whizzybang

Hi guys,

If you look at my signature, i got a slightly modded engine.
But since my engine has got 125k miles on the clock and still pushing 315hp at 12psi, i installed an AEM wi kit. With water only.

I run the middle sized nozzle which should be 350cc/min iirc.

Started the injection at 5 psi with max flow at 10. I did that mostly to remove carbonization from my old engine. The car runs like a dream, except after 6500rpm it misfires due to my stock ignition system not being able to cope with that much water i guess.

The result is : after 20km of hill climb, the 1 gallon tank is nearly empty. This got me thinking : do i risk anything injecting too much water for my setup ?
I know water and oil dont mix but could this cause lubrication of the housings to fail due to water "washing" the oil off ?

Otherwise, this is the best mod i did on my car, hands down. My tuner couldnt believe an engine that old could push that kind of power !

peejay

Misfiring under heavy load will cause engine damage, that'd be the big thing to worry about.

whizzybang

Could you tell me why ?

tom94RX-7

iTrader: (5)

Maybe you should just put the small nozzle in.?

tom94RX-7

iTrader: (5)

And no you're probably not injecting enough water to wash oil off, just a guess though.

Howard Coleman

iTrader: (6)

you are fine at 350 CC. what plugs? what gap?

HC

whizzybang

BUR9EQP on all four, but i didnt measure the gap prior to install them. What should i put them at Howard ?

Thank you

Sgtblue

iTrader: (16)

Assuming from your signature you're still running the stock OMP, I'm an advocate of ALSO pre-mixing at about .5 oz. per gallon. Injector duty goes to zero off-throttle, sometimes for long periods. I feel neither pre-mixing or the OMP are ideal by themselves.
Our cars are similar in power and I'm still on stock ignition. I've been doing both for about 3 years with no issues. Plugs still stay clean, so I don't think carbon is a problem. And I still get knock control and cooling. No break-up with M3 nozzle water-only. And I'm not even progressive.

whizzybang

Sgtblue, regarding the injectors, are you talking about fuel or oil injectors ? Because i dont think oil injectors are cut off on overrun. And even if it was the case, manifold is under vacuum so no water is injected.

I am talking about max flow at say 3000 rpm where i already am at 12 psi of boost.

Howard Coleman

iTrader: (6)

i don't believe your plugs are gappable. i would look very carefully at your primary wires/plug wires and boots. you could have voltage leaking to ground. if you can can find a set of Autolite Racing AR3932 plugs give them a try at .023 gap.

btw, you are doing your motor a big favor w the water.... major de-carbonization.

howard

Sgtblue

iTrader: (16)

Talking about fuel injectors. If you just premix with a PFC, on deceleration/off-throttle (like when your going down hill, foot off the gas pedal and engine braking) your fuel injector duty cycle goes to zero. Premixing means during those periods there isn't any lubrication either. Running just the OMP doesn't have this problem on the FD it's rpm and load based. BUT, the OMP injects crank case oil that's not designed to burn and with at least some contaminants.
You were concerned about sufficient housing lubrication, so I thought I'd mention my rationale for both...pre-mix and use the OMP.

whizzybang

Oh ok sgtue i understand now and yes i still use the stock OMP. I plan on puting a two stroke oil tank in the future though. Thanks.

Howard, thank for the tip. I'll check the wires, and try and source a set of these plugs. Can i ask you what you think about that power curve ? Does it translate a lack of ignition power at high rpms like i thought ?

Howard Coleman

iTrader: (6)

"what (do) you think about that power curve ? Does it translate a lack of ignition power at high rpms like i thought ?"

you used the correct description in your first post.... "misfires."

note your power is smooth til you get to around peak torque. peak torque is maximum airflow and maximum combustion chamber pressure. after peak torque rpm causes not enough fill time so the pressure reduces a bit.

peak pressure stresses everything of course especially ignition. i would say your squiggles are consistent with (partial) ignition misfires. we solved this on my engine by changing (tightening) the plug gap a bit. other items would be plug boots that are not tight and worn plug wires as well as worn out coils. generally coils not up to the job just sign off at a certain rpm.

if you have misfires and are using AI the worst move is to cut back on AI, the right move is to crank up the spark.

good luck,

Howard

whizzybang

Thank you Howard that is perfectly clear. I was going to buy Magnecor spark plug wires anyway as one of my OEM boots doesn't hold tight to its spark plug.

One last question since we talk about it : is there an actual difference between Magnecor KV85, 8mm and 10mm wires ? With all othr ignition parts stock. I'm a bit confused here.