24lb injectors
12-05-2013, 07:41 PM
#16
Rennlist Member
you need to talk to the ECU? 
I installed the 30lb injectors on the stock S4 system to better deal with the greater displacement going to a stroker. But, as i suspected it was a little too much fuel based on the restrictive intake of the stock S4. would love to try 24lb injectors, as they seem to be where i need to be based on expected HP and fuel air mixture goals. (right now, i have to be near 44psi to make it all run 12:1, before, at 320-330rwhp, i was 12.6:1 and running 70psi with a 19lb injector)
I installed the 30lb injectors on the stock S4 system to better deal with the greater displacement going to a stroker. But, as i suspected it was a little too much fuel based on the restrictive intake of the stock S4. would love to try 24lb injectors, as they seem to be where i need to be based on expected HP and fuel air mixture goals. (right now, i have to be near 44psi to make it all run 12:1, before, at 320-330rwhp, i was 12.6:1 and running 70psi with a 19lb injector)
12-05-2013, 09:56 PM
#17
Captain Obvious
Super User
Super User
The Linclon Mark VIII came with 24lb (blue top) injectors from the factory, I have a set in my '85. All the pushrod Mustangs only had 19lb units (orange top). The ones in that picture look like orange tops.
12-05-2013, 11:39 PM
#20
Rennlist Member
Kibort. 
When you change injector size, you change the amount of fuel that gets injected per millisecond of time that the injector is open (the pounds-per-hour number, but no one leaves injectors open for hours).
The LH knows how much air is going through the MAF, and knows how much fuel has to go along with that air (the often-discussed air/fuel ratio), so it knows how long to open the injectors.
Until you change the injector size, that is. It still thinks it is squirting a little fuel, but in fact it is a lot more. And just to confuse things, with a stroker there is a lot more air going through the MAF, which calls for yet more fuel, which means the already-close-to-max injector time just goes to 100% open, a garden hose in other words. The (predictable) result is too much fuel, i.e. a very rich mixture.
One way to compensate is to reduce the fuel pressure, which reduces flow, until the mixture is about right. Sort of like turning down the garden faucet, the sprinkler doesn't spray so hard.
You can get away with this sort of stuff with a race car, because you don't really care how well it runs outside of a fairly narrow range of RPM (4000-6000 or whatever), and wide open throttle.
A much better solution is to reprogram the LH with the correct injector-size, so when it calculates how much fuel is needed it will come up with a sensible answer. Back in the "old days" this wasn't possible, and lots of fiddling got done. Then John Speake and Niklas Kämpe came up with the Sharktuner, which lets you poke around in the LH brain and change stuff like injector size (and opening time, and fuel maps) so that the ECU works like it is supposed to, instead of just turning on a garden hose for a while.
Mark Kibort, for reasons which are not entirely clear, does not agree with this point of view. That's fine, no problem with that, but it is fun to tease him
Disclaimer: I sell Sharktuners for John, and I am probably biased...
Now back to the OP's problem: The Ford/Bosch 24# injectors work fine, but those aren't them. I would suggest either sticking with stock, and send them out for cleaning and flow-testing (e.g. Witchhunter or your friendly neighborhood injector-cleaning service)
And stop shopping on eBay for 928 parts !!!
When you change injector size, you change the amount of fuel that gets injected per millisecond of time that the injector is open (the pounds-per-hour number, but no one leaves injectors open for hours).
The LH knows how much air is going through the MAF, and knows how much fuel has to go along with that air (the often-discussed air/fuel ratio), so it knows how long to open the injectors.
Until you change the injector size, that is. It still thinks it is squirting a little fuel, but in fact it is a lot more. And just to confuse things, with a stroker there is a lot more air going through the MAF, which calls for yet more fuel, which means the already-close-to-max injector time just goes to 100% open, a garden hose in other words. The (predictable) result is too much fuel, i.e. a very rich mixture.
One way to compensate is to reduce the fuel pressure, which reduces flow, until the mixture is about right. Sort of like turning down the garden faucet, the sprinkler doesn't spray so hard.
You can get away with this sort of stuff with a race car, because you don't really care how well it runs outside of a fairly narrow range of RPM (4000-6000 or whatever), and wide open throttle.
A much better solution is to reprogram the LH with the correct injector-size, so when it calculates how much fuel is needed it will come up with a sensible answer. Back in the "old days" this wasn't possible, and lots of fiddling got done. Then John Speake and Niklas Kämpe came up with the Sharktuner, which lets you poke around in the LH brain and change stuff like injector size (and opening time, and fuel maps) so that the ECU works like it is supposed to, instead of just turning on a garden hose for a while.
