road friendly
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road friendly
Hey folks! new to the site and would love to hear any info regarding a possible 2 speed rear installation in a 84 school bus I own,actually I own two, both with rebuilt 8.2 detroit diesels, with 3 speed Allison auto trans. Right now it takes an act of congress to get them over 60 on the flats, and I like to keep the revs below 3500. Seems every one I know with this set up that pushes much beyond that ultimately ends up throwing a rod. Your thoughts would be appreciated.
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Mark R. Obtinario
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Which Allison transmission do you have that is only a 3-speed?
The AT54X, MT64X, and HT74X are all 4-speed and the MT65X, and HT75X are all 5-speed.
I certainly hope you are keeping the RPM's below 3500. In fact you should be well below 3500. Redline on those engines is 2600 RPM's. Turn them any faster for any amount of time and you will certainly throw a rod.
Remember, the 8.2L is what it is. It is a medium duty diesel engine built to be a throw-away engine that was never designed to be run with a turbo. Most versions were in the 160-190 HP range. They can be pumped up but the reliability and heat becomes a real problem. Heat will become the limiting factor more on a rear engine bus than a front engine bus due mostly to air flow.
Expecting it to push/pull a bus at speeds of 60 MPH or more is really asking a lot of it.
If you were to regear to a highway gearing that would allow you to cruise comfortably at speeds in excess of 60 MPH you will end up grinding up every hill at very slow speeds.
Again, it is what it is.
If you want to be able to cruise at speeds in excess of 60 MPH and scoot up the hills above a walking pace you are going to need more than 300 HP. Modern intercity motorcoaches are able to travel at the speeds they travel because they have 450-525 HP engines with overdrive transmissions.
In regards to 2-speed rear ends, don't waste your time and $$$. Shifting a 2-speed rear end with an automatic can be dangerous if you try to do so while the bus is in motion. The only buses I have seen with automatics and 2-speeds the shift switch was in the engine compartment and not accessible except for when the bus was parked.
In addition, if you were able to shift on the fly, your top gear choice isn't going to be all that different from what you most likely have already. I think the fastest 2-speed gearing I have ever seen was 4:56.
I have seen many buses with 4:11 gears with Cat 3208(T) engines. Even with a turbo and 250 HP they were slugs on hills. They would fly on the flat but forget hill climbing ability.
Good luck with your bus(es).
Mark O.
Winlock, WA
The AT54X, MT64X, and HT74X are all 4-speed and the MT65X, and HT75X are all 5-speed.
I certainly hope you are keeping the RPM's below 3500. In fact you should be well below 3500. Redline on those engines is 2600 RPM's. Turn them any faster for any amount of time and you will certainly throw a rod.
Remember, the 8.2L is what it is. It is a medium duty diesel engine built to be a throw-away engine that was never designed to be run with a turbo. Most versions were in the 160-190 HP range. They can be pumped up but the reliability and heat becomes a real problem. Heat will become the limiting factor more on a rear engine bus than a front engine bus due mostly to air flow.
Expecting it to push/pull a bus at speeds of 60 MPH or more is really asking a lot of it.
If you were to regear to a highway gearing that would allow you to cruise comfortably at speeds in excess of 60 MPH you will end up grinding up every hill at very slow speeds.
Again, it is what it is.
If you want to be able to cruise at speeds in excess of 60 MPH and scoot up the hills above a walking pace you are going to need more than 300 HP. Modern intercity motorcoaches are able to travel at the speeds they travel because they have 450-525 HP engines with overdrive transmissions.
In regards to 2-speed rear ends, don't waste your time and $$$. Shifting a 2-speed rear end with an automatic can be dangerous if you try to do so while the bus is in motion. The only buses I have seen with automatics and 2-speeds the shift switch was in the engine compartment and not accessible except for when the bus was parked.
In addition, if you were able to shift on the fly, your top gear choice isn't going to be all that different from what you most likely have already. I think the fastest 2-speed gearing I have ever seen was 4:56.
I have seen many buses with 4:11 gears with Cat 3208(T) engines. Even with a turbo and 250 HP they were slugs on hills. They would fly on the flat but forget hill climbing ability.
Good luck with your bus(es).
Mark O.
Winlock, WA
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Mark R. Obtinario
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In regards to your transmission, if it is an Allison there should be a builder's tag on the left side (right side in a rear engine bus) of the transmission.
In regards to your rear gears, if it isn't stated on the bus body builder's plate inside the bus it should be on a tag on the top right rear of the rear end (or top left front on a rear engine bus).
In regards to your rear gears, if it isn't stated on the bus body builder's plate inside the bus it should be on a tag on the top right rear of the rear end (or top left front on a rear engine bus).
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Stealth Camper
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I have a 76 International (345 cu/in. gas) with a two speed rear-end. Hi range is about 6.33 and low is about 8.4. I am looking for a sacrificial truck or bus to get rid of that mess. And pick up a diesel and maybe a transmission, too.
I really don't think you want a two speed.
One thing about it; in low/low, there is NOTHING that can beat me off the line for about the first 8-10 inches. Rev it up good and pop the clutch! Takes off like...well, like a turtle...but a very fast turtle for a tenth of a second or so.
I really don't think you want a two speed.
One thing about it; in low/low, there is NOTHING that can beat me off the line for about the first 8-10 inches. Rev it up good and pop the clutch! Takes off like...well, like a turtle...but a very fast turtle for a tenth of a second or so.
road friendly
Mark ....my mistake, meant 4 speed ,to many vehicles, with to little memory to keep them straight. I'm not to surprized to hear your take on things. I suppose I inherantly knew that I was limited to what I might be able to do with this set up, but hope springs eternal, and I have limited knowledge on drive trains. I have seen a few newer front powered school buses that are capable of cruzin speeds above 60 . Not sure if they were powered by Internationals or Cat motors , or what displacement. Any knowledge on that subject or suggestions on repowering. I appreciate your thoughts and your kind responce. It has been very helpful!
sincerely,
Terry
sincerely,
Terry
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Mark R. Obtinario
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Terry your re-power options are pretty unlimited as far as choices are concerned. The limitations have more to do with practicality and $$$$.
To start with, with what sort of platform do you have--Type 'C', Type 'D' front engine, Type 'D' mid-engine, or Type 'D' rear engine?
What you have will in large part determine what choices you may have for repowering.
If you are wanting to repower with another diesel engine you have a choice to two basic types--heavy duty and medium duty.
Heavy duty will have HP ratings starting about 300 HP and go well over 600 HP. The redline for all practical purposes on heavy duty diesel engines is 2100 RPM. If your bus is slow while turning your engine in excess of 3000 RPM you will be really pokey at 2100 RPM.
Medium duty will have HP ratings starting about 140 HP and top out around 350 HP. Like your 8.2L, most medium duty engines redline at 2600 RPM.
HP costs $$$. The more HP you want the more it will cost you. Not only do higher HP cost more but everything else has to match the HP or you will be breaking down or overheating all the time.
I personally do not like Cat engines for various reasons. Probably the most important reason now is Cat no longer makes any engines for onroad applications. This will limit the aftermarket and used market in the future.
Cummins has made two good medium duty engines that have seen service in a lot of different applications--the 5.9L/ISB and the 8.3L/ISC. The 5.9L/ISB would be similar in performance to what you have currently but it would climb hills better. The 8.3L/ISC would be a major step up. Cummins also made the 555 V-8. It is best used for a door stop or boat anchor.
IHC has made several medium duty engines, four of which have seen a lot of service in a lot of different applications. The 6.9L/7.3L/Powerstroke/D444(E), DT(A)360, the DT(A)466, and the DT(A)530. The 6.9L/7.3L/Powerstroke/D444(E) would be a step down from what you have already. The 360 would be about the same powerwise but a lot better at pulling hills. The 466 would be a step up and the 530 would be a big step up. IHC also made the 9.0L V-8. It was very similar in design as what you have and would be a step backward for you.
If you opt to really power up and go to something like a DD Series 60 or a Cummins 350/400 be aware that you will also have to upgrade your transmission, driveline, and cooling system. Trying to use what you have currently will just not cut the mustard with the higher HP and torque of the heavy duty diesel engines.
If you haven't already converted your bus your best bet would be to sell what you have and purchase a bus with the engine that you want. Repowering is never going to be easy or cheap. So unless there is something about the bus you have that you really like...
