Injectors for 850 T5- fat ones or thin ones?

[chumpden]

There are two different injectors listed for my 1997 T5 (B5234T engine), fat EV1 type 0280150785, and thin EV6 type 0280155759. According to some suppliers, icluding Bosch and Rockauto, the thin ones are for cars with fuel return sytem, and the fat ones for cars without. My car has a fuel return pipe, but is fitted with the fat injectors. I would be happy to conclude that the injectors have been replaced incorrectly, and get a set of the thin ones were it not for for the fact that many suppliers contradict the above advice and specify the fat ones for fuel return sytem cars. I haven't been able to get a definitve answer as to which is correct, and why there is a difference. Can anyone help?

[misha]

Both have fuel return systems...the difference is that M4.3 have it on fuel rail and M4.4 have it at right hand rear wheel(fuel filter area).
M4.3 have FPR on fuel rail and M4.4 have fuel pressure DAMPER there...while fpr is in fuel filter area in the back of the car.

[chumpden]

Thanks misha. Useful information. Do the two injector types correspond to the two respective injection systems, or is that too simple?

[misha]

They are identified by their colour.The colour says what flow rate they have,besides Bosch part number.
I don't have a turbo,but as far as i know... M4.3 & M4.4 turbo car's injectors are interchangeable.

Parts stores are not quiet correct about info they provide,sometimes pretty confusing...BUT part numbers are like the fingerprints.
That said....if you don't know what you need they are usually confusing.

[chumpden]

Both are orange and have the same flow rate, but slightly different impedances. I think they might be interchangeable, but I am not sure. The fat ones that are fitted are working, so perhaps I should stick with them. The thin ones are more readily available it seems, and are more modern, so it would be a good idea to use them if they are compatible.
Thanks again for your advice.

[WhatAmIDoing]

If it ain't broke, don't fix it.

[erikv11]

Fat ones!

Bosch 0280150785 are oranges, 315 cc/min.
Bosch 0280155759 are reds, 315 cc/min.

Your 97 turbo is a 2.3 HPT and shipped from the factory with EV1 type 0280150785, which are orange. That's why they are in there.

The EV6 type 0280155759 may appear orange in some photos, but they are red. They started shipping in 97 (US market) with the 2.5 LPT engine.

Perhaps you could put reds in an 850 HPT but in all these years I don't think I've ever heard of anyone doing that particular swap. Although their flow rate is the same, the other relevant variable for the ECM to get a proper AFR is the injector dead time. Since dead time is a function of voltage, it may differ slightly between reds and oranges for that or reason or just by design. The tune is expecting oranges, give it oranges ...

Reasons I have seen to switch injectors are for servicing (send for sonic cleaning, replace a bad one, etc), or to use a different tune that calls for a different flow rate. Fuel system type is irrelevant.

[chumpden]

Many thanks for your replies. Whilst it ain't exactly broke, I didn't know if it was optimum, and I do need at least to replace the seals because there is a petrol smell in the cabin. If they are the original injectors, they have probably been undisturbed for 20 years and 170000 miles. Thanks, erikv11 for that authoritative explanation. I am a bit colour blind. It looks like Rockauto, Bosch and others need to update their information bacause they list the thin red ones for 2.3T engines. I'm glad I asked the experts.

[hausmeister]

If you have to remove them anyways think about getting them serviced or replace with serviced injectors. The originals in my car were not very good it seems, I replaced them with serviced injectors, the engine even sounded very different after that.

[chumpden]

Yes. good idea. I have ordered some new ones, and I'll get the old ones serviced for spares or for someone else to use.