Mark Kibort, for reasons which are not entirely clear, does not agree with this point of view. That's fine, no problem with that, but it is fun to tease him
Disclaimer: I sell Sharktuners for John, and I am probably biased...
Now back to the OP's problem: The Ford/Bosch 24# injectors work fine, but those aren't them. I would suggest either sticking with stock, and send them out for cleaning and flow-testing (e.g. Witchhunter or your friendly neighborhood injector-cleaning service)
And stop shopping on eBay for 928 parts !!!
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Kolll (02-05-2023)
12-06-2013, 12:08 AM
#21
Does the size of the pintle cap matter? I've got the drop in Ford A302's and the pintle cap is about 1-1.5mm shorter than the 928 stock. I transferred over all the o-rings but don't want to drop $50 for 8 new injector seal kits sets just for the little caps.
475hp/460lb.ft
12-06-2013, 01:31 AM
#23
Rennlist Member
Kibort.
When you change injector size, you change the amount of fuel that gets injected per millisecond of time that the injector is open (the pounds-per-hour number, but no one leaves injectors open for hours).
The LH knows how much air is going through the MAF, and knows how much fuel has to go along with that air (the often-discussed air/fuel ratio), so it knows how long to open the injectors.
Until you change the injector size, that is. It still thinks it is squirting a little fuel, but in fact it is a lot more. And just to confuse things, with a stroker there is a lot more air going through the MAF, which calls for yet more fuel, which means the already-close-to-max injector time just goes to 100% open, a garden hose in other words. The (predictable) result is too much fuel, i.e. a very rich mixture.
One way to compensate is to reduce the fuel pressure, which reduces flow, until the mixture is about right. Sort of like turning down the garden faucet, the sprinkler doesn't spray so hard.
You can get away with this sort of stuff with a race car, because you don't really care how well it runs outside of a fairly narrow range of RPM (4000-6000 or whatever), and wide open throttle.
A much better solution is to reprogram the LH with the correct injector-size, so when it calculates how much fuel is needed it will come up with a sensible answer. Back in the "old days" this wasn't possible, and lots of fiddling got done. Then John Speake and Niklas Kämpe came up with the Sharktuner, which lets you poke around in the LH brain and change stuff like injector size (and opening time, and fuel maps) so that the ECU works like it is supposed to, instead of just turning on a garden hose for a while.
Mark Kibort, for reasons which are not entirely clear, does not agree with this point of view. That's fine, no problem with that, but it is fun to tease him
Disclaimer: I sell Sharktuners for John, and I am probably biased...
Now back to the OP's problem: The Ford/Bosch 24# injectors work fine, but those aren't them. I would suggest either sticking with stock, and send them out for cleaning and flow-testing (e.g. Witchhunter or your friendly neighborhood injector-cleaning service)
And stop shopping on eBay for 928 parts !!!
When you change injector size, you change the amount of fuel that gets injected per millisecond of time that the injector is open (the pounds-per-hour number, but no one leaves injectors open for hours).
The LH knows how much air is going through the MAF, and knows how much fuel has to go along with that air (the often-discussed air/fuel ratio), so it knows how long to open the injectors.
Until you change the injector size, that is. It still thinks it is squirting a little fuel, but in fact it is a lot more. And just to confuse things, with a stroker there is a lot more air going through the MAF, which calls for yet more fuel, which means the already-close-to-max injector time just goes to 100% open, a garden hose in other words. The (predictable) result is too much fuel, i.e. a very rich mixture.
One way to compensate is to reduce the fuel pressure, which reduces flow, until the mixture is about right. Sort of like turning down the garden faucet, the sprinkler doesn't spray so hard.
You can get away with this sort of stuff with a race car, because you don't really care how well it runs outside of a fairly narrow range of RPM (4000-6000 or whatever), and wide open throttle.
A much better solution is to reprogram the LH with the correct injector-size, so when it calculates how much fuel is needed it will come up with a sensible answer. Back in the "old days" this wasn't possible, and lots of fiddling got done. Then John Speake and Niklas Kämpe came up with the Sharktuner, which lets you poke around in the LH brain and change stuff like injector size (and opening time, and fuel maps) so that the ECU works like it is supposed to, instead of just turning on a garden hose for a while.
Mark Kibort, for reasons which are not entirely clear, does not agree with this point of view. That's fine, no problem with that, but it is fun to tease him
Disclaimer: I sell Sharktuners for John, and I am probably biased...
