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Slight knock on E85

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henrysan

Proven Member
212
24
Feb 20, 2014
wichita, Kansas
On all my E85 WOT logs I have a little knock, it happens anywhere from 4k-7k rpm. The knock reads only .4* or .7* (1 to 2 counts raw). I have always just told myself it is just engine noise/phantom knock, but now that I am pushing my setup harder I begin to wonder. So is that much knock something to worry about? Thanks
 
You need to find the issue. If its real knock, you need to stop right now. E85 really doesnt knock because of its octane content and cooler burn. If it is real you've more then likely already done serious damage to your motor. Tuning E85 is different then gas. You dont tune for knock. You tune until your gains plateau and then you back off a bit
 
I dont really know how a e85 plug should look so I will post pictures tomorrow of my plugs. I have always had this small knock, back when I tuned for 91 octane and when Ive run low boost/timing on e85 (20 psi/16* peak). Currently at 18* peak timing, 28 psi 11.9 afr. I will try backing off boost again to see if the knock goes away but I have read on this site that e85 needs 16-17* timing up top minimum for correct burn. My spool up timing/afr is 10* at 4k 12.1 afr steadily climbing to 18* at 7k 11.6 afr.
 
Pictures of a plug isnt going to tell us anything unless it was from right after a run and the motor was shut down when you let off.

Anyways, you have too much timing on the hit. You want 5-7* around peak torque and ramp up from there. You dont want lots of timing with high load on the motor. E85 doesnt need more timing, it just responds better to high timing then pump. I personally run 13.3:1 during spool and hold it at 12:1.

Are you even comparing your logs against each other on level ground to see if your adjustments are improving anywhere? This is where a dyno is useful. Hell even loading the logs in VD and comparing the two.
 
Lean it out some. Your timing is probably about right. What plugs are in it? Non projected plugs will want about 3* more timing than projected plugs. Put some fresh plugs in it, and go out an flog it. If it's detonating it should show up as extremely small black specks on the insulator. You can also try and read the timing on the ground strap, but it's hard on an NGK plug.
 
I saw good gains down low on dsmlink which is why my spool up timing starts at 10*. I probably should pull some back to ease load. The plugs are ngk non protruding 7s gapped .025
 
Update, I did some pulls after doing a fuel line mod, replacing the fuel filter banjo bolt and lines with AN fittings kit from automods. I dont know if that is why but I did a couple of pulls afterward and they were clean, no knock during the pulls. Running 28 psi, 45lbs HR of air at 18* timing up top. Car feels strong.
 
keep in mind I would lower the timing down once you start to increase the boost level over 28. Not much just be carefull.[DOUBLEPOST=1411770155][/DOUBLEPOST]
Update, I did some pulls after doing a fuel line mod, replacing the fuel filter banjo bolt and lines with AN fittings kit from automods. I dont know if that is why but I did a couple of pulls afterward and they were clean, no knock during the pulls. Running 28 psi, 45lbs HR of air at 18* timing up top. Car feels strong.
What is your AFR up top now?
 
Thanks for the heads up. I am going to the track for my first timeever for test and tune next friday. I have 3 different maps saved in link from mild to somewhat aggressive. I will do my first run tuned down for sure.[DOUBLEPOST=1411770737][/DOUBLEPOST]My afr starts at 12.1 at 4k and steadily goes down to 11.7 at 7k
 
Thanks for the heads up. I am going to the track for my first timeever for test and tune next friday. I have 3 different maps saved in link from mild to somewhat aggressive. I will do my first run tuned down for sure.[DOUBLEPOST=1411770737][/DOUBLEPOST]My afr starts at 12.1 at 4k and steadily goes down to 11.7 at 7k
Ok thats a great AFR on E85. What fuel pump are you running. I had problems with the walbro 450 at 28 psi not being able to hold the ~77 psi of pressure I needed. If you can punch your fuel pump pressure relief now is the time to do so as you will start to loose pressure at this point if your on a single pump.
 
My fuel setup is pretty much maxed out. I have a rewired walbro 255 @43psi base pressure. I was looking at the walbro 450 but I have read about it not keeping up with pressure like you say. Need to read up about the pressure relief valve punch mod. I know someone local that builds walbro in-tank double pumpers for evos, I wonder if that is possible to make with our 1g sending units?
 
Yea the 450 is out of my car now and the sending unit is at buschurs to get the double pumper currently. I would not get the 450 unless you run race gas or pump gas as you dont need as much pump for that fuel. Im sure there are many u tube videos on punching the relief on the 255s or write ups you can google. The relief is at the top of the pump I think. It takes 15 min to do the mod real easy and you will be safe for now with 28 psi but after that it will bleed if not punched. The 450 does not have the relief location the 255 has the 450 is internal so thats why im going to a modded double pumper. I log my fuel pressure threw link using a sensor on the regulator. I finally said screw it with the tune madness and now changing pump set ups. You should be good to 30 psi with a punched 255 but unless your logging FP I would not go above that.
 
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