engine and drivetrain Does your 32/36 with C.D. jetting suck...

[robsanab]

a lot of gas???

for those with C.D.'s prescription... I discovered something very interesting and perplexing. I am getting very poor gas mileage... this is with a brand new carb. The tech at Pierce Manifold recommended I start by resetting the float from 40mm back to stock 35mm. I did so and was then able to adjust both the idle screw and the mixture screw right within spec per Weber's and other literature's recommendations. Not that what I had was that far off... both were only about one half turn out further than the maximum recommended. Engine still runs the same but my gas mileage improved quite a bit.

My problem is STILL very poor gas mileage however. My previous 32/36 was stock jetted and leaked air around the throttle plate shaft. With it I still had decent throttle response... decent, but rough idle... no flat spots that folks talk about... and I was able to get 19-20 city and 25-27 highway with a 4 sp. Now with this new carb: Resetting the float enabled me to reset and fine tune the screws as stated above and my gas mileage improved a solid 3 mpg city and 2 mpg freeway... I now get about 16 around town... 20 combination and 22 all highway (and yes, with electronic ignition, new ignition parts and tuned/timed. Not too long ago the valves were adjusted and compression was good and even among cylinders). Not very good mpg considering I don't drive her very hard... and what others of you seem to be getting. I have even tried full tanks driving like a grandma and it doesn't improve. Also I didn't experience a significant increase in power going from my old carb to the new carb with C.D. jetting. The reports I hear from you all is that this setup should get 20-28 (and that includes spirited driving) and that it kicks ass compared to the stock jetting.

Point is: I get significantly worse gas mileage than my old leaky stock jetted carb.

I'm thinking about going back to the stock jetting... and starting fresh from there... unless someone else has another suggestion. I was just hoping that The Prescription would have been a nice place to start and then tweak from there.

I mainly wanted to report to yall the difference the float level made in my instance. Why is that? What's going on? I have no vacuum leaks that I can find. I found some leaks and plugged them up AFTER replacing the old carb... so if anything I have fewer now than before at least. I don't know why my new carb can't work efficiently at the 40mm float setting. So maybe my compression is lower than ideal? I am not creating as much vacuum to justify C.D.'s 40mm float spec?? My spark plugs aren't telling... they seem to show everything is as pretty good.

[Slavs]

The 32/36 will give you 17-19mpg (Alll Around)with 4 speed despite many of the claims on this board. There is no way it can ever get better mileage compared to a stock single barrel Solex which yields 21mpg (All Around) for the stock 2002. Many of these people are relying on their fuel gauges rather on what they actually have in their tank. Most of them don't realize that there are at least 2 different sizes of fuel tanks for the 2002. Roudie cars have 12 gallon tanks while squares have 13 gallon tanks. You got to use the right tank size for your calculation.

If sidedrafts are econo-carbs along with high compression pistons and long duration cams, then BMW would have designed the 1502 to have these features. On the contrary, each one of these modifications will lower a significant portion of your gas mileage. The 2002ti was rated at 16mpg by the factory.

Slavs

[TJs692002]

I am really happy with my 32/36 and C.D.'s jetting.

However I went from the stock Solex to the Weber.

What is your altitude? I think the jetting is set up for sea level but I am not sure. I know my 02 is great in Sacramento but looses the pep when I am in Tahoe.

I do not know what mileage I am getting because my odometer is broken but I can go about 200 miles or so on a tank. I drive 25 miles a day round trip and it takes about 8-9 days before I hit empty.

Sorry, your not as happy with your set up as some of us are.

[Guest Anonymous]

I have the weber setup on my 1600 (02 engine) and upgraded differential

(not original 4:11 gears).

My fuel mileage is averaging at 25.

It is a daily driver in all types of traffic conditions.

Check choke setting.

[Guest Anonymous]

I have the weber setup on my 1600 (02 engine) and upgraded differential

(not original 4:11 gears).

My fuel mileage is averaging at 25.

It is a daily driver in all types of traffic conditions.

Check choke setting.

[robsanab]

choke is OK... fully open when warmed up and I'm at sea level pretty much.

As stated I have gotten pretty good MPG with my previous 32/36... so I have a good reference point. I know how to figure gas mileage and my speedo is right on according to the mile marker method.

[winstontj]

i have a 3.45 rear end and a 5-speed with stock motor and 32/36 to cd's settings. I only noticed that the flat spot went away and things seemed smoother when i made the change. No real change in fuel milage. Biggest thing to watch is how progressive and exactly when and where the second choke opens up. For me, normal driving (70/30 hwy/city) gives me 31mpg. City only is about 25, highway only is about 32-33. When i drive like a jackass I'll be lucky to get 15mpg. Be mindful of dipping into the 36. You can feel it in the accelerator. Also, carburetors are not hybrid vehicles - you are using OLD technology to try and get new tech. milage. What about looking into an EFI system? Also other things like vacuum leaks, spark plugs, ignition, timing, TIRE PRESSURE, air dam, how fast you accelerate, how fast you drive on the highway, etc. all have an effect. I know you said your car is in tune and you run an electronic ignition but I think your numbers are fine. Sounds like you need to just lighten your foot a little.

Also what diff are you running? do you have a fuel leak? even one you don't know about? has your diff ever been changed without re-calibrating your odometer? I'd be happy with 25mpg highway with a 3.64 rear end. that's good.

[KFunk]

I've got a 32/36 w/CD on my 4-speed '74 with original 3.64 and a hell of a lot of miles and half-assed tuning...

