We have also been doing some gearbox temperature testing over the last month or so.
We all know about the problems with S2 gearboxes and we have chatted to a fair few gearbox people about this in order to try and nail down what the problem is. The conclusion we all came to was excessive temperature in the gearbox resulting in thermal expansion of the casing which in turn looses all of the internal tolerances and things start to get all wibberly (that’s a technical term).
This problem is also present in the Rover PG1 gearbox. A good friend and fellow racer David Harvey has extensively tested his gearboxes including warming them up in an oven and measuring this expansion and contraction. His results were quite eye opening.
I had noticed in my S2 that after 3 back to back laps at the Nurburgring (the first track day i did in the car), the change started to get a bit sloppy and not as nice as when the gearbox was cool.
We had already designed a gearbox cooler system for Ade’s car and we always had the idea to refine it and make it a proper kit, but we wanted to do some testing first.
So we fitted my car with a gearbox temperature gauge and started driving. On normal road driving there is no problem at all, the oil temperature never went over 78 degrees C.
On track however it was a different story. After about 10 minutes on track the temperature was 110 and still rising!
We switched the cooler on and after about a lap the temp was down in the mid 90’s.
We did another track session with the cooler on all the time and the temperature never went over 90.
More to the point the quality of the gear change stayed constant with no woolyness at all.
In our chats with some gearbox oil experts (and we have spoken to a few of those as well) it seems that the standard very low quality oil that Lotus put in from the factory actually turns corrosive at 100 degrees and will literally start eating the synchro’s!!!
A good quality gear oil will handle the temperatures no problem, but of course from the conversations we have had it is thermal expansion of the gearbox that is the killer here and keeping the oil temperature under control will help reduce this.
I dont want this to be a blatant sales focused post, I wanted to pass on the information we have found, but we have now enhanced and finished the kit and they will be available soon.
before the cooler was fitted.
