internal modifications..for DC5R TURBO..

**acz0190** · 03-03-2006 09:24 PM

hi there,
recently i have been researching pistons,rods and cams,valve work, i am on the verge of purchasing some pistons from the states and was not sure of what compression ratio to choose from for a turbo application hoping to run 16+ boost.The stock ones i have now on the k20a are 11.1:1 of 86mm bore and i have no idea which combination to use for a safe and powerful turbo setup. also would anyone have an idea what are the procedures/pricing would be just to install new pistons/rings/rod?i heard itl be costly and a c*nt of a job. The pistons are the same bore as stock.

**yourfather** · 03-03-2006 09:41 PM

You've posted this in the ALL MOTOR section, not the FORCED INDUCTION section.

and when it says FORCED INDUCTION that means either SUPERCHARGED, or TURBOCHARGED.

But, I was just wondering why you wouldn't slap on a turbo first, see how it goes, and then if you need more power, put forged internals in.

And, from what I've read, compression doesnt mean a thing. It all depends on how you get it tuned.

**BLKCRX** · 04-03-2006 12:02 AM

Personally a standard k20 turbo charged on a stock motor on 7psi will result in around 200 to 250kw depending on what turbo / manifold you use… building a engine and running even more boost would give you a 300+kw machine

Anyway id suggest turbo’ing your standard engine first and then look at building up the engine.

There’s a lot more to building your engine than just installing rods and pistons, and I most certainly wouldn’t buy 86.00mm pistons you want at least 86.25 and hone out the bock so the pistons have a perfect piston to bore clearance, then worry about new bearings for the whole engine, new gaskets / seals, new oil and water pump, those things can cost a fortune, not to mention labor. I just got back from qld from tuning a turbo dc5r and yeah stock form with a well designed turbo setup can be a lethal weapon.

Heres a pic of my clients engine bay ! Turbo DC5r !

Originally Posted by yourfather

And, from what I've read, compression doesnt mean a thing. It all depends on how you get it tuned.

Engine Compression will make or break a turbo setup !! it must be matched PERFECTLY with your setup !!! this is VERY important i wouldn’t be buying pistons, that’s for your engine designer to choose the compression and bore size !

Regards James

**Weq** · 04-03-2006 12:08 AM

james hit the nail on the head.

to answer the quesiton though, usually people drop compression down into the 9's as that is what most off the shelf 'turbo' forged pistons come in. Watch out for forged NA pistons.

ps. thats what i call a turbo!

**yourfather** · 04-03-2006 10:15 PM

well, im not a mechanic or a tuner, so I'm sure you know best

But, from conversations I have had with you James, and from the Turbo B series thread, it doesn't seem to say that having a stock compression ratio is necessarily a bad thing.

**BLKCRX** · 05-03-2006 04:16 AM

I don’t believe there is ever a reason to go below standard compression!! for ANY turbo setup. That’s my belief.

Regards James

**acz0190** · 05-03-2006 05:03 PM

all i wanna do is just nail those xr6/8 turbos,clubbies at the green light..i hate how they're intimidated when they see my car..anyhow i heard putting in pistons is costly whats an estimated figure?

**acz0190** · 05-03-2006 05:08 PM

i guess the reason why id wanna do internals first is because its the most costly part and i wouldnt have to worry about damaging my engine if it was turbocharged on stock internals. thanks guys i appreciate your help everything is a learning curve for me..

**yourfather** · 05-03-2006 05:14 PM

well, you won't need to put forged internals in.

You can get 200kw @ the wheels with a turbo kit.

The XR6 turbo doesnt put out that much at the wheels.

**Weq** · 05-03-2006 09:46 PM

too put pistons into a motor, nothing else, u are looking at around 2k in labour.

**LVNIT** · 06-03-2006 11:22 AM

Originally Posted by acz0190

all i wanna do is just nail those xr6/8 turbos,clubbies at the green light..i hate how they're intimidated when they see my car..anyhow i heard putting in pistons is costly whats an estimated figure?

Good luck nailing them at the lights mate, traction wont be your friend, been there done that

**BLKCRX** · 07-03-2006 09:37 AM

There’s no way I would ever just recommend replacing the pistons only in a k20 engine, I would be replacing the rods before the pistons, as they are by far the weakest part.

Rods and Pistons + Hone + new gaskets + new bearings would be a minimum, but whilst your block is out there is so much more work you could do to the engine to improve its efficiency strength and performance and reliability.

Regards James