If you do opt to repower, purchase a complete power package that includes the wiring harnesses. You will need the correct electronics to operate the newer engines and transmissions.
Regardless of which engine you chose, your current transmission will not work without some revalving and changes in the governor.
Good luck and happy trails.
Mark O.
Winlock, WA
To start with, with what sort of platform do you have--Type 'C', Type 'D' front engine, Type 'D' mid-engine, or Type 'D' rear engine?
What you have will in large part determine what choices you may have for repowering.
If you are wanting to repower with another diesel engine you have a choice to two basic types--heavy duty and medium duty.
Heavy duty will have HP ratings starting about 300 HP and go well over 600 HP. The redline for all practical purposes on heavy duty diesel engines is 2100 RPM. If your bus is slow while turning your engine in excess of 3000 RPM you will be really pokey at 2100 RPM.
Medium duty will have HP ratings starting about 140 HP and top out around 350 HP. Like your 8.2L, most medium duty engines redline at 2600 RPM.
HP costs $$$. The more HP you want the more it will cost you. Not only do higher HP cost more but everything else has to match the HP or you will be breaking down or overheating all the time.
I personally do not like Cat engines for various reasons. Probably the most important reason now is Cat no longer makes any engines for onroad applications. This will limit the aftermarket and used market in the future.
Cummins has made two good medium duty engines that have seen service in a lot of different applications--the 5.9L/ISB and the 8.3L/ISC. The 5.9L/ISB would be similar in performance to what you have currently but it would climb hills better. The 8.3L/ISC would be a major step up. Cummins also made the 555 V-8. It is best used for a door stop or boat anchor.
IHC has made several medium duty engines, four of which have seen a lot of service in a lot of different applications. The 6.9L/7.3L/Powerstroke/D444(E), DT(A)360, the DT(A)466, and the DT(A)530. The 6.9L/7.3L/Powerstroke/D444(E) would be a step down from what you have already. The 360 would be about the same powerwise but a lot better at pulling hills. The 466 would be a step up and the 530 would be a big step up. IHC also made the 9.0L V-8. It was very similar in design as what you have and would be a step backward for you.
If you opt to really power up and go to something like a DD Series 60 or a Cummins 350/400 be aware that you will also have to upgrade your transmission, driveline, and cooling system. Trying to use what you have currently will just not cut the mustard with the higher HP and torque of the heavy duty diesel engines.
If you haven't already converted your bus your best bet would be to sell what you have and purchase a bus with the engine that you want. Repowering is never going to be easy or cheap. So unless there is something about the bus you have that you really like...
If you do opt to repower, purchase a complete power package that includes the wiring harnesses. You will need the correct electronics to operate the newer engines and transmissions.
Regardless of which engine you chose, your current transmission will not work without some revalving and changes in the governor.
Good luck and happy trails.
Mark O.
Winlock, WA
road friendly
Mark-
Thanks for responding so quickly, and as warned , you seem to be a well spring of knowledge! Your thoughts on repowering certainly are helpful and pragmatic. With the effort and costs involved it truly might be wiser to do as you say and look for something that does have the muscle already fitted. I have done an initial conversion but as you probably know the first attempt is usually an education on how to do it right or better the next time.
As far as the rpms on this engine goes, I had a diesel mechanic suggest I remove the governor and gave no warning of over reving.I'm sure I have had it over 3 grand a few times going down hill. Even then I did'nt feel comfortable with that engine speed. I'll have to consider myself very lucky to have all my rods still inside the block. I will be much more cautious in the future! Thanks for the warning.
Sincerely,
Terry
p.s... Gee, I wonder why they put governors on them?
Thanks for responding so quickly, and as warned , you seem to be a well spring of knowledge! Your thoughts on repowering certainly are helpful and pragmatic. With the effort and costs involved it truly might be wiser to do as you say and look for something that does have the muscle already fitted. I have done an initial conversion but as you probably know the first attempt is usually an education on how to do it right or better the next time.
As far as the rpms on this engine goes, I had a diesel mechanic suggest I remove the governor and gave no warning of over reving.I'm sure I have had it over 3 grand a few times going down hill. Even then I did'nt feel comfortable with that engine speed. I'll have to consider myself very lucky to have all my rods still inside the block. I will be much more cautious in the future! Thanks for the warning.
