Danno

[quote]-wait a minute! I thought all 4 injectors DID fire simultaneously...?<hr></blockquote>From looking at the wiring diagrams, there's two injector drivers in the DME. Each one fires two injectors simultaneously, #1&3 and #2&4. As for the timing of these drivers, I would say that they're still functioning in batch mode. Although I've heard from others that they're staggered 360-degrees. Kinda like a semi-batch mode. Something in between batch and full sequential.

Not that there's much of a difference in performance between the two (this has been debated endlessly). There really can be a difference at idle & low-RPM. But at high-RPM/full-throttle where you make max torque/power, the only difference between the two techniques is when during the 720-degree cycle you squirt fuel onto the back of a closed intake valve. That's because at 40-80% duty-cycle on the injectors, you're already spraying full-time during the intake-valves open period anyway. The difference then becomes whether you take the 20% time that the injectors are closed in one chunk, or two 10% periods; all of which are when the intake-valve is closed, so performance differences are insignificant.

keith

so how does it make sense that you can swap the leads with no effect on the running engine?

(like when troubleshooting an injector)

Danno

I guess then the two DME injector drivers work in parallel and all the injectors fire simultaneously. Even if the #1 & 2 injectors were 360-degrees apart, mis-timed fuel would just sit in the manifold and wait for the next valve-opening to get dumped in; the actual fuel-volume won't change.

In real-life practice, having the injectors a little farther away from the valves actually makes more power. This provides more air-volume behind the valve to mix with the fuel and achieve better vaporization of the fuel.

toddk911

"I use my car mostly for the track, and I need top end, so I've gone to a simple K26/8 with the Jon Milledge system, which produces about 285 flywheel horsepower. For this, the stock fuel pressure regulator works fine. "

Does hp matter in this issue or is it only the air/fuel ratio? i.e.if you are running lean and need more fuel, you need more fuel, regardless of hp. Right?

Also, does upgrading to the 3bar FPR only helpfull if running in close to stock upgrades?

smokey

Horsepower is determined by the volume of air/fuel mixture you can get into the cylinder at a given rpm. If the mixture is too lean, or the timing too advanced, you get detonation, no matter what the horsepower.
If the amount of fuel being injected is determined from a simple rpm map, there will be insufficient fuel as the boost is increased above standard, and detonation will result. Aftermarket chips make the necessary adjustment to the fuel mapping, but the chip must be designed for the specific turbo.

Above a certain boost level, the chip can no longer program enough fuel because the FPR/injector combination physically cannot deliver enough fuel. This problem will occur above some specific flow/horsepower level (flow=horsepower). I have been assured by Jon Milledge that with a K26/8 turbo and his standard chips/shims/drilled cycling valve system, the 3 bar FPR is not required. I have some training in fluid dynamics, and his explanation made sense to me.

The key is that the entire system must work together. Providing more fuel than the chip/turbo combination requires will simply result in using more fuel than necessary, but will presumably provide some safety margin. The only correct way to determine the required fuel pressure is with a dyno and full metering of all the parameters involved. That's how Jon designs his sytems.

Anyway, that's my understanding, and I stand to be corrected if I'm wrong.

toddk911

Thanks Smokey.

Is there any software and/or hardware available to hook up a personal lap top and tweek the air/fuel? <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Danno

only if you buy an aftermarket engine-management system...

Kool

I have a 3 bar FPR and APE stageII chips. With the mildely jstted banjo bolt. I am fairly confident that my car can handle more boost. It only goes to 1.8 bar or a little more on the stock gauge. What is the best way to meter boost. Should I dive in and get a dual stage wastegate and adjust it from there or is there some better solution?

Danno

Shim your stock wastegate and get an electronic boost controller, like the Apexi AVC-R. Someone found a deal for $315.

Kool

When I shim the wastegate I need to take the jet out of my banjo don't I? So AVC-R will work with the stock wastegate? I didn't think that it would. Thanks for the advice Danno

Danno

Yes, remove the banjo-bolt restrictor (or put the stock one back one). The solenoid that comes with the AVC-R is much faster-acting than the stock CV. So you want to provide it with as much pressure as possible so it can manage the wastegate precisely.

Alpine951

Kool,

What is it that makes you fairly confident your car can handle more boost. I am trying to determine the same.


John

Kool

Anybody who knows better please set me straight about what I am about the following.

The Stage II APE chips are designed to handle more boost. They bump the fuel curve up. When you add in the higher pressure FPR you are increasing the amount of fuel in the combustion chamber even more. More then likely my car has more fuel then it can burn with the amount of air that it is receiving at the current boost level. So if that is the case I should be able to raise the boost and the car will run more efficiently.

Am I thinking correctly?

If I am right I hope that this helps.

Alpine951

I think the theory is fine. But I don't think you will know unless you do a dyno. The reason I asked the question is I am considering turning up the boost. I just put in a digital air fuel meter and a 3 bar FPR. I have a lindsey BE and the car is chipped. Problem is that in 4th gear doing 80mph if I bury the throttle the gauge only reads 0.75 volts. I think I should be in the 0.8 to 0.9 or higher to be safe. Now I am thinking I need to dyno the car with a real exhaust gas analyzer to find out for sure.

toddk911

Alpine, how much boost are you running?