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Bob Axsom

Well Known Member
I have a few more little benefit drag reduction ideas to work on for next year's racing season but I'm getting down to the "slim pickin's" part of that bag of tricks and I have already bought a BA C/S Hartzell with F7496 blades to pick up speed from thrust improvements. I am a little frontally challenged in my RV-6A against the very slick RV-8s and I have to look at the "more power" options to reel them back in. At a high level, what are the options?

Bob Axsom
 
When all else fails...

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Going with the flow...

n5lp said:
What Ernie says! Ok, Ernie, how many times did you guys blow up engines with that stuff?
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Well... quite a few. Nitrous is actually very predictable and easy to manage when the atmosphere is reasonably constant, but when you're racing to 40+ thousand feet the conditions are changing so rapidly it's almost impossible to manage. The use of Nitrous does however have some side effects on the male species... testosterone levels have been known to go off the chart. When you press the button...well, you remember what it feels like to be 20 again and in some small way, that experience makes the necessity of building another engine a bit more palatable.
 
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So Ernie....we need to talk about where you're going to put the Nitrous tank in the -3....:)
 
Bob Axsom said:
At a high level, what are the options?

Bob Axsom
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Without going inside the engine (i.e. cam, compression, stroke, etc), the same as any racing engine - exhaust and intake tuning, ignition, and induction system that gives you the best MP. Wrapped exhaust (or ceramic coated) is good for power, as is keeping the induction temperatures down (dense).
 
Without going inside the engine???

HP increase is a pretty simple thing, follow the concept of getting more air in and out. Also, getting the timing to produce max cylinder pressure at the correct point of piston travel.

Ram air is an easy one.

Smoothing out all the internal passages in the intake system is a good one too-----I had a mismatched step in the elbow for my system, that was an easy 1/8" ---bit of work with a Dremel and it was gone. Matching the ports to the gaskets is an old hot rod trick, google it.

Keeping the intake charge dense as possible is free power, insulated intake tubes and ceramic coated exhaust will help. Directing heated cooling air away from the intake tubes. Cold air sump-----WARNING, if you run a carb, this is a formula for possible icing.

Ram tuning of the intake and exhaust.

Anti reversion cones in the exhaust may help---google this one too.

Good solid ignition and timing is vital to max power. Multiple spark is good.
 
Does anyone make a cold air replacement sump for a Vertical intake? When I switched from carb to FI that thought definately crossed my mind.
 
Toobuilder said:
Without going inside the engine (i.e. cam, compression, stroke, etc), the same as any racing engine - exhaust and intake tuning, ignition, and induction system that gives you the best MP. Wrapped exhaust (or ceramic coated) is good for power, as is keeping the induction temperatures down (dense).
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OK, I'll bite here. Aside from reducing heat transfer to the intake plumbing (and allowing a slightly denser charge) how does ceramic coating increase power?
 
short answer,

Keeps heat inside the exhaust pipe, thus gases are expanded to a greater volume, thus velocity in the pipe is higher.

Gas velocity can be used to scavenge the cylinder of spent combustion gases, and if there is enough valve overlap, suck in fresh combustion charge. Our Lycosarus engines probably dont have the needed overlap for this to come into play.

Of course, the correct design of the exhaust system comes into play here also.
 
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Forced Induction

Time for a Turbo Bob. You could just normalize it and it would still make a big difference.

Hans:D
 
The horsepower of an internal combusion engine is:
HP=PLAN/33,000
where
P=brake mean effective pressure
L=length of stroke (FT)
A=area of piston (in^2)
N=number of power strokes per minute

So to increase the power of the engine, you can increase some or all of the above.
P can be increased by supercharging or turbosupercharging, having an oxygen rich fuel like methanol/ethanol or and addition like nitrous oxide, all of which require more fuel to be burned with the additional oxygen. A small effect is to use a tuned exhaust system that will extract more of the spent charge from the combusion chamber. Likewise a small effect is to use ram air pressure on the induction side.

L can be increased with a stroker crank
A can be increased with larger bore pistons
N can be increased by turning the engine faster. In the case of an aircraft engine, the propeller has to be changed to allow the engine to turn faster

Very simple, none of them cheap.
 
