mutant_matt

I believe, you have hit the nail on the head

Razor2001

Thanks again guys you are a big help...

Now I need Pete to respond on the Turbo heat shield question I asked as he seems to believe the heat shield does not need to be replaced where as others believe it should be replaced

Thanks again guys and Scoobynet for help !

Can't wait to install the DP and centre sections, yeeee haaaaaa, 300 bhp here I come (but more importantly I will be able to take someone walking off the line thx to increased low down torque

Cheers,
Ray

FLAT ERIC

iTrader: (1)

As Rob said my light came on usually at a steady engine speed.And you would get the error code "PO420" Cat below efficiency threshold.When reset it would go for between 3-21 days before coming on again.Depending on how I drove.

The fix is wired in line with the rear O2 sensor next to the ECU & gives a modified signal from the sensor.Fools the car into thinking the cat is still there by giving it an average reading.
Purring doesnt work.

If you now get a fault it will throw the CEL in the usual way as it will receive readings outside its parameters.

Glad mines done now 'cos living in fear of the light coming on & having to trust that it's just the zorst can turn you to drink.



All is explained here.
http://www.scoobysport.co.uk/exhaustswrx.htm

Mark

[Edited by FLAT ERIC - 7/29/2002 10:14:18 PM]

Razor2001

BTTT

Pete Croney

Morning Ray

Piers LoFi is spot on, the little box only affects the signal from the rear O2 sensor. When the car is held on a light throttle cruise, the ECU performs a check routine on cat efficiency. The box makes sure that the ECU sees what it wants to see. Fuelling is controlled by the front O2 sensor and is unaffected. You should fit it straight away.

You should also refit the turbo heat shield. It will need to be trimmed to fit. Make a cut from the top of the arch, over the downpipe, across to the right hand corner in a line that goes just below the rear bolt hole. At the corner, make a cut straight down to the bottom.

Adam M

how much do these little boxes cost and can they be bougth separately?

Pete Croney

Adam £50 and yes they can.

Razor2001

Thanks Pete and everyone else for help

Cheers,
Ray

mutant_matt

Pete,

Your little boxes must be doing a roaring trade these days? Have you sold many?

Matt

Big Goon

Had my center pipe and small cat (front/rear???) removed yesterday for a pair of ScoobySport straight thru's, £200 well spent, picks up better and now has a half decent exhaust note and throb again

Big Goon

And btw, so there was a sensor in my small cat, and thats now sat in the new straight thru piece of pipe ?
If so wont the rear sensor notice the smaller cat missing ?

Pete Croney

Shane

The centre cat is downstream from the sensor.

Matt

A few yes It works on the non Subaru cars we have tested it on too

Big Goon

Thanks Pete