Carb Tuning - EMPI 32/36 DFEV

[Mrgonzalo]

Hello all,

I searched through some of the older threads about tuning on these carbs, and was not able to find a definite answer... Hope I'm not beating a dead horse.

My 1980 2000 has been upgraded with a EMPI 32/36 DFEV and an 1800 intake manifold. When I drove to CA, I found that the car was running a bit rich. I followed Weber's tuning instructions, but the engine will not function smoothly unless I fully close the idle mixture screw and tighten the idle speed a couple of turns past the recommended amount. At this point, the car will idle on Park at about 900 RPM.

1. From what I've read, the jets might be too big. Is this an educated assumption or should I be looking elsewhere?
2. After the tune-up, I am getting horrible gas mileage (we're talking 16-18 mpg at 65-70 mph). Input?
3. Fast idle screw should not be touching the lever at all, correct?

I will also need to have the car pass CA Smog test. All emission-related equipment has been removed. Because of the fact that an exemption applies to my case, I can register the car as a 49-state vehicle (but still need to pass smog).

4. Anyone familiar with emission standards - any blanket recommendations here?

Thanks, and hoping to hear your input!

[So Cal Mark]

if you have the mixture screwed closed completely then you're getting fuel from another circuit. The most common problem is that the idle is too high. Opening the throttle with the speed screw will cause fuel to trickle in from the main circuit. If that's happening, it's impossible to set the idle mixture properly. The other issue could be the secondary stop screw is misadjusted, allowing the secondary throttle to stay open, creating the same issue as the primary throttle open too far. If both throttle plates are completely closed, you could have a misadjusted float.
I've found the 32/26 are usually a bit on the lean side for a 2L motor but every motor is different and altitude has a big effect also

[Dombrockt]

When installing the DFEV on my 2L with an 1800 manifold, I ran into 2 problems, one of which Mark described. The secondary throttle stop was backing itself out allowing the engine to pull fuel from the secondary at idle. Made it impossible to get a good tune. After resolving that issue I started on the idle jets. For my engine, the stock jets were a bit too large. I first started tuning with the vacuum gauge only, and it ran fine with the stock idle and main jets. However, when I plumbed in an 02 sensor, I learned that I was idling much too rich, as well as cruising in the 10:1 range. The engine seemed to accept where the jets were at, but the mileage and smell were awful. I tuned with the 02 for idle and cruising, and was able to improve mileage, but didn't get to finish before I put the car away for the year.

[Dombrockt]

Also, as Mark stated, the float setting is a smart place to start before getting too wild with the jetting.

[Mrgonzalo]

Gents,

To give you a bit more info... Regardless of the mixture adjustment (anywhere from 4 turns from fully-seated to fully-seated) the engine will die off, unless the idle speed is at least 3 turns from the fully-seated position. Unless I am not grasping the concept, this would lead me to believe that the idle speed adjustment is not the source of the problem (since without this amount of turns, the engine shuts off) but rather a symptom of it.

If this is correct, then perhaps I should look at the other possible issues you mentioned in the following order:
- Float adjustment
If within specs...
- Secondary speed screw
What is the recommended adjustment here? Haven't found any info in the specs. Also, can you point it out in this diagram? http://store.cip1.com/Merchant2/graphic ... 36DFEV.pdf

[So Cal Mark]

if you have the mixture screw fully seated and the idle speed screw wound in 3 turns then you are running on the main circuit at idle and low speed

[Mrgonzalo]

Understood. Unfortunately at my current level of knowledge (straight up beginner enthusiast) I am not sure where to start in order to correct this, considering that manufacturer's settings will not allow my car to run.

[tartan18]

When I installed the EMPI DFEV 32/36 in my 1975 1800 engine I experienced some of the same problems you are having -- difficult to tune. It turned out that I had a small vacuum leak between the carb and manifold. Once I tightened things up the carb turned in perfectly. Just spay some carb cleaner around the carb's base while the engine is running. If the idle improves you have confirmed a leak.

[Dombrockt]

It sounds as though some of the basic settings on the carb may be off. In my experience, there are a number of different things that can be wrong. The key is to start simple, and make sure all your basics are checked and double checked. Is your timing off? That can affect your idle speed. Is your throttle linkage binding? Allowing full movement both directions? Are you off the choke? I had friction in the throttle linkage that wasn't allowing the set screw to contact the throttle stop. Hard to set throttle stop if it doesn't touch. Also, the idle stop isn't only meant for setting the idle speed. It is also to ensure that you aren't idling on the main circuit. There are several small holes in the throat of the carb, and when the idle adjustment makes contact with the linkage, just the very outer edge the the first primary progression hole should be exposed. On a DFEV, this is usually less than 1 1/2 turns in. Set this, and don't touch it again! From there, set your idle speed with the mix screw. If you have a vacuum gauge (and you should), hook it up to the spark advance port on the carb. It should read 0. Definitely no more than 2". If it reads more, you are idling on the main circuit.

A decent reference:
http://www.redlineweber.com/html/Tech/c ... _best_.htm

An awesome reference:
http://performancecarbscience.com/
Absolutely worth the $10.

[Mrgonzalo]

Thanks for the tips, gents... I will work on these and report on the results.

[bradartigue]

The car should run on the mixture screw alone at around 650 - 700 RPM, the idle speed screw then bringing it up to around 150. To achieve this you typically have to work backwards, since cars don't like to run the mixture is bad, turning in the idle speed screw a couple of turns, getting it running, then getting the mixture right, then backing down the idle speed, then readjusting the mixture, and repeat a few times.

The correct idle jet is known when you can adjust it rich or lean with 2-3 turns from seated. In other words, that mixture screw should only need to come out 1 1/2 - 2 full turns to find a decent mixture, then fine tuning from there.

Air leaks will prevent you from achieving a low idle on the mixture screw and typically make the engine "wave" up and down in RPM.