I'd like to know if anyone has tried this:

I'm not using trailing plugs in my turboed NA S5. In a perfect world, i would like to experiement with different boost levels and compression ratios and find out what the best combos are for performance.



Has anyone tried replacing their trailing plugs with some sort of small chamber that threads into the rotor housing? this would lower the compression ratio depending on the volume of the chamber. i know this would be bad for emmisions, but i wonder if it would work. maybe the trailing plug hole is so small, that the pressure wont have enough time to move into the chamber at any reasonably high RPM? anyone have any thoughts on this one? I can try to make it more clear what I mean if there is any confusion...

Thanks

 

I have doubts about that one.



Not that I think the hole is too small on the trailing spark plug, but controlling your fuel and ignition with a Z axis of compression - I mean, thats a whole new level of tuning that IMHO isn't needed. Why would you want to be able to change your compression ratio that often? It should be static...



A simple test would be to check your compression with the trailing plug in vs out. At least then you have the "range" of what is possible...

 

The trailing hole is so small. I dont think it can do much.

 

One320B, what do you mean by Z axis? which way is X and Y?

i want to do different tests with boost levels at different rotor compression ratios...just for the sake of learning something. aslo becasue i have an NA S5 and a BUNCH of bran new huge turbos i am itching to put on the motor. we are planning on running the turbocharger half as a turbine engine with propane, so we are planning on putting an oversized turbo on the motor, since spool up time won't be an issue (in theory). beacue of this, i would like to run at a high psi in order to run the turbine spool where it is most efficient.

 

Z axis is a 3rd dimension in most geometry studies. I was just making a point that it would a whole new variable you'd have to compensate for during tuning. Fuel and Timing would make up X & Y.



The trailing hole is small - but if you leave a plug out, it makes a big difference, lol...



If you want to play with compression, why not just start looking at some crazy porting or timing instead - you'd probably get similar results. Low compression means more fuel, more timing and more boost. But you can get similar power from high compression just by using less timing and less boost, still needs lots of fuel though, lol...

 

you need to really look at the volumes involved. whats the CC of the camber @bdc? and tdc? this will tell you how big of a "chamber" you need, and weather it'll even fit.



what would be neat, is to put a baloon on there...