Turbcharging 3,2 -how loving compression?
 

Hi

I'm new on this forum as a registered user but have been looking around for a couple of years,

I'm planing of turbocharging my Carrera 3,2 and my planing setup is: Megasquirt, MSD, Holset HX40 charger and homemade headers

I have a Carrera 3,2 -86 with Euro spec engine and wondering how you guys have lowing the compression ?

-way to go is what I can see: cutting the top of the pistons a bit, new pistons or put a distance between cylinderfot and engine case.

the last option I have newer seen anyone do on a Porsche engine but is VERY common on bikes

If I go for new pistons -which piston? -were to buy? and what compression ration? -thinking of 8:1 compression and boost of 0,8-1 bar



-thanks for answers

BR from Sweden

Erik

sorry for the bad spelling in the topic! -can´t edit the topic :(

Hi
I don't think you have enough meat in the pistons to cut them down.
Adding shims under the cylinders have different problems, you have to deal with the cam chains etc.

The right way is to buy new pistons, JEs are good. I have been thinking about the same thing and I would try to use 8.5:1 or maybe a little more.

EFI with ignition is mandatory, you will have to be flexible with the timing as boost increases.

I would also use 2 smaller turbos, should be easy to find 2 smaller used turbos from the scrapyard. A lot of small displacement cars use turbos nowadays.

Hej Magnus!



Where do I buy JEs with 8.5:1 ?

With the Megasquirt I have control of ignition, boost and fuel.

I´m going to go for one turbo, have friends that runs singelturbo on 930 with 513 whp and spools wery quick aloso a BMW 635 with singel HX55 (and thats a BIG turbo) with quick spool.

-with shims around 1mm is there realy a problem with the cam chains? isn´t there enough play of the chains?



//Erik

Hej
You can buy directly from JE.
Maybe you can get away with 1mm, if that is enough to lower the compression.
You should talk to Micke Svens, we have a 911 turbo guru in Stockholm! I know he has some tricks with chains and using a smaller idler sprocket etc.

Hi

Can´t find anyting on JE, do you have a link? what money do we thalk??

Charles Navaro at lnengineering

LN Engineering Nickies The Original and Genuine CNC Billet Aluminum NSC-Plated Cylinders

Good guy - very knowledgable

also look for posts from Juan Ruiz - he ran some crazy boost numbers (and HP) on a 3.2 -

JE Pistons Manufactures Quality Forged Pistons for the Domestic Automotive, Sport Compact, Powersports and Racing Markets, send a mail and ask them. JE can make any piston you want.

I asked JE about pistons for a 2.0S, I'm guessing that the price won't differ much for 95mm pistons, so it's roughly 10.000 Swedish for a set with shipping and VAT etc.

"We do not shelf stock these pistons but we can make these for you. We have a minimum piston order quantity of 4 pistons, and the starting price with pins, locks, and rings is $165.00. Additional features and coatings will cost more.

The standard lead time is 3 weeks once we get the complete information and payment."

-any cheaper options??

It's never gonna be cheep to tinker with a Porsche engine. You need quality forged pistons.

US 3.2 pistons have a lower compression ratio at 9.5:1.

Why not just limit boost to .4bar and leave the internals alone? When rebuild time comes, change the pistons and the wastegate spring to up the boost.
With a good intercooler or water/alcohol injection and 93 octane gas, you should be fine.

Hi

I have had a lowboost setup in mind but higher boost seems tempting :) the solution to ad a shims under the cylinderfoot is somthing I have to investigate more.

Hi

I found this tread Autobahn Performance, Inc. - Expert Independent Porsche and Audi Service and Parts and if you look a bit down on the side you see that they have machined of the piston for lower compression so it seems like there is some meat to take of !

-anyone how knows ?

But thats a US spec car with 9.5:1, you have euro pistons 10.3:1.
But sure you can probably lower your compression somewhat by machining the top of the piston. I have read somewhere to leave at least 5 mm.

Hi again!

I talked to Micke Svens at spezialmotorer and he says 1,5mm should be now problem to shim the cylinder foot regarding the cams and chains

I have tried to calculate the the compression with 1,5mm shim and thats make with my calculations around 8.5:1 -can someone help me calculate the compression??

//Erik

Anyone how can help me with the compression calculation ?

3164cm3
borr 95mm
stroke 74,4
comp 10,3:1

/E