GYTR Head and High Compression Piston


11 replies to this topic
  • dreid32

Posted September 05, 2010 - 11:25 AM

#1

Has anyone tried the GYTR Head assembly and high compression piston. I'm anticipating responses of how much better "local tuner" ported head is, but I'm really looking for information on anyone that has actually installed and raced this set up.

  • dreid32

Posted September 05, 2010 - 05:55 PM

#2

Forgot to add, I'm interested in the modifications to a 2010 yz450f

  • racerxx276

Posted September 05, 2010 - 06:15 PM

#3

I put just the GYTR cams in my 2010 bike, along with a DR D pipe and changed the map.
I didn't want a beast to ride. I felt that the whole kit would be fast, but would take a lot more effort to ride. It now accelerates pretty hard in the low-middle and some top .

I really like how it works now... and if I want it faster I run straight 100 octane instead of 1/2 -91 and 1/2 -100.

  • grayracer513

Posted September 05, 2010 - 07:48 PM

#4

Octane number is unrelated to power output. It's more accurate to say:

... and if I want it faster I run Straight Race Gas instead of 1/2 pump and 1/2 race gas



  • brentn

Posted September 06, 2010 - 05:33 PM

#5

Unless you have the GYTR high compression head, or any other manufacturer that exceeds the stock compression ratio, 100 octane is useless for performance.

  • grayracer513

Posted September 06, 2010 - 06:10 PM

#6

Four-strokes don't use alternate heads to raise compression, they alter the piston.

You are correct in that any more octane than the amount that prevents detonation is unnecessary, and won't do anything for the engine, but true racing fuels typically do produce more power than pump fuels for reasons that have nothing to do with their octane rating.

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  • brentn

Posted September 06, 2010 - 06:29 PM

#7

I have no idea why I said head, my brain is not working today. I meant to say piston...

wow, I need to take some vitamins or somethin..

  • brentn

Posted September 06, 2010 - 06:31 PM

#8

Four-strokes don't use alternate heads to raise compression, they alter the piston.

You are correct in that any more octane than the amount that prevents detonation is unnecessary, and won't do anything for the engine, but true racing fuels typically do produce more power than pump fuels for reasons that have nothing to do with their octane rating.


I suppose this is when you get into "oxygenated fuel" right?

  • grayracer513

Posted September 06, 2010 - 07:30 PM

#9

That's one approach, yes, but high energy racing fuels are not all oxygenated. Gasoline is a blend of several different compounds, not just one or two as was the case 50 years ago. Switching one compound for another, or adjusting the balance of the various components can change a lot.

Most modern pump gasolines blended for emission reduction are oxygenated by one means or another, and some of them are really not what anybody would call high performance fuels.

  • Polar_Bus

Posted September 07, 2010 - 02:01 AM

#10

Four-strokes don't use alternate heads to raise compression, they alter the piston.

.


In many instances the factory supported "race" programs would offer optional OEM "race" thickness head and base gaskets as well to alter compression ratios. Not sure if Yammi follows this method specifically with the YZF's.

Edited by Polar_Bus, September 07, 2010 - 02:45 AM.


  • racerxx276

Posted September 07, 2010 - 03:24 AM

#11

The GYTR cams came with instructions to run 95 or higher octane with the cams installed.


As far as the more octane = more power goes, lets just say that my engine just runs better with the higher octane, cleaner, crisper. Maybe it feels like it has more power because it is just running better...

Now, maybe if I played with the fuel map, I could get it to run this way on 91 octane, thats entirely possible...

  • grayracer513

Posted September 07, 2010 - 07:35 AM

#12

Probably not, unless the object was to lower the compression. The late YZ450 base gaskets are a steel shim, and the head gasket is only 3 sheets of thin steel.

The GYTR cams came with instructions to run 95 or higher octane with the cams installed.

OK, but did it specify which octane rating system? The owner service manual specifies 95 octane or higher for a stock YZ450. Difference is that that 95 octane is Research Octane, which is roughly 86-88 Motor Octane, or about 90 octane under the US AKI system as you find graded on gas pumps in the US and Canada (Research# + Motor# divided by two to get the average).

Your bike may very well run better on the particular higher octane fuel, but unless it has a tendency to detonate (ping) on the 91, the power and performance improvement is coming from overall quality and character of the fuel, and the octane number has nothing to do with it. I could blend a can of 110 octane fuel for you using oxygenated 91 octane pump "emissions" premium and ethanol that would be fiercely lame by anybody's standards. Then we could compare that with a 92 octane race fuel.

I don't doubt that the fuels you are comparing perform exactly as you say, but it's a mistake to attribute the difference to the octane rating.





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