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spence88mph spence88mph is offline
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Join Date: Jan 2007
Location: Melbourne, Australia
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you need to read this again, very good advice...

Originally Posted by DonE View Post
Kris is right. You need to talk to someone who has actually done this mod as we are all just guessing about turbos until you provide air flow numbers. Who knows what the most efficient turbo will be for a 3.8L.

As for cams, you really need to start here first because it is the component that manages air flow through the motor. If it were mine, I would be looking at custom for my application. Performance Developments (a kiwi) makes a great GTII improved version that works through out the power band (2800 - 7000rpm).

Here is something to consider on the pistons - Mahle in the US is now more flexible in price and build, so look at them for a set of 102mm pistons - but wait. Consider a set of custom rods that are a bit longer (a mm or so) to stroke the motor - Mahle will off-set the piston pins on the custom pistons.

Now take the airflow that the new cams and stroker rods make, then pick your turbo. With the combination of longer stroke, the big vacuum pulled into the cylinders will give you good torque, but longer stroke also means compression is accelerated, so watch for detonation (it's a trade off). So your turbo will need to big, but very efficient at low boost levels and high air volumes. Most likely, you'll need a ball bearing turbo.

You have a great platform for a torquey turbo motor - don't stress over the HP numbers. While you're pulling away from the light, the guy next to you with 100 more ponies will still be waiting for the turbo to spool up.

Good luck
'89 911 M491+Turbo
'89 944 Turbo
'88 928S4
'18 C63S Coupe
Old 02-06-2010, 01:43 AM
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