And I've been getting 16-18 MPG around Honolulu dense traffic, and on my cross-country drive it usually got 24 MPG. Somehow I managed to get 28 MPG once, but I think that was when I descended the Rocky mtns.

I may try that with the float sometime, if there's no negative results.

[winstontj]

KFunk & robsanab,

What exhausts do you run? KFunk don't you Auto-X? How hard are you driving? I can get 10mpg with my 32/36 if I try and drive HARD. There are many factors and if you're running the stock setup the 32/36 isn't meant to be an economy upgrade it's a performance upgrade and performance = sacrifice. You can probably get better milage but you'll have to also sacrifice elsewhere. What tires do you guys run? I posted a thread about tire width and economy a little while ago. Fatter tires = worse milage. If you do the following you'll get an average of 25mpg and that's about as good as it gets with a stock 4-spd, 3.64 & 32/36....

remember it's the DRIVER more than the car that gets the milage because YOU open and close the throttle not the car.

#1 - engine in proper tune per manual. (valves, timing, plugs, points)

#2 - C.D.'s prescription, plug the correct hole, use good air filter

#3 - tire pressure at minimum 30psi but 32-35 is better

#4 - correct fluids in crankcase, gearbox & rear diff

If you have all of the above and you still can't get over 16-18mpg it's YOUR FOOT not your car.

[reuben2002]

I get pretty consistant 23-24mpg with my 32/36, which I thought was pretty low, but with the four speed and 3.64 gears, I can see now that it should be great. I removed the whole choke assembly on mine, seems to run much better. If you notice, C.D.'s jetting is quite a bit larger on the secondary, so reduced fuel mileage over stock jetting is to be expected. If you're really concerned, get an assortment of jets, and go to a shop with emissions equipment, and you should be able to fine tune the 32/36. Obviously C.D.'s presciption won't be ideal for every setup out there, but it is a good benchmark. As for float settings, it depends on what float you have. For my float, the Weber book I have says 40, not 35. Good fuel mileage is not a plug-and-play item for a 30+ year old car, and will require some work.

Reuben

[robsanab]

all points taken... I do realize there are many variables… and I feel I’ve taken them a lot into account (I didn’t mention that I have a 3.64, I’m at sea level, and the float is plastic and is what CD’s 40mm is based on, etc.).

Winstontj- your items 1-4 are affirmative… problem is I’ve taken my foot into account as well… that is the one variable I am able to monitor frequently and quite accurately I might add… IT is NOT because I put my foot into it MORE.

Slav and Winstontj…. True, I don’t believe everyone’s calculations, which are wildly varied (just like the condition of these cars), but it’s not based on anyone’s calculations… this is from my experience. Whether I figure gas mileage correctly or not, it was figured the SAME way BEFORE and AFTER the carb change (And with the same tires if that matters… and I always check my air pressure… besides will that make a 7mpg difference?).

Slavs- it is possible to get a fairly accurate MPG… I did it by verifying my speedo was indeed correct… even noticing on long trips that the odometer was very close… and then not going strictly by the odometer guesstimate method but actually logging what went into the tank and what was used… not by tank size/fuel gauge estimating. Again, with the old carb I got much better MPG.

Old carb: 20-27

New carb: 16-20 (2-3 less with the float at 40mm)

It is stated by CD that this is a performance upgrade that can get as good or maybe better gas mileage... mine plummeted significantly. Yes, he does say IF you can keep your foot out of it… I’ve already addressed that one.

So, I don’t think my expectations are too high… I stated what I was getting with the old carb and with the new carb… my average went from 25 to 18. That was the drop due to changing out the carburetor.

BTW… I’m not here blaming CD prescription necessarily… I’m just putting this out there, with the interesting experience about the float level change to see if that makes sense to anyone or if someone may know what condition may cause that to happen. I thought it might be telling. Maybe there is something wrong with the new carb? Maybe it points most definitely to a vacuum leak or other. I’m trying to avoid taking it off and shipping it back to Pierce… it’s my only car for awhile… and it’s getting to be wet season… damn.

[TJs692002]

I have the brass float set up to what Pierce recommends 35 or 32 or I forgot. I am wondering if the others that are also happy with cd's jetting are using the plastic or brass float? This might make a difference since changing your plastic float level from 40 to 35 helped improve your mileage mabey the brass one will do even more.

[KFunk]

My car has aftermarket headers and exhaust, but don't know the brand. Some german kind that starts with a B, but I couldn't read the rest of it.

Yes, I autocross and run the crap out of my car and it has to hurt the mileage some. I don't even get that great of mileage out of my miata, either.

[kamil]

I own a 1975 '02 automatic. i recently installed a weber 32/26. at the same time i also desmog it by removing the CA smog exhaust manifold and replacing it with a 72 tii manifold. my carb runs quite rough. the engines shakes and the carb kinda pulse's i believe th problem could be related to the vacumn. the mechanic who instaldled my weber did not do it right. seem the vacumn hoses are all messed up. does anyone have a diagram of how to connect all the vacumn/air hoses correctly with a weber 32/36 on a 75 '02. i would really appreciate. thanks

[TJs692002]

Once you remove all your smog crap, you only have one vacuum line running from the vacuum advance off the distributor going to the big fat vacuum nipple sticking out the base of the 32/36 Weber.

Now if you have a mechanical advance dizzy, just plug all the vacuum nipples in the carb and motor on!!