2 cycle vs. 4 cycle?

[dgorila1]

Since I'm in the research/search phase and new to diesel engines, I wanted to get everyone's opinion of what  the pro's and con's of the older 2 cycle diesels vs. newer 4 cycle models. Is one better or worse than the other overall, cheaper to maintain and rebuild, etc? Maybe Brian from American Fleet can provide details based on his professional experience as well :-) Thanks.

[lostagain]

The 71 or 92 series Detroit can be very strong, reliable engines, as long as they are set up right, and maintained properly and regularly. The old 2 stroke mechanics are mostly retired now, and finding a competent one is a challenge, especially on the road. You have to be able to maintain and repair them yourself.

The modern 4 stroke is familiar to any diesel shop, so much easier to maintain and fix, if you are not a mechanic yourself. Also more fuel efficient, and half as much heat to dissipate.

If you don't have a bus yet, buy the latest model you can afford. That will be with a 4 stroke and auto trans. Make sure you get a bus with the powertrain you want, because an engine or transmission swap later can be very expensive.

Good luck.

JC

[Detroitenginespecialist]

There isn't a quick way to answer your questions without going into some details.  I do agree with the post above that basically is saying that you need to figure out your budget first and then go from there.  I personally would probably replace any engine that my bus came with unless there is significant documentation of the history of the work that was preformed prior to my purchase.  I would not recommend buying a bus with a plan of "up grading" the engine for more power.  That is asking for trouble in my opinion.  If more power is what you want, then buy a bus that has the engine you want it already.
 
American Fleet would probably turn down a request to take out a 6V92 and replace it with something bigger.  We are proponents of building an engine back to how it was originally built.  Because if you start trying to add more power, you will compromise other engine related components that might be affected by the engine upgrade.

If you choose a 2 cycle and do a minimum amount of engine work to "get by" then you run the risk of get stuck somewhere that won't have the parts available.  Going with a Series 60, allows you to have more accessibility to parts due to tractor trailer trucks running the same engine.  So therefore, parts are more readily  available throughout your travels.

Dependability – The Series 60 will last longer than a 2 cycle.  If properly taken care of,  a Series 60 will last into the 700,000 to 900,000 mile range with some components failing along the way.  But getting oil analysis from time to time will help you see what's going on inside your engine to better prepare you for issues down the road. 

Engine cost – depending on what 2 cycle you are considering, there could be a $2,000 – $4,000 swing between a 2 cycle and a series 60 non-EGR depending on which warranty you choose on the series 60.

I could continue with a few more points of view,but this post would start rambling on.  If you wish to continue this conversation please give me a call.

[bevans6]

Probably the biggest factor is what is in the bus you want.  If you have your heart set on a vintage bus, it probably came with a two stroke.  If it still has the two stroke, you will probably keep it in there and use it.  If you like newer buses they will come with a four stroke, since two strokes pretty much ended in the 1990's.  If you buy a 10 year old or newer bus, it will have a pretty modern four stroke and you will be dealing with modern electronics, sensors, engine controls, maybe EGR and other pollution controls, etc.

Everyone has their opinion on which is better.  I like my two stroke mechanically injected engine because I understand it, I can work on it and fix it with normal tools, and it's extremely reliable.   It uses no electronics, in fact it doesn't use electricity at all to run once it's started.  I have a modern four stroke computer engine in my pickup truck, and if it breaks I have to call a tow truck, there is almost nothing I can do to it without a computer to tell me what's wrong and what sensor to change.  If I was going at this with what I know now it would come down to budget.  No money, I would have a two stroke but if I could afford it I would have a four stroke in a newish Prevost, just before the pollution controls got stupid...

Brian

[Detroitenginespecialist]

Agreed on that last post.  I would definitely stay away from engines with EGR components.  If the Series 60 engine you are looking at has a serial number 06R0 (6) or (7).... more than likely its will be a EGR engine. 

[Seangie]

Go 4 cycle.  Save the money and get a bus that has a 4 stroke.

