Increasing MPG - 1994 P30 454

[dix39]

I don't know what "Super Steer Specs" are, but I agree with Rick that it's important to find someone who knows what they are doing for the job, especially if you are getting new tires. I had ours aligned 3 times in the 4 or 5 years we owned it. Poor alignment wore out a new set of front tires in about 20k miles.

I did just about everything you guys have done, but something the last alignment person did that I wasn't aware could be done was adjust the bell cranks. He snugged those up as well as the wheel bearings.

Steve

[RickNC]

Originally Posted by dix39

I don't know what "Super Steer Specs" are.....
Steve

http://supersteer.wpengine.com/wp-co...ions-10-06.pdf

[tcg]

I've got a 1996 28' Shasta with an E350. The biggest thing I do to go from 6mpg to 8mpg is set the cruise control at 60mph and watch people pass me.

Other than that I don't really try.

[AudiDudi]

You might try increasing the exhaust pipe size. I went from a 2 inch to 2 1/2 inch on an older 390 ford and increased mileage from about 7 to about 9 and had much better throttle response. On my current 7.3 diesel truck, I went from a 3 1/2 to 4 inch exhaust and increased mileage by about 1mpg.

[FFG]

Tyre wear is good considering they are between 11 and 18 years old and some haven’t been changed since it was imported into the uk in 2004. Haven’t used the cruise control yet but will now I’m getting more confident.

[EyezOpen]

Originally Posted by FFG

Getting around 6 mpg in a 25 foot Itasca Passage (1995) and want to improve this as others in the Uk are getting double this. I'd be happy with 10 so what re the most obvious things tho change/upgrade. I'm looking at Tri-y from Doug Thorley to increase torque but to help with engine and cab temps and I have a manifold gasket leak so its an obvious upgrade.
Look pretty stock as it is and I've changed a fair amount of consumable but I need to look at other options.
Its a 7.4 Chevy big block, HEI. Not really had any experience so any help much appreciated. Seems to run well but ticks under load (which I suspect is the gasket) but is quiet when cruising.
FFG

Hello i will give a opinion here, this opinion cones from yrs of building big blocks and programming tbi injection systems for boats. I am not demeaning tbi systems but there pretty much only good for cold starts...lol calm down tbi guys i meant that with love..well kinda. First start the engine pull off the air cleaner and shine a neon light down the tbi and take note of the injector spray pattern. A nice conical shape would be desired...more that probalby you will notice the pattern is scattered and actually dripping. Second as to the ect sensor that is very critical...its a choke of sorts. A cold engine simply gets a extra squirt of fuel...when she warms up the squirt is backed off a smidgen. Its called a cold enrichment circuit and when activated it increases the pulse width sent to the injector... just a smidge that is.

If those injectors are leaking switch to a carb or your opening a real can of worms.

[EyezOpen]

Originally Posted by EyezOpen

Hello i will give a opinion here, this opinion cones from yrs of building big blocks and programming tbi injection systems for boats. I am not demeaning tbi systems but there pretty much only good for cold starts...lol calm down tbi guys i meant that with love..well kinda. First start the engine pull off the air cleaner and shine a neon light down the tbi and take note of the injector spray pattern. A nice conical shape would be desired...more that probalby you will notice the pattern is scattered and actually dripping. Second as to the ect sensor that is very critical...its a choke of sorts. A cold engine simply gets a extra squirt of fuel...when she warms up the squirt is backed off a smidgen. Its called a cold enrichment circuit and when activated it increases the pulse width sent to the injector... just a smidge that is.

If those injectors are leaking switch to a carb or your opening a real can of worms.

[EyezOpen]

[leadman]

If the bell cranks are worn change to the SuperSteer bell cranks. They have tapered roller bearings in them vs brass bushing in the original ones. Pricey but well worth the money. The driver side wear out first usually.

[TwoGrizz]

I would really like to hear more from EyezOpen,
Switch to a Carb? How and what Carb?
I get 6 MPG average. 1994 32 ft. Bounder towing a small trailer.
Putting a lot of money in to 1 or 2 miles more?????

But I would like to know more about how to do it.

Thanks, Steve

[glennj3cub]

I have a 1987 HR, 33 foot with 6 wheels in the back, dual then one trailing. 454 Chevy engine. Seems I have always gotten 6 MPG, speed not changing much.
I have all new tires (2 years ago and $1800). Replaced the air back and shocks up front. That sure helped the feel.
We took a trip a couple of weeks ago, it started backfiring some, then skipping. Finally it stopped running. Got a tow in to a local shop. 5 hours later drove off with a $1000 bill. New plugs, wires and distributor. I could feel the new power instantly.
Now for what your interested in. I started off the trip with 5.5 MPG with the engine ac running. The ac compressor started screeching so we stopped using it and went with the external generator for roof top ac. I think we were getting around 6.5 MPG at that point but that was not accurate due to not having a new full tank after repairs.
Now after coming home, driving at or below 60 mph, no ac or generator running, windows open. 8.1 MPG on the road and through small towns and lots of traffic.
So the # 1 item that helped must have been new plugs, wires and possibly the new distributor! Then of course not using ac or generator and speed.
Wondering how much air pressure you have? I use 94 lbs.

[glennj3cub]

Originally Posted by FFG

Tyre wear is good considering they are between 11 and 18 years old and some haven’t been changed since it was imported into the uk in 2004. Haven’t used the cruise control yet but will now I’m getting more confident.

My tires where pretty old like yours, they started blowing out, even the spare was old. The tire store told me though they looked great (tread and no dry rot visible) that when tires get over about 10 years old they should be replaced.

[FFG]

The tyres have hardly any wear but there are faint cracks appearing so I made the decision change them all. They were 7.50 x 16 but can't get these in the load rating so going Michelin Agilis+ 225/75/16. I've got 3 but need to try them to make sure the duallys don't touch before I fully commit to that size. i change the tyres on my TVR between 5 and 7 years irrespective of use as you do notice they go hard and you lose grip.
FFG

[EyezOpen]

Originally Posted by TwoGrizz

I would really like to hear more from EyezOpen,
Switch to a Carb? How and what Carb?
I get 6 MPG average. 1994 32 ft. Bounder towing a small trailer.
Putting a lot of money in to 1 or 2 miles more?????

But I would like to know more about how to do it.

Thanks, Steve

First things first if it is not broken dont fix it, with that being said the first truth tbi is very old tech at some point it is going to wear out. By now i would find it incredible the original injectors are working or replacement injectors for that matter. There are sites that offer replacement injectors and mfgs who build them however they are off the mark time after time. The only replacement injector one can use with any confidence are those made be ac delco with the original numbers and you will find them long gone. Then you have the working parts of the tbi and they to are worn with age and use...

The 454 tbi is a stand alone unit its design is limited to 680 cfm that inhibits air flow all by itself and no amount of modding can enhance that limitation and there are a lot of modifications one can buy to enhance just that.

Im sitting here playing back the old tapes realizing i have no ideal how how your main body computer works with your engine.....i would think its quite primitive that is it does not control timing advance....Before anything is done one would have to determine how the main body computer effects the engine what happens is if its just pulled. In the marine environment its called MEFI and that is a very basic system, just pull the mefi replace the distributor...mount a carb and new linkage and your done. It maybe that simple for a RV to ive never seen the whole system..Perhaps there is a old delphi guy or gal...on this site that can illuminate this topic a bit.