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Hot-rodded engines - Do they really work?

Bill Rusk

BENEFACTOR
Sandpoint, Idaho
Question

Do the hot-rodded engines really put out more power to the prop? I have about come to the conclusion that you can spout all the dyno numbers all you want but if that Hp can not be translated into power at the prop it is pretty well wasted. Will the hot-rodded motor spin the same prop faster? Will it spin more pitch the same RPM? Has anyone compared a new standard 0-360 (or 0-320) to a 0-375 or hot-rodded 0-360 with a pull test? I know we have compared props.
I would like to see a standard, say less than 100 hrs 0-360 engine, same exhaust system pull test with a given prop. Now, take that same prop off and put it on a hot-rodded motor, same exhaust, and do the same pull test.
We have slowly developed some pretty good prop numbers. I am interested in the engine numbers.
Perhaps guys like Peppard, Mike, Crash, Calkins have done this and I have missed it. No speculation please, just the facts. Is anyone in a position to do this? You have a standard motor and your hangar mate has a hot-rodded motor so you could swap props with a pull test? Obviously we would need to limit the variables as much as possible. Not fair to compare a worn out motor to a new one, with different exhaust, etc.

Are the hot-rodded motors really worth it and are they really getting more Hp to the prop?

Bill
 
I know that if you take out 11:1 pistons and put in 10.5:1 pistons on an IO-360 that dyno'ed at........

Okay, let me rephrase this:

IO-360 with 11 to 1......turns a 90x37 prop at over 2350 RPM static.
Same engine with 10.5 to 1 pistons turns the same prop at about 2150 RPM static.

The prop was changed to an 84 x 45 which is a very good compromise for this a/c and engine.

This engine on 11 to 1 burned over 19 gph full throttle........BUT it pulled harder than any hotrod Cub I've been around and turned it's 90x37 at higher rpm than a known test of an O-375 on nitrous turning the same prop but pitched to 35......in ohter words.........the IO360 on 11 to 1 made more torque than a nitrous O-375.

opinion........my opinion is that hotrodding works, it works very well, and it is very addictive to have that much power. I just wanna do it over and over and over again.

PS, you hotrod, you gotta do your best at engine baffling and cowling optimization to get the heat out. I have seen guys screw this up, and blame everything else, when they're used to 150 Cub stuff that works fine.
 
PS, if you're happy with 150 horse, be happy. You're still having fun and can go and do aLOT of stuff. You don't need 220 HP. Go flying!!!
 
Stock O-320/360 parts are easy to get. If something goes wrong with a hot rod engine it usually has to come off the airplane FWF and go back to the builder, not always but sometimes. Your adding horsepower already in your quest to build the lightest cub for your needs.
 
I have had conversations with guys that have taken an 0-320 from an honest 160-170-180 hp in increments and each time the borer prop needed to have more pitch added to it to keep the rpm's in the sweet spot. What started as a 82-41 ended up a -46. The RPM stayed the same but the thrust increased and the climb rate went up as the take off shortened. Basically you can make an 0-320 with a borer pull better than a stock 0-360. It seems like the borer prop works quite well with more pitch you just need some power to spin it up.

What is the most efficient way to make more at altitude? displacement or compression ratio? displacement = weight so that works against you when dealing with wing loading. Can a smaller engine with a lighter prop and higher compression ratio make the same thrust at altitude as a larger engine with lower compression and heavy prop? What is the difference in fuel consumption?

I think the idea should be what is the best prop to use for the intended mission, then find the power to make that prop work best.

Take a strong stock O-360 and put your favorite Cato prop on it. Then find the combination of parts needed in an O-320 to spin that same prop the same RPM. Hopefully you can do that with a 30lb weight savings. I would try to do testing at different RPM settings from 2100 to 2700 rpm. Just an idea .....

I think I remember hearing that the CC 0-340 180hp carbon cub engine/Prop makes more thrust that a top cub 0-360 with the Mac- Club prop. that could just be a rumor or hangar talk though.

Jason
 
Increasing Engine Power

There are basically 4 things you can do to increase power, and they all work to a point. 1) You can increase the amount of air flowing into the engine by using cold air induction, porting the cylinder heads (Aero Sport, Lycon, and others routinely do this) and using tuned exhaust such as Power Flow, or turbocharging. 2) You can increase the compression ratio using high compression pistons. 3) You can increase displacement by stroking a smaller engine (eg. 320 to 340 with ECi crankshaft, 360 to 375 with Aero Sport crankshaft, or 360 to 408 with Superior engine), or you can just buy a larger engine from Lycoming. 4) Lastly you can increase RPM, but this isn’t really an option when you are running a 90” prop. All of these are proven to increase horsepower, and all of them will lose power at the rate of 3% per 1000 feet above sea level. Only turbocharging can sustain horsepower at altitude.

