Honda D Series Forum banner

1 - 20 of 24 Posts

·
Registered
Civic
Joined
·
682 Posts
Discussion Starter #1
I'm asking this for a friend of mine:
He has a build z6 engine with vitara's and eagle's.Now we calculated his compression ratio with unmilled head(just cleaned)and cometic HG.And it say's 7.88 :1 Cr.Is this Cr still driveable without the turbo ?He needs to drive a few times a year without the turbo ,for Car inspection.Can this Cr still ignite the Air/Fuel ?
 

·
R2.....Zap Balls
94 Ex coupe
Joined
·
5,186 Posts
Mine is 8.5:1 and isn't bad at all without boost. He should be able to drive it, but it may be sluggish without boost being that low. I'm sure someone with more insight on this will chime in soon.
 

·
Registered
Civic
Joined
·
682 Posts
Discussion Starter #3
Mine is 8.5:1 and isn't bad at all without boost. He should be able to drive it, but it may be sluggish without boost being that low. I'm sure someone with more insight on this will chime in soon.
What specs are you using for the vitara pistons?I have feeling that the zeal specs aren't correct on the vitara's or i did something wrong
 

·
insert user title here
domestic.
Joined
·
3,014 Posts
What specs are you using for the vitara pistons?I have feeling that the zeal specs aren't correct on the vitara's or i did something wrong
hes not using vitara pistons. hes just stating his compression ratio. mine is about the same compression ratio and its felt like a n/a car out of boost.
 

·
Hi hater!
Joined
·
12,548 Posts
Well Ill let you know that your calculations are about right on my A6 its about 7.3:1 and is not bad with all my piping hooked up but I had to drive it with my cold side piping off completely it felt totally different and very sluggish but driveable he should be fine
 

·
Registered
Joined
·
4,732 Posts
yeah, hes fine. mine drives fine when boost pipe pops off every few weeks. and thats with no mill, viataras, and .051 Middle shim layer cometic gasket.
 

·
Registered
Joined
·
4,732 Posts
using t bolt clamps. and expensive ass 4 ply coupler, so no isnt that.think its cause my turbo seals are going, and the first 2 couplers/piping gettin oil on it...only thing i can think of. I need to make a bead on the end of all my pipes where the couplers meet then the sob cant blow off period.
 

·
Registered
1999 civic Hatchback
Joined
·
2,452 Posts
I ran my Y7 vitara setup Naturally Aspirated for 1000 miles.. I took it to the track at the end of the break in period and i ran a better time with the dog low CR and vitaras than with the Higher CR stock pistons...lol

With stock 9.6:1 pistons i ran 17.2(with Short Ram)... with 7.8:1 Vitaras i ran 16.6(with homemade CAI, stock Exhaust Manifold, Z6 Intake manifold)... go figure...
 

·
Banned
Joined
·
56 Posts
I ran my Y7 vitara setup Naturally Aspirated for 1000 miles.. I took it to the track at the end of the break in period and i ran a better time with the dog low CR and vitaras than with the Higher CR stock pistons...lol

With stock 9.6:1 pistons i ran 17.2(with Short Ram)... with 7.8:1 Vitaras i ran 16.6(with homemade CAI, stock Exhaust Manifold, Z6 Intake manifold)... go figure...
wha?? That somehow doesn't make any sense. 9.6:1 CR compared to less than 8:1? I don't see how an intake mani would make more than a half a second difference with that big of a cut in CR. The only reason I'm even saying anything is because I'm planning on ordering some shit from you, but I was waiting on the second batch of custom length I beams because I couldn't justify to myself running any lower than 8.5:1 CR. I really didn't want to run any lower than 9, but seeing as this is my DD and I want there to be some room for error 8.5:1 will be fine...but less than 7.5 with the 137mm rods?!!! I don't know about that. But you're saying you got better performance with that low of a CR...I'm kinda second guessing myself. Someone help me out here and explain how that's possible.
 

·
My 91 Crx Hf
97 Civic Coupe
Joined
·
2,164 Posts
How come alot of sites show vitara's as 8.5:1, when for my a6/y8 w/ .031 h/g zeal shows 7.8:1 and mini me's have higher compression than the stock motor to begin with...

and you would probably need to do some sort of tuning for such the low compression (sub 8:1), thats a large jump from factory 9's:1.
I've been thinking about getting vitara's when I purchase my rebuild kit but I won't be turbo'ing my car for at least 6 months, you guys think that with that super low compression w/ 105300 cam, and some head work it'd be around the same as a stock y8 power wise?

sorry for going off topic...
 

·
yellow bar for me
viper blue 92 eg
Joined
·
3,572 Posts
wha?? That somehow doesn't make any sense. 9.6:1 CR compared to less than 8:1? I don't see how an intake mani would make more than a half a second difference with that big of a cut in CR. The only reason I'm even saying anything is because I'm planning on ordering some shit from you, but I was waiting on the second batch of custom length I beams because I couldn't justify to myself running any lower than 8.5:1 CR. I really didn't want to run any lower than 9, but seeing as this is my DD and I want there to be some room for error 8.5:1 will be fine...but less than 7.5 with the 137mm rods?!!! I don't know about that. But you're saying you got better performance with that low of a CR...I'm kinda second guessing myself. Someone help me out here and explain how that's possible.
id say a freshly rebuilt motor with fresh bearings and no sludge runs better than a 150k+ motor.
 

·
Banned
Joined
·
56 Posts
id say a freshly rebuilt motor with fresh bearings and no sludge runs better than a 150k+ motor.
I would agree...but 9.6:1 compared to 7.8:1. I'm still not understanding how that's possible. If he were to have rebuilt his engine with the same CR and improved his time by .5 second, then that would make sense. Rebuilding and lowering the compression THAT much though, I'm still not understanding how that's possible. I'm not calling him out or anything, I just really want to know how it's possible.
 

·
Registered
Joined
·
566 Posts
I would agree...but 9.6:1 compared to 7.8:1. I'm still not understanding how that's possible. If he were to have rebuilt his engine with the same CR and improved his time by .5 second, then that would make sense. Rebuilding and lowering the compression THAT much though, I'm still not understanding how that's possible. I'm not calling him out or anything, I just really want to know how it's possible.

Old engine could have been down on compression due to worn ring's.

It might have had less compression than the built low comp engine.

My car's a lot slower with the lower compression, you don't notice it till you switch back to a higher comp motor.
 

·
Registered
See above...
Joined
·
13,322 Posts
^Exactly! If I have a chance I'll dyno my hatchback with the freshly rebuilt motor to see what the difference is between a "beat-to-hell" Z6 with horrible ring seal (factory comp) vs the fresh block with SRPs/Eagles (9:1). I would assume maybe a 7-9 hp gain over the 112.7 I laid down.
 

·
Registered
Joined
·
1,737 Posts
my a6/z6 vitara with 7.5:1 compression felt just like a stock dpfi d15, thats what vtec hooked up. no problem at all driving. (first 40 miles unboosted)
 

·
Registered
Joined
·
4,732 Posts
maybe he ran when it was 100 degrees on the d16z6 stock compression...and when he ran the vitaras coulda been alot colder....that plays roll in traction off the line...and power period. so what hes saying im sure is 100% true.
 
1 - 20 of 24 Posts
Top