Maximum Allowable RPMs

Topic: Maximum Allowable RPMs (Read 2895 times) previous topic - next topic

Maximum Allowable RPMs

May 14, 2012, 01:50:27 pm

This is a follow-up to my recent post regarding RPM range on our ISM 450. I talked with Cummins Support today and got the real deal from my motor's build sheet.

The "maximum overspeed" is 2600 RPMs for 15 seconds. The "high idle" is 2300 RPMs. The peak torque is between 1200 and 1600 RPMs. He suggested, as a couple of you did, thinking of 2100 as a max, thus allowing some cushion should I do an accidental downshift.
jor

Re: Maximum Allowable RPMs

Reply #1 – May 14, 2012, 02:18:59 pm

Quote from: jor – May 14, 2012, 01:50:27 pm

This is a follow-up to my recent post regarding RPM range on our ISM 450. I talked with Cummins Support today and got the real deal from my motor's build sheet.

The "maximum overspeed" is 2600 RPMs for 15 seconds. The "high idle" is 2300 RPMs. The peak torque is between 1200 and 1600 RPMs. He suggested, as a couple of you did, thinking of 2100 as a max, thus allowing some cushion should I do an accidental downshift.
jor

I noticed my 450 in the U320 is 60mph at 1250 rpm and gets 10mpg in perfect conditions.

Impressive.

Bob

Re: Maximum Allowable RPMs

Reply #2 – May 14, 2012, 02:51:14 pm

Interesting, I have played with many diesel engines, and I would say the L10, M11 and the ISM are about as rugged, dependable and economical as there are today. Know from experience the little L10 at Half million miles, you drop the pan and roll in new bearings, at one mil, you do the cylinder kits, cam bearings, fuel system and lower end and keep getting up. There are other engines that will do that, but they are few and far between.
The B and C series are great medium engines, but they will not go that distance.
Dave M

Re: Maximum Allowable RPMs

Reply #3 – May 14, 2012, 04:15:38 pm

Quote from: jor – May 14, 2012, 01:50:27 pm

The "maximum overspeed" is 2600 RPMs for 15 seconds. The "high idle" is 2300 RPMs. The peak torque is between 1200 and 1600 RPMs. He suggested, as a couple of you did, thinking of 2100 as a max, thus allowing some cushion should I do an accidental downshift.
jor

I would have assumed the Allison Tranny would not allow an engine overspeed if working as designed.

Re: Maximum Allowable RPMs

Reply #4 – May 14, 2012, 05:22:26 pm

Quote

I would have assumed the Allison Tranny would not allow an engine overspeed if working as designed.

When I get a chance I'm going to have Allison check mine out to see just what that overspeed number is. I know now that the if-you-exceed-this-speed-your-cummins-will-explode number is 2600 for 15 seconds and that the fast idle number is 2300. I'll post what I find out.

Also, I remain skeptical that the Allison would prevent an overspeed going downhill if the driver has selected too low a gear. The manual uses the word "may" instead of "will." I intend to get definitive info and to find out if maybe the previous owner of my coach (gear head speed demon like Dave) may have adjusted the Allison parameters.
jor

Re: Maximum Allowable RPMs

Reply #5 – May 14, 2012, 06:00:32 pm

jor, Just a question, I see you refer to your 99 320 as having the ISM450, Looking at Foretravels spec sheets, the 99 used the M11 Celect+ 450. this is not a ISM. SO I am wondering if your unit was a late 1999 unit and did get the ISM. I got into the M11 and ISM issues when I had mine upped from the 450 to 500 hp, was told that would not be possible before the ISM 2000 model year. There are more than a few differences between the M11 and the ISM.
Just wondering
Thanks
Dave M

Re: Maximum Allowable RPMs

Reply #6 – May 14, 2012, 06:34:09 pm

Good point, Dave. Matter of fact, when I bought this rig I thought I was buying the M-11 Celect+. As you point out, the FT brochure and spec sheet indicate it is equipped with the M-11. I hadn't really checked it out when I took it in for an oil change. I noticed on the receipt that they had noted ISM. I told the guy that it was an M-11. He drug me out to take a look and sure enough, it turned out to be an ISM. My build number is 5569 and the motor's date of mfg is 03/99.
jor

