So I'm building a d16z6 with scat rods and PM6 pistons. This comes out to almost 10:1 CR. Will I need a tune for this? This will eventually be boosted and tuned on Neptune but I wanted to use the motor in the mean time.

Also, how would 8.54:1 (vitaras and custom rods) be to drive unboosted. Stock CR is 9.14

 

In order for the setup to run PROPERLY, yes you will need a tune. If you have a burner, let me know and i can send you a Crome BIN for a good basemap for a very similar setup. (D16z6, stock map, 10.2:1 CR, stock cam, ported intake manifold, 4-1 header, 2.5' OD exhaust with test pipe. This would be a good point to start from. As for how the car would run with 8.5:1 comp outside of boost, it wouldnt make much power. Why may i ask would you even consider running that low of compression anyway? With todays fuels and tuning available there is no reason to do such a low comp build for boost, that is very old thinking. Hell my last turbo build was 12.5:1 comp on a stock sleeve B20 and it held totally fine for a lot of street miles and track abuse on ~14psi/450whp.

 

the low compression was basically because vitaras and custom forged rods was cheaper than real forged pistons. I also learned that I can't use forged rods with the PM6 pistons so I guess I'm stuck using stock rods which will be ok because I'm only shooting for around 200 HP.

But no I don't have a burner. I think I'm going to get a base map from Phearable and use that until I save up for either Ostrich and Hulog or Demon/Neptune

 

Gotcha. Well stock pistons and rods are totally fine for 200whp on a d16z if everything is healthy to begin with, so if that's all your shooting for save your money to use elsewhere. With a proper tune (NOT a basemap) you can go 250-275 reliably for a daily driven d16z6/y8 and we have done probably half a dozen stock d series turbo setups in that power range for customers with great success. Back in the day my own personal 95 Coupe went into the 11's on a stock d16z6 shortblock and lasted an entire season with no failure before I got rid of it. Good luck

 

Interesting comments B20VtecVillain about those numbers on stock engines. You got a PM

 

Don't use vitaras. The blow-by and combustion efficiency sucks, not to mention the loudest wrist pins known to man, it sounds like a diesel. You'll never actually know if you threw a rod bearing. It makes every turbo laggy, and your power output suffers considerably for not even having forged pistons. I've tuned too many of these, and nobody is ever happy with them including myself.

8.5:1 CR Vitaras on a non-boosted Z6 makes 106hp.

Honestly you probably don't HAVE to tune a stock Z6 on 10:1 CR. The stock ecu is incredibly conservative. But you SHOULD tune it, because you're missing a lot of potential even on a bone stock engine.

For D series I would encourage you to go with higher compression even if you're boosting it. 9:1 at the least, but 10:1 is ideal. It's a long stroke, it spends very little time at TDC so knock isn't a huge issue - especially with the Y8 head.
You can use a bigger turbo and spool quicker, using much less boost and still making better numbers. Until you pass about 350hp you can still get by on pump gas also.

 

B20VtecVillain is right, there are many stock D-series blocks pushing 270hp. Granted they're not track driven, the pistons melt pretty quick if you're rapping it out too often since they don't dissipate heat very well. But if 270 is all you're after, just throw in some ACL race bearings and ARP head studs, mod it up.

 

i had a vitara z6 back in '09 i think it was. honestly in boost it wasnt bad and sure as **** wanted a lot of timing on the dyno. in vacuum it sucked. even with a good timing advance it still had nothing and you would spend most of the time driving around at like 5-10" just keeping up with traffic. it cut down on the mpg pretty good

if you are going to go boost anyway, just tune it now. it will run better, more efficient you may even get a few more mpg