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Author
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Topic: 2V vs. 4V gas mileage
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hardhat
Journeyman Posts: 69
From: summerland, ca
Registered: Feb 2004
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posted 03-09-2005 03:48 PM
 
I heard you might get better gas mileage out of a new Edelbrock 4V (assuming w/ secondaries) than the original 2V that came stock with the car in 73'. My original 2V operates great and puts me at about 18 mpg driving conservatively. Any opinions? Herb
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SkinnyMan
Gearhead Posts: 916
From: Tupelo, MS - USA (CA temporarily)
Registered: Jan 2005
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posted 03-09-2005 04:42 PM
quote:
Originally posted by hardhat:
I heard you might get better gas mileage out of a new Edelbrock 4V (assuming w/ secondaries) than the original 2V that came stock with the car in 73'. My original 2V operates great and puts me at about 18 mpg driving conservatively. Any opinions? Herb
The ever present variable is the right foot. With the 2V you got no more than 2V's worth of carburetor. With a 4V there is always 2 more V's to push your foot into - but HEY, that's what they are there for.
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SkinnyMan
Tupelo, MS Thank you, Thank you very much!
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Fastback68
Gearhead Posts: 4511
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 03-09-2005 07:34 PM
The conventional wisdom is that a 2V is more economical. However, it's also said that a 4V, if tuned correctly, is more economical. I believe a poorly tuned 4V with a heavy foot is a bad combination.
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 03-09-2005 07:36 PM
Forget gas milage, with the 4v, you are gonna have that LEAD foot syndrome.  ------------------
William
68 Coupe
"Restomod in Progress"
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mike70351w
Gearhead Posts: 120
From: Delaware
Registered: Dec 2004
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posted 03-09-2005 11:08 PM
I did that test back in the early 90's while stationed in Sacramento. My test mule was motorcraft 2100 & 600VS. 70 fastback, stock 302 with RV cam, 3.00 gear. I had to make the trip several time in a 6 month period so I made about 3 test. My goal was always to see which carb could get me to the base I'm headed to without a fulling up. Driving the same I filled up at the same place both way with different carb. I ended up tossing the 2100 afterward. (the HP loss not worth it)
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64coupe
Gearhead Posts: 173
From: Bristol, PA
Registered: Sep 2002
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posted 03-10-2005 12:00 AM
i have a 750 dp and i get great gas mileage drivin on trips around town isn't so great.
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kinger44
Gearhead Posts: 376
From: Waterloo, Ontario, Canada
Registered: Sep 2004
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posted 03-10-2005 12:15 AM
Sorry, but these are vintage Mustangs - muscle cars. Why are we talking about gas mileage? If we want good mileage, we would buy a Prius!Gregg
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white68stang
Journeyman Posts: 92
From: Kansas City, Missouri
Registered: Jul 2004
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posted 03-10-2005 01:29 AM
I drive my 68 everyday. I'm not interested in 1/4 mile times. I like having a car that is a little peppy when you step on it, but is also decent on the gas mileage. Please keep the gas mileage talk coming, there is more to Mustangs than quarter mile times.  ------------------
1968 Fastback, 302, 5 speed, ez wiring harness.
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Fastymz
Moderator Posts: 22791
From: Reno Nv M&M #1240
Registered: Apr 2001
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posted 03-10-2005 01:40 AM
I think 18 mpg is darn good already.
I don't see why a small 4 barrel wouldn't get the same gas milage and allow for alittle extra power when wanted. ------------------
oddly obsessed with big scoops on little Mustangs 65 coupe 351w C4 Big Boss 429 hood scoop,8" 3.40 TracLoc. My Pics
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SteveLaRiviere
Administrator Posts: 48752
From: Saco, Maine
Registered: May 99
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posted 03-10-2005 08:58 AM
The beauty of Mustangs are that they can be all things to all people. While losing your license street racing a civic can be fun, so can getting 20 mpg cruising. Remember, gas mileage is a form of performance too. While I'm a strict Ford fan, I have to say my hat is off to GM for engineering a 400 hp Corvette that gets 26 mpg. ------------------
'70 Mustang Mach 1 351C 4V/FMX/3.25 Open
'70 Mustang Convertible 250 I6/3 speed/2.79 Open
'72 Mustang Sprint Hardtop 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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SteveLaRiviere
Administrator Posts: 48752
From: Saco, Maine
Registered: May 99
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posted 03-10-2005 09:07 AM
18 mpg is real good, and I don't think you'd improve it with a 4V. While you would spend most of your time on the primaries, which would be smaller that the throats of a 2V, all that would go out the window once you activated the secondaries, and if you are like me that would be often. For most people, if there's power there, they'll use it.One thing you could do for gas mileage is install a vacuum gauge on your dash and try to drive while keeping it as high as possible. ------------------
'70 Mustang Mach 1 351C 4V/FMX/3.25 Open
'70 Mustang Convertible 250 I6/3 speed/2.79 Open
'72 Mustang Sprint Hardtop 351C 4V/FMX/4.30 Trac Loc
