Hello

I lowered the compression ratio from stock to 8.5:1 with my build. I also went +1mm valves, 276/276 cams, ported the head, ported the intake manifold - throttle body - exhaust manifold (grimmspeed). I also added an adjustable exhaust cam gear. Cam timing is set to 0

Now the car won't idle very well unless I give it the throttle and even then it is running pig rich. What needs to changed in the tune for these upgrades? Do I need to set the exh timing gear differently?

I'm guessing lean out the idle areas of the fuel map?

Not really sure what to do.. looking for generalized changes in the tune when these mods have been done.

Here's a copy of my map in the attachements (was previously tuned by Jestr for a basic stock setup, walbro 255, 720cc injectors, tbe & intake @28 psi taper to 25)

thanks

 

You need to start from scratch. The tune that was on the car is just terrible.

Any reason as to why you set the cam gear to -5?

 

Engine builder set it there. I'm not sure why.

If I may ask, what is specifically is wrong with the tune? I would like to learn please. Let me know what you think! Thanks!

 

Oh hey - double checked with builder and the exhaust gear is actually set to 0 not -5.. my bad

 

I'd send the ROM to a E-Tuner. There are a bunch on here. Id recommend PMing TSCompTuned, they car get your car idling right ect..

If i had to guess, you Injector scaling could be off or in your fuel map it is just too rich at idle. Try leaning it out on the fuel map's.

 

Curious, why the lower compression? You sacrificed performance and mileage with that change yet you added bigger valves and cams... just asking?

 

with lower compression you can run more boost and make more power....

you should know this, you own a turbo vehicle. lol

 

Thank you. I have a few questions.

1. Injector's weren't messed with at all. I had 720's before I rebuilt it and 720's were tuned for in this map. Would the changes I made affect the injector scaling? I don't believe so, but I'm here to learn so please explain. Thank you!

2. Fuel map set at idle is 14.7; I don't know where its at because I only have a narrow band (I know, fail.) Should I get a wideband before even proceeding to make adjustments myself?

Attached are images of my fuel map and timing. I think 6* timing around idle needs to be changed. In my opinion, since we added 2cc of displacement per piston, the timing is off in those areas and needs to be bumped up. What I think needs to be done is add a degree to those 6's, and see how it runs. If it runs slightly better, add another degree until idle is set right. Then go and tune my fuel to hit target 14.7 afr at idle. That should do it right? Just looking for someone who has done this before to approve or review my game plan. I've studied this a lot and have tuned Subaru's before but never adjusted a map for a change in compression ratio

Thank you for your input. It is very appreciated!

 

Yes true but not completely correct. You could raise the compression, run less boost, run more timing, get better mpg, and potentially make more power than less compression more boost..

 

Another member suggested adjusting the idle air control screw, or checking for vacuum leaks and to not mess with timing or fuel.

 

you should never have to mess with the idle air control screw. you need a wideband and a real tune or an e-tune from someone on here

 

So , how did You lower compression? I haven't seen 4g63 pistons lower than 8.5 . And the head should have been milled which will slightly increase comp. I know you say you came from Subura's but mitsubishi tuners usually raise compression.

 

I'm running the wiseco 8.5:1 pistons and stock is 8.7:1 i believe. I'm going to bring it to a tuner and not mess with it myself. If I don't know and have to ask, no sense in rolling the dice with a $5k build lol.

I did read on another post that if the CR is lowered, there will be unburnt fuel. This also goes along with what my narrow band is telling me. While narrow band is junk, I totally agree, it is reading way more rich than it ever read before.

So basically I'm just going to take it to be tuned and not bother with it anymore.

 

Please get your car tuned A.S.A.P. contact one of the many remote tuners on here and have them help you.