Of course, all of this is for experimentals only, except buying a larger certified engine, assuming an STC is available.

As mentioned by others the problem with these mods is getting rid of heat. If you have the same surface area of cooling fins on an engine but increase power, you are going to have to work much harder to keep cylinder head and oil temperatures in line on hot days. Also the more you increase power the more likely you are to shorten the life of your engine. There is no free lunch here.

Dave Prizio
 
I have a 0-320 ,160hp in my exp. cub with a 74/56 prop for break in. Next summer i will put a borer 82/41 for float flying( maybe to fine for a 160hp) . My question is : what is the best static and climb RPM should i look for best power(thrust)?

frenchy
 
PS. Some guys don't want to mention what they got.....and some guys who are experimental don't wanna mention what they got. I heard of a very powerful -320, wonder if he'll chime in. It's experimental.

but.....it won't pull like that IO-360 on 11 to 1. Nothing I've been around does.

I haven't been around the turbo'ed 4 cyl. Lycomings. What is happening with those??

Frenchy.....seems like everyone likes to see between 2350 and 2500 static. With fixed pitch its a compromise and you need to decide whether you'd rather have supreme out of the hole performance or compromise more toward cruise performance.
 
Dave Calkins started off with an IO-360 with 11:1 pistons, that's pretty hard to beat so maybe that's the reason there are so few replies!

More down market:
Cub No. 1: O-320-A2B, stock, certified Cub, 74DM6-52 prop: 2500 rpm static.
Cub No. 2: O-320-A2B, stock engine but I had the engine shop flow balance the cylinders (polish the ports), certified Cub, exact same 74-DM6-52 prop, not been touched since No. 1 Cub, exact same prop: 2550 rpm static.

I have found the flow balanced engine will run way with the RPM when pushed at full throttle. When playing around it will go red line+. Never experienced this before. Flying around normally at 21"-23" it seems no different than #1 Cub.

This is also one of the smoothest O-320-A2B's I've flown behind, so I'm sold on flow-balancing.

Cheers,
Andrew.
 
Well after many hours searching SC.org I have found a few #'s. First, it is pretty interesting in the searches how quickly the data availability changes. If you go back to 2005 almost all the prop discussions center around the 0-320. Hot-rod engines, 0-360's, composite props, 90" props, nitro, and the like, has really exploded in the last 7 years. Pretty cool to see the change we have been a part of.

As best I can tell the standard 0-360 will spin a Catto 84-42 at 2450 RPM
A hot-rodded 0-375 with 9.6 pistons will spin a Catto 84-44 at 2450 RPM

This statement is just me trying to interpolate and interpret wildly divergent posts on this site, but it is the best I can pull together at this time. Unfortunately the sample size is limited which in turn limits the validity of the data. Is it the hot-rodding, or just the higher compression ratio, that accounts for the difference? It also looks like that difference will result in about 50 pounds on a pull test. Interesting stuff.

Bill
 
Well of course hotrodding is a GoodThing.
I was out checking RPM/IAS the other day as a result of a question from a bud. It was -10C so the air was a bit "thick" for RPMs, but good for engine performance. This is on skis, with my "Bart massaged" 0320.

Checked my speeds/RPMs w/the 41” Borer: (about -10-12* today)
2200 RPM 85 MPH indicated

2300 90

2400 95

2500 100

2600 105

2700 110

2800 115
 
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I would spend money on a well balanced engine long before any money towards hot rodding. If you have never flown behind a balanced engine, you owe it to yourself.
 
If the final choice tends to run at the high end of the temperature spectrum you will need to be careful at altitude. If you are still able to pull high power at altitude, which is your stated reason for this, you will find that the cooling is directly related to the indicated airspeed. If you loose indicated speed due to altitude effects you will loose the amount of cooling ram air that is required for the desired result. This may require reducing power to stay cool which will defeat your purpose.

Seems to me that you should use the largest displacement which is available without over souping so that the engine will still produce power at altitude without producing excess heat. Lets face it, a Cub does not produce a lot of ram cooling air. Particularly when loaded at altitude.
 
Logan - ???

