John Etnier

I got partway into the install and realized that (A) I didn't trust myself to safely disconnect the fuel lines and (B) it was foolish to go in there and not install an adjustable regulator at the same time.

I figure Paragon, unless someone suggests another source. Is it necessary as well to install a pressure gauge???

User 41221

Out of curiosity, did anyone check the height of the replacement injectors against the originals? That might make for mounting problems if there is much of a difference. Also, you don't have to take the fuel lines off, but its really easy to do. You shouldn't have any problems.

The folks that mentioned using soap... I don't like that idea, as soap can harden rubber o-rings. I think you are a LOT better off using ATF fluid, as its basically a detergent with additives for prolonging the life of rubber seals and o-rings. They are right about not "screweing the injectors in" tho, they should pop into place in the rail with slight pressure, and once you have all the injectors in the rail, then you align the injectors in the manifold holes and push down.

John, I am assuming the adj fpr is due to diffences in flow rate? I'm not sure you'll need it if I read the specs on those injectors, the stock fpr should be fine, but someone check me on that.

By the way, I just signed a lease on a corporate apartment in Dover NH (I'm up there monthly on business), so if you can wait until mid Dec, I'll be happy to run up and help you.

John Etnier

Thanks for the offer, Scott. At this point I have an appointment in place with my mechanics for a week from today: I would rather not cancel on them. They've done me a lot of favors this year.

I figured to pop in the AFR so as to increase flow a bit (airbox mod and aftermarket exhaust in place), but it is another $190.00. I may just do the injectors right now.

C5Driver951

Please check the length of the old injectors while you're at it measuring the distance between o-rings, and measure the diameter at the o-rings.

Thanks,
Joel

User 41221

John,

You may consider sending your old injectors out for cleaning (+1 for WitchHunter, they do great work) and have them on hand in case you aren't happy with your new injectors. I can have them swapped out in under 15 minutes, if you'd like to do back to back comparisons.

I've also heard (and this is second hand so don't attribute it to me or take it as gospel) that the four hole injectors are more prone to clogging than the pintel type injectors (which are more prone to sticking). Pick your poison, I guess... lol

Regards,

John Etnier

To sow further confusion in this thread, I have heard back from a 2nd vendor who mention a different injector: Bosch 0280155831. Here's the full quote from their emailNote that he's referencing the best match he has in stock. I plan to ask my vendor about this number, though.

User 41221

Just for reference, my newly serviced injectors were test flowed by WitchHunter at 3bar, and came in at 293/294cc/min. My car is running well and has very good power, but isn't showing any signs of running lean. Putting in an injector that flows at 324cc/min will give you 9% more fuel. I'd think that without a way to compensate for this (adding more air would be ideal), your car will be a bit sluggish with the newer injectors, regardless of "atomization".

Regards,

Jfrahm

Depends on the software. Naturally when you are in closed loop the ECU will dial out the extra fuel that slightly larger injectors would add, but if the software is decently written it will also correct the WOT maps (which are naturally open loop) to account for this variation.

Otherwise as your injectors get lazy or your fuel pressure regulator gets pooched you will start to skew really lean at WOT. Or for that matter if you have to switch to 10% ethanol gas seasonally. If you go from E0 to E10 fuel that'd be about the same effect as going from 300cc/min injectors to 285 cc/min in terms of energy delivered.

If the ECU is smart enough to compensate for variation in fuel quality or delivery pressure it'll handle a small change in injector size.

Also I do not think it's good to mount a fuel pressure gauge under the hood. Just another leak waiting to happen and you cannot read it when you are at full throttle under load anyway. If you are dyno tuning, use a proper handheld gauge.

When I have needed a fuel pressure readout I could see while driving I temporarily mounted a cheap mechanical oil pressure gauge by ziptying it to the cowl or wiper and adapted the line to the fuel rail.

-Joel.

KevinD

John - your last link to the new vendor (Fuelinjector.citymaker) had a chart on their site that listed the 968 as taking 0280-155-010 (not 0280-155-831 that he told you) and FuleinjectorRX lists this part as a 15.2ohm/ 296cc. That seems to be the closest match so far.

KevinD

OK, my bad - So the 0280-155-010 are the old style and the 0280-155-831 are the new 4 hole. But the 831s are "3 - 4mm taller". I have 4 on order and will let you know how much shimming they take to retain the original rail.

John Etnier

Man: this is getting frustrating. Where do you see the 155-010 listed and specified? The closest match I find to "FuleinjectorRX" is http://injectorrx.com, and I can't find listings of that sort there.

Meanwhile I've had to delay my Friday car work due to externalities.

User 41221

Joel,

Maybe you can answer this, as I'm not sure I have the answer. Doesn't the ECU in the 968 treat the fuel injector volume as a fixed unit and adjust voltages from there? In other words, it assumes at WOT it will see x amount of fuel based on the original spec of the OEM injectors? I thought that the DME doesn't have a way to measure fuel amount like it does air and approximates the a/f mix, and if it gets a discrepancy like more fuel than it was expecting to see, it throws a code. I haven't experienced that particular phenomenom on a 968, but I have played a little with the diagnostic code of the DME, so I am hoping someone here can confirm this.

I make no claims to be an authority on this, so if I am wrong, feel free to correct me.

Regards,

KevinD

John - yes the stats were on the link you gave http://injectorrx.com/boschtf.html
The injectors were listed in the catalog for Porsche on fuelinjector.citymaker
but when I called them (also known as MotorMan) they said they only had that 155 010 listed because they offer rebuilds for the cores, but they can't get new ones. He confirmed that the closest match in the 4 hole style was the 155 831.
http://www.fuelinjector.citymaker.co...INJECTORS.html

FRporscheman

Scott,
I thought the DME gets information on fuel mixture from the O2 sensor. I know it's technically not the same as metering the fuel input like a MAF meters air, but it's what they use.

User 41221

Yep, thats my understanding too. Its an approximation based on a translation of voltage (the richer the mix, the higher the voltage), rather than an actual measurement of the amount of fuel being injected into the cylinder. I'm not saying that the DME isn't capable of handling this, I am just trying to understand how it does so.

Regards,