Brain Teaser

[hiddenhearth]

I am still trying to get some answers to some power chart questions for the 0-360. Here's the question.

Lets say a stock O-360 (8.5 pistons) running at cruise and 24/2400 is producing 150 HP. Now take the same engine and put 9.2 pistions in it and electronic ignition. We dyno the engine and find out that the max HP has been boosted from 180 to 194 HP. Now take the modified engine back to the same exact conditions as the first example and set the power to the original 24/2400. Will the modified engine make more HP at the same settings or do you need to raise the MP to achieve the increased HP that the engine is capable of producing?

No one word answers please!

[Ironflight]

...but I'm sitting in a hotel room a thousand miles from home, and don't have my engine manual with me. But if I did, I'd simply compare the power settings you ask for the 180 HP O-360 and the 200 HP O-360 models (sorry, can't be more specific on dash-numbers), and see what they say.

I have a guess, but I won't make a fool of myself.

(caveat....while I am supposed to be an aeronautical enginer (and I even play one on TV sometimes!), I didn't specialize in propulsion systems....I always figure the gear-heads would bring the right ones.... )

Paul

[13brv3]

I'd say it will certainly be making more power.

You've assumed (we know) that max power is higher for the 9.2 pistons, and wouldn't both engines have ideally been at 30/2700 during that test? If the high compression pistons are higher at that particular condition, why wouldn't they be higher at 24/2400?

My understanding is that the high compression pistons make more efficient use of the fuel air mix, but hey, I fix MRI scanners, so what do I know

[Mel]

The power curve for the 180 hp engine will not relate to your engine. It should be producing more power, but how much is a guess. You have changed the entire power curve by changing compression. You now have a totally different engine. Your power curve will also be totally different.
Mel...DAR

[RatMan]

Originally Posted by Ironflight

(caveat....while I am supposed to be an aeronautical enginer (and I even play one on TV sometimes!), I didn't specialize in propulsion systems....I always figure the gear-heads would bring the right ones.... )

Paul

But are you staying in a Holiday Inn Express Paul? Maybe that would help

Rat

[Allen Barrett]

Don't forget, EI systems have timing maps that are relative to the equation. where is the engine timing of the 9.2:1 with EI?

Allen Barrett

[Mike S]

My guess---------more hp, but due to the electronic ign. more than to the compression.

That assumes, of course, that the ign. has timing advance capabilities.

In my experiance, which is automotove, comp change usually doesnt mean a whole lot in itself, it is only one compnet of a total system. Higher comp will give more hp, usually, but can sometimes give less power if the rest of the engine dosent support it-------detonation being a prime example.

One of the main reasons to increase come ratio-----------again I am talking from an automotive background, is to compensate for cam changes. The objective is to maintain optimum cylinder pressure at the compression stage, and a long overlap cam will drastically reduce that so a comp increase is needed.

Same reason you REDUCE the comp ratio when supercharging--------cylinder pressure is the driving force here also.

Then you throw in timing factors, and watch the cylinder pressure issue really go nuts-----------------

Mike