lower Compression Ratio advantage?

if your not going force induction whats the adavantage of having a 10:1 cr?

 

Compression Ratio Calculator

I do Beleive that a Normal Engine Issued by the Manufacture is Not higher than 10:1 the Average Car is Around that Compression Ratio, so the Advantage would be Longevity and Reliability of the Engine,


Click Here to Calculate

 

higher compression means more heat but sometimes u need lower compression if u are pulling in more cold air and injecting more fuel but then again it all depends on your heads and cams and lots of stuff goes into finding the perfect tune and setup for your application

 

what kinda motor are you runnin?

 

i am running a 95 GSR OBD1 soon to have JDM ITR header, K&N for street, HKS for race days. the reason i am asking this is becuz people told me to put high compression pistons (i am goin all motor) but i dont want to rebuild the bottom end if i dont have to. my compression in all four cylinders are 260 psi+ and i think that's excellent. i am lookin to get 180+ HP to the wheels if not better one day(if i run a 13 sec 1/4 i will be happy). the car is made for autoX.

 

260psi in all four cylinders means that your motor is running strong. right now your c/r for the gsr is around 10.1:1 wich is pretty low. if you want to run 13's in a quarter mile i would build your head and bottom end running around 12.0:1-12.5:1 c/r and some massive tunning. this motor could be streetable just depends on what cams you run and how good of a tuner you have.

see i a planning on doing a LS vtec build. right now i only have a b16. the LS internals are really strong but the pistons are shit considering there so low c/r and just shit haha. so when i do this build im gonna run the ls block, ls crank, ls rods, arp rod bolts and either ITR or P30 over sized pistons. which i will have around 12.0:1 c/r wich is about were you need to be on a lsvtec. and 12.0:1 c/r is a good racing and street drivable compression ratio for your motor. this was just used as a example.

so on your motor you can run the gsr block, gsr crank, gsr rods, arp rod bolts, and just get some CTR over sized pistons or p30 over sized pistons to be in the 12 c/r range. you do need to do some search because i am not searching as i say this i am just doing a estimate knowledge base.


if you have any more questions feel free to ask and if i am wrong with anything please feel free to correct me.

 

i wish my factory ratio in my crv was that high, factory i think it about 8-8.5:1

 

with a Gsr motor you can run in the 13s with your stock internals. depending on what you have it in. tuning also goes a long way in making power all motor. the one in my 99 coupe ran a best of 13.93 and all it had was intake header exhaust and intake manifold with a basic tune(176whp). then i went poor man status on it and that was one of the best builds ive done. throw a b16 head on it with CTR cams and bolt ons and you will be fast. then i took it a step further with CTR pistions and i was runnin low 13s with no traction until the end of 2nd. if i had traction and i couldve ran high 12s easily and that was on a pretty basic tune(205whp). if i were runnning a max tune i couldve had more power. a tip for goin fast through the 1/4 get a b16 tranny. the short gears love the street and track but hate the interstate lol. 80mph vtec in 5th.

 

^^ nicely said man. i always wanted to do a poormans type r lol

 

whats the benefits with having the b16 head? is it just for the pnp work? or is it that you can find ITBs for that head easily. becuz i was thinking for doing a mild pnp (maybe even just a mild porting job) on my gsr head.

 

porting the gsr head isnt a bad idea but i would go with the b16 head. not only cause i have compared the 2 many times lol but here is why.....

 

the b16 head has bigger combustion chambers than a gsr. the overall design flows better. if you ever decide to use pistons with a huge dome(high compression) the gsr head with its flat quench pad will have some issues lol. the b16 on the other hand can handle a pretty high comperssion piston without any problems. think about it the pr3(b16) cast is used on both the civic and integra Type R. so adding a b16 head to your gsr block will bring you that much closer to the real thing.

 

hmm but addin the b16 to my b18c1 block will lower compression tho correct? so you will need to add pistons to bring it back up to high compression correct? thats a poor mans itr i believe, but what im sayin is i dont want to change pistons unless i have to. i plan to shave the head, and from my calculations i would still but in the high 10's compression. so i just want to pnp the gsr's head.

 

before i changed my pistons out for the CTR 11:1 i ran stock gsr pistons with my b16 head and buddyclub headgasket. the stock gsr pistons are only 10:1 and with my b16 head and buddyclub headgasket i was runnin 10.3:1 which is a tad higher than with a stock gsr head. and that was also before the port job.

 

i am planning to shave my b18c1 head, and from doing calculations i will be in the 10.8:1 zone of compression. any pros and cons about shaving the head? i already know once u shave you can go back, but im not worried about that. and having a 10.8:1 cr will basically make my motor similar to a USDM ITR correct?

 

10.8:1 is higher than a USDM ITR. and shaving the head isnt a bad idea but like you said once you do it there is no going back and if its not done right it can cause some serious issues.

 

See my other choice was putting JDM SiR pistons or USDM ITR pistons in it, it will still keep me under 11.0 cr. Will the 10.8 cr act mostly like an JDM ITR motor? also, call this bogus or not, a co-worker of mine who used to work in a shop said a motor with a lower cr(10-10.5) will "wind up" faster than a motor with higher cr(11.0-11.5). have no clue what he ment by wind up but maybe it gets to higher rpms faster? but maybe you can help me out there.

what did you gain after the pnp btw?

 

its just that most really high compression motors make their power at really high rpms. like a freind of mine used to have a crazy super high compression b20/vtec crx that would pull until a 12,000 rpm redline. it was only for the strip cause it could only run on race gas. anything under 13:1 can get away with pump gas.

 

with the type r cams i ran the pnp gave me a solid 10whp in top end during tuning