Those corrected curves display what Brad Anders has always said.

It.s nothing new and the data doesn.t show anything different then most of the "guru.s" already know.

The engineers knew what they were doing.

The business decisions and reasons are also there too.

They didn.t just use D.jet on tje account that it sounded like a good idea.

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

At this point, and after everyone's input on the subject, I wouldn't.......

1. Reliability

2. Simplicity

3. The ability to use a non Bosch distributor

4. The look

5. The sound

All in all, what's wrong with using one or the other because you "Like" them.

Many times folks choose something because they like it, not always because it makes sense........

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?

Click to view attachment
Carburetor:Fuel metering device.
Fuel injection:Fuel metering device.
Same/same.

https://issuu.com/contact.magazine/docs/alt...volume_4_previe(turn to page 12)
How the internal combustion engine works,power is relative to the volume of air compressed.
Fuel burns at a ratio near 14.7/1 air/fuel mixture.
Charles Lindbergh flew fuel conservation flights to demonstrate that truth,no getting around it.(http://www.charleslindbergh.com/wwii/)
The new DFI allows very fine resolution of lean running conditions to alter that 'truth'.
Cruise condition cylinder switching allows a smaller fuel burn for greater range and emissions performance.
All good,the carb,much better than the Wright Brother's 'fuel plate',is a thing of the past in the 21st century.
So,go with what you know,for ease and price.

1. My FI engine starts immediately with every turn of the key. No matter if it's freezing outside or boiling hot or if i'm at sea level or 10,000 feet up.
I've had this engine for 10 years now with only changing oil every once in a while and changed the spark-plugs once.

2. Have you ever dis-assembled a carb?

3. OK

4. Personal preference, i quite like the look of my engine.

5. I'll give you a ride in my car and we'll talk about the sound again afterwards.

Fixed it.

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.

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.

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.

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!

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......

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!

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 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.

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.

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.

Glad to see you posting once and a while Geoff.

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.

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.

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.

Click to view attachment

Click to view attachment

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.

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 ?

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.

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

Thanks jd74914, again great work on the data, and it makes complete sense with my gut feeling that the two Dyno traces had an inaccuracy somewhere in RPM.
I agree about a little more fine tuning on my particular car might be needed just to delay that drop off in curve at the end. That's why I'm hoping someone out there has a D-Jet stock AFR trace so I can see it's fueling. I'd guess I need to lean off my AFR post 4500RPM to get an exact matching D-jet curve (it isn't far off mind you already). But to be fair, I don't plan on sustained running at those RPM's. I have more of a classic car Sunday cruise plan for my 914, as I've got other big brutal monsters in my garage already that'll pass the 200mph mark and set my pants on fire, so don't need to prove anything with this 14. :-)

You don't want to match a stock djet afr trace!

The actual fuel used today is a much different blend than the blend that cars were set up for by the factory

Whether it's a difference in fuel blend or the factory's tune for emissions and economy. The stock are trace is not ideal.

I retune my stock fuel injection for a more rich mixture and still get 31-32mpg on the highway (1974 2.0)

I have another dyno chart somewhere and the AFR is pretty flat at 13.5 to one upto 5500rpms

Hi Brant, I think I didn't explain well or the meaning in my post is mis-understood. The D-Jet curve I'd like to match is the end of the HP curve, where it looks at the moment mines dropping off early. The AFR of the D-jet I'll never be able to match as the car would always want to run richer with carbs.
I'd like to see the AFR of a stock D-jet just for curiosity and to gain knowledge and understanding of the "benchmark" and also as a comparison to what happens to the AFR through the rev range when you fit carbs.
I agree totally that stock classic car engines (of all types) on modern fuels and with a good few miles under their belts often benefit from running a little richer than 40 years ago when they were new and running on older fuel types and blends.

Geoff,

If you have another graph with AFR trace that would be brilliant! Better to have your trace as it goes with the data you already posted so the best info we could have!
Thanks in advance

Hey fellas, what's the best oil for air-cooled motors?

Oh no you didnt....

It depends on which tires you are running...

And on the tenth page,they lost their minds.




/

Click to view attachment
(aircooledtechguy pix),T4 exhaust,section thru studs.

