Hypothetical de-cat question

[wheeljack888]

If you use the green tune resistor does it send the ecu into an open-loop fuel map, and therefore allow you to remove the lambda sensors?

Thanks

Phil

[GreenV8S]

Yes, I think that's the theory.

[wheeljack888]

Cheers Peter

[HarryW]

Assuming that the de-cat map is populated, no harm in trying I suppose. Also my assuption is there is more than one map, not just a modified way of read the one map that is .

Harry

[s4s280]

Having been down the Lotus Elise route of decat for daily running and CAT for MOT, with my Chim, I'm interested in this one.

The main CAT must be a bloody expensive item, so I had the thought of a manifold change and loose the pre cats, then a "DECAT PIPE" and refit the main CAT for MOT.

Thus - hopefully saving it for MOT purposes and maybe gaining a better gas flow from the heads.

Has it been done before, or am I dribbling on a bit ?

Bob



>> Edited by s4s280 on Monday 27th June 14:00

[victormeldrew]

Yup, I have two sets of pipes. One catted, t'other empty. All standard TVR parts. No visible sign of modification! A slightly expensive way of doing it, as the non-cat tvr manifolds and Y piece were over a grand

Not sure about the ECU changes - if anyone could fill me in I'd be obliged. Team Central did the change years back and I don't know what else they did other than the pipes.

I understand performance could be improved by fitting cones inside the cat chambers to smooth the flow, but somehow having bought factory parts I just didn't want to start hacking them about!

[raceboy]

Well mines not had a any sort of cat in it for about 2 years now, no remapping, still got the Lambda sensors in, and other than a little extra noise no problems

[s4s280]

Raceboy - Presume you still fit the CAT back for MOT though.

Also guys, if the green resistor is used what is supposed to happen.

I love all this Efi tweaking knowledge

>> Edited by s4s280 on Monday 27th June 14:00

[raceboy]

s4s280 said:

Raceboy - Presume you still fit the CAT back for MOT though.

errrrr No

[wheeljack888]

s4s280 said:

Also guys, if the green resistor is used what is supposed to happen.

I read in Steve Heath's book that TVR ECU's have two fuel maps programmed in. The fuel map for catted engines is activated using the 'white' tune resistor (~4000 ohms) and non-catted engines use the 'green' one (~470 ohms). I bought my green tune resistor from Rimmerbros. My hope was that the non-cat fuel map would be open-loop and therefore not need the lambda sensors for fine fueling tuning at light throttle and idle.

I shall find out soon whether it works when I finish putting the engine back together (and also when I've recovered from a particularily heavy Glastonbury!)

Cheers

Phil

[victormeldrew]

and this resistor goes where?

[wheeljack888]

victormeldrew said:

and this resistor goes where?

It is a heat wrapped resistor wired to a 2" long 2 pin connector on the main wiring harness very near to the ECU. The white resistor part no. is PRC8009.

Cheers

Phil