9:1 JE pistons?

[JustinCase]

Does anyone know where I can get my hands on a set of 9:1 83mm pistons made for a 92.8mm stroke? I can only find 8.5:1 and 9.5:1 but I know people run 9:1 JE's?

[IVRINGS]

I don't think they have them. That is why I've been looking at different brands like Supertech and that M brand.

[JustinCase]

I could have sworn Ive seen 9:1 je pistons in a few peoples build threads.

[AudiHere04]

I had spoke to pete @ IE about getting 9.0:1 he said they had to get them custom made, and assured me 8.5:1 would be fine. Call up IE.

[IVRINGS]

I could have sworn Ive seen 9:1 je pistons in a few peoples build threads.

Maybe not 83mm, but I think stock bore they do have them.

[JustinCase]

So what the general consensus on 8.5:1? Does it affect low end that much to not be worth it? Does anyone have experience with both?

[B6Lovin]

Go high compression and bigger turbo. I want to see a DD 475awhp on pump at 15psi kind of car. That way when you do meth and 25+ psi you'll be more like 600+ lol

[JustinCase]

Don't think that hasn't crossed my mind. I was planning on going the safe way with the lower compression but I keep having reservations because I dont want to lose the low end power. I understand the pro's and con's of low vs. high compression but are there any big disadvantages to going with the 9.5:1? Im worried Its going to be tempermental and Im going to be constantly combating knock. Now is the time to make this decision because Im ordering them before Thanksgiving so I'm welcoming any input.

[IVRINGS]

I'm in the same boat. I try to keep telling myself to go 9.5:1 for the extra power since our stock is 9.3 so it is closer then a 9:1, but then I go well I can go safer and go 8.1:1 since I'm going 2008cc. Since I'm going to be K03 powered for a while I don't want to lose to much power till I go BT or BAT.

[Shayneduboulay]

I got my motor built and I went with Mahle 8.5:1 pistons with my K03(till the Agtronic Downpipe, Manifold and 5857 kit is finished being fabricated). There wasn't a BIG difference between stock and now. I was told that it would be best for my build. You should just go with 8.5:1 and be done with it. MORE BOOST!! lol

[IVRINGS]

I got my motor built and I went with Mahle 8.5:1 pistons with my K03(till the Agtronic Downpipe, Manifold and 5857 kit is finished being fabricated). There wasn't a BIG difference between stock and now. I was told that it would be best for my build. You should just go with 8.5:1 and be done with it. MORE BOOST!! lol

The problem with that is we would have more power with lower boost if we go 9.5:1

[SleeperAvant]

What about Wiseco? Don't they make 9:1?

If not, could one run 8.5:1 on a BT / BAT at high pressure and loads of timing to have a nice torque curve?

I got my motor built and I went with Mahle 8.5:1 pistons with my K03(till the Agtronic Downpipe, Manifold and 5857 kit is finished being fabricated). There wasn't a BIG difference between stock and now. I was told that it would be best for my build. You should just go with 8.5:1 and be done with it. MORE BOOST!! lol

Nice.

[B6Lovin]

You don't have to work the turbo as hard with higher compression... Think of it like this.

You can make x amount of power with say, 630cc injectors... But let's also say you're maxing out those injectors 90% of the time to do it. What would be your logical step to make things easier on the whole system? You go up to say, 830cc injectors.

In the same way, if you have te option to have better bottom end and not work your turbo as hard to make the same power you would at a higher boost and lower compression I'd do it. It's a win win

[1ScientisT]

I'm with B6Lovin... 9.5:1 is relatively timid in a naturally aspirated engine. The limited displacement of our engines makes for weak bottom end power. I say supplement that with higher compression pistons and leave yourself room to adjust boost up top. The 8.5:1 pistons will increase lag on that big ol' turbo and who wants that? It's way easier to adjust your boost than your compression ratio.

[JustinCase]

From what I understand though the 5857 likes high boost more though correct? So maybe I wouldn't be using it to it's potential at say 15 psi?

[JustinCase]

What about going all out and doing like a 9.5:1 6262 build? I'm not opposed to doing something different with this.

[dougyfresh]

From what I understand though the 5857 likes high boost more though correct? So maybe I wouldn't be using it to it's potential at say 15 psi?

why are you going with a 5857?

why JE? there are other piston manufacturers.

[JustinCase]

why are you going with a 5857?

why JE? there are other piston manufacturers.

I know. I'm not set on JE but I have read conflicting opinions on Supertech and I didnt find too much info on weisco and cp. Again this isn't set in stone so I value everyones input.

[SleeperAvant]

I'm with B6Lovin... 9.5:1 is relatively timid in a naturally aspirated engine. The limited displacement of our engines makes for weak bottom end power. I say supplement that with higher compression pistons and leave yourself room to adjust boost up top. The 8.5:1 pistons will increase lag on that big ol' turbo and who wants that? It's way easier to adjust your boost than your compression ratio.

