Joeak47's thread on cast piston VS wiseco forged piston.

[joeak47]

I tried experimenting with a few other things today... This is kind of different...
I bored the cylinder again (didn't need too),so i could experiment with a cast piston (that everybody hates),but that I prefer,to see if it would make any difference in power vs the wiseco,and to see if the cast will stay "round" in the intense desert heat unlike the wiseco's that tend to want to expand even more when they get hot.

THE PISTONS...

CAST >>> WSM brand,thats right,the cheapest I could get my hands on. Everybody says they're cheap,so why not experiment with the cheapest I could find??? It looks decent,and has a teflon coating applied to the outside. The coating is about .0001 of an ich thick. Just enough to fill in the grooves left by the machining process. I would assume that it will only last during the initial break in period. Quality japanese rings. Feels nice and light.

FORGED >>> Wiseco brand. Nice and pretty! Very well machined! Lots of sharp edges. The inside looks to be finished differently. Shot peened perhaps? I use to be able to see the grain flow of the aluminum on the inside of the piston...not anymore. Did they change the machining process? Feels heavier than the cast piston. The dome is a wee bit higher than the cast piston.

First off,on my last test, the engine was set up with a "squish" of .045 with the wiseco forged piston. Piston to cylinder wall clearance was .003 and the cylinder nice and round with no taper. The new head was phenominal as I already stated in another thread.

This time I wanted to see if if a cast piston would make a difference in power vs the wiseco among other things. I beleive that it will have a better ring seal.

The reason i wanted to try this,is because I wanted to see if it would run cooler,have the same power or more,STAY ROUND, and to see if it would give any other benefits. The cast piston was set up with a piston to cylinder wall clearance of .003 (the same),and the cylinder is nice and round with no taper.

I have the ability to bore my own cylinders,so this is old hat to me when it comes to experimenting.

I installed a WSM piston kit (that in most peoples opinion sucks) to see what would happen. The "squish" increased to .060,because the piston dome is a bit shorter than the wiseco. Nothing I can't change if need be.

I took out the new blaster with the new top end today,and noticed positive things!!! After I did the heat cycles, I headed out to the desert and proceded to "get it on" to break in the new rings. Lots of different engines speed,compression braking,shifting,etc. In other words I rode it like I ride it. after a half hour I let her cool and did it again, and then again.

Fist off,just for the record,it was 105 degrees today (7-11-2012) where I am in Nevada when I was testing. we're talking Africa hot. Here's what I noticed...
The cylinder ran 325 to 335 degrees,and the head about ten degrees cooler. This is after multiple long hard runs. When I was running the wiseco,the temperature went as high as 375 degrees,but with an outside tempurature of 96 degrees outside! WOW! I was surprised! Thats 9 degree cooler ambient tempurature! WTF?

The power was a wee bit more too! ...as I figured that it would be. I would attribute this to a better ring design than the wiseco's use. The "keystone" type ring design creates a better seal in my opinion,and I can feel it! Ring seal is EVERYTHING!

The last item I noticed was the fact that the cast piston is QUIET! The wiseco's (I've installed many) are always a bit louder. Something a trained ear can hear,and a trade off between the two pistons.

I checked all my temperatures with my infrared heat gun that I kept in my pocket on the ride. By the way... I weighed both pistons,and they weighed exactly the same... 9 ounces!

As for people saying that "Cast pistons suck"... No they don't! If they do,then why do the manufacturers install them at the factory? Things that make you go "Hmmmmm". I've never had an issue with a cast pistons...ever. Yes I've repaired blaster engines that have dropped a skirt,or had cracks in the intake windows,but this was do to excessive piston to cylinder wall clearances. I've also replaced a few wiseco's with the same issues. Routine inspection and maintenance would have detected these problems. The wiseco pistons are nice,but in my opinion...overated. They also tend to swell more than they should,even with the proper clearance and round bore. Give me a cast piston any day. The trick is to maintain the atv. Inspect things once in a while. I know of many blasters that are still running the factory cast piston. We're talking YEARS of use. Not hours. I noticed more power with the cast piston,much cooler running tempuratures,and quieter operation.
Wiseco says that they're piston makes more power? I didn't feel it. Sure its forged,but I prefer the advantages of the cast piston and its ring design.

You will notice scuff marks on the wiseco.

