anyone know what the compresion in a b18c1 is after you mill the head .02 ? i cant remember the exact number.. the max is like .4? its half of that

thanks

-sam

 

i believe milling your gsr head 0.020" or "twenty thousandths" should raise your compression approx. 0.5 or in you case it would take you from 10:1 to 10.5:1. this is based on calculations i made when my head was milled thirty thousandths - raised me 0.77 or what i call 10.8:1. this was confirmed by group-a when i picked up my car. hth.

 

what pistons should i drop in to give me a good compression now that my heads milled 2twenty thousandths

 

i'd say itr/ctr pistons would be good

 

can u have more agressive cams with a .4 mill???

 

with head milling and aggressive cams you will have to watch piston to valve clearance...

 

could i pull off toda Bs with 2 mill?

 

Really? .77 over stock Gs-r compression? I have mine milled at .030 as well, I was told it would be around 10.4? What was your psi? I had about 220 all around?

 

i'd really like to know the real answer. i'm using these old calculations: http://integra.vtec.net/engine/motorbuild.html
some people here tell me there are much better ones than this but that's all they said. when i picked up the car, group-a said 10.8:1 was right but who really knows...
so someone here must be able to give us a real number, keeping in mind that any calculation on paper is merely an approximation.
another source for related info is the specs quoted by manuf. of thinner head gaskets, although i think they're numbers might be a little high. if i remember right(king-motorsports site seems to be down right now), mugen says they're 0.47 raises you point four or point three, stock being 0.7mm. i keep running into people who think stock is closer to 1mm, but my helms says point seven. anyway convert that to inches, blah blah blah...ok, now i'm confused...

 

a very very rough estimate is that a 0.1mm = 0.1 cr

0.030" = 0.762mm

which jives with the .77 i calculated.

looking at the toda gasket (using toda pistons) for B18C5 they list:
0.6mm 12.3 : 1
0.8mm 12.1 : 1
1.0mm 11.9 : 1
http://www.todaracing.com/B16A.html

this jives with the 0.1mm=0.1cr

someone who actually knows the real deal for a fact, please correct me/enlighten us

 

Hey Go,

Remember we tried to get an answer on this before.

I must have gotten confused and thought that each 10 thousandths = .1 compression. That's what I've been going by...

What you're saying here makes sense to me, fwiw

Soooooo, if I have JDM ITR pistons in a GSR with the head milled 20 thousandths what would my compression be?

I've heard that the JDM pistons get you to 11.4:1. If 20 thousandths is approx .5 compression, am I at 11.9:1??

Thanks,

FB

 

Oh,

I need to get a compression and leakdown test. Hopefully my new bottom-end is holding up ok. I'm concerned since my TQ (120 with 177 HP) from the dyno was so low .

With such high compression, I should have very high numbers, right? I know it's also important that they're even. Probably something like 250 in each cylinder?

Any rule of thumb or estimate would be greatly appreciated.

Thanks,

FB

 

oh no, not again! heh heh
the more i look into this the less i think i know.

i don't feel like looking it up but if i remember, the jdm itr (do we need to specify B18C5 now in this post rsx world?) is 11:1 vs usdm itr at 10.6:1
my logic tells me that putting jdm itr pistons in a usdm B18C1 would give you 11:1 but is that how it actually works? are there other factors like head volume cc quench area combustion cloverleaf welded hand polished knife edged...

i gotta go eat something...

well first rule of cr test is you want consistency and use this to locate and isolate problems. i don't know if you'd be as high as 250...i just don't know. i'm pretty sure you want to be over 200, in general. (stock?) let's hear from those engine builders that are supposed to know all this ***** and have every cel# number memorized like #7 is tps

 

Hehe,

The JDM ITR (let's leave RSX out for now ) pistons in a GSR motor yield a little higher compression than in the USDM ITR because of the head. For example, ITR head on B18C1 block actually lowers compression.

Thanks for input on compression, I better be over 200 or I think I'll probably cry. If I'm ok, gotta figure out where all my TQ is going. If not, gotta figure out if I want to deal with the pain of redoing the bottom-end or what other alternatives are out there.

I know I should get at least 10 more HP with a good header/cat/exhaust. Gotta decide between Spoon, Toda, SMS, HiTech etc. Any one of them should help a lot over my pitiful Neuspeed 4-2-1...

Take care,

FB

 

ok, that first part makes perfect sense. i can think better post-mcnugget...

please don't put much weight on the "200" i offered. where are those super-genious-expert-peeps??? (probably all dirty and greasy and working, not sitting behind a keyboard, lol!) and btw, my celly was throwin' lots 'o lucky sevens last night...(tps wasn't positioned exactly right...)