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 03-10-2005 12:23 PM
My 68 gets about 22mpg (premium 93oct) when cruising. Timing is set around 12 degUsed to have a 2 barrel carb but it wasnt really any better. The carb is an edelbrock 600 (vacuum sec) and it takes a lot of revs to really open the secondarys properly because its a mild 289. the carb is a little big for the engine but thats what keeps the secondarys closed... Ive set it up with leanish jets when im cruising, and runs richer when I get on it - the needles are controlled by vacuum so you can tune it to get the best of both worlds. Only richens when you need it! Another thing to consider is trip length - it takes a while to get my car warmed up and during that time with the choke etc... the mileage is bad - probably low teens. if you are making short trips you might benefit from trying to get the engine to warm up faster and adjusting the choke to suit. Of course I have a 2.79 rear end ratio which is the best for gas mileage. But I have a C4 auto tranny which is bad for gas mileage. Manual transmissions will do better, so the best would be a T5 with an overdrive (its also lighter which will help your city mpg). The autos generally dont have a lockup torque convertor which loses you a couple of MPG compared to a manual transmission. I have a 160 T-stat which is bad for gas mileage, with a 190 T-stat youd get better cruising mileage. remember all the other tricks. Keep your windows up, tires inflated properly blah blah. Power steering, engine driven fans, A/C pumps all those accesories hurt gas mileage just as much as they hurt performance. I have no accesories (except alternator) and an electric fan.
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'68 coupe, '66 289 C code
engine, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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Twirly Bird
Gearhead Posts: 226
From: Central PA
Registered: Aug 2004
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posted 03-10-2005 01:51 PM
I have seen this to be true before in CERTAIN conditions. A friend's father switched his 2V to a 4V on a highway driven car (limited acceleration with constant velocity). The primaries on the 4V pumped less gas than the 2V carb. He drove in a manner that prevented the secondaries from kicking in. Gearing and speed make a huge difference! He claimed somewhat improved mileage. IMHO, the cost savings wouldn't pay for the carb and intake. I agree with everyone else - for me the temptation would be irresistible 
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BornInAFord
Gearhead Posts: 610
From: Bend, OR, USA
Registered: Dec 2002
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posted 03-11-2005 12:15 AM
The Mustang 2100 tops out at perhaps 380 CFM of flow. The 4100 (1.08 venturi) has 480 CFM flow. But, this means that you are only using 240 CFM (at most) per pair of venturis (compare with the 2BBL carb). Thus, you are actually increasing the velocity through the carb and injesting less air with the 4BBL at partial throttle, being more efficient in the process. But, as mentioned, the other 2 barrels are hard to stay out of.
Daniel
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 03-11-2005 09:16 AM
 Why does the 190 t-stat get better mileage than the 160???------------------
William
68 Coupe
"Restomod in Progress"
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68 S-code GT
Gearhead Posts: 3835
From: Sayreville, NJ, US
Registered: Mar 2000
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posted 03-11-2005 09:24 AM
quote:
Originally posted by indyphil:
My 68 gets about 22mpg (premium 93oct) when cruising. Timing is set around 12 deg
WOW thats great! I had a 67 with a tired stock 351W 2V along with a 2.79 rear and the worst I ever got was 16 MPG(I used to beat the piss out of that car!). Always wanted to put a 4V on there but there is that ugly lead foot thing that takes many people over. ------------------
Ed S. 68 S-code FB GT 4spd(now C6)/3.25 PS PDB
68 J-code(now 289) Cp Sprint"B" C4/3L00-9" PDB PS AC Bla-Bla-Bla
99 F150 XLT Ext/cab, 4X4, 5.4L, 3L55 [This message has been edited by 68 S-code GT (edited 03-11-2005).]
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 03-11-2005 10:37 AM
The 190 T-stat gets better mileage because the fuel evaporates and mixes better - you also get lower HC emissions. It will make less max power because you wont be able to inhale as much air/fuel mixture at wide open throttle - but good gas mileage is not about wide open throttle power its about good efficiency at part throttle. Sometimes the things that boost peak power also help to boost part load efficiency , but often making maximum power will hurt part load efficiency (like a big cam) I heard it only takes about 15-20hp for cars to cruise at 60mph. ------------------
'68 coupe, '66 289 C code
engine, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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74merc
Gearhead Posts: 1322
From: Demopolis AL
Registered: Jun 99
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posted 03-13-2005 01:07 AM
quote:
Originally posted by Twirly Bird:
I have seen this to be true before in CERTAIN conditions. A friend's father switched his 2V to a 4V on a highway driven car (limited acceleration with constant velocity). The primaries on the 4V pumped less gas than the 2V carb. He drove in a manner that prevented the secondaries from kicking in. Gearing and speed make a huge difference! He claimed somewhat improved mileage. IMHO, the cost savings wouldn't pay for the carb and intake. I agree with everyone else - for me the temptation would be irresistible
My factory 2100 vs Holley 600, same city milage, 12-16 mpg, highway went from 16 to 19 when changing to the Holley.4100 does better on the highway than the 2100. The intake probably has more than a little to do with it.
