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Generic Fuel delivery question, EFI or carbs

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My base 2002 was modified over the years, part of it being fuel injection from a later BMW model, along with a DTA computer (very antiquated, that - I think it needs a Win95 laptop or some other antique).

The car starts well, has very good torque and HP, absolutely *abysmal* mileage, and the gas pedal is a bit of an on/off switch. I'm used to it, but am starting to question this setup because since I moved 3000mi away from the shop that did this, the closest shop that can retune a DTA is over an hour away - not a convenient drop off, and they did mention I was lucky their one laptop still booted to connect to this antique device.  

 

I am currently experiencing a lower idle (borderline stall when cold) and less good starting, and need to figure it out - the tune cannot change so it's probably something else (unless gas formulation summer/winter matters)... From a performance/cost/practicality perspective, would you: 

 

a) Leave it - a retune is cheap and normally not needed often - Most likely issues are "other stuff" since a tune won't change... 

b) Switch to another brand of modern EFI computer, cost/recommendation?  end result: more common tune-ability by a closer shop

c) go back to carbs: Better gas pedal feel by restoring original mechanism (less on/off), better sound, everyone can tune this, but new carbs are probably $$$ ?

 

The main Q here being can you make the same power with carbs than the boost I got with EFI on my car ? (it was significant, the car went from "ho-hum" to Tii levels and way way more torque - had dyno charts before and after).

  For fun / feel, which do you prefer ?  

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(edited)

That's a very good question,  I prefer the Megasquirt EFI setup, however, I may be in the minority.  Most people can and will be able to work on a carb setup.  

a) first check other mechanical items that may be out of adjustment (valves), or out of spec/worn out parts first, (spark plugs, ground connections, filters, fuel pump, etc...

b) Megasquirt, Electromotive, Haltech, etc..systems have a lot of support, as they are the more current and popular systems now.

c) Carbs will be a good option, however you are already setup for EFI,,  manifold, fuel pump, fuel lines, air filter setup, etc,  You would need to replace all those parts for carb(s).  Like ypu stated earlier  $$$  maybe one more $  ;)

 

The new EFI systems will give you more power and control of mixtures under all driving conditions.  Altitude, temperatures, and start ups. Obviously this my opinion and experience. 

Photos of your setup would be helpful to better understand your questions.

 

Cheers,

Matt

 

 

IMAG0804.jpg

Edited by Schnellvintage
Added info

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With your car already converted to efi I would think the path of least resistance would be to switch over to a more modern control system and upgrade the linkage for better control of the loud pedal. Sooner or later you'll lose access to the old windows program you need to tune the old system.

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Upgrade. 

 

How is the wiring to the ECU currently arranged?  Does the DTA control stuff directly or via relays? What difference in configuration is there between DTA and your new ECU? Same voltages? Same signals?

 

If the wiring all passes by a single location then consider whether or not you can terminate each wire on some form of terminal and then run new wires from your new ECU to these terminals for the equivalent wiring. 

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That: "Carbs: They're necessary and barely controlled fuel leaks that sometimes match the air passing through them." is a funny quote ! 

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This is a well adjusted Weber 38/38 and stock type distributor vs a 318i manifold, mega squirt, and crank triggered edis ignition system. Same stock Unknown mileage engine. Same dyno and similar conditions, though a year apart. Blue is the carburetor. 

 

DC350A6D-180F-4CD4-BC9F-DEB52531B4AE.thumb.jpeg.5d25388b2b6206755ce62e620466f148.jpeg

 

Difference wasn’t in power output. Drivability was decent with the Weber, but really good with the EFI setup. Cold starts we’re especially improved. I’ve never tracked fuel economy, but it was much easier to get the right amount of accel enrichment with EFI. Carb was either too righ or too lean at throttle tip in. Couldn’t get a good compromise.

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I'd say it depends what you're more comfortable working with.  Since you own a 2002, I'm assuming you have at least basic mechanical and electrical tinkering affinity.  I'm an avid proponent of Megasquirt, but I'll never say a bad word about carbs; they're very simple, elegant, and pretty darn good at what they do.  And if you already know your way around carbs (float levels, jetting, etc.) and are less inclined to dive into electrical and computer stuff, there lots of good 2002 carb setups to choose from.

If on the the other hand you really want to maximize the reliability, mileage, driveability, etc. and like tinkering with electrical/computer stuff, then by all means continue on the path to a better EFI setup.  Start by reading my full write-up on Megasquirting a 2002 here and feel free to PM me with questions. (I won't talk you out of a different ECU option but will certainly recommend the Megasquirt path):

 

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@bento, what cam was this with?  I find the low/mid-range torque curve quite interesting, as I could swear the longer 318i runners perform considerably better than the stock bunch-a-bananas manifold in the 2-4k range on my car, but I do not have the dyno data to prove this, and yours indicates just about the exact opposite:

image.png.d7555dd8d0724fd08a979cd01cf8abe6.png

I also agree with essentially no difference in peak power between the two though.

 

I did/do run a 284 reground cam with both manifolds though, so perhaps that is part of the difference?

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12 hours ago, AustrianVespaGuy said:

@bento, what cam was this with?  I find the low/mid-range torque curve quite interesting, as I could swear the longer 318i runners perform considerably better than the stock bunch-a-bananas manifold in the 2-4k range on my car, but I do not have the dyno data to prove this, and yours indicates just about the exact opposite:

image.png.d7555dd8d0724fd08a979cd01cf8abe6.png

I also agree with essentially no difference in peak power between the two though.

 

I did/do run a 284 reground cam with both manifolds though, so perhaps that is part of the difference?

 

That’s with a stock cam.

 

I swore until it was on the dyno that the efi setup felt more powerful in the low-mid rpm range as well. Maybe it’s crisper throttle response that we noticed?

 

I will say neither was tuned on the dyno. I just did a few runs to see what the numbers were. So maybe we left something on the table with overly conservative advance curve? We did do a fair bit of road tuning and had to pull timing out due to pinging at several places in the ignition map, so I doubt we left a ton.

 

 

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