11882 ultra stroke wiseco pistons, option for +4mm stroker?

[graham heise]

Been looking at options for a +4mm stroke crank to use with 31k cylinders. From research i thought the non base spacer option piston was the 795 wiseco with raised wrist pin. I found these 11882 ultra stroke pistons listed. from the sellers description this may be an option ?? different piston crown angle of 13 degrees?? anyone here used this option?

https://www.ebay.com.au/itm/2-x-Wiseco- ... 1333124157

This is seller description
Introducing ULTRA STROKER pistons from Wiseco designed by engine builders with 20 plus years in the industry



One of the definitive ways to get more power from your Banshee is by increasing the stroke of the engine.



This is a pair of BRAND NEW Wiseco forged ULTRA STROKER pistons.



These pistons are custom made by Wiseco (part number 11882)

They allow you to run a 4mm stroke long rod crank (58mm stroke 115mm rod) –

The stock banshee head will require a .060” base gasket to work properly. I also offer the .060” base gasket as well.

Availability is 64.00, 64.50, 65.00, 65.50, and 66.00mm sizes for your cylinders



These are Wiseco forged pistons that takes all the good features to make much more power than Blaster pistons:

- The piston domes are 13 degrees - so you can run a stock banshee head (must use the .060 base gasket)

- a Blaster 573 piston has 9 degrees, so the squish is not optimal when using a stock Banshee head.

- 6mm pin offset location - compensated for the increased stroke and rod length

1. The raised intake windows allow the piston windows to be fully open at BDC. (Unlike the blaster piston, in which they are mostly closed at BDC) - Please see the last auction photo for a visual between an ULTRA piston (left) and a BLASTER piston (right)



Why use ULTRA STROKER PISTONS?

You have a stock bore banshee, and you don't want to bore it .080”over to the last bore just to run Blaster pistons (Blasters are 66.00mm or larger)

You don't have to re-cut 9 degree Blaster dome for your Cool Head or re-cut your stock head (we also sell 13 degree ultra stroker domes that are bolt on - the only modification with a Pro Design Cool Head is our custom CNC cut dome and using a .020” base gasket instead)

You don't want to run a spacer plate, the transfer timing will be out of specifications, above 135 crank angle degree.

[Questo vecchio rz]

Interesting..never heard of that until I read your post

[JonW]

Nor me, sounds good from what you out up, interested to hear from someone whos used them now.

[EE]

Now if only there was a substantial amount of airflow at BDC.......

[graham heise]

From a bit more research the 11882 piston has a 6mm offset pin like a blaster piston but is made in smaller sizes. Ie 64mm up compared to the blaster that starts at 66mm oversize. The 795 piston has a 5mm offset which protude an extra 1mm into head. Maybe this 11882 piston is closer to a plug and play with +4mm stroke crank with the long rod then the other options. Cylinders and head would still need work for optimal results.

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[T.RexRacing]

Now if only there was a substantial amount of airflow at BDC.......

Care to dive a little deeper Ed? Any relief for that?

[EE]

I was lucky enough to have a group of world class tuners help me design the pistons for my RD250 LSR bike, I can be a pain in the ass because I question everything trying to find every last bit of advantage, in the beginning there were some certain ideas about when the most airflow was needed but in the end the engine simulations showed us this:
1)Starting at BDC the piston rises 30deg to 210deg or rises 2.786mm and intake flow starts
2)intake flow peaks at 315deg or 45deg before TDC or 9.578mm before TDC
3)From there intake flow tapers off as the pistons passes TDC and ends at 45deg ATDC or 9.578mm down from TDC
Now good pipe dynamics can stretch things a bit but there is not much airflow going on at BDC... so... if you set the windows higher to be open at BDC then the skirt actually starts to close the intake as it rises when you really want it open... basically you want to get the skirt out of the way as quickly as possible and keep it out of the way as long as you can... except at BDC when not much airflow is going on.. just sayin..

[T.RexRacing]

Thank you.

[Questo vecchio rz]

Question, does this data transfer the same or closey from the cylinder/piston design of the 70sAC RD250 to a next generation 1980s
YVPS 350 cylinder/piston design ?
Or is the initial claims of the aforementioned piston design for the YPVS/Banshee possibly have some validity?
Just asking
Thanks for any insight, merry XMAS by the way.

[EE]

How you should phrase that is "does the data from one cylinder reed engine transfer over to another of similar design?" An engine doesn't care what year it was made thank goodness or my "70's aircooled RD250" wouldn't be making the hp it does lol!!! To answer your question there just isn't or almost isn't any intake airflow at bdc...

[graham heise]

Then why put the ports there. Was your 1970's tuned 250 running a +4mm long rod stroker crank. If it was where did the pistin windows end up?

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[EE]

The stroke of the crank is not the issue. The issue is that regardless of crankshaft stroke there is little or no intake airflow at bdc of a two stroke engine.

[Questo vecchio rz]

The issue is that there is little or no intake airflow at bdc of a two stroke engine.

Interesting.....That's the kind of response I was hoping for ,as I was curious of your opinion of it it we're "all" 2 stroke engines or just "various incarnations".

I'm no engine designer/engineer, but as you, I enjoy and learn by questioning everything... so that I make a decision based upon what factual/ definitive information I learn from others. I enjoy the bench racing and watching ideas on paper pan out in real world results. I can add this to my engine notebook for funday reasearch

Thanks