# anyone fitted WOSSNER rs4 pistons in a vr6 engine?



## adaptorman (Dec 12, 2007)

reason i ask im sure they would fit 
as the 2.7 bi v6 turbo uses 81mm pistons 
21mm wrist pins
rods are 154mm long 
8.0:1 compresson
wrist pin bushers wouldnt be a problem to replace 
only things i worried about are piston block angles between rs4/vr6
im sure they will work ,reason i ask is got a full set cheep

reckon with arp conrod bolts should have a decent 400bhp engine if the pistons will run in the bores?

anyone know which way these rings fit ,as there differnert colours i.e black/silver and been told rings need to be set at 120deg fro each other as couldnt find any correct info. as im temptord to give it a try


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## GinsterMan98 (May 19, 2008)

well, I do know that the rings on a VR6 have to be set at 120 deg per the bentley. Not sure if this will help you though.


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## Rheinland Technik (Apr 2, 2010)

VR6 Pistons, though 81 mm in diameter, have 20 mm wrist pin diameters and are made to fit 164 mm center to center rods with a 90.3 mm stroke. The compression height is 1.275 +/- and have an angled top with valve reliefs made for the VR6 head. Using the 2.7 pistons would not really be worth trying.


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## adaptorman (Dec 12, 2007)

hi cheers tbh i dont understand some of the techical figures , im unsure why these wouldnt be worth useing ?, 
is it the pistons them selfs that are the problem or wrist pin bushers, 

i built a vr6 lump with a block rebore useing audi v6 83.01m pistons with 21m conrod bushers and a 2mm headspacer , with no piston/compression head problems,until a crank bearing spun which shows 8 on the compression tester)



as ive another option is use 154mm rods 21mm conrod bushers and mk4 r32 crank?


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## adaptorman (Dec 12, 2007)

GinsterMan98 said:


> well, I do know that the rings on a VR6 have to be set at 120 deg per the bentley. Not sure if this will help you though.


nice very helpfull 
also found which ring fits were too


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## adaptorman (Dec 12, 2007)

on the left is a stock vr6 piston on the right is the rs4 wossnerr piston , not mutch differnce , but the wossnerr has a deeper dish on the top then a vr6 piston


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## filthyeuropean (Sep 23, 2006)

...or you could buy VR6 pistons and do it right..


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## adaptorman (Dec 12, 2007)

correct , if was to pay 789 pounds for a set of ebay, or fit these for 200 ,, has to be worth a try/attempt


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## 1SlowSLC (May 4, 2003)

Im not an engineer, but just looking at those pictures...let's say you get the pistons to fit and everything works mechanically(bottom end rotates freely etc).... You still have shorter pistons, with a bigger dish.You want to put pistons designed to run in a straight perpendicular bore into a bore with a 15 degree v where the pistons are angled to not stick out on one side of the deck of the block. I just think it would be a major mess. It would probably drop compression too low, increase volume of the cylinder,and the combustion process would probably be thrown off by the valve reliefs being in the wrong place.It'll be hell to get the motor to run right, even with standalone management it would be a task to tune it right. The woessners are not designed for that motor. If it was so easy to throw any old piston in any motor, you would see people doing it all the time.

Now, I can say I've seen and read about the other odd combinations you threw together that worked. So it might be possible to make it work, but I think it wont be worth the time, effort and headache. Keep stock pistons in there, or sell off the woessners and use the money towards a set of proper, made for vr6 forged pistons. I'm a machinist, but that doesn't mean Im going to go buy a chunk of metal and machine my own pistons cuz it'll save me money. Its about having a correctly designed and engineered part so your motor runs like its supposed to.


