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drivetrain build for 20 mpg

  
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drivetrain build for 20 mpg

 
slip60 slip60
New User | Posts: 1 | Joined: 04/12
Posted: 04/07/12
02:19 PM

Anyone have suggestions on a drive train to produce 300hp,on regular gas and get 20+ MPG...would like to do a Res to mod with good gas mileage for everyday use..thanks  

452RBchevy_c10 452RBchevy_c10
User | Posts: 138 | Joined: 01/09
Posted: 04/08/12
08:24 PM

First of all this gas sucks today, no energy in it. Why not do a 4.8LS V8? Parts gallore for it and probably low cost now since its kind of popular and its a Chevy. What about a 302 Chevy or Ford? 273 Mopar? 231 Buick V6 How bout a 300hp 3.4 60 degree Chevy V6? Here's one for ya, try to spin the snot out of a 3.0L Buick V6 from a FWD Century or Cutlass Ciera to get 300hp.

You can get 300+hp from a dirt cheap 305 Chevy too. Give that a shot. Just some ideas throwing out there.  

452RBchevy_c10 452RBchevy_c10
User | Posts: 138 | Joined: 01/09
Posted: 04/08/12
08:30 PM

Spin the snot out of a 3.0L Buick V6 from a Century or a Cutlass Ciera that is all built up.

Why not a 305 Chevy? You can get 300+hp from it. You can find them dirt cheap and they got small diameter bores for this junk gas sold to us dumb citizens that take whatever our egg head know it all politicians force on us.  

cameronasi cameronasi
New User | Posts: 13 | Joined: 08/12
Posted: 08/22/12
05:34 AM

Wow a 4.8LS will cost on fuel right?  

TheSilverBuick TheSilverBuick
Guru | Posts: 1220 | Joined: 02/06
Posted: 08/22/12
08:45 AM

Pfft, I've gotten 19.5mpg with 400HP with a Buick 455, and I'm currently at 17.5mpg with the 450HP combination that the tune hasn't been optimized so might squeak up some.  I've got plans for some head work and a new cam that I'm expecting around 500HP and well over 20mpg.  Pulling a ton of duration out of the cam (the proverbial over cammed)but bumping the lift significantly (now have valve relieved pistons I didn't have when I got my current cam), and then significantly improving cylinder head flow.  I also used to run a low compression 455 that made in the neighborhood of 320HP and regularly got 23mpg highway. All runs on 87 octane. Just need a decent overdrive gear and run 3.50 or less rear end ratio's.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. '69 Firebird replaced!

http://www.bangshift.com/forum/index.php?topic=6189.0

waynep71222 waynep71222
User | Posts: 155 | Joined: 04/12
Posted: 08/22/12
09:25 AM

a few thoughts that might prove to be wrong..

but  here we go anyway..

high intake manifold vacuum means there is actually LESS volume of air passing through the engine .  

less air volume means less fuel mass to reach the same air fuel ratio..


less air and fuel also equate to less horsepower..  but how much horse power does it really take to push your car down the highway at legal speeds..

there were some japanese cars that used a double bladed throttle body.. with a small primary and a large secondary that actually fed different sections of the intake manifold.. but with an air flow meter..  the total fuel needs were calculated to spray the proper amount of fuel into the intake port..

think about this..

diesel engines.. without turbo or superchargers have atmospheric pressure in the intake... so each stroke has the a full volume of air..  at say 14.7 pounds per square inch above a perfect vacuum..   14.7 is standard air pressure at sea level...

if you have a motor with 15 inches of manifold vacuum.. 15 inches of vacuum is about half of 29.9 inches .. so you have half the volume.. so only half the fuel is needed...

