uhh...not so decent mileage

[Anonymous]

i have been doing quite a bit of highway driving and am really noticing my gas getting SUCKED way back...i can use almost half a tank of gas bombing it for about 90-100 km at varying speeds from 120 km/h to 160ish km/h....i know that much varience in speed at that high of speeds is going to suck back the gas...but thats rediculous...even a sorta constan speed of 120-130 will use up almost 1/4 tank of gas in that distance....not tooo bad, but not great...i get awesome mileage in the city though, depending how i drive as well, i find it better on gas if i dive it more gas and then release the gas than if i slowly accelerate...its like theres a spot around 1/4 way down on the pedal which really sucks the gas...but here is what i have done to the car. it could possibly be a power at the expence of mileage but who knows...maybe i still need to fine tune

I bored out the carb, enlarged the jet to almost twice the size of stock and tightened the accelerater pump screw for a quicker shot, its a carter YFA 1bbl. i played with it quite a bit and its set up really good right now. I have a bonnet on it from a taurus and have a ram air setup (filtered with sock) and i have no manifold vacuum hooked up to my vacuum advance, and no EGR or any emissions stuff. otherwise its pretty much stock. is there anything i can do for slightly better mileage? timing is setup about 2 deg. before pinging, othere than that i have no idea where its at, probably 15 deg more that stock

this is all in a big 4 door 3500+ beast and i raced a 4.3 litre vortec S10 and beat it (not the extreme S10 cause it can do like 15 secs) so am i looking at power at expense of economy or just a really bad setup?

 

[Anonymous]

You moved well beyond me in this thread where you were talking about PCV jars and hydrogen
http://fordsix.com/forum/viewtopic.php? ... ght=milage

What I picked up here is that you should run vacuum advance, inflate tires to their max, and drive like you have a raw egg under your foot. Unfortunately I can only get two out of three

leadfoot :roll:

 

[Lazy JW]

I bored out the carb, enlarged the jet to almost twice the size of stock and tightened the accelerater pump screw for a quicker shot, its a carter YFA 1bbl.

I believe that you have pretty well diagnosed the problem right there. When you bore out a round hole to double the diameter it QUADRUPLES the capacity of said hole. Of course the YF has the metering rod in the jet so it won't be quite that large of an increase, but you are truly putting a LOT more fuel through there than before. Also, the vacuum advance will help the part throttle economy somewhat. Don't leave home without it.
Joe

 

[CZLN6]

Howdy Dave and All:

As Joe and Leadfoot say, add the Vacuum advance function back to the distributor, and back off the accelerator pump to only meet the need to cover an acceleration transition and no more. Anything more will be a waste of gas. Set the way it is, every time your foot wiggles on the gas pedal you're squirting a small amount of raw gas down the manifold.

Joe also hit on the increase in area when you bored out the venturi, but you're guessing at jet size. I'd try reducing the main jet until the engine surges at a steady cruise speed of say 40 MPH, then go up one size. This will lean the engine Air/fuel ratio, giving you better mileage and even more power. A larger main jet than you can use does not make more power. It just wastes gas.

Also make sure your choke is functioning properly and not staying on any longer than necessary. Make sure you idle speed is set as low as possible.

Finally, I'd invest in a good timing light and vacuum guage if I were you. If you don't know where you started from, how will you know when you got where you were going? Accurate measurements and before and after assessments are very important to progress.

Adios, David

 

[Anonymous]

You moved well beyond me in this thread where you were talking about PCV jars and hydrogen
http://fordsix.com/forum/viewtopic.php? ... ght=milage

What I picked up here is that you should run vacuum advance, inflate tires to their max, and drive like you have a raw egg under your foot. Unfortunately I can only get two out of three

leadfoot :roll:

Actually, when i had the stock carb and everything was working right i could get 25-30 MPG approx, only used about 2 tanks o gas and then for some reason the hydrogen fuse keeps blowing (wiring is fine i thing i just gotta replace the electrodes or something....i hope) i gotta redo something, but its more of a neussance right now, and only works realy when your under a fuller manifold vacuum than i hardly am ever at now...hehe also a leadfoot

thanks alot for your help, i will hook up manifold vacuum again , i think i had disconnected it before because of a hesitation problem that was actually linked to the old carb but ran better without the vac advance hooked up, but i will certainly hook it up now. I gotta make jets bigger by grinding them since i cant buy those anymore, but i will look for a few carbs that i can pull jets out of and make a few. It would be sweet if it made even more power. Well..i will play with the accelerator pump once again :roll: i was hoping i was done with that. About the choke..It doesnt even engage (dont worry i have it set up that way) i can start er up and drive it, slower than normal, till its warm. idle speed is at 700 RPM, ive gone to 400 but it feels way too low and i have stalled a couple times when cold...sounds sweet though

My freind has a timing light, but i dont know how i can tell how many degrees ive advanced, i know i back the timing till the line in the damper or whatever is steady, do u tell my the notches in the timing metal thing when the line is more frequent by one of the lines? u can see i havent even used a timing light yet :roll: but i do have a vacuum gauge, I have heard that u just tune by getting the highest manifold vacuum possible, anything else to it? thanks again guys

 

[Lazy JW]

The timing method you are referring to is to advance the timing until max vacuum is observed and then back it down one inch from the highest point. It is a pretty good method of setting initial timing but you need to be careful that you don't end up with it being too much at the high end. The round hole that I mentioned was the jet size. It's amazing that it even runs at all with double the diameter. Just curious, how do you enlarge the jets by grinding? I have never seen grinding stones small enough to fit inside the main jet on my YF. Usually jets are sized in increments of a few thousandths of an inch.
Joe

 

[Anonymous]

the bore isnt double the size (dont know where that came from unless u were reading the part that is actually about enlarging the JET twice the size of stock) its only about 130-140% larger than stock...still a lot more though than stock. But the reason i can grind the jet to make it larger is cause the hole in the back area is larger and it gets smaller with a curved taper, so grinding the thinner part higher up makes the jet size go up...and u can definitely see the size difference on either end of the jet (stock)..

