pondfish
Well-Known Member
Hi all do anybody know at what rpm the turbo kicks in on the above engine
Turbo question on a nanni 200hp
- Thread starter pondfish
- Start date
sailorman
Well-Known Member
Ask Peachments !!!
omega2
Well-Known Member
Unlike your car engine it is spinning from the off, keep your fingers away from it.
bluejasper2
Well-Known Member
hi pondfish, i think turbo kicks in about 2400 -2500rpm my mates boat benateau 7.
Latestarter1
Well-Known Member
I do not buy any of this............
Here we go again 'Propellers move boats engines merely turn them' responding to the load placed upon them this is basic stuff.
The manufacturers data sheet can ONLY give one boost number which is at 100% load and rated engine speed.
Your boost curve follows a specific vessels propeller demand curve, you will be getting boost albeit low levels from just above idle it does not 'kick in'.
The power surge being felt is engine passing peak torque and boost levels will be rising more steeply due to shape of prop demand curve, the real one not the calculated one off the manufacturers spec sheet.
Here we go again 'Propellers move boats engines merely turn them' responding to the load placed upon them this is basic stuff.
The manufacturers data sheet can ONLY give one boost number which is at 100% load and rated engine speed.
Your boost curve follows a specific vessels propeller demand curve, you will be getting boost albeit low levels from just above idle it does not 'kick in'.
The power surge being felt is engine passing peak torque and boost levels will be rising more steeply due to shape of prop demand curve, the real one not the calculated one off the manufacturers spec sheet.
pondfish
Well-Known Member
Ok thanks let me put it another way have any body got an Antares 760 with a nanni 200hp if so what do you find is the boat/engine sweet spot getting best boost from turbo but not drinking the fuel
omega2
Well-Known Member
Nearly every manufacturer reckons 200 rpm below maxrevs, i.e with an ancient Ford (dorset) Sabre 180, "they" say max output at 2450 rpm, and 2250 should be the most "efficient" speed. We run at a speed that is comfortable and are still able to make the tea!!
Latestarter1
Well-Known Member
Please just do me the favor of downloading your engine data sheet from the website and peruse it along with my previous comments.
No clue why you are boost obsessed, as I explained your boost curve will simply follow your propeller demand curve.
If you look at the fuel consumption curve you will see that it also follows the propeller demand curve which in this case is an arbitrary 2.5 exponent, which may be reasonably close to your actual propeller demand curve which could be between 2.4 and 2.7 dependent on your hull shape.
Now take a look at your torque curve, best point on the fuel curve will be around peak torque, in reality sitting just above peak torque will be the sweetest spot so around 2,400 looks pretty reasonable me.
Your engine is a light duty automotive engine unlike Omega2 who has mid range engines and he is correct regarding running 200rpm 'off the top' for his continuous operation. In your case LDA engines need to be run at 400 rpm off the top for continuous operation.
Based on the above your operational engine speed range 'window' will be between 2,500 and 3,000 rpm.
Good luck
pondfish
Well-Known Member
Thanks for the info,
Why you should think i'm boost obsessed I don't know,
It was two simple questions I thought (1) At what rpm does the turbo kick in, (2) what do you find is the sweet spot to run the above engine,
Because I would not like to labour the engine and also not let the engine drink the fuel away for just a few knots more,
But as I said thanks for the replys
Why you should think i'm boost obsessed I don't know,
It was two simple questions I thought (1) At what rpm does the turbo kick in, (2) what do you find is the sweet spot to run the above engine,
Because I would not like to labour the engine and also not let the engine drink the fuel away for just a few knots more,
But as I said thanks for the replys
GDPR150987
...
Im curious about the meaning of an LDA motor. Is this term used on motors that have reduced longevity compared to say industrial CATs etc?
I believe the Nanni diesel in question is based on a Toyota automotive base in which case some Land Cruisers have over 250k miles on the clock having experienced varying RPMs and loads throughout their lives which I would have assumed being more detrimental to longevity than say a marine motor sat at mainly low'ish cruising RPMs.
I guess what Im trying to ask, Latestarter, is your expert opinion on wheather this term LDA means they wont last as long as say Omega2's mid range engine (although I'd admit I have no idea what his engine is)
Appreciate your help.
Latestarter1
Well-Known Member
Apologies LDA (Light Duty Automotive) characterised by by engines originally designed for cars and light vans.
Omega's Ford Dorset motors were originally for the Ford D Series truck which grossed at between 6 and 16 tonnes.
Properly applied all engines whatever class should never be subject to wear out in leisure applications, however there is not much meat on the bone once you start abusing them.
With modern materials piston speed is no longer a measure of durability, for example CAT C18 tends to set the bar for piston speed, nobody would question C18 durability/ reliability.
One has to remember that energy is heat, when you produce high specific power from a small displacement and there is not much meat on the bone, a small problem can become catastrophic very quickly.
GDPR150987
...
