turbo 325 compresion?

[rob_htid]

right, im realy thinking about turbo'ing my 1991 325i sport, i understand thi is already the lower compresion engine but still too high for running moderate boost,

instead of skimming the piston's (weakening them) i have a set of m20b20 rods wich are 2mm shorter than the 132mm standard rods, that would lower the compresion yes? but by how much and am i just talking compleate shit here


only way of finding out is by asking you guys so thanks for takeing the time to read and please reply

Rob

[e30_Turbo]

something around 7.5-1 cr

a little low unless you're planning big boost.

8.8 is fine, evo's are 9 out of the factory.

Fozz

[rob_htid]

how would i get 8.8, skiming? whats the standard CR on these?

is it worth forking the cash on a set of pistons?

[e30_Turbo]

how would i get 8.8, skiming? whats the standard CR on these?

is it worth forking the cash on a set of pistons?

8.8 is what you have now

early m20b25's are 9.7 iirc

define worth?

Got a spare 500? if so then yes, going for 500+ bhp all day, hell yes!

5-12psi fun car, not needed.

BMW make engines that can take abuse, mines had 10,000 turbocharged miles, on a 155k lump N/A, stock bottom end, still going strong.

Spend money on manifold, management, turbo, head studs, head check, big exhaust, decent condition stock cam or turbo grind cam, bigger injectors, big IC and the biggest of them all, get it mapped properly.

Fozz.

[Gunni]

8.8 compression is fine for whatever you need on stock internals.

Also B20 rods are 130mm and 325i are 135mm,

just run the stock engine as it is.
plenty plenty plenty people have done it.

http://www.e30tech.com/forum/forumdisplay.php?f=7
http://www.e30zone.net/modules.php?name ... pic&t=6137

[Gunni]

Also here is a little to all ,
spend your money on the tuning !!!!
part´s only get you so far.

[rob_htid]

ok thanks i was 3mm out on the rods there...strangly i actualy knew that, anyway!...


thanks for the help, i didnt think it was such a low comp engine to be honest, thats good, what management are you guys useing? i take it its not anygood useing the standard, how about a cheap standalone set up like megasquirt? also what bhp you getting from just 7-12psi?


thanks Rob

[BadDave]

what bhp you getting from just 7-12psi?


thanks Rob

Realistically

Between 250 and 300-330 ish from what information i've seen on here and other forums


Gunni/Sal/Ant ond others should be able to be a bit more precise with the figures

[Gunni]

totally depends on manifold and turbine section on the back side, and the compressor on the front side.

8psi shows normally 240-280
12psi 280-330hp

I use VEMS , and just in the last couple of days it´s taking leaps and bounds in functionality and tuning capabilities.
Not that it was bad to begin with either.

If you want to know everything you need to turbocharger your E30 read the stickies in this forum.
And then come back with questions.
http://www.e30tech.com/forum/forumdisplay.php?f=23

[BadDave]

Gunni
Just out of curiosity(and for future referance)

How much boost can you safely run with an 8.2:1-8.3:1 CR on an M20B28 and standalone management setup??

[Gunni]

depends on back pressure, setup and tuning, but for a simple reference,
it´s known that stock internals can do 475whp with stock compression with a 2.5.
and that was done at 1.4bar of boost using a paper gasket.
So if you stay below those numbers your fine

But remember that was a 2.5 highly selective parts bolted on (i.e best available) and thus the engine setup optimized.
If you have uprated rods and pistons it basically becomes a point of how much your turbo can do, and your injectors.

but for stock internals, I´d say anything below 400whp is going to be fine for a very very long time.

[BadDave]

Thanks for that Gunni