john gill

You all need to remember that at WOT all these engines run way too much enrichment, so all in all it may not be a problem .

Kuba

Are these a possible source for 24# 928S4 injectors (for porken chips)? http://www.blueovalindustries.com/engine/en8810kit.html

It looks like they have the right slot and connector but no mention if impedance.

jcorenman

Those are Ford Motorsports M-9593-LU24A, the impedance is OK (11-12 ohms) but the latency (opening-time) and flow characteristics for each type of injector are different. For a custom tune (e.g. Sharktuning) they would work fine (provided there is clearance for the connector-adapters, it might be batter to rewire the injector harness with the EV6 conenctors).

To answer the question of whether these injectors are suitable for a particular chip set, you need to know what injectors were used to develop the maps for those chips.

As an example, one popular choice for 24# injectors in the past has been the Ford M9593-A302. Flow rates are similar (wihtin ~10%) but the difference in opening time (latency) is huge: 0.84 ms for the A302 compared to 1.25ms for the LU24A (at 55 psi and 12v, per Ford specs).

Either would be fine if the fuel maps were developed for that injector, but maps which were done for the A302 would be unsuitable for the LU24A and vice-versa.

ROG100

For what it is worth we stock the 19Lb & 24Lb injectors with the correct O rings. Remanufactured but like new. Sold hundreds of sets with only two injectors giving an issue. I wish I could buy them new locally but then the price would probably double. One European 928 owner has found some new ones in Germany.
Mine are the design II - "plug & play".
87 to 91 #19Lb/Hr - 14.5 Ohms 0280 150 556 FMS-M-9593-C302
85 to 86 #24Lb/Hr - 14.5 Ohms 0280 150 947 FMS-M-9593-A302

I have a lot more sets coming in and will offer a special of $310 per set of 8 for a couple of weeks until stock depletes.

76FJ55

The upper clip groove is not present on these. There should be a groove running all the way around about mid way between the o-ring and the notches in the sides.

PorKen

Latency, smatency (mostly).

All 928s with EFI are batch fired - two squirts per revolution - so it doesn't really matter when the injectors open. The length of time it takes to open the injectors (aka advance time) affects the total time the injector is open, but that base calculation can be adjusted either manually (S3) or automatically (S4).

Changing fuel injectors does not magically change the Volumetric Effiency of a engine. Unless you radically change the intake or replace the cams (exhaust to a lesser extent) the engine is going to breathe in pretty much the same as when it left the factory. People can spend years making new fuel maps. For their effort and expense, if they dared look, they will probably find that their super-awesome maps pretty much look like a bad copy of factory maps. (AMHIK. Not to mention, S4-up have an error prone MAF translation method that you can chase forever... )

Change gears, temperature, air pressure, etc. and the RPM to MAF relationships move around, up/down. Overall though, the factory maps match the VE of the engine they were made for. Weird!


Power gains come from more ignition advance when possible. Put simply, S300s chips take a holistic approach with new programming to maximize smoothness by reducing errors and continually adapting to conditions to maximize that advance at all pedal positions (not just WOT). (They are also manually adjustable, if needed.)


Factory MAF ideal (base fueling) map.

jcorenman

Ken, pretty picture but you are confusing additive and proportional effects-- slope and intercept, if you will. Injector latency is additive, while MAF aging and the LH adjustment/adaptation are proportional. With one data point-- the O2-sensor-- you can't solve for two variables.

Suppose, for example, that I took a fuel map that was optimized for the A302 injectors and instead used the LU24A's discussed above (after cutting slots, good catch). Driving down the highway the car would initially be very lean-- AFR 20:1 or so, until the LH made the appropriate adaptation based on the O2-sensor. It would wind up adding 25-30% more fuel to compensate for the longer opening-time-- it is a big effect with short pulse widths.

Now punch it. At WOT the O2-sensor is no longer active, but the adaptation continues to add 25-30% more fuel. The fuel pulse is much longer, but the opening-time didn't change, and the LH would be over-correcting. The result is that the mixture is going to be pig-rich, in the 9:1 range.

That's bad enough, but doing it the other way would be much worse: Tune for the LU24A and then run the A302. The mixture will be pig-rich while cruising until the LH adapts, and will then go dangerously lean at WOT (AFR in the 15-16 range).

Porsche dealt with that by sticking to one injector. When you tune a car, you choose injectors first then tune the fuel maps accordingly. Latency matters.

SMTCapeCod

We know Ken recommends cleaned/matched factory injectors for his chips.

Is the latency spec & resistance for the factory part available?
Flow rate was added earlier in the thread, 24.7 lbs / 3 bar (S3)...but wait was that supposed to be 247cc @ 3 Bar?

Also, I think John said one spray per revolution and Ken is saying two....I must've read something incorrectly..