its very hard to find a cam selection engine combo that creates more than about 18 inches of vacuum.. but i have not been looking for them..   i did build up a 396 that idled in drive with 18 inches of vacuum..  it was on a 67 ss396 chevelle.. i had a terrible time with it. as that model actually dumped the air injection air into the base of the carb while closed throttle high vacuum readings.. think taking your foot off the gas coming off the freeway.. this thing would open the dump valve and flood the intake with air injection air...    i used an H230 grind from american custom cams in covina ca.  but that was a long time ago... i use that H230 grind in other engines.. took out an H131 RV cam and put in an H230.. went from 11 MPG to 17MPG with just a cam change in a loaded ford van with a 351W.. same effect but i never got the MPG on a dodge van with a 360.. got 100 miles farther per tank..  on trips between la and salt lake city.. so there is something magic about that grind..

installing oxygen sensors and a air fuel ratio display..  narrow band works great so you don't have to spend a ton of cash..   if you have it.. wide bad is far more accurate..  

an manifold vacuum gauge..

i am thinking about rigging up a twin gauge mount.. with a air fuel ratio gauge..and a vacuum gauge on a magnetic mount..  put a cigar lighter plug on the air fuel ratio gauge.. so i only need one wire to the oxygen sensor and a vacuum hose..  makes it easily removable  between tuning sessions if you don't want a cluttered look for daily driving..

my thoughts are that with OBD2 systems.. a lot of the extra fuel is being used to keep the cats at operating temp... don't believe me.. just unplug the secondary sensors.. and take it for a drive..   when somebody comes up with a heated grid.. inducting heating coils to heat an internal grid.. so the excess fuel needed to maintain combustion inside the cats is not needed to maintain internal temps for proper operation..  then the fuel economy will increase again..

the 305 chevy is a great idea...  even building a stroker with a 305 bore might be interesting..
as the 305 bore keeps the expanding flame front in a smaller space..  the long stroke creates more torque as there is more distance and angular leverage for the expanding gasses to push the piston down with..  this takes a LOT more engineering skills than i have..


one thing.. building manifold vacuum requires proper valve guide clearance.. so the valve is not floating around on the valve seats... i have taken to using stay lube moly graphite assembly lube on the valve stems.. in the guides and some under the ring retained seal.. this lubes the guides for a long time.. so they don't wear and don't seize..  how long is motor oil going to last as that is what most are lubed with when assembled..

if you are running a carb.. you will want to pay close attention to the idle mixture adjustment.. and the idle transition tuning..  as at 10 to 30 mph.. at a steady speed.. you are running a lot on idle transition along with a portion of the main circuits...  read up on idle transition circuits..

i just found out a few weeks ago. that the summit brand carbs that were the holley 4010/4011 have a kit from summit to fine tune the idle transition circuits ..  real weber carbs also have easily tuned idle transition circuits..  one can get weber jetted metering blocks to fit conventional 4150./4160 design carbs also..

wheel alignment.  tire pressure.. tire internal design can also seriously effect fuel economy.  can you push your car on level ground with ONE HAND...  and have it continue to roll.   did you know that tire design effects MPG that putting the wrong tires even through they are the same size on a prius can effect fuel economy by 5 mpg..   i worked on some caravan rear brakes just the other day.. the rear wheel bearing assemblies had so much break away torque needed .. i thought they were bad.. until i got the replacements.. and they were exactly the same..

if it as easy.. full sized SUVs would be getting 40 mpg..

don't forget... that early to mid 80s.. 305 chevy's with feed back carbs in a full sized caprice could knock down 26 mpg.. the 350 versions could do 23MPG highway..   the V6's with feed back carbs in G bodies i have heard of 26MPG with the feed back system.

review the second or third race from the end of the sprint cup nascar 2011 season.. it was won on MPG. as that driver did not back off all the way on the throttle going into corners.. there were no flames coming out of his tail pipes in the corner.. he out ran everybody by going 7 to 10 laps farther at the end than other people were able to go without pit stops...  stopped the super high intake vacuum from pulling massive amounts of fuel from the idle ports and idle transition ports..

food for thought..