| Author | Message | ||
| Bob Baldwin (Bob4106) (66.56.100.54)
Rating: N/A |
I have a 1961 4106 and notice in the book.(maintenance manual). I don't have a DD book. 565.5 CU.IN. 17:1 compression ratio and 235 brake hoursepower at governed speed (1650) But what is the horsepower and torque rating. Where can you find a DD book on an 8v71 and whats the going cost for then | ||
| DonTX/KS (66.82.9.13)
Rating: N/A |
The 4106 sales brochure had the best one I have ever seen, a chart with HP and torque plotted on a graph. VERY interesting chart it is, I hope someone can copy it for us, I loaned mine to a 4105 guy and he must have liked it too, been four years and he still has it. The torque falls off rapidly after about the 1150 rpm point as I recall, JL Vickers, I bet you have a copy of that brochure, right? | ||
| Bob Baldwin (Bob4106) (66.56.100.54)
Rating: N/A |
That would be nice because i just find it so interesting to see how much torque that some of the diesel motor have.(stump puller) And wanted to know since so many people have turn up their motors and run at a different rpm now that what the book saids. | ||
| J.L.Vickers (209.34.15.19) Rating: N/A |
According to the PD-4106 specfications booklet that I just happend to find it states and I quote! Engine 8V/71 Displacement (cu.in.)567.4 Bore and Stroke 41/4" X 5" Compression Ratio 17:1 60cu. mm.injectors (std) B.H.P.@ 1650 rpm 235 Torque (max.ft. lbs. at 1200 rpm) 770 272 hp at 2000 rpm. 4-1/8 axle ratio 60 mph at 1650 rpm. 2100 rpm I would say around 75-80 mph? This is my guess. jlv | ||
| DonTX/KS (66.82.9.36)
Rating: N/A |
Thanks JL. Wait til he gets the chart out though, the torque falls from 770 to about nothing at 2100 rpm. GM has you set the VS2 so that it cannot be shifted down above 1150 rpm, and will shift up at 1700 no matter what you do. | ||
| Bob Baldwin (Bob4106) (66.56.100.54)
Rating: N/A |
Thats one thing I was looking for Don.I had a feeling it was around 1100 to 1200 rpm and shifting was around 1800 (now thats what I was thinking and going by motor sound don't have a tack) | ||
| DonGeneda@ (66.82.9.43)
Rating: N/A |
They did not need a tach when they come from the factory. RPM was set like 1950 usually, and it was very easy to tell when you were there, it just stopped accelerating and of course did not hurt a thing! The city bus geared boys found that screwing up the governor to 2200 or so let them get off the porch and run with the big dogs almost, did not care that the main effect was only to burn lots more fuel at much lower torque. | ||
| Geoff (Geoff) (66.238.120.53)
Rating: N/A |
You know, I don't quite understand this torque thing. Is max torque where you get your best fuel milage? It certainly isn't where you get your power, as in horsepower. A standard timed 8V71 with N60 injectors produces 277HP @ 2100 rpms, once you start dropping rpms all you do is start to lose all your power. Max torque might be at 1200 rpms, but you are lucky to climb a curb at 1200 rpms. --Geoff '82 RTS CA | ||
| FAST FRED (65.154.177.119) Rating: N/A |
Normally a diesel has a relativly flat torque curve , but yes the torque peak is the place for the max fuel economy. Thats why the DD gensets for Prime power were 1200 , with the shorter lived standby at 1800.And early coaches like mine (GM) were gov to 1650 ,a compromise for economy, and longevity. At one time some mfg. would release the Fuel Map , which is a graph of the power/fuel burn showing the ranges of best economy. Looked like a cloud on a weather map with an area of best economy , surounded by lower & lower efficency (higher fuel burn per hp). The new busses with the 2 overdrives (and a computer to watch for overloads) is an attempt to operate the engine closer to the torque peak low RPM. On the flats it only takes 95 to 150 hp to cruise , so no need to scream the engine for such a low power output. FAST FRED | ||
| DonTX/KS (66.82.9.48)
Rating: N/A |
My points exactly Fred. I have heard, but not confirmed, that the ideal sweet spot is where the torque output and HP output CROSS on the charts. JL Vickers snail mailed me that chart on a 4106, I will post it when it arrives. I know from personal experience on my bus, lowering the cruise RPM dramatically increased fuel mileage. I drove a friends 4106 automatic (VS2-8)from Charleston SC to Topeka KS on a tank of fuel, and had enough left over to go half way back there again! Of course the VS2 would not even let the engine speed over 1650, yet the cruise was far faster than the law allowed. Automatics don't eat fuel, RPM's do. | ||
| Geoff (Geoff) (66.238.120.27)
Rating: N/A |
1650 rpms is pretty low for operating the engine, 1700-1800 is as low as I would go with a 71. | ||
| DonTX/KS (66.82.9.14)