Anyway,this was fun. Here's some pictures...

WSM cast piston

These have a very light teflon coating

Side view

Exhaust side

Bottom view

WSM piston is just under 9 ounces with rings,pin,and circlips

Wiseco is just under 9 ounces too.

Installed piston

Good to go.

 

[sicivicdude]

As for people saying that "Cast pistons suck"... No they don't! If they do,then why do the manufacturers install them at the factory? Things that make you go "Hmmmmm". I've never had an issue with a cast pistons...ever. Yes I've repaired blaster engines that have dropped a skirt,or had cracks in the intake windows,but this was do to excessive piston to cylinder wall clearances. I've also replaced a few wiseco's with the same issues. Routine inspection and maintenance would have detected these problems. The wiseco pistons are nice,but in my opinion...overated. They also tend to swell more than they should,even with the proper clearance and round bore. Give me a cast piston any day. The trick is to maintain the atv. Inspect things once in a while. I know of many blasters that are still running the factory cast piston. We're talking YEARS of use. Not hours. I noticed more power with the cast piston,much cooler running tempuratures,and quieter operation.
Wiseco says that they're piston makes more power? I didn't feel it. Sure its forged,but I prefer the advantages of the cast piston and its ring design.

The problem with cast pistons isn't how they live, but how they DIE. Forged pistons will crack (sometimes break a skirt, sometimes not) but will for the most part remain whole. Cast pistons crumble into a million little aluminum balls as they disintegrate.

Also, companies put cast pistons in for their other advantage...... they CHEAP to produce versus a forged piston and because the engine is new and the piston to cylinder clearance is perfect, they don't have to worry about how the piston will end it's time inside that engine. That's something the owner will deal with down the road (once the engine is out of any sort of warranty!)

Cast pistons do run tighter tolerances and do make less noise. Still not enough of an offset in my mind to justify their use in any of my engines. I have/install/run only forged pistons, period.

Wiseco and Wossner...

 

[yzrider]

There seems to be interest in the strength of Forged vs. Cast Pistons. I didn’t have a cast piston to crush in the press for a demonstration, but we’ve all seen enough carnage and know how cast pistons fly apart.



I did find an old forged Wiseco to give a substantial push demonstration. I put this old Trooper Wiseco in my 60 ton press and gave it a shove. The piston didn’t start to fail till around 40 tons. I took these photos at 50 tons of pressure.

2 Views of the same Piston after a 50 ton push





CAST PISTON:







My large press was a little over kill for the Yamaha piston. The piston started to crack almost instantly. I wasn’t able to get any kind of pressure reading


The pair: Small, Yamaha Cast
Large, Forged Wiseco.






Not much needs to be said after a look at the pics. This is a total guess but it seems as though the forged piston is 5-10 times stronger than the cast piston. This shows you folks the true story between Cast & Forged pistons.
I give Wiseco Piston a Thumbs UP.

Small Engine Machine Works Inc. - Home
“Old Dog”
JT

Everything2Stroke - How strong is that forged piston?
^^ the carnage pics are in the link... this says all that needs be said... and is the reason why i'll always run weisco

 

[Triple_B]

Everything2Stroke - How strong is that forged piston?
^^ the carnage pics are in the link... this says all that needs be said... and is the reason why i'll always run weisco

The thread is also on here.

http://www.blasterforum.com/engine-13/cast-piston-vs-forged-piston-48964/

 

[joeak47]

The problem that I have with wiseco is that they tend to swell out of round in hot enviroments compared to a cast piston. That sucks. I've had good luck with wiseco's in liquid cooled applications when it gets really hot. The reason is fairly obvious... Liquid cooling,which offers a much better controlled enviroment.

The press demonstration is pretty cool. Very informative! I still like the "keystone" designed rings better that the cast pistons offer. A better design in my opinion that produces a better ring seal. Better ring seal = more cylinder pressure = more power. Ring seal and break in is very important as we all know.

With proper jetting,clearances,and lubrication, a cast piston will have a long service life. I've seen my fair share of broken cast pistons (not on my bikes),but the bikes they came off of looked like your typical "run hard and abused" examples.

I wonder if wiseco has changed some of they're manufacturing techniques. They look different now (on the inside).

