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Discussion Starter #1
Does anyone have experience converting fuel injection to Webber carbs specifically on the 2.0 liter spiders? Is it better to modify the existing fuel injection, or go with ITBs. Personally i love carbs, but on these motors in particular, do they respond better to modified injection, ITBs, or carbs? Would love the opinions. I'm ready to clean up my induction system the stock layout could use some help.
 

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What year car do you have? The non-North America Spiders never had Spica or Bosch L-jetronic and they made at least 10 HP more than the emission controlled FI cars that we got in the States. Converting an S2 Spider (through 81) to Webers is fairly easy. Converting an S3 is more difficult if you plan to keep the cylinder head.

FI vs Webers is almost like Christianity vs Islam on the ABB. From my own experience of driving a Spider with Webers and a GTV6 with Bosch L-Jetronic is that I have a strong preference for the Webers and I will soon ditch the L-jetronic on the GTV6 and go to Megasquirt programmable FI. But I like to develop and get more power out of my cars. If you want better gas mileage and the ability to pass an emissions test then stock FI is your friend.
 

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But Mad North-Northwest
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As a guy who has both, you'd have to be NUTS to ditch L-jet for carbs. Webers are fine if you have 'em, but EFI has way better driveability across all conditions, it's better for your engine, plus it gives you better economy and emissions.

If you're thinking you're gonna bolt on Webers and gain a bunch of power you're misunderstanding how fuel systems work. You can't just dump in more fuel and expect to get more power. There are plenty of physical engine mods you can do to improve performance somewhat, but those will work even with the stock system (hell, do a search for supercharged Alfas with stock l-jet: it's been done)

Tom Sahines and Wes Ingram gave a talk for the Alfa club here and had some great advice: they said the best fuel system for your Alfa is the one it came with. I would heed their words.
 

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As I said, the European motors made at least 10 Hp more than the US models with Spica or L-jet and for some years it was close to 20HP. Part of that was the cams but a lot of it was due to the emissions system (FI). If you live in California and have to pass emissions your options are limited. My 2L motor with cams, pistons, Webers and a ported head makes 169HP and it will make more when I fix the restrictive exhaust system. It made 111 HP when it was delivered to the US with Spica. The question is do you like power or emissions compliance? In South Carolina you have that choice.

My 3L V6 "S" motor probably makes about 200 HP and there is not much more available if I stay with L-jetronic. I have cams that will probably make at least 250 HP but L-Jetronic will not manage it because it is based upon meeting emissions regulations. Fitting programmable FI will make it fly like a free bird.
 

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But Mad North-Northwest
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That euro difference was cams and a lack of a cat converter, not the fuel system, Ed. Beyond the cat converter, there isn't any "emissions" stuff in the L-jet system, at least not anything that affects power.

You're misunderstanding how the fuel system works. You can't just bolt on Webers, dump in more gas, and expect more power.
 

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you'd have to be NUTS to ditch L-jet for carbs
Richard Jemison won an SCCA GT2 Championship with an Alfa GTV6 that hade been converted from L-jet to Webers and made 300 HP. Do you really think that was NUTS?
Ed. Beyond the cat converter, there isn't any "emissions" stuff in the L-jet system, at least not anything that affects power.
L-Jet and Spica are designed to supply an accurate air-fuel mixture to an engine that they are specifically set up for, that produces low emissions and low fuel consumption. That AFR is leaner than the mixture required for maximum power. When you replace it with something that will supply an AFR that is optimized for power then you get more power. Case in point:
In the early days of L-Jet, Tom Zat, Fred DiMatteo and another guy who's name I forget, figured out how to modify the L-Jet ECU to supply more fuel to the motor and hence get more power. Tom's "Pandora's Box" with a modified air fuel meter was a product of that. RJ's route was Webers. Later on Al Mitchell raced a GTV6 and spent 3 years modifying L-Jetronic to get more power. Then He switched to megasquirt and never looked back. He now has done many Megasquirt conversions on 6 cylinder Alfas. He has found that simply replacing the L-Jetronic with megasquirt and doing nothing else, gets about 30 HP more from a 3L motor. Some of that is due to the elimination of the restriction caused by the AFM and the rest of it is due to supplying a mixture that is optimized for power and not emissions. L-Jetronic sacrifices power for low emissions.

