AMelbye

Hi,

My 1990 S2 has some very noisy injectors, and I'm trying to make up my mind regarding what to replace them with.

I've been searching a lot and found a few threads on the topic, but very few of them reach any sort of conclusion.

Here's what I've gathered so far:
The original part number is 0 280 150 811.
Specs:
Impedance: 2.4ohms
Spray pattern: A
Distance between O-rings: 60.5mm
Flow rate@300kPa(3bar): 208,2g/min or 297ml/min

this is according to a spec sheet that can be found on google by searching for "bosch injector data". Other places on the internet this part is quoted as a 25lb/hr injector. 208,2g/min is about 27.5lb/hr.

I've tried to get bosch tech support help me find a modern equivialent, and it seems that the misinformation goes all the way back to bosch. They first informed me that the injectors flow 25 lb/hr, then informed me that they flow 208,2g/min(=27.5lb/hr). There's obviously some mistake in their parts catalog. Bosch btw were very helpful. The guy I got in touch with really did his best!

I'll assume that the higher number is the correct one.

The point of installing more modern injectors:
modern injectors run quieter and produce a finer spray that gives better idle, lower emissions, lower fuel consumption and (some say) added power and improved throttle response.

Spray types:
A: this is the original spray pattern, single beam, very coarse atomization
B: I don't know TBH
C: modern equivialent of A. Single beam, four holes, fine atomization
E: dual beams, optimized for cars with 2 inlet valves (like a 16valve 944)

I'm not sure if I should go for C, which is closer to the original, or E, which is optimized for a 16 valve head. Here also comes the factor of spray angle. If it is too wide, it will hit the sides of the exhaust manifold, rather than being picked up by the air flow. I have no idea how wide I should go.

Impedance:
The S2 uses low impedance injectors. There's only one bosch injector with low impedance, similar flow rate and a modern spray pattern. The part number is: 0 280 150 969. I's a gen2 injector, having the same thick body as the original part, but a more modern spray pattern. The part was only used on the Brazilian version of the Opel/Vauxhall/GM Omega, the part is only available from Brazilian webshops. The prices are not horrifying, but more than I'm willing to pay for something I don't even know if will work.

If not using this part, the only other option is using high impedance injectors. There is a resistor pack that you may be able to remove. I've seen it suggested on the internet, but I have not been able to find any indication that anyone actually tried it.

IF high impedance injectors are an option, I've found what I believe is a good modern substitute: 0280155831 coming out of a modern 2.5L turbo Volvo engine. They're readily available and cheap.
Flow rate: 237,2g/min, which is about 14% higher (higher is safer than lower).
Spray pattern E (dual beam, is this a good idea?)
distance between O-rings: 60,3mm (60,5 on original part)

Then I have a bunch of data I don't know what to make of:
spray angle alfa-50: 20 degrees (not stated for original part)
spray angle alfa-80: not stated (21 degrees for original part)
axial deviation angle: 0 degrees (not stated for original part)
spray orientation angle 90 degrees (not stated for original part)
spray distribution area: 12-24 degrees >30% (8-30 >40% for original part)

spray distribution area seems to be the one that has the largest deviation. Is this good or bad?

Does anyone here know more about this than I do? I'd really appreciate some input.

My main questions are: is it safe to bypass the resistor pack and install high impedance injectors?
how will the engine management cope with the larger injectors?
Does anyone have experience with the different types of modern spray patterns (C vs E) in a 16 valve 944 or 32 valve 928?

V2Rocket

You are right that the S2 has very noisy injectors - partially because they are old design and partially because of the high pressure (3.5-3.8 bar)

Unless the noise is really bugging you or one is actually dead, there's no real point the swapping injectors...

But if you really want to, don't limit yourself to just OEM injectors - check with places like 5.0 motorsports, RC Engineering and other Injector specialty places, they have lots of new-style offerings in a variety of flow rates that will work well.

The 928 guys have high impedance systems but they have good luck with Ford injectors from the 1990s and 2000s.

Spray pattern...Believe the S/S2 use an old "single shot" pencil type squirt. Going to a more modern 4 or 6-hole "spray" injector will help, the split-shot like you mention for the multiple valves isn't really very useful, but the finer spray from a multi-hole disc-type injector is good.

