Engine Design and modification

11 posts in this topic

Posted

So I wanted to start up a thread discussing different engine designs and modifications that may have more benefits than others. I will start off with a few questions that I know some of you may have some answers to. It would be great for everyone to join in and see what we can learn from it all. 

My Question.

has anyone ever offset the crankshaft center line from the center line of the cylinder/s to reduce the piston ring to cylinder loading on the combustion stroke (this is the highest load phase)? Please disregard the fact that doing this modification will have a lot of cost attached to it.

Share this post


Link to post
Share on other sites

Posted (edited)

I do it the easiest less costly way. we Offset the pin in the Piston, make for a nice quite transition.

Now in some applications we have run right up pins and made for a noisy piston but it made more power.

I think we mostly offset .5mm-1mm

 

 

Edited by pistonguy
2 people like this

Share this post


Link to post
Share on other sites

Posted (edited)

I found it

This was for factory Yamaha when Chad Reed was riding for them

For some reason my team back at the factory made a tool to for a straight up pin and Its darn hard to get there business and they wanted a 1mm pin offset.

Time in these situation is critical we didn't have time to make another costly tool so we made them a few test pieces  with a .5mm offset.

The results were Catastrophic and Game over.

I put tape over the number because I can't have anyone making calls trying to get the Factory Yamaha race piston they saw on the internet.

Your really not going to notice the pin offset of .5mm with a eyeball, its offset to the exhaust side.

A coule bells and whistles, Lateral Gas ports on the top ring and a Pressure Accumulator groove in-between the two rings.

And we don't use Three Ring Pistons to go racing with..

 

 

DSCN0884.jpg

DSCN0885.jpg

Edited by pistonguy

Share this post


Link to post
Share on other sites

Posted

thing of beauty

Share this post


Link to post
Share on other sites

Posted

So that's why pistons have an intake and exhaust side! (minus the valve reliefs...let me have my fun...)

Share this post


Link to post
Share on other sites

Posted

Pistons exhaust side is probable way more active than his intake side hahahaha sorry bud too much scotch.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

I found it

This was for factory Yamaha when Chad Reed was riding for them

For some reason my team back at the factory made a tool to for a straight up pin and Its darn hard to get there business and they wanted a 1mm pin offset.

Time in these situation is critical we didn't have time to make another costly tool so we made them a few test pieces  with a .5mm offset.

The results were Catastrophic and Game over.

I put tape over the number because I can't have anyone making calls trying to get the Factory Yamaha race piston they saw on the internet.

Your really not going to notice the pin offset of .5mm with a eyeball, its offset to the exhaust side.

A coule bells and whistles, Lateral Gas ports on the top ring and a Pressure Accumulator groove in-between the two rings.

And we don't use Three Ring Pistons to go racing with..

 

This is awesome stuff here Piston, does any company manufacture pistons with offset wrist pin bores? 

I have some knowledge of the lateral gas ports to increase the top ring to cylinder seal. 

Could you lets us know the reason for the accumulator groove between the two rings, and I know having only 2 rings for racing is the way to go

Everytime I pull a high mileage GY6 apart I see the same ware on the pistons and cylinder. I'm sure having a slight offset may help with this. I also thought about an oil squirter to bathe the underside of the piston and bore to increase lubrication. But I don't think there is space for this modification

Share this post


Link to post
Share on other sites

Posted

Honda developed this train of thought (offset bore and rolling center of the crank) years ago

Share this post


Link to post
Share on other sites

Posted (edited)

Ya all the aftermarket piston  manufactures here in the states have offset pin bores.

Everything I did auto, cycle, tav, snow, we did with offset pin bores other than custom project per customer specs.

Another way you may want to think about on that thrust load is the Rod angle, I don't know the stock rod length to translate that into a rod stroke ratio.

A longer connecting rod will help straighten out that angle and be must less harsh on the cylinder wall and piston skirt in that transition at the bottom of the stroke.

Tho stuffing a longer rod in her will require a customer piston and the Wrist Pin location will now be higher up in the piston.

Also remember at TDC and BDC thats were the engine oil has its toughest job, as that piston slows then turns direction is extremely difficult to maintain a film of oil at those slow piston speeds. we will always see accelerated wear there.

 

 

ProductInfo.aspx

These would be the folks that you would have the best chance matching up a rod only +2mm, +3mm or more.

They list the rod specs but would be a guessing game searching, if you call them with your specs I'm sure they have there system filtered thru engineering to quickly be able to see if there is any match at all.

 

Edited by pistonguy
1 person likes this

Share this post


Link to post
Share on other sites

Posted

Oh on the Pressure Accumulator Groove, Its simply a place for Pressure to go from Detonation or edge of detonation, without giving the pressure a place to go it will Lift the Top Ring off the cylinder.

Played with some Anti Det grooves along with the Groove, it seemed to come about manufacturing pistons for the Buick Indys, in all reality it was fuel management problems so they were burning up allot of pistons and was a couple bells and whistles that helped with the problem until they solved all the fuel management problems.

Buick prêt much turned that over to Brayton racing father of driver Scott Bryaton until Scott was killed shacking down the "B" car...

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Thanks a lot for sharing this piston, Really appreciate sharing the knowledge. 

Tell me what you think about this for optimizing our little engines. It may sound counter intuitive, but may help engine ware. If we use one of the tall blocks that the 8.2mm stroker crank would use with a stock or undersized crank (2.5mm or 6.6mm) and a longer con rod to reduce the angle. How much benefit do you think we will have, and couple that with potentially having an offset piston.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now