Funny you should ask that. I was at Dave's yesterday.
Very interesting day and some great learning curve stuff.
So last time was the dead clutch and crap power. So this event was all about proving the EFI throttle body injection actually works and optimizing for the pipes and porting I currently have. That then gets me the build base I need. Basically if I made stock power and it was easily tuneable I would be happy.
So.....The clutch held but in the end it won't be strong enough so will need to sort that later.
First few runs we concentrated on fueling and ignition. My ignition map needed to start much higher at the low revs. i think it ended up at 32 and 1500. Will post the map later but remember we are only working at WOT so the lower end of the map will look weird, basically just look at the 100%TPS line. So we fiddled with that and fuel and got it burning OK but it ran out of power at the top end and the curve shape wasn't great.
When I set my throttle bodies up (Tiger 1200), I did a volume check compared to the 36mm carbs I originally had and as the Tiger bodies were so much larger (42mm), I reduced the butterfly opening accordingly to match the volumes roughly. Long story short.....2 strokes use twice as much air as 4 strokes.... My power was massively dropping off at WOT. Couple of cups of tea and some head scratching and we worked out the bodies had to be pretty much wide open to work. Quick adjustment of the motor speed controller and bingo massive gains!
Now I could add much more fuel across the map (god I love EFI, 2 second tweak and no stinking of petrol
) and Ta Da! .......BHp!
Basically I got it to roughly stock BHP....which was the plan. Throttle body EFI reed valve, piston porting can work on a Kettle!
Next we had a look at the porting. Fundamentally my transfer timing is a bit short. Looking back at the TR porting compared to mine (previous post). I could do with raising the roof by 4-5mm. So there is a job for the strip down.
Next was the exhausts. They are a bit long which can be good for torque but will affect the power. We ran a few calcs on Daves fancy software and I would probably do with widening the belly diameter as well. I also need to look at my inverted stinger design as a few mm error can have an impact.
Anyway... we started to do some more power runs getting improvements playing with the bodies and fueling and timing and got er revving nicely to 7500 (target in the design is 8500) and then I had a head gasket let go!!!
As you will remember I have removable squish heads and after a previous dyno issue where my O ring design also let go because my squish head diameter is slightly undersize and doesn't seat properly on the O rings in all 3 heads due to the tolerance of the head bolt holes, I fitted a standard gasket just to keep getting data ......but that has now gone.
Thankfully I know why so I need to fix the head diameter/O ring tolerance. Dave also recons I need to up the Shure hardness of my Viton O rings to 90 in the head.
Also when I install the new heads the trick is to assemble the head without O rings. Clamp it flat and do a tiny skim with everything clamped to make sure it is flat with no movement. I think I am getting some movement at high revs.
So a few steps forward and one back as usual. With the pipes and porting I have I think some more map tweaking will get me 90+ then I will need some port/exhaust mods.
Learning all the time......