This is pretty helpful:
http://www.polog40.co.uk/article_injector_table.php

jcorenman

Folks are talking about both S3 and S4's in this thread, so it gets confusing. For the S3, you are correct that Ken's chips are tuned for the stock S3 24# injectors, but with the regulator swapped for the higher S4 fuel-pressure. I don't have latency specs for those, Ken may. But whatever it is, it is correct for the stock maps as well as Ken's S3 chips.

S4's (and GT, GTS) use smaller 19# injectors which are used at the higher 3.8 bar (55 psi) pressure. Those are marginal especially for the GTS, but Porsche gains some headroom by pulsing them once per second engine revolution above 5100 RPM (IIRC). And they do run up to 100% duty cycle on some engines, at sea level in cooler temps-- but that is also tempered by the fact that the factory tune is pretty rich at the top end. Sharktuning for a more moderate 12:1 or 12.5:1 AFR provides some headroom, and after fiddling with timing yields a nice increase in power from the stock injectors.

Swapping to 24# injectors for an S4/GT/GTS provides more headroom and avoids the need for the every-second-revolution trick, injectors can be pulsed once per engine rev all the way up to max RPM. But this requires Sharktuning or chips that are tuned for those injectors.

The stock 19# injectors have a latency (opening-time) of 0.95 ms, the Ford M9593-A302 24# 4-hole injectors (that Roger posted about above) have a latency of 0.84 ms, the Ford M9593-BB302 30# that we have in our GT are 1.20 ms, etc. Different injectors of the same flow rating will vary quite a bit. Other than Ford Motorsports, spec's are hard to come by. And hard to test for, although we are working on that.

Injector flow ratings are generally spec'ed at 3 bar pressure, so the 19# stock S4 injectors actually flow 21.4 lb/hr at 3.8 bar, and the 24# injectors actually flow 27 lb/hr at 3.8 bar. Or thereabouts, actual flow rates can vary also between different injectors of the same flow rating.

Impedance for all of the 928 injectors needs to be 11-15 ohms, the so-called "high-impedance" injectors. Within that range I don't think it matters. The low-impedance type (2 to 3 ohms) won't work and will likely toast the LH.

I hope this helps.

SMTCapeCod

Very helpful to me, thank you. Learned something wrt the S4 double tap, and it helped untangle some of my thoughts on the thread to date- hopefully helpful to some future readers, too.

Potential datapoint here:
http://members.rennlist.org/jerdmann/ljetcomponents.htm

And another ques- if the injectors are close wouldn't post install recalibration of the MAF tamp down on the extent to which they would be running outside of bounds open/closed loop?

PorKen

As I said, mostly. Extreme examples are the reason why an adjustment pot* is included with S4.S300s chipsets to statically adjust the addition or subtraction required for different environments if necessary. The 'maps' require no modification.

'Tune' all you want. It's never going to be perfect with these computers. There are not enough inputs...no weather, no road speed. On top of that, stock MAF values are increasingly random at higher rpm. Fuel tables/maps are based on a coarse RPM to MAF value relationship. Change the relationship, run a different gear than what the maps were tuned with, the weather changes, or drive up a hill and you get problems with wot fueling.

S300s chips compensate for gearing, terrain, and coolant temp with new coding and custom mapping. They also smooth all inputs, including the wonky MAF, for more stable average fueling which allows for higher ignition advance = better response/more power. Things the stock chips, or tuning systems based on them, cannot do.


*This winter the coding plug will be programmatically removed in order to reuse its inputs, for a separate WOT adjustment, No-Lift-Shift, etc.

SMTCapeCod

This is tripping my OCD.....for the 24 lb high impedance injectors, factory rated flows are available on a few tables online. I spent a few seconds just searching for high impedance and 247 or 248...several leads but several do seem to be NLA.

Measured flow rates are available at Whunter and at least one other site...the variability is frustrating- 240-260 measured at 3bar for 24lb rated injectors. Gr. And then there is variability in the direction of spray on some.

More specs: http://www.justfuelinjectors.com/ser...flowchart/Page
Before flaming, the table is alphabetical, scroll down below accel.....

Hilton

I'm guessing by now you're aware that there are multiple credible sources of injector flow data, and some of them disagree?

jcorenman

And none of those tables include latency (opening time). Few manufacturers spec it, and it is not easy to measure. But the effect is large-- my examples above are both 24# injectors made by Bosch for Ford Motorsports, and they are a mile apart.

Flow rate is also a bit hard to measure: Gasoline varies in density, but I think most labs use various solvents for safety reasons. Flow rate specs within the same lab are probably reliable, between labs probably not.

I think part of the reason that the specs are so scarce is that car manufacturers don't worry too much about any of that stuff. They choose a suitable injector first, then tune the ECU's, then stick with that injector. And the aftermarket is mostly DIY or professional tuners, who do the same.

Kuba

Are we saying that two injectors of the same flow rate (24# @ 3bar) will flow different amounts of fuel at the same pressure depending on latency?

I will probably go with these (maybe): http://www.fiveomotorsport.com/blue-...011-0280150947