Carbs vs injection?

[decampos]

Sorry if this is an old chestnut, It's quite a difficult thing to search for in the archives. Carbs or injection: is one generally preferred over the other with the E9s? Are the injected cars more problematic in any way?
Cheers
Ben

 

[x_atlas0]

It depends on if you are talking stock or modified. The stock Zeniths are pretty reliable, as is the D-Jet system. However, it seems like the D-Jet is aging much worse than the Zeniths, in terms of "repairability", due to the scarcity of old analog parts and the lack of remaining specialists for the system. If you are talking about a later Motronic system, it seems to be working much better, as it was used on more cars and parts are readily available.

 

[decampos]

Thanks for the info.

 

[jmackro]

This is kind of like asking whether the Yankees or the Red Sox are the "better" team - it is as much an emotional question as a technical one.

My 2800 came carbureted from the factory, and I would be reluctant to modify it even though a modern EFI system might give better fuel economy, smoother cold running, more power, etc. I also like the simplicity of carbs - you don't need an OBD II analyzer when the thing won't start. And, I just like the feel of driving a carburated car.

But, my modern cars have EFI and I have no desire to convert them back to carbs.

 

[decampos]

This is kind of like asking whether the Yankees or the Red Sox are the "better" team - it is as much an emotional question as a technical one.

My 2800 came carbureted from the factory, and I would be reluctant to modify it even though a modern EFI system might give better fuel economy, smoother cold running, more power, etc. I also like the simplicity of carbs - you don't need an OBD II analyizer when the thing won't start. And, I just like the feel of driving a carburated car.

But, my modern cars have EFI and I have no desire to convert them back to carbs.

Hi jmackro. Thanks for your reply. I was wondering if there was an 'avoid the injection models' rule or something like that (like some other cars of the era). Was just checking. I generally prefer carbs also. Love the induction roar though I don't know how pronounced that is on these engines.

 

[bmwmadman]

My coupe started as a standard carbed unit - 2800cs. But after the engine started getting tired and the carbs out of sync I took a leap to a 3.5 motor & 1.3 motronics EFI. All of this was installed by La Jolla. IMHO under the hood looks like a CSI but the performance is of a modern car. NO WAY i could ever go back.

 

[decoupe]

It's interesting that the m30 based engine has a series lifespan from the late sixties to the early 90's going from carbs and distributors to D and L Jet and a couple of Motronic series (3?) EFI. Add onto that list are some fairly exotic ITB race setups and the turbo charged engines and there is a lot of choices for you to chose from. Almost anything from the first 2800CS to the last M635i will fit (albeit with some creative work).

There are good reasons to pick from any of the above including originality, aesthetics and the sound of carb'd intakes threatening to suck small children off the sidewalks. Love that sound. EFI gives you more control and flexibility to really modify and increase performance delivery but at the cost of simplicity and authenticity (if that is a factor) to the era in which your particular e9 comes from. Sort of like comparing a roaring bonfire and a high efficiency forced air furnace. Both will get you hot.

It's all about choices and this is one of the beauties of this engine is that all of the options are all available to you and for the most part are direct bolt-on's to that m30 block. Sort of a time machine.

Doug

 

[thehackmechanic]

Injection

On my CSi, the previous owner had already yanked the D-Jet and put it in a box and put on Webers. I eventually retrofitted L-Jet with Lamda from an '81 528i, and I love it. I also like the fact that it's almost, but not quite, period-correct. That is, although the coupes didn't have L-Jet, the 1975 3.0Si sedan did -- same setup as the '75 530i. The later system differs only slightly in use of the oxygen sensor. I have nothing against Motronic conversions, but they do have a different look and feel when you open the hood. The L-Jet looks very similar to the D-Jet when you open the hood.

And, best of all, after not driving the car for four months, I hop in it, hook up the battery, and it starts right up and idles fine.

 

[gjm]

For me, this is one of the attractions of the coupé. Not just the good looks - that's a given - but also the interchangeability of the important parts. It can be more or less as original or as modern as you want it to be.

There's someone over here in the UK running an E9 fitted with an Emerald management system. Not a cheap solution, perhaps, but one that might appeal to those looking for FI.

For my part, we don't (yet) own an E9 but are looking. It'll be an automatic as a matter of necessity, which would probably be better with an injected engine; unfortunately the contender for our funds is a 3.0 CSA with poor running problems. (I've touched on this in the Classifieds section - it may not need replacement carbs but that would help rule out at least one problem and is much more economic than converting to FI.)