 

[joeak47]

The thread is also on here.

http://www.blasterforum.com/engine-13/cast-piston-vs-forged-piston-48964/

Thats not so bad... a little bit of tig welding and that baby would be as good as new!

 

[wwholden]

Can you explain this ring seal theory on the cast pistons. I dont see how they are different. Im sure they are but would like to be informed.

 

[Triple_B]

With proper jetting,clearances,and lubrication, a cast piston will have a long service life. I've seen my fair share of broken cast pistons (not on my bikes),but the bikes they came off of looked like your typical "run hard and abused" examples.

I 100% agree with this. All of the requirements listed should make any piston last long. It just seems that jetting, clearances, and lubrication are all hard to get exactly where they need to be, which is a good thing about the Wiseco pistons. Wiseco pistons seem that they allow a little bit of tolerance when it comes to proper lubrication, jetting, and clearance.

I could be wrong, but that is what it seems like to me, based on a little experience and from what I've heard

 

[Awk08]

i know, i know..... most of you have seen me post this numerous times,
my brand new 1996 blaster, ran very very hard for 8+ years, i sold it with the stock piston and oil injection still in it, starting on 1-2 kicks and running strong
hence when i decided to get back into quads, the choice was simple....blasters !
i do now however only run wiseco's

good tests and info Joe !!!!!

 

[scotj77]

i am with civic on this one. i have melted my fair share of pistons learing how to build a 2 stroke properly and the way the cast piston melts away completely shot my crank from having alluminum down in there eating the bearings away. with a forged piston my ignorance to airleaks just seized the piston withoug melting the exhaust side away.

But this is def some interesting inforation

 

[joeak47]

The thing that gets me is the differences in running temperatures. That really blew me away! Ive had great luck with cast pistons. Always have. I think I'll be keeping this one in there.

 

[Awk08]

The thing that gets me is the differences in running temperatures. That really blew me away! Ive had great luck with cast pistons. Always have. I think I'll be keeping this one in there.

what do attribute the higher temps from the forged piston too ?
possibly the higher compression/tighter squish ?
did you check the compression of both ?

 

[joeak47]

Can you explain this ring seal theory on the cast pistons. I dont see how they are different. Im sure they are but would like to be informed.

the keystone type or semi-keystone type ring prevents ring sticking. These rings are flat on the bottom and have a slight taper on the top. The added benefit is that they have a taper on the top,and so does the piston ring groove. These two surfaces act against each other as two incline planes,helping force the ring agains the cylinder wall on the down stroke (power stroke). This plus the high pressure combustion gasses getting behind the ring work together to force the ring against the cylinder wall.

The wiseco's use a thinner rectangular type ring. This ring can be installed either side up,because both sides are the same. It has the advantage of a little less drag on the cylinder wall because its thinner.

 

[Brute71]

the keystone type or semi-keystone type ring prevents ring sticking. These rings are flat on the bottom and have a slight taper on the top. The added benefit is that they have a taper on the top,and so does the piston ring groove. These two surfaces act against each other as two incline planes,helping force the ring agains the cylinder wall on the down stroke (power stroke). This plus the high pressure combustion gasses getting behind the ring work together to force the ring against the cylinder wall.

The wiseco's use a thinner rectangular type ring. This ring can be installed either side up,because both sides are the same. It has the advantage of a little less drag on the cylinder wall because its thinner.

also because of the thinner ring there's less weight which means the rings wont flutter as soon

 

[Blaner]

ok hang on, you said you installed both cast and forged with the same tolerance of 0.003? well that right there is the reason for your variances,

forged pistons due to their tendancy to expand unequally (agreed) need to have a slightly bigger tolerance to accomodate this, running one at clearances which are the same for a cast piston will result in higher running temperature as the piston expands and increases friction between the skirt and the cylinder, this is the reason for the louder sound; hotter running temp;decreased power (drag) and the scuffing. while the cast piston was free to do what it wanted with less friction.

You need to run this test again with cast at its correct clearance, then with the forged at the right clearance.

your results are flawed in that regard.

 

[best]

It is going to be very hard to get an apple/apple comparison here with clearance and quench being questioned no matter what you do. I have run both Wiseco and various cast in my KTMs for years. From the experience, I do feel there is a power advantage to the cast pistons. I have never broke a skirt on the KTMs so I am perfectly fine with the cast pistons.