Now consider what happens when you modify an engine that has SPICA or L-Jet.
Unlike a carburetor, SPICA does not measure air flow. It calculates an expected flow based upon throttle position and rpm. That calculation is based on a volumetric efficiency number for the engine that it is supplying. If that number is correct then it will accurately meter a mixture that will produce low emissions that is too lean for maximum power. When you raise the volumetric efficiency by using a different camshaft to increase valve lift or improve the porting or reduce the restriction in the intake/exhaust systems, the SPICA has no knowledge of that. It continues to supply a mixture that is now even more too lean. It will not allow the engine to make the power that it is capable of. In this case fitting Webers makes a huge improvement. My Spider motor is testament to that. Wes Ingram will sell you an HP SPICA pump that will deliver more fuel and can supply engines with a higher VE but that too has it's limitations. Gigem75 really wanted to make the HP pump work on his high out put motor and I understand that Wes worked with him on it but he could not get it to supply enough fuel and he finally gave up and fitted Webers and his motor now produces the expected power.
L-jet does measure air flow and it computes a fuel signal based upon an analog model of the engine. If you increase the VE it will supply more fuel and that is good, even though it is not the amount needed for maximum power. But the extra fuel that it can supply is limited. Richard Jemison sells cams that will work with L-jet and they produce a modest increase in power. But L-Jet cannot handle bigger cams and hence it puts a cap on HP. The motor will run very lean at high rpm. He and others have tried installing bigger injectors to provide sufficient fuel at high rpm but them it runs much too rich at mid-low rpm. Hence the move to Megasquirt.
Most of the L-Jetronic systems are now at least 25 years old. The AFM's that were once accurate now are not so accurate. The contact between the wiper and the conductive track deteriorates and it supplies an erratic signal to the ECU. Connect a VOM to the output terminals of one of these and slowly move the flapper. There will be places where you get a nice steady change in resistance and there will be spots where it jumps around. I have tested 6 of them and they all exhibited this problem to some degree.. AFAIK, you cannot buy a new Bosch AFM so you are stuck with a system that is getting worse with age. My GTV6 is in this category. It is going to get Megasquirt.
You're misunderstanding how the fuel system works
You are dead wrong there.
 

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But Mad North-Northwest
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Okay, Ed, I'll grant you that you know some stuff. Sorry if I was flip with you.

I stand by my advice for a street car, though: you'd have to be nuts to replace EFI with carbs. Just in terms of driveabiluty and engine life, for Pete's sake. I mean, Webers are fine for what they are, but the AFR is all over the place on 'em as conditions change. The Giulia is Weber'd: they work, but I feel like they're always a compromise, and I'd go to L-jet in a heartbeat if it were simple (and not a '63 Alfa!).

I wasn't talking about SPICA or Megasquirt. I am familiar with SPICA's limits, and as you said Megasquirt would be a much better option in a modified engine than either l-jet or carbs.

FYI, there's nothing wrong with your AFM if the resistance jumps around as you move the flap: that's the wrong way to test it. It's not an age thing, they apparently did that when new. If you measure the voltage output it'll be smooth, but this requires a voltage source and a different procedure:

Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk  ?2001 www.the944.com

So the good news is your pile of AFMs are probably fine :D
 

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Hopefully we can agree on the following:
SPICA and L-Jetronic FI systems are precise and if properly maintained will enable your Alfa to perform to it's original specification with relatively low fuel consumption and emissions. Replacing either system on a stock motor with Webers is unlikely to produce noticeable power gain and will certainly result in higher fuel consumption and emissions.
Webers are less precise but more adaptable and are a popular choice for modified, high output engines where fuel consumption and emissions are not a concern. They are relatively simple to tune and maintain,
Programmable FI such as Megasquirt is both precise and adaptable and is a good choice for someone who wants to develop an engine for maximum performance.
 

