engine hp - Page 2

Max... · 02 May 2015, 09:46

Ahhh I see - what's GDI?

Roflhat · 02 May 2015, 10:15

you could fit even small outboards with fuel injection and programmable CDI ignition. A guy in the states even fitted a massive turbocharger to his tohatsu 50, think he was getting over 100bhp from it.

Yamaha have a port map for their 2 stroke 3-cyl 90 that brings it up to 120bhp, but leads to a higher stressed engine. They sold the port map to Hydrotec (I think?) so if anyone wants a 120hp yamaha which weighs the same as the 90...

Wazzajnr · 02 May 2015, 21:31

Hmmmm, interesting comments. Yes I get that the engines need to last better and be more reliable.
Not convinced on the gearing argument because what you have with a prop is basically a crude torque converter. I doubt I'll be able to do much with mine using off the shelf stuff as its a cheapo Chinese motor.
As far as not using bike engines at full power for most of the time, I can assure you that when I rode my 50cc it was WOT pretty much all the time. You needed WOT to hold 50mph and I was using it for journeys that were almost completely on dual carriageways.
I think the comment about the tuned exhaust holds most water as they make a huge difference on 2 stroke motors.
My 3.5cc model car motor made 0.4hp with stock exhaust, with the racing exhaust it made 2.7hp at 32,000rpm.
Might have a go at cleaning up the ports etc on mine. Not bothered too much if I kill it, it was only 250 quid brand new.
Still think that with today's tech, we should be able to make more from the cc they are.
Also, why did the eu ban 2 stroke boat motors but still allow bike motors to be 2 stroke? Surely the emissions from the millions of bikes sold as 2 strokes every year are far greater than the shall number of boats that use them.

On that note, having bought a brand new 2 stroke, who would be the one who could prosecute me for using it? As it is, the boat and motor were bought by my limited company so could I claim that it was bought for taking customers on pleasure trips and therefore is commercial use?
Stupid rule anyway unless they're going to ban use of existing motors.

apshutt · 02 May 2015, 23:12

The "commercial use" law I think only applies to companies involved in Marine activities eg Marine biologists and fisheries and not for trips with customers! I think!

Poly · 03 May 2015, 01:08

Wazza - will these alleged commercial trips be on a vessel which has been MCA coded? The law is (mostly) quite clear on what is and is not a pleasure vessel or a pleasure trip, and simply ownership by a limited company is not enough.

Roflhat · 03 May 2015, 08:53

If you can get more hp from an outboard without reducing reliability or longetivety I think outboard manufacturers will be queuing up for you, it's easier said than done, unless you spend a small fortune on it.

It makes sense to stop selling 2 strokes as their emmisions are worse, and it's fairly easy to do, whereas going all around the UK trying to find all existing 2 strokes would be impossible...

bmb779 · 03 May 2015, 10:01

They would be queuing up to stop you,imagine what that would do to their sales.

Last Tango · 06 May 2015, 09:28

Quote:

Originally Posted by Max...

Ahhh I see - what's GDI?

I think (and I might be shot down in flames) that Mitsubishi were the first to use the system they termed "Gasoline Direct Injection" basically injecting the fuel directly into the cylinder in a similar fashion to a diesel engine. The principal being that the 18:1 air/fuel mass ratio on idle could be pushed without causing pre-ignition. (in their case pushed to 44:1) if there was no fuel in the cylinder to pre-ignite. (injection was on or after TDC advancing with revs and load) The theory was good and it produced very low emissions on idle and good economy.....unfortunately, only if the vehicle was very lightly driven. Once it's "given a bit of stick" the economy goes out the window.

Apply the same principal on a two-stroke and the fuel isn't introduced until after the exhaust port has been covered so their inherent inefficiency caused by half the fuel charge going out the exhaust is resolved. But the hardware is not cheep and it's management system is going to require power eg 12v battery.
Justifiable on an engine costing thousands but not on one costing hundreds.

Last Tango · 06 May 2015, 09:44

Quote:

Originally Posted by Wazzajnr

Not convinced on the gearing argument because what you have with a prop is basically a crude torque converter. .................................................. ............................
On that note, having bought a brand new 2 stroke, who would be the one who could prosecute me for using it?

A "very crude" torque converter. It's a bit like saying being able to spin your wheels means that your tyres are a crude torque converter. Propellers are designed (in the main) not to slip and you might be surprised how good they are at that. Sit a propeller in three feet of water and try to lift it out without it turning!

Re the two stroke, I'm not sure if it's you or just the seller that has commited the offence.

Last Tango · 06 May 2015, 10:09

Quote:

Originally Posted by Poly

Wazza - will these alleged commercial trips be on a vessel which has been MCA coded? The law is (mostly) quite clear on what is and is not a pleasure vessel or a pleasure trip, and simply ownership by a limited company is not enough.

Just to stir it up...........if the the vessel is used in Cat C or D waters it may not need to be coded