Why EFI?, maybe excellence was expected and they came as close as they could.. Options

[Gunn1]

Did Porsche eff up?

No they didn't eff up, they did the best they could with the new technology they had. It seems as though the technology was purchased by the folks at Bosch from the aviation component of Bendix. That said most Injection systems were originally good at idle and full open throttle, so primarily racing applications. So in there infancy not well suited for automobile applications.

Been reading on different types of fuel delivery systems and their pro and cons.


There are very few con's to todays EFI systems, there were however performance and reliability issues with the original designs. Even today Claims of increased HP, Fuel economy, drivability, reliability and so on....some still dispute
how much these differences really mean. It appears the main thing EFI does extremely well over Carbs is in the pollution factor, or in this case the ability to pollute less. Carbs are a some what open system allowing hydro carbons to escape/vent in to our atmosphere even when the engine is at rest, where as the EFI is essentially a closed system releasing no vapors or gases unless the engine is running and those gases are then coming out of the tailpipe from the exhaust cycle.

Many of the Guru's (about 5 to 1) prefer carburation.

The above Statement isn't correct, although what confuses this OP is the sheer amount of photographic evidence on this site and others including evilbay and CL showing most engine compartments with Carbs installed. Many here have spent thousands on their cars, and what do you see when the lid is lifted? a Carburated engine..... So while my intentions will be keeping my cars in their stock or near stock form, with EFI, I cannot understand why so many Carburated cars. (Because its easy isn't an answer, because its simple isn't an answer and because its cheap isn't an answer)

With this being the case, Did Porsche mess up when they went the EFI route with the 914?


I do not believe they messed up, I believe they did the best they could with the available technology they had. Granted they did sort of use the end user as of a kind of a guinea pig/test bed, but what manufacturer doesn't in some way.

WHY DID THEY DO IT?????


I think that just as much as seeing the Ljet and Djet as a performance and platform to develop future EFI systems off of, Porsche and others also incorporated EFI into there products to show they were progressive company's in design and practicality.
EFI, Unibody, Targa, Mid engine, four wheel disc, and many more attributes can be cited as Porsches View into the future.

I would like to keep my car stock with the factory EFI, but increasingly getting more difficult to do with so little information backing it up.


Above statement is also incorrect. In my case I think I am fortunate because I believe I have most the parts needed to reinstall the factory EFI's on all three of my cars. There is a plethora of info on both sides, but for now.... just for originalities sake, EFI will be the way I go.

To those that added constructive comments and or facts to this thread... it is much appreciated...to those that took this thread as some sort of attack on their beliefs, or way to "clutter" the site, I can appreciate how you feel, but I just see those arguments as shutting down the free flow of ideas and the give and take of facts that get each of us to arrive at our own understanding of the information.

[Darren C]

Hold on guy’s, I know the OP has got everyone hot under the collar….

Brant. I never said 14.7:1 is ideal specifically for a 914. It’s the best ratio for max power from burning gas. I agree totally with you, our cars run much richer.

Conedodger. I agree entirely with you, like I said in my earlier post the best comparison test would be an other UK members FI car on the same Dyno. The lower data in the graph show barometric pressure, relative humidity and temperature at the time of the testing if you want to get real picky with comparisons.

DBCooper, check the lower scale on the graph, its RPM, so you see the full AFR & HP across all throttle settings. Each of these dyno runs took 20 minutes over the full rev range against the force of the rollers, the Dyno’s computer takes the data and produces the graph. The rollers offer a resistance to the car so that you get a true representation of driving underload through the whole rev range. It's the only sure fire way to get meaningful data and a feel for driveability while plugged into the machine.

I’m not agreeing or disagreeing with the OP, just posting some data so that everyone can make up their own minds. Jeez even with hard data you guy’s still want to pick a fight as you only see what you wanna see.

Stugray, I agree with you, that’s why I said we need to compare eggs with eggs and welcomed an FI data post by someone else. Although I do disagree with you when you say its not as useful as the first 4 pages :-)
So as a fair comparison with all I can offer, lets look back at Jeffs equally informative graph of factory specs. His graph has Torque v Horsepower for the FI 914.
As I indicated earlier I have around 50 various data graphs from the 4 hours on the Dyno. Here’s the equivalent graph to Jeffs, showing HP & Torque but on a carb 914 through 3 jet sizes.

