'90 Mazdaspeed Miata Rallycross Project

The fuel pump was also upgraded/replaced last season. Edit: Evan beat me to it.

EvanB wrote: the fact that it is worse with race fuel

What are your spark plugs gapped to?

EvanB wrote: ngk copper gapped at .030, stock msm coils/wires.

Took it out to do a log. It now sounds like a spark cut. I'm not sure if it changed or I am just thinking of it a different way.

What is DutyCycle1? Injectors?

Yes

The cut is right in the middle, you can see MAP and injector duty cycle drop and spark angle spike then O2.

Is 95.6% kind of high for injector duty cycle?

Probably. One thing I found out is the red vertical lines are a sign of interference. I'm going to try adding another ground or two.

Wouldn't the injectors just go up to 100 and stay open continuously rather than cutting out?

I'm not an expert, but I won't let that stop me from giving you my unqualified opinion... :D

When I was sizing the injectors for the Neon, what I remember coming up with was that if you've got duty cycles approaching 100%, you need a bigger injector. It could be fuel pressure is too low, of course, but I would think 95.6% duty cycle numbers would be more than just a few psi low. It also kinda seems like the pulse width is a bit high, but I'm not sure of that. The O2 voltage line seems to indicate that it's going a bit leaner. I'm also curious about why the CLT line seems to disappear and reappear on you. If MS stops seeing a CLT signal, it thinks that it's -40F outside and will try to enrich the heck out of things which could cause some weirdness, but my experience is that is just runs like poop no matter what you do until that signal is restored, not the other way around.

These just stock MSM injectors? Are you running the MSM pump/FPR?

It is a 99 fpr, I'm planning on getting an adjustable at some point.

Stock msm injectors, I know I need some bigger ones.

I believe the MSM ran them at higher pressures, but Keith would have to check me.

Possibly part of your problem.

Alternatively, i have a set of 330s laying around i could send your way for $20 or something. Came out of my MX6, so they're dirty and could probably use new o-rings and pintle cushion things, but that stuffs cheap.

I'm thinking more like 440s.

I'd jump to 460s then unless you know where to get high impedance 440s.

RX7 460s are plentiful on Miataturbo.

Oh yea, that's what I meant.

cghstang wrote: Is 95.6% kind of high for injector duty cycle?

You don't wanna know what teh RX-7 runs them at then

But then, I'm not running a piston engine which can melt pistons/valves if they run lean under heavy power, or a turbo engine which gets even more expensive when that happens... or worse, a piston engine with a turbo on it.

Knurled wrote:

cghstang wrote: Is 95.6% kind of high for injector duty cycle?

You don't wanna know what teh RX-7 runs them at then (:) But then, I'm not running a piston engine which can melt pistons/valves if they run lean under heavy power, or a turbo engine which gets even more expensive when that happens... or worse, a piston engine with a turbo on it.

I'm fairly certain the MSM runs them well over 100% as well.

I KNOW the MX6 does. Ever seen another 4 cylinder make 270whp+ on 330s? E36 M3's ridiculous.

Well it hasn't had a problem leaning out under full throttle. It is still at a safe afr up to the point it cuts out.

Do you have anything like the overboost protection on or something? I got some cutting out when I cranked up the boost a little bit and started bouncing off the overboost setting.

Hard to tell from the graph, but it does look like the advance is dropping right as the RPMs start falling off. Maybe increase the advance a tiny bit on the top VE bins? 1.34volts on a WBO2 should still be relatively to the safe side if I remember right.

The overboost protection is set much higher than the boost I am hitting. I think I have it set at 16psi.

Knurled wrote:

cghstang wrote: Is 95.6% kind of high for injector duty cycle?

You don't wanna know what teh RX-7 runs them at then But then, I'm not running a piston engine which can melt pistons/valves if they run lean under heavy power, or a turbo engine which gets even more expensive when that happens... or worse, a piston engine with a turbo on it.

It goes to 11...

Just re-read the entire thread. berkeleying awesome!

More action shots!!!

Swank Force One wrote:

Knurled wrote:

cghstang wrote: Is 95.6% kind of high for injector duty cycle?

You don't wanna know what teh RX-7 runs them at then (:) But then, I'm not running a piston engine which can melt pistons/valves if they run lean under heavy power, or a turbo engine which gets even more expensive when that happens... or worse, a piston engine with a turbo on it.

I'm fairly certain the MSM runs them well over 100% as well. I KNOW the MX6 does. Ever seen another 4 cylinder make 270whp+ on 330s? E36 M3's ridiculous.

300+ crank horsepower on four 330s is not ridiculous, it's impossible, unless you're running in the range of 70-80psi fuel pressure over manifold pressure.

Anything over 100% duty cycle just means the computer wants to open the injectors before it wanted to shut them, and it's just an academic number.

For example, my injectors go static somewhere in the mid-8000s. The air/fuel mixture goes too lean to ignite at about 9500, so it's a dandy rev limiter...