AMelbye

I think my injectors do work ok. My idle is anything between rough and horrible, but I have no reason to believe it's caused by the injectors. More likely something else.

However, the noise bothers me, and I'd really like to swap them out if even just to make absolutely sure that the noise is coming from the injectors. (I believe it is, but I won't know 100% before I have replaced them. I'd hate to ignore the ticking only to have a ruined block due to a valve seat falling into the cylinder. Worst case scenario )

Swapping in a new set of stock injectors make little sense if I can get better performance for cheaper using a more modern part, so I started looking at options.

As for the split shot not being useful: do you mean it'll have no benefit over a standard (modern, type C) conical spray, or that it will perform worse?

V2Rocket

No benefit.
944s don't drop valve seats.
If it's a LOUD but regular/consistent ticking it's the injectors...Do you have the foam/plastic fuel rail cover fitted? It helps to knock down some of the noise.

AMelbye

944s don't drop valve seats ever? I've heard that they can disintegrate and parts of them may fall into the cylinder causing very expensive damage. Not so on a 944? That's good news

I've emailed 5.0 motorsports and RC Engineering, and hopefully one of them will turn up with a solution.

The ticking is loud and quite consistent except it gets even louder when the engine gets warm. I have the fuel rail cover on and I've checked that the rubber is still in there. The rubber is not in perfect condition, but I believe it's still about 90% effective compared to new.

V2Rocket

In the 12 years I've been involved with 944s the only valve seat I've ever heard of that dropped was an aftermarket one that someone installed on their SOHC head to fit larger valves.

The original ones are in there good...

AMelbye

I'm aware that some valve seats and valves have been replaced on mine a few years ago, but I'll cross that off the list. Thanks

RC injection got back to me. They have a suitable replacement, however their parts are all one-hole, so I'm guessing they're the same type as the original design. Kinda pointless unless I've missed something?

5.0 motorsport got back to me too, suggesting a 3 hole Lucas injector.

I guess the Lucas injector would be an improvement over the gen1 bosch, but compared to a gen3 bosch? I think not, based on this video:
.

So the question left is: is it safe to disable the resistor pack on a 944 S2 to run high impedance injectors? Has anyone done this?

Gen3 bosch injectors are cheap and easily available, but high impedance only. It would be great if I was able to use them.

V2Rocket

high impedance would reduce the current flowing through/out of your DME - should only be safer, really.
there isn't any resistor pack that i am aware of.

AMelbye

I read in a forum thread somewhere that the 89-90 S2 has a resistor pack, but I haven't checked if mine does.

According to what I read, the 89-90 has a resistor pack, and the '91 does not. Perhaps the S2 was originally designed for a high impedance injector, but for some reason (supply problems?) they decided against it at a later stage, and didn't put them in until '91.

If so, it is likely that the injectors are running in saturated mode, even though they are low impedance. The only way to know for sure is by checking with an oscilloscope. If they are running saturated mode, removing the resistors and swapping in high impedance injectors should work fine.

If the injectors are running in peak and hold mode, it'd say it's safer/better to stay with low impedance injectors, even if there is a resistor pack present.

I won't be able to check this for a couple weeks, but I will find out and report back. Or perhaps someone will stop by and provide the answers by then

V2Rocket

unplug an injector and put an ohmmeter or DMM across the pins, that will tell you if high or low impedance where it matters..

AMelbye

This will tell the impedance of the injector, but it will not tell if the injectors are driven by a peak-and-hold signal(high voltage to open valve quickly, low voltage to keep it open) , or "saturated mode" (same voltage for the whole duration of the pulse).

High impedance injectors are designed for saturated mode, and may not behave as expected if run with a peak-and-hold signal.

V2Rocket

All low impedance injectors are peak and hold. All high impedance are saturated types, it's a characteristic of the solenoid coils.

manu4jc

What dictates the use of high or low impedance? The DME? The Harness? Both? Niether?
The reason I ask I have a situation where I have a 91 S2 engine and harness and a 90 S2 DME and injectors... wanting to see if it is a problematic combination or not.

V2Rocket

the DME, much lower current required for high impedance (less current less heat)...there was some kind of resistance change in the 91s but I don't recall the specifics...I believe there was a resistor pack added though?