Interesting call regarding temp vs mph

[Sam]

I called Bronson Hill propellers today to get some information on prop labing. Not only did I get the information I asked for but then some. A fella named Byron informed me that for every 10 degrees up or down it can effect your top end by 1mph. For every 150 lbs in your boat it can effect your top end by 1mph. For every 1000 feet above sea level it can effect your top end by 1mph.

So what do you think ? I am more interested in the temp variation since most of us don't live in the mountains. Surley someone out here has heard of this.

THX
Sam

[Bryan Tuvell 33ZX]

Sam, my old 350 MAG ran a 180, the 502 a 160, there has been several posts by the big motor experts on temp/motor size and requirements, did you do a thread search, I say this because when I had a temp problem last year it came up.
Good luck man, we look forward to seeing you in KY.
Bryan

[Sam]

Sorry Bryan, I missled you regarding the temp, I was talking about the air temp not engine temp.

Sam

[RickR]

Cool dry weather makes a big difference in engine performance. It may also lessen the wind resistance on the hull.

To experiment try running with the hatch off. I usually gain 1mph. Leave "The Boss" on the dock, another mph (plus you don't have the blood running down your leg from her digging in her fingernails, while she is screaming for you to SLOW DOWN wink ).

Elevation makes a big difference also. My local lake is 1000' above sea level and the lake I camp on is 1700'. Genuine Risk runs alot better in Florida.

I feel saltwater improves preformance also, it's more bouyant (sp?).

It's best to jet and adjust idle on your carb for your local lake in normal weather.

[Digger]

I've been dealing with it for years in the helicopter game. higher ambient temp = less power available. In our case we're looking for weight carrying ability (i.e. will we be able to get off the ground) but its the same parameter you want to measure for max speed. Higher altitude makes it worse. We have charts that we look at before every flight to determine no foolin how much power available we'll have.

I would think there would be a chart somewhere for other engines as well besides turboshafts. maybe not. Anyone with a dyno, with the ability to precisely control intake air temp could make one...

[GEOO]

I read that 10 degree drop add's 1% in power.
Forced induction with an intercooler... Water to air intercooler.. (Up north water temp runs 50 in spring to 70 degrees in the summer)...Cools the charge 70 to 100 degrees...
Nitrous can also cool the intake temp. Last summer I recorded one hit of nitrous, intake air temp went from 90 degrees to 50 degrees in 4 seconds.
My engine compartment would get over 100 degrees when I sit still. Once the boat gets moving the temp drops down to ambient temp.
Some motors have raw water fuel coolers. Helps stop vapor lock and cool fuel makes more power.
Nitrous Express makes a kit to spray nitrous on the exterior of an air to air intercooler for cars. The nitrous does not go into the engine it just cools the IC so the intake charge gets colder. GEOO

[Murphy]

This thread is about air temp. etc., but I've been thinking about engine temp. relative to performance lately also. "There is a direct relationship between oil temp/viscosity and performance. High oil weight puts more drag on the distributor shaft and robs the engine of horsepower. It also wears out the distributor bushings faster and can cause eratic timing which also robs horsepower. A high pressure oil pump only makes this worse. Excessive oil pressuree or high viscosity oil(straight 50 weight), or an oil cooler that doesn't allow the oil to come up to at least 220 degrees can be a problem also. The solution is to run stock oil pressures, a 30 or 40 weight oil (in cold water a multi-weight 10w-30) and not overcooling the oil with a larger than necessary oil cooler. The ideal oil temperature should be 220 degrees during normal use, and after a hard run it shouldn't be above 270 degrees. Engine oil temps below 200 degrees are too cold for a warm engine. Engine oil has to come up to operating temperature not only to be circulated by the engine efficiently, but also to evaporate any condensed water. I've seen many engines destroyed by rust buildup on internal components from condensed water that was not evaporated because the oil temperature was too cold. Replacing the oil cooler with a smaller one, or removing it completely may be the solution. Some people believe that high oil pressures and cool oil are necessary for a high performance engine, but in reality, excessive oil pressure and overcooling the oil has a negative effect on horsepower and durability". (Dennis Moore in Small-Block Chevy Marine Performance).
I noticed my sbc was running really cool all last summer and I'm seriously thinking of removing the oil cooler this year to see if that makes a difference. Anybody been this route?

Murph

[Dr. Dan]

No question that you get more grunt (torque) out of cooler denser air, I notice a major difference in the normally aspirated Lightning when I romp on it in the early a.m., it's a bit foggy, the K & N Filter is sucking in all it can!!! eek! And that puppy will snap your head against the back window if you're not ready for it, :p gotta love basic & plane American horsepower(no gimic,no juice,no turbo B.S,just a hoot to drive and it it has 157,000 miles on it), now if I only could make it float? :rolleyes: Hmmmmmm?...Doc

[Sam]

Does synthetic oil run hotter than fosil oil ? I also thought I read somewhere that you may actually gain a few rpm's using synthetics, I don't maybe I was dreaming.

Sam