Suping up my school bus

[Anthrobus]

So on my checklist for my conversion, is doing some engine mods. On a 6 cylinder Cummins what would you guys recommend to increase fuel economy and or increase horsepower and performance. I've got a stock turbo on it right now is there a better one I should upgrade to? I've Been Told instead of upgrading the turbo to simply just Advance the timing. Has anyone else here tried this? Are there any negatives to doing this as in damaging the engine negatives? Are there any how to videos on doing this in a school bus? Thanks in advance.

[cadillackid]

the FIRST thing you do if you are going to start power-adding is install a Pyro gauge as close to the manifold outlet or right before the turbo you can get..



a bigger turbo wont do you anjy good until you can add fuel.. the turbo simply puts more air in the cylinder... with more air you can burn more fuel. (which makes more power)..



advancing the timing can sometimes net more power depending on where the timing is now.. (I dont know the 5.9 24 valve spercifically).. it also can increase cylinder temp.. this why the pyro is important....


you can definitely have fun with poiwer adding!

-Christopher

[Jolly Roger bus 223]

Research and learn what you have?
If you do have the Cummings engine then there are many resources on the WWW that can help get more? Like caddiekid said. Find the HP rating of your specific engine and figure out if it can be turned up or not?
Turning an engine up out of its original design gets into how long it will last?
I can re-power what I have to go faster or just be happy with what I have? Run the back roads that I love anyway or interstate speed? Much rather stay out of the rat race at 70-80 mph and hit the backroad's at (49-50)? Might piss a few people off but it is still faster than a tractor or combine in the road

[cadillackid]

I should also add dont forget your transmission .turnon up the torque can also destroy inadequate transmissions and break worn or weak U joints
Christopher

[Darvin]

I have a post on this a few weeks again. The industrial engine s are a lot harder to turn up if it’s the 24 v. If it’s 12 v then it s super easy

[Tango]

The older "B" series engines are the easiest to tweak (4BT/6BT). Almost TOO easy. Cadillac is dead on. Don't go anywhere with it until you have an EGT telling you what is going on and definitely know the limits on the trans. Can't begin to count the number of folks who have cranked them up only to destroy them and or the trans. Easy to get carried away.



If you are running a "one wire motor" I do have some excellent tuning specs for that engine put together by one of the sharper minds over on "4BTSWAPS.COM".

[cadillackid]

As much as I harp on purpose building your rig.. ie why do you need 600 horsepower to tow a Subaru in a short bus... as an old hotrodder I always go back to the fact that power-adding is just plain fun!

Christopher

[somewhereinusa]

I had a 5.9 in a Dodge ram. last year of mechanical. Bruce at Pittsburgh Power said it was making over 400 hp. It only really had two mods, more fuel(easy with mechanical pump) and a different exhaust side of the turbo, no waste gate and smaller dia outlet. I put over 150,000 miles on it that way. Didn't have a pyro but, should have. I did have to replace a couple of exhaust manifolds. I regularly grossed over 27,000 lbs and averaged over 13 mpg. It would pull most mountains in 5th gear with the cruise on. I put 260,000 miles on it in 2 years, then bought a semi.

[cadillackid]

that sounds like one mean arse 5.9.. what was it the guys on the dyno did last year? something like 1800 Horsepower before the block came apart? there was a cool youtube video floating around of the dyno run where that 5.9 block burst so fast that the crank was still spinning after the rest of the engine flew across the room..
thasts one strong engine to take even half that power..

-Christopher

[Ronnie]

towing in 5th gear? 5th gear has broken so many times for me, and have a few teeth missing off the overdrive in the aux. as well. 5.9 is a great engine but tranny's do not like it.

Mine is a 96 with the N-4500, and three speed spicer aux that I added.

[cadillackid]

sounds like a weak tranny! there are plenty of other transmissions out there that last behind 5.9s.. put an allison 6 speed auto in and be done with it.
-Christopher

[Ronnie]

Or put it in front of the 6 speed allison already in the bus with the bus attached to it....

The truck has seen better days at this point so really do not know what I will do with it. Local use only for now, and yes kind of keeping it in reserve for the engine if the bus engine gives up. Although the bus has really low miles so that is not likely anytime soon.

[cadillackid]

agreed its always good to keep a spare motor if you have the space.. also esp handy if you want to do any power-adding to your bus.,. you have a spare engine for parts if you break something.. I almost always had a couple extra 4 bolt SBC short blocks in my garage when I was a hotrodder.. now that im into busses. and messing with my 444E ive been looking around for a decent one to stuff away in a corner..
-Christopher

[BriteLeaf]

Originally Posted by Anthrobus

So on my checklist for my conversion, is doing some engine mods. On a 6 cylinder Cummins what would you guys recommend to increase fuel economy and or increase horsepower and performance. I've got a stock turbo on it right now is there a better one I should upgrade to? I've Been Told instead of upgrading the turbo to simply just Advance the timing. Has anyone else here tried this? Are there any negatives to doing this as in damaging the engine negatives? Are there any how to videos on doing this in a school bus? Thanks in advance.

Following 🧐

[ddcam]

24 valve? First is add pyro guage,and electronically controled. add achip... you can then adjust for low end power, mid, top end on hiways.... Then if not enough bigger injectors, better upgrade injector pump,then you can go with bigger turbo... Should not need all of that Check exhaust temps,watch tranny temps, and chip you will be happy I bet...

[Tango]

Still not clear exactly WHICH 6 hole Cummins we are dealing with here, but the following does apply to any P-Pump, all mechanical 4 or 6 BT Cummins. Got the following reply regarding tuning specs from one of the brighter minds over on 4btswaps.com. Thought it worth sharing.



