Exige S Decat

a little birdy mentioned that decatting an exige S isnt the thing to do as maybe will run lean and detonate and fOOK rings etc etc
any thing in this???

have done 2500miles on my exige S with ITG, decat and ultra.
no noticable problems and no MIL illuminating.

As a general rule reducing the exhaust back pressure will increase the exhaust gas scavenging of the cylinder so that the mixture which is then compressed has a higher density/fractin of fresh mixture in comparison to exhaust gases.

This change in mixture can lead to more detonation so the ignition timing may need to be retarded. On the 240R it runs higher boost (which has a similar effect) and the ignition is retarded to compensate, detonation occurs more often at low to medium speeds which is why the S has pretty much the same torque is the 240 in this range. The S has more ignition advance and runs much closer to the thermodynamically optimum ignition advance.

I’ve not got any experience with the supercharged toyota so I cant say how easy it is to hear any detonation but on the all ali K series you can hear the tinkling sounds a mile off. Decatting a base 120PS K series S1 usually results in plenty of detonation. I’m not sure with your exhaust if you’ll hear it though?

If in doubt run it on optimax/ultimate (presumably its set to run on 95RON normally?).

Also - I’m not sure on this one but does the Lotus ECU have knock control, I doubt it, but if it did it would automatically retard the ignition.

thanks bob.
not sure about knock control on the ECU.

will try to run on optimax. pressumably this will only help and not totally prevent.

Hi Craig, I’ve just been sat in the dealers for an hour and a half having my gearlever fixed and spent most of the time reading a service manual (well worth buying). The car does have a knock sensor so it should recognise any detonation and back off a bit, if you run it on 98 it will allow it to put keep the original amount of advance and give a little more performance. Thats the theory anyway…

thanks again bob…

that sounds like its sorted then.
i can get out blasting without fear of melting me pistons.

mind you its difficult to push it over 4500rpm as it sounds like something is going to explode or put it another way like the world is going to end