8V71N bus - bad decision?

[Geoff]

I don't know....  I have driven my bus in Oregon and have been down to 1st gear in a couple of spots in the steep mountains.  Never under 10-15 mph but still, that is with 350HP and 1025 ft lbs of torque and a 32-34,000 lb coach.

--Geoff

[Oonrahnjay]

I don't know....  I have driven my bus in Oregon and have been down to 1st gear in a couple of spots in the steep mountains.  Never under 10-15 mph but still, that is with 350HP and 1025 ft lbs of torque and a 32-34,000 lb coach.
--Geoff

     Is that with a 6V92, Geoff?

[Geoff]

     Is that with a 6V92, Geoff?

Yes, 6V92TA, 9G90 injectors, 350 HP. A nice, little workhorse.  V730 and 4:10 gears.

--Geoff

[Oonrahnjay]

Yes, 6V92TA, 9G90 injectors, 350 HP. A nice, little workhorse.  V730 and 4:10 gears.
--Geoff 

      Sure sounds like a good workhorse.  Does the V730 lockup at 1:1?  What's "best" cruise with the 4:10 rear?

[Geoff]

The V730 torque converter locks up in first gear, and the final drive is 3rd gear that has a .875 overdrive.  It will do 80 mph@2350 rpm's with the 4:10 rear gears.  The "best cruise" for fuel economy is 1800 rpms, which is 62 mph, but it is very hard to drive the bus that slow with 70-75 mph speed limits.  I've been getting 8 mpg keeping up with traffic so that's good enough for me.

BTW,  an 8V71TA @375 HP only gets 5-6 mpg, which is the same as an 8V92TA @500 HP.

--Geoff

[edvanland]

Don't care how fast I am going when I get to the top as long as it is not overheating I am good. Slower speeds I can enjoy the view.

[Scott & Heather]

I love my 500hp turbocharged 8v92 and I'll never look back.


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[windtrader]

I feel a lot better knowing what to expect now.  Sucking fumes from all you while I'll be crawling and creeping in the slow lane, "enjoying " the scenery. Lol

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[Geoff]

I feel a lot better knowing what to expect now.  Sucking fumes from all you while I'll be crawling and creeping in the slow lane, "enjoying " the scenery. Lol

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When you're in the slow lane climbing a hill you aren't watching the scenery, you are watching your mirrors as the trucks and cars try to get around you as you are creating a bottleneck and hope nobody gets in an accident!!  It is quite a scene when the cars want to go 70 mph and they run up to a truck that suddenly changes lanes in front of them to pass another truck going 15-20 mph or an old bus going 5 mph.

--Geoff

[Dreadnought]

I'm such a sad geek- I was curious about quantifying the performance of my MC5 without wrecking the actual vehicle.

I have a medium fidelity vehicle simulation package- that has proven VERY accurate for my 80s BMW M6, my Porsche 993 turbo and other classics with well verified performance figures documented. I've also used it with a lot of success simulating the performance and fuel economy of a Navistar International Pro Star fitted with the Maxxforce 13- verified to measurement data.

So I made some assumptions about the tyre coefficient of friction (Mu) for a commercial vehicle and for the drag coefficient and ran the simulation for my Bus.

The top speeds in gears tallied up to what I get on road - 17, 31, 54, 74 mph respectively assuming a 1900 rpm change up point- so this gives me confidence. this is with the 3.33 rear end I have.

the 0-60mph is showed to be just under a minute (49 seconds whether a slip start or a idle start),

Top speed is shown to be around 75 mph. That seems a little conservative.

This is assuming use of the 65 injectors to get 304 bhp. Mines actually around 280 with the C60s.

I did a run with an 8v92 TA torque curve- tuned to get around 470 bhp. This makes a massive difference and gets to 60 mph is around 22 seconds and a top speed above 90 mph-assuming the same gearing.

I've heard it said that the MC5 is the hotrod of the bunch because its lighter. I dread to think how the Mc8 with 8v71 NA accelerates!

On the road my bus feels pretty nippy, but a couple of weeks ago I was towing my BMW on a trailer- and although the top speed only fell to 72 mph it didn't feel too spritely!

[eagle19952]

I pulled Tioga Pass into Yosemite to Tuolemne Valley from Lee Vining pulling a 16 foot trailer loaded with my 8v71N no jakes. Up and down.

yes I saw 22mph. AND almost 11000ft. and 2-3 mpg
https://www.flattestroute.com/?from=Lee+Vining%2C+CA%2C+United+States&to=TUOLUMNE+VALLEY&travelMode=Bicycling&measurementMode=miles

and i also did it on 120.

[windtrader]

I pulled Tioga Pass into Yosemite to Tuolemne Valley from Lee Vining pulling a 16 foot trailer loaded with my 8v71N no jakes. Up and down.

yes I saw 22mph. AND almost 11000ft. and 2-3 mpg
https://www.flattestroute.com/?from=Lee+Vining%2C+CA%2C+United+States&to=TUOLUMNE+VALLEY&travelMode=Bicycling&measurementMode=miles

and i also did it on 120.

WOW! So many different  experiences. That's one major torture test. Being in the Bay Area, that's a route I'd likely take bout the reverse. Thanks

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[Geoff]

Don--

I am from the SF Bay Area and go back and forth from Arizona all the time.  Plus when I lived in Vallejo, CA, I can verify your earlier statement that any direction you take out of state is going to be a climb up a mountain.  What I wrote earlier about "climbing up a hill" in an old, underpowered bus is exactly true.

--Geoff

[windtrader]

Geoff,
Well all I can do is say I've warned plenty about a non turbo 8V71 so expect a slow slog up the hills/ There really nothing more I can do given the tradeoffs and limited budget for this hobby. I'm mentally prepared for the snail's pace up the bigger grades, that's all I can do on this first trip around the busnut carousel. I have the budget to get a Series 60 bus but it would be an empty shell. The compromise is a 8V71 that is fully converted and ready to go for the same $. Tradeoffs, tradeoffs, what ya goin do?

[Dave5Cs]

Don also you might want Jake's for your speed down the hills.....