More news from us as and when it happens!

 

[jmackro]

My personal solution for the carburetor problem is a pair of manual choke Weber 32/36 DGV's. See: http://www.piercemanifolds.com/product_p/22680.005.htm From my experience, 95% of the problems with the original Zeniths, and water choke Webers have to do with cold starting & cold running - at highway speeds, just about any old carb will work tolerably well.

I was discussing rebuilding my water choked 32/36's with Mike Pierce, and he said: "heck, just buy new manual choke 32/36's - they're cheap". And he was right (as always) - at $200 apiece, they are less than the automatic choke models, and less than the cost of professionally rebuilding old carbs.

I mounted a choke cable below the dash, pull it out to start, push it half way in to run, push it all the way in when I hit the freeway, and I'm done. Sure, EFI would be smoother, but could you do it for $400?

 

[x_atlas0]

My personal solution for the carburetor problem is a pair of manual choke Weber 32/36 DGV's. See: http://www.piercemanifolds.com/product_p/22680.005.htm From my experience, 95% of the problems with the original Zeniths, and water choke Webers have to do with cold starting & cold running - at highway speeds, just about any old carb will work tolerably well.

I was discussing rebuilding my water choked 32/36's with Mike Pierce, and he said: "heck, just buy new manual choke 32/36's - they're cheap". And he was right (as always) - at $200 apiece, they are less than the automatic choke models, and less than the cost of professionally rebuilding old carbs.

I mounted a choke cable below the dash, pull it out to start, push it half way in to run, push it all the way in when I hit the freeway, and I'm done. Sure, EFI would be smoother, but could you do it for $400?

Yep, you sure can if you get a good deal on the tii booster or change the wiring a bit so it fits the L-Jet intake manifold. I did the whole Motronic 1.3 system for ~300$, including the tii brake booster.

 

[jmackro]

Yep, you sure can if you get a good deal on the tii booster.

No no no, you're thinking of a DCOE conversion. Yea, that takes a tii booster, custom intake manifolds, and 3 carbs at about $400 apiece.

The DGV carbs just bolt to the stock e9 carb manifold, and the throttle linkage works as is. Yea, you need a JAM adapter to use the stock air filter, but aftermarket air filters can also be used (though they are noisier, and don't look at all original).

 

[x_atlas0]

No no no, you're thinking of a DCOE conversion. Yea, that takes a tii booster, custom intake manifolds, and 3 carbs at about $400 apiece.

The DGV carbs just bolt to the stock e9 carb manifold, and the throttle linkage works as is. Yea, you need a JAM adapter to use the stock air filter, but aftermarket air filters can also be used (though they are noisier, and don't look at all original).

No, no, I meant you could do the Motronic 1.3 EFI conversion for less than 400$. You need the tii brake booster to clear the Motronic intake manifold.

 

[jmackro]

Oops sorry, guess I didn't read your first reply correctly.

So are you saying that Motronic 1.3 components will fit an L-jet manifold, providing a more modern EFI solution (than the older L-jet) that clears the stock brake booster?

Or, are you saying that if you retain the stock booster, you are limited to using the older L-jet system?

 

[x_atlas0]

Oops sorry, guess I didn't read your first reply correctly.

So are you saying that Motronic 1.3 components will fit an L-jet manifold, providing a more modern EFI solution (than the older L-jet) that clears the stock brake booster?

Or, are you saying that if you retain the stock booster, you are limited to using the older L-jet system?

The Motronic 1.3 wiring harness requires some lengthening and shortening to fit the L-Jet manifold. If you do this, you can use the original brake booster. If you use the Motronic manifold to avoid the wiring issues, you have to cut and channel the Motronic manifold or use a 2002tii brake booster to clear it.

 

[sfdon]

1972 cs body

1979 528i intake

1984 euro 3.5 10:1 218 stock horsepower engine

Schrick cam

ported and polished

1992 735i Motronic 1.3 adaptive

turner chip

 

[bill]

I just got done transplanting a 75 CSi D-Jet system into my 74 CS. So far it has been great. Helped to eliminate surge/hesitation problems that I could never sort out with carbs (new head gasket helped too.) I had Webers with auto chokes which worked fairly well, but when the 75 CSi parts car fell into my lap, with a working engine, I couldn't resist making the swap to D-Jet. But, we shall see how well it goes...(ask me how I feel when the brain fails and I can't find a replacement (I am keeping the Webers...))