1976 Porsche 912E fuel injectors with 1.8 Ljet injection? Options

[Geezer914]

Will 1976 Porsche 912E injectors work with 1.8 Ljet injection, on a type IV built to 2056 cu.in. with Raby RS heads and 9550 cam? I also have a 50mm VW Vanagon throttle body that I converted. I am thinking that the 912 engine being a 2.0L with Ljet injection it would add more fuel. Any opinions appreciated. (IMG:style_emoticons/default/confused24.gif)

[Krieger]

Those injectors should plug into that harness. You should put a wide band O2 sensor in the exhaust and air flow meter in the car for factual information. AEM makes one. Amazon is a good deal. You can turn up the fuel pressure a few PSI.

[ClayPerrine]

Already did that. Running in Betty's car for years. Works great!

[Dave_Darling]

Work? Sure it'll work. Will it be right? Maybe, maybe not. But you may be able to tweak the system until the mixture is good.

The 1.8 injectors may work as well. I recall Mueller running stock L-jet on a 2056cc and reporting that it worked fine as-is.

I'd still want to check the mixture with a wide-band O2 setup, though.

--DD

[Cap'n Krusty]

I don't like more than 2-3 extra pounds of fuel pressure. The spray pattern becomes less of a fog and more of a stream, killing the air-fuel mixture.

The Cap'n

[Valy]

The 912E injectors are the same as the 914 1.8 ones.

[Geezer914]

Size and fit, yes. But the part numbers are different. I am going to contact Standard Motor Products to see if they can give me any specs.

[Porschef]

I've got the same setup, using 912e injectors. They only flow slightly more than the 1.8s.

Very interested in your TB conversion, and if it will allow for a slightly leaner idle, the 9550 seems to be rich at idle, and I've got the bypass screw backed out all the way.

[JeffBowlsby]

This may help.

http://users.erols.com/srweiss/tableifc.htm

A given Bosch injector is often used on several different vehicles, same Bosch PN, different vehicle specific PNs, but its the same identical injector with the same performance specs, perhaps with different hose configurations is all.

The fuel needs of a specific vehicle are determined by the ECU, for that reason the same injector can be used on a 1.6L or a 2.0L engine all else being equal, because the pulse width is determined by the ECU. Knowing the injector specs allows crossover choices that may be identically compatible and are priced differently or are more available when a specific vehicle PN is hard to find.

I have posted a chart somewhere for substitute 914 injector PNs...

[Dave_Darling]

... the same injector can be used on a 1.6L or a 2.0L engine all else being equal, because the pulse width is determined by the ECU.

Yes, but.

A given size injector can only flow a maximum of so much fuel for a given fuel pressure. (And there are limits to the pressure; if it gets too low the fuel will dribble instead of spraying, and if it gets too high the pattern also suffers and the seals can leak.) So you can't have the injectors be too small.

You can't have them be too large, either. Metering of small amounts of fuel is difficult for large injectors, because the amount of time the injector would be open is too small. The ECU will only have a limited amount of resolution at those very short durations, and it will take a noticeable amount of time for the injector itself to open and close, and the variations in that will start to become noticeably large relative to the desired opening time.

That said, a given injector can support a variety of power levels or engine sizes.

Your point is valid in this context, but it is not a universal truth. (IMG:style_emoticons/default/smile.gif)

--DD

[Valy]

I've got the same setup, using 912e injectors. They only flow slightly more than the 1.8s.

Very interested in your TB conversion, and if it will allow for a slightly leaner idle, the 9550 seems to be rich at idle, and I've got the bypass screw backed out all the way.

They actually flow the same. Here is the original Bosch datasheet.
https://docs.google.com/file/d/0B7nmo8cXp08...sp=docslist_api

[ClayPerrine]

I've got the same setup, using 912e injectors. They only flow slightly more than the 1.8s.

Very interested in your TB conversion, and if it will allow for a slightly leaner idle, the 9550 seems to be rich at idle, and I've got the bypass screw backed out all the way.

They actually flow the same. Here is the original Bosch datasheet.
https://docs.google.com/file/d/0B7nmo8cXp08...sp=docslist_api

You are basing your data on the superseded part numbers. All auto manufacturers regularly supersede parts to decrease the number of items in their replacement parts inventory. The original 912E injector was a different part number from the 1.8L 914 injector. Because of the low volume of production on the 912E, the part number for the injectors was superseded by the 914 injector. It will work fine in most situations in the car.

If you look to the aftermarket suppliers, they used the original part numbers for their supply of parts. So the 912E injectors are a different number from the 914. And there are some small structural differences. The 914 injector has a "chimney cap" on the pintle. The 912E injector has a rounded end with no chimney cap.

The 912E injectors are the same part number as a Datsun/Nissan 280ZX injector. The 914 is not listed there. It has a different part number.


Don't believe me? Then get on any parts site and check. All of the aftermarket suppliers list different part numbers for the 912E injector vs the 914 1.8 injector.

[Valy]

I've got the same setup, using 912e injectors. They only flow slightly more than the 1.8s.

Very interested in your TB conversion, and if it will allow for a slightly leaner idle, the 9550 seems to be rich at idle, and I've got the bypass screw backed out all the way.

They actually flow the same. Here is the original Bosch datasheet.
https://docs.google.com/file/d/0B7nmo8cXp08...sp=docslist_api

You are basing your data on the superseded part numbers. All auto manufacturers regularly supersede parts to decrease the number of items in their replacement parts inventory. The original 912E injector was a different part number from the 1.8L 914 injector. Because of the low volume of production on the 912E, the part number for the injectors was superseded by the 914 injector. It will work fine in most situations in the car.

If you look to the aftermarket suppliers, they used the original part numbers for their supply of parts. So the 912E injectors are a different number from the 914. And there are some small structural differences. The 914 injector has a "chimney cap" on the pintle. The 912E injector has a rounded end with no chimney cap.

The 912E injectors are the same part number as a Datsun/Nissan 280ZX injector. The 914 is not listed there. It has a different part number.


Don't believe me? Then get on any parts site and check. All of the aftermarket suppliers list different part numbers for the 912E injector vs the 914 1.8 injector.

Did you actually read the data sheet? All the injectors are listed there, including the 912e and all 914 varianrs. The flow numbers for 912e and 914 1.8 are the same.

What substitution are you talking about. Those are the original part numbernumber.

[Valy]

One more thing: there is actually a difference between the 914 1.8 and the 912e injectors. The 914 1.8 had a 90 degree fuel line attached to them. It's in the datasheet as well.

[Geezer914]

Thanks for all the info. According to the Bosch chart, the 1.8 and the 912E injectors both flow the same volume at 18.1 lbs. per hour. The Standard Motor Products 912e injectors FJ707 appear to be aluminum or SS, while the 1.8 injectors are plastic.

Just received an email from Standard Motor Products, both injectors have the same flow rate. Just as suggested, adjust the AFR with a meter.