A tachometer in a P-30

I had a 1990 Winnebago on a P30 chassis with a TBI 454. It was 31 feet long and weighed (purely an estimate) around 13-14K lbs.

I got 6.5-7 MPG if I ran on a cool day (ie temp below 70) or at night without the generator going. On a hot summer day (temp above 85) with the generator, I'd get closer to 6-6.5 MPG.

Edited due to being a duplicate

Daveinet wrote:
I'm almost 32 feet. Weight is 13580 fully loaded.

Gjac wrote:
I am surprised also that the newer 8.1's and V-10's don't do better than the older motors. Most seem to report 7-7.5 mpgs on on the newer MH's with 5 & 6 speed transmissions, while 8-8.5 mpg seems to be the norm for a 454 TBI with a 4 speed transmission for the same length MH. Maybe more HP uses more fuel? Weight of stuff inside more slide outs?

They are significantly more efficient, its just that they are installed in units that are much taller and about 8K lbs heavier. Most the old 454 are running in coaches that are 16K lbs on lower profile chassis. The 6 speed does not help mileage, but just optimizes engine speed for best use of available power. In high gear, the engine RPM is still nearly the same, regardless of if you have a 4 speed or a 6 speed. The difference is that when you ask for more power, it will shift sooner, so the engine is turning the optimum RPM for the needed power. You also have a lower first gear.

Interesting, mine is a 1995 33 ft 11 ft 6 in high and weighs about 15,000 fully loaded. I did not think the weight would be that much difference. 8000 lbs is a lot of weight increase, but I guess when you look at the whetted surface area increase of the newer, higher, wider mh's plus slides the weight adds up quickly and it is still HP to weight that affect performance and mpg's.

I'm almost 32 feet. Weight is 13580 fully loaded.

Gjac wrote:
I am surprised also that the newer 8.1's and V-10's don't do better than the older motors. Most seem to report 7-7.5 mpgs on on the newer MH's with 5 & 6 speed transmissions, while 8-8.5 mpg seems to be the norm for a 454 TBI with a 4 speed transmission for the same length MH. Maybe more HP uses more fuel? Weight of stuff inside more slide outs?

They are significantly more efficient, its just that they are installed in units that are much taller and about 8K lbs heavier. Most the old 454 are running in coaches that are 16K lbs on lower profile chassis. The 6 speed does not help mileage, but just optimizes engine speed for best use of available power. In high gear, the engine RPM is still nearly the same, regardless of if you have a 4 speed or a 6 speed. The difference is that when you ask for more power, it will shift sooner, so the engine is turning the optimum RPM for the needed power. You also have a lower first gear.

Daveinet wrote:
I'm surprised you need to drive so slow to get 10mpg. Back when I was running the 454 and 3 speed, I could get 10 on flat level ground traveling 65 mph. The only thing the engine had was headers. Otherwise it was bone stock.

What weight/length RV were you pulling to get 10 mpg? My Bounder is 34', and we're usually pretty lightly loaded. I'd love to get 10 mpg even at 60.

Daveinet wrote:
I'm surprised you need to drive so slow to get 10mpg. Back when I was running the 454 and 3 speed, I could get 10 on flat level ground traveling 65 mph. The only thing the engine had was headers. Otherwise it was bone stock.

I am surprised also that the newer 8.1's and V-10's don't do better than the older motors. Most seem to report 7-7.5 mpgs on on the newer MH's with 5 & 6 speed transmissions, while 8-8.5 mpg seems to be the norm for a 454 TBI with a 4 speed transmission for the same length MH. Maybe more HP uses more fuel? Weight of stuff inside more slide outs?

I'm surprised you need to drive so slow to get 10mpg. Back when I was running the 454 and 3 speed, I could get 10 on flat level ground traveling 65 mph. The only thing the engine had was headers. Otherwise it was bone stock.

BULLETLS1 wrote:
I did change the distributor, there was a sale in summit racing, 50bucks a billet one, high perf coil, nice 9mm wires ceramic spark boots, 1number leaner jets (yes, still has a carb), the injector in the "least injection hole", carb spacer (I think it was a waste of money), and definetelly north of 10mpg! Keeping @50mph
30footer.

Did you change the distributor as a preventative measure or was it giving you some sort of problem? I ask because mine has 98 k miles and is the original and have thought about just changing it because it is old.

Deano56 wrote:
wow 8 mpg, I think my carbed 1990 P 30 34' MH gets around 6 mpg but not sure

Yeah, my 87 34' Bounder is the same - you might also be restricted, as I am, by the fairly un-economical 3 speed trans. I almost never get her above 60, and I'm lucky to hit 6.5 mpg. There's not a lot we can do without spending a fair amount of money, and you really have to look at payback. If I drove mine 10K miles a year it would make a difference, but at 3-4K a year, right now I just have to live with it.

I wanted a clean look, I'll consider deleting the air vent (dash AC doesnt work anyway).