2010 2011 HC piston info. Read!!!


17 replies to this topic
  • MXR176

Posted January 14, 2011 - 06:08 PM

#1

Just had Tom Morgan do my motor on my 2011 450. Just passing on some info he told me. He said that he highly doesn't recommend using anything higher then a stock compression piston. He said that anything higher then the 12:5:1 affects the flow on top end. Just passing on some info to fellow thumpertalkers

  • grayracer513

Posted January 14, 2011 - 06:38 PM

#2

It can, but the way that the combustion chamber of the YZF is designed, a 13.5:1 piston won't reduce flow enough to offset the gain in power. If I'm not mistaken, Ron Hamps' 60+hp 2010 YZ450's use a higher than stock CR, although his championship winning 5 valve engines used a custom shaped piston crown to bring them up to that level.

There is certainly no reason to think that an engine with stock or lightly touched ports would do anything but see a net gain from higher compression.

Old school engines like Harleys and British twins did all have a practical compression limit that had to do with the height of the combustion chamber dome. Triumph twins ran better with 10:1 or so, while Norton twins had no problems with 12:1. Modern domes are very low by comparison, so that a 12.5:1 piston is essentially flat.

  • MXR176

Posted January 14, 2011 - 06:55 PM

#3

Just passing on info I was told. I think Tom Morgan has been around the block a time or two. Not doubting you at all. All I know is hes pushing 60hp also he said. Time will tell when I get this thing back together. He did the whole head remapped the ECU, Airbox mod, and Cams. He said that if I feel I need something changed on the map to just get ahold of him and he will do some adjusting for me untill its exactly the way I want it.

  • harrperf

Posted January 14, 2011 - 10:56 PM

#4

It has much more to do with the fuel used and the overall design of the piston and skirt than it does with the compression these days.

Ron will also tell you with some of the cams he uses - higher compression LOOSES power because the "dynamic" or "running" compression ratio (as discussed before in seperate thread) gets too high.

Sometimes you build so much cylinder pressure you hurt yourself!

If running the ama legal vp fuel (pro5.1 or whatever they call it now) - there really is no need to go with more compression unless the cam has a lot of wasted overlap. Ron builds a lot of motors for use on c12 - A highly leaded, high octane fuel - that LIKES/NEEDS compression.


95 percent of the time on ANY bike these days - a higher compression piston than stock looses power past peak. Often the improvements in power from a piston are from design not compression ratio. That said - to please riders - sometimes this is a good thing as it makes the engine FEEL like it revs out forever...instead of quickly slamming into the rev limiter.

So I would agree with Tom's statement - and say that most users would be surprised to learn that OEM pistons typically make the best power but are not quite as resiliant as a forged on.

  • MXR176

Posted January 15, 2011 - 05:19 AM

#5

It has much more to do with the fuel used and the overall design of the piston and skirt than it does with the compression these days.

Ron will also tell you with some of the cams he uses - higher compression LOOSES power because the "dynamic" or "running" compression ratio (as discussed before in seperate thread) gets too high.

Sometimes you build so much cylinder pressure you hurt yourself!

If running the ama legal vp fuel (pro5.1 or whatever they call it now) - there really is no need to go with more compression unless the cam has a lot of wasted overlap. Ron builds a lot of motors for use on c12 - A highly leaded, high octane fuel - that LIKES/NEEDS compression.


95 percent of the time on ANY bike these days - a higher compression piston than stock looses power past peak. Often the improvements in power from a piston are from design not compression ratio. That said - to please riders - sometimes this is a good thing as it makes the engine FEEL like it revs out forever...instead of quickly slamming into the rev limiter.

So I would agree with Tom's statement - and say that most users would be surprised to learn that OEM pistons typically make the best power but are not quite as resiliant as a forged on.


Thanks Harp. That's how Tom was explaining it to me. Then he lost me when he started talking fuel and cam stuff. Guy was making my head spin with how smart and knowledgeable he is. That's why he's worked with some of the sports best.

  • KJ790

Posted January 15, 2011 - 11:51 AM

#6

It also has to do with what cams you are running. Using cams with longer duration tends to decrease the dynamic compression ratio of the engine, so a higher compression piston can be used to try to get that back up to what it was before changing the cams.

  • grayracer513

Posted January 15, 2011 - 12:11 PM

#7

It also has to do with what cams you are running. Using cams with longer duration tends to decrease the dynamic compression ratio of the engine, so a higher compression piston can be used to try to get that back up to what it was before changing the cams.

It depends a lot, too, on where exactly you want the power.

High compression can interfere with high end power by raising cylinder pressures too far in the rpm range where the more aggressive cams are most efficient, but just as you have said, it can also be a great way to compensate for the loss of low end associated with very aggressive cam timing, and to "cover over" the interference the cams cause with lower speed operation.

For the 80+ percent of those using otherwise nearly stock engines, a high compression piston does provide a boost in the low and mid range that most people find quite productive. It's only in the more highly modified engines that you have to question using one.

