V8 300 vs V8 250

[bassmasterffej]

What is the difference? ECU tuning only?

[monkeyfish]

What is the difference? ECU tuning only?

From another thread

http://www.bbcboards.net/showthread.php?t=905138

[EuropeanAM]

May be other differences also... since there are literally dozens of different models for each.

[bassmasterffej]

[XRD]

Was able to sit down with my fishing partner who is a Merc tech today and look over the parts breakdown. Intake and exhaust cams, valves, heads,pistons, and fuel system all show the same part numbers between 200 and 300 in the Pro XS motors. That's all I had time to look at.

[BigBadBass]

So that means simple pcm ecu calibration going to be at play like grand daddy verados of prior?

[bassmasterffej]

[MengRanger]

Still hope for a true 80 Ranger, interesting LOL

[leo13]

In general for a na engine it is difficult to make a 20% gain by just changing the mapping. The R 300xs uses a custom short runner intake manifold compared to 250xs long runner.

What is the difference? ECU tuning only?

[Bamaman]

The composite intake runners for the 300 horsepower are tuned differently--shorter. I would also think the ECU is programmed differently too. It is not just a matter of a reflash on the ECU.

The motors sound incredible.

[RockYScouT]

In general for a na engine it is difficult to make a 20% gain by just changing the mapping. The R 300xs uses a custom short runner intake manifold compared to 250xs long runner.

The Yammis can tune a 200 up to 300hp with only a reflash. There is more to it with veriable cam timing than just spark and fuel. I don't know, I am keeping my fingers crossed!

[engineermike]

These engines are dbw, meaning they simply can use the ecm to prevent the throttle blade from opening all the way on the lower hp models.

[leo13]

No varaible cam timing on the merc.

Changing the air door max position is possible but would function better with a hard stop instead relying on the servo and tps. It has to have a very consistent and accurate position for the life of the engine. Very small changes would have a significant affect on output since it would have a relatively large cross section for the given output.

[Gamblinman]

Good luck breaking the algorithms, and if you do, you can forget your warranty. Think you can pull your tune out and re-install the original without them knowing? Nada...they record every change, and that recording is stored in an inaccessible area...except to Mercury personnel. All the major automotive and marine manufacturers have caught on, and installed preventative measures.

[engineermike]

No varaible cam timing on the merc.

Changing the air door max position is possible but would function better with a hard stop instead relying on the servo and tps. It has to have a very consistent and accurate position for the life of the engine. Very small changes would have a significant affect on output since it would have a relatively large cross section for the given output.

You need a "soft stop" so that it can compensate for ambient conditions. Yes, a 250 might make the same power in the summer as winter. In cars, Pwc's, and most likely outboards, they're not using hard stops. Do some research on torque-demand based ecm's...its fascinating and makes a whole lot of sense, but you have to think of engine operation completely different.

[leo13]

There is no way to calibrate max output on this type of engine therefore IMO a bad idea to use the servo/air door to limit output. Late in life waning of the controls could change output drastically. Inbord & outboard prop drive marine engines run at a constant load, max load for every speed. It is similar to a car continuously driving up a hill. There would be no need to baby sit the air door beyond the TPS to improve economy. Cars especially hybrids are different because they can run from a negative load to max and benefit from load based cross checking.

You need a "soft stop" so that it can compensate for ambient conditions. Yes, a 250 might make the same power in the summer as winter. In cars, Pwc's, and most likely outboards, they're not using hard stops. Do some research on torque-demand based ecm's...its fascinating and makes a whole lot of sense, but you have to think of engine operation completely different.

[engineermike]

There is no way to calibrate max output on this type of engine therefore IMO a bad idea to use the servo/air door to limit output.

Probably way back in the early 2000's, certain marine and powersports engine companies determined/decided that the engine performance characteristics were precise enough from the factory, and consistent enough over the life of the engine that they could meet their goals using only speed-density or n-alpha feed forward control with no air flow measurement or O2 sensor feedback. Ones I know of are the HPDI Yamahas, Sea-Doo PWCs, Yamaha PWCs, numerous street motorcycles, and of course the Verado. They do calculate the output using all the available inputs using the engine model in the PCM. If I am not mistaken, Verado already limits power on the 200-250 L6 using boost bypass to limit boost, which works almost the same way by limiting output via regulated air flow.

Late in life waning of the controls could change output drastically. ..

Some of these systems run a calibration cycle on the throttle body during the tiny delay after you turn the key but before the engine starts.

[EuropeanAM]

Throttle control is digital/electric, just like the Verado was. Tried-and-true... it's PCM controlled, and very precise. Far more so than any mechanical cable and stop could EVER be, since it's compensating constantly based on PCM demands.

[Nova Kaw 650]

These engines are dbw, meaning they simply can use the ecm to prevent the throttle blade from opening all the way on the lower hp models.

[GLOCKMEISTER]

I’m almost positive a “flash” will be available for these new motors. I was told by a reliable source they were flashing them during test trials on lake X. If Mercury makes it where this isn’t an option, but you can still flash the SHO’s... that will be a huge mistake IMHO!!