Guest DaneL24 Posted April 10, 2003 Share Posted April 10, 2003 I have a plan for using the stock EFI on an L28ET and using progressive Hobbs switches and extra injectors for gradual enrichment as boost increases. Several injectors would be mounted in a spacer between the intake manifold and TB, and those injectors would be activated one by one with Hobbs switches at different boost levels. Then I could get an A/F ratio gauge and tune the boost levels that each switch is activated. The injectors would be small, and there would be many, so the incremental enrichment could be more gradual. I also figure that the manifold should be able to distribute the fuel mixture well even though it is MPEFI, because it is designed to carry gas from the cold start valves all the way to the head anyways. The Hobbs switches also have to be adjustable for a wide range of PSI for this to work, more than 10 PSI hopefully. If they aren't adjustable enough, I have an idea for fabricating my own switches with adjustable boost pistons and circuit breakers. I just want to know how adaptable Hobbs switches are and if anybody has had any success working with them. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 10, 2003 Share Posted April 10, 2003 I used a Hobbs switch to turn on the water injection at a certain boost level on my carb'd turbo L24 I used to have. The switch wasn't cheap, and it blew out when my car backfired once. IMO, you are going the wrong direction. Save your $, and get a programmable ECU. You are going to spend over $100 on switches, injectors, and other stuff to get this CF working. Plus you need to drive the injector in a peak and hold fashion. If you just connect +12v to the injectors, you will burn them out for sure. If you feel like tinkering, you can build a Megasquirt for less than $200, and be done with it: http://www.bgsoflex.com/megasquirt.html Just trying to save you aggrivation I have already experienced. Pete Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted April 10, 2003 Share Posted April 10, 2003 The plan for driving the new injectors would be to run wires off of the current injector wires to the auxilary injectors, so they would use the same power source as the regular injectors and have the same pulse width. It would simply be a series circuit instead of a single circuit. I didn't know hobbs switches were so expensive. The Megasquirt does look pretty good, but I would just like to swap the stock ZXT ECU into my 240, so I can have both fuel and ignition control. The progressive hobbs switches are just to allow the turbo to boost at PSI levels too high for the stock computer. Aftermarket injection may be the answer, but I'm just looking at my options, and I'm pretty sure I could make a very adaptable system with hobbs switches. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 11, 2003 Share Posted April 11, 2003 You can't just add more injectors in parallel wit the existing ones. The resulting impedance will be too low, causing either the injectors, or ECU to overheat, and possibly get damaged. With an aftermarket ECU, you can ditch the air flow meter, and a lot of other stuff that is really not needed in a 240Z. I'm running an aftermarket ECU in may car. It gives me total control over triming and fuel. Best $1200 I ever spent. Pete Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 11, 2003 Share Posted April 11, 2003 Just like speakers, impedance is important. Too little, as said above, will cause the injector drivers to burn out, just like happens to folks who put low imp stuff on high imp cars Although, then I suppose you could theorize of 12 high impedance injectors being used, but I dont know that they would still put out enough juice to dump as much fuel as you'd think would come out. If it were this easy someone probably would have done it, and I haven't heard of it myself(?) Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted April 11, 2003 Share Posted April 11, 2003 I didn't know you couldn't wire the injectors that way (I didn't consider the impedence). Thanks for letting me know. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted April 11, 2003 Share Posted April 11, 2003 I'm not big fan of additional injector either. Unless I can get 6 extra injector on the manifold be cause I don't think the #5 and #6 will get as much fuel as the rest. My car suffers heat on #5 and may be #6. So I don't know how well it helps. 10psi on 78 ECU with turbo injector seems fine until 5500rpm. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 11, 2003 Share Posted April 11, 2003 I'm having good luck so far with 370cc injectors using my Z31 computer. I've upped the boost to 12 psi so far, and it is driving as well as it did with the stock injectors. What I did is not plug and play, but you seem to have an ambition for tinkering like me. I cut out the MAF element and installed it in a 3-1/2" intake pipe, then bumped my fuel pressure to 45psi. What I am currently planning on doing is adapting the MAF from the Z31 to support 370cc injectors, and sell them, just like Granatelli does with Ford stuff (a recalibrated sensor for larger injectors.) Then folks won't have to fab a new intake. Conceivably this can work with larger injectors as well, like 420cc and 450cc; this should just be a component change in the MAF. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 11, 2003 Share Posted April 11, 2003 For some cars there is something called the MAFT, the MAF translator. Its a MAF with a built in rheostat, usually for blown cars etc, kind of ghetto tuning but if it gets the job done, then... An intake manifold design effects air distribution, and generally a factory unit is just never going to distribute evenly. Individual injector tuning would be neat, if you were using an EGT or something fancy to monitor everything, but in general just being able to have some adjustability would be nice. I may look into the Megasquirt again sometime in the future. Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted April 12, 2003 Share Posted April 12, 2003 I think I found a solution. What if I wired the extra injectors straight to a 12V power source with a dropping resistor inbetween, just like the injectors usually are? There would be no signal from the ECU, so the injector would just stay open once its activated by the Hobbs switch. Maybe I could even figure out a system with a magnetic trigger to fire the injectors, like an attachment to the cam sprocket. As far as manifold distribution goes, I've got another idea. I could use the intake manifolds from a L24/L26 (since they are designed for even distribution) and modify the SUs for TBI, like a spacer inbetween the manifolds and SU TBs with the injectors in it. For the SU's, I would disconnect the floats/plug up holes and modify the air pistons to rise with boost instead of with vacuum (or just permanently lift the air pistons since they won't meter gas). So what do you guys think of these ideas? Have I found a possible solution? Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 12, 2003 Share Posted April 12, 2003 They would stay open constantly would they not? Sounds like they would overheat. 82+ cars have no dropping resistor FWIW. Why are you so resistant to spending a little more to get Megasquirt working, and not having to fabricate second fuel rails and hack job parts thrown together? If you have the know how it shouldn't be much more "work" other than getting it tuned, which should not take too long if you know what your doing. Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted April 12, 2003 Share Posted April 12, 2003 I like the idea of a Megasquirt system, and I'm still considering it...but there are a few things holding me back from it. From what I understand, with a Megasquirt I have to solder the ECU together. I know its feasible to do, and that people have had success with it in the past, but I don't have experience with advanced electronics projects like that, so I can't be certain that I will solder everything together right so the ECU will work. With a stock ZXT ECU, I can already be certain that it will work, and not only control the EFI, but the ignition as well. So when I increase the boost, I simply need an adjustable and tunable system to add the extra gas necessary for the engine at higher boost levels. That is why I like the idea of using the Hobbs switches, the certainty of using an ECU designed and built by electrical and computer engineers vs. something I soldered together myself for the very first time. As far as the dropping resistors go, they will be from an early 280Z. They don't need to be dropping resistors for the ZXT ECU, because the wiring for the extra injectors would be completely separate from the ZXT ECU. As far as overheating due to constantly open injectors...thats why I suggested the possibility of a magnetic trigger, so the injectors would open and close. Maybe I could even rig up a fan for extra cooling. The magnetic trigger wouldn't affect pulse width in proportion to VE like normal injectors, but it will still open and close them at the same rate as the engine RPM, and the system would still be adjustable through Hobbs switch adjustment, injector sizing, and fuel pressure; so the fuel mixture wouldn't be completely wrong just because injectors pulse width doesn't change as VE changes. And remember, all of this would be a piggyback system to the stock ZXT ECU, so if I have to I can drop the boost down and just use the stock electronics if necessary. Does that clear up why I am so "resistant" (which I'm not, I'm just looking at my options) to using a standalone EFI system? Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 12, 2003 Share Posted April 12, 2003 How much power are you looking for here? Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted April 13, 2003 Share Posted April 13, 2003 However much power the motor can handle...I would be happy with 300 HP eventually. I just want to be certain that the car will run well in stock form and at the same time be able to turn up the boost and add the necessary fuel when I start tuning the motor. Thats why I like the idea of a system being added to the stock ZXT ECU, the stock ECU will keep the car running well, and as soon as the CFM requirements of the motor exceed the capabilites of the stock ECU, I start adding fuel by other means...ie. extra injectors. I also like the idea of a RRFPR, but I'm working with other ideas as well...thats why I posted this. As for the Hobbs switch system...I was looking at the diagrams for the early EFI and figure it would be a lot easier to use cold start valves than extra injectors. Thats because while I can use the dropping resistors to control the power to the injectors, I need the ECU for the injector opening signal. Not the case with the cold start valves though, they are just run from a 12V source (with FP relay) and recieve an opening signal from the thermotime switch, a lot easier to mess around with than the ECU. Now I just need to learn a little more about cold start valves and thermotime switches to come up with a better plan for the switches. I don't know if the cold start valves simply recieve an on/off signal from the thermotime switch or if they have variable power. I also don't know if the thermotime switch just changes resistance based on temperature, so I could somehow figure out a way to place a variable resistor between it and the grounding point (to adjust the signal in proportion to boost). I see your point about using the Megasquirt, but I have reasons for my plan as well. I'm not about to make any drastic decisions right now either. I'm fixing up my 240Z right now and plan to install an L28ET in it over the summer. Its a few months down the road still, but I'm getting ideas right now, and thats why I bring it up. Comprende...? Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 13, 2003 Share Posted April 13, 2003 The cars can make 300 with an injector upgrade, your IC, turbo upgrade, etc, and should not be too rich at idle. Its beyond the 300 HP mark that things get exotic. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 13, 2003 Share Posted April 13, 2003 I made 300hp with stock injectors and the Z31 ECU (stock fuel pressure, nothing fancy). That's crank hp (assumed driveline losses for 260 rwhp), and I was starting to run lean on the top end. I expect to make a bit more now with just 6 370cc Merkur injectors ($7.00 each) and my MAF installed in the larger intake. I also got an adjustable FPR, and will need to run about 45 psi fuel pressure. So far it's running smoothly, and I just need some time to ease up the boost to confirm everything is kosher. That should be a SAFE 350hp with stock electronics, and possibly upwards of 400 hp for 350 rwhp. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 13, 2003 Share Posted April 13, 2003 I'm looking to get some of those Ford injectors, did you go to a yard? Wondering how you got them for $7 each. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 13, 2003 Share Posted April 13, 2003 Yep. Pull-N-Save. There have been 1 or 2 of the cars per week, at least last year when I was pulling them. Any Tbird turbo, Cougar turbo, Mustang SVO or Mercur XR4TI has them - make sure you get the ones with the brown tops. Quote Link to comment Share on other sites More sharing options...
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