As for the press test, not really a fair measure. It is like testing a soda can against a waterglass. The cast piston is rigid and brittle, but generally strong enough to do the job and retains shape well. The cast piston also supposedly slides with less friction due to the metal structure and make up.

The biggest thing that worries me with the Blaster piston is the windowed skirt being weak. Having had many cracked and broken ones, a more ductile piston may be a good idea. I think excessive rpm & clearance may be an issue with skirt breakage.

Rock on Joe! You don't learn without trying.
You can shim the basegasket to get the same quench if you want, or I guess you could do the head.

 

[Blaner]

It is going to be very hard to get an apple/apple comparison here with clearance and quench being questioned no matter what you do.

i disagree, it is a basic fundamental of any engine building - fit your piston with the correct clearance depending on what type of piston it is. if you dont, you will suffer consequences such as shortened lifespan, premature scuffing and heat siezes, shattered skirts etc.

its a fundamental which seems to have been ignored in this test? the pistons are not running at the optimal potential

however, its good to see guys thinking and testing.

 

[slickerthanyou]

On Weisco's the rings have a letter and number on them -N75 as an example-, and are suppose to face UP! I remember a WSM cast piston being 10 degree dome as the weisco's are 11 degrees.

I like seeing guys try stuff!
I choose Wiesco only because of the carnage that has happened to be with cast! However, now that I think about it, if the forged skirt breaks off then that chunk usually puts a hole in the case! either at the bottom or the balancer gear side.

I say that if you check compression/air leak test a few times a season, (or when a power isssue arises), you will be good!

 

[joeak47]

The wiseco piston has a recommended clearance of .002 (thousandths)

The WSM piston has a recomended clearance of .0028 to .0035.

I set the wiseco an extra thousands on the loose side,and the cast in the middle of the recommended range.

I've had a wiseco set at .004,and .005 before this comparison test and it still showed some very minor scuffing. They also got a bit noisier. That grey area thing I suppose. I think all pistons can get a wee bit of scuffing reguardless of the piston type,just nobody pulls the top end apart to see,because the engine is running good. This same wiseco top end was pulled apart twice for inspection and showed the tiniest amout of scuffing,and I'm talking negligable,however I was running the blaster in 80 degree to 87 degree weather. The wiseco tended to swell a bit more in the high 90's to 100 degree plus weather. Still ran awesome! If I wouldn't have torn it apart again,I probably wouldn't have even known.
I do know that the cast piston retains they're shape better when hot,and the ring seal works great.

I'm not saying that wiseco pistons aren't good pistons,because they're great pistons. I've ran them. I'm just saying that they're not the ultimate weapon. They handle detonation much better,but then again,proper tuning is a must...right?

I'm also saying that cast pistons aren't as bad as everybody thinks. Everybody gets into the histeria,and gets it engrained in they're head that a mushroom cloud will roll out from under your fuel tank if your not running a forged piston. Pure bunk. As for manufacture's running them,because they're "cheap"... think again. They're products have a reputation to uphold... Honda,yamaha,KTM,etc,etc. They wouldn't sell very many bikes and atv's if they're products blew up right after warranty. If these manufature's ran forged pistons from the factory,they would probably unleash complete hell on they're warranty departments,because of all the people that don't read they're manual about break in,warm up,proper jetting,lubrication,etc.

I could see someone gong down to a dealership to purchase a new atv,or MX bike,and bringing it back the VERY next day because it locked up because it wasn't warmed up before riding. A forged piston wouldn't increase the cost of a new bike that much if they were installed at the factory... They're only about $30 more (retail for us) than a cast piston. The manufactures did this for a reason... the cast piston is more forgiving against improper warm-up,is quiet,and just plain works good. Bikes are jetted for sea level altitude from the factory too. This covers the manufature's on the jetting issues. Remember that proper lubrication,warm up, and clearances are important!

wiseco recommended clearance

This is the "Old School" instructions that wiseco use to include with they're pistons.

The other half of the "Old School" wiseco instructions...the good old days!

 

[joeak47]

As for the press test, not really a fair measure. It is like testing a soda can against a waterglass. The cast piston is rigid and brittle, but generally strong enough to do the job and retains shape well. The cast piston also supposedly slides with less friction due to the metal structure and make up.

I thought this test was cool...very cool,but....

I run my pistons in an engine not a press,and I run the right side up,not sideways.