 

[Lazy JW]

Indeed I was refering to the jet size being double the original diameter. I still think that is WAY too big.
Joe

 

[Anonymous]

right...sorry for the misunderstanding....all i can fint at pick-a-part are TBIs and EFI's...and a newer version of carb on mustangs...all the other carbs are gone...i may have to go elsewhere...oh well.

 

[Anonymous]

About that bored carb - boring more than 10% usually destroys the transfer characteristics in the region of 1/8 to 1/3 throttle, which is where you got that "bog" you mention....

Unfortunately, opening the venturi throat like that also rapidly destroys the mix efficiency at lower engine speeds. Boring is usually reserved for WOT applications, like land speed records or drag racing. Good for MPH, bad for MPG.

For a +40% bored carb, the jetting should be about +15%, no more. The increased air volume does not increase the vacuum over the jet, because the throat is bigger, so you should just try to balance the missing difference.

 

[Anonymous]

did i mention a bog? Not right now there isnt...only when its cold, due to the ram air setup...and i HAD a bog before i played with jets or accelerator pump...now i dont have any bog...just a real nasty rich gas smell...lol...WOW...I am WAYYYYYY overjetted, thanks for the % equation...that will help me with my next jetting...although once i get this carb tuned up and running its best then i will probably buy another stock carb, just for the gas mileage part of it since i may possibly get a job )just got interviewed and he has one more guy to interview)...but driving there and back sucks half a tank of gas (little less with efficient driving and wayyy more with lead foot)..so i wont be keeping this carb for too long if i keep the job...although i may get a few extra bucks for this job to get a new car so i can really rip my six apart.

 

[rickwrench]

About that bored carb - boring more than 10% usually destroys the transfer characteristics in the region of 1/8 to 1/3 throttle, which is where you got that "bog" you mention....

Unfortunately, opening the venturi throat like that also rapidly destroys the mix efficiency at lower engine speeds. Boring is usually reserved for WOT applications, like land speed records or drag racing. Good for MPH, bad for MPG.

This is true on engine carb combinations that are well matched to each other. But the stock YF carbs on the 250 are ridiculously small. Maximum economy being the target. Routinely, the heads are modified to accept 1, 2, or 3, carb(s) with 100-200% more total airflow than stock.
You will lose some velocity in the larger single venturi, but even a maximum boring out a YF within the limits of the casting will still not be enough carb for a 250.

As for mileage, the point of boring the carb is to allow the engine to suck more air/FUEL mixture into each cylinder for more power. MPG will go down.
If you are running fine when the engine is cold with no choke you are running rich. What color are the plugs?
rick(wrench)

 

[Anonymous]

actually the plugs dont look half bad...normal brownish color and a slight bit o black around the ceramic (or whatever it is) from being rich or leaking oil or whatever...but its not as bad as i would have expected.

If you are running fine when the engine is cold with no choke you are running rich

It ran great without the choke when i had my stock raised air filter with a closed back, but now with the ram air setup it will misfire and almost die if i try to accelerate too fast, when its warm its a charm. is it still to rich?

would i get any better mileage using 2 stock carbs or would it be about the same, or is it hard to say?

 

[kirkallen143]

Read "Horsing around with the Mustang Six". by Ak Miller. He suggested and tried a YF1 from a 240 (1973-1974) and said did not have to re-jet only adjust slightly to get the best out of performance and economy for the 200 L6. Made a good even swap.

Kirk ' 73 bronco

 

[kirkallen143]

Here's the link, read it you will enjoy it:

www.cometcentral.com/tech/hm6/index.html

Kirk ' 73 (bronco)

 

[rickwrench]

It ran great without the choke when i had my stock raised air filter with a closed back, but now with the ram air setup it will misfire and almost die if i try to accelerate too fast, when its warm its a charm. is it still to rich?

It was probably rich before, but now it sounds like it's where it should be, and you need a choke .
Rick(wrench)

 

[Anonymous]

rick, what kinda milage do you get on those flip-flops?

stock or modified?

flames?

 

[Anonymous]

Read "Horsing around with the Mustang Six". by Ak Miller. He suggested and tried a YF1 from a 240 (1973-1974) and said did not have to re-jet only adjust slightly to get the best out of performance and economy for the 200 L6. Made a good even swap.

Kirk ' 73 bronco

I priced a YF1 at Lordco for about 150 bucks...i know a freind who works there so he can get it for 20% more than the store pays which usually works to around half price...But i have a 250...is the YF1 higher CFM than the YFA?

 

[rickwrench]

rick, what kinda milage do you get on those flip-flops?

stock or modified?

flames?

Nah, they are bone stock, the generic payless drug store variety. Good mileage, top speed isn't so great, though. I'll be giving them a complete durability workout in about two weeks. A couple weeks of tropical island beach sand is the best test. And, truth be told, I haven't jumped on the skate in about... well, dammit, I've just got a lot more sense now! Looks good on the garage wall though.
Did you get that fan?
Rick(wrench)

 

[Anonymous]

actually no...not yet. Miami mail stinks

I sent my mom a package 2 day USPS....5 days later....

so I will track it tomorrow...

chaz