dk17340

Will 1991 944s2 fuel injectors work in an 87 944s?

ramius665

Yes. The S2 injectors are slightly more powerful so you may run a bit more rich.

924srr27l

Are you thinking of changing your injectors for S2 versions will make your car faster or ?


Only they may be larger (Bigger amount of fuel flow per second) but unless you change your settings / ECU it may not run well at all and would not make the car faster anyway ? the S2 has 500cc bigger capacity and hence needs more fuel the 2.5 S.

Jfrahm

IMO you are better off sourcing appropriate EV6 injectors. They are quieter, which makes it easier to hear other engine noises. They may also have better cold and low RPM atomization, probably not measurable. But if you are going to the trouble of changing injectors you might as well get a more modern, improved design. You could probably go 5% bigger and that'd compensate for the E10 gas we have now, although this correction should already be within the stock maps.

odonnell

You can use this page to figure out the injector specs based on the part numbers:

http://www.polog40.co.uk/article_injector_table.php

It looks like the S2 injectors, which are 0280155003 according to another thread on here, are 277 cc/min (26.4 lb/hr, which you can to convert on this page) and are 15.4 ohm impedance.

The 944S injectors, which are 0280150811 (looking at 'Product Code' on this page), are the same flow rate but have a lower impedence (2.4 ohms).

So you can install them but you aren't guaranteed to have the same end-of-the-day pulse width (how long the injectors stay open for, per pulse). Whatever you do, don't install 944S injectors in an S2. The lower impedance allows a high current through the drivers, which they may not be designed to take.

Stoich AFR for pure gasoline is 14.7, stoich for E10 is ~14.1, which you're right, is ~5% different (4.08%). Therefore OP could get some 0280156061 injectors which are 289 cc/min (4.33% more flow, at 12 ohm impedence), they should fit just like old ones and will plug right in to the stock harness. It looks like 0280157008 and 0280159709 may also be equivalent.

http://www.ebay.com/sch/i.html?_from...56061&_sacat=0

ramius665

Michael, both the S and S2 have an in-line resistor pack for the injectors as part of the Jetronic fuel system.

odonnell

Ah ok, never mind my blurb about impedence then. Thanks Aaron!

added to my post, there are some injectors out there that the OP could have a go at.

Jfrahm

Whatever you do, make sure you use injector clips or some other robust means of securing the injector to the rail. There have been car fires as a result of unclipped injectors popping out of the rail and gas spraying everywhere. In one case a clip was put on but it was inverted and not gripping the injector.
If you need clips the BMW equivalent is cheap and easy to get.

Dimi 944

That is valid only for '89-'90 S2.
'91 S2 models do not have the resistor pack and use different injectors.

dk17340

Thanks for the input. I was asking because I was looking for a replacement set of injectors. I wanted to get the knowledge from the group, before I procured the wrong set of injectors. Thanks again.

Dougs951S

Isn't this failing to take into account the fact that the different impedance will effect the dead time of the injector and therefore the actual amount of fuel injected, IE going from a 15.2 ohm injector with X flow rate to a 12 ohm injector with X+5% flow rate will not necessarily result in 5% more actual fuel delivery?

Edit: NVM I can't read obviously as you already mentioned that...

924srr27l

I'd just get your original Injectors Ultrasonically cleaned and tested for spray pattern and flow etc...

Otherwise changing them may cause some adverse effects.

I was thinking of different Injectors on my 2.7 Motor, and a company here in the Uk tried some other make but they could not get them to work properly (from idle and all the way up the Rpm range), so I decided not to dabble.

Then my engine man said the stock Bosch ones are fine, unless you've a turbo motor and your seriously upgrading and increasing the boost etc..

R

odonnell

The stock S injectors look pretty small to me at 277 cc/min actually...

http://www.witchhunter.com/injectorcalc1.php

Assuming a 0.50 BSFC (it's NA) and a maximum allowable duty cycle of 85% (which is standard for sizing injectors), you're pretty much maxing them out at 180 bhp.

It's interesting that Porsche decided to use the same flow injectors for the S2. At 205 hp, they would have to be run at an 88% max duty cycle...even assuming a 0.45 BSFC which is very very good for an NA motor. So I'd say anyone modifying a 16v 944 to where it will make +10hp past stock, should be interest in upsizing the injectors. I'm very happy with the 0280150431 injectors in my 8v, they're ~30.1# at 2.5 bar fuel pressure and there are no resolution problems at idle, and peak power they're only having to do ~70% duty cycle. Makes tuning easier when that's out of the way.

Arominus

Your kind of right, IIRC the 91 S2's went to a different resistance injector, along with some other wiring changes that carried into the 968. We had to deal with the ac wiring because it changed in 91, so when the 93 968 motor was swapped the 89's wiring was no longer right and the a/c wouldn't activate. We had to rewire a few things at the DME to get it working.

Humboldtgrin

Op if you subscribe to rennlist I'll send you my 87 944S injectors from my parts car free of charge. The downside, I've never seen the car run...