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74merc
Gearhead Posts: 1322
From: Demopolis AL
Registered: Jun 99
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posted 03-13-2005 01:09 AM
quote:
Originally posted by BornInAFord:
The Mustang 2100 tops out at perhaps 380 CFM of flow. The 4100 (1.08 venturi) has 480 CFM flow. But, this means that you are only using 240 CFM (at most) per pair of venturis (compare with the 2BBL carb). Thus, you are actually increasing the velocity through the carb and injesting less air with the 4BBL at partial throttle, being more efficient in the process. But, as mentioned, the other 2 barrels are hard to stay out of.
Daniel
For the record, I used my 2100 shaft and butterflies to replace the seized ones in my 4100. I don't think the CFM is that different. I will double check to verify 1.08.
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PTB's 67
Journeyman Posts: 4
From: Nebraska, USA
Registered: Feb 2005
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posted 03-20-2005 10:14 PM
A year or 2 after I rebuilt my 67's 289, I was able to get a stock 4bbl manifold and Autolite carb from a 68 302 Mustang. With the original 2bbl I had been getting 19mpg on the interstate. After swapping the carb and manifold, no other changes, I was getting 22-24mpg. That was with a 3.00 rear end and 3sp manual. The Autolite was a spreadbore design and the primaries were much smaller diameter than the 2bbl bores. With the current Holley 600 I have no idea what kind of hiway milage I get since I don't do any long distance driving in the Mustang anymore. Also that 24mpg was back when the limit was 55mph, so it probably would be less at todays speeds. The worst milage I ever saw out of my Mustang was shortly after I first rebuilt the engine back in 1978-9. It still had the C4 in it. My 2bbl was messed up and needed to be rebuilt. My neighbor let me borrow the 2bbl off of his stock car. An annular discharge Holley 650 2bbl (if I remember correctly). With that new rebuild and larger carb I just couldn't keep my foot out of it. 7mpg around town but boy did it ever feel fast. ------------------
'67 Coupe
289 .040 over
Badger pistons 11:1
Mellings Cam
288 dur .460 lift
Holley 1850 600cfm
68 302 4bbl manifold
3sp manual
Heddman Headers [This message has been edited by PTB's 67 (edited 03-20-2005).]
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hardhat
Journeyman Posts: 69
From: summerland, ca
Registered: Feb 2004
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posted 03-20-2005 10:33 PM
Thank you all for the replies. It wasn't going to take much to convince me to make the switch. For along time I've been bent on keeping the car stock. However, with the rising gas prices ($3 this summer!!) and the positive replies, the upgrade can now be justified!------------------
73' conv. 351C 2v mild cam, exhaust, fmx
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SkinnyMan
Gearhead Posts: 916
From: Tupelo, MS - USA (CA temporarily)
Registered: Jan 2005
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posted 03-21-2005 12:16 AM
quote:
Originally posted by PTB's 67:
Also that 24mpg was back when the limit was 55mph, so it probably would be less at todays speeds.
Your gas mileage may be better, worse or the same with the higher speed limits. I believe it has to do with where you hit your peak torque and horsepower. I would think if you are lugging it or torque is on the back side of the curve, your mileage would suffer. But if you are right in the sweet spot of the torque, while cruising down the interstate, then your mileage would be as good as if not better than before. My brother had bought a VW bus and was letting me drive it in Wyoming. He said that if I kept the speed at 65, I would only have to down shift on the hills. I called him later and told him that I found out if you ran it 75 you didn't have to down shift at all.
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SkinnyMan
Tupelo, MS Thank you, Thank you very much!
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hardhat
Journeyman Posts: 69
From: summerland, ca
Registered: Feb 2004
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posted 03-21-2005 01:57 AM
75? That's pretty good!
My bus max's at 65....
Sombody on another thread said it only takes 25(?) h.p. to do 60 mph. I thought that sounded about right!
- H------------------
73' conv. 351C 2v mild cam, exhaust, fmx
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Toronado3800
Gearhead Posts: 1163
From: St. Louis, MO
Registered: Jul 2001
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posted 03-21-2005 12:03 PM
I've read and think I've confirmed, that new cars get their best highway mileage at the lowest speed they can maintain overdrive. For my Toronado that's right under 60 mph. Too close to 50 and 1500 RPMS, and the converter wants to always unlock or worst the tranny will downshift.Of course its a multi point injected car so I don't have to deal with the secondaries opening up and dumping gobs of fuel. My 68 has a Performer 750 and seems happiest right above 60 at about 2500 RPM. By that time the C4 has been in 3rd forever and NEVER down shifts. Maybe later this week I'll run it to work and see what the lowest speed it will stay in drive is and if my economy is better. I'm thinking I'll see no economy improvement because my converter stalls around 2,000.
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