nevermind! Just needed a lil more fuel pressure!

 

Invest some money in a wide band, that should tell you right away if you are running lean that is causing the knock.

But for reference, how much boost are you running? At 7 psi and aftercooled, I have about 3-4 threads showing on the FMU.

 

^^^ I agree, we need to know what your afr is past 7k. Stock timing map isnt going to be an issue at 10 psi or less on your CT kit, I can attest to that, so its likely fuel related or another mechanical issue. Over heating of sorts will cause this as well. either from the Engine systems or the charger. It might be possible your blower is going bad and producing more heat. Have you noticed any power or performance drop lately? what made you change the plugs initially? Just throwing stuff out there that comes to mind.

Adjusting the fpr richer wont hurt anything and is worth trying if you are at a loss, but what will hurt is if you try and put it back to where it was and end up running leaner becuase you cant check your afr. I would at least try to either count the turns or threads. You can go down to about 3 showing, after that you will hear the engine idle change and start to sputter, this is a signal that your fuel pressure is too high and causing irratic injector behavior. You dont want that

 

Im running the base psi, I think it is 5 or 6 since it is not aftercooled. The power feels the same as before, and I changed the plugs only as preventive maintenance since they were getting old.Do you think a clogged fuel filter would cause this?

Thanks for all your help, its really appreciated!

 

Maybe your injectors are losing efficiency? 7psi is about max'ed for stock injectors. Crank your FPR down all the way, but you'll be boggy down low in order to keep it safe up top. Engine management will help.

 

wow I just looked at the FPR and it has about 4.5 threads showing! Perhaps the previous owner increased the fuel pressure because the car also has a comptech header? Should I increase the pressure more?

thanks!

 

Try one more turn and see if that helps, you may be able to go 1 more turn yet before fuel pressure is too high and your injectors begin to fail, at least you don't have many threads left to count. As I mentioned before, you can listen to the tone and idle change as you reach that threshold of injector failure, You can try to screw fpr all the way in until you hear this and then back it off until the car idles cleanly again. Yes the 4 into 1 header will make the car leaner in the upper rpms, and yes you will bog more in the lower rpms when increasing fuel pressure to make safe up top, a simple vafc will take care of that rich condition down low.

Get a wideband!

 

Im going to install a B&M fuel gauge in my fuel rail, which will tell me the fuel pressure. What is the maximum I can increase the pressure to until the injectors become maxed out?

thanks again!

 

Your down to the point where adjusting by fuel pressure readings isn't going to help you much beyond giving a reference point, because the recommended safety margin is 80% duty or in other words 80psi at redline and all that guage will tell you is where your running at idle uless you run a remote to the cab and have a buddy check it at 9k rpm, thats what you need to measure by, but that still wont tell you what your afr is. The stock CT kit typically requires 85-90psi on stock exhaust, you have a comptech header and maybe a cat back I dont know, you are going to likely need the injectors right up to failure threshold of between 95-100psi to get the afrs right, so thats why I mentioned going by my suggestion of the car idle condition because that will tell you if you are there or not, your injectors may start to fail at 97psi whether as mine may start to fail at 100, your going to be down to tuning by 1psi increments now, which is about a half a turn fyi. 1psi of added fuel might mean running 13.1 vs 12.9. You really need a wide band because if you don't have to run at 98psi you really dont want to. 100psi is the fail point typically fyi, but again it may be slightly different from that on your car vs another.

 

Oh I see.. so if I increase the fuel pressure 1 psi at idle, does that equal 1 psi at redline? or does the pressure increase exponentially? What is the stock pressure at idle? I have a stock exhaust by the way.


thanks in advance!