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Author Topic: 8V71 horsepower  (Read 1205 times)
Cary and Don
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« on: July 26, 2013, 12:17:52 PM »

We have been following Chris and Cheries engine build.  Their 8V71 with N65s is the same as our Eagle has.  We were a little stunned by their Dyno test of 250hp at 3500 feet.  We haven't taken our Eagle over 4000 feet yet.  We were planning on a trip this fall that would be taking us to the 7000 to 9000ft range pulling a Pathfinder.  If the Dyno was without the fan, air compressor, power steering pump, or generator,  does that mean that the final horse power installed will be lower?  Are we going to have problems pulling hills at this altitude?  How much trouble do you think we can expect on the hills and how fast do you think we will be pulling them? 

Don and Cary
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bevans6
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« Reply #1 on: July 26, 2013, 12:29:18 PM »

The final hp will indeed be lower, but the number that they achieved is pretty meaningless in terms of anything accurate.  They said the dyno was uncalibrated and turning the brake backwards, so it's amazing they got any number at all.  The altitude plays another part but there are calibrations that could have been done to compensate for the air pressure or lack thereof.  Bottom line the dyno was done not to measure power accurately but to make sure the engine started and ran properly with no leaks, all cylinders were firing, no abnormal smoke and to start to break in the rings.  They also got to set the low and high idle speeds accurately.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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LowTide
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« Reply #2 on: July 26, 2013, 12:53:32 PM »

If I may ask, what happened to the thread about updates? I assume you guys must be reading this somewhere...... I can't find anything about the rebuild  Huh

Mike
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Mike and Lori
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Dave5Cs
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« Reply #3 on: July 26, 2013, 01:04:19 PM »

Mike look on their website it all there.

Don I used to live in Colorado springs, Colorado. It was about 6,700 feet and if we went to the top of Pikes Peak it was about 14,000 our trucks performance change a lot. So any elevation change of a large number will take away a lot of power. Less on fuel injected vehicles especially computer regulated ones because the computer compensates for the lose of air. On our big motors if you don't have the DDEC then you will notice it in a lack of pulling power. Just means you will be going slower up hills. Enjoy the scenery!......  Grin

Dave5Cs
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Utahclaimjumper
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« Reply #4 on: July 26, 2013, 01:11:13 PM »

 Its why you have a transmission, lower the gear and speed to continue up hill at lower horsepower. The trucks have the advantage of many lower gears but are still in the slow lane, get use to it.>>>Dan
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Utahclaimjumper 
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« Reply #5 on: July 26, 2013, 01:16:53 PM »

 If you haven't been higher than 4000 Ft. then you have lived a charmed life, my house is at 5800 Ft. and 3 out of 4 directions is up,, we have lost 18 percent of power before reaching for the key. You can count on a loss of 2-3 percent per thousand feet above sea level when climbing if not turbocharged.>>>Dan
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Utahclaimjumper 
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luvrbus
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« Reply #6 on: July 26, 2013, 01:18:27 PM »

250 hp won't be far off 90% of the 6v92 Ta engines running down the road in buses are only 270 hp with 9A90 injectors they go as low as 240 hp I don't read their blog what rpms was the 250 hp
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« Reply #7 on: July 26, 2013, 02:12:23 PM »

250 hp won't be far off 90% of the 6v92 Ta engines running down the road in buses are only 270 hp with 9A90 injectors they go as low as 240 hp I don't read their blog what rpms was the 250 hp

2250 rpm
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OneLapper
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Cary and Don
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« Reply #8 on: July 26, 2013, 02:26:25 PM »

We live at 2600 feet.  It is just that all the trips we have taken so far went down hill to the ocean.  We have some steep grades, 8% here,  but the altitude hasn't got all that high, maybe 6000ft.

Don and Cary



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RJ
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« Reply #9 on: July 26, 2013, 06:48:06 PM »

How much trouble do you think we can expect on the hills and how fast do you think we will be pulling them? 

Don -

I just answered a similar question over on BNO earlier today!

Using I-80 between Sacratomato and Reno as an example, with a stock 8V71 (or 6V92TA) you'll pull the hill mostly in 2nd & 3rd.  The closer you get to Donner Summit (7,229' EB/7,337' WB) the more time you'll spend in 2nd gear at about 30 mph or so.

But don't worry, CalTrans has provided nice wide truck lanes for us slow pokes.  Grin

The WB climb out of Reno is shorter and steeper, but EB out of Sacratomato is longer (70 miles!) and more gradual.  If you have a Jake brake, you can almost come down either side w/o using the regular service brakes, or at least use them quite sparingly.

Just remember to shift the gearbox manually and keep the rpms in the 1700 - 1900 range on a partial throttle as you're climbing - watching for black exhaust smoke in the process - and you'll be fine.  Thousands of Trailways Eagles and Greyhounds ran these highways and byways with your engine, so it's almost a non-issue as long as you DRIVE the coach and not simply steer it.

FWIW & HTH. . .

 Wink
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RJ Long
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TomC
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« Reply #10 on: July 27, 2013, 04:40:20 PM »

Doing a chassis dyno-you can expect 80% of advertised horsepower at the wheels. 250hp÷.80=312.5hp-which is right on par of what a 8V-71 should be putting out. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
bevans6
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« Reply #11 on: July 27, 2013, 04:44:45 PM »

It wasn't on a chassis dyno, it was on an engine dyno prior to hanging all the accessories and final install.  You are very correct on the loss on the chassis dyno, though, based on my experience with race cars.  Usually the operator has a conversion factor and if he built the engine, he has an even better conversion factor...

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
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