Positive displacement S/C w/ spray (nitrous/methanol)

[Razathorn]

Hondata, something has confused me and I was wondering if you could shed some light on it. My water/methanol injection system sprays a 'constant spray' in the intake tube based on the psi behind the nozzle and the nozzle size. I thought when I went to tune with it that it would result in far more mixture being used at the lower rpms than at redline and I would see things leaning out at 8500 long before 4500 for instance. What I saw was quite different -- spray alone richened everything to below 11.5 and leaning out via the nitrous control panel with fuel units across the board generally brought the a/f curve up on both sides (4500 and 8500) about the same... meaning it didn't lean out up top any sooner than down low. I thought that there would be 'less methanol per put' at 8500 and hence it would lean out more and I would end up tuning fuel a lot more to get a flat a/f under spray.

Any ideas on why this is?

[Hondata]

I understand your post, but can't explain the behaviour of the AF with a constant methanol volume. It could have something to do with droplet size and vaporization, or could be some other factor I am not aware of. I seem to remember that I saw the same thing with my turbo. It actually makes tuning a little easier when the AF curve shifts up or down by the same amount over the rev range.

[Razathorn]

I seem to remember that I saw the same thing with my turbo. It actually makes tuning a little easier when the AF curve shifts up or down by the same amount over the rev range.

Indeed it did. I also initially saw a boost increase in the top of the rpm range. I'm really confused as to what is going on as I expected fuel to be different and I expected boost to drop a bit on the 9psi pulley. I guess the spray was making the air denser before it got into the blower as well.

Wayne

[Razathorn]

I seem to remember that I saw the same thing with my turbo. It actually makes tuning a little easier when the AF curve shifts up or down by the same amount over the rev range.

Indeed it did. I also initially saw a boost increase in the top of the rpm range. I'm really confused as to what is going on as I expected fuel to be different and I expected boost to drop a bit on the 9psi pulley. I guess the spray was making the air denser before it got into the blower as well.

Wayne

I determined from another location that the increase in boost on my roots supercharger was due to the water/methanol mix decreasing the gap between the blower case wall and the roots rotors, causing the blower to increase pumping efficiency due to a 'better air seal' between the wall and rotors.

Figured since I just stumbled across this thread I would chime in again.

[deafy]

how do you have your water meth kit hooked up? what is controlling the pump and etc?