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2.7 with i pistons
Posted: Thu Jan 18, 2007 8:47 pm
by Gabi_323i
ok so i have a 10.2:1 eta engine in my car. last night my timing belt slipped and one valve broke and made a huge hole in one piston, i bought 6 2.5 pistons, my question is will this work ok in the eta block? i also have the 2.5 head, intake, t/body etc
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 8:48 pm
by dimebag_from_hell
i wish i knew what all this stuff meant!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:15 pm
by Jimbob
The block will need decking slightly (can't remember how much!) and the piston skirts will need shaving (bout 8mm I think from when I had mine done).
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:24 pm
by Gabi_323i
Jimbob wrote:The block will need decking slightly (can't remember how much!) and the piston skirts will need shaving (bout 8mm I think from when I had mine done).
i want to go turbo so i think i can benefit the lower cr
i don't like the piston shaving too ... i thought it needed only with the 2.8 conversion?
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:28 pm
by Jimbob
you will have a higher CR but as most people only run 4-7psi the given CR will be fine.
If you don't shave the skirts they will hit the crank!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:33 pm
by Simon13
i'd use later 2.5 pistons then lower CR so more boost!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:42 pm
by Gabi_323i
how can i have a higher cr if the pistons sits 2mm down the block??
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:44 pm
by Jimbob
The earlier pistons were a higher comp than later ones, i was assuming you had the earlier ones
and the reason for to lower the block was to have the pistons sit in the same place at their highest point
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:50 pm
by Gabi_323i
well i read a thread posted by mops
http://www.e30zone.co.uk/modules.php?na ... ht=stroker
and no one mentioned the piston needed shaving and the cr will be 8.3:1
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:52 pm
by Simon13
we need a picture of the pistons!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:56 pm
by Jimbob
Look for any other info (loads in this section) and Ant will have posted somewhere the piston skirts being shaved. Like I said, I've had it done myself and had a very good engine as a result of the work I've previously stated!!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 9:58 pm
by Gabi_323i
and i really don't know what 2.5 pistons i have, early or late, how can i found out? i take a pic tomorow
here is the 2.7, dead
http://i82.photobucket.com/albums/j266/ ... mag007.jpg
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 10:01 pm
by Jimbob
Here's my early piston:
Hope that can help.
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 10:05 pm
by kam-325i
the later 325i pistons have an inverted dome/dish where the flat section is on the early ones.
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 10:06 pm
by Gabi_323i
tomorow i will post pics with the pistons, i want to go turbo so i need a lower cr, i don't want to shave the block
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 10:08 pm
by Simon13
kam-325i wrote:the later 325i pistons have an inverted dome/dish where the flat section is on the early ones.
otherway round dude!
Re: 2.7 with i pistons
Posted: Thu Jan 18, 2007 11:02 pm
by kam-325i
Simon13 wrote:kam-325i wrote:the later 325i pistons have an inverted dome/dish where the flat section is on the early ones.
otherway round dude!
Eh ???
later = lower compression 2.5 ?
Re: 2.7 with i pistons
Posted: Fri Jan 19, 2007 9:39 am
by Ant
You can just about see in the Pic Jim has posted that the ex valve cutout is deeper in the early high CR pistons.
That section is quite a bit "meatier" on the early units when compared to the late.
using 8.8:1 with the 2.7 build will give a CR around 9.5:1 with all the usual stroker mods.
Skirts must be machined on the early pistons, it will not turn over otherwise !
Re: 2.7 with i pistons
Posted: Fri Jan 19, 2007 9:44 am
by Gabi_323i
with the 2.7 block crank and rods and 2.5 pistons the piston will be 2mm down the block? i want a lower cr for turbo
Re: 2.7 with i pistons
Posted: Fri Jan 19, 2007 9:48 am
by Ant
will give approx 7.4:1 CR then dude.
leaves a large squish band though, I'd certainly recommend uprated head bolts and welded waterways.
there is no cheap way to do what you want to achieve, reliably....
Re: 2.7 with i pistons
Posted: Fri Jan 19, 2007 9:57 am
by Gabi_323i
so i have the late pistons
i very confused :-s mops said that the comp will be 8.3:1 with the eta block
edit that was with the early 9.7:1
now i get it
i will have welded water chanels and metric blues, and a holset h2d
Posted: Sun Jan 21, 2007 1:47 pm
by Gabi_323i
http://i82.photobucket.com/albums/j266/ ... G_0029.jpg
http://i82.photobucket.com/albums/j266/ ... G_0030.jpg
these are the 2.5 piston, are they late or early model? from what pictures i've seen i think they are the late 8.8:1 ones
OK if you're using the euro i head with the euro i pistons:
VOL = Volume of 1 Cylinder
CCV = Combustion Chamber Volume
CR = Compression Ratio
First we know that the i engine has a bore of 84mm and a stroke of 75mm so:
VOL = (1/2 BORE)squared * STROKE * pi
VOL = (4.2cm*4.2cm) * 7.5cm * pi
VOL = 415.63cc
We know that the engine has a stock CR of 8.8:1 so we can figure out the CCV:
CCV = VOL / (CR - 1)
CCV = 415.63cc / (8.8 - 1)
CCV = 53.28cc
What you will be doing however is changing the stroke to 81mm so the VOL changes:
VOL = (1/2 BORE)squared * STROKE * pi
VOL = (4.2cm * 4.2cm) * 8.1cm * pi
VOL = 448.88cc
Now using this and the CCV we can figure out the new CR, but the pistons will be 2mm from the top of the deck. So we account for this empty space by calculating its volume and adding it to the CCV:
VOL = (1/2 BORE)squared * HEIGHT * pi
VOL = (4.2cm * 4.2cm) * .2cm * pi
VOL = 11.08cc
New CCV = 53.28cc + 11.08cc = 64.36cc
Ok so we did all that just so we could do this:
CR = (VOL + CCV) / CCV
CR = (448.88cc + 64.36cc) / 64.36cc
CR = 7.97
are the above calculations corect?
Re:
Posted: Sun Jan 21, 2007 2:05 pm
by Ant
Hmm, I vote late, what do the skirts look like ??
Re:
Posted: Sun Jan 21, 2007 2:33 pm
by Gabi_323i
damn, i'll have to take a pic
how about the cr?
Re:
Posted: Sun Jan 21, 2007 3:04 pm
by kam-325i
those are the same pistons that are fitted in my engine, which is the lower compression 8.8:1
Re:
Posted: Tue Jan 23, 2007 9:02 am
by scort300
Hi everybody i'm new to this website, but very impressed. Now excuse my ignorance but the ETA block. Is that the 525e bottom end? what else used this? And what is the Euro head?