Re: Maximum Allowable RPMs

Reply #7 – May 14, 2012, 06:57:40 pm

jor,
That is great, in that case I guess it could be setup to the 500 hp, providing it has the wiring harness for the bypass turbo controller already on the engine, ft it does, then the computer on engine can handle the upgrade. Sounds great. Better if you can get me the Cummins engine number, I can get you the build sheet for it. Can forward it email.
Heck with the resonator and the 500 hp, and no slide on that 36', you would be looking for trucks, RV's and cars to pass on mtns.
Great
Dave M

Re: Maximum Allowable RPMs

Reply #8 – May 14, 2012, 07:50:44 pm

I'll take you up on that offer, Dave. The SN is: 34951382 and the family is: XCEXH0661MAH. My email is oiga at comcast dot net. Thanks!
jor

Re: Maximum Allowable RPMs

Reply #9 – May 14, 2012, 08:28:12 pm

OK, you are giving me a case of I wanna a 500.

Re: Maximum Allowable RPMs

Reply #10 – May 16, 2012, 05:25:51 am

jor, I emailed you the info for our engine number, DID you get it ??
Dave M

Re: Maximum Allowable RPMs

Reply #11 – May 16, 2012, 09:41:03 am

Quote

Re: Maximum Allowable RPMs
« Reply #10 on: Today at 02:25:51 AM »
Quote
jor, I emailed you the info for our engine number, DID you get it ??
Dave M

Just sent you a PM, Dave.
jor

Re: Maximum Allowable RPMs

Reply #12 – May 16, 2012, 02:35:58 pm

jor, I at present have no way of converyting the xps to the pdf for you, tired to post here, but it will not take a xps either, so since I am NOT a computer nerd, I hope you can find a local who can assist in converting it.
Your engine is a ISM450 built 10 Mar 99 and the CPL is 2608, built at the Jamestown Engine Plnat.

Dave M

Re: Maximum Allowable RPMs

Reply #13 – May 16, 2012, 02:41:11 pm

Quote from: Dave M – May 16, 2012, 02:35:58 pm

jor, I at present have no way of converyting the xps to the pdf for you

Dave,

E-mail it to us - we have full Acrobat software and I should be able to convert it for you and send you and jor the PDF.

Michelle

Re: Maximum Allowable RPMs

Reply #14 – May 16, 2012, 03:03:03 pm

Michelle, many thanks.
jor, thanks to Michelle for converting, here is you data.

Dave M

Re: Maximum Allowable RPMs

Reply #15 – May 16, 2012, 06:30:12 pm

Greetings to all,
This is an interesting conversation. I also have a 99 U320, build #5586, 40'. I was under the impression that I had the M11 but after reading the comments about RPM's, etc. I lifted the bed and sure enough, the letters ISM C are big and bold on the side of the valve cover. This also brings a question regarding the Silver Leaf engine designations. My version of silver leaf does not have ISM engines listed. Does the M11 450 designation come close enough to the ISM for proper management? Would appreciate any comments.
Thanks.
Richard Anderson
99 U320, build 5586, 40'

Re: Maximum Allowable RPMs

Reply #16 – May 16, 2012, 09:45:42 pm

Dave and Michelle, thanks a million.

Richard, I noticed that the VMS doesn't list the ISM 450 and I called Silverleaf to inquire. They instructed me to use the M11 engine category. Said it was the same. From what I can see (torque and hp numbers when driving) they are.
jor (using my wife's computer)

Re: Maximum Allowable RPMs

Reply #17 – May 17, 2012, 09:08:28 am

Thanks for the information, jor. Glad I don't have to change anything.
Best wishes,
Richard Anderson
99 U320, 40'

Re: Maximum Allowable RPMs

Reply #18 – May 18, 2012, 02:22:46 am

I to have the 99 U320 built in jan. 99, build #5522. Information on the cummins online quickserve shows that I have the ISM-RV 450. Also have ISM on side of the valve cover plate. Always thought that I had the M11 select plus. Engine serial number is 34940570, Engine built at the Jamestown engine plant 11 Dec 1998.

Re: Maximum Allowable RPMs

Reply #19 – May 18, 2012, 09:20:10 am

Guess we can narrow the changeover from M11 to ISM a bit. My '99 build #5512 also built in Jan '99 has the M11-RV 450E Plus. It was built at the Jamestown plant on 19 Nov 98.

Affiliate Notice