hp incrase pistons

[trx250r180]

anybody know how much difference on a 05 450r a 11.5 or a 13 to1 piston makes with a hrc cam and a full exhast,2-4 hp maybe??is it worth the change from stock? is there noticeable increse in power or just change power curve?

[pro-rider46]

i think i heard for every half of a compression point is like a 3% increase in power.


stock is 10.5:1, and chad502ex can make a 17:1

[chad502ex]

I make 15:1 pistons that with machining of the cylinder head, I can obtain 17:1 and still fit any camshaft currently available...

the chart below is percentage increase in hp..

[trx250r180]

so if im reading graph right if have 10to 1 now and bump to 13 to 1 is a 6.6 hp increase? thats a lot of hp for just a piston swap

[chad502ex]

Originally posted by trx250r180
so if im reading graph right if have 10to 1 now and bump to 13 to 1 is a 6.6 hp increase? thats a lot of hp for just a piston swap

yes, you have read the graph correctly.

6.6% increase in HP is like going from 39 stock to 41.5hp just on compression increase alone. That doesn't include increasing the size, or more accurately, increasing displacement.

That chart is a mathmatical gain derived from variables such as thermal efficiency, fuel efficiency to atomize, cylinder filling, compression chamber efficiencies, and piston dome efficiencies that inhibit maximum power output... its just an estimation but is close enough to use..

[chad502ex]

I've noticed a couple of question being raised around on other forums regarding the chart I posted above that could be detailed further here. I hope that trx450r180 will permit further tech talk discussions in this thread. If this is a problem, let me know and we can move this information and start another topic.


The numbers in the chart above is calculated and is used to estimate the theoretic percentage gains for an associated compression increase.

Before I get into how the numbers in the chart above were determined, I'd like to remind everyone that Static Compression is not as important to a running engine as Dynamic Compression is for estimating potential power or efficiency of the engine.

The figures in the chart above are based on static compressions, when, more importantly, its the dynamic compression, always being lower than static, that lift the percentage gains slightly higher than posted. Variables in a running engine such as the exhaust valves ability to exit thermal gasses, the exhaust valve thermal conductivity through the valve seat, the thermal transfer through the piston to the cylinder wall, the coolants ability to extract heat into water jackets to be cooled externally, the exhaust pipes ability to smoothly transition to ambient temp/pressures, all help the engines ability to increase efficiency. There is a point however where heat losses start to cancel efficiency gains when static compressions approaches 17:1 as pictured below (thanks GPracer2500)

I centered my 15:1 Static CR piston design on the notion that dynamic compression being lower in 450R applications than static if used with larger camshaft profiles will not be near the point where heat losses dominate the efficiency gains. The chart below that was found by GPracer2500 peaks near 17:1 before the losses begin to provide no additional gains. The crossover in the chart below is 15:1, hmmm. Using my piston, anyone can easily target 17:1 peak with head machining, if desired.

Thermal conditions occur when the engine is running, not when the engine is in "Static" conditions. So, wouldn't make sense to determine dynamic compression first, then apply thermal efficiency calculations to determine what the thermal losses in the system (engine) are?

I could care less about Static Compression,.. those figures are just for the public to generalize for octane requirements, but in fact, advertised static compression do not determine thermal efficiencies, octane requirements, or timing considerations....


Thermal efficiency is how effectively the engine can convert heat into mechanical power.

Thermal efficiency is meaningless in an engine that isnt running and making heat.

approx 1/3 of the fuel energy is exited out the exhaust pipe as lost heat.

approx 1/3 of the fuel energy will be lost to the cooling system, leaving roughly 1/3 of the energy available for power output.

I'll get to the formula in the next posts...

[chad502ex]

the efficiency equation used...