Rating: N/A |
Same old discussion Geoff, GMC thought quite differently of course than you. I think that we are talking apples and oranges really, GMC wanted the old engines to never exceed 1700, and they certainly must have known what they were doing. The VS2 manual even cautions against increasing the shift point to higher RPM's. The engine "your generation" uses is quite a bit different than the old 235hp 8V71 bus engine, and the torque curve is definitely different too. The common old "318" Jimmy truckers drove was also different, and a lot of the "drive em like you hate em" stuff cames from them. I don't know when and where it all got modern, but the discussion was specifically about a 4106. I put a lot of miles on mine at lower RPM, sure did not hurt it, never used oil or fell apart. Do you have the rpm/torque chart for your engine? I know Mallie has some for later engines, and it is dramatically different figures. Some of it also comes from the term "lugging". We all know we should not do that, but just what the hell IS lugging (for an 8v71)? Obviously in a bus that is designed so you cannot shift down until you are pulling below 1200, made to pull an entire grade at 1200, and cannot go over 1700, that is NOT lugging. Don't forget, unlike the Eagles and MCI and whatever, the GMC bus with an Allison VS2 and 8v71 was ENTIRELY designed by GMC, not just an assembly of whatever they could buy cheap from someone else to stick in there. My information concerns the oldies, has nothing to do with an 8V92TA with twin turbos on it. | ||
| Geoff (Geoff) (66.238.120.27)
Rating: N/A |
The 4106 8V-71 is the same engine as the trucks used, the only difference was that the bus engine was standard timed and used smaller injectors. Both used N-injectors and 4-valve heads. I think the difference you are pointing out is that Greyhound wanted the engines set up for the best fuel milage, while the truckers wanted the power. Like I said before, the power is up at the top of the rpm scale. The 92 is basically the same as the 71, only it has bigger pistons and a wet liner to take the additional heat away better. Comparing the 92 series and the 71 series, the 92 has a wider torque curve than the 71 and will actually keep pulling at lower rpms than a 71. Getting back to driving the stock 4106 at low rpms, the small injectors will let you get away with running it at low rpms-- you HAVE to shift up to get any power out of the engine so this keeps you from lugging it. By lugging it, I mean giving the engine more fuel than it can burn to the point of overheating the clyinders. Even so, lets examine the 4106-- a very light bus to begin with, so getting 10 mpg is easy to achieve with the 4-speed. Okay, lets look at Henry Draper's big and heavy raised-roof Eagle with an 475HP 8V92TA and a 10-sd(?) Roadranger-- I believe he said he got up to 8 mpg on his last trip. --Geoff | ||
| DonTX/KS (66.82.9.70)
Rating: N/A |
I agree and believe that is all very accurate, and that is why I specified that FOR THE STOCK 4106 this is the way it is. I have heard many theories of just why the buses were set up the way they were, would be neat to know why they REALLY made them that way. I tend to believe that the small injectors, no tach or pyro specs were so they could hire anybody to drive em, and nobody could hurt em, as much as it was for fuel mileage. Remember in the era we are talking about, gasoline was 14 cents a gallon and diesel was cheaper, the cost of fuel was not a big issue then, and we would have called anybody a liar that claimed the cost of fuel in 50 years would be where it is today. | ||
| Bob Baldwin (Bob4106) (66.56.100.54)
Rating: N/A |
yes it looks like they where built ahead of their time. Some one or ones really but a lot of thinking in to it. And alot of the parts shows that. I can not beleive some of the things they came up with 40 years ago and how they are still doing the job today | ||
| FAST FRED (63.234.22.76) Rating: N/A |
The stock 60 injectors can not be lugged , if you are not loosing RPM. IF you may have enough power to climb the grade at over 1150 RPM the 60's will not cause "Bucky Balls" (black smoke from overfuling), and if the cooling systwm is halfway maintained , they will NOT overheat. We are able to drive the tiny East Coast speedbumps , virtually always without shifting down.The instalation of a 4905 gearset in the 06 , is mountain gears and helps backroads hillclimbing even more. The belching black smoke is for the fellows with defuler injectors, not a stock well maintained coach. Fuel milage is mostly a detirminant of frontal area vs speed. Weight counts but not a lot. Sleak , no 8ft sat dish , no rows of carbunkle air coolers , no antenna farm , air horns or tug boat spotlight , is best way to get over the majical 10mpg. Works for me ,(though the mountain gears don't help milage) FAST FRED | ||
| Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A |
Pure BS Fred, I believe. Steve Sanford from Texas ran a test a couple of years ago over several hundred miles, with and without roof air conditioners. He stated that the mpg was exactly the same with or without the A/C units. He used to contribute to the boards frequently. Do you have any FACTS to support your opinions? Richard | ||
| DonTX/KS (66.82.9.36)
Rating: N/A |
And while you are at it FF, add in the reference to figures on how much drag that FM radio antenna is going to cost us in MPG. That has GOT to be a biggie, and I have yet to see the figures on that. I once walked away from an MCI out on the interstate, I noticed as I passed, he had a little 2 ft whip FM antenna dragging in the breeze, must have been the reason I passed him so easily. Then again, maybe he just wanted to go the posted limit and I was in a hurry. | ||
| Prather (207.69.138.201)
Rating: N/A |
When I first got my Eagle 05 with a 8v71 and N60 injectors I got 9.5 mpg, took out the seats, raised the roof and got 9 mpg, added 10k pounds into the conversion and now get 7 mpg. I have a nine speed manual, shift up at 2100 RPM shift down at 1400 RPM. Engine heats in the mountains if I drop below 1400, it likes 1800 RPM for the best cooling. Prather | ||
| DonTX/KS (66.82.9.36)
Rating: N/A |
You might want to look at the fuel consumption charts for an answer to it all. It would appear that the added weight makes you run higher RPM and that makes your fuel mileage worse. You are lucky, with that 9 speed you can put it just where you want it to be, assuming you can get some decent speed in 9th with fairly low rpm. | ||
| Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A |
snip "Fuel milage is mostly a detirminant of frontal area vs speed. Weight counts but not a lot." FF Prather, that is the kind of information I like to see posted here. Actual facts to support your statement. Based on this information, I believe the quote from FF is more BS that is unsupported by fact. Your experience is just the opposite of what he stated. ie. Your frontal area increased but mpg only decreased .5 mpg. However a change in weight by 10K lbs. decreased mpg by 2. Who are we to believe, actual experience, or unsupported opinion? Richard | ||
| Jim Ashworth (Jimnh) (172.211.199.214)
Rating: N/A |
When I first bought my Prevost it weighed 42,500lbs, had roof airs. One trip from FL to NH to CO and back to NH with the cruise on 65 (because of the excess weight) I got 6 mpg. After re-converting it, with no changes to the exterior, it weighs 38,000lbs. I now drive 70 or better and the fuel mileage over the last two years is averaging 5.4 mpg. Actual experience shows that speed, not weight is more of a contributing factor. That info just has to be worth more than $.02 ! Jim | ||
| Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A |
Great Jim. Actual experience means a lot. I have always been of the opinion that speed is the determining factor, but have not posted anything as it was always just an opinion. Your experience lends credence to that opinion. Richard | ||
| Geoff (Geoff) (66.238.120.78)
Rating: N/A |
I think it's a combination of speed and rpms. I get my best fuel milage on the freeway CRAWLING at 55mph, but as the song goes, I CAN'T DRIVE 55... | ||
| DonTX/KS (66.82.9.26)
Rating: N/A |
Well, in theory, it is the barn door being pushed thru the air thing, and it goes up drastically with speed increases. For some reason, I did not find that to be as true as paper said it should. I am a "fast cruiser" and yet did not notice the drop at higher speeds (75-80). I suppose it was because of my gear ratio which was far off from almost any other normal bus(I was dramatically overgeared, so maybe at higher speeds I was more in the best rpm range for economy). For most buses, faster means quite an increase if RPM, perhaps past the best economy place. | ||
| jim wilke (12.46.52.74) Rating: N/A |
Well Don, GMs are more aerodynamic than most, too. About 4 years back there was a guy who had hooked up with one of the original GM 4104 bus project engineers. He said GM had done a lot of wind tunnel testing & learned that the 12" radius they used was the best compromise between aerodynamics & interior space. Jim-Bob | ||
| FAST FRED (63.234.22.210) Rating: N/A |
