Higher CR without tuning?

[MichaelSuch]

I was looking at picking up some forged pistons/rods combo with an 8.3:1-8.5:1 CR for my build. I know that bumping up the CR can increase the chances of detonation, but I currently have no way to tune. Would I be ok running that CR with the stock ECU? I do have a logger so I could see if it were to start knocking. Is this a bad idea?

 

[toofast82]

The 1g timing map is pretty aggressive. You really won't know how much boost you can get away with until the car is running and you see it on the logger, but it probably won't be much more than stock.

 

[srumel]

You will probably be ok. Just go easy on it and keep it set to stock boost or even just wastegate pressure in the summer, especially if you still have the stock sidemount. Definitely keep an eye on the knock, and if it gets significant a good bandaid fix is to retard the CAS a couple of degrees until the knock goes away, but not much more than 4/3degBTDC. I have a JDM (I know, I know) motor with 180psi across all four which is roughly 8.5:1 I think and I haven't had any major problems with knock.

 

[MichaelSuch]

Boost I don't really care much about right now, it's just a 14b. I'm slowly working my way up and am looking at getting it to around a 300HP car, but I'm just trying to take my time. I don't have the funds to really get this thing moving yet. I do have an MBC so I can lower the boost, I don't really plan on driving the car hard at all until I can get Link and some fuel mods. Also I forgot to mention that the head I had work done to has not been shaved or anything neither has the block so the compression ratio shouldn't be any higher than what the pistons say they are correct?

 

[JusMX141]

A 2G has an 8.5:1 compression ratio stock, although their timing map is not quite as aggressive as that of a 1G. A 2G also has a smaller factory turbo, although if you're running wastegate pressure on a 14B you should be fine.

If nothing else you'll gain a little off-boost torque, as well as spool your 14B a little quicker than normal; this was the goal with the 8.5:1 pistons and smaller factory turbo found in the 2G's.

 

[Side_Show]

i'm running 9:1 CR wiseco pistons and bc272 cams on stock 14b boost (str8 to wastegate). I don't wanna raise the boost until i get some type of management system. I have an Aem wideband but still didn't hook it up yet. Felt a big difference in performance compared to my stock 7.8cr pistons and cams.

 

[MichaelSuch]

i'm running 9:1 CR wiseco pistons and bc272 cams on stock 14b boost (str8 to wastegate). I don't wanna raise the boost until i get some type of management system. I have an Aem wideband but still didn't hook it up yet. Felt a big difference in performance compared to my stock 7.8cr pistons and cams.

9.0:1 seems pretty high, do you have a logger? Also are you DD'ing this car?

 

[u2slow]

You`ll be OK and you`ll love it

 

[myturbo]

the stock crank and rods has been proven to 600+awhp , on a 100% stock block.

At the most, just get some pistons, and bearings. i would probably use EVO 8-9 pistons.

 

[Side_Show]

9.0:1 seems pretty high, do you have a logger? Also are you DD'ing this car?

no i don't have a logger and yes it is my DD. I'm not raising the boost until i have something to tune with and hook up my wideband. I don't want to risk blowing something on my setup which only has like 6k on it. I'm just using regular 93 octane, wish we had E85 here.

Edit: I also i forgot to mention i don't have any fuel mods yet. Soon i should have a 255 walbro and fuelab FPR

 

[MichaelSuch]

Well the earlier Evo's came stock with 9.0:1 CR, so it's not that high I guess. Was the difference noticeable when you put in the high compression pistons? What rods are you using?

 

[Side_Show]

i'm using eagle h-beam. Well it was noticeable but at the same time i also did redo my whole engine. Bored it .20 over, deck head and block. Plus regrinded stock valves, revised topline lifters, new rockers and the bc272 as stated before with BC springs/Ti retainers. All my other little mods in my profile i did before.

 

[tkelly27]

Did you get my PM? My internet has been screwy