Okay fellow HTers. Here is my issue, I recently took my block to the machine shop to get cleaned and all that. And I had to bore out the cylinders to 75.5 due to surface rust... Now im having issues regarding pistons. I was planning to buy Vitara 75.5mm pistons but i heard that the piston sticks out a little.. so I dont know what to do now. I still have the stock pistons and rods but im not sure if that will work with the 75.5 bore..

If there's anyone who can help or provide some info, I appreciate it.

And i was planning to build to motor for boost. looking for 190-200whp.

 

Is your D15B a 3-stage VTEC? I have always wanted to built one...

Vitara makes all different types of pistons. High & low compression, turbo pistons... etc..
If you had your block bored out .5 you will need a 75.5 pistons.

If you buy High compression pistons they will sick out a little.
If you buy turbo or low compression then you will be fine.

A Friend of mine's Vitara B20 VTEC high compression build.


You will also need to have is bored for Piston to wall clearance.
This is usually .0025 to .0035 the clearance depends on your HP goal.

.0025 = 250hp
.003 = 300hp

There is more behind it but this is how I have always determined the clearance on all my Vitara builds.

If you go more then .004 you run the chance of having piston slap...
I never go more then .0035

If you go with a wiseco piston the clearance is in the piston.
Most of the higher end pistons have the piston to cylinder wall clearance in the piston already.

If you replace the rods with H-beam you will need to notch the block to make clearance for the thicker rod.
If you buy I beam rods you wont need to notch.
http://www.theoldone.com/articles/d_...building_tips/

Your goal of 190 to 200whp is completely reasonable.
You should have no problem reaching this with out boost on a fully built D15b.

Good luck with your build!!

 

The engine is the JDM D15B single stage Vtec. The ones from the vti's. And with the piston to wall clearance, what tools do i need to measure that? Feeler gauge? I've been trying to look for I-beam rods so i wont have to notch the block but i cant find any. Wiseco is a great company but i dont have the budget for 400+ pistons because they dont have off the shelf pistons for this engine.. Its going to be a daily driver also.

 

For p2w you need to use a dial bore gauge and measure bore then mic the pistons. You should always have the pistons before having your block bored. You could run into some problems

 

I always leave a piston with the machine shop.. Let them figure it out.. They have all the tools....

 

okay so use a dial bore gauge for p2w. I originally wanted to keep the bore at 75mm but i wasnt sure if the surface rust broke through, so i went on the safe side and over bored. Is there anyone running vitaras in their jdm d15b here?

 

so should i order 75.5 vitara's and take the block to the shop?

 

Yea but hope your p2w clearance isn't already to much since they bored it without the pistons

 

ahh, i hope it fits then.. and if it does fit. Will it matter much if the piston isnt too far down or up inside the block? like what kind of clearance issues will i have?

 

I don't think you understand what p2w clearance is

 

the clearance between the piston and walls right? im asking if the if the p2w has good clearance should there be a problem with the piston sitting above or below the deck.

 

The p2w has nothing to do with where the piston will sit in the bore

 

yes it doesnt have to do with where the piston will sit. so p2w is the clearance between the piston and the wall, too tight and it'll scratch the walls.. too loose and whatever happens. Okay here is what im trying to say, ex: the p2w is good. now what about where the piston sits? Is there going to be a big difference if it sits a little above or below the deck.

p.s. - not trying to argue or anything but thank you for helping.

 

only if there is no room in the combustion chamber to allow clearance for a high compression piston, u dont want the piston coming into contact with any edges or valves (can happen without proper valve relief on the piston, wich are the round grooves you see on the compression side of the piston, in some high compression applications these recesses are increased to allow for proper valve clearance). Now... with a low compression or turbo application piston, it will usually sit lower, and you will have to compensate with boost and a/f tuning to reach your goals, because lowering compression in a naturally aspirated car will lower the power output. also if u decide to go high compression, make sure you up your octane rating, same if you go turbo, only case you wont have to raise the octane is if you lower the compression and remain naturally aspirated. hope all this helps.

 

Great info Ej1ryder. I know turbo app pistons usually sit below like you explained. Now what if they sit slightly ABOVE the deck? Should I treat it as if it were a high compression piston and give it enough room for combustion?

 

I don't really have any advice for you, but is there any chance you'd do me a huge favor and post a pic of one of the stock pistons? I have one of those engines, I was told they were domed pistons, now I'm starting think they're dished.

 

The original P08 pistons are flat dished.

 

Interesting, thank you very much They're definitely higher compression than Z6 pistons.

 

 

help?

 

anyone with more good info?

 

u got turbo application pistons and theyre sitting high at top dead center? have the clearance from the top of the piston at top dead center, to the top of the inside of the combustion chamber, take into account where the valves will be wen fully extended bu the cam lobes. if clearance is too tight and ur planning on going turbo u may want to invest in a thicker head gasket to reduce compression and increase clearance. hope that helps

 

Question about the P08 pistons, I just pulled apart a 95 D16Z6 engine and someone is using the P08 pistons instead of the P028 Pistons, my question is, why would some one do this?