Re: [Amel Yacht Owners] RPM on Volvo TMD22A, again...!


Erick MEJEAN <maramu@...>
 

Hi Daniel

You must consider two things when you look at an engine performance.
Power output and torque. Each engine has its own power curve and torque curve.
Both don't follow the same pattern and don't have the same meaning.
With regards to the TMD 22 it reach its peak power of 57.4 KW at 4500 RPM, but it reach its peak torque of 162 Nm at 2400 RPM.
At 4500 RPM the torque is down to 125 Nm.
While motoring you are more interested by torque than power as regardless of the power you will never achieve a higher speed than the hull speed.
Running an engine at its best torque does not make it labouring the sea as it is the time when the engine has the more strength.
The calculation of the propeller pitch takes into account all these factors. Changing the propeller pitch would be a big mistake as it will make your prop no longer adapted to the engine,transmission and hull specs.
Propeller companies are using extremely sophysticated software to calculate the size and pitch of a propeller given a boat specs.
The power will only help you to maintain a higher speed while motoring in choppy water or against the wind but the overall efficiency of your engine will be lower.
You also need to consider the consumption. While running your engine at 2500 RPM your consumption will be in the range of 7 L/h and you will reach your max hull speed. Running the engine at 3500 RPM will multiply your consumption by almost two and your speed will remain the same. Which means basically a fuel autonomy divided by two........
What the engine does not like is to be run at the same RPM for hours, which never occur to a car engine. As such to prevent the turbo clogging every three hours you should push your engine to 3000 RPM for around 20 min to eliminate the carbon residues. Eventhough you run your engine at 3500 RPM for hours without changing the RPM sooner or later you may face this turbo clogging problem.
Hope this will answer your questions

With best regards

Erick MEJEAN







----Original Message Follows----
From: "dgoffaux" <dgoffaux@bhkmining.com>
Reply-To: amelyachtowners@yahoogroups.com
To: amelyachtowners@yahoogroups.com
Subject: [Amel Yacht Owners] RPM on Volvo TMD22A, again...!
Date: Wed, 23 Apr 2003 20:50:03 -0000

So happy to have found this site! And to be able to find out how
others have solved various problems (few, actually, in my case) with
their Super Maramu! I purchased SM #135 last year in France (this is a
1995 model) had a good revision on all systems and crossed over to Ft
Lauderdale last December. 17 days from Gran Canary to Guadeloupe,
whithout pushing, the fishing was too good!

One thing I noticed at purchase time was that the engine, in gear,
will not go over 2700 rpm. The Volvo manual indicates a max. speed of
over 4000 rpm for the turbo version. The engine runs nicely, without
smoking and has about 2000 h. now.

The Volvo dealer in Guadeloupe said that they knew about Amel habit to
reduce RPM with the adjustment of the Max prop, a procedure whith
which they totally disagree! They recommend, at next haulout, to
adjust the Max prop as to obtain about 3,400 rpm with the engine in
gear (in neutral there is no problem to rev up).

In France, I also had the turbo dismantled and cleaned, as it was
found full of soot.

So,
1. What is the normal max rpm for the Volvo, as per Amel, and/or as
per Volvo?
2. Presumably, if the pitch of the Max prop is to high, keeping the
engine "labouring", it will induce sooting and will clog the turbo,
especially if indeed it only starts to pump at 2500 rpm or there
about. This may explain why - as I just read on various notes on this
site- one needs to rev up to maximum revolution for a few minutes
every so often. Why not, instead, have the engine running at its
recommended speed?
3. Obviously, I can see why someone recommended to remove the turbo
and clean it every year. This does not seem right however. Nobody does
that on a car or industrial equipment for that matter.

Has anyone any suggestion? Should I leave my engine /Max-Prop as they
are, or should I make some adjustments?

One last question on the transmission: what sort of oil should we use,
it says on it ATF (Automatic Transmission Fluid) but what kind? There
are now 4 different Dextron type fluid oils, does it matter which one?

I would be gratefull if someone could shed some light on those issues.
Good sailing to all.

Daniel Goffaux
On "Passion"





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