N and P

Unfortunatly increasing "N" doesn't always mean more power. It usually leads to a reduction in "P" by the lowered manifold pressure. I have no idea what RPM a Lycoming creates it's maximum power, but I am guessing it isn't too far from 2700rpm. That's just the way the cam was designed.

Unless, of course, you increase the "N" by adding more cylinders.:D
 
Dave says GET MORE "N" so contact the FAA and get a bigger N Number!! :D
Actually, follow the simple rule:
SUCK- optimize intake flow, reduce restriction, cool the charge, ram air,
SQUEEZE-increase compression for more combustion pressure & less retained exhaust
BANG-Optimize timing, electronic ignition system?
BLOW-enhance exhaust blowdown, prevent reversion, optimize scavenging see CAFE exhaust system tests. Exhaust jet thrust, see Kent Paser's Speed with Economy.
Any increase in one of the above has limited effect if there is a limiting problem with one of the others. For example, increased intake air and fuel flow gives limited power gain if the exhaust system is restricted.
If you run at excess RPM, consult the horsepower / torque chart for your engine to estimate benefits, consider liabilities like prop RPM limits and harmonic ballance issues.
 
speed

I was told years ago that after all the engine and other tricks had been done, that Tracy Saylor and Dave Anders both had their hartzell blades reworked and got a big jump in performance. I met Tracy years ago so the info may have come directly from him. There are probably just a few prop shops willing to do this. From a safety standpoint you are way out on a limb with mods to metal blade props.
The parallel valve Lyc will survive 1000 hours at 3300-3500 rpm. The angle valve doesn't last as long. For a long distance race I feel a fixed pitch turning 3000-3300 r/m is optimal with the four cylinder engines. Some of the British racers and early generation fighters went very fast with fixed pitch props. In the late 30's Steve Wittman was going 325 with a ground adjustable prop with metal blades with a little over 450 horsepower. Some others were using two to three times the horsepower to go the same speed. I believe Roscoe Turners Laird Meteor was in the 1200 hp range. Very few of the thirties racers had retract gear. Todays Super Sport racers are topping around 400 with around the same power as the 30's racers, but much more refined airframes.
 
Walt said:
Does anyone make a cold air replacement sump for a Vertical intake? When I switched from carb to FI that thought definately crossed my mind.
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Every cold induction system for the Lyclone 320/360 that I could find on the market today seems to be available in horizontal only.

We have it on the ECI IO-360 in the RV-8 and it definitely works as advertised.
 
terrye said:
The horsepower of an internal combusion engine is:
HP=PLAN/33,000
where
P=brake mean effective pressure
L=length of stroke (FT)
A=area of piston (in^2)
N=number of power strokes per minute
Click to expand...

I took data from a lot of different normally aspirated engines, both car and airplane, and I formula I found that works really well in predicting HP on most engines is: cid X rpm / 5280; it's loosely based on the PLAN(K) you wrote of.
320 X 2700 / 5280 = 163.6
 
SHIPCHIEF said:
...BLOW-enhance exhaust blowdown, prevent reversion, optimize scavenging see CAFE exhaust system tests. Exhaust jet thrust, see Kent Paser's Speed with Economy...
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I looked at the CAFE data a whole bunch.

http://http://cafefoundation.org/v2/research_reports.php

Looks like a 4 into 1 with 40 inch primaries is what a 360 likes - worth 8-10 HP. I built this for my Hiperbipe and it works well, though packaging 160 inches of exhaust tubing is a nightmare. Collector length must be tuned as well, but it's easy to do on the ship using the age old "spray paint burnoff" trick (look for highest temperature, cut collector at that point).
 
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Porting

After attending a forum by Klaus Savier at OSH this year, I came away with the best bang for the buck HP increase being porting the cylinders. i.e. grinding and smoothing the intake (and presumably exhaust) passages. On one particular cylinder, he showed >30% flow improvement on a flow bench from stock to ground.

I've never done it, but it looks like it could be done for next to nothing.
 
flowing cylinders

You will find disagreement among engine builders as to whether "flowing" the cylinders will produce a measurable horsepower increase. UNLESS you remove so much material as to conpromise the life of the cylinder. Flowing will produce a smoother running engine.
One of the most effective internal mods is high compression pistons. 9-1 will produce a few horsepower. 9-1 is about $500 for the pistons for the parallel valve engines. 10-1 about $1000-1200.
9-1 are stock Lyc pistons, 10-1 are custom.
 
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