Pre cat chip to cat car ??

[jasoncook]

Hi all ,Well I was wondering if anyone had fitted a pre cat chip to a cat car changed the resister and set the co using the adjuster on the air flow. This would let you set the mixture pre 3k to a little richer hence smoother and no switching time when the system swaps from lambda loop to full mapping. I have no pre cats but the main cat would remain. My car seems to eat lambda sensors and runs on neat fuel before the lambda’s start switching any thoughts cheers Jason

[FlipFlopGriff]

Jason,
I've tried it on a fully catted 500 (the one that we took the photos together at Back Home) and it did run smoother, but only tried it for a couple of miles. Can't help further than that I'm afraid.
FFG

[grahamw48]

Mine has had it done the other way round...cat to no-cat (Chim engine in Wedge, using Chim ECU).

Runs perfectly.

[jasoncook]

did you use the chim ecu or the wedge cats in or out.

[grahamw48]

Chim engine with matching ECU, tune resistor changed to non-cat.

Wedges never had cats of course ( original Wedge headers and exhaust system used ).

New Real Steel 218 cam fitted, which I feel is too mild, but probably ideal for the supercharger I'm saving up for.

Also just had adjustable fuel reg' fitted.

Better exhaust manis on a Chim should release more power though.
Mine only makes 195 at the wheels.

[jasoncook]

I think the 5.0 litre map has only a tvr map on the cat resister choice ,I have been told if i just swap the resister for a non cat without the chip it will revert to a 4 litre map.

[FlipFlopGriff]

Jason,
Probably worth a call to Heath or Dom at Power.
FFG

[JKY]

blitzracing (generally on the Griffith/Chimaera forums) should be able to comment too as he uses a switchable resitor to test bed this set up - tested my 500 on non cat briefly and it ran far smoother with rock steady idle.

[blitzracing]

I think TVR only ever modified one fuel map for each application, so switching to the non cat map will revert to the origional Lucas program for an unmodified engine. Worse than that, the catalyst needs the fuel lambda cycling to keep it working, so if switch to the non cat map the fixed mixture may overheat the cat' and damage it, so its not a permanent solution. The TVR engine does idle better on the non cat map, and tends to shunt less, but the full power is no different as the ECU goes open loop anyway. The overfueling you refer to on start up is the same on both maps , but it should not damage the sensors. The Mark Adams chips do have both maps modified for a specific engine, and greatly reduced cold start fueling, and would be a much better solution.