  • brentn

Posted January 15, 2011 - 03:45 PM

#8

So your saying that if I dropped in a high compression piston 13.5:1 into my 2010 the only difference I would be seeing in power is because of the one ring design and not two?
Wouldn't even be worth it you say?

  • MXR176

Posted January 15, 2011 - 04:26 PM

#9

So your saying that if I dropped in a high compression piston 13.5:1 into my 2010 the only difference I would be seeing in power is because of the one ring design and not two?
Wouldn't even be worth it you say?


Sorry but you lost me. What did you just say?

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  • beezer

Posted January 16, 2011 - 06:27 AM

#10

I put a higher compression CP piston in my YZ along with a set of Hotcams and the bike is noticably faster.

  • MXR176

Posted January 16, 2011 - 11:13 AM

#11

I put a higher compression CP piston in my YZ along with a set of Hotcams and the bike is noticably faster.


Tom Morgan has designed all the latest Hot Cams since he is employed by C&L Company, just an FYI.

  • brentn

Posted January 16, 2011 - 03:43 PM

#12

Sorry but you lost me. What did you just say?


Your saying that high compression pistons hurt performance.
High compression pistons offer two things for the 2010 450, they have higher compression of course and they have a 1 ring design for less drag.
Since high compression hurts performance, then adding a HC piston with a one ring design should still yield a little more power because of less drag on the ring but the compression ratio will do nothing to add any more power?????

Just doesn't seem right that people are designing high compression pistons for this bike outright knowing that it hurts performance.
If this is information is true, why don't they just offer stock ratio pistons that one ring designs"?

  • KJ790

Posted January 16, 2011 - 03:53 PM

#13

Your saying that high compression pistons hurt performance.
High compression pistons offer two things for the 2010 450, they have higher compression of course and they have a 1 ring design for less drag.
Since high compression hurts performance, then adding a HC piston with a one ring design should still yield a little more power because of less drag on the ring but the compression ratio will do nothing to add any more power?????

Just doesn't seem right that people are designing high compression pistons for this bike outright knowing that it hurts performance.
If this is information is true, why don't they just offer stock ratio pistons that one ring designs"?


You can run one compression ring on any piston you want. I only run the top compression ring on stock pistons quite often.

Higher compression pistons are offered b/c they can help performance when pared with certain other mods. It depends on the porting, cams, and ignition timing used. Everything has to work together. A good engine builder creates a package that works with everything else. So in a stock engine the high compression piston may not offer a benefit, but with some porting and aggressive cams a high compression piston would likely outperform the stock piston.

  • harrperf

Posted January 16, 2011 - 04:15 PM

#14

You can run one compression ring on any piston you want. I only run the top compression ring on stock pistons quite often.

Higher compression pistons are offered b/c they can help performance when pared with certain other mods. It depends on the porting, cams, and ignition timing used. Everything has to work together. A good engine builder creates a package that works with everything else. So in a stock engine the high compression piston may not offer a benefit, but with some porting and aggressive cams a high compression piston would likely outperform the stock piston.


Well said plus almost every HC piston on the market is forged.

They rarely shatter when they break - where as a stock piston may detonate hard enough to shatter...

So even if there is no power improvement - you do often get a reliability improvement in some respect.

Extremely well made pistons have ring lands that are much more straight if viewed under a microscope - and sometimes the skirt thickness and profiles are altered to improve power/reduce friction.

And beyond that some pistons have deeper valve pockets to allow more aggressive cams...

It just depends on the PACKAGE a builder puts together for you.

  • brentn

Posted January 16, 2011 - 04:52 PM

#15

Ok I was mis-understanding the initial statement.

btw, the stock 2010/2011 have forged pistons, they are not cast. Says so right on the brochure and the feature page.

  • MXR176

Posted January 16, 2011 - 06:47 PM

#16

Tom Ported Polished and Flowed my head, Hot Cams Stage 2 Cams, Reprogrammed/Remapped my ECU, Wiseco 12:5:1 Piston and running it on VP U4.4. He said the last one he did like this was pushing 60hp and easy to use ridable power. I can't wait to get this thing together and ride it.

  • harrperf

Posted January 16, 2011 - 09:31 PM

#17

Go run it on a local dyno - a lot of places with only charge 30-40 bucks if all you want is to strap it on and get a run with no tuning...

takes all of about 10 minutes...

bring a buddy and run any stockish 450 to calibrate what THAT dyno reads.

Then you will know where you are at!

  • rcmxracing

Posted February 01, 2011 - 12:13 PM

#18

Tom Ported Polished and Flowed my head, Hot Cams Stage 2 Cams, Reprogrammed/Remapped my ECU, Wiseco 12:5:1 Piston and running it on VP U4.4. He said the last one he did like this was pushing 60hp and easy to use ridable power. I can't wait to get this thing together and ride it.


Well....what's the word? How did it turn out?!:thumbsup:
If your bike is still easy to ride then that's a win although for me anything I can do to avoid running race fuel makes me happy. Been down that road too many times with modified 2 strokes, PITA!





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