more newbie tuning

[droppinbottom]

ok i am learning on tuning a dsm and have a few questions. the shop that built my motor made a few pulls with my pocket logger in 3rd after the motor was broken in and adjusted timing so no knock would come up.

i just installed my safc-II and my lm-1 and started makeing a few pulls and adjusted my a/f so i am holding around 11.5. well tonight while i was logging my a/f i made a few pulls logging with the pocketlogger aswell and i was getting anywhere from 0-17 counts of knock. i noticed the knock seems to start around 4500rpms.

im pretty much stock as of now. im @14psi, 3" turboback, 255lph.

i am going to do a boost leak check tomorrow after i get off work but im wondering if it could be something else causing the knock? should i pull a little timing or add more fuel?

thanks for the help

 

[ihaterice]

you will need to add more fuel and that certain rpm.

 

[titogs95]

BTW you need an AFPR. (if you don't have it). you are over running your stock fpr.

After you check for boost leak.Please, try to post the logs. try to rich those point that seems to be knocking. (Do you have any fuel controller?) if still knocking you might have some weird phanton knock....

If all that fails try to run 100 octane gasoline to see if you are having real knock or phanton knock.

 

[droppinbottom]

since all of my tuning background has been done on n/a cars it was easy to shoot for a certain a/f ratio. i will add some fuel back up top and see if the knock goes away but that will probably put me into the high 10's to low 11's on my a/f ratio's.

correct me if im wrong but isnt around 11.5-12.0 supposed to be correct for a fi car?

thanks again

 

[bird man]

yes 11.5 will be perfect. it also gives a little leeway if you spike just a bit.

 

[playitlouddsm]

I would say when your tuning your car, you shouldn't be shooting for a certain # for af ratio. You just need to figure out what works with your set up. Run as lean as you can with as close to zero knock as possible.

 

[exiletalon]

I would say when your tuning your car, you shouldn't be shooting for a certain # for af ratio. You just need to figure out what works with your set up. Run as lean as you can with as close to zero knock as possible.

very well put,- tune your AFC too the limit that you own- if you can run 20 psi on pump gas then go right ahead- you did something right!

 

[bird man]

yes...run as lean as possible...on my last dyno I leaned out to 13 and somehow had hardly any knock. I had to ask myself " do i turn it down a bit to be safe, or do i leave it like this and come back to my pistons being melted after a few hard runs?"
I have always been tought that after you pass 12.2 Your looking for trouble. Knowing my car used to spike periodically i played it safe and kept a straight 11.5 and have had no problems. I would rather be a little rich than a little lean.

 

[jepherz]

I pretty much disagree with the above posts. When tuning, running more lean isn't really a power adder. The fuel you are adding beyond stoich is mainly to suppress the heat that is created from the combustion. In certain RPM/Load ranges, I think you should tune for an AFR. I can't think of any reason why a wideband o2 would be necessary if you weren't trying to set your AFR to a certain ratio.....?

On my car, after my boost is set where I want it, I tune my fuel tables to specific AFRs in different load ranges. (11.5-12.5) I use the wideband to find out how far off the reading my ecu is getting is from actual AFR. After that, power is all in the timing. Add timing for more power and subtract it if you're getting knock.

I know that no car is the same, but there is also nothing wrong with using other's similar setups to help you tune. Not many professional tuners will go into a tune blindly; they usually have other similar setups to use as reference.

Not saying anything above was wrong, that's just not how I think it should be done.