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View Full Version : 86 Pistons Pics - Would you use them with a supercharger or turbo?



Matt
18th August 2012, 04:56 PM
http://images.thecarconnection.com/lrg/subaru-d-45-2-0-liter-boxer-four--2013-subaru-brz_100371873_l.jpg

Pistons
http://www.avoturboworld.com/images/stories/2012/brz_piston/brz_piston_001.jpg

http://www.avoturboworld.com/images/stories/2012/brz_piston/brz_piston_002.jpg

http://www.avoturboworld.com/images/stories/2012/brz_piston/brz_piston_003.jpg

http://www.avoturboworld.com/images/stories/2012/brz_piston/brz_piston_004.jpg

Thanks to http://www.avoturboworld.com for the pictures

Definately a piston top I'm not used to seeing and it appears to be a pretty strong design... Though how much boost is too much for a FA20 engine to handle?

Matt
8th September 2012, 10:51 PM
Here is a disected view of the piston from the side... Still not much word out there of lunched engines due to boost.

http://www.ae86drivingclub.com.au/dcimages/522538.jpg

davidgarratt
8th September 2012, 10:58 PM
Cool piston's, I see ART make them :D they are behind 4age cast pistons and also some HKS cast piston so you know thy are well made :cool: they are light also @ 22grams (if that's what the 22g stands for)

Frak
9th September 2012, 12:15 AM
ART make a good quality piston, lots of factory race pistons for bikes are made by ART, HRC have used cast ART's for decades and they don't have piston failures.

Vance
9th September 2012, 05:19 PM
now show me the rods.....



looks good. ill be planning on turboing or supercharging my 86 in a few years. hopefully i can get away with just thicker head gasket if the rods look as strong as the pistons. i want at least 1 bar FI.....

Matt
9th September 2012, 08:01 PM
Will see what i can find... There is already a company accelerated performance running 15psi on a stock engine..

Bullet superchargers have verbally indicated the engine is good for more psi than what they are currently running on their car, but they are treading slowly as they want to learn more about the direct injection.

Matt
11th September 2012, 04:57 PM
I love google...

http://www.ae86drivingclub.com.au/dcimages/5/3/4/9/400886.jpg

and

http://www.ae86drivingclub.com.au/dcimages/5/3/4/9/400888.jpg

Vance
12th September 2012, 04:10 PM
everything looks good. only issue now is trying to get the compression ratio down from 12.5 to 9.5.....


those con rods look awesome. press split so each big end cap is matched to each rod. very nice

rthy
12th September 2012, 11:26 PM
Should be interesting,
here is a 2.0 TDI D4D piston
http://i.ebayimg.com/00/s/NDAwWDMwMA==/$(KGrHqR,!m!E-rGnGg8LBPsfwCjZMg~~60_12.JPG
the swirl pot seems alot deeper, wonder if a turbo petrol version would need a deeper swirl pot too

Hopefully in due time subaru will just piff out a turbo model

Jimmee1990
13th September 2012, 01:29 AM
The bowl is a lot larger in those subaru diesel pistons because that's the whole combustion chamber, the head face has very little bowl if at all from memory. I'm sure in time a factory turbo version is inevitable.

Vance
13th September 2012, 04:08 PM
the brz sti coming out in 2013 will not be turbo according to subaru

Sam-Q
16th September 2012, 12:06 PM
That is the single best piston design I have seen for any factory engine. It has multiple really good features built into it. No wonder they can handle such a high compression ratio.

Any have a combustion chamber pics?

Matt
17th September 2012, 08:07 PM
http://www.ae86drivingclub.com.au/dcimages/5/3/4/9/538294.jpg

Sam-Q
17th September 2012, 08:21 PM
thanks Matt/ Now I can see why this can run such high compression. This would be a very detonation resistant chamber. I can explain many of the different features shown here if people want.

Matt
17th September 2012, 09:18 PM
Yep I'd appreciate it...

briigo82
3rd October 2012, 04:16 PM
So would I. Explain away...

Sam-Q
5th October 2012, 10:10 AM
alright if I remember I will write my observations on the weekend

Sam-Q
16th October 2012, 11:30 PM
alright where to start...

now this is going to be a long winded summary of info I read or I am working out myself from what I can figure out. If someone can add something or correct me then go ahead.

Base piston and pin design:

- This design of piston is unlike the convention in that it's what's refered to a "slipper" design. This doesn't feature a piston skirt all the way around but rather has it at full length where it has the forward-aft movement and not and the sides where there is trivial rocking force. The skirt design therefore intersects the pin support right where the end of the pin is. Using a conventional design extra material has to be add not only to the sides of the pistons to distribute the force into the pin area but also the piston crown as the distance between it's supports is a greater span. The reduced skirt contact area also reduces total drag on the engine.

- Art has gone to the extra trouble of removing material wherever it wasn't needed, small areas like between the gudgen and the crown has an indent all to remove material.

- The bottom of the piston has the shape follow the countour of the gudgen pin support, this reduces any un-neccesary skirt length which further reduces weight and also drag.

- Although pretty much standard these days the oil ring grouve has drilled lubrication holes, some earlier more primitive piston designs had a slot which is quite a weakness.

- Features a special coating on the contact surfaces of the skirt.


Crown shape and chamber:

Now this is a tricky one to explain. I am not familiar with the progress of detonation in a direct injection engine as it tottaly changes one of the initial causes.