Latestarter, I understand now thanks very much :encouragement:
Skylark
Well-Known Member
Turbochargers do not "kick in". They are high speed rotational devices and are inherently mismatched for use on reciprocating ic engines. Turbo manufactures, I worked for one for 19 years, work hard to refine the compressed air / boost delivery characteristics to match the air consumption requirements of the combustion process.
They have two stages; compressor and turbine. The compressor stage can not supply low flows at high pressure, it will "surge" and become unstable. Likewise it can not keep supplying air at higher flows, it become "choked". The aim is to match engine air flow needs without surge and without choke. Lots of design variables here. Blade design, clearances, backward curvatures, diameter, trim, housing a/r and so on.
The turbine harnesses exhaust gas energy to spin the compressor stage. Simple energy balance, remember from school boy physics; mass x Cp (specific heat of the gas) x temperature drop across the turbine. Exhaust gas flow is directed over the radial inflow turbine by a funnel (it's a scroll but funnel is easier to grasp). Imagine a funnel with a large exit diameter. Now one with a small exit diameter. The one with the smaller diameter will spin the turbine sooner for the same mass flow. At higher flows, it will become chocked and no more gas will pass through the turbine. The larger funnel wouldn't be much use at lower mass flows but works a treat at higher flows.
Diesel engines are, generally, categorised as low, medium or high speed. Car diesels are high speed, truck are medium. A truck engine operates between, say, 900 to 1800 rpm. Many years ago, a turbine housing (the funnel) could be chosen to harness the exhaust gas energy and drive the compressor. So called fixed geometry.
Car diesel engines run from, say, 1000 to 4000 rpm. A fixed geometry turbo can not match this need. Enter the "waste gate" of the 1980s. The turbine stage "funnel" is quite small to provide low speed boost. At higher flows, a simple valve opens in the turbine housing to bypass excess gas around the turbine stage. Effectively, a turbine speed controlling device.
Today, the crude waste gate has been largely replaced by variable geometry. Vanes move within the gas flow to direct more or less gas over the blades. Given that exhaust gas temperature can be around 800 degrees centigrade, the materials technology, at automotive costs, was quite a challenge to achieve this.
Sensing and electrickery has a key role these days, too.
Cast your mind back to the wonderful Saab 99 EMS Turbo. Compared to today, it had a very large, heavy turbo. On a modern passenger car, the turbo can accelerate at something like 100,000 rpm per second. Put your foot on the throttle and a couple of seconds later the turbo will be spinning at approaching 200,000 rpm.
A combination of big and heavy, inefficient large compressor and turbine wheels and a poor match to the engine........it "kicked in". It was taking its time to accelerate.
Hope this is helpful.
They have two stages; compressor and turbine. The compressor stage can not supply low flows at high pressure, it will "surge" and become unstable. Likewise it can not keep supplying air at higher flows, it become "choked". The aim is to match engine air flow needs without surge and without choke. Lots of design variables here. Blade design, clearances, backward curvatures, diameter, trim, housing a/r and so on.
The turbine harnesses exhaust gas energy to spin the compressor stage. Simple energy balance, remember from school boy physics; mass x Cp (specific heat of the gas) x temperature drop across the turbine. Exhaust gas flow is directed over the radial inflow turbine by a funnel (it's a scroll but funnel is easier to grasp). Imagine a funnel with a large exit diameter. Now one with a small exit diameter. The one with the smaller diameter will spin the turbine sooner for the same mass flow. At higher flows, it will become chocked and no more gas will pass through the turbine. The larger funnel wouldn't be much use at lower mass flows but works a treat at higher flows.
Diesel engines are, generally, categorised as low, medium or high speed. Car diesels are high speed, truck are medium. A truck engine operates between, say, 900 to 1800 rpm. Many years ago, a turbine housing (the funnel) could be chosen to harness the exhaust gas energy and drive the compressor. So called fixed geometry.
Car diesel engines run from, say, 1000 to 4000 rpm. A fixed geometry turbo can not match this need. Enter the "waste gate" of the 1980s. The turbine stage "funnel" is quite small to provide low speed boost. At higher flows, a simple valve opens in the turbine housing to bypass excess gas around the turbine stage. Effectively, a turbine speed controlling device.
Today, the crude waste gate has been largely replaced by variable geometry. Vanes move within the gas flow to direct more or less gas over the blades. Given that exhaust gas temperature can be around 800 degrees centigrade, the materials technology, at automotive costs, was quite a challenge to achieve this.
Sensing and electrickery has a key role these days, too.
Cast your mind back to the wonderful Saab 99 EMS Turbo. Compared to today, it had a very large, heavy turbo. On a modern passenger car, the turbo can accelerate at something like 100,000 rpm per second. Put your foot on the throttle and a couple of seconds later the turbo will be spinning at approaching 200,000 rpm.
A combination of big and heavy, inefficient large compressor and turbine wheels and a poor match to the engine........it "kicked in". It was taking its time to accelerate.
Hope this is helpful.
Latestarter1
Well-Known Member
Thank you David