Muldoonman

[Don Fairchild]

My coach is a 95 Country coach two axle 4:56 gears with 12R22.5 tires and the HD 4060 trans. It weight's 37,000 lbs. and I pull a 2003 Chevy Silverado 3500 crew cab 4X4 that weights 7,700 lbs.
To answer your question the best I can, when I bought the coach 8 years ago it had several bad cylinder kits in it and a liner o ring leaking. When I got it home I pulled the engine and changed the kits and had the heads rebuilt, I had the injectors rebuilt and changed tips from 9-6 to 9-62 for more fuel I also had the pop pressure increased for better spray and burn in the cylinder. I checked the blower and made sure it was a 100% and it was so I changed the by pass valve from what is call a maxi to a middy valve ( the lowest opening pressure you can get) . The book calls for the injectors to be set at 1.50 but I have them at 1.475., If any one wants to change there injectors to a lower setting you need to bar the engine over by hand and make sure they don't bottom out before you start the engine. I also set the valves at .014 not .016 as the book calls for. I looked at the camshafts in the engine and found J43 cams so I had an offset key made and advanced the camshafts up 1/2 tooth this is 2.5 Deg.s I verified this with a degree wheel and dial indicator. I then changed the turbo from a TV8512 with a 1.39 hot housing to a TV8513 with a 1.23 hot housing. This combo in a this DDEC three engine gives me 525HP with 23 lbs. boost at 1800 rpm. I also have a hyd. fan drive so I am not spinning the fan all the time. I try to cruse at 1700 rpm in 6th gear most of the time, when in cal. It is 1600 in 5th that's 62 MPH in this coach.

Hope that helps

Don

[muldoonman]

Thanks Don. Sounds like you built a hot rod. After having bought my bus 3 years back, i'm still trying to figure this 2 stroke out. It's a fun learning journey for sure. Thanks again for the info.

[Don Fairchild]

I did not build it as a hot rod I built it so I could cruse it at a lower rpm to save fuel and engine life. Pushing these big box's down the road takes hp and tq so the lower rpm you can make power then match the tires and gears will go a long way to get you where you would like to be.  You prevo being a 91 I believe is a DDEC II. You can make some change's to your tune up, put a tighter hot housing on the turbo and pick up some mpg but you won't match mine with the setup you run.

Don

[muldoonman]

Looking at my Prevost build sheet, mine has 3.58 gears, 12R 22.5 tires. Likes to run about 65 at about 1750 to 1800 rpms. Pull a 2013 F150 4x4 Super Crew. Wife followed me in yesterday and said speedo was about 4 mph off. Of course all the mpg you can get is important but 4 or 5 to 7  ain't a lot of difference. We didn't buy for the mileage anyway. When I run out of money, I think I will stop and park (or get me a thief hose and find one of you boys with a full bus and a pocket full of money)

[twostick]

I don't know, 4 MPG is $1 a mile for fuel. 7 MPG is $.57 a mile based on $4 a gal fuel for easy math. Seems like a fairly substantial difference to me .

Kevin

[muldoonman]

You're right Kevin, but I ain't gonna spend $25,000 to get there (7mpg) with my 22 year old bus with an engine change from this sweet sounding 8V92TA! Any way, I only got 68,000 miles on the engine and chassis now.

[twostick]

Yes there is that . It would take 50,000 miles for the fuel savings to pay you back. If you were at major overhaul time it MIGHT make sense then. I always liked that 2 stroke snarl. Some said they wouldn't pull with a Cat or a Cummins but my response was always that they at least sounded like they were trying. 

Kevin

[luvrbus]

You can get the torque range on a 8v92 right up there with the 60 series 12.7 and the Cummins

[twostick]

When the DDEC 8v92 first came out, the clutch engagement torque was 1000 ft/lbs which was 2-300 more than a a Big Cam Cummins. They were matching peak torque numbers with the 4 strokes which at the time would have been 1400 ft/lbs IIRC but I think they needed 1400 RPM to do it vs 1200 RPM for Cat and Cummins. The only place a mechanical injected 2 stroke was lacking compared to the 4 strokes of the day was fuel consumption and maybe life to overhaul.

Kevin

[Don Fairchild]

It doesn't matter if it is a two stroke four stroke gas or diesel, if you get the parts combination matched for the air flow and fuel flow any engine will run to it potential. If properly built a two stroke will pull good torque down to about 1200 rpm, mine on the dyno shows 1000 ft. lbs. at 1200 and 1550 at 1400 - 1450 rpm. Back before the 60 and some others came out the 71TA and 92 TA ran somewhat better fuel millage than cummins and a hole lot better than cat. The fuel rate on most of the four strokes other than John Deer is somewhere around .387 gal/hp hr. John Deer is between .46 - .50 gal/hp hr. depending on HP. The naturals are around .486 gal per hp hr. The turbo two stroke engine are around .456 gal/hp hr. after we put the ccts parts in them they drop to .426 gal/hp hr. I can get them down to .347 but the peak cylinder pressure and temp. gets to high and they won't pass emission testing.  you won't believe the hp tq numbers they come up with.

Don

[wg4t50]

Want some additional power from your 8v-92, find a good turbo from a 6V-92 and use 9200 injectors in your mechanical babe. Make sure you have good gaskets on the airbox covers, they WILL LEAK.

[Don Fairchild]

My 8V92 is DDEC but I had the injectors rebuilt and used the 9-.0062 tips like a 9A98. The 9200 uses a 7-.007 tip they flow the same amount of fuel, I also use the high load spring and seat and an extra shim to build pop pressure.

On my 8V71TA I use 125's with a waste gated 12.7L 60 turbo and going up a hill will bump the waste gate at 32 lbs. I kept breaking the air box doors on the dyno so I had a friend of mine water jet doors out of 3/8 steel and we milled a recess in them for the gasket, I then made boxes for three middy valves on each side and run 1 1/4 Aeroquip lines to them. one on each end and the middle. If you are not setting down when you romp the throttle it will throw you down and it has 3:36 gears with 24.5's on it.

I am not going to put the hp and tq numbers on here every time I do I get several f-you pm's and phone calls telling me I can't do that and what an asshole I am. ( I am an asshole but who cares )

I have a guy that comes by from time to time that run's Bonneville with a twin turbo 6V71 and uses 145's in it. We are trying to have a set of 160's built for him

Don

[wg4t50]

Don, I see we have a lot in common, agree on not telling too much as we get labeled incorrectly. Can tell you a ported / cleaned up heads on a 8V-92 with the 145's 6V-92 turbo plated air box covers, will truly amaze one, into the 3.73 rear, 11R24.5 RTO 910 at 2650 rpm in a 1955 Senicruiser is too far for me today, you need to do those things while your younger and less bright, been there & done that, also played the 12V-71 in the MC7.
Another reason I am happy today with the simple ISM500 in a 30,000 lb coach.  Am too old& stiff to crawl all over them today.
Dave M

[robertglines1]

Lift off      Do you strap the blower??

[wg4t50]

When fuel was under $1,00, was fun time. less than 5 mpg, who cared.