Coldside hesitation at the track

[mts]

I posted this on Miata.net, but haven't gotten any responses yet so I thought I would try here as well. I took my 1994 BRP Colside SC'd car to the track this past weekend and all went well except for an irritating hesitation or "hiccup" the car consistently had only at part-throttle around 5,000 rpm. I could "outdrive" the hesitation whereby in the couple corners where I would typically lift and go part throttle, I just drove a bit deeper and hit the brakes harder using the gas pedal as more of an "on-off switch" so I didn't get in a part-throttle situation. The car has the old BRP coldside MP62 set-up with a split-second extra injector pre-blower and a new PC-pro. The a/f's on the dyno look good although I really didn't do much/any part throttle work. The plugs are new, as well as the wires. It's going to be a couple weeks before I can get to the dyno and I am looking for some ideas.

Anyone else run into a part-throttle hiccup like this?

[mts]

For future posters, this turned out to be a fueling issue. I got it on the dyno and the split second unit had gone haywire and was adding WAY too much fuel. The big mystery now is it wasn't doing that before and I have no idea how the settings changed by themselves. I'll have to watch it and may have to replace it if it happens again.

[bogey]

What are your settings on the Split Second? I have been adjusting mine and am still not 100% happy. (It is pretty good now, but getting some stumble at 6K+)

I am only adding from 4psi on up. What is the "right amount" without dumping too much fuel?

Also, how can I switch between MAP A and MAP B? Can I haev two maps, changable for warm vs hot weather?

[bogey]

I found the part throttle stumble caused by adding fuel too early. It was originally starting at 0psi, and I have tried 2psi and 4psi. 4 seems best.

[Serpico]

What are your settings on the Split Second? I have been adjusting mine and am still not 100% happy. (It is pretty good now, but getting some stumble at 6K+)

I am only adding from 4psi on up. What is the "right amount" without dumping too much fuel?

Also, how can I switch between MAP A and MAP B? Can I haev two maps, changable for warm vs hot weather?


Interesting idea! I have 4 injector clips on my SpitSec controller and if I wanted to I could just load two different maps and switch them by using one of the other two injector clips that corresponded to the other map.

However, it's easier to just add a light or two on the PCPro when the colder weather returns. I think I'd rather add more fuel with the main injectors anyway.

[Kyp J]

Interesting idea! I have 4 injector clips on my SpitSec controller and if I wanted to I could just load two different maps and switch them by using one of the other two injector clips that corresponded to the other map.

However, it's easier to just add a light or two on the PCPro when the colder weather returns. I think I'd rather add more fuel with the main injectors anyway.


When I originally installed my E cool, the instructions on the SS specified 2 of the plugs were for a certain impedance injector and the other for another. Since I didn't know what kind of injector I just went with what was suggested (the ones for the A map).

Is it OK to switch to the other impedance driver with whatever injector we are using?

[chuckerants]

When I originally installed my E cool, the instructions on the SS specified 2 of the plugs were for a certain impedance injector and the other for another. Since I didn't know what kind of injector I just went with what was suggested (the ones for the A map).

Is it OK to switch to the other impedance driver with whatever injector we are using?

I think I remember calling Split Second to ask which I should use when I first got my SS just to verify. I think I'm using the right ones.

The other harness/MAP I'm using for my Aquamist.

[Tom @ Fast Forward]

Miata injectors and the extra injector I supply are high impedence injectors.

[bogey]

That begs the question - which pair of wires should be used?

If memory serves me right - I think they were red vs tan.

[Tom @ Fast Forward]

There is a set of wires that are solid colors and they go to map A. The wires with the stripe go to MAP B.

[bogey]

So which ones are high impedance vs low impedance?

[Tom @ Fast Forward]

Table A drives the injectors controlled by the Tan wires. These injectors can be either low or high impedance. Table B drives the injectors controlled by the Tan/Black wires. These can only be high impedance.

[bogey]

So either way I am good. Set Map A and Map B to the same program and all is well...

Right now I have ecool added at 4psi on up. The 4psi column runs from 1-5, ramphing up to the 10psi at 5-9, then flat on up.

I think this is too much fuel at top end. Seems to stumble at 6K rpm. I am considering changing from 1-3 at 4psi ramphing up to 3-6 at 10psi and higher.

When you tested ecool temperature drops, what levels were the SS controller using? What levels worked best?

[Kyp J]

So either way I am good. Set Map A and Map B to the same program and all is well...

Right now I have ecool added at 4psi on up. The 4psi column runs from 1-5, ramphing up to the 10psi at 5-9, then flat on up.

I think this is too much fuel at top end. Seems to stumble at 6K rpm. I am considering changing from 1-3 at 4psi ramphing up to 3-6 at 10psi and higher.

When you tested ecool temperature drops, what levels were the SS controller using? What levels worked best?


Sometime back, a highly techie sounding discussion was going on about injector on times and I remember trying to relate to it without all the complicated jargon. I think I calculated the entire intake stroke of one piston is only 4.5 milliseconds long at 7,000 rpm. I never figured out how a single injector's on time relates to that considering the next piston will be sucking in the next 4.5 milliseconds worth of air/fuel. But it depends on how often the injector is being pulsed by the control card which I never found out. Once per rev? Twice per rev? 4 times per rev? Then, what happens if the on time is longer than the pulse control rate (still on when it needs to be turned on again)?

Bottom line, I let Tom figure out what to set my SS to and quit thinking about it.

[Tom @ Fast Forward]

The SS pulses 4 time per revolution if you have it set for a 4 cylinder, 4 cycle engine.

The PC-Pro is also set to pulse 4 times/rev. If it was real short on fuel, I can set it to pulse up to 12 times/rev. I set my 99 to 5 times once and nearly drowned it. That was +25%. ;-)

[bogey]

The question still remains - how much fuel should the SS/ecool injector provide to get the cooling effect, while allowing the PCPro to manage the majority of the fuel?

How many milliseconds should the injector be open? Should it be a rising rate based on boost? RPM? or should it be flat across the ranges?

I don't think fuel should be added until boost is 3-4psi because it runs too rich on transition. Also, should it come on at low RPM? The controller starts at 500rpm and goes to 8K. Is it necessary to add at lower RPMs?

I will keep trying different levels, but I am hoping someone has already found the optimal settings. I really need an air intake temp gauge...