[trx250r180]

quote

I've noticed a couple of question being raised around on other forums regarding the chart I posted above that could be detailed further here. I hope that trx450r180 will permit further tech talk discussions in this thread. If this is a problem, let me know and we can move this information and start another topic

please keep this going ,i view this site to get information,and hope others will gain from my questions and learn as well

you seem very knowlegegeble on engines and i had no idea you could run 15 to 1 or even 17 to 1 in a gasoline engine,i thought only diesel engines could run that much,i am from automotive field ,own a auto recycling yard and i know in car engines adding high duration camshaft you can get away with a little higher compresion because the valves are open longer releasing cylinder pressure to help avoid detonation,i would think an atv engine would be similar ,so how are you getting the engines not to detonate with such high compresion numbers? big cams ?special fuels?

another question,is there a chart helping to know if your engine needs race gas or will be ok off pump gas,it seems higher compresion would make more heat and if lugging in woods and engine temps climb would aid to detonation,i know there would be a lot of variables ,i guess is there a way to see if a hrc cammed 05 trx450 with 12.5 or 13 to 1 compresion would be ok with 92 pump gas with full lrd exhast

[chad502ex]

Originally posted by trx250r180
quote

another question,is there a chart helping to know if your engine needs race gas or will be ok off pump gas,it seems higher compresion would make more heat and if lugging in woods and engine temps climb would aid to detonation,i know there would be a lot of variables ,i guess is there a way to see if a hrc cammed 05 trx450 with 12.5 or 13 to 1 compresion would be ok with 92 pump gas with full lrd exhast

great questioning.

Your concerns about detonation is valid. There is plenty of guessing going on without anyone investing any research on the topic.

I hope to be able to provide proof of octane requirements in the near future. My plan is to connect knock sensors and quantify the audible frequencies (pinging) using different motor octane fuels. A knock sensor connected to an Oscilloscope can capture, record the knock frequencies within any engine. Essentially, its what the computer in cars do. Once a ping is detected, the computer will try to adjust ignition timing to reduce its affect. However, ignition retards only reduces its amplitude slightly.

Generally, variables such as dynamic compression determined from the intake closing BTDC, MON of the fuel, and ignition timing can allow for estimation. Estimation sucks! I want to know. Its the engineer in me, which is why I want to test and measure!

This is why it cracks me up to see ppl buy pistons using its advertised STATIC Compression as a determination of the octane requirement without understanding that its also dependent upon the camshaft selected... sure, piston selection can be generalized to recommend the octane requirement, but not accurately at all...

KNOCK sensors costs $30 and would be real easy to 32 bit them into 3d igntion timing on the 450r's...

Why the quad manufactures havn't implemented knock sensors on the sport quad models where performance enhancements is inevitable is beyond me....

[chad502ex]

this chart illustrates the audible ping frequencies within the cylinder as the sound waves from the ignition wavefront are reflected about in the cylinder after detonation.


I'd rather not get into the physics of 'modes' where constructive and destructive nodes exist to add or cancel in the wavefront energy. The illustration is meant to provide this discussion with the frequencies of the ping for its associated resonat cavity (aka cylinder)....

[GPracer2500]

Originally posted by chad502ex
....I'd rather not get into the physics of 'modes' where constructive and destructive nodes exist to add or cancel in the wavefront energy....

:p Understood. I was gonna use this graphic in an "Engine Trivia" thread, but I figured no one would get it. It was gonna be:

What is this and what does this have to do with gasoline?
http://i34.photobucket.com/albums/d133/gpracer2500/huygens00.gif

But anyway....are you using software or something to make that last chart? Are the "modes" different knock intensities? Currently I'm reading a paper called The Intensity of Knock in an Internal Combustion Engine: An experimental and Modeling Study. It's interesting so far, although I've just started getting into it.

BTW, that other thread wasn't meant to be anything underhanded on my part--I think you know that but I wanted to say it explicitly just in case.