The only reason I would buy another 2 stroke is if the bus it came in was in great shape and I just fell in love with it and it was too good a deal to pass up.  But in that case I would save up to re-power to a 4 stroke.

We have a 2 stroke now.  Love it because its soooo simple to wrench on.  But I do wish we had a little more power, gas mileage and more mechanics to work on the engine.  Alot of times (like 3 out of 4) the shops along the road will just tell me they just don't work on 2 strokes.

-Sean

[luvrbus]

You won't find a 2 stroke in a bus that was made in the last 22 years 1994 was the last for highway use for a 92 series 2 stroke.
A 8v92 is a good engine electronic or mechanical if taken care of and not ran hot I have had those for years.
So far with my series 60(non EGR) electronic engine it is kinda of a love hate relationship what bothers me the most is the rough idle on a 4 stroke and the noise they are loud   

[dgorila1]

Thanks for all the replies, great info!

[TomC]

Even though I have overhauled and replaced virtually everything in the engine compartment, plus turbo'd my 8V-71 for better performance, I am converting my old '85 Kenworth with the Caterpillar 3406B mechanical. Quite possibly the most reliable mechanical engine ever made. So much so Caterpillar is still making the 3406C mechanical for 3rd world countries for pumps and generators, and also they have a natural gas version.
2 stroke engines are very reliable. But from one that has had both, I can safely say a 2 stroke Detroit is a lot more maintenance than the 4 stroke engine. MTU still makes the 6V-53TI, 8V-71TA, 8V-92TA for military use. And MTU still has parts for the 53, 71, 92, and 149 series. As said before, it's not the parts, it's finding someone that can work on the 2 stroke engines. If you want reliable, stay with a mechanical 4 stroke engine like the Caterpillar 3306, 3406, Cummins L10, M11, NTC. Then you'll have an engine anyone, including you could work on. My Caterpillar 3406B is just about maintenance free. Only thing to be done is overhead valve adjustment every 100,000mi, roll in bearings at 500,000mi and replace injector tips. Good Luck, TomC

[muldoonman]

My 1991 8V92TA is running great with 86,000 miles but was wondering if a 4 stroke replacement can be installed in a 91 Prevost. I've read Ken has a 4 stroke in his older coach and it was a pita with the tag and modified it to fit. My coach looks new as having been stored all it's life inside except for the short 2 or 3 day  runs we make. I  like the style (rivets) and the best part is I paid cash for it years ago. 

[Detroitenginespecialist]

muldoonman
Yes you can make that switch, but its not worth the money just to say you have more power.  It would be a huge undertaking to do it right.  If you want a bus with more power, then go and buy one. 

[luvrbus]

Kent Widdison installed a M11 with a Allison back in 2004 in his Prevost somewhere I have photos of the install not for the faint of heart RIP Kent.I have a friend that has one of the very few factory installed Cat engines and B500 in a 1998 XLL Prevost.
Before I spent the time,money and aggravation for a transplant I would buy a 8v92 DDEC lV with a charge air cooler @ 525 factory hp over1600 ft lbs of torque they will take you to the dance with series 60 and bring you home  

[muldoonman]

Kent Widdison installed a M11 with a Allison back in 2004 in his Prevost somewhere I have photos of the install not for the faint of heart RIP Kent.I have a friend that has one of the very few factory installed Cat engines and B500 in a 1998 XLL Prevost.
Before I spent the time,money and aggravation for a transplant I would buy a 8v92 DDEC lV with a charge air cooler @ 525 factory hp over1600 ft lbs of torque they will take you to the dance with series 60 and bring you home  

Yeah no problems with mine and it pulls good but was wondering. If I do anything would trade up to 4 stroke when the time comes if I can catch it before it blows. LOL.

[luvrbus]

Glen you are good for another 400,000 miles just feed it fuel and smile

[muldoonman]

Glen you are good for another 400,000 miles just feed it fuel and smile

Good to hear Cliff.