# who runs higher cr pistons ?



## yohimbe (Jun 13, 2005)

I think IE offers a set of pistons which have 11:1 CR ratio, does anyboedy run such a combo with a chip upgrade ? I am just curious what hp increase they would be with a fine tune of the ecu.


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## easy cheese (Aug 3, 2008)

*Re: who runs higher cr pistons ? (yohimbe)*

i would like to know also ... http://****************.com/smile/emthup.gif


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## bimmerboy02 (Oct 2, 2005)

What about just using 2.0t pistons? Won't be as light as a nice forged, but much cheaper and 10.5:1


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## DRedman45 (Aug 7, 2009)

*FV-QR*

i am pretty sure the 2.0t pistons are slightly smaller than the 2.5


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## [email protected] (Jan 2, 2009)

The 2.0T pistons won't work in the FSI, the valve angles are different, so the notches are wrong. 
FWIW, I can do whatever compression ratio you guys like for the price listed for the 11:1... 11:1 or 11.5:1 is as high as I would go on pump fuel though.


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## yohimbe (Jun 13, 2005)

*Re: ([email protected])*

I think with a proper tune there should be a good gain in hp. 200hp should be made with a modern engine like the inline 5, it has all specs which are needed but the low compression ratio(which can be only a reason because of the bad fuel in the countries where the car is sold also like middle and south ameria), every 325i built in the 90s has 190hp stock, 
and when I do a little math compared to the 4 valve vr6 (which has a compareable valvetrain and head but the intake port which is not ideal because of different length and squared shape) a 2.5 should have 182hp


_Modified by yohimbe at 1:05 AM 4-30-2010_


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## easy cheese (Aug 3, 2008)

so who would we get to tune us if we got the piston?


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## yohimbe (Jun 13, 2005)

custom setup


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## [email protected] (Dec 5, 2005)

easy cheese said:


> so who would we get to tune us if we got the piston?


 Whomever you feel comfortable with! 

IE Rod & JE Piston Combo Packs are available @ 20squared HERE


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## thygreyt (Jun 7, 2009)

is it that easy?? to tune i mean...


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## [email protected] (Dec 5, 2005)

thygreyt said:


> is it that easy?? to tune i mean...


 Should have chosen a better way to phrase that sentence. 

Whichever tuner you feel comfortable with and most important, is willing to do it for you. I know if anyone is interested, I can speak with the guys at Unitronic as I'm sure they won't have any issues with it.


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## thygreyt (Jun 7, 2009)

whats a good ratio for NA?? and for FI?? 

i still havent decided which route to go... so any of both options is good...! 

and anyways, what would be the estimated power gains??


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## Issam Abed (Feb 12, 2004)

[email protected] said:


> The 2.0T pistons won't work in the FSI, the valve angles are different, so the notches are wrong.


 This post is confusing. I assume you are trying to say that 2.0T pistons wont work in the *INLINE-5 *Rabbit motor and if you are saying that then you are wrong. 

BPY pistons will work and have worked in the 2.5 motor.  

If you guys need higher CR pistons send me a PM on the INA account.


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## [email protected] (Jan 2, 2009)

If you want a hackjob, you could slap in FSI pistons and I suppose it might work. The valve angles ARE different though, between the two engines. 

'Course, what's a few wrong valve notches between friends. ABA's run with 16v heads after all, doesn't make it right.


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## Issam Abed (Feb 12, 2004)

[email protected] said:


> If you want a hackjob, you could slap in FSI pistons and I suppose it might work. The valve angles ARE different though, between the two engines.
> 
> 'Course, what's a few wrong valve notches between friends. ABA's run with 16v heads after all, doesn't make it right.


 Apples to oranges... ABA pistons are *FLAT TOP* and have *NO* cut outs for the intake valves. 

Not sure where you got your information from but FSI | TSI & 2.5 cylinder heads are practically the same castings and the valve cut outs are in the same locations. (Please see other threads which I wrote for Vortex for further information)


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## [email protected] (Jan 2, 2009)

The valve angles are different between the two heads, I have both engines here. I'm well aware of the similarities and shared parts. Similar does not mean identical. 

FWIW, it'd probably run just fine with no valve notches as well, if your cam timing was spot on, and you aren't floating parts. A 1.8t will for example.


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## Issam Abed (Feb 12, 2004)

[email protected] said:


> The valve angles are different between the two heads, I have both engines here. I'm well aware of the similarities and shared parts. Similar does not mean identical.


 Not sure what engines you have there but the (2) engines I have here have the following: 

BPY Camshaft centre to centre = 109.2mm 
BPY cam height from face of head = 139.6mm 

BGP 2.5 Camshaft centre to centre = 109mm 
BGP cam height from face of head = 139.9mm 

If you have done any disecting or data to prove this then please share it. I cant be the one to always post this kind of information.


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## BluMagic (Apr 9, 2008)

i plan to.. but i need a second car first. interested to see the numbers.... 

11:1 and the valvetrain kit paired with a single mass lightweight flywheel should make a pretty fun car.


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## thygreyt (Jun 7, 2009)

so 11 is better for NA and 8.5 better for FI?


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## [email protected] (Jan 2, 2009)

The Rabbit intake valves are canted 2 degrees less then those in the FSI, which changes the position and obviously angle of the valve notches slightly. 

A visual inspection of course will not catch the 2 degree difference. I was surprised as well.


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## BlackRabbit2point5 (Sep 6, 2007)

personally I'd say 9:1 is ideal for boost unless you wanna run a ton of boost and don't care if the engine is flat when off boost, then run 8.5:1 or lower


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## thygreyt (Jun 7, 2009)

what about na mode? 

lately i've been debating on wheather to do NA or FI. 

if i were to stay NA i would change the rods, valves, and similar components. 
mods would be: 
-pistons 
-rods 
-valves 
-intake 
-Intake mani 
-power pulley 
-headers 
-high flow cat 
-exhaust 
-cams 
-standalone software 


or FI: 
-C2 turbo stage 2 
-intake 
-chip 
-exhaust 
-SRI 
-power pulley 

where can i get more power and reliability?


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## yohimbe (Jun 13, 2005)

why does the 2.5 inline need that low CR for FI, my daily driver is a 1.8T mk4, has 9.5:1 and I am running 22psi (1.5bar) the design of the head/combustion chamber seems to be very actual , not like the old 2 valve GTIs or 2 valve VR6


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## Jefnes3 (Aug 17, 2001)

a ~stock 2.5L is already knock limited without boost on pump gas. 
add boost ~7-8psi and ignition at torque peak is near zero deg. 

-Jeffrey Atwood


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## sleees345 (Dec 31, 2009)

If the valve angles are different between the 2.5 and FSI, can't the pistons be machined so the notches for the valves match? There's at least an alternative to buying the forged pistons. At the end of the day, though, i may prefer the peace of mind having the forged pistons.


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