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-   -   Question for you engine gurus (http://www.wakeworld.com/forum/showthread.php?t=804454)

dreamer 04-23-2015 5:44 AM

Question for you engine gurus
 
I've been testing a few props on my SV244 Enzo and wondering if there is an optimal rpm to wakesurf at. I have the PCM409 and with at least 3000#'s of ballast running at 11.2 mph close to sea level. The rpm's from the different props ranged from 2700 to 3000.

It pops the rider up without cavitation and will easily hold speed at 2700 rpm wakesurfing with the highest pitched prop but I'm wondering if the engine is lugging along or spinning freely enough.

denverd1 04-23-2015 9:58 AM

sounds like its in a good spot. my 230 w 383 runs about 2800 RPM with a couple thousand pounds in it. I wouldn't worry about it.

How do like the motor so far? sounds like a torque monster that sips gas

dreamer 04-23-2015 10:50 AM

Yes, the 409 is a great engine. The 330 Scorpion in my last Enzo had to work way too hard compared to this engine.

rallyart 04-24-2015 7:07 PM

Peak torque on the engine is the ideal speed to run with a heavy load. Your redline is 5600 so your torque peak might be 3200 or higher. 2700 is probably close enough to it that it will be able to run with lots of throttle left so you won't have to worry about lugging it. In any case 2700 is much better than 2400 with that engine.
Peak cruising for that engine is 4000 which means you are past it's maximum efficiency above that. Boats never seem to publish their torque outputs, just HP. You can feel the peak torque range when you are accelerating through it full throttle. The boat will give you it's best 'push' there and not sound like it is tapped out like it does at peak HP.

Short answer is 2700 is fine and bit higher is also fine.

redsupralaunch 04-25-2015 7:16 AM

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Quote:

Originally Posted by rallyart (Post 1909754)
Peak torque on the engine is the ideal speed to run with a heavy load. Your redline is 5600 so your torque peak might be 3200 or higher. 2700 is probably close enough to it that it will be able to run with lots of throttle left so you won't have to worry about lugging it. In any case 2700 is much better than 2400 with that engine.
Peak cruising for that engine is 4000 which means you are past it's maximum efficiency above that. Boats never seem to publish their torque outputs, just HP. You can feel the peak torque range when you are accelerating through it full throttle. The boat will give you it's best 'push' there and not sound like it is tapped out like it does at peak HP.

Short answer is 2700 is fine and bit higher is also fine.

Lets see the 2016 specs. IMO the graph looks like peak torque is at 4000 but the spec sheet reports 400ft/lbs@4400rpm.

The new Ford Raptor sure has the advantage here!

rallyart 04-26-2015 7:16 PM

Good find Chris. If PCM is actually getting the 409 hp then they must have tuned intake and exhaust differently than GM. There won't be any difference in the heads and they run the same RPM. That tuning would be in harmonics that would have raised the high end torque some, or they are just being more creative in their dyno readings to get the Beach Boys number for a cool factor.
In any case higher RPM with a heavy load would give a more controlled throttle. The disadvantage of running a higher RPM is that you are spinning the engine more times and putting more wear on it as a result.

You are right about the numbers on the graph and the specs being slightly different. They probably picked the prettiest graph to print and used there max numbers for the specs. (or maybe I'm just cynical)


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