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

[Jake Raby]

Hell, I still have some cars with points, and condenser too... But I favor a mechanical diesel that only has one wire in the engine bay, and that kills the fuel control to shut it down.

[MarkV]

...so given that why would you put carbs on a stock configured engine?

1. Reliability- Damn I was always fooling with the Dells

2. Simplicity- Yep, simply refused to start in the cold

3. The ability to use a non Bosch distributor- why?

4. The look- well maybe

5. The sound- yes, that loud sucking sound so I couldn't hear the passenger talk....

1. I never mess with my Dells....I rebuilt them and jetted them when I got the car.... easy to work on.

2. I don't live in the cold. As cold as it gets here it still always starts.

3. Every Bosch distributor I have owned had a dwell & timing that bounced... they can't be dialed in without a distributor machine. The cap is too small and the electrodes are too close together. The Mallory is totally adjustable by the user....multiple advance curves and springs.

4. Maybe?

5. I like the sound. If I want to talk I drive my daily driver.

I have the injection in a plastic box in my garage I just choose to run the Dells.

[Mike Bellis]

I did not read through all 9 pages...

EFI/FI was developed for fuel economy not maximum performance. The early 70's saw the oil embargo and every manufacturer was trying to make a smaller more efficient vehicle. Emission standards were also getting tougher to meet.

Technology has vastly improved since then. EFI is far more efficient than carbs. Even for max HP. Any rpm or load can be programmed in a modern aftermarket system. Porsche still does not tune for maximum HP, rather it's a balance of performance and driveability. They are leaving HP on the table because no one wants to drive a drag boat on the road; all on or all off.

Did they screw up? No. They integrated the newest technology of the 70's in search fo a balance.

[Darren C]

Jd74914, Thanks for taking time out to overlay both graphs. Great work!

As you say, and I and others have said the only real comparison is to have two cars run the same dyno.

Once you start to manipulate/compute two separate sets of data from 2 separate dyno machines to “average” them you get an average but not accurate result. I’m going to try and convince a fellow UK D-jet car to run the same dyno as mine to get a better idea -still expecting someone to say afterwards; hey it was sunny one day and raining on the other ;-)

Your overlay graph is interesting as the tail off at high rev range may mean I need to look again at my Air Correctors, or it may mean that the two separate machines had slightly differing calibration on their ability to measure RPM? That’s an interesting thought as it would pull my early gain in torque in line with the D-jet, and push my late drop off in torque back to match the D-jet.
It’s all probably old news to the anonymous guru's, but I haven’t been able to find good graph data comparing a stock D-jet and a stock engine just running carbs with no other modification or parts changed; only strong historical opinions of the results in a “because I say so” format. Or data on hot cam modified engines where it is hard to make comparisons.

What has been shown in this thread from the data is that at the HP and torque on two standard engines, one with carbs one with D-jet are pretty much the same. So it follows that the drive would be a similar experience.
Now I’d love to see the AFR (Air fuel ratio) trace for the D-jet for a similar comparison to my first graph so that we have the data for emissions, and can see the fuel economy differences in cold hard facts. We all know the Carbs will be running richer with less mpg and higher emissions but the data will make an interesting read and would be more useful than a “because I said so or he said so” response. OP, we know the factory changed to FI based upon emissions, let's wait to see the AFR data from the D-jet to compare the two otherwise stock engines, and it'll hopefully show why they didn't eff up.

Jake, love your reply! I have cars with Magneto ignitions and Autovac fuel supply!

[Gunn1]

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

Now that's some of the dumbest bullshit I've seen in a while, and then, just when you think that one could never be topped it (good God!) just keeps on coming:

If indeed a 914 is NARP I guess it could be said Porsche didn't eff up?

Are you drinking again?

Nothing to do with drinking, I just have an aversion to loudly expressed ignorance and to trolls. So you said five of every six gurus preferred carbs to fuel injection and were asked several times who those "gurus" were. Gurus, right? No answer yet, so who exactly are they?

Oh DB,

I believe thou is the ignoramiss within this thread.

Has thou not seen and read all thee those Guru's have said?

Obvious is the troll, it is not I, for I have resigned myself to EFI.

So DB open thy mind, thy heart, thy soul, let all the data sink in, then thou will know.

