Not so far ago I replaced my standard 20NE CAM with a 20SEH cam and changed the CHIP for the 20SEH maps. I took the car for a little bash around europe (around 7K miles at speeds over 100mph) I experienced no problems with my engine during this period. So I have now come back and decided to have a look at the spark plugs. I was a bit surprised to see them having a dark brown color. They look like they are corroded. Do you think this color is OK?. All 4 of them have the same color.
Yes the color is dark brown mat color. I was surprised because sofar I have only seen grey colors on my spark plugs. It may be because the engine has been primirily driven with no idling at all, always almost af full throttle, whereas I normally just do a mixture of town, B roads and motorway driving.
No, I did not fit any different pistons, but the head got skimmed when I fitted the new cam, so I recon the compression ratio must have gone up a bit. Also because I don't think I have a compression ration of 10, I can run 98RON maps with 95RON fuels without having any pinging.
I have noticed a definite improvement over the standard with the engine definitelly more willing at the higher RPM. However, the standard ratio gearbox does not help so 5th gear is only good to mentain speed but it becomes useful at speeds above 120mph and down the hill where I managed 140+ (on the clock!).
With the new CAM economy was a bit worse on average about 3mpg worse (about 30-32mpg) but then I was progressing a bit faster.
I guess with a slightly wilder CAM (270 grind) , reprogrammed ECU and a close ratio gearbox will be the best for performance but economy will drop even further.