Jason - I don't remember any pull tests with a CC 0-340 but I'll bet you a steak dinner that it will not out pull a normal 0-360 with a Catto prop. Both engines getting 2450 static. That would begin to get to the heart of this whole post. Does it all work or is it mostly hype?

Lets do a massive pull test at JC. One after another, hook em up, write down what engine, prop, exhaust. Pull. Hook up the next guy and repeat. I'll bet you could do 50 pulls in about 2 hrs if it was set up right. That would be most interesting.


Pete

Excellent point as well. I am really trying to get past all the hype and see if it really works or are we spending a lot of time and money for little significant gain. Obviously, each person will have to decide if it is worth it to them. I am just trying as best I can to determine exactly what it is we are gaining. Looks to me, at this point, like about 2 inches of prop pitch or about 100 RPM.....maybe. Then the next question is ....does that performance gain last for 2000 hrs or is it pretty much gone after 100, 200, 300 hours? It does seem that the performance engines run smoother and there is value in that.

Bill
 
To throw a little fuel on the fire here. If you used ethanol for the fuel for your "hotrod", it would bring temperatures down, have more power at higher altitudes since the fuel is 1/3 oxygen, and you could maybe raise the compression ratio up to 13 to 1 instead of a measly 11 to 1.:lol: Might have to rig up a compression release to get the starter to turn the engine over though.
 
"Lets do a massive pull test at JC. One after another, hook em up, write down what engine, prop, exhaust. Pull. Hook up the next guy and repeat. I'll bet you could do 50 pulls in about 2 hrs if it was set up right. That would be most interesting."

Great idea. This would be pretty entertaining and informative. I'd even like to hook my -11 with 85 stroker and get some numbers.
 
I would be happy to spearhead The Great Johnson Creek 2012 Pull Test if there is any interest. We will pull anyone and everyone.

Bill
 
..what's "Johnson Creek"?:)

someone woke up ready to stir the pot
stir.gif
 
FWIW

i put a new Lycon engine in my 18 in June--port and polished, 8.5 to 1, 82-42--at factory it got 177hp

did a pull test with a fellow at palmer end of July who has an 18, 160hp, 10:1, and think his prop is 82-41

results were exactly the same--they both pulled somewhere in the mid 600's--

again, FWIW
 
I have 0-375 Bart motor not one person thats flown it said it performs like a stock 0-360!! I have 980'hrs on it , lots of mods nitrous high lift rocker ratio electrictronic fuel injection high energy ignition system ect ect. Cruise RPM 2500' depending on altitude 6.5-7 gph fuel burn mikeo
 
I say lets do it at Landmark (0U0) which is a few miles south of JC and at an alt of 6662' There will be no traffic to deal with and no one around there to complain about the noise. Much safer environment at a higher elevation. If you're lucky you'll get some additional DALT as the day heats up if it's better weather than last year.


Jason
 
I have 0-375 Bart motor not one person thats flown it said it performs like a stock 0-360!! I have 980'hrs on it , lots of mods nitrous high lift rocker ratio electrictronic fuel injection high energy ignition system ect ect. Cruise RPM 2500' depending on altitude 6.5-7 gph fuel burn mikeo

Mike's airplane looks like it will literally hover when pulled up into a vertical line at a safe altitude. ....and that's without the happy button.....and that's with the prop that performed the lowliest against the other hotrods and props of the same day's static pulls.

Which brings up the points:
1. Will your O-360 PA-18 hover?
2. Is static prop testing a really worthwhile measure of performance?

...questions:nutz:
 
Hate to keep reminding, high compression = no mogas

Love the JC pull test plan! Count me in
 
Bill are you getting nervous about drag racing in Alaska?

The right prop will harness the extra power.
 
Hot rodded engines definitely work and to think otherwise would be like thinking that 8.50 tires would work as well as 35's as long as you're careful. My 0-320 with 10:1 lycon pistons (no port or polish) spun an 8244 Borer with more rpm that the 7.5:1 spun the 8242. That translated into faster cruise, less gas/hr. and way, way better performance! The Catto propellers are even more amazing in what they can do. Static pull tests are step 1 and show interesting trends but they are not the final word. Catto's new chord design pulled about the same static but climbs harder, cruises faster and cools the engine better as tested on Josh's Producer (0-375) when in flight. Now we are talking props & engines- sorry but like 5-Rivers said, they go together. Use the same prop for all engines @ JC and we will get another round of interesting results. Good luck, Bill-I love this forum!
 
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