Great project. You've done several good things with the engine. Two of the areas I always recommend checking are the turbo and injectors. The third area that might warrant some attention is the injection pump. You're focusing on good work and there are some improvements in the pump that are worthwhile. If you haven't already, install a 3000 RPM governor spring. Although you won't be running that speed, it helps with gear shifts. Second, consider changing the torque plate in the pump to a #10. That one has decent manors and can provide a significant power increase when needed. Third, adjust the timing to 16 deg. No higher or you risk blowing a head gasket. That will help with power and may improve fuel mileage as well. Last thing is possibly change the fuel overflow valve in the pump. Those things have a spring that gets weaker over time and can cause a loss of power. There are aftermarket items which are vast improvements over the stock unit. All of these changes are not expensive and can be done with the pump in place. A turbo boost elbow would also be advisable to help tune the boost level to take advantage of the new power. Your 130 HP engine can quickly become 200 HP without any bad effects on the engine or sacrifice of fuel economy. You'd basically be making the engine more efficient. And of course the power can go up even further. About 250 HP would be the limits for a stock turbo and injectors. After that point you'd be looking at other mods and don't think you're looking in that direction. A solid 200 HP would feel like you had a big block gas engine in there.
Of all the changes I mentioned, the timing adjustment would probably the hardest. That one requires loosening the the nut on the pump gear and a few special tools to accomplish the job. The governor spring would be #1 in order of importance. Then the torque plate and boost elbow. The change in timing would probably be one of the last things, but can have a huge impact on performance. Changing the overflow valve can be done in a very short time. It's also the cheapest. All the changes may be done for around $300 in part cost, depending on how well you shop. Probably the most bang for the buck on a P pump engine.




And...don't consider turning up the power without installing an EGT!

[BigPaul367]

Advancing the timing can only be done with a Tuner Computer! This is very limited. If you use a 'Hot Rod' tuner, good luck, most of those cause more bad than good!

[Ronnie]

On the older all mechanical ones you can not use a "tuner", you physically turn the injection pump. These are the ones Tango is referring to.

[Tango]

Yes...the info posted is as noted only for...


"...P-Pump, all mechanical 4 or 6 BT Cummins".

They have the advantage of...


A. Not requiring a computer to run...and...


B. Not having a computer to screw things up!

[cowlitzcoach]

Originally Posted by Anthrobus

So on my checklist for my conversion, is doing some engine mods. On a 6 cylinder Cummins what would you guys recommend to increase fuel economy and or increase horsepower and performance. I've got a stock turbo on it right now is there a better one I should upgrade to? I've Been Told instead of upgrading the turbo to simply just Advance the timing. Has anyone else here tried this? Are there any negatives to doing this as in damaging the engine negatives? Are there any how to videos on doing this in a school bus? Thanks in advance.

You don't mention which 6 cylinder Cummins engine you have, in which bus the engine is, what your transmission is, or what your rear end gear ratio is currently.

If your rear end gear ratio is high numerically you will not go any faster at redline, you will just get to that speed faster and stay at that speed longer while going up a hill. The problem that occurs when you keep your foot buried in the throttle while going up a hill is you can literally melt the engine down from too exhaust temperatures too high. So install a pyrometer as the first order of business.

If your engine is a 6BT/ISB of 180-200 HP it likely has the Allison AT540 transmission. Adding HP to an Allison AT540 is a great prescription of blowing up the transmission. Or cooking it from overheating the transmission fluid. If you have the AT540 I wouldn't bother adding any HP as you won't experience any great increase in fuel mileage if you do. What you will do is overheat the transmission sooner and you will also get it a whole bunch hotter more often. If you have the MT640 or one of the newer OD transmissions like the 1000, 2000, or 3000 series you will not have as much of a problem overheating the transmission. But be aware of the HP and Torque ratings of the different models of transmission. The ratings are fairly conservative but adding more HP or torque than what the ratings recommend will not result in a long trouble free life for the transmission.

Regardless of anything else, you are going to need to increase engine cooling capacity. If you have a Type 'C' conventional bus swapping the stock radiator for a larger one is not too difficult. You may actually find an OEM style radiator that will bolt into place with very few modifications. If you have a Type 'D' FE (front engine) bus adding additional cooling capacity is going to be a bit of a fabrication problem which may require creating a new front grille and modifying the front bumper. If you have a Type 'D' RE (rear engine) bus adding additional cooling is going to be a problem. There is not one bus manufacturer yet who has figured out the answer to prevent a rear engine bus from overheating. All of the OEM's have been fighting this issue since the first rear engine buses were made back in the '30's and '40's. The problem all stems from trying to move air from a low pressure area around the rear of the bus into a high pressure area inside the engine compartment, across the radiator core, and then out the back of the bus. Adding additional cooling capacity isn't going to work unless you can get more air to flow across the radiator in volumes large enough to cool the engine down. Some OEM's have mounted auxiliary radiators to supplement the stock radiator. Some OEM's like K-W Pacific, Gillig, and Flxible have utilized scoops of one kind or another on the roof at the back of the bus to help force more air through the radiator. The scoops had varying degrees of success.

The way in which your bus was built was to maximize performance at the least cost for the HP and Torque rating that was checked off on the order sheet. Since most school buses spend 90%+ of their service life at speeds less than 35 MPH very few of them are optimized for cruising at highway speeds. As a consequence changing route bus into a highway cruising bus is usually a bad idea financially. It would be a whole bunch less expensive to find a bus that will cruise at highway speeds than to pay for what it is going to cost to upgrade everything.

Good luck.