For info The dyno is at sea level in Portsmouth UK, the car is timed at 27 BTDC as per standard with stock cam, NO modifications other than just bolting on carbs.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i265.photobucket.com-18255-1465851457.1.jpg)

Hopefully this’ll be a starting valued comparison for you Stu. Jeff or someone more computer literate than me can maybe post the two graphs side by side (Jeffs and the one above)

Gereed, Thanks for your post, I agree, the only way to truly optimise AFR is to go FI. You can pull the lean/rich issue slightly changing air correctors, but imagine the AFR graph line is a see-saw (pivoting in the middle, say around the 3500rpm point in the lower scale) if in your case your running too rich at part load changing to a smaller air corrector will tip the graph up a little at low revs but down at high revs. The pay off in trying to fix your issue with air correctors alone will be richer running at higher revs. This is where a lot of messing about and testing on the Dyno is needed, but as we all agree, FI makes this easier to control. Carbs are great but crude in this respect. However carbs can be fiddled with by any home mechanic, not many have the tools or knowledge to re-map FI. It’s horses for courses. As Brant says by changing more than the air correctors you could eventually get close to a perfect set up, but it will always run richer than an FI equivalent.

Sir Andy,
My car is a US California car, so its stock wasn’t 100HP. US spec GA 2.0 engine: 91 HP @ 4900 rpm is the figure measured by the U.S. standard SAE
In Europe the HP figure is measured by DIN which is 95 HP @ 4900 rpm for a U.S. spec GA 2.0 engine.
As I’m in Europe our Dyno measures HP in DIN, so I haven’t lost any HP at all, but thanks for asking!

So tin hat back on, I try and be helpful, offer facts not opinions, have no bias to FI or Carb and the guns point my way yet again?

[SirAndy]

My car is a US California car, so its stock wasn’t 100HP. US spec GA 2.0 engine: 91 HP @ 4900 rpm is the figure measured by the U.S. standard SAE
In Europe the HP figure is measured by DIN which is 95 HP @ 4900 rpm for a U.S. spec GA 2.0 engine.
As I’m in Europe our Dyno measures HP in DIN, so I haven’t lost any HP at all, but thanks for asking!

Since you're in Europe, thanks for leaving out the (somewhat important) detail that your car has a US spec engine ...
(IMG:style_emoticons/default/rolleyes.gif)

PS: Do you still have the CA smog equipment installed? Are you using the stock exhaust and stock heat exchangers?
Because if not, the 95HP @ 4900rpm is not a correct baseline to measure against. To quote your own words "eggs with eggs".

[Darren C]

My car is a US California car, so its stock wasn’t 100HP. US spec GA 2.0 engine: 91 HP @ 4900 rpm is the figure measured by the U.S. standard SAE
In Europe the HP figure is measured by DIN which is 95 HP @ 4900 rpm for a U.S. spec GA 2.0 engine.
As I’m in Europe our Dyno measures HP in DIN, so I haven’t lost any HP at all, but thanks for asking!

Since you're in Europe, thanks for leaving out the (somewhat important) detail that your car has a US spec engine ...
(IMG:style_emoticons/default/rolleyes.gif)

PS: Do you still have the CA smog equipment installed? Are you using the stock exhaust and stock heat exchangers?
Because if not, the 95HP @ 4900rpm is not a correct baseline to measure against. To quote your own words "eggs with eggs".

Sir Andy,
I'm not looking for a fight here.
As I said earlier my car is stock apart from the carbs, including stock exhaust and heat exchangers. The smog equipment came off the car as part of the FI removal.
That's all.
As for neglecting to to say it is a US spec car, it was you who assumed it was european, then chastise me?
My build thread and introductions on this forum show quite clearly it's a US car, photos of it in Desert Hot Springs CA and its importation to UK are well documented and it's listed on the register on here.
Why do I have to keep on making justification for every post I make on this forum?
It just creates fear to post by those who are less thick skinned than me.
Somd914, I agree with you, that would be the best comparison ever.
My reason for posting in this thread was to try and add some fact on why emissions drove the carb to FI move in our 914 and to in some way satisfy the OP without all the tit for tat that ensued over the first 4 pages.
Like anyone breaking up a fight, seems both sides have turned on me now and any good intent and good information is lost in the fractious. Hey ho.