Sincerely,
Terry
p.s... Gee, I wonder why they put governors on them?
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Mark R. Obtinario
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How does one remove the governor on a diesel engine?
On a diesel engine the governor is part of the injection pump. You can adjust the stop up or down but you can't eliminate it.
You can also adjust the pressure up or down for more or less power--translation adding or subtracting the amount of fuel available.
Changing either from stock calibration can have serious and very expensive consequences down the road.
On a diesel engine the governor is part of the injection pump. You can adjust the stop up or down but you can't eliminate it.
You can also adjust the pressure up or down for more or less power--translation adding or subtracting the amount of fuel available.
Changing either from stock calibration can have serious and very expensive consequences down the road.
Depends entirely on the pump design. The only diesel injection pump I am familiar with is the Bosch VE (and asian knock-offs). On this pump design, maximum RPM is set solely by the position of the control arm connected to the accelerator. Adjusting or removing the set screw that limits the full-stop travel of the arm affects the top RPM. Remove the set screw and valve float is your new governor (assuming you have valves).Mark R. Obtinario wrote:How does one remove the governor on a diesel engine?
On a diesel engine the governor is part of the injection pump.
You can adjust the stop up or down but you can't eliminate it.
On these pumps, maximum fueling ("power" adjustment) is accomplished by adjusting the set screw that controls the injection window duration. Internal pump pressure is set to a hundred pounds or so by a bypass regulator and an orifice on the return port. The only important function of internal pump pressure is to provide mechanical advance for the injection window timing. Delivery pressure is set by the injector spring shims, but has little effect on power, although this can affect timing to a degree.
On turbo models, the pump includes an aneroid diaphragm to increase fueling under boost. This has a few associated adjustments of it's own, including the "smoke screw" and "star nut".
These pumps were used extensively on the early Dodge/Cummins trucks. They can be tweaked up quite nicely for more power. Incresing the diameter of the plunger and/or recontouring the cam plate can turn them into competition components.
Sharkey
> Bosch VE IP's
Where might I find more info on this stuff. Besides idle curiosity, I happen to run one of these in the Nissan Maxima I drive (LD28 engine). Al Savage, proprietor of nIssandiesel.dyndsn.org and a committed gear head who has spent a lot of time working on Nissan diesel engines, feels that the internal pump pressure may degrade with high mileage leading to incorrect timing advance; he looks askance at possible wear of the internal lift pump vanes in the IP. My Ford 6.9 also uses this variant... I think. Happily I've not had to look at anything below the oil fill on that engine yet, although it has made very clear to me that it doesn't like ULSD straight!
Rufus
> Bosch VE IP's
Where might I find more info on this stuff. Besides idle curiosity, I happen to run one of these in the Nissan Maxima I drive (LD28 engine). Al Savage, proprietor of nIssandiesel.dyndsn.org and a committed gear head who has spent a lot of time working on Nissan diesel engines, feels that the internal pump pressure may degrade with high mileage leading to incorrect timing advance; he looks askance at possible wear of the internal lift pump vanes in the IP. My Ford 6.9 also uses this variant... I think. Happily I've not had to look at anything below the oil fill on that engine yet, although it has made very clear to me that it doesn't like ULSD straight!
Rufus
road friendly
Gentlemen.... It seems I must choose my words very carefully on this site, removing the governor was a figure of speech, adjusting would have been the correct term. Thanks to both Mark and Sharkey for your input. It shows the complexities surrounding the diesel engine.
Terry
Terry
Rufus;
Here are some pages of info about the VE:
Basic design and operation:
http://www.cs.rochester.edu/u/jag/vw/en ... jpump.html
Tech info, including photos:
http://home.comcast.net/~vwgtd/vepump.htm
Tuning the VE for performance:
http://dodgeram.org/tech/dsl/more_power/Power_ve.htm
There used to be a scanned version of the VE service manual, but my link now returns a 403 Forbidden message, guess it's off limits now.
Here are some pages of info about the VE:
Basic design and operation:
http://www.cs.rochester.edu/u/jag/vw/en ... jpump.html
Tech info, including photos:
http://home.comcast.net/~vwgtd/vepump.htm
Tuning the VE for performance:
http://dodgeram.org/tech/dsl/more_power/Power_ve.htm
There used to be a scanned version of the VE service manual, but my link now returns a 403 Forbidden message, guess it's off limits now.