[chad502ex]

Originally posted by GPracer2500
BTW, that other thread wasn't meant to be anything underhanded on my part--I think you know that but I wanted to say it explicitly just in case.

no worries. If you have any questions, you can always find me here.

two waves- one sinx and the other being cosx where the third represents constructive and destructive interference in the time domain.

where the two waves are in phase, constructive interference will exist to cause a double in amplitude. where the two waves are out of phase the amplitude is zero

modes are essentially multiples or harmonics of the fundamental frequency. Pings are rich in harmonic energy and extend out beyond audible frequencies where their amplitudes or intensities degreasing linearly as frequency increases.

my last chart can be derived by determining the resonant frequency of a cavity as the volume is changing with RPM. Determining the resonant frequency for an associated cavity (engine cylinder) is a bit more difficult to model as an engine cylinders volume is always changing with time and is difficult to model with shape of the dome/CC. Exciting the cylinder with energy from an the detonation event before the main ignition event causes two wavefronts to collide where they meet. The frequencies are essentially produced from the wavefronts reflecting off the cylinders metal surfaces..

[sandmanblue]

Wow, that's a lot of stuff there.

Not that I'm chiming in to disagree. It might be easier to just say 1 - 1.5 hp per point of compression increase in a 450 sized motor....

Carry on....

[chad502ex]

here's something interesting I found in a SAE paper.. A Variable Reactive Compression Piston (VRC)

The idea is for the piston to immediately react to changes in cylinder pressure.

Basically, the upper part of the piston is spring loaded, but attached, to the lower skirt part of the piston..

What's kinda funny to me is a couple years ago Mixxer from VCP, (at that time was his first failed business name) asked me in public forum if I were to design a piston what would be details of it. I jokingly suggested a design like a Hammerhead dart- 2 piece spring loaded out of carbon fiber. LOL! What's always been funny to me is that was the name of Mixxers first piston name called the "Hammerhead",....

Anyway, this is what the piston is,... be sure to read the paper when you get a moment,.. interesting....

http://me.engin.umich.edu/autolab/Publications/Adobe/P2005_06.PDF

[GPracer2500]

^ Nice. Thanks for the link.

[chad502ex]

bump.... :devil:

the pistons will be shipped tomorrow...

:macho

[chad502ex]

Originally posted by trx250r180
so if im reading graph right if have 10to 1 now and bump to 13 to 1 is a 6.6 hp increase? thats a lot of hp for just a piston swap

BTW: I commented early in this thread that you were correct, but this is not a HP increase, but a percentage (%) gain in hp...

hope this helps.

[trx250r180]

chad,do you custom make a piston that would yield 12.5 to 1 with a hrc cam for a 05 trx450r ?if so would like one if you sell them,i dont mind price of race fuel,its just not always available and 92 pump is ,and i dont want a quad cant ride if race gas not avalible al the time

[chad502ex]

Originally posted by trx250r180
chad,do you custom make a piston that would yield 12.5 to 1 with a hrc cam for a 05 trx450r ?if so would like one if you sell them,i dont mind price of race fuel,its just not always available and 92 pump is ,and i dont want a quad cant ride if race gas not avalible al the time

I may decide to lower the compression on my 15:1 to 12.5:1 someday, but honestly..... I prefer to offer pistons for customers that need a piston with features that isn't offered by anyone but me.. a 12.5:1 piston is readily available and offered by all piston houses and builders... My favorite shelf pistons are produced by CP Pistons. CP Pistons have race pistons and shelf pistons that could fit pump gas requirements. My ultra-light 15:1 piston is designed for "RACE GAS ONLY". If you can run race gas, and want the very BEST race piston available- then this is it!

I hope you can see that I'm only trying to suggest something more fit for pump fuel. When your ready to fully commit to RACE FUEL and desire 55+, give me a call.

[wppracing]

Here is an example of just a piston change.
Wiseco 13:1
Baldwin 14:1

[chad502ex]

Originally posted by wppracing
Here is an example of just a piston change.
Wiseco 13:1
Baldwin 14:1

yes Brian- great example of compression increase gains...

My 15:1 should have similiar gains....

and you remember this chart,... it works against your dyno run too Brian!!! :cool: