OT old beetle tuning question Options

[r_towle]

Hi,
1972 beetle 1600 DP with the PICT 30/31 single carb.
We went from dual weber 40 mm to the single to achieve better MPG for my son.
the dual webers averaged 20 mpg...
I am assuming that the single will get him to the high 20's....of course depends on his foot...
new motor btw, reputable builder..The heads are worked a bit to reduce the compression ratio...long motor life was his rational.
Is that an achievable goal. 25-30 mpg??

Rich

[drewvw]

as long as the carb is tuned up nicely, I don't see why not. I've gotten 20mpg out of the ghias 1600DP setup when the solex wasn't 100%.

[Tobra]

easily, depends on driving habits quite a bit though

[So.Cal.914]

Depending on how he drives he should get that or better. 72 is a OLD bug? Aaaarggg.

[r_towle]

Depending on how he drives he should get that or better. 72 is a OLD bug? Aaaarggg.

ok,
rephrase the question.

same driver, same driving habits...in my mind he should get better MPG with a single carb than with dual 40mm webers.

the plugs were golden brown, and I had gotten the dual webers tuned really nice...lots of jet changes etc...

but now, stock solex single barrel carb...it should (I would think) get better mpg...
Im thinking one jet versus 4...all that...

then the other side of my brain says...the engine will only suck so much air/fuel per stroke, no matter how it is fed (provided the fuel delivery is tuned correctly) ...so with dual 40mm webers..each barrel will provide the required amount of air/fuel for the cylinder that is sucking it in at that time...

So same driver, same habits, same right foot....will he get better mileage??
BTW 20mpg seems just way to low for a 1600 stock beetle...
Rich

[Aaron Cox]

what you lose in mileage with twin carbs, you gain in response (IMG:style_emoticons/default/smile.gif)

[type11969]

I could achieve 25mpg in my sp 1600 69 Beetle. I get around that using my 1.8L t4 in the same Beetle now . . . using dual dells. The long intake runner length doesn't help with the single carbs, fuel can fall out of suspension, especially on a cold day.

I doubt your mileage will go down by switching to that single though. But, how low is that compression ratio? That could easily be the cause of your lower mileage numbers. Lower CR = less efficiency.

[Air_Cooled_Nut]

40mm are too big for a stock engine in the first place. And that mileage is bad...probably running too rich to make up for the over-sized carbs.

[JoeSharp]

My squareback got over 40 and over 25 around town. It had 32PICT's from the factory with a little head work, a recurve on the dist, a mild cam and good exhust.
It all depends on the set-up. With your cam it may be a step backwards. You should be able to get the bug to up over 30 mpg easy.
:PERMAGRIN: Joe

[r_towle]

40mm are too big for a stock engine in the first place. And that mileage is bad...probably running too rich to make up for the over-sized carbs.

Thanx, gotta read the whole thing...
40's work, gotta get the right venturis and the right jets and voula they are alot smaller...
they did work, not to rich plugs were/are golden brown...
NOW it has a 30/31 PICT...

My squareback got over 40 and over 25 around town. It had 32PICT's from the factory with a little head work, a recurve on the dist, a mild cam and good exhust.
It all depends on the set-up. With your cam it may be a step backwards. You should be able to get the bug to up over 30 mpg easy.
:PERMAGRIN: Joe

that is what I remember from the four that I had when I was younger...
the headwork is very mild....it is a normal deal when he rebuilds them to do this (though I asked for purely stock)...but waddya gonna do...I got reamed out for complaining (on this board..cause he is a friend of someone here)
Soooo,
I am gonna take a look at the entore ignition again...maybe even pull the jet to see what it is..
I am hoping that does not require taking the carb apart, but it might...

I am shooting for 25-30 mpg...and that should be achievable with a 1600 stock motor, stock exhaust, stock carb, stock car, stock wheels and tires (little tires too, really thin)
Right now the dwell is to high,
The car hesistates at low rpm, and the valves need to be done...
So, I am hoping that once all that is done the car will get to where it should be....

Rich

[type47fan]

I have a stock 1600 in my '66 bug and have gotten 26 MPG consistently with that engine since 1976! I'm a conservative driver. . . .

Good luck,

[brer]

what distributor?

if you're using the 009 a MPG gain can be had by going back to a vacuum advance type.

[Katmanken]

Ummmmm....

I usta get 16-18 mpg with my Karmann Ghia and a single barrel solex..... (IMG:style_emoticons/default/happy11.gif)

It would lay rubber in 2 gears, and

Had a few mods to the carb. Carb had 2 speeds..... Idle and GOOOOOOOOOO!!!!!!!

Ken

[blitZ]

It's possible the right foot factor played a role. I drove my son's Celica to work no problems. He gets his license, three months later the front tires are bald and the clutch is cooked. (IMG:style_emoticons/default/huh.gif)

[Thack]

Dual 40mm seem like a lot of air even though you choked it with venturis. Since you are going to a smaller carb you will get more mpg efficiency. Yes a motor only sucks in so much air but you can dump more fuel than needed for moderate acceleration and fuel mileage. In other words, just because you can hot rod a motor doesn't mean it needs the performance gain. An airplane mech told me that burning a 1/2 pond of fuel an hour equals 1 horsepower. I'm sure you can see that the dual 40mm would deliver more fuel per hour than the PICT. Don't expect the same low end performance or the top end too.
What are you doing with the 40mm carbs?