Would it be possible to rig a large scale servo (as I have a spare) for the throttle?
If the servo has got the power needed, then sure.
Main questions here is: What is the servos torque and what torque is needed to move the throttle.
Whether you'll find it sufficiently precise is another thing to consider.
I think the main problem will be learning the programming and getting the thing wired up correctly.
Yes, but these days program libraries exists for most stuff (a library is an assembly of routines that does the grunt work of something when you call it from your program).
Wiring it up as easy as possible probably means that you should get a board which has got as much of what you need, to minimize what you have to make yourself.
Do you have any recommendations for the microcontroler I've looked at the Axion on here would that control the motors and cope with the datalogger?
I'm thinking more in terms of something with as much as possible already on the board - like eg. an (µ)SD card slot, an USB server or whatever will let you transfer the measurements to the PC with less soldering on your side.
Something like this board
(US$60), a board I have myself, or, if more speed and storage capacity is needed, this board
(US$50) or even its smaller sibling
The last two board doesn't have an SD slot (although the larger of them has got USB OTG),but they're blindingly fast and especially the larger of them is crammed full of goodies and you won't be running out of RAM space.
However, selecting the board really cannot be done until you have decided on how you want to transfer the data to the PC, as no two boards are the same.
I'm guessing I can rig a push button to activate the program
Most boards have a reset button and that's all that's needed (or just let it rip when you apply power, which generates a reset event anyway).
or could I interface with a pc and run it from there?
Sure, but do you really want a PC next to a dyno (dirt and oil "fog" in the air will not be the best environment for a PC).
If you really want a PC in there, a better solution might be to use a USB interface/measurement card on the PC.
I'm in the uk so hopefully they can ship here.
I have never had any problems getting stuff sent to Denmark, so I cannot imagine there should be any problems at all shipping to UK. All the hardware (boards, programmers etc.) from Microchip shipped to inside EU, is ab UK anyway
If I had to make this, I'd start with the interfacing hardware (motors, their linkages an the sensors), then add the electronics controlling them and testing that each behave. Then (and not a second before), I'd select a board, get it, program it and put it in service.
This way you know exactly what you need and the time tinkering with the hardware will let your thoughts on how it should all play together will mature.
BTW. wouldn't you need a sensor for measuring relative humidity as well?(Changes in R.H. from one day to the next can seriously render your measured data untrustworthy, as power depends quite a bit on R.H.).