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Discussion Starter #9
Thank you for your insights. I ask because on some v8 applications i have experimented with, I have seen power gains in some cases close to 30HP converting to carbs. This will be my first time experimenting with a 4cylinder DOHC. I enjoy building custom intake manifolds on occasion to try to gain more efficiency, so in this case it sounds like i will stick with carbs. In the future i would like to try ITBs though. Carbs just prove to be a little more cost effective in most cases. Thank you for your input guys! I will keep it in mind.
 

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Speed is always money and the question is always,

How fast can you spend?

I have webers on my car; the P.O. used a webers-SPICA-manifold conversion kit with K&N filters. I played with it for about a year and never got it to run right, even after replacing the fuel pump, and replacing the fuel pressure regulator, and adding a Euro plenum, air box and cold air intake. The only thing that worked was installing the Euro manifold and the Euro cams, and then rejetting the carbs to suit. The short version is I spent a lot of money to get a car that runs very,very nicely, but still doesn't have more power than an original Euro version of my car.

Unless you are planning on building an engine that has fuel demands greater than your injection system can handle, I can't see the weber conversion being an advantage. Even then, if I were dumping a couple of K into a already fuel injected car, I think that an ITB system would give more bang for the buck unless you are going to keep modifying the engine. That (IMHO) is why the racers prefer carbs. They can more quickly and easily be 'remapped' to suit engine changes than an FI system.

I love my carbs but I don't think I could recommend a casual driver just in search of a little more umph to make the switch.

FWIW
 

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But Mad North-Northwest
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Well, yeah, that's the question: what exactly are you trying to do, Joe? What's your goal, and how much do you want to spend?

I can tell you that you're not gonna get that same V8 +30HP out of a 120HP 2-liter engine just by switching to Webers. The Euro Weber'd cars had, what, +10HP? And that's with no cat & different cams, so it's not even apples to apples: do the same mods with stock L-jet and you'll probably see the same results.

Despite what folks seem to think, the L-jet system doesn't run the engine lean. It runs stoichiometric at idle and part throttle and is already designed to go rich at WOT for power. So like I said, just bolting on Webers and dumping more gas in isn't a solution: you need to think about the engine as a whole.
 

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Discussion Starter #13
I think its fair to say that its obvious that i'm not going to get an extra 30 horse. Its the idea of improving intake flow and having flexible tune ability. The idea for my project is to find an extra engine+trans to build. I plan on fully rebuilding the bottom end and balancing and blueprinting it. As for the cylinder head i will try to find aftermarket cams, springs, and, valves. Also, fully port and polish the cylinder head. But, for now i will just make the intake manifold and stick with the carbs and, bolt a header+custom exhaust on (no cat). As far as how much i want to spend i dont think it matters considering the fact that i only got it for 1800 dollars, so with that said i think i can put 6gs maybe more into the car.
 

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Does your car currently have SPICA or L-Jet?
 

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Discussion Starter #15
I wish i knew. How can i tell? By the way i just found a megasquirt 1 on ebay for about 300 not bad. maybe i can do ITBs.
 

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But Mad North-Northwest
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What year's the car? You should probably put that in your signature: makes troubleshooting easier.

I'm gonna feel dumb if it's a SPICA car. I could've sworn I saw L-jet in your post.
 

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Discussion Starter #18
My alfa is an 86' spider veloce does that help? i hope it does cause i dont know how to tell the difference between injections? I think i may try the itb route... i found megasquirt 1 for 300 on ebay and also found 4 42mm itbs for about 500... i have never installed megasquirt or itbs sounds like a fun project...
 

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But Mad North-Northwest
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Okay, with an '86 (assuming someone didn't already fit carbs!) you've got Bosch L-Jetronic electronic fuel injection. It's a multiport EFI setup.
 

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Discussion Starter #20
Okay, with an '86 (assuming someone didn't already fit carbs!) you've got Bosch L-Jetronic electronic fuel injection. It's a multiport EFI setup.
:thumbup1: no worries i didn't do anything yet... So, the l-jetronic is better than spica?
 
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