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## adaptorman (Dec 12, 2007)

1SlowSLC said:


> Im not an engineer, but just looking at those pictures...let's say you get the pistons to fit and everything works mechanically(bottom end rotates freely etc).... You still have shorter pistons, with a bigger dish.You want to put pistons designed to run in a straight perpendicular bore into a bore with a 15 degree v where the pistons are angled to not stick out on one side of the deck of the block. I just think it would be a major mess. It would probably drop compression too low, increase volume of the cylinder,and the combustion process would probably be thrown off by the valve reliefs being in the wrong place.It'll be hell to get the motor to run right, even with standalone management it would be a task to tune it right. The woessners are not designed for that motor. If it was so easy to throw any old piston in any motor, you would see people doing it all the time.
> 
> Now, I can say I've seen and read about the other odd combinations you threw together that worked. So it might be possible to make it work, but I think it wont be worth the time, effort and headache. Keep stock pistons in there, or sell off the woessners and use the money towards a set of proper, made for vr6 forged pistons. I'm a machinist, but that doesn't mean Im going to go buy a chunk of metal and machine my own pistons cuz it'll save me money. Its about having a correctly designed and engineered part so your motor runs like its supposed to.



hi yes i do understand what u mean , im personly going on the last 2 engines one had stock vr6 pistons skimed flat again ran fine 20psi , with one piston blow due to injector failure, so i do think they will run fine , again the lastist moter the pistons were from a v6 12 audi 83.01 again no probs at all other then poor crank bearings , or possible streched conrod bolts , , as im conveniced it will work , as if stock skimed pistons were fine and stock v6 audi 12v pistons were fine , for what they cost ill thow them in ,,


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## GinsterMan98 (May 19, 2008)

Well, I agree with most of what you said about not knowing the actual compression these will give him. On the other hand putting pistons from another engine into another one is not new. For example, Honda guys run Suzuki Vitara pistons in D series engines all the time. They are the like 1 or 2mm larger bore, but give a lower CR so they don't have to deal with head spacers and such. These are OEM parts for the Vitara and guys have made well into 600whp range with this setup. Oh and they are cast. In defense of what you said though you did bring up a very valid point. These pistons are not designed to run in a 15 deg bore. The Vitara pistons are almost the same as OEM Honda ones except they are shorter and both are inline four bangers.

OP, the best bet is to do the math. Take the pistons to a machinist and have him determine the dish volume and figure out what the diffrence is going to be vrs stock pistons. You can also use a MK4 head gasket to bump the CR up .5 or use a MK3 gasket to lower it .5, so you can play around with the CR alittle. If you go with it make sure you clay the rotating assembly.


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## MarcoVR6SC (May 3, 2003)

It will probably work, although I wouldn’t do it.

The 15° angle is not really a problem(if as said there’s no mechanical interference), because cylinder pressure is pressure and it doesn’t care about the piston’s shape, only for the diameter. 

One thing is that you won’t know what the CR will be, and second, this is where the shape of the piston does matter, the engine could run less effective(VE) and heat the piston more than the original(the piston is also cooled by the head when it reaches TDC, which is one reason the VR6 piston has it’s specific shape).


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## adaptorman (Dec 12, 2007)

cheers guys tbh ill fit these and fire it up on the floor run it for a while then check cr , going on ring lands compaired to vr/wossnerr i do reckon i will need a 2.5mm spacer which i do run on my old 83.01 audi 12v v6 pistons from a 2.8 engine which gave me a 8 when tested which i was happy with
i could just fit set of rods/bearings/crank and refit , but easyer this way , ill get these fitted and pop some pics up , as im just makeing new bearings at mo,


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## GinsterMan98 (May 19, 2008)

I like you bro, this is how things get done, balls to take a chance. So skimmed VR pistons held 20 psi? Thats very interesting to me because I was interested in this same idea about two months ago and most told be to just run a spacer. How much would you take away to have like 9:1? I will never run that much boost, maybe 15psi at most. Hit me up with a PM and we can talk about this more. G/L! and keep us in the loop.


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## GinsterMan98 (May 19, 2008)

> second, this is where the shape of the piston does matter, the engine could run less effective(VE) and heat the piston more than the original(the piston is also cooled by the head when it reaches TDC, which is one reason the VR6 piston has it’s specific shape).


