|
|
Mid-Missouri | 
Like last year, I might be taking the 5020 with the 8v-71 to a tractor pull. What is the max rpm I could semi-safely run with? I heard 4000 would be fine. It had the overhead ran a year ago and runs smooth. It has the variable speed governor and I have a book for these motors but could use some advice on adjusting the high rpm. I will have an air stop available to prevent a possible runaway. On a side note, do these 2 cycles respond well to an addition puff of propane while pulling? It is supercharged but not turboed. It weighs about 20,500 pounds and has duals full of fluid and a cab. It pulled good in fourth last year but didn't quite have enough grunt in fifth. Thanks
Edited by seedcleaner 9/11/2010 18:22
|
|
| |
|
Hagen Brothers farms,Goodrich ND | The rods might stay on to 4000, but I suspect the stock valve springs will put you into valve float at anything above 2700-3000 rpm. You dont want to float and drop a valve in that engine.
A 2 cycle Detroit is not really supercharged, that blower is more of a ventilation device to push clean air into the cylinders at the same time as it pushes the exhaust out the top. .I suspect it does not add more than 1 or 2 psi max of boost to the air charge, and remember that the exhaust valves are open any time the intake ports are open, so it can not produce much extra pressure in the cylinders.
You will gain a good power boost by aspirating propane into the intake air.
Max rpm of the VS governor is adjusted by removing spacer rings that limit travel of the spring cup, and by adding shims under the spring in the end of the spring cup.
Edited by Jon Hagen 9/11/2010 22:15
|
|
| |
|
Texas | A little advice , (please , Dont take this as a smart @ss comment).
I would not mess with the govenor on an old detriot , too many things could go wrong , #2 You have cast heavy duals and rice tires ,the diff might give up .
That is a real neat old tractor , id love to have it myself ,id hate to see it blown up on a pulling track . |
|
| |
|
Ravenna Ohio | If it is not a steel clutch and flywheel, don't even think about 4000 rpm. Just ask Jake at Pulloff.com to find the links to the exploded cast clutch reports. |
|
| |
|
Brazilton KS | If the exhaust valves are open any time the intake ports are open, how does a turbo do any good?
|
|
| |
|
Devils Lake, ND | Jon Hagen - 9/11/2010 18:40
...the exhaust valves are open any time the intake ports are open...
Not quite. The exhaust valves are open any time the piston is below the ports. If the intake valves are open at the same time, the blower pushes the exhaust out of the cylinder. |
|
| |
|
Cen IL | You would be better off to take the liquid out of the tires and hang on steel ballast. You'll expend a lot more HP trying to get that mass of weight in motion. |
|
| |
|
Hagen Brothers farms,Goodrich ND | plowboy - 9/12/2010 19:40
If the exhaust valves are open any time the intake ports are open, how does a turbo do any good?
Other than pressurizing the inlet side of the blower which reduces the power required to turn it, a turbo does do not do much for a 2 cycle Detroit. Remember a turbo only takes an 8V-71 from 318 hp to 350 hp, just about a 10% gain, likely about what it takes to turn that shaft drive blower under load..
Edited by Jon Hagen 9/11/2010 22:24
|
|
| |
|
Brazilton KS | The pistons ARE the intake valves. If the piston is below the port, then the blower can blow air through the port into the cylinder.
|
|
| |
|
Statesville, NC | wouldn't it help to build more intake volume/pressure in the cylinder if the exhaust was restriced some? Maybe that's done by the valve opening or duration. |
|
| |
|
Fruita CO | The exhaust valves close before the ports, to fill the cyl. after it's scavenged. Seems like the valve timing is a little different on turbo engines, but don't quote me on that...Detroit lessons were a long time ago...
PS-I don't think you need to worry about hurting the rear end of a 5020 on a sled-no matter the HP...
Edited by ronm 9/11/2010 23:23
|
|
| |
|
Hagen Brothers farms,Goodrich ND | Trent2520 - 9/12/2010 21:47
wouldn't it help to build more intake volume/pressure in the cylinder if the exhaust was restriced some? Maybe that's done by the valve opening or duration.
Good question that likely only an old Detroit 2 cycle engineer could answer.
Would restricting the exhaust to allow the blower and turbo to pack more air in the cylinder , overcoming the loss of exhaust scavenging caused by the restriction ??