Any aerodynamic text will give the relationship beteween ,speed and drag. Its locatedin your local library for FREE! It is true that some coaches are so terrible from an air drag view that a whole ocean of air is dragged along with the coach. These will suffer loads less from row after row of carbunkles and that antique 8ft sat dish. If you have the back issues of BC mag , way back when there were usefull articles , there was one by Bob Belter (if memory serves) on coach air drag. On autos there working hard with the congress to repeal the laws about TV screens in drivers view. The reason is to get rid of the DRAG of the rear view mirrors! For the sake of better CAFE. If its worth this much bribery , just for a bit of windage , consider the size of a single rooftop air carbunkle to the size of a set of rearview mirrors! Do it your way , 10 MPG and a nice uncluttered exterior is my way , and works for me. If you work at it hard enough , if there is another backyard conversion coach purchase in your future , perhaps 3 MPG would be a fine goal, not for me tho. FAST FRED | ||
| Jojo Colina (Du1jec) (209.75.20.72)
Rating: N/A |
Here is a link to a Performance chart for 8v71N with N65's http://www.cwis.net/~mallie/page17.html Thanks to Mallie | ||
| DonTX/KS (66.82.9.27)
Rating: N/A |
A very good one too. Notice the difference between the 60 and 65 injectors in regards to torque rpm and amount. | ||
| TWO DOGS (66.90.218.60) Rating: N/A |
has anybody tried putting a turbo on a stock 8v71,looks to me it's just screamin' for it | ||
| Geoff (Geoff) (66.238.120.78)
Rating: N/A |
I notice that the peak torque is at 1600, not 1200. | ||
| DonTX/KS (66.82.9.44)
Rating: N/A |
Better read it again Geoff, clearly says 1200 rpm, with the C60 that came in the 4106. Scroll down to the specs just below the chart. I will have the 4106 chart from GMC posted for all to see as soon as it gets here by mail. | ||
| C Fred (67.72.98.110)
Rating: N/A |
If I was so set on gettting the highest fuel milage that can be had I would not buy or convert a coach. I want to live in my coach like I do at home. I don't want to be hot in summer and cold in winter. I want to watch TV and take a hot shower. I want to eat like I do at home and I want a good nights sleep. If it cost me one or two miles per gallon so be it other wise I would stay at home. I build mine to use and that is what I do. Fred North Florida Bus Conversion | ||
| DonTX/KS (66.82.9.29)
Rating: N/A |
I can agree with that perfectly Fred. Far too much space is spent on MPG and lying about it. Still, some of us can be inquisitive enough to explore things like this rather than just ignoring "that thing" in the back that makes noise and smoke, can't we? Many of us "live" buses, they get a bit more personal than just another old bus glitzed up for resale, and understanding these things cannot be all bad. I am sure there are many like you that could not give a flip about horsepower or torque or mileage, but we find it interesting, as does the person that just bought a bus and is trying to learn about such things. | ||
| Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A |
Right on Fred. I am 1000 percent behind you and if I only get 5 miles per gallon then that is better than the 4 miles per gallon I got on my last stick and staple with a 460 Ford. Some of the others can get a bicycle and backpack and get away from the rest of us if they like. Richard | ||
| Bob Baldwin (Bob4106) (66.56.100.54)
Rating: N/A |
I agree I did not buy the big bad bus for good fuel milage. I bought it to convert to MY likings.To travel where I want to go. As well as having a small home with me. What more can I ask for. When people ask me about milage. I ask them. What will they get pulling their home to where they want to go. Because I have everything I need here. | ||
| Geoff (Geoff) (66.238.120.161)
Rating: N/A |
I looked at Mallie's chart (again), and read the specs. The chart shows the highest torque at 1600 rpms (800), but for the sake of comparison the specs only list what the torque is at 1200 rpms (770). So the highest torque IS at 1600 rpms. Also, at 2100 rpms the torque is 760, very close to what the torque is at 1200 rpms (770). So with your governor set at 2100 (full load) rpms, you are climbing the torque curve as the horsepower drops until you get below 1600, where it starts to drop again. So, the shift point shouldn't be lower than 1600 to maintain the best torque and horsepower when climbing a grade. I wish I could see a 92 horsepower/torque chart like this one-- the 92's have a wider torque range. | ||
| DonTX/KS (66.82.9.43)
Rating: N/A |
Nope, just not so. I will prove it when the mail gets it here. Torque on a 4106 is definitely less at 1600 than at 1200, and the rating at 1200 is chosen because that is where it peaks. Like I said earlier several times, that does not apply to ALL diesels by a long shot, only to the 4106 detuned 8V71. The four strokes have a considerably different torque curve also. | ||
