Another Stihl 460 build

[Rich Fife]

It would have lessened the downforce on the right side of the deck some and maybe decreased the drag.

Here is about the only published cfd results for dirt cars, notice the name on the nose!

Simulating a Dirt Late Model Racing Car in CFD - Advanced CFD Technology Engineering Experts - TotalSim

TotalSim has completed an aerodynamic analysis of a Dirt Late Model using CFD showing how these cars are able to corner at high speed on slippery tracks

www.totalsim.us

This is a badass article! LMs are the best racecars everrrrrrr... period.

 

[Rich Fife]

I get that. But if it doesn’t matter because you’re cutting the base anyway…

Well, When I finished cutting the base, the base was noticeably thicker at one end... I'll have to go out to the junk box to see if I still have it... it was so bad, that the saw wouldn't rotate 360*... I might have an old video on the laptop showing the base after the cut. After this cylinder I "kinda" backed down from promoting China stuff... lol

 

[thompsoncustom]

Those are to smooth the air flow after the trailer to decrease the low pressure region which is where the majority of the drag comes from. Dimples are more like the vortex generators (inverted naca ducts) at the back of the sleeper to keep the flow attached down the trailer. Sometimes you'll see another row of them at the end of the trailer.

I wonder if adding dimples to the bottom half/quarter of the skirt on the inside could be beneficial than.

 

[srcarr52]

I wonder if adding dimples to the bottom half/quarter of the skirt on the inside could be beneficial than.

On a semi the dimples would need to be the radius of a basebase (maybe softball) to do anything. That's why they use the stick on vortex generators that are way more efficient at creating a disturbance to reduce the boundary layer.

 

[Rich Fife]

Simulating a Dirt Late Model Racing Car in CFD - Advanced CFD Technology Engineering Experts - TotalSim

TotalSim has completed an aerodynamic analysis of a Dirt Late Model using CFD showing how these cars are able to corner at high speed on slippery tracks

www.totalsim.us

What's your take on Solid front Axle vs IFS on Late Models? I've talked with Austin Kirkpatrick a couple years ago... he gave me some pointers as well as direction which helped the race program... but, I was strictly against and strongly disliked solid front axles UNTIL Kirkpatrick Drove away with it at the 2020 Carolina Clash... He was literally night and day faster through the apex. This opened my eyes a bit...

 

[Rich Fife]

This was the Last "Street Stock" that I built. "Kratos"

 

[Moparmyway]

Well, When I finished cutting the base, the base was noticeably thicker at one end... I'll have to go out to the junk box to see if I still have it... it was so bad, that the saw wouldn't rotate 360*... I might have an old video on the laptop showing the base after the cut. After this cylinder I "kinda" backed down from promoting China stuff... lol

That only happens if you don’t base your cut off of the bore. IMHO, the bore rules, everything else follows. I believe that your results provide the proof of my statement

 

[Rich Fife]

That only happens if you don’t base your cut off of the bore. IMHO, the bore rules, everything else follows. I believe that your results provide the proof of my statement

This cylinder wasn't my first rodeo... I Always ensure the bore is dialed-in, (front and back)... and I always make sure the base is perpendicular to the bore... for obvious reasons. Before this cylinder I was China this China that etc... I read horror stories, but, figured the vast majority of those stories came from Stihl, Husky, loyalists... Well, like the saying goes "if you play the game long enough, youll end up getting played"... after that cylinder, i cut back on pushing the China stuff. Now, When the cylinder came in, the first thing I did was stick it on the 660 clone so i could get my base numbers... it WOULDN'T rotate 360*... it bound up maybe 2/3rds the way up in the bore... I chucked it up in the lathe, the base was so far out (and extra meaty) with the bore running true, even The squishband was messed up... not nearly as bad though... I 4 pointed the squish had the bore dialed in the front and rear... it was simply a cheap China cylinder that was f'd up like no other.
I was hesitant on ordering the 381 cylinder for the 440....

 

[srcarr52]

What's your take on Solid front Axle vs IFS on Late Models? I've talked with Austin Kirkpatrick a couple years ago... he gave me some pointers as well as direction which helped the race program... but, I was strictly against and strongly disliked solid front axles UNTIL Kirkpatrick Drove away with it at the 2020 Carolina Clash... He was literally night and day faster through the apex. This opened my eyes a bit...

I know he did so well they changed the rules and made it illegal.

It's a lot easier to tune your spring stiffness for the necessary wheel stiffness with a straight axle because you don't have the non-linearity of all the caber gain. Also the front wheels are coupled so it has a different roll stiffness.

 

[Rich Fife]

I know he did so well they changed the rules and made it illegal.

It's a lot easier to tune your spring stiffness for the necessary wheel stiffness with a straight axle because you don't have the non-linearity of all the caber gain. Also the front wheels are coupled so it has a different roll stiffness.

Exactly... this dude thought outside of the box and the big guys smacked his peepee because his homebuilt chassis and engineering utterly destroyed their big money R&D. It was insane to watch him race... the speed he carried into and through the corners was insane. Our Street Stocks range from 420-500hp and I struggle to set the cars up trying to achieve what he did that night.
Our current cars are tied down in the front with chains/limiters shocks and we also use bump stops from time to time.
Shiiit all I have left is my racing suit and fab equipment... some spare parts. I kinda want to race but I dont want to spend my money... I'd much rather tinker with saws... I think.