Remember, the pistons do not push the exhaust out of the cylinders in a 2 cycle Detroit. It's the fresh air blowing in the intake ports at the bottom of the cylinders that pushes the exhaust out of the exhaust valves at the top of the cylinders |
|
| |
|
Kittitas Co. Wa. State | Neat looking 5020,, thou I am going deaf just looking at the picture. Got a 4-71 on a elevating scraper to fix fields with, I wear both ear plugs and ear muffs and am still deaf by end of the day. |
|
| |
|
West Chazy, New York | The easiest way to boost power in a Detroit is to replace the two valve head with a four valve head. Getting the exhaust out so clean air can come in is the goal.
|
|
| |
|
northwest tennessee | I agree why risk doing major damage to it pulling it and for what. |
|
| |
|
Devils Lake, ND | Forced induction motors, especially gassers, don't like a lot of intake/exhaust overlap; you just blow your boost out the back. Detroits are different, in that they need the boost to push the exhaust out of the cylinders. Their "overlap" is determined by the position of the exhaust ports in the sleeves.
More boost should help a 318, as you can still pack the cylinders after the piston gets above the exhaust ports. On a puller, I would prefer to speed up the blower (if that's possible) rather than add a turbo. The turbo will slow down exhaust scavenging. (I know the xV92's have turbos) maybe jerry-rig an aftercooler of some kind? |
|
| |
|
Fruita CO | Have you guys ever seen the gears in the ass-end of a 5020? You are NOT gonna hurt it w/318 HP on a sled, I think it would probably be good for 500... |
|
| |
|
Statesville, NC | Ok, now I'm confused. I thought the ports were for intake and the valves for exhaust? |
|
| |
|
| Yes, the ports are for intake; valves are for exhaust.
Rod |
|
| |
|
Devils Lake, ND | The other way around. The ports are 3/4 the way down the sleeve. When the piston is below that, the intake valves are open, and the boost pushed the exhaust out. |
|
| |
|
Hagen Brothers farms,Goodrich ND | RodInNS - 9/13/2010 12:59
Yes, the ports are for intake; valves are for exhaust.
Rod
Edited by Jon Hagen 9/12/2010 14:24
 (2 stroke Detroit.jpg)
Attachments
----------------
 2 stroke Detroit.jpg (29KB - 398 downloads)
|
|
| |
|
Bethany, MO | I wondered if anyone was going to figure out the limiting factor in this game! It won't be safe at 3000 much less 4000. You get the prize Oilfarmer!
Edited by bowtieighth 9/12/2010 14:49
|
|
| |
|
Fruita CO | No-no-no..maybe on your weedeater...
Edited by ronm 9/12/2010 17:32
|
|
| |
|
Devils Lake, ND | I stand corrected. I went all those years getting it wrong.
I know they can run in reverse, though. I did it one time. |
|
| |
|
Fruita CO | No argument there-saw that happen too... |
|
| |
|
Brazilton KS | But it takes a 92 from 365 to 475 and well beyond in marine apps. There has to be some boost involved in that.
|
|
| |
|
Brazilton KS | Aw, come on Ron...It's not like they were scraper tractors or anything :) |
|
| |
|
| The 8V-92N (no turbo) had a 2.6 to 1 overdrive blower. The 8V-92 Turbo and 8V-71 (318) have a 2.1 or 1.9 to 1 overdrive blower. Many years ago, I saw the 2.6 gears put in an 8V-92 Turbo to boost power and acceleration. It really worked, but more changes were done at the same time. I think the same gear set (you might have to change the rear housing) will fit the 8V-71. This is not something you can do in a few hours and fuel economy will suffer. |
|
| |
|
Hagen Brothers farms,Goodrich ND | plowboy - 9/14/2010 00:32
But it takes a 92 from 365 to 475 and well beyond in marine apps. There has to be some boost involved in that.
There may well be if the exhaust valve timing closes the valves before the intake ports are fully covered.
I wonder if those models of the 92 series also include an intercooler like the one we have in an old semi tractor. I believe the advertized HP of that "T I" one is 430.
If I get time today, I will see if any of my old DD manuals list max air box pressure.
I know it is low enough at idle that you can easily R&R an airbox cover with the engine running.
Edited by Jon Hagen 9/13/2010 08:48
|
|
| |
|
Brazilton KS | My guess (and this is pure speculation on my part) would be that the very high hp is raw water cooling and raw water aftercooling. At least that's the case on Cat's ultra-high marine ratings.
|
|
| |
318 Detroit: Max rpm for tractor pull?
