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Vitara p2w clearance

5K views 31 replies 15 participants last post by  satansbrother 
#1 ·
OK. I know almost everyone suggests running them loose (0.003"-0.0035"), which is quite loose for a cast piston, especially for such a small bore. Has anyone tried Honda clearances? (0.0004"-0.0016") at least at the service limit? (0.002"). Generally, I have found that if you are patient enough to break-in a motor, tighter clearances will help in the long-run with less blowby and less oil consumption. But you have to be really patient with breaking in, especially not boosting for more than a few seconds and let the pistons expand and scuff.
 
#4 · (Edited)
my p2w was around 0.0045" on my first vitara engine, I never had any abnormal oil consumption(except some turbo seal leakage fixed now),not even 1 liter per oil change. still going strong today 30k .

as for my break in ,drove 500-600km on low boost +start tuning a/f ,change oil,
crank the boost continue tuning and drive it like I stole it .
Been enjoying it since.

Tighter is not always "better"
 
#10 ·
Like said before..

Looser is for cars that do boost for long periods of time. If this is for street purposes, then tighter clearances will be fine as your only in boost for a few seconds. Street cars spend most of the time in Vac anyways.
 
#7 ·
For the most part, The FSM specs are for stock built engines. If you are tossing one together for mom's grocery getter they are fine.

You start increasing the HP, then some clearances need to be adjusted for that.

More Air + More fuel = More power = More Heat = More expansion.
 
#8 ·
Still, I see no problem boosting other Honda engines (and I have boosted quite a few in the past) with stock clearances. And I am talking more than 2x the stock HP levels with no issues. So, I think going that loose might not be needed. Anyway, I will probably be among the first trying tight clearance on vitara pistons and let you know guys. I am thinking to go for Honda's service limit (that is 0.002"). 75.5mm of course and longer rods.
 
#9 ·
#11 ·
I'm running a .0038 in my vitara but I just got the car together and only got 50 miles on it. Right at 18-19" vacuum so I didn't have issues with the rings seating and I honestly took it easy on the motor. This is a street car that I plan on boosting right at 22lbs once tuned the first week of February. I'll give u updates as time goes on
 
#13 ·
^^^ This is what im mainly concerned about. But from what I have gathered about the subject and some may agree and some may not is it seems that ring gap should definitely be run on the loose end but p2w I dont believe its necessary to be that loose..... Idk they are a cast piston and so they should expand like a cast piston...... I'll probably go like .003 on my build though too just in case lol
 
#14 · (Edited)
Yea its loud compared to my forged supertech/eagle build but not nearly as loud as a buddy who has .0040 p2w 75mm nippons pointed toward the timing belt. I have .0038 on 76mm ycp vitaras pointed toward the flywheel and once she's warm its identical to my other car so no complaints here. Definitely go ycp and toward the flywheel. We put the motors together at the same time in my garage and decided we'll each go a different way on the piston with similar clearances and see which is louder because most say go toward flywheel but some stick to the timing belt. We're both much happier with engine noise of mine. I'm guessing it's the way they're facing vs. The fact that mine are ycp vs his nippons.
 
#25 ·
Good info going here, I'm curious to what the higher hp motors run for p2w. Say an eagle/vitara around 450-500+ hp? I'm thinking around .0035-.004 as to it will be a somewhat street car weekend warrior drag car running e85. All in all i guess it depends on what my tuner thinks.
 
#26 · (Edited)
I'd say most people run around .035 Me being one of them.. and yes the pistons are some what loud when the car starts. That's the negative side of the bigger ptw but hey we don't have to worry about our pistons seizing when we are in boost now do we lol..

I also know people on here that run .025 and have been for years with no problems.. Me personally i think if your around 350whp .025 is Fairly tight.

If i could have done my build over again i might have gone with .030 to cut down on the cold start noise but hey its still going strong just under 2 years now. So i guess its not that bad eh? lol

i think what it comes down to is, I would rather deal with the noise then have a piston seize during a Wide open pull period..

Has anyone known someone seize a Vitara piston because of too tight Ptw clearance? Not something you really hear to much lol
 
#28 ·
My next block is .0035 but I'm shooting for 400+ I do agree on shoebox's statement above. .0025 250 .0030 300 .0035 350-400...
 
#29 · (Edited)
You mean 1 thou per 100 wheel hp. Haveing 35 thou piston to wall would be comical. Also i have 5 thou piston to wall on my d17y8 na build and my upper and lower ring gaps are 25 thou, and my bearings are all looser then oem service limits. Some may say i like it loose
 
#30 ·
You mean 1 thou per 100 wheel hp. Haveing 35 thou piston to wall would be comical.
Yeah I've always wondered if people understand what the numbers really mean. Im sure fuel would effect piston swelling due to heat ranges, but i think the principle is correct with one thou (.001) for every hundred horsepower.

I've never built an engine so I'm kind of in the dark about one aspect of p2w. Lets say I plan on running a .004 p2w, i would assume you that would be your total clearance, so really you would only have .002 on each side of the piston for clearance? or is it .004 on each side so really you would over bore the cylinder .008 for the final p2w of .004? i would just like to get it straightened out, preferably from someone who has experience here. P.S. this question makes me feel dumb but i won't after i get the right answer.
 
#31 ·
Measure bore, measure piston in correct spot. Take piston size away from bore. You have piston to wall. The pistons never actually sits in the middle depending on what part of stroke its hard agaist the bore on one side.
 
#32 ·
Measure bore, measure piston in correct spot. Take piston size away from bore. You have piston to wall.
Done both, but some clown ass i bought my block from tried a DIY hone job and has the block all tapered and not even close to being the same bore sizes. Im trying to figure out if my block will have enough material for a straight cut so i dont have to junk it.
 
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