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L-Jet injectors

 
Old 01-08-2019, 03:47 PM
  #31  
ROG100
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I have done a lot of research to find a suitable replacement that meets the criteria along with being low impedance.
Either with the barb ends to take the hose or to be used with GB's adapters.
As a seller I am looking for a sustainable source for multiple sets.
I have found a number of alternatives but they are in very short supply or too expensive.
I like the idea of removing the plastic at the top to reveal the barbs but that adds labor to the cost. Ideal for the DIY owner owner.
928 Motorsports sells a set that look like they are modified for circa $700 so it may be better to stick with the originals and have them cleaned and hoses replaced by www.witchhunter.com or buy used from Mark at 928 International.
Alternatives are -----
0280 150 201
0280 150 158
0280 150 154
Lucas D1540BA
0280 150 364
0280 150 260
Do your own research to make sure.
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Old 01-08-2019, 03:49 PM
  #32  
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Hey umc,
Welcome back to your old thread! Well this is largely academic for me now, but the issue appears to be that nobody has found/tried/proven an injector that a) flows 24 lb/hour, b) has low impedance and c) offers an improved spray pattern over the original. Even ignoring whether an injector will or can be made to fit, my own research (and I admittedly know nothing about this stuff) has not turned up many candidates. In fact only one, a Lucas injector, and I have no idea if its spray pattern is any good. It’s called a disc-type injector. But it does flow 24 lb/hr and have low impedance. Here’s a link: https://www.fiveomotorsport.com/bosc...150360-jaguar/

Edit: I see Roger just beat me to it and is way ahead of me!
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Old 01-08-2019, 05:17 PM
  #33  
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I used Greg's adapters and 24lb injectors as recommended. Fitted in early 2015. Excellent results. Used type 2 24# refurbished injectors easily available and guaranteed on ebay

https://docs.google.com/document/d/1...JT-Zl2eAQ/edit

This is the ebay seller and the injectors I bought from him Bosch 0280150947 24lb
https://www.ebay.co.uk/itm/Bosch-Tur...CHQD:rk:3:pf:0

Last edited by murray928; 01-08-2019 at 05:26 PM. Reason: Additional information.
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Old 01-08-2019, 05:22 PM
  #34  
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Murray928 - different car and different injector totally. We are talking about USA 4.5L & 4.7L 16v cars which are totally different to your 84 to 85 S2 ROW 16v twin dizzy car - I wish it was that easy 8>)
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Old 01-08-2019, 05:34 PM
  #35  
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Sorry Roger. Didnt mean to incorrectly advise. Just recommending what I used to solve my problem as discovered on Rennlist. I defer to your technical expertise re differentiation between USA and ROW 16v engines.
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Old 01-08-2019, 05:36 PM
  #36  
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I wonder if it would be easier to modify the L jet ECU board to support the higher impedance injectors. I know there are folks on here that rebuild the the S4 ECUs, so the output circuit there must be well understood. Perhaps we can look over the L jet circuit and either come up with a change or analyze the circuit to show the higher impedance parts are ok. Does anyone have info on the L jet circuit? I have a great analog/power circuit guy on hand.

In general most of the time circuits can handle going from a low impedance load to high much better than the other way around, but there are lots of variables.
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Old 01-08-2019, 05:50 PM
  #37  
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Originally Posted by karl ruiter View Post
I wonder if it would be easier to modify the L jet ECU board to support the higher impedance injectors. I know there are folks on here that rebuild the the S4 ECUs, so the output circuit there must be well understood. Perhaps we can look over the L jet circuit and either come up with a change or analyze the circuit to show the higher impedance parts are ok. Does anyone have info on the L jet circuit? I have a great analog/power circuit guy on hand.

In general most of the time circuits can handle going from a low impedance load to high much better than the other way around, but there are lots of variables.
Read post #29 from The Forgotten On and this thread:
https://rennlist.com/forums/928-foru...dance-car.html

As I've posted in countless threads, the issue with load is you can go one direction but not the other.
Putting low impedance injectors in an S4 will most likely fry the brains. A high impedance injector with a low impedance driver, it will just see less load, which won't hurt anything.