Terry, this is serious thread hijack, but here goes . . .
Rufus, the IH 6.9's Stanadyne DB2 IP is not a "VE" design or variant. It's got it's own weaknesses, but I don't think its advance mechanism requires a comparable level of housing pressurisation as does the VE design. It's also got an external lift pump
The VE is, per Bosch's labelling, a "Distributor" pump. Its lift pump is also its housing pressurisation pump, and while I don't have hard numbers, my limited testing here implies that the Bosch-licensed Asian variants seem to have trouble keeping the housing pressure up after a few tens of thousands of miles. Because this directly affects the performance of the timing advance, high-RPM timing is retarded due to lower housing pressure (the cam plate is advanced hydraulically: lower pressure = less advance). Retarded timing = smoke.
The VE design is optimized for high-RPM diesels; the LD28's top speed is around 4400 RPM, as is the VW's. I don't know what the governed RPM is for the older Cummins ISB's that utilized the VE design, but in any event Cummins seems to have dropped using the VE design pretty fast
For IDIs, the IPs with plunger pumps (Bosch calls theirs their "Inline" pump") work most reliably as long as you don't need high RPMs. See the Nissan SD22 & 23 (but not the SD25, as it went to the VE design). The plunger/Inline pumps have more pressurized pieces to adjust and calibrate than the Distributor IPs, and poorer accuracy at high RPMs; I suspect that to be a reason why they've not been "electrified" as much as the Distributor IPs for IDIs.
The Bosch "Yellow Book" for both the Inline and Distributor IPs are cheap and available from Amazon; I own them both and they are evidently translated from the German, as they are not exactly easy reads.
Finally, how many IDI engines are in use in the medium & heavy truck market? Maybe in days of yore . . .
Rufus, the IH 6.9's Stanadyne DB2 IP is not a "VE" design or variant. It's got it's own weaknesses, but I don't think its advance mechanism requires a comparable level of housing pressurisation as does the VE design. It's also got an external lift pump
The VE is, per Bosch's labelling, a "Distributor" pump. Its lift pump is also its housing pressurisation pump, and while I don't have hard numbers, my limited testing here implies that the Bosch-licensed Asian variants seem to have trouble keeping the housing pressure up after a few tens of thousands of miles. Because this directly affects the performance of the timing advance, high-RPM timing is retarded due to lower housing pressure (the cam plate is advanced hydraulically: lower pressure = less advance). Retarded timing = smoke.
The VE design is optimized for high-RPM diesels; the LD28's top speed is around 4400 RPM, as is the VW's. I don't know what the governed RPM is for the older Cummins ISB's that utilized the VE design, but in any event Cummins seems to have dropped using the VE design pretty fast
For IDIs, the IPs with plunger pumps (Bosch calls theirs their "Inline" pump") work most reliably as long as you don't need high RPMs. See the Nissan SD22 & 23 (but not the SD25, as it went to the VE design). The plunger/Inline pumps have more pressurized pieces to adjust and calibrate than the Distributor IPs, and poorer accuracy at high RPMs; I suspect that to be a reason why they've not been "electrified" as much as the Distributor IPs for IDIs.
The Bosch "Yellow Book" for both the Inline and Distributor IPs are cheap and available from Amazon; I own them both and they are evidently translated from the German, as they are not exactly easy reads.
Finally, how many IDI engines are in use in the medium & heavy truck market? Maybe in days of yore . . .
I know sometimes, Governor's are set for as close as possible, to a particular "speed". School districts - some of them - have their buses set so the driver's can't go over 60. At least, that is what the mechanics told me where I worked at. 
They said it was for my protection - I couldn't be accused of going over the speed limit that way - what with my lead foot and all. I guess I "assumed" that was the norm. All of the buses I drove - except our trip buses, were Governed for about 60mph. Am I getting something wrong in this?
They said it was for my protection - I couldn't be accused of going over the speed limit that way - what with my lead foot and all. I guess I "assumed" that was the norm. All of the buses I drove - except our trip buses, were Governed for about 60mph. Am I getting something wrong in this?Who is online
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