Author Topic: Do Forged Pistons Guard Against Cold Seizures?  (Read 311 times)

Steveog

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Do Forged Pistons Guard Against Cold Seizures?
« on: November 07, 2019, 01:51:07 AM »
This may be a bit theoretical, but was wondering if anyone has empirical evidence of Forged Pistons (Wossners) being less prone to cold siezures?

My thinking is that because the forged slugs take a bit longer to come up to operating temp, that gives the cylinders a chance to expand under heat and...less chance of a cold seizure.

Usually, our season is warm enough to be unconcerned, but this winter, I plan to run the 3xv for suspension and brake tuning.

I’m not running a thermostat and my shop is barely heated.

Any thoughts?

Thanks
« Last Edit: November 09, 2019, 02:26:37 AM by Steveog »
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SeaR1ck

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #1 on: November 07, 2019, 02:31:28 AM »
No they are more likely prone to cold seizures. They need proper warm ups they expand more then a cast piston does. Part of why usually forged pistons are sold as one size fits all and cast pistons you can get in slightly different sizes to match your A B C D cylinder.

So take extra care to warm up your forged pistons properly. If you do not warm them up well enough you'll start getting vertical scratches on your piston and cylinder walls  . Most commonly around the exhaust port area.

Also the colder weather will make your bike run slightly leaner. Because of the denser air it's getting more air and less fuel vs hotter thinner air which means lesser air more fuel.

« Last Edit: November 07, 2019, 02:38:03 AM by SeaR1ck »

mellorp

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #2 on: November 07, 2019, 10:59:55 AM »
Cold seizure is caused when the barrel and piston have a high temperature difference. However the reason is thermostat related. The thermostat (shut) holds back all the coolant making the initial warm up quite quick. However if you then set off and the engine temp goes up to allow the thermostat to open, it does so quite quickly, dumping all the cold coolant into the cylinders. The cylinders then cool very quickly, but the piston is still hot. Hence a cold seizure due to disproportionate component temperatures. Also called a 4 corner seizure on older cylinders where the studs go all the way through the barrels, giving yet another material (the stud or head bolt) that expands at a different rate

The tolerances of piston and ring  to barrel clearance allow for the cold components to expand to the correct size when the temp gauge is around 55 to 75 degrees. I don't know what temp the working surfaces are at but I suspect they are an awful lot higher

Remove the thermostat and this stops the "cold coolant" flowing so a cold seizure is much less likely.

Even warming the engine properly if you ride on a cold day the thermostat will open and close causing rapid coolant temp changes. This is usually OK on the road where engine speeds and engine temps are lower, but on a circuit you have more extremes and hence the higher risk of engine failure

That's a very simplistic explanation but it sort of gives you the idea of how complex the entire process is for engine designers to fathom out :-)
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Martin77

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #3 on: November 07, 2019, 11:37:47 AM »
I agree with what Phil says, though in my experience themostats open/close progressively (there's often a chart in the manual showing start temp and full open temp for the stat). The only bike I've owned that did the sudden dump of cold coolant after initial warming was a 350YPVS. I prefer to run a thermstat as it keep the temp at a more consistant level, but that's on the road.

Eitherway, what you need Steve is good old fashioned duct tape, cover the rad with it to help it warm up and keep it warm. You may need to experiment as to how much you'll need, just keep a close eye on the gauge and shoot for 60ish degrees..

yanw

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #4 on: November 07, 2019, 11:49:58 AM »
I recall Paul removing the thermostat on his 3XV-GP. He went out in a cold morning in Wales and was ok until he backed off and a cold gust of wind came from the side causing a cold seizure. It will be in one of his build threads.

mellorp

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #5 on: November 07, 2019, 12:48:01 PM »
Paul's 3XV GP is now in my ownership. Moral of the story is don't go out when it's cold and don't back off :-)
Mellion say If it ain't broke thrash it until it breaks

yanw

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #6 on: November 07, 2019, 01:54:43 PM »
Paul's 3XV GP is now in my ownership. Moral of the story is don't go out when it's cold and don't back off :-)
;D

Martin77

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #7 on: November 07, 2019, 03:39:42 PM »
Or fit a thermostat.  ???

mellorp

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #8 on: November 07, 2019, 05:07:47 PM »
Mellion say If it ain't broke thrash it until it breaks

Steveog

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #9 on: November 08, 2019, 01:32:27 AM »
Thanks gentlemen. Outstanding answer(s).

Rick - I had some vertical markings on my cylinder wall (that didn’t seize) back in August. I’ll have the cylinders off this winter. Will look close for the streaking you mentioned.

Yan - I read all of Paul’s build. In fact, it was his cold seize that promoted my question. Quite a disaster after all that work. Gotta admire his perseverance.

Phil - Great technical info. Lots of work in the writing. Plus, you and Martin agree.

Martin - I’m convinced. Twice. HA. Get a thermostat. Hoping to find one that can be fitted in-line, as the engine bay has been modified extensively. Don’t wish to return to the Yamaha jungle.

All - Looks like I’ll need to add another item to the winter maintenance.

My best to you all.

Steve
Brief, fleeting Glory. Which of itself cannot last, but while it does is the greatest game of all.

SeaR1ck

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #10 on: November 08, 2019, 02:42:48 AM »
I believe you could have a housing machined to fit the thermostat inside of it. Kind of similar to what TM is doing with its new tpi 250/300 smokers.


Steveog

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #11 on: November 09, 2019, 02:25:12 AM »
Thanks, Rick. That looks like what I need. The thermostat itself needs to open consistently over a certain temp range, I’m thinking it should start about 50C.

On the last track day (no thermostat) it was hot and humid. I did use some gaff tape* on about 1/4 of the rad’s surface area in the first session, but the bike ran around 80C, so I pulled the tape and it stayed steady at 62-65C for the rest of the day.

This new mod would be for cool air testing only, but I’m convinced it’s good insurance against a cold seize.

Steve

* Gaff tape is made for the film production industry. It’s formulated so as not to leave a gummy residue or pull paint from walls or others surfaces. Expensive, but better than trying to clean the adhesive out of those tiny radiator grooves.
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tzr-v4

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #12 on: November 09, 2019, 08:03:09 PM »
Plenty of inline thermostat...
https://www.meziere.com/Products/Cooling-System-Accessories/Inline-Stat-Housings.aspx

This is easy to test on very helpful.

Olivier.
Olivier.
TZR250 2MA & 2XT, RD500s et TZR-V4 building...

Steveog

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #13 on: November 09, 2019, 11:24:37 PM »
Thanks, Oliver.

It was just made apparent to me that I will need two thermostats, as I’m running a TZ Radiator with hoses running independently to both heads.

Regardless, good sources.

Steve
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tzr-v4

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Re: Do Forged Pistons Guard Against Cold Seizures?
« Reply #14 on: November 10, 2019, 01:45:57 PM »
I'm studding a new water pipes system on the RZ500 if we go to individual heads.
I believe that keeping the thermostat is the think to do so I look the individual ones to do the trick.
On the RZ500, the thermostat is reducing the hot water flow going back to the radiator (on the top of it).

Olivier. 
Olivier.
TZR250 2MA & 2XT, RD500s et TZR-V4 building...