 

[Rich Fife]

I know he did so well they changed the rules and made it illegal.

It's a lot easier to tune your spring stiffness for the necessary wheel stiffness with a straight axle because you don't have the non-linearity of all the caber gain. Also the front wheels are coupled so it has a different roll stiffness.

Have you seen pictures of the solid axle and how he modified it for cleance, spread, lengthened and adjusted the inner "C" (for the balljoints) camber/caster... Definitely interesting.

 

[Powerstroke Cowboy]

How bout that dimpled piston?

 

[Rich Fife]

What about it?

 

[Powerstroke Cowboy]

It's dimpled......

 

[Rich Fife]

Why yes it is. Was Inspired by the overweight spandex wearing ladies.

 

[Powerstroke Cowboy]

On a more serious note. I have been watching to see when dimpled pistons take off. They have always intrigued me. But I am a huge skeptic.

I wonder how much surface area was gained buy the dimples?

More surface area should give more power just from the fact the pressure has more area to push against.

Another thing is you just made the piston lighter. That's a plus as well.

But, more surface are also means there will be more heat transferred to the piston. So more heat will be getting into the crank. Plus now the rings have none heat to transfer to the cylinders.

With the dimples there's also more sharp edges, they collect heat easier than a smooth surface. Plus, heat stress cracks start from sharp edges.


I would think the last two deals should be able to be took care of by a good quality thermal coating. But, I am still skeptical at how well a thermal coating will hold up in a combustion chamber.

It will also be interesting to see if the dimples fill up with carbon over time.

I like the fact you are playing around with the dimpled piston concept.

 

[Moparmyway]

This cylinder wasn't my first rodeo... I Always ensure the bore is dialed-in, (front and back)... and I always make sure the base is perpendicular to the bore... for obvious reasons. Before this cylinder I was China this China that etc... I read horror stories, but, figured the vast majority of those stories came from Stihl, Husky, loyalists... Well, like the saying goes "if you play the game long enough, youll end up getting played"... after that cylinder, i cut back on pushing the China stuff. Now, When the cylinder came in, the first thing I did was stick it on the 660 clone so i could get my base numbers... it WOULDN'T rotate 360*... it bound up maybe 2/3rds the way up in the bore... I chucked it up in the lathe, the base was so far out (and extra meaty) with the bore running true, even The squishband was messed up... not nearly as bad though... I 4 pointed the squish had the bore dialed in the front and rear... it was simply a cheap China cylinder that was f'd up like no other.
I was hesitant on ordering the 381 cylinder for the 440....

Maybe be a little more specific/clear in what you’re describing ? I interpreted your post, as read, that it wouldn’t rotate due to zeroing off the crooked base.

If you read it, then my comment applies. A little more sugar and less vinegar, eh ?

 

[Loony661]

On a more serious note. I have been watching to see when dimpled pistons take off. They have always intrigued me. But I am a huge skeptic.

I wonder how much surface area was gained buy the dimples?

More surface area should give more power just from the fact the pressure has more area to push against.

Another thing is you just made the piston lighter. That's a plus as well.

But, more surface are also means there will be more heat transferred to the piston. So more heat will be getting into the crank. Plus now the rings have none heat to transfer to the cylinders.

With the dimples there's also more sharp edges, they collect heat easier than a smooth surface. Plus, heat stress cracks start from sharp edges.


I would think the last two deals should be able to be took care of by a good quality thermal coating. But, I am still skeptical at how well a thermal coating will hold up in a combustion chamber.

It will also be interesting to see if the dimples fill up with carbon over time.

I like the fact you are playing around with the dimpled piston concept.

I’m going to reference back to my days building racing high performance V8’s again here, BUT: flame propagation across the piston top was a hot topic about 15 years ago. What was found, based on dyno results, was that controlling the burn across the piston top made the engine easier to tune. Shiny new pistons made less power than taking those same pistons and bead blasting them, leaving the surface roughed a bit…

Also, as far as coatings go, back again about 15 years, they were already coating combustion chambers and piston tops with heat resistant coating to contain the heat in the combustion chamber, with good results. May not be cost effective in a small engine like a chainsaw, but on top fuel dragsters it made a difference in power, as well as part longevity.

 

[Rich Fife]

Maybe be a little more specific/clear in what you’re describing ? I interpreted your post, as read, that it wouldn’t rotate due to zeroing off the crooked base.

If you read it, then my comment applies. A little more sugar and less vinegar, eh ?

Yeah, I'm not the best at clearly explaining things... in my mind, they seem clear. Lmao

 

[Rich Fife]

I’m going to reference back to my days building racing high performance V8’s again here, BUT: flame propagation across the piston top was a hot topic about 15 years ago. What was found, based on dyno results, was that controlling the burn across the piston top made the engine easier to tune. Shiny new pistons made less power than taking those same pistons and bead blasting them, leaving the surface roughed a bit…

Also, as far as coatings go, back again about 15 years, they were already coating combustion chambers and piston tops with heat resistant coating to contain the heat in the combustion chamber, with good results. May not be cost effective in a small engine like a chainsaw, but on top fuel dragsters it made a difference in power, as well as part longevity.

I LIKE it!