Now back to the OP's problem: The Ford/Bosch 24# injectors work fine, but those aren't them. I would suggest either sticking with stock, and send them out for cleaning and flow-testing (e.g. Witchhunter or your friendly neighborhood injector-cleaning service)
And stop shopping on eBay for 928 parts !!!
the 02 sensor does an amazing job of regulating fuel at part throttle. during closed loop operation, a 30lb injector vs a 19lb injector is not that big of a deal. ((this is seen with looking at the output from a wide band 02 device)
at full throttle, the fuel pressure change techqiue tends to work pretty well. with the 5 liter , raising it up to 70psi, gave 12.5 safe and powerful fuel ratios. With the stroker, the 30lb injector was too much as i exected, and the 19, might not have been enough, proved by the high pressure i needed with the stock 5 litre displacement. Continuing to back down the fuel pressure with the higher displacement vs stock, and larger injector, got it in the acceptable range, not only for cruise settings, but WOT. not a lot of downside that i can see for the street, since its on the street quite a bit .
sure you can remap the system and run the risk of running lean if there are temp changes or other things not taken into account during the re-map.
anyway, my ecu cannot be shark tuned, so im left with a engine that is tuned via injectors and fuel pressure. Big deal. Bill ball has see it, riden in it and tested , and you have seen the dyno numbers . There is little that is left to be improved on now as far as power or drivablity.
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Kolll (02-05-2023)
12-06-2013, 02:13 PM
#26
Advanced
Thread Starter
Ugh, I know how stupid it sounds now, but it appears that these injectors are made by Denso and not Bosch. 
Lesson #2: Not everything with Jetronic connectors is Bosch.
Lesson #2: Not everything with Jetronic connectors is Bosch.
12-06-2013, 04:06 PM
#27
Rennlist Member
Jim,
Thank you for the explanation. I am still trying to get my AFR right after the supercharger installation (L-jet), and I would like to understand things as much as possible.
Mark,
Why can't your car be Sharktuned?
OP,
Sorry for going astray.
Thank you for the explanation. I am still trying to get my AFR right after the supercharger installation (L-jet), and I would like to understand things as much as possible.
Mark,
Why can't your car be Sharktuned?
OP,
Sorry for going astray.
12-06-2013, 04:37 PM
#28
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Let's not be so hard on Mark K. We did get Sharktuner to work for one short road session. His LH and harness are factory prototypes. So, as I recall we substituted my PEM-loaded LH and managed to find the harness lines with temporary patches and went for a drive. Sure, with some tuning time we might have found more HP, but based on what I saw, the mixtures were not bad at all with his current injectors and modified fuel pressure and the car was behaving well. Without a lot more tuning time than we had available I decided to leave things as they were rather than try to "correct" the fuel pressure and injector settings and try to retune the map and burn new chips. I did want to return when we had more time and a dyno session, but we haven't had a chance to do that.
12-07-2013, 01:32 AM
#29
Rennlist Member
So-- with apologies for posting back on the original topic-- did you swap the original injectors back in? Does the engine run OK? If not, then something else got messed up. Check for other connectors that might have gotten disconnected in the process.
If it runs OK with stock, but not the Denso's, then there is something different with the Denso's that isn't compatible. Return them or sell them.
If you can find a set of Ford/Bosch M9593-A302, new or used/cleaned/flow-tested then those will work well, or just get your factory set cleaned and flow-tested.
But if the goal is to perk up the car then have a look at Ken's chips for the 85-86 cars. They work with stock injectors or the A302's, but require swapping the the fuel-pressure regulator to the 55 psi S4 regulator. His website is http://liftbars.com
12-07-2013, 02:30 AM
#30
Since my thread appears to attract no attention, I'll address this here.
Can anyone tell me the o-ring size for the injectors? The Ford ones cannot be used since they're too small so I swapped out the ones on my original injectors. They're thicker but diameter wise, only about 0.5mm larger (i.e. They're 14.8ish). I'm reading threads that they should be 16mm in diameter. Original injectors were refreshed by my (old) mechanic who knows 928s. Either they're okay or he installed the wrong o-rings.
Can anyone tell me the o-ring size for the injectors? The Ford ones cannot be used since they're too small so I swapped out the ones on my original injectors. They're thicker but diameter wise, only about 0.5mm larger (i.e. They're 14.8ish). I'm reading threads that they should be 16mm in diameter. Original injectors were refreshed by my (old) mechanic who knows 928s. Either they're okay or he installed the wrong o-rings.