Compression rate?

ANBU_fto · Post by **ANBU_fto** » Wed Oct 13, 2004 1:02 am

hi guys!!!

i was jus wondering what compression rate can the fto handle, because (if i am right), the fto's compression rate now is a 10.5:1.

what is a safe compression rate for an fto in terms of rasing it.

salacious · Post by **salacious** » Wed Oct 13, 2004 2:44 am

I can't answer your query but I'm almost 100% certain that the ratio is 10:1 (it states this in Mitsi engine manual). I do know someone that had a head skim to raise the compression ratio but I don't know what it increased it to.

ruchi · Post by **ruchi** » Wed Oct 13, 2004 9:29 am

why do you want to raise the compression?

What mods have you done?

What mods do you plan to do?

G_A_V · Post by **G_A_V** » Wed Oct 13, 2004 5:11 pm

i read in the latest hpi ( thye have an article on modding na cars)
that you can pump up most na cars to 13-14 on pump premimum.
I think it was hpi might of been fast fours, i can dig it up for anyone who cares

ANBU_fto · Post by **ANBU_fto** » Wed Oct 13, 2004 7:14 pm

well the turbo was a a no no for me....

so im staying na, and with money i saved well yea...

um i was hoping to get the compression higher, as much as possible. but i dont weant anything going wrong a few days later.
at first i was thinking about 12.5:1, but if i am able to increase it more then i might as well.

GAV can u please dig it up for me please... much appreciated dude thanks a lot guys

and i pan on doing mods such as port and polish, extractors and anything that would help...

jester · Post by **jester** » Wed Oct 13, 2004 9:58 pm

hey man! hows it going!

i thought you were going to Turbo your FTO? why the no no?

Oh and the standard Compression is 10.00

Dunno if you already are but, maybe you shuld try and get you xtractors fixed up first!
I'm still trying to organise mine but as always its $$$ issues!

What happened that guy you know (uncle/mech/friend?)
that could do a custom job for you ?? any news on that??

G_A_V · Post by **G_A_V** » Wed Oct 13, 2004 11:56 pm

yeah sure ill go thgh the mags within the next couple days, and scan it in for you

GPXXX · Post by **GPXXX** » Thu Oct 14, 2004 3:24 pm

ANBU_fto wrote:well the turbo was a a no no for me....

was it my car that scared you too much? LoL...

seriously though', what's with the sudden change??

ANBU_fto · Post by **ANBU_fto** » Fri Oct 15, 2004 1:34 pm

well its not a "for sure non o" for me as far as turbo'n the car, its because i have noticed that a few fto with the conversion have had a few problems with them, and with my budget, if something was to go wrong then i would be dead... plus because off the skyline accident a few days past, my oldies are having second thoughts about it, dont get me wrong i would still love to have it turbo'd, but..... i dont know.... mayber i should start a poll or something.... i mean i still like the N/A, (becuase i just killed a turbo'd skyline..... shhhh), because wheni bought this car i wanted it to stay na and be the fastest na fto....

BAH!!! im so confused now...!!!!

jester · Post by **jester** » Fri Oct 15, 2004 9:05 pm

Stay N/A!! ha

no offence to the lovely Turbo drivers out there!

My 2 cents!

ANBU_fto · Post by **ANBU_fto** » Sat Oct 16, 2004 1:15 pm

yea thanks mate..... still trying to decide.....

ANBU_fto · Post by **ANBU_fto** » Tue Oct 19, 2004 11:54 pm

so guys.... whats the compression rate that an fto can handle... as in its peak point?

G_A_V · Post by **G_A_V** » Wed Oct 20, 2004 12:03 am

I looked for that magazine today, and couldnt find it, i tihnk it was the latest hpi with the guide to tweaking na cars ( that was the only mag i couldnt find)
My Parents own a newsagents so i read all the car magazines, and we sold out of hpi's after i read it so im pretty sure itsi n there

ANBU_fto · Post by **ANBU_fto** » Wed Oct 20, 2004 5:47 pm

no!!!!!

lol

has anyone heard of "ross pistons?

thanks anyway dude....

Post by **smorison** » Wed Oct 20, 2004 8:04 pm

i'm actually working on this... to go with my other major engine mods to happen over the next couple of months...

i'm hoping to be able to get to 12:1 or better without having to strength internals...

hopefully in the next few days i'll have a response from our special technical contacts at MMC in japan

ANBU_fto · Post by **ANBU_fto** » Wed Oct 20, 2004 9:18 pm

ive ask around, and they all say 12.5 is the highest that u will need...

jester · Post by **jester** » Thu Oct 21, 2004 12:49 am

12.5

mmm very interesting!

and thats without stronger internals?
Whats the kinda power/torque gain xpected froma mod like this?

hnm738 · Post by **hnm738** » Thu Oct 21, 2004 1:17 am

i dont understand any of this???
but what effects does lowering or increasing that compression do?

would it have any affect on stock cars?

Post by **smorison** » Thu Oct 21, 2004 8:31 am

hnm738 wrote:i dont understand any of this???
but what effects does lowering or increasing that compression do?

would it have any affect on stock cars?

adjusting compression is only something for us <insert appropriate word here> people

there's no real point in changing compression until you've done everything else... .

compression works like this...

air @ sea level is 14.6psi
air goes into car 14.6psi
air goes through intake 14.6psi
air goes into cylinder 14.6psi
piston compresses air - compression goes up to 146psi (10:1)
spark plug ignites air
big booooom

now if you compress air further to say 12:1 its now twelve times denser than the atmosphere and its all still in the same tiny enclosed area that the air is when the car was running 10:1 compression

changing compression can be done a few different ways, but changing piston shape or shaving a bit off the head....

i have no idea yet what the power gains of this will be.... it's going to be one of my do it and see mods... it will however make the car a little harder to start and run cold... as well as a few other drivability things... which is why i say its really only for those who have already done a lot of mods to the car and want to go further without slapping on a turbo...

what i'm looking at is...

currently: 100kw
intake plenum: 110kw
CAMS: 120kw (guesstimate)
compressoin: 140-160kW (guesstimate)

i still need to do some maths on the compression to power ratios... when i do i'll firm up the power gain... these are all atw figures and without a turbo

(unfortunatley its about the same cost)

GPXXX · Post by **GPXXX** » Thu Oct 21, 2004 12:57 pm

for your sake Steve i will not bother with increasing the compression ratio on the MIVEC if you DO INTEND to slap on a turbo later.

static high compression is not boost-friendly (read: safe) because by the time you add positive pressure (from the turbo) into the combustion, the effective CR would be somewhere close to 16 - 17:1 (if not higher, depending on the amount of boost that you run) :shock: this is why most turbo'd cars have low static CR (around 8.0:1) so they can run more boost reliably...

increasing the CR would be a sensible thing to do for N/a tuning but i don't see the point of going to such extremes yet without the basic NA upgrades first... for the money i would seriously consider a revised camshaft upgrade instead because they will make a significant difference in terms of torque spread and driveability

my 2c..