| Geoff (Geoff) (66.238.120.161)
Rating: N/A |
Yes, I didn't notice that the chart was for the N65 injector, and the lower specs are at peak. You got me! | ||
| DonTX/KS (66.82.9.39)
Rating: N/A |
Yeah, I thought that was going on there. Want a shock? Somebody publish the torque for a 3406 Cat and then be prepared to cry if you don't have one in the bus. | ||
| TWO DOGS (66.90.214.63) Rating: N/A |
I'm already cryin' cause I don't have a cat 425 | ||
| Tom Caffrey (Pvcces) (65.74.64.127)
Rating: N/A |
What I would like to find is some sharts or other information that show part throttle performance. I've never seen any, only full throttle ones. Anybody have any idea how I can come by that information? Tom Caffrey PD4106-2576 Suncatcher | ||
| DonTX/KS (66.82.9.34)
Rating: N/A |
Sure Tom, I got it in my hands, and for YOUR bus too! JL Vickers came thru with the mail. Not sure how to get it on this board, so will Email you a copy in a few minutes when I get it scanned. | ||
| ChuckMC9 (Chucks) (66.167.143.104)
Rating: N/A |
Don, I'll figure a way to get it on the board if you want to email to me as well. -Chuck | ||
| DonTX/KS (66.82.9.30)
Rating: N/A |
OK, on the way! Thanks | ||
| ChuckMC9 (Chucks) (66.167.143.104)
Rating: N/A |
Don's data -    Happy to be of service - I'm off to go bang on a bus! -Chuck | ||
| DonTX/KS (66.82.9.30)
Rating: N/A |
Thanks. Now you can see why the Allison VS2 could not be shifted down before dropping to 1150 rpm. It would also be fun for someone with a stick shift stock geared 4106 to shift up at 1650 rpm and see how low the tach was when in the next higher gear. That range is called "what GM wanted", and obviously is NOT lugging. This is a later version from the one I had, mine never mentioned the higher HP at a higher RPM even, I suppose they had to do that to make it more competitive. | ||
| Geoff (Geoff) (66.239.48.59)
Rating: N/A |
I cannot believe that they actually put a bus on the road that had the governor set at 1650! It is confusing that they turn around and advertise the horsepower at 2,000 rpm if they had the governor set at 1650. Anyway, I remember "the old days", and Greyhound buses were famous for passing everybody on the road, and it wasn't at 60 mph! | ||
| DonTX/KS (66.82.9.25)
Rating: N/A |
Isn't that interesting? Can we have such a faulty memory? I recall some very fast ones back 50 years ago, or was it that since they were so darned big they just seemed to go fast? My 4905 NEVER saw greater than 1700 rpm, and would run very well at 80mph range, and due to gearing would turn 142 mph if you could find one helluva tailwind going down a very steep hill. Things have changed! If you think what we had as cars back then, no wonder they seemed fast maybe. I can still recall trying to run down a 3751 GMC Greyhound to get a soldier back on it who had been left in the restroom during WWII. Dad had that little 4 cyl 60 hp 1940 Willys acting like a racecar, and it took us miles and miles to catch that bus! | ||
| Geoff (Geoff) (66.239.48.59)
Rating: N/A |
My memory isn't faulty, I am talking about the 60's and 70's, when Greyhound was running 4106's and Scenicruisers. You might have some advertising in print, but the truth is they turned up the governors up big time. When I worked for Detroit we used to find the high-speed governor nut screwed in all the way on buses-- a simple trick the driver's learned. I don't doubt the Greyhound mechanics went along with it too... | ||
| DonTX/KS (66.82.9.17)
Rating: N/A |
Ah ha, the plot thickens, and I think you are probably correct! We have heard from old greyhound guys for years that the GMC's of that era were governed slow by request of Greyhound. I never bought that theory because the 4905 was governed slow too, and Greyhound never ever bought even one of those. So I guess the mystery that remains, is why on earth would GMC turn down the governor, limit top speed to 60, and sell it as a 235hp bus, when we all know that a faster, more powerful (272hp) bus could have been sold much more easily, simply by turning up the wick. The smell of lower taxes or some government sanction is there. The sales person could hand out the brochure book, then whisper "Hey, you know with a simple adjustment, you will have a 272 hp bus that will run faster than 60". Sure would be nice to scare up a GMC salesman. | ||
| TWO DOGS (66.90.216.103) Rating: N/A |
the buses wern't sold to indaviduals...they were sold 50 and 100 at a time to major companys...salesman said '15 mpg'........the SHOP MECHANIC said "here ,look at this screw " (to the driver).......on bigtrucks...the fleet mechanic is required to set the screw at "good fuel mileage" ,and then put bondo over the screw to prevent tampering |