454 TBI mpg

Chipper Chapman · 11-28-2016, 07:14 PM

Looking at a 32' Winnebago for a decent price locally, it has a 454 TBI and 4L80E. I tow a 24' enclosed weighing about 8-8500 pounds. What rough MPG would I expect. My last one was 454 carb/th400 and I got 6 on good days. Looking for something a little more fuel friendly. Thanks

Alan Roehrich · 12-03-2016, 04:18 PM

The TBI engine is no better than the carbureted engine for fuel efficiency or performance, and in fact is often worse. The TBI engine is in fact the exact same engine as the old carbureted engine, except that in most cases it has an adapter and a 650 cfm fuel injection throttle body instead of a 750 cfm Q-Jet.

The Vortec engines are light years ahead.

james schaechter · 12-04-2016, 08:51 AM

Quote:

Originally Posted by Alan Roehrich

The TBI engine is no better than the carbureted engine for fuel efficiency or performance, and in fact is often worse. The TBI engine is in fact the exact same engine as the old carbureted engine, except that in most cases it has an adapter and a 650 cfm fuel injection throttle body instead of a 750 cfm Q-Jet.

The Vortec engines are light years ahead.

At some point physics come in to play. When you are powering a boxcar hooked to another boxcar that is very heavy, it just takes fuel to move it! We have had all types of tow vehicles. Our gasser with 454 with 4LE80 was 6-8 Mpg. Our current diesel pusher 8.3 cummins is generally 7.5mpg . We pull a 24 ft trailer. The difference for us was that the diesel pusher is quieter, more stable and it stops waaaay better than the gasser. I doubt if you will save a lot on fuel with a TBI.

Alan Roehrich · 12-04-2016, 10:52 AM

James is correct.

However, efficiency in the engine itself makes a considerable difference.

The problem for TBI is that fuel injection, even electronic fuel injection, by itself, makes little difference in efficiency. Put that on top of the old 1973 design truck 454, and you get next to nothing, on a good day.

The advantages of the Vortec system are considerably higher compression, better cylinder head flow, better intake manifold flow, and even a moderate improvement in camshaft design.

Even then, the Vortec left plenty on the table. The cam profile still isn't enough, they moved to non adjustable rockers, the exhaust system is a product of design by cost, not efficiency, and the computer tune is mediocre at best.

ss3011 · 12-28-2016, 02:28 PM

I have a 1996 , 27 foot Southwind Storm with a TBI 454 pulling a 24 foot Wells Fargo enclosed trailer . There are two things that makes big difference in my fuel economy , the speed I go , and whether I use the cruise control . Best mileage I ever got was 9 mpg , that was going about 55 mph and not on cruise . Normally on the highway I can get 7 mpg , but that is never going over 65 mph , and driving it off the cruise control , trying hard to stay in 4th gear . My motorhome will almost run non-stop in 3rd gear if I run the cruise . If I drive , I can run in 4th gear most of the time , only rarely going into 3rd gear on long grades . That makes a big difference , and just lets the engine loaf along at under 2500 rpm .

11-28-2016, 07:14 PM	#1
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 473 Likes: 246 Liked 166 Times in 71 Posts	454 TBI mpg Looking at a 32' Winnebago for a decent price locally, it has a 454 TBI and 4L80E. I tow a 24' enclosed weighing about 8-8500 pounds. What rough MPG would I expect. My last one was 454 carb/th400 and I got 6 on good days. Looking for something a little more fuel friendly. Thanks __________________ Chris Chapman 1969 Chevelle NHRA F-G/SA 1090

12-03-2016, 04:18 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,095 Likes: 1,541 Liked 1,769 Times in 402 Posts	Re: 454 TBI mpg The TBI engine is no better than the carbureted engine for fuel efficiency or performance, and in fact is often worse. The TBI engine is in fact the exact same engine as the old carbureted engine, except that in most cases it has an adapter and a 650 cfm fuel injection throttle body instead of a 750 cfm Q-Jet. The Vortec engines are light years ahead. __________________ Alan Roehrich 212A G/S

12-04-2016, 10:52 AM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,095 Likes: 1,541 Liked 1,769 Times in 402 Posts	Re: 454 TBI mpg James is correct. However, efficiency in the engine itself makes a considerable difference. The problem for TBI is that fuel injection, even electronic fuel injection, by itself, makes little difference in efficiency. Put that on top of the old 1973 design truck 454, and you get next to nothing, on a good day. The advantages of the Vortec system are considerably higher compression, better cylinder head flow, better intake manifold flow, and even a moderate improvement in camshaft design. Even then, the Vortec left plenty on the table. The cam profile still isn't enough, they moved to non adjustable rockers, the exhaust system is a product of design by cost, not efficiency, and the computer tune is mediocre at best. __________________ Alan Roehrich 212A G/S

12-28-2016, 02:28 PM	#5
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	Re: 454 TBI mpg I have a 1996 , 27 foot Southwind Storm with a TBI 454 pulling a 24 foot Wells Fargo enclosed trailer . There are two things that makes big difference in my fuel economy , the speed I go , and whether I use the cruise control . Best mileage I ever got was 9 mpg , that was going about 55 mph and not on cruise . Normally on the highway I can get 7 mpg , but that is never going over 65 mph , and driving it off the cruise control , trying hard to stay in 4th gear . My motorhome will almost run non-stop in 3rd gear if I run the cruise . If I drive , I can run in 4th gear most of the time , only rarely going into 3rd gear on long grades . That makes a big difference , and just lets the engine loaf along at under 2500 rpm .