This is the main reason people told me not to do it. Increased change of det due to removing the mass from the piston witch helps cyl cooling. My plan was to have a machine shop just increase the size of the dish without removing any material from the squish area, outer edges of the dish. You are also correct on the cooling benifet of this as some refer to this as free octane.:thumbup:


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## adaptorman (Dec 12, 2007)

yes pal hers a pic 








if it wasnt for injector going down it would have been fine 
other engine again similar design just wider dome bigger pistons 








this is why im convinced they will work , ive instailed one , and happy with it


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## adaptorman (Dec 12, 2007)

just be carefull if u go this route as if u increese the centre dish , then look inside the piston you will found piston goes thin , hernce why i skimed the top , as this as not only been done on other vrs, also similar design on other pistons fitted into vr6s, ic arnt honstly say what happernds inside the chambers in boost , other then it works tbh


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## dub_slug (May 12, 2008)

This is very interesting, where can one buy a set of these pistons?

:beer: for your crazy ideas adaptorman! :thumbup:


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## GinsterMan98 (May 19, 2008)

You are a true BAFM bro!:thumbup: Its good to see this work in real life.


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## adaptorman (Dec 12, 2007)

some dont agree some do , but without trying ideas you,ll never know 
which pistons are meaning stock skimed , audi 12v or wossnerr pistons?
i have a brand set of audi pistons complete rings/rings but u need to buy conrod 21mm pins bushes (5.09each from dealers audi from the audi rs4 engine , from dealer have the info if needed , as most know mahle/mopisson are used in top engines


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## dub_slug (May 12, 2008)

What do I need to put these on stock or forged VR rods?


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## adaptorman (Dec 12, 2007)

just a set of of rs4 small end codrod bushers from audi dealers , either cut/remove ur old ones or have them pressed out and re fitted with 21mm bushers , theres also a fair amount of vws that use 21m bushers as stock
piston wise u can use stock rods on all of these pistons , id recomend arp bolts if ur going to run over 20psi to be safe


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## adaptorman (Dec 12, 2007)

pictures to follow fitted these rs4 wossnerr pistons in my vr6 block look/fit fine with 21mm bushers added


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## adaptorman (Dec 12, 2007)

well they fit decent , 
















added high beam rods/arp bolts , see how utch these pistons hold


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## adaptorman (Dec 12, 2007)

just a small update these wossnerr pistons are spot on so far in my vr6 t 
small afr video here runing obd1/converted 4pin maf,100mm tube with 640cc tunie 4bar

http://tinypic.com/r/nmdruh/7


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## GinsterMan98 (May 19, 2008)

Badass bro, this is cool stuff right here. Please keep us informed how they do.:thumbup:


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## GinsterMan98 (May 19, 2008)

Did you use a spacer with the RS4 pistons? what did you use as a headgasket?


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## adaptorman (Dec 12, 2007)

hi pal yes evern thow the rs4 piston were a 8 compression drop and use 154mm rod length,21mm wristpins
i bought audi rs4 wristpins pressed them into high beem rods.or stock rods which are 164mm in lengh i had to use a 2mm headspacer along with a multilayer heagasket, 
just done my first 600mile no rod or pistons probs as yet  runing 20psi on a holset hx35 12cm
http://tinypic.com/r/nmdruh/7


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## GinsterMan98 (May 19, 2008)

I want to see it on the road!!! So to recap you used stock rods, 21mm bushings in the pistons, and a headspacer to get a 8:0:1 CR. What thickness head spacer did you use???
*EDIT* 
2mm, missed that. What would 2mm give you on a stock setup?


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## adaptorman (Dec 12, 2007)

u can use other conrod bushers but ull find they come std at 20.5m ,which need to be internatly reeemed out to fit your stock conrods 21mm wristpins of the audi pistons , youd be looking at 10 without a spacer  dont think ill need this other set of pistons so ill ebay them , gave it a 20psi boost today , rather fun , better if roads were dry, just need a 2.8 4motion or tdi gearbox now as mine as a mk4 r32 which is too short and spins in every gear


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## VWallin (May 17, 2010)

Wow! That's just amazing. Is it still running without any issues? I'd love to se a video on the street
with lots of boost


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## adaptorman (Dec 12, 2007)

will do when i either short maf issiuse or reset issiuse on standalone as sorting ms unit to run right would save me a lot of hassle on re modifying the engine


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