Were the staged injectors sequentially fired too? As far as I know even the MS1 has two channels to drive injectors, but to run staged injection they have to be wired in as batch fire. So the regular injectors are batch fired and when the pre-programmed condition to turn on the second set was met they'd kick on as batch fire. I haven't tried it, but the MS staged injection can be tuned to be all on or all off, or be gradually brought in because the second channel runs it's own fuel table, so the second stage can be ramped in. My dual MS3 example was having both the primary and secondary injectors running sequentially.
Yes, the staged injectors on the BigStuff3 was fired sequentially so each cylinder could be individually tuned. So if you used two MS3 units, one to power one set and the other for the second set of injectors, what would the fuel tables in each unit look like in order to accomplish staged injection? Paul
Way cool, now that's powerful processing! With them CAN linked together reading the same set of sensors (I'm pretty sure my friend has done this for different reasons), the first MSIII fuel table would simply be set up normally, and when you wanted to cut back the duty cycle at X load and Y RPM then you'd simply set the fuel map accordingly, then with the second MSIII the fuel map would be zero'd out below the X load and Y rpm you don't want it running and then come on when that X load and Y RPM are reached. Of course you can have the fuel table on the second one gradually come in too. If I were at home I'd quickly build the two tables and print screen the example, but for now this is what I pulled from the Megamanual. This would be an example of the fuel table for the second MSIII (or simply the second table if batch fire was okay and one MS). Notice it starts at 4,000 rpm for this particular engine and all the values below that are zeros. This shows a second fuel table so it is displaying the logic too of when to kick it in, but for a second MSIII it would be a simple primary fuel table with the lower values zero'd out. (I couldn't get the picture to display, but the link works) http://www.msextra.com/doc/ms3/img/stagedsettings.png On the MSEFI forum, one of the principle programmers responded to my question with this. Current version is 1.0.5, so it could be in the works. This answer was to a staged injection question (batch fire), about reducing the duty cycle of the primary injectors when the secondary ones kick on. Apparently it's possible. In the two MSIII scenerio we are hypothezising, it wouldn't be that complicated, just simply lower or flat line the fueling of the primary MSIII's fuel table above X load and Y RPM, in the area that the second MSIII's fuel injectors are kicked on.
The Accel Thruster, Gen 7 and FAST XFI will do the same. The Accel also allows you to do individual cylinder trim even in batch.
According to Accel's DFI Gen 7: It still only has 8 injector logic outputs. Near as I can tell it still has to be batch fired for staged injection above 4 cylinders. After hitting a dozen or so websites looking for info on the Accel systems, I can completely agree with you Mark on it being a great bang for the buck. Do those universal wrapped GM V8 harnesses reach the Buick distributor in the front of the engine?
And damn you guys, you almost have me convinced to go sequential on the Skylark..... Stupid peer pressure :spank:
If your goal is to maximize gas mileage then sequential will definitely help. Maybe we were just being sneaky in steering you in that direction. Whatever the case it is good to be able to share ideas and work on them together. When staging injectors you don't want to bring a second set in gradually because the goal is to stay away from short pulse widths. Most injectors minimum response time is just over 1 msec and are more linear after 2 msec. These injectors are expensive but they have found a way to stablize the injectors at short pulse widths. http://www.injectordynamics.com/ A set of ID2000s where used on a Buick straight 8 project where the maximum pulse width had to be 5 msec. There was no problem with idle. It appears that the Holley Dominator EFI may be capable of sequencial staged injection with 8 injectors? I couldn't determine by just reading the websights if any other company offering a unit under $2000 could stage all 8 injectors sequencially by having 16 separate injector drivers or 8 drivers that could drive 2 injectors each with switched grounds. Paul
Jim If you are expecting 500 hp you will need at least 42lb injectors The BSFC for a blown engine is at least 0.60 500x.60/8x0.8 = 47 lbs/hr @ 43 psi fuel pressure. Yes, the ego thing has blocked many great ideas from becoming a reality. It has also caused many new companies to be formed by the creative people that wouldn't quit on their idea. I'm not suggesting that here but given the finances, there are a ton of ideas that need exploring. Paul
But you can wire 2 injectors per set, it will run 16 total. BS3 will run 24, that's why the alcohol drag racers like them. But with an Accel for a Buick you just run a Ford style main harness with a GM injector harness. I am currently doing a project for a local marina. They use a MEFI V for Mercruiser 502 BBC with blowers. They run real rich, especially in the rear cylinders. They run 12 injectors. We're going to do the same, 4 in the blower hat and 8 at the ports. It will run in sequential with no issues. If we had 16 we could stage it but in this case that doesn't provide any real benefit.
Mark So if I read you correctly, the software supports staging, meaning the user gets to input a duty cycle percentage value somewhere in the set-up and when the first set of injectors reaches that percentage duty cycle, the injector pulse widths going to the drivers are cut in half and an output is available to activate the second set of injectors? I really would like details. Right now we are doing a blown methanol 7 liter BBC hydroplane in the vintage class and it needs to be just the way it was 50 years ago with Hilborn mechanical injection. But the 2 projects after that will be EFI and I will need to decide on which system to use. Thanks Paul
So let me see if I understand what is going on here. Basically we have a bunch of drag racers driving development with no real consideration for street use? That's OK I guess, if you're a drag racer... which I'm not. Be happy to show you the way up and down a mountain though, and efi is just the thing for that. Jim
Jim You lost me here. You didn't reference to any previous statements. It always seemed to me that EFI development was for the street enthusiast first and the drag racing group had to ask for all the bells a whistles needed for competition and it is finally being added to the systems at this late date. Please elaborate Paul Did you see my response for injector sizing in post #48?
Thanks Paul, somehow I totally missed that. Good to know definitely and I much appreciate the advice. Jim
You guys are worrying about staging multiple injectors and I'm here trying to figure out the best way to run a crank trigger without it being expossed to the environement. I guess I need to get caught up to the big boys before I'm totally on my own :laugh:
I'm telling ya, tens of millions of cars run with a crank trigger exposed to the environment. It's a non-issue.
Like The Silver said. If you run a magnetic type of trigger, either Hall Effect or a simple coil pickup, they are impervious to environment. The whole discussion with staged injectors is to have an injection period short enough so you can pin point the time of injection to maximize fuel mileage and power even with a large duration cam. Have you decided on a system yet? Paul
And that can change wth rpm and load, not all systems allow you to alter the injector timing under those conditions. Same with cylinder to cylinder trim.
Mark Yes. Because an injector has a minimum response time and depending how far the injectors are from the intake valves, the lead time needs to be increased as rpm increases in order to hit a specific injection point. However the shorter you make the injection period the less problem there is staying within a specific window of time and at high rpm and high load you probably aren't concerned about fuel mileage anyway so staying inside the window is not a problem. Did you get a chance to find out the specifics on staged injection for the Accel system? Can two sets of 8 injectors be staged while operating in sequential mode? Also since you brought it up, in sequential mode, can the injection timing be programmed along with timing changes based on rpm and load using the Accel system? Thanks Paul