Alright- ideally the combustion chamber would be the smallest sphere possible with the ignition in the dead middle. However this has to be altered to suit the other conditions of the engine. The basic theory is the same though- the smaller and more isolated the chamber is the better. When a combustion chamber is larger it increases the surface area of the combustion event. This then causes more heat loss, less proper burning and on externally injected engines encourages uncontrolled preigniton and dual flame front collision from the outer edges to the main firing. This is one of the big reasons why 5 valve engines have quite the disadvanatage compared to 4 valve chambers. The chamber is narrowed right down with the use of the quench zones which I will get to shortly. The combustion zone recess in the piston has also been shaped in a triangle shape which is quite clever. This is matched to the path of the fuel discharge of the fuels direct injector. So the theory would be that the fuel is pushed evenly and completely across the entire combusion zone.

Now the really sneaky trick with the crown design is the angled quench areas. This is what was previously F1 tech only. If what I read is correct Cosworth was the first company to introduce this in a mass produced engine (motorbike). It's quite a task for a manufacturer to impliment this feature as the piston needs to match a 3d shape of the chamber to a very tight clearence. The gains however in such a design are clear. In a conventional chamber the quench zones are the flat machined areas of the head, the gasses are pushed out into the chamber area and are cooled down- hence the name. However with an angled quench zone the air is pushed directly into the middle of the head- right where the spark plug is. This would also stop the injected fuel overshooting the chamber and being unburnt in the quench area or the exhaust valve pockets increasing emmisions.


There... comments anyone?

Matt
18th October 2012, 08:14 PM
Thanks for that sam...

ill-minded
20th October 2012, 12:22 AM
I feel like a big nerd for understanding all of that and having prior knowledge of tapered squish areas. I've actually got a technical paper done by Mitsubishi on the effects of tapered squish pistons.

Matt
20th October 2012, 06:07 AM
Throw up a link ill-minded... I'm keen to learn more about this kinda stuff

ill-minded
20th October 2012, 12:31 PM
I don't have a means of hosting files, but I'm happy to email it to someone with some web space. It's about 5mb. I guess I could throw it up on a file hosting site, but I've got no idea which ones are preferred/better.

Matt
20th October 2012, 01:27 PM
http://www.ae86drivingclub.com.au/downloads/pistonsquish.pdf

There you go fellas...

Matt
20th October 2012, 07:37 PM
Linked it up above...

Sam-Q
22nd October 2012, 09:49 AM
awesome I am going to have a good read of that later. My suggestion for anyone who wants to know more is to read this book:

"Four-Stroke Performance Tuning" by A Graham Bell

sprinter666
14th December 2012, 02:34 PM
insane reading cheers guys, man should invite u guys to a bbq, the insane technical discussions i wouldnt understand would blow my mind no doubt.

Sam-Q
14th December 2012, 04:25 PM
If it's on a Sunday or weeknight then yes sure. If you want to cop it till your ears bleed ask me about 2 stroke tuning!

ill-minded
16th December 2012, 06:30 PM
Some more interesting pictures of an FA20 internals.

http://ameblo.jp/scorch/entry-11424068734.html

Skylar
17th December 2012, 12:43 AM
Didn't read that scientific paper on piston shapes. Looks interesting but no time now. Got a few things to add. Haven't read the rest of the thread either so I apologise if I'm repeating stuff.

A combustion chamber with good squish properties can be the cause of knock when turbo'ed with high boost. Due to the increase charge density in the combustion chamber fromn the turbo, the "jets" from the quench pads causes the charge to swirl too quickly and cause a separation of flamefronts which results in detonation. That's my understanding of the subject. Someone correct me if I'm wrong.

Some engines don't like quench pads and swirl. One engine builder went the other (put the piston further down the bore while maintaing comp ratio) and got more power for some reasons he still can't explain. It was only that specific type of engine though. The guy does use quench pads as much as he can on all his engine builds. The CC looks to be pretty open and the piston doesn't have a slanted squish band.

Is there a reason why a GTX2867 was used over a 2871 for that build above. 2871 would have done the job just fine since it isn't running super high boost which I though was the whole point of the GTX series or wheels. It's a little more efficient but I dunno if it's worth the extra cost for non-competitive guys like us.

Matt
20th May 2014, 02:33 PM
Found these on the web...

A fa20 engine pulled apart and lots of good pictures.

http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47220.jpg
http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47225.jpg
http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47235.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47231.jpg




http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47228.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47232.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47234.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47252.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47238.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47236.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47239.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47245.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47246.jpg
http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47248.jpg
http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47237.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47253.jpg


http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47256.jpg




http://www.revvolution.com/image/albums-b-5o9-rj-r8-0/revvolution-project-brz-fa20-4ugse-teardown-and-assessment-47258.jpg

Matt
20th May 2014, 02:38 PM
And also these

http://www.revvolution.com/image/albums-b-5q7-rj-r8-0/revvprojectbrz-fa20-engine-tolerances-49869.jpg
http://www.revvolution.com/image/albums-b-5q7-rj-r8-0/revvprojectbrz-fa20-engine-tolerances-49867.jpg
http://www.revvolution.com/image/albums-b-5q7-rj-r8-0/revvprojectbrz-fa20-engine-tolerances-49870.jpg
http://www.revvolution.com/image/albums-b-5q7-rj-r8-0/revvprojectbrz-fa20-engine-tolerances-49873.jpg
http://www.revvolution.com/image/albums-b-5q7-rj-r8-0/revvprojectbrz-fa20-engine-tolerances-49875.jpg

Be sure to check out the source Here (http://www.revvolution.com/blog/Platform-Series-Subaru-BRZ-Scion-FRS) for the full article / many more pics