I heard that 12.5:1 isn't streetable. Can't I run 93 with that, and not get knock?

I am planning to do a 12.5:1 with a 3.5 bore (0.060 extra).

What octane gas would I have to use to run this?

Thanks

~Tacoman

You would need to run an aftermarket ignition to retard timing a little...and the higher octane you use the better. i "guess" you could call it streetable, but i dunno anyone who has tried yet. you would definitely need to upgrade injectors,fuel pump and all the normal stuff. id also upgrade your entire valvetrain also.

www.TeamKLR.com
1997 Silver RS
12.3@118mph,20psi, race gas(drag radials)
Wiseco 10.5 Pistons
Eagle Rods
T3/T4 Turbo
Custom FMIC
Greddy Exhaust
440's

I've read at the neons.org boards of an individual who had this setup and wasn't ever able to get his running right.

Apparently, with that high of a compression, he didn't have the ability pull back timing enough to prevent the engine from knocking.

Some people may recommend 12.5:1 compression as easy to get, free all-motor power, but some requisite tuning is necessary. Yes, that's true, but an emphasis has to be made on the tuning part of things. Many times, we think of tuning as simple adjustments mads with piggyback type add-ons that allow us to add a littel fuel here, and pull back some timing at the higher RPM's. But the necessary tuning with a 12.5:1 CR setup may require something more than merely a MSD, a FPR, or something of the like.

You may very well need a standalone to get it done, to even run properly at low rpm's, much less than 7200rpm's, to take full advantage of the bigger "squeeze" in your combustion chamber.

little off topic but i was gettin ready to buy the small block off rpmxtreme's site, what comp ratio is good for a street car? 10.5:1???

I'm planning to buy Kiku's pistons, which he said he was running 12.5:1 on his 97 (or 98), and he said he didn't retard the ignition.

Is it REALLY needed?

~Tacoman

12.5:1 is defiantely high. Back in the day (mid 80's) getting a Mustang 5.0 with 12.5:1 compression was an engine option! I think if you could get up around 10 you'd be in a good spot. Not necessary.


.

1999 GS Special Edition

You can do it with the right fuel and proper ignition timing. You will probably want to AT LEAST have 30 lb injectors, MSD, SAFC, and a set of cams to give you enough air in and out of the engine for that high compression. I would also recommend using ARP head studs.




__________________________________________________________________________
Car Sold


http://hometown.aol.com/ohshootuhh/
www.Fast420A.com

Then would i be better off goin 8.5:1 or 10.5:1 and what kinda difference would there be between the 2?

I would say with you being an A/T, turbo or non turbo I would do 10.5:1 minimum. Go higher if you aren't going to turbo or if you want to spend a LOT of money for an EXTREMELY FAST and fun to tune high compression turbo motor! }( }(
________________________________________________________________________________________
Car Sold


http://hometown.aol.com/ohshootuhh/
www.Fast420A.com

I personally wouldn't go under 11.5:1 if you are going all motor. 10.5:1 will give a little extra, but I'm probably not normal, I would raise to 10.5:1 to turbo.

11.5:1-12.5:1 for NA, but you have to know what you are doing, there will be some tuning involved. May have to pull timing, and you'll have to watch that fuel.

When you get higher in power output, be it NA, or turbo, or nitrous; fuel and timing play a more crutial role, expect to spend some time tuning the car.



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

What about using water injection along with 12.5:1? You would get the same benefits as the turbo guys that use it. Better detonation resistance, increased charge air cooling etc... and then once you got the tuning down, if you decided to go turbo, having the water injection available puts you in that much better of a position.Just a thought....

Current Mods:
Flowmaster Muffler
Ghettofied PVC intake w/K&N Filter
Platinum +4 Plugs
MSD Super Conductor Wires
1 Heavy Right Foot!!!!!

Water injection would only work on an engine that doesn't run much like race only. Otherwise you'd need a huge water tank or have to stop and fill it up every mile.



________________________________________________________________________________________
Car Sold


http://hometown.aol.com/ohshootuhh/
www.Fast420A.com