Turbochargers...enlighten me.

[boatone]

My Dutch steel cruiser has a VP TMD31A lump which has a turbocharger.
As I normally use it on the non tidal Thames, its rare I get over 2000 revs.

Last weekend, however, I tootled off down river to the big city and got up to around 3000revs at times tho' mostly cruising at 7 knots at around 2800rpm. Max revs for the engine is stated as 3800rpm.

So, should I have noticed the turbo kick in and , if so, what would I have been aware of?

 

[[2068]]

The fact that you got to 3000rpms without huge billowing clouds of black smoke, or any strange high pitched whistling noises means that your turbo is working just fine. It'll be whirling aimlessly at lower rpms, then starts to really work at 2000+.

Worth checking that you can actually reach 3800 or thereabouts: if not, you could consider a smaller or finer pitched prop. Or scrub your bottom.

Would be surprised if you noticed any kind of "kick" from a TMD31 attached to a steel cruiser. Unbolt it and mount it in the tender to experience the thrust...

dv.

 

[Divemaster1]

[ QUOTE ]
My Dutch steel cruiser has a VP TMD31A lump which has a turbocharger.

So, should I have noticed the turbo kick in ............

[/ QUOTE ]

Well, in your boat, I do not expect that you would have noticed it "kicking in" .... it would already have been spinning ... and (not knowing your engine admittedly) it probably would already have "kicked in" as a booster of air between 15 - 1900 RPM ... (mine "kicks in" at about 12 - 1300 when under load). The torque curve of the engine would be boosted, but then again, you will be propped to take benefit of this anyway, so probably not really noticable for you. Your turbo does have a water jacket, so you will probably not hear the traditional turbo whine of the good old Fords... ... perhaps if you opened the engine hatch, you would have been aware of a slightly higher pitched noize emitting from the engine's turbocharger, but would not expect that to be very noticable on this engine...

I do hope that you are not disappointed that you did not see the stern digging in, foils emitting from the hull sides and the hull raising out of the water as the speed gradually built up towards the mid 30's... /forums/images/graemlins/smile.gif

 

[tcm]

i think divemaster has hit the nail on the head. ALL thamesy boaters are very keen to go to the "tideway" and tell misty-eyed stories of the incredible feeling of the turbochargers "kicking in". I don't see any problem in doing this regardless of the fact that er it just goes a bit faster. I haven't noticed any "kicking in" effect on other boats either, really.

 

[mainshiptom]

Tony

I have turbos on mine and can just about hear them at over 1000 revs, no real kick but just more fuel intake !

Tom

 

[boatone]

Thanks for the replies.
I was not questioning any particular lack of excitement, only asking what I should expect.With a 20" prop and a 2.6:1 geearbox ratio its difficult to see how there would be any major physical whoopee involved /forums/images/graemlins/grin.gif

I did however wonder if there would be any audible or visible effects ..smoke etc. In the event, a very quiet engine merely seemed a little noisier at the higher revs and there were no smoke issues at all.
Having made a brief trip down below, SWMBO emerged to say 'feels like we are really powering along from down there' which surprised me cos she rarely says anything about engine things.

I must confess that I didnt have the nerve to push up and beyond the 3,000rpm mark....a cautious approach maybe. My boat makes very little wash and I was well able to hold my own with some of the more powerful boats that had to keep their revs down to minmise wash.

As for misty eyed tales of turbos kicking in.....I dont think I fall into that category.....although I must admit driving a Phantom 40 brought a hint of a smile to my face recently /forums/images/graemlins/smile.gif(thank you Peter).

 

[ROCKETSHIP_11]

TRY A SAAB TURBO FOR THE WHOOSH!!! HERE WE GO FEELING!!

 

[Andrew_Fanner]

I do notice some effect at 3000 on my AD41, gaining a knot or so without any real throttle movement.

 

[MedDreamer]

No nosebleed though?

 

[Nauti Fox]

Mrs Boatone feels those turbo's kick!

While Mr Boatone shows her how its done and powers onto the plane.

 

[apollo]

Tony

Would have thought you might have heard the high pitched whistle (a bit like jet plane) even up on the back deck.

Mike

 

[[2068]]

...not unless the turbo bearings are on the way out. On an AD31, it shouldn't be audible.

 

[foxgoose]

I've been puzzled for a while by the completely different power response of Volvo KAD 43's and KAD 32's - both turbo & supercharged.

My Botnia Targa has a single KAD 43 and delivers fairly seamless, relatively quiet power right across the rev and boat speed range, so if sea conditions get a bit hairy I can back off to 15 knots, or even come of the plane to 8 or 9 , and pootle home in relative comfort.

The Ombrine we keep in Malta has twin KAD 32's and their characteristics are totally different.

Over about 1500 revs/7 knots a loud whine starts (which I've been told is the s/chargers kicking in) and persists until about 2500 revs/20 knots after which the turbos kick in and the engines sound healthy.

My local diesel guy there says don't run them in the noisy 1500 -2500 rpm zone 'cos it'll wreck them.

Problem is, the Ombrine is very light and the hull is nothing like as forgiving as the Targa so when a decent chop gets up you've got to battle on at 20 knots and get hammered or come off the plane and get rolled around at displacement speed.

Is this typical of KAD 32's and if so, why are they completely different to the 6 cyl jobs?

 

[[2068]]

>
>My local diesel guy there says don't run them in the noisy 1500 -2500 rpm zone 'cos it'll wreck them.
>

Your local diesel guy is talking rubbish, unless your belts were about to expire anyway.

Not sure why the KAD43 is so much quieter, although it does have a different air intake, and there is only one engine.

You're right that the KAD32 does have a slightly odd torque curve: theres a big lump of torque at about 2000rpm, then it drops off at 2500rpm, then steadies (slight fall) up the rev range until 3500rpm. This makes the KAD32 appear fantastic in boats that are planing by 2000rpms, and a bit of a slug in those that get stuck in the hole at 2500.

Probably the bigger displacement block on the KAD43 is what gets you the more consistent power delivery.

dv.

 

[kimhollamby]

Pedros typically overpropped their boats during the time yours was built - there's a theory that it is a good thing for displacement craft - so although the TMD31 is rated maximum power (100hp) at 3800rpm for one hour in 12 (3600rpm continuous) I doubt yours would reach full revs anyway, unless the prop has been changed or repaired (repitching and repairs on displacement cruisers can have more profound effects on performance than on planing boats).

At 3000rpm you should be making 7.5 knots or so; it'll take most of the rev range and double the diesel burn to do a knot and a bit more.

At 3000rpm the turbo will be providing modest boost; it starts to work properly on this engine from about 2500rpm up, depending upon load.

You tend not to hear the turbos on TMD31s.

It's hardly a must but if you are fascinated by the behaviour of the turbo you can (or certainly could) buy a turbo boost gauge for the TMD 31.

At river speeds the turbo would have been spinning, but not providing any boost as such, other than for very brief spells if the throttle is blipped for manoeuvres.

There are two dangers to craft with these engines and the like on rivers. Bore glazing and turbocharger sooting. You can generally avoid them by getting down the tideway a couple of times a year and loading the engine sufficiently for a decent run.