Whether it be EFI or Carburation in your ride, it is ultimately up to thy owner to decide.

So rather than holding on to anger and such, let it go before thou appears to protest to much...... (IMG:style_emoticons/default/piratenanner.gif)

[Darren C]

Jeez, did you stay up all night to write that poem? It's 9:43am here in UK, so I'm up and about. What time is it in Minnesota?
Me thinks the tit for tat may be consuming you.

[Gunn1]

Jeez, did you stay up all night to write that poem? It's 9:43am here in UK, so I'm up and about. What time is it in Minnesota?
Me thinks the tit for tat may be consuming you.

No ....working on a emergency water main break overnight in Bloomington, Mn.

Looking forward to fixing this, then working a full 12 hour day shift afterwards.

As far as tit for tat ........I'm good!

[stugray]

I would like to see two exactly stock engines on the dyno EXCEPT:

ONE engine has a mild carb cam, dual webers, and tangerine racing's street exhaust.

I am guessing an easy 15-20 hp over same engine with stock EFI.

And there is another reason to have carbs on an otherwise "stock" motor: Vintage racing.
I would have a megasquirt instead of carbs if the rules allowed it.

[Mueller]

...so given that why would you put carbs on a stock configured engine?

1. Reliability
I can agree with this somewhat, of course if starting off with old worn out carbs this might not be true

2. Simplicity
I can agree with this somewhat, of course if starting off with old worn out carbs this might not be true

3. The ability to use a non Bosch distributor
I've run a Mallory Unilite distributor with D-Jet , I just added electronic triggering inside for the injectors, cost less than $10

4. The look
Yep, they can look good on a flat motor

5. The sound
Yep

I never had a 914 with carbs (except for the /6 I had for a few weeks) I've tempted to buy carbs for the current car but will probably stick with the LJet since I don't want to dump too much money into it.

[sb914]

(IMG:style_emoticons/default/dead horse.gif) (IMG:style_emoticons/default/dead horse.gif) (IMG:style_emoticons/default/dead horse.gif)

[Bleyseng]

I would like to see two exactly stock engines on the dyno EXCEPT:

ONE engine has a mild carb cam, dual webers, and tangerine racing's street exhaust.

I am guessing an easy 15-20 hp over same engine with stock EFI.

And there is another reason to have carbs on an otherwise "stock" motor: Vintage racing.
I would have a megasquirt instead of carbs if the rules allowed it.

I still have to dyno my 2056 with a Raby cam and Djet as it should be in the 115-120 hp range. 25mpg and tons of torque....so who needs carbs as it looks totally stock.

[DBCooper]

As far as tit for tat ........I'm good!

No, no “tit for tat”, just a simple request for substance that you've repeatedly ignored. You said “Many of the Guru's (about 5 to 1) prefer carburation.“ Now that’s a surprising fact that you then used to infer that Porsche “effed up” by putting fuel injection on their engines, questioning the competence of Porsche engineers. Those are statements you made, so I’m just curious to know where you get this information, who you consider a “guru,” and why you think they’re better than the Porsche engineers. Simple enough. You’ve been asked several times who these “gurus” are and you have time to rhyme, so what’s the problem?

By the way this isn’t a new question, google “carbs vs. fuel injection dyno comparison” or anything similar and find lots of empirical comparisons complete with charts and graphs. Generally carbs can equal fuel injection at wide-open throttle, so a draw there, but fuel injection is more efficient and performs better at all RPM points below wide-open. Meaning the Porsche (and every other car manufacturer's) engineers were right, no surprise. As to the “look” and the sounds of carbs, those are purely subjective so really silly to argue about.

[914_teener]

I would like to see two exactly stock engines on the dyno EXCEPT:

ONE engine has a mild carb cam, dual webers, and tangerine racing's street exhaust.

I am guessing an easy 15-20 hp over same engine with stock EFI.

And there is another reason to have carbs on an otherwise "stock" motor: Vintage racing.
I would have a megasquirt instead of carbs if the rules allowed it.

I still have to dyno my 2056 with a Raby cam and Djet as it should be in the 115-120 hp range. 25mpg and tons of torque....so who needs carbs as it looks totally stock.

Glad to see you posting once and a while Geoff.

[Gunn1]

As far as tit for tat ........I'm good!

