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RPM VS Knots

DIESEL engine, transmission and generator repair and maintenance discussion forum.
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Lyndon670
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Re: RPM VS Knots

Postby Lyndon670 » October 22nd, 2014, 5:58 pm

We are all glad that this is your last post.

Your previous post to your "last post" backed up exactly what I said - I even reiterated the simple calculation for you so you could understand the image that YOU posted.

I'll re-reiterate for you, one last time:

"we recommend a cruising speed of at least 200RPMs less than wide open throttle" (that's what you posted)

2300RPM x 10% = 230RPM

2300 - 230 = 2070RPM
2300RPM - 2070RPM = 230RPM

EITHER WAY, ITS "at least 200 RPMS less than wide open throttle" AS PER YOUR POSTED DOCUMENTATION.

I don't need to post documentation, you are arguing it for me.

I am not entering into a war of wits with the unarmed.

Thanks for proving my data so I don't have to.

You are right though, every website does have one. You proved that fact also.
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Volvo 7.4TAMD
Queens Cove Marina
Georgian Bay, Ontario

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Re: RPM VS Knots

Postby Hugo » October 22nd, 2014, 8:56 pm

Oh boy, it sounds like you failed English in school. Now I see what the problem is. I wasn't going to reply but this is for the benefit of others.

"we recommend a cruising speed of at least 200RPMs less than wide open throttle" is saying exactly what I'm telling you not what you're saying.

The key phrase here is "at least", you're not understanding what this says.

Read it about 50 times and get someone that understands English to interpret that for you.

That is saying exactly what I'm telling you, cruise at a speed of "at least" 200 rpm less, in other words the lower you go the better, not the other way around. At least 200 rpm is saying 300, 400, 500 rpm off of WOT is okay, not the way you're reading it.

The way you're interpreting that the phrase "at least" would imply that cruising at 100rpm off the top or WOT is okay, no manufacture is going to rate a high performance diesel at those numbers. Engines that are run at these power levels are de-rated to meet that duty cycle but you clearly don't understand what duty cycle is either.

Before you reply with more garbage to fill your EGO actually read what I wrote, you're not reading it, you just want to be right no matter what. It's okay to be wrong in life my friend that's how we learn.
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Lyndon670
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Re: RPM VS Knots

Postby Lyndon670 » October 22nd, 2014, 10:10 pm

Oh look, Hugo is back! And now apparently I don't have a grasp of the English language!

I wasn't going post this, but Hugo wasn't going to come back either....

From my Volvo Manual:

Copied from Volvo D9 Manual ......

Pg71
Operation
Cruising speed
Avoid operation at full throttle, for best fuel economy. We recommend a cruising speed which is at least 10% below the
maximum engine speed at full speed (full throttle). The maximum
engine speed will vary due to propeller choice, load and sea conditions, but it should be in the full throttle range.

If the engine does not reach the full throttle range, this could
be caused by a number of factors which are noted in the
“Fault tracing” chapter. If the engine speed exceeds the full
throttle range, select a coarser pitch propeller. Ask your
Volvo Penta dealer for advice.

(They are going to change the last line to read "Ask your Volvo Penta dealer for advice - or Hugo)
Lyndon,
2000 Carver 506
FOXY JOE
Volvo 7.4TAMD
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Georgian Bay, Ontario
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Re: RPM VS Knots

Postby Hugo » October 22nd, 2014, 10:37 pm

I don't know what else I can say to help you understand what you're reading. :banghead:

"at least 10% below the maximum engine speed at full speed (full throttle)" Means don't cruise over 90% WOT but it does not mean you have to cruise at 90% of WOT!!!! It's quite the contrary; they're trying to tell you not to exceed a cruise speed of 10% off of WOT!. Less rpm is better is what they're saying. :banghead:

I've beaten this horse dead. You need to get someone else to help you understand this. Print it and take it to your Volvo tech or something, you're not understanding what I'm saying or what you're reading. For the last time I will tell you that it's the opposite of what you think.

Volvo needs to reword that so that people like you understand it...

No, they won't ask Hugo because Lyndon's approach is more profitable - more piston meltdowns and shorter engine life. After all Volvo wants to sell and repair engines...
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Re: RPM VS Knots

Postby CYO Admin » October 23rd, 2014, 5:27 am

Gentlemen. While I appreciate a good debate as much as the next guy there is absolutely no need for personal attacks "of any kind" on this forum. There are plenty of forums where it's allowed, and the norm, but this isn't one of them.

Take it down a notch.
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PhilH
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Re: RPM VS Knots

Postby PhilH » April 21st, 2018, 2:54 am

Hey, guys. My understanding is that continually running a diesel at low rpm's like idle does not allow the engine to really heat up fully, help seal the rings, prevent blowby, adds mopisture to the crankcase, and builds up carbon deposits on the pistons. That said, my training was that diesels last longest when run at 50-80% of rated load, just like your generator. I think the life of a diesel depends more on maintenance, regular fuel and oil filter changes, and frequent use. Many engine mfg recommend you dont run max rpm continuously, and suggest continuous loads or loading not to exceed more than 90% of max power. That said, probably frequent oil changes will prolong the life of your engine more than any other single thing. Just my opinion.
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Kby
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2003
VOLVO TAMD 63 twin

Re: RPM VS Knots

Postby Kby » June 21st, 2019, 2:50 pm

Hello guyz,

I need your help I have carver 444 with volvo penta tamd 63p.

My issue is speed the max speed that the boat runs currently is 10 miles with an RPM 2100 I noticed that there is a lot of black and grey smoke while running.

Is there anyway to increase the speed or what should i do in this case.
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Kby
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2003
VOLVO TAMD 63 twin

Re: RPM VS Knots

Postby Kby » June 21st, 2019, 3:47 pm

Hello guyz,

I need your help I have carver 444 with volvo penta tamd 63p.

My issue is speed the max speed that the boat runs currently is 10 miles with an RPM 2100 I noticed that there is a lot of black and grey smoke while running.

Is there anyway to increase the speed or what should i do in this case.
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km1125
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Re: RPM VS Knots

Postby km1125 » June 22nd, 2019, 1:46 pm

The first question would be... how clean is the bottom??

How clean are the engine filters?

I'm sure that boat will do well over 10, but you have to figure out if the boat is loading down the engines or if the engines are having trouble developing power.
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tonyiiiafl
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Re: RPM VS Knots

Postby tonyiiiafl » June 22nd, 2019, 4:38 pm

As the owner of many diesels I have always gone by the rule of 80% WOT is the cruising speed. Had Detroits and Cummins with well over 10,000 hours with no ill effects.

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