Z

I haven't personally ever seen it on any 928, including ones that were boosted by different methods, or strokers that were using the stock ECUs. I have seen instances where there were different resonance issues causing problems, but those were due to modifications or issues with things other than the stock ECU or fuel delivery systems, even when 42lb or larger injectors were used. The resonance mentioned in this thread really shouldn't be due to any inherent issue of the 42lb injectors or the firing of them by the LH computer. As has already been mentioned, coming up with a device to try to convert the batch fire system to a soft of sequential system would probably be kind of involved if made to the level required to make it work as well as it really should. Even then, I'd have to wonder if it was the best, easiest, and most economical method to eliminate the problem that's being seen.

I have an aftermarket ECU project that I started, and haven't touched in quite a while, that's intended to be a direct plug-in replacement to a stock harness.
Are you talking your '91, or the '85? I initially intended to configure things for use in an '85-'86 car, but it could be done for the later cars too. If you're talking about the '91, personally, I wouldn't do it if I were you though. In some ways, I really feel that switching away from the properly working and tuned later stock stuff, would be a step backwards.

I've thought about making a coil on plug ignition setup to work with the stock EZK/EZF, but haven't done anything with that idea yet, beyond the theory of operation stage. Even if I did build it, it would just be for the tinkering and curiosity aspect of it. On the vast majority of cars, I wouldn't expect it to gain any horsepower over a properly running stock two coil system. My car runs fine with the stock stuff and the piggy-back computer I installed over a decade ago. I don't see any real advantage in me changing that anytime soon, which is why I haven't been in any hurry with either project. At this point, the only change I'd probably do, other than for goofing around purposes, would be to remove the piggy-back computer and tune the stock engine management stuff with something like the SharkTuner.

I'm not questioning anyone who has said that they installed an aftermarket engine management system, and that it resulted in the car running better, or making more power. A properly running and tuned stock system will give you the same results in most cases though. That's with the later LH/EZF/EZK systems. Earlier stock ignition and L-Jet or CIS systems do have limitations that will end up becoming more significant issues if somebody wants to do something like add boost. That's why we replaced the L-Jet and stock ignition system on Hacker's '81 with the LH/EZF system from an '85, installed 42lb injectors, and then SharkTuned it when he went up to 20+ psi of boost. Up at that point, there were other things that become more of a limiting factor than that stock '85 engine management system that was installed. There's more than one 928 out there making more than 600rwhp with just the tuned stock engine management system, and it seems to be working well enough for them.

The aftermarket engine management systems don't do anything magic. They switch injectors and ignition coils on and off. That's all. If you were quick enough, you could do it manually with a toggle switch for the injectors, and one for each coil. There have been engines around for at least the better part of a century that seemed to work okay and made more power than any 928 engine, without using any ECUs at all, just carburetors, mechanical fuel injection, points distributors, and magneto ignitions.

Electronic systems do give greater control, but do you really need anything more than the stock ones provide in most cases? In the past, I've seen people who mentioned wanting a newer ECU, with a newer, faster processor. I'm not sure why. I've simulated over 26,000 RPM into the stock LH computer, and it didn't seem to have any problem with it at all. The stock dual coil ignition system is very good as well in my opinion. Out of curiosity, I did once try to measure the maximum voltage that one of the stock coils was capable of delivering. I never did find out though. The coil started the spark gap tester that I was using on fire and melted it before I reached the limit of the coil. All an ignition system needs to do is fire the spark plug at the right time. Anything beyond that is overkill, unnecessary, and is often just marketing that doesn't do anything more other than add cost and headaches, especially when compared to a properly functioning stock system.

Yes, modern vehicles use sequential injection, but not for any sort of real power increase. I've read that the main reason for it is for OBD-2 compliance. On some vehicles, it can also help give minor increases in fuel efficiency, in small low RPM and light load areas. That can really depend on having injector size and flow pattern, cam timing, valve geometry, intake geometry, and who knows how much more all designed to work together to take maximum advantage of it. There may be some additional power available by tuning each injector individually, but don't expect much. Doing it optimally would also require monitoring each cylinder's air/fuel ratio individually, tuning each one at every different RPM, and load point, and under controlled conditions. Plan on spending some time on it if you do decide to try it. A lot of time. Oh, and if you do it on a dyno, don't expect it to be the same under actual driving conditions, and don't be surprised when it's different in each gear. Of course it can all change again if you go to a different gas station, or even the same gas station on a different day. I did some gas testing from a couple of different gas stations, and from different pumps from each station recently. All I'll say about that is that anybody who thinks that they can fully optimize any sort of fine tuning like this in the real world is mistaken.

