Ok to Install 1.7 Injectors on a 2.0?

[73ess]

Is it possible to install 1.7 injectors on '73 2.0 engine without problems? What exactly is the difference between the 1.7 and 2.0 injectors?

Thanks,
Steve

[djpateman]

flow rate is different, so it will always run lean, and may burn the engine. Not a good idea.

[73ess]

Can you compensate by adjusting CO mix at the ECU? Other components that one could adjust to compensate?

[bowlsby]

Thats just an idle adjust screw, it has no effct off-idle.

[Bleyseng]

No, not enough flow even with all kinds of monkeying with a MPS.

Been there done that!

[larrym]

it will run very lean & HOT & the preignition will kill your pistons

I tried it years ago when I was poor & stupid

[galto]

D-Jet or L-Jet?

I don't think it's a good idea on the D-Jet because I think the D-Jet uses the inducance in the injectors as part of it's firing seqence.
And I just don't think it's a good idea.

[73ess]

Hmm...my mechanic (a very reputable Porsche shop) says it's not a big deal at all. The difference is minimal. Hmmm...

[djpateman]

Originally posted by 73ess
Hmm...my mechanic (a very reputable Porsche shop) says it's not a big deal at all. The difference is minimal. Hmmm...

If you believe that, I can sell you some engines fresh from New Orleans.

[Bleyseng]

as I said, I have tried it and couldn't get enough flow at Wide Open Throttle, not even close! So if Porsche couldn't do it 35 yrs ago when they built the 2.0L in 73 why do you think that it would work now???

2.0L flow way more air with those big ports and big valves so they require way more fuel!

[73ess]

Just how much is the difference in flow rate. As my boss would say, "Where's the data to support the claim?". ;^)

[Bleyseng]

I don't recall the specs off hand but DD must know!

[Dave at Pelican Parts]

Nope, sorry. DD does not know.

However--I do know that it has been tried a number of times over the years, and as far as I know nobody has gotten it to work correctly. I'm thinking the limitation is elsewhere in the system, though, because I recall the injectors themselves have way more than enough flow rate than they need... But at that point, you don't exactly have D-jet anymore.

--DD

[djpateman]

It does not have to be off by much to screw up the air/fuel ratio. Because it flows less, the mixture is lean. Lean mixtures burn hotter and will crack your heads.

The factory could have kept the same injectors and changed the ECU, but elected to keep the same ECU (in 1973) and changed the injectors. This is what highly paid engineers decided to do after much testing, and I am not about to suggest they didn't know what they were doing.

From Brad Anders site:

Flow rate data (courtesy of Roland Kunz):

Yellow (1.7L) - 265 cc/min @ 2.0 Bar, 3V, 0.15 mm ± 0.05 mm lift
Green (2.0L) - 380 cc/min @ 2.0 Bar, 3V, 0.15 mm ± 0.05 mm lift

That is a 43% flow rate increase.

[pbanders]

Don't do it. The 2.0 injectors are electrically identical to the 1.7 injectors, the only difference is the flow rate. To use 1.7 injectors in a 2.0 motor, you'd need to adjust the MPS to increase the duty cycle of the injectors, across all operating conditions. Getting this "right" has proven to be difficult or impossible for those who have tried before. This may be due to limitations in the drive circuit in the ECU at supporting the higher duty cycle. See my site for additional information.

[bowlsby]

Brad, the early injectors are NLA at the moment, but the later injectors are available. The part numbers are almost identical, ending in 031 and 031A.

Curious to know if you or anyone else has any documented information about the differences between the early (73-74) and late (75-76) 2.0L injectors?

Are the flow rates the same? Are the two part numbers functionally interchangable for all 914 2.0L engines?

Could it be that the respective ECUs or other FI system parts are different enough so that Bosch would have required different injectors or was the updated part just a minor upgrade like for a different/better pintle design or something?

[Dave at Pelican Parts]

Originally posted by pbanders
This may be due to limitations in the drive circuit in the ECU at supporting the higher duty cycle. ...

That was what I was alluding to in my "elsewhere in the system" comment...

Originally posted by bowlsby
Curious to know if you or anyone else has any documented information about the differences between the early (73-74) and late (75-76) 2.0L injectors?

I checked the impedance between two sets I had (8 early injectors, 4 late ones), and the difference was in the noise. When I sent them out for cleaning and flow-rate checking, they appeared to have the same range of flow rates at the beginning, and were definitely the same when they came back.

--DD

[pbanders]

It could be that there was a change made in the later injectors that was related to reliability (e.g. an improved part), and that they are electrically and functionally the same. Regardless, if given the choice between using 1.7 or late 2.0 injectors on a 2.0 displacement engine, I'd use the late 2.0 injectors.

[73ess]

Well, I'm gonna trust you guys over my mechanic. Anyone got a decent pair of 2.0 injectors for sale?

[Jared at Pelican Parts]

I have tried it in an attempt to save money in the past. It does not work. You cant play around with the MPS and the FPR all you want, it still runs lean.