Figure8allday

Hey all great advice needed. I have 2000 GT 4.6 5 speed. MODS: bbk CAI, bbk 70 mm TB, 3:73 gears, cylinders bored + .020 over, and forgred bottom end. Nothing was wrong i just wanted to forge it so i can add a supercharger from american muscle. I screwed up and had shop install 00 cc flat top pistons instead of original 17/18 cc dish pistons. This increased the compression ratio from 9.40:1 ...to.....12.14:1 Thus, now the motor has knocks when i accelerate. So ive only driven it 18 miles since installation. I have Bama tuner but their tunes didnt solve it. Help!!!! Suggestions?????

347mav

110 octane racing fuel and no supercharger. And keep it no more than 180° coolant temp.

Drastang

stock cam?

jwog666

you are done, pull it apart and install the correct pistons, you cant safely supercharge something with 12:1 ratio unless you want to go broke running race fuel all the time

oxfordgt

It's not impossible with the correct top end. TFS heads will solve your detonation problems, their much better design allow for alot more timing. I have much higer compression and run more timing then MBT with no problem. Call comp cams and tell them you are looking for a cam with a late intake closing event to help bleed off some compression. You will also lose boost but pulley for a few pounds more and you'll be fine.

jwog666

not impossible, but with a lower compression ratio, you will be able to actually run significant boost, and will make more power. if you choose to "make it work" with the wrong pistons you will make less power and torque then you will if you fix it the right way.

oxfordgt

This is not true. when done right you will make more power. A simple way to think of it is if your engine in NA form makes 250rwhp(low compression) and you add 14.7 lbs of boost you will make 500rwhp. But with your higher compression with the right heads and cams in NA form you should be around 350rwhp so add 14.7 lbs of boost and your at 700rwhp knock it down to 8 lbs of bosst and your will be around 500rwhp. So to get the same power of a low compression poor quality build you can use less boost which puts less stress on the engine.

jwog666

anything is possible given large amounts on money. the thing you are not mentioning is that at 12:1 you will not be able to run pump gas, and you for sure will not be able to run pump gas with 12:1 and boost. since he isnt building a track car, we should probably keep our advice grounded in the real world. he bult the engine wrong, and after the fact he is trying to cobble it into running by avoiding the obvious solution.........get the correct pistons and fix it correctly.

oxfordgt

I'm pretty sure you don't truly understand how to design an engine but I do. He can run pump gas all day long with boost as long as the top end is set up right. People say bull**** on my engine running pump gas at 12.5:1 compression and making the power I do but it's very easy to do since my dynamic compression is much lower, as long as you understand how an engine works. Hell I'd slap a supercharger on my engine right now and have no problem running pump gas.

jwog666

once again, while it is possible to run high compression low boost, it is a waste of time and money. here is some more info to back up my statement about power output, low compression high boost will make more power than high compression low boost




*sources,Weiand

anything else i can prove wrong for you?