Have new gx200 - thinking about piston

D

Devil-D-Dawg

New member
What is the functional difference between the honda flat top and the drop-in wiseco?

Either install will use the appropriate arc rod.

Thanks in advance.
 
The Wiseco drop in offers a longer rod ratio which reduces stress on the wrist pin and crank journal especially at high RPMs, more dwell time at the top and bottom of the stroke which aides in compression and combustion. Plus using the Wiseco piston and .490 wrist pin with the 3.595 rod gives you a 25% on top end weight reduction, the 3.707 rod gives you a slightly longer ratio and because you have to cut the top of the piston gives you more weight reduction producing more power and less stress on the engine. I have a post on our Facebook page (ARC Racing) that explains rod ratio a little better.
 
The Wiseco and long rod set-up will provide a considerable increase in power over the Honda Piston and Std length rod. However, the Wiseco is prone to failure. We have seen quite a few pistons with broken ring lands, broken skirts, or splitting in the wrist pin area. More troublesome is the wrist pins which we see quite a lot of breakage. The available HD pins help, but have not eliminated the problem. We also see a lot of wear on the pin and in the pin hole. Ring life is shorter than the OEM Honda rings.

The Honda piston and Arc rod is almost bullet proof provided compression and rpms are reasonable (and correct oil is used). But again, power and engine acceleration is not as good.
A great compromise is the GX160 UT2 Flat-top and with the 0.100” longer rod

http://www.nrracing.com/product-p/arcbilletrd100.htm

This provides an increase in rod in length without the expense and loss in durability of going to a Wiseco set-up.
 
Nrracing said:
The Wiseco and long rod set-up will provide a considerable increase in power over the Honda Piston and Std length rod. However, the Wiseco is prone to failure. We have seen quite a few pistons with broken ring lands, broken skirts, or splitting in the wrist pin area. More troublesome is the wrist pins which we see quite a lot of breakage. The available HD pins help, but have not eliminated the problem. We also see a lot of wear on the pin and in the pin hole. Ring life is shorter than the OEM Honda rings.

The Honda piston and Arc rod is almost bullet proof provided compression and rpms are reasonable (and correct oil is used). But again, power and engine acceleration is not as good.
A great compromise is the GX160 UT2 Flat-top and with the 0.100” longer rod

http://www.nrracing.com/product-p/arcbilletrd100.htm

This provides an increase in rod in length without the expense and loss in durability of going to a Wiseco set-up.
Click to expand...

Thank you VERY much - this was exactly what I was wondering.
 
That's why I use JR-Racecar piston. Best on market. Use Total Seal Gapless rings with it. Also use heavy duty wrist pin.
 
The Honda piston and Arc rod is almost bullet proof provided compression and rpms are reasonable (and correct oil is used).
I know this is subjective, but what is the correct oil?
 
JPR57 said:
more dwell time at the top and bottom of the stroke which aides in compression and combustion.
Click to expand...
I have a spreadsheet that will show you the dwell time difference with different Rod lengths. Give me the lengths of the two rods and the stroke of the engine and I'll tell you how much difference there is. You will be surprised at how little difference in dwell time there is. If you measure to three places, I don't think you'll see any change, but I can measure to as many places as you want, (5 – 6 places in travel, or more, with as little as .1 degrees of rotation, is possible) in which case you will see some slight difference.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.(Al Nunley)
 
JPR57 said:
The Wiseco drop in offers a longer rod ratio which reduces stress on the wrist pin and crank journal especially at high RPMs, more dwell time at the top and bottom of the stroke which aides in compression and combustion.
Click to expand...
while the longer Rod will give you a better Rod length to stroke ratio, (still far from ideal) the dwell time changes almost nothing. Both rods, the long one and the short one, move the piston down .001" at 2.6 degrees of crankshaft rotation. If I go to five decimal places on the travel, there is a very very slight difference.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.(Al Nunley
 
So what are you recommending Al? You have a spreadsheet as you often point out, but I just wonder if you have the slightest idea of how a change in rod length has an effect on performance. I ask this because you involve your self with every rod length conversation. Is the longer rod length part two of the Holy Grail? Just curious? FYI. Wikipedia is not a reliable source for how to build a race engine!
 
Question
Al how about calculating the number of degrees for each rod too move the piston down the cylinder from tdc .200.
That may show a difference more so than simply 2.6 degrees for each .001.
Or would it be 200 times 2.6 degrees? I know that ain't right, just visualizing it seems like it would be about 30 degrees.
I need excel:(
 
Wes Snow said:
So what are you recommending Al? You have a spreadsheet as you often point out, but I just wonder if you have the slightest idea of how a change in rod length has an effect on performance. I ask this because you involve your self with every rod length conversation. Is the longer rod length part two of the Holy Grail? Just curious? FYI. Wikipedia is not a reliable source for how to build a race engine!
Click to expand...
I'm not recommending anything. Apparently you did not read very closely. Someone said the longer Rod changes the dwell time at top dead center. I was just pointing out that, yes it does, but you have to go to four and five decimal places to see the difference. Few have a measuring device that will display four and five decimal places. If you're interested, my spreadsheet can show you just exactly how much difference there is.

What's your problem?

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.(Al Nunley
 
I really would like to know how many degrees for .200 of piston movement, one rod length vs the other.
Please Al.
 
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