Need help want to order pistons today... 9:1 or 8.5:1 pistons or inbetween

[uvamosk]

IM having my ka24de built for turbo, I have option of 8.5:1 or 9:1 Or inbetween Because Im having them custom made... Does anyone know which would be best to run with? I know i can run more boost on 8.5 but then i lose the bottom end. My machinest is worried about headgasket problems with 9:1 so please hurry I Want to order hte pistons here in the next few hours... Im also runing a T3/T4 turbo with .70 trim Super 70 turbo... I have a JWT ECU tuned for 50lbs injecters... So Im looking for max performance from them... thanks

[Import_Ant]

what is your definition of max performance? is the car your daily driver? what will you be using it for? Drag, autox? what are your goals for it basically.

if you want a daily driver/autoX and dont want more than 300 whp I'd go w/ the 9.1:1 cr. it'll give you good driveability and if you want to run any decent sized t3/t4 you can easily keep it out of boost for daily commuting and gas conservation.

if you want more than 300-350whp i'd go w/ the 8.5:1 cr. you'll still be able to daily drive it but you'll have to ability to make a bit more peak Hp while sacrificing initial responsiveness and low-end power.

[uvamosk]

Alright glad you responded so fast, I have t3/t4 .70 trim turbo thats supose to be good for up to 600hp. My numer im shooting for is 400hp. I have bought crower rods, to put these pistons on. Im having them coated to the pistons that is. I will be useing the car for Daily Drivin and also a little Drag, A little Honda and Caviler Street Smaching. Im haveing the engine built from the ground up. Im going with .20 over not to push the walls to thin. Im just wanting to know Which COMp ratio would be best for maxing out the turbo and fuel... Ill have 50lbs Injecters and fuel pump and JWT ecu So im not to worried about having issues with that stuff. Im just shooting for 400hp

[uvamosk]

I was also infored by Wiseco that I can run any thing from 8.5 to 9 so i can get lets say a 8.8 to 1

[nismofly]

50lb'ers wont be good enough for 400rwhp, youll probably need like 72lb'ers up there

aside from that one of the major companies, like ross or arias or something, makes 8.8:1 pistons, those would probably work fine for 400 hp

[uvamosk]

Well 8.5 is to low maybe and 9 to 1 is to high so everyone agree that 8.8 woudl be best?

[HolyShiznit]

I use SuperTech 9:1's, I run 24 psi and am adding a 50 wet shot of spray. I run around DAILY with 350rwhp on pump 92 octane. 9:1, or 8.8:1 is the way to go, it has seemed from what others have done and what I have felt (ridden in) that 8.5:1 is a bit too conservative. Most of the 500+rwhp KA-T's run 9:1 pistons. But to each their own.......

EDIT: 50'lber's won't give you enough head room IMO for 400whp. Get more fuel, I run 75lb'ers.

[uvamosk]

Well ill be running a SAFC ontop of the JWT ecu so I should be good to go if i Want bigger INjecters I woudl think Other than that Im going to go order my 8.8 : 1 pistons right now... I figure if i run 8.8 that will give me a little room to play with but i just figured if im only getting 150hp from 9 to 1 then its going to suck if i go downt o 8.5 that would be like lol 130hp

[HolyShiznit]

Our engines are rated at 155 crank HP with a 9.5:1 stock compression ratio. We do not have 9:1 stock.

The difference between 8.8:1 and 9:1 is completely negligible. Also, with your SAFC it won't matter, the amount of fuel flowing from a 50lb' as compared to a 75lb is insane, not to mention JWT ecu's tend to run rich. My theory is just safely max out the settings that you have and see where you get to. Hopefully you have some way of checking injector duty cycle.

You don't need 400rwhp to have an insanely fast car. On my old, old, set-up at 310 rwhp I could wax most anything I found.

[nismofly]

Anthony i believe is still running his 9:1s, and he just laid down what, almost 530 rwhp?

that should say enough about not worrying about it right there, but id do either the 8.8:1 or 9:1, for me it just depends on the brand of piston and what i get with that brand

[uvamosk]

Well, Im going to run Wiseco Pistons Paying 520$ to have them custome made for the 91 Ka24de. I will have wide band O2 and Ill get something for duty cycle. I Just want to hit 400hp or 350hp with a 50shot of Nitrous.. Im kinda thinking of going with 9:1 but i havent decided fully yet.

But so far here is what I got

ka24de 92'

Crower Rods,Weisco pistons at .20 over,3angle valve job and port and polish,Maybe knife the crank,JWT ecu runing z32 maf,T3/T4 turbo running .70 trimCast Iron Manifold with center placed Wastegate,Turbo XS waste Gate 38mm,Turbo xs BOV,FMICV-LSD Alum Drive Shaft,( Debateing Cams and springs )255lbs Fuel Pump and New lines.SAFC.I am also makeing a custome Intake Manifold uses the stock but gets rid of the bottom part and makes it short runner.

I just have goal of 400hp

or close...

If you can make any other Suggestion through them in...

O side note lol I bought the turbo, wastegate, header, and everything to hook it up for 700$ brandnew so thats why im running turboxs lol

[98s14inaz]

It costs $100 to get a retune from JWT. Call them up, place an order, pay $100 + deposit, they mail you a new chip-takes about a week, install new chip, mail back old chip, get your deposit back. Don't forget that you are also changing the compression ratio as well as the injector size. You will need a new program for that, safc is not adequate to handle such a huge change in variables. Better safe than sorry.

[HolyShiznit]

For the record the only difference between JWT compression ratio tunes are the timing ratios, but even those are sometimes identical. I have 9:1 but I request a 8.5:1 so that I could have ramped up timing to combat the conservative maps of JWT.

[C-Kwik]

Depending on your planned powerlevel, I might go with stock compression. 9.5:1 these days is not high. And so far, the apparent limits of the KA internals do not appear to be the compression ratio itself. Certainly, it's good insurance, to go with a lower compression ratio, but as long as you run premium unleaded, I doubt it will be a problem. Didn't Ivan pull off 400 HP before seeing stock rods deform? I don't recall seeing any detonation related problems nor hearing him say anything about that...

[HolyShiznit]

Stock rods went at 500+whp on his mustang dyno. Stock pistons went at 410ish' whp.