ratio for turbo

[hicas187]

i have a 92 240sx and i want to go forced induction i was wondering what type of ratio i should go with that would suit my needs. i want a lot of boost with out doing any damage to the motor i need to know if i should go with 8:1 or a 8.5:1 compression ratio any help would be great thanx

[Craving4Boost]

your question is to brod...please be more detailed on whats "a lot"

[hicas187]

about 20 pounds of boost.

[Import_Ant]

it's not really the amount of boost that is important it is the volume of air and efficency the turbo is working that matter more. basically as stated many times before you have to work based off of a goal. you want to make X hp from your motor not get to x boost. if you orient your question like that you will be able to get alot more helpful responses. 20 psi of boost between a T3/T4 and a T70 are going to net a HUGE difference in power.

try and figure out a power goal for your engine but it is usually agreed that the lower the compression ratio the more you are going to lose in lower RPM responsiveness but the more potential you have for top end power. if your car is a daily driver you might not want to loose too much of that low end response.

[:: orion ::]

9:1

Tuning is so advanced these days, runnig low compression is a band-aid for poor tuning...or what the OEM manufacturers do to prevent damage from some idiot running 87-octane in his new Evo 8.

For you, who's going to tune precisely and always run good gas...9:1 is perfect.

- Brian

[MarkEmark]

9:1

Tuning is so advanced these days, runnig low compression is a band-aid for poor tuning...or what the OEM manufacturers do to prevent damage from some idiot running 87-octane in his new Evo 8.

For you, who's going to tune precisely and always run good gas...9:1 is perfect.

- Brian

Agreed, 8:1 would be extreme overkill....The new 2.0 liter Audi turbocharged engines run a 10.5:1 compression ratio....They are also direct injection though and pretty sophisticated as far as engines go, but you get the idea.

[hannibal]

Agreed, 8:1 would be extreme overkill....The new 2.0 liter Audi turbocharged engines run a 10.5:1 compression ratio....They are also direct injection though and pretty sophisticated as far as engines go, but you get the idea.

Wow, thats freakin high compression!

I always wonder how much those injectors cost on a motor like that...

[hicas187]

well if i wanted to shoot for like 450 to 500 hp would that be realistic or not? and if so where would i start? would pistons and rings be a good place to start?

[Import_Ant]

that is totally realistic on the KA block. you're talking upgraded pistons, rods, cams, injectors, MAF and good tuning method (standalone preferably.)

someone want to second that?

[scheffler]

you also need a turbo

[240DRFT]

if i were you i'd go for a lower goal like 350 rather than 500

[WDRacing]

In the end, you will make more power by adding boost and lowering compression. But thats just mathmatics, the driveability will go down the crapper off boost with a turbo big enough to justify a 7.5 or 8/1 compression level. Me, I'm staying at 9.5 and will use methonal for anti-knock rather then lowering the compression.

WD