No offense intended to anyone here, but from what I've seen, that level of of sense and understanding really is much less common in the automotive world than a lot of people might think.

AO

Probably the 85. It has the greatest need IMO. Let's get it on. Spring build in GB?

hans14914

Starting to get a bit off topic, but I dont really see the advantage of moving to COP with the stock management system. The factory ignition system works great, and I dont think it will ever be the limiting factor when still controlled by the LH/EZK combo. At any rate, the hardware developement reqiured would be more expensive than just swapping over to MS3-Pro or VEMS... so at that point just replace it all.

I did happen to evaluate all the COP units that would work with our car. I have a bucket here with probably 20 different coils. The Cayenne coil still is one of the nicest, but the connectors are impossible to get in the open market. After going through them all, the there is an Audi 2.0T FSI coil which would work well with a new boot. I have the boot designed, and necessary modifications for installing it take less than a minute per coil. After, it is a perfect fit, and the plugs are commonly available - even on Amazon.

So, if someone wanted to develop such a system, I could help with logic-level coils.

On the resonance issues, I know that is somewhat common to just increase the line pressure and adjust the fuel map accordingly. The shorter opening times and higher pressure seem to shift the resonance into an area where it becomes less problematical. I recall their being a "white paper" issued by Kinsler on the subject a while back.

On another note, I happen to have a set of S4 headers here with test ports installed in all the runners for per-cylinder data collection. if someone wanted to measure EGT and WBO2 data along all cylinders to see what the differences really are, I would gladly lend them out.

Regards,
Hans

slate blue

All good points Carl, I would add to this that if you have the early style injectors that came on the euro S2 and I can't see the S4 injectors being any better. The spray atomization is dreadful, no I am wrong, it is non existent. I changed one of the cars years ago to the 4 spray hole injectors and I can only see OEMs further upgrading before they go to direct injection. So if you change the computers change the injectors. Note some aftermarket ecus have knock control such as the OBR Euro 8.

BC

Hans - how much are the coils you designed that donut for?

victor25

OK boys and girls, Here you go


More to come soon... I will tidy it up the install, and do a little fine tuning next week.
I just wanted to show that it could be done with minimal input.

victor25

I will post a nicer video later this week of the car running at different rpms, and with the wires all cleaned up. I cant drive it yet because we have too much snow here.

Does anyone have any flow data on the stock intake? I would really like to put that data to use and adjust the fuel rates to match the flow data if someone has that.

ptuomov

I recall that the injectors fire in two cycles, four each cycle. Someone should be able to confirm or deny this. Except now I am seeing Jim Corenman saying it's once for all eight.

My naive self would say that installing some fuel dampers to the rail would get rid of the resonance with about 1/100 of the cost and aggravation of a new ECU. You can install those anywhere in the rail, I think, and get most of the benefit.

I think that the larger injectors do cause a stronger pulse even if the same amount of fuel leaves the rail, because the fuel exits at a higher flow rate for a shorter period.

There are no real gains from sequential firing for our cars at the top end. The injectors are open for a long enough duty cycle that when they officially open and close doesn't matter.

Individual cylinder fuel trims would be nice, but 99% of the people who currently use the Sharktuner (excellent tool) don't have the needed instrumentation to do anything intelligent with the individual cylinder fuel trims.

Ducman82

are you using the stock cam sensor on the later S4 engines for the signal?

victor25

I agree that dampers would help immensely, and the system has one of the original dampers on it. I am almost done changing the setup to include both original dampers, with front damper location, and original flow through design.

This is a totally separate project from that resonance now. This will allow for individual cylinder fuel trim ability. Which should increase HP and fuel efficiency at lower rpms, but also allow us to really dial in cylinders to for the crappy stock manifolds.
As you know all the cylinders just don't flow the same, but all get the same fuel. Now we can get them all exactly at 14.7 instead of two at 14.2 and six at 14.9.

victor25

I am not using any sensors, using the stock pulse for everything. The stock pulse tells me exactly how long to fire the injectors, and the space between pulses tells me what the RPM is.

I have multiple inputs on the board though. This will allow for much much more abilities and options down the road

ptuomov

It's more likely two sets of four that flow differently and the difference depends on the rpms.

victor25

yes I realize that would change with the rpm, and they would probably trade places with rich/lean. I may just have to use exhaust gas temp sensors and take a bunch of readings