No, no “tit for tat”, just a simple request for substance that you've repeatedly ignored. You said “Many of the Guru's (about 5 to 1) prefer carburation.“ Now that’s a surprising fact that you then used to infer that Porsche “effed up” by putting fuel injection on their engines, questioning the competence of Porsche engineers. Those are statements you made, so I’m just curious to know where you get this information, who you consider a “guru,” and why you think they’re better than the Porsche engineers. Simple enough. You’ve been asked several times who these “gurus” are and you have time to rhyme, so what’s the problem?

By the way this isn’t a new question, google “carbs vs. fuel injection dyno comparison” or anything similar and find lots of empirical comparisons complete with charts and graphs. Generally carbs can equal fuel injection at wide-open throttle, so a draw there, but fuel injection is more efficient and performs better at all RPM points below wide-open. Meaning the Porsche (and every other car manufacturer's) engineers were right, no surprise. As to the “look” and the sounds of carbs, those are purely subjective so really silly to argue about.

This thread has had more than five knowledgeable people weigh in on both sides of the issue.

I never considered this to be an argument, rather a spirited debate with the hopes of learning from those more educated than myself.

[Mark Henry]

My new 3.0 performance /6 has weber's, got them cheap in a trade.
Although I like FI, that's what I will run unless I'm disappointed with them.
Still hoping to get my car back on the road this year. (IMG:style_emoticons/default/unsure.gif)

[jd74914]

Your overlay graph is interesting as the tail off at high rev range may mean I need to look again at my Air Correctors, or it may mean that the two separate machines had slightly differing calibration on their ability to measure RPM? That’s an interesting thought as it would pull my early gain in torque in line with the D-jet, and push my late drop off in torque back to match the D-jet.

It's not unheard of for dyno engine speed measurement to be incorrect. There is a Dyno Dynamics brake locally which measures engine speed in error by ~200 rpm. We used to go and then scale all of the data back and recalculate torque at home. (IMG:style_emoticons/default/dry.gif)





If you compare the normalized curves, I'd guess one of the dynos was measuring off by ~225 rpm since the curves are nearly line-on-line with that shift. My guess is that the slope of the curve is different between yours and Geoff's because there is a slightly different driveline loss multiple (Cl) being applied. Given that, it does look like yours drops off sooner so there is probably some more carb tuning to be had.


For the record, I hate working with carbs...when you're on a dyno or tuning in general it's so much easier just to change a few numbers in a table! Well, at least until you work with something high end the likes of AER/Life Racing, etc. and they you have 20 tables to work with. (IMG:style_emoticons/default/laugh.gif)

[Racer]

Did Porsche eff up?

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

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

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

WHY DID THEY DO IT?????

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.

No mess ups.. it was "cutting edge" technology back in the late 1960s when the car/engine was coming together.

I can't think of ANYONE else who built and offered in 1970:

Mid engine
Electronic Fuel injected motor (911s had either carbs or MFI)
5 Speed syncromesh trans (even base 911s came with a 4spd)
4 wheel disc brakes
4 wheel independent suspension
Nearly 14 cu ft of combined trunk space
Removable Targa top

All for $4K ?

[gereed75]

Wait, There were some really nice 20 year old designs from MG, Triumph, and Fiat to pick from!!

The X 1/9 was a modern design but with a sub 2 liter carbed POS engine and midget driver space.

The 914 was serious engineering when it appeared. Very cool!! It was kinda "mini exotica" for the common man when cars like the Lambo Muira and the Pantera were the shit. And you could subconsciously link it to the all powerful 917!!

I do admit to some mid engine lust for the Lotus JPS Europa, but it was just too quirky for a street car.

[ClayPerrine]

(IMG:style_emoticons/default/dead horse.gif)

[Gunn1]

Did Porsche eff up?

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

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

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

WHY DID THEY DO IT?????

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.

No mess ups.. it was "cutting edge" technology back in the late 1960s when the car/engine was coming together.

I can't think of ANYONE else who built and offered in 1970:

Mid engine
Electronic Fuel injected motor (911s had either carbs or MFI)
5 Speed syncromesh trans (even base 911s came with a 4spd)
4 wheel disc brakes
Nearly 14 cu ft of combined trunk space


Removable Targa top

All for $4K ?

I know .....what a value for a cutting edge platform!