Injectors are stupid, 12V they click open. L-Jet brain supplies 12 volts when it's time to spray fuel. As long as you don't overload / overhead the injector driver, you'll be fine.

I'm preparing to install 85/86 injectors in my 80 with modified S4 fuel rails. Only reason why it hasn't been done yet is I'm still putting the body / interior back together, a bit behind schedule.

So....let's wait for some real world testing before trying to totally reinvent the wheel on this one.
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Old 01-09-2019, 08:45 PM
  #38  
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Yes. That is also what I said. But as an electronics guy I can also tell you it could possibly be more complicated. The first question in my mind is 'why did they use low impedance injectors on the L jet 928?'. Here are a couple of possibilities:
1) That's what they had / they could get them cheap.
2) The magnetics in the early injectors were not as efficient so they need more current to do the job.
3) They wanted faster opening times, and so wanted higher current, and so needed lower impedance.
4) They were worried about noise and higher impedance circuits are more susceptible to noise.
5) They were doing something different with the injector circuit-wise than is done on later injection systems.
6) They were worried about the total impedance stack up of all the connectors plus the injectors rising over time as the connectors corroded.

I do seem to remember that on my L-Jet 914 the injectors did not have one side going to ground or hot as I think later systems usually have, but instead they went to hot via some series resistors. I don't recall if I saw these on my L jet 928 or not. Why did they use series resistors on some or all L-Jet cars? Some possibilities:
1) They could only get low impedance injectors but they did not actually want to use all that current.
2) There were inductive effects of the injectors (ringing, overshoot, etc) that they were worried about and they used a RC to damp them out.
3) The circuit actually measured and controlled the current going through the injectors by tapping into the point between the series resistance and the injectors.
4) They were worried about a short in an injector cooking the harness or the ECU.

Anyway, my point is that it may not be as simple as low to high is always ok, and if the details are available it might be worth looking at them so that we could have something more definite than 'well I tried it and it has worked so far'. Nothing wrong with that for me, but its probably not an answer that people like Greg are gonna buy into.
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Old 01-09-2019, 09:43 PM
  #39  
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I suspect that the low impedance design was just what the older engine management did, before the high impedance injectors were designed. It wasn't only Porsche, you can find them in Nissan, Subaru, Mazda, etc...
A little later on, the manufacturers went to high impedance, possibly due to advances in the injector design, or possibly in technology and understanding of how to control and drive them.
The switch to high impedance also lowered the current flowing through the ECU significantly, reducing the resistance heating effect, as well as required wire gauge. I suspect that the reduced wire size is a large part of the decision, based on how marginal many manufacturers have gotten with wiring barely meeting required current flow when new, in the interest of saving pennies per vehicle built.


Many of the low impedance ECUs are designed using "peak and hold" control, so that they don't get as hot as they might otherwise, but most still have resistors in series with them, to limit max current draw.

Regarding the wiring path, common/ground switching is fairly common on cars, but either way works, just depends on which way the ECU is wired. Per my company's electrical engineer, design is simpler for a common switched output, since you just have to provide a ground path, and can use any voltage (as long as it is less than the max of the switching IC being used.)

There is a huge amount of information on this over at the MegaSquirt ecu site, but it goes way out into the weeds in detail, and often down a rabbit hole. So, what were the actual reasons for the engineers doing it one way or another, who knows...
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Old 01-10-2019, 02:29 PM
  #40  
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Much useful L-Jet info here:
https://www.alfabb.com/bb/forums/alf...tor-l-jet.html
Camelo says he will try Bosch P/N 0280150440 which are:
23.8 Lbs/Hr
250.1 CC/min
179.9 grams
50.75 psi
3.5 bar
16 Ohms resistance
(Looks like type that has a plastic top with barbs under.)

His last post was 10/10/16, unfortunately no result posted of his trial.

Also, this is relevant:
http://performancefuelsystems.com/In...TechCorner.htm
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Old 01-11-2019, 05:38 AM
  #41  
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^^ Those are high resistance. You should be able to run them just fine.

I'm sure that if a 944 dme can handle it, the 928's can as well.
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