From what I was told by Ray@RAI, you would need to supplement high compression (10 or greater) with a big turbo with water/meth. There is also a limit to the amount of boost you can run as well. A convo regarding their custom pistons:

....we are still working on it, but the pistons are available. The I beam rods may not be available as of yet, we will have to talk to IE about them. The pistons are special order at this point and are not stocked. Tuning with any software will require a lot of time to ensure safety and reliability. I would run about 18* timing and no more than 24-25 psi of boost pressure. This is assuming you have a proper water meth setup, the octane boosting properties of water meth injection will be required.
After the testing is complete we can release the dyno's. A 10:1 motor will increase spool time significantly, also off boost driving will benefit as well.

[B6Lovin]

if i were to do this all over again i can tell you one thing - i'd say fuck the bullshit small stuff, and go straight to a 6262, 40r, or larger on a 10:1 or higher stock bore/stroke and i'd cam/rev the ever-living hell out of it....

its all what you want though, i wouldn't want to daily drive anything much more powerful than what i have.. 450awhp is pretty much perfect on a daily, if it's just a weekend car i see no reason to not shoot for 550+ with it.

[JustinCase]

Wouldn't a higher CR DECREASE spool time?

[JustinCase]

Oh and as far as the turbo selection I was kind of jumping on the PTE bandwagon. What I would really like to do is go with either a Bullseye S259 or s362. I like their turbos a lot and a lot of companies swear by them (I.e. Autoxtrem). But I am a little afraid to go in a different direction and not have a shoulder to lean on so to speak.

[B6Lovin]

yes higher CR should decrease spool time. hell, if you could do a 2.0 or a 1.9 with a higher CR and still keep it safe for fast hard revs that'd be even better.

[JustinCase]

Well I already got the crank so 2008cc it is. How do you feel about 9.5:1 CR with an S362? I mean I don't plan on rolling around at 8000 rpms but i want to be ale to when I want to have fun.

[B6Lovin]

hell yes. that sounds like an extremely stout setup to me!

[A4SoftWalker]

I don't see what all the high compression fear is all about.
There are daily driven HPF M3's out there that slurp up 11:1 ratio with turbocharging to boot.
It is my opinion that the reduced compression frame of thought is quite old and with modern engine management systems efficient intercooling + liquid meth detonation can be controlled effectively.

[B6Lovin]

thank you.


high compression is the way to go.
so is mild porting/high velocity setups.... it's all about the power band. just ask anyone with a s4 (and they're right)

high velocity, high load, high compression, high boost, high timing, and shit tons of fuel. THAT is the recipe for a truly fast a4. you want lots of boost as soon as you can get it and as much power as you can get until it hits. we dont have much displacement to work with so you want to create a very heavy load on the motor as quickly as you can (a single mass flywheel is best IMO) and couple that with off boost power (timing, compression, and proper fueling) and then throw the mother load of boost fuel and timing into that ish and you've created a car that takes off like a freight train, doesn't take till 5k rpm to do it, and has enough off-boost response to be daily driveable at power levels of 450-500 without much issue. you'll have top end, bottom end, mid range, everything you could want from the car.

[nofearhawk]

I have 9.5:1CR CP pistons, 83mm, getting coated by swain tech. The block is getting decked and the head surfaced so that should raise the compression a little, I'm thinking it'll be closer to 10:1CR when all is said and done.

I'll let you guys know how it goes. The idea was to shift the graph left and get the turbo spooling sooner.

[JustinCase]

I think you have calmed my fears of 9.5:1. I was originally thinking it would be a bad idea but it seems like in this case different isn't necessarily wrong. I was looking for an excuse to go with a big ol turbo and I think the fact that it will spool sooner is reason enough for me. Unfortunately I'm going to have to go in stages here but hopefully this isn't going to turn into a Clint-esque build haha. Maybe its time to start a proper build thread?

[nofearhawk]

BTW I also had a CR thread going not too long ago:

http://www.audizine.com/forum/showth...ht=compression

It sort of just trailed off though but what I said in my first post appears to be correct.

Also, browsing in the other parts of the zine', the fsi engine has 10.5:1 CR and makes great power chipped and some of the b5 guys are running 9.5+:1 CR's as well. Not really uncharted territory.

[diagnosticator]

Remember that on a stroked build, if the stock bore and pistons was used, the CR would increase due to the longer stroke. So does the CR change/increase with a larger bore/piston size over stock. Just make sure you know what the actual static CR will be before you buy parts. Use the CR formula to find the original combustion chamber volume, the use the new bore/stroke numbers and the existing chamber volume to figure the new static CR. For example, a performance piston is listed as 9.5:1 CR, is that the CR on the stock stroke or ?. What combustion chamber volume is used to calculate the published CR?

[nofearhawk]

^ Good information, also most aftermarket piston manufacturers list the CR for the stroke that the piston will be used for so it makes it pretty easy since they did the calculating for you already.