d16y8 with vitara and custom rods. I just built the motor. everything else is stock. 9:1 compression, stock exhaust, cai

trying to tune partial throttle. seem to be doing fine but still need help.
everyone is saying tune for 14.7 but this is not the case. im not tuning wot, wot is pretty simple and i wont need help with that

i got a ton of datalog. started from a stock z6 map and set timing at 16 then set my dizzy.

my question is regarding afr while accelerating. can anyone give me info on what afr i should have at what psi

like say
-20psi im pretty much lean at 16:1 afr
-20 to -17 about 15:1
-17 to -14 about 14.7:1
-14 to -5 about 13.5:1
anything above that i have not tuned yet because i dont hit wot

now it seems the car is slow, sluggish and has a couple what seems to be flat spots.
i would like to fix this and get slightly better acceleration part throttle. i know im running lower compression but i think afr plays a big role because i can feel the cars acceleration at different afr

what would really help is a say a datalog from a bonestock car to see the afr so i can imitate that

 

Add/subtract fuel to where your car likes it the best. Pretty simple. Not every car will be the same.

 

Or save the money and cough up a real tune at Pure Tuning or *gulp* Speed Industry (though I understand if you don't want to take that particular route.

 

Your power is made with tuning fuel + timing. You're only working on half of it so far and your setup is modified from stock so it doesn't act quite exactly the same.

 

AFRs are the least of your problem dude, 14.7:1 below 750mBar, 13.5:1 from there til 3psi. Add timing til it knocks, then... rebuild the motor. :D

 

ehh im one of those diy guys. and i do alignments at home

also built a motor for a friend and we called speed industry like 9 time and scheduled how many appointments for a dyno tune and never got on the dyno till this day. been like 5 months. probably never going there for anything. we were actually o our way one time for a scheduled dyno and when we called they said they were too busy

 

yeah i understand but im not trying to make power or anything just trying to drive it through winter as im doing now. and i will tune timing once i get comfortable with the fuel maps
I built this motor basically so i can learn to tune. if it blows i got a couple more motors lined up so i not worried about blowing. and it will blow in the summer i can guarantee that.

 

Depending on the combustion chamber dynamic, fuel quality/ amount/ octane, temperature, etc. fuel will burn at different rates. You have to ignite it a few degrees before the compression stroke reaches TDC in order to get the full benefits during the proceeding power stroke. Advance ignition timing to get the peak combustion power point closer to TDC.
With that said, if you ignite it TOO far in advance, you get a massive explosion in a very small space that has nowhere to expand, which produces engine knock. Sounds a lot like your engine inhaled a bunch of ball bearings.
Very, very basic explanation, but I'm sure you know how to proceed from there.

 

are you trying to teach me something. this is basic knowledge no. im not asking how an engine works

 

v8killaz, try tuning the part throttle area around 14:1. This should give a nice smooth and responsive(ish) feel. If it doesnt then your going to have to tune the ignition timing properly on a dyno and hope that picks it up.

 

You have the general idea about drivability tuning. You will need to see where your engine likes the fuel ( by monitoring knock) during heavy load/low rpm. Some engines will see knock in the 13's where 12.8 or richer cleans it up. That is just the fuel, which is basically simple to tune. Where you will find yourself spending allot of time is on the ignition timing. Tuning timing will help your response but you will need to keep a close eye on knock voltage.

Lawrence

 

Spend some time research how to read a spark plug for ignition and fueling adjustments and youll be way ahead of what a lot of people know about tuning.

 

sound good

im tuning partial throttle not wot

yeah i read alot about plug reading. all the v8 guys tune like that. its just i dont have a clue on how to do it for partial throttle. wot makes it easier. put new plugs in and do a pull then check. i dont see how i can do this same method partial throttle

 

the white porcelain has layers, for lack of a better term. the top of the porcelain (the part that stick outs), is for idle. a little bit farther down the porcelain (which is essentially a higher cylinder pressure area) and is your acceleration and mid-light loads. the bottom of the porcelain is WOT. you are looking for a nice fuel ring around it.

Unless you are running a decent compression ratio, you are going to have a hard time running into detonation issues under mid-light loads. This is where an EGT gauge can help give you a gauge of combustion temps so you can play with fuel and ignition to yield the best efficiency.

 

ok i see. never looked into an egt gauge. i might as well though.

could this be used for efi also. im assuming both systems use the same techniques
http://www.4secondsflat.com/Spark_plug_reading.html

 

Pretty basic explanation that will get you started. With a trained eye u wont need an egt gauge

 

you were asking what AFRs to use - most people need basic knowledge with that inquiry. if your timing is correct there is no reason you shouldn't be able to tune partial throttle at stoich. Unanimously, you need more timing. As far as plug reading, all of that is null if they're the wrong heat range.