The beauty of the DFI is the lack of cylinder wall washing by raw fuel,improving ring life.
Drill and tap a hole into the chambers,preheat and tig weld the barrel from the chamber side.
Final drill and tap for the DFI injector,then,machine the head complete.
A dry flowing int port can be reshaped,without the unatomized fuel pooling out of suspension.
/
Click to view attachment
T4 intake,section thru valve guide and seat.


Good pix of the T4,T1 heads in sawn sections,as above.
http://www.thesamba.com/vw/forum/viewtopic.php?t=602256
Unlike the second plug proposal,a DFI install ought to enter the chamber from the intake,"fat"part of the chamber.
Could it be as good as 20HP/TQ across the graph?
/

Brant can I run a 205 series tire under stock fenders? What size do you guys like? Hope this hasn't come up before.

Maybe Chris. Depends on your wheels and the chassis.

Idiots!! [grumble, grumble] Use the gotdamm search function!!

Oh yeah, the horse! Gotta take out some of this hostility and abuse that poor long-suffering horse!!

Since we are digressing...
Always thought the six-stroke engine concept would be cool to apply to an air-cooled engine:
http://autoweek.com/article/car-news/insid...x-stroke-engine

An additional set of strokes is added to inject water into the piston. It turns to steam from the stored heat of the piston, so it gives an extra power stroke while cooling the cylinder at the same time.

Interesting article.

Click to view attachment
The main crankshaft with one(of four) rod and piston. The power is taken off this crankshaft while the top crankshaft operates the small top pistons to give favourable port openings. (Cars and Drivers)

https://primotipo.com/tag/bob-chamberlain/
Well,this '40s engine type would now be a viable proposition with the DFI tech available today.
Swinging the twincrank to beyond 12K,with fuel efficiency never before possible.
A moment cancelling design,smooth.

/

Very interesting Veekry9,

While we're going off course a little...

I was an Engineer in the Navy for 18 years and one of our engine types was a Napier Deltic, I led teams rebuilding, replacing and maintaining them. They had opposing pistons and 3 cranks in a delta (triangle) layout.

https://en.wikipedia.org/wiki/Napier_Deltic

I also worked on an array of gas turbines, from full tear down and rebuilds to straight replacements, and general servicing. These included Early marinized Rolls-Royce aero engines, Tyne, Olympus (same engine as our Concord jet plane had) and Spey, I even qualified in the Harrier jump jet Pegasus too. We also used the Rover turbine (as a fire water pump) I rebuilt a few of these too. A very similar Rover BRM basic design copy engine was used in the Howmet race car.

https://www.youtube.com/watch?v=GAgLSy371us

I've actually help fix one of these gas turbine race cars in the paddock at Goodwood!

The complexity of the Fueling systems on these babies would blow your mind in comparison to D-jet :-)

The REAL question is "Why did they design an engine that needed oil?" Did they Eff that up too?

Click to view attachment

Ah Oil is thicker than water!

Yeah,the Moon had not yet been traveled to,and turbine and Wankel engines were going to be the next big thing.
Today,I would surmise the vast improvement in materials would make a turbine/electric/magnetic/hybrid car
a marketable space age set of wheels.Heck,you could run it on recycled cooking oil/kerosene/mdo.
A set of igniters in each cylinder,to initiate a more complete burn will likely be the next big improvement for piston engines.
High temperature magnesium,whodathunkit?I'd like to see the response a lightweight reciprocating mass as applied to the
aircooled engines would have.The crank could be lightened substantially,piston velocities near or beyond what F1 is attaining today.
Something old is new again,the Napier is a diesel in the marine application I would guess.
Diesel with solid state spark ignition,when was the last time that was tried,I wonder?
Mg:
Cost, pure: $3.7 per 100g.
Cost, bulk: $0.29 per 100g.

http://www.hotrod.com/how-to/engine/hrdp-1...t-vapor-engine/
https://www.google.ca/webhp?sourceid=chrome...+piston+engines
https://www.google.ca/webhp?sourceid=chrome...car+documentary
With the modern control of fuel by electronic means,EFI,the leanout of the chamber could be attained,a temp not possible then.

Appears you've had your sea legs for a lifetime.
Been to the Bay o' Biscay?(Cockney)
https://en.wikipedia.org/wiki/Rogue_wave

Dupe post Never mind