Audible knock at medium/ high load at low rpm

[Sekred]

I have had a similar problem, knocking around 2500-3000 rpm, moderate load.
Typically it usually happens like this. Driving around in light traffic, urban situation. Maybe 20-30 minutes of light throttle application and then I give the throttle a prod in say third or forth gear loaded. Engine pings, lift off the throttle straight up. Prod the throttle again same situation, engine pings, lift off again and that's it.
It use to do this about twice and then the ECU makes a adjustment and it won't ping again, even WOT 2000 rpm 6th gear.

Its did this a few times Always after driving around lightly loaded as describe above.
I have changed to a revised Tune recently and it appears Ok now but I am running Toluene and my Octane ratio is around 100 RON.

 

[JPGC]

I have had a similar problem, knocking around 2500-3000 rpm, moderate load.
Typically it usually happens like this. Driving around in light traffic, urban situation. Maybe 20-30 minutes of light throttle application and then I give the throttle a prod in say third or forth gear loaded. Engine pings, lift off the throttle straight up. Prod the throttle again same situation, engine pings, lift off again and that's it.
It use to do this about twice and then the ECU makes a adjustment and it won't ping again, even WOT 2000 rpm 6th gear.

Its did this a few times Always after driving around lightly loaded as describe above.
I have changed to a revised Tune recently and it appears Ok now but I am running Toluene and my Octane ratio is around 100 RON.

Thanks for the input. Yours sound a lot like mine. Not sure I want to have to run toluene all the time though. That stuff is kind of pricey, lol

 

[razorlab]

Or just tune/get tuned the car correctly for how you drive it.

 

[JPGC]

I attempted again this morning to run logs that show my negative corrections while I'm waiting for Justin to respond to my email. It was about 20 degrees colder than yesterday, and sure enough, I was getting negative corrections at first the obviously the ecu adjusted and it quit. This is an outside temperature defendant issue. I'm not surprised though as it was tuned initially in 85+ degree temps. This little turbo spools so quickly, especially when it's cold out. It hits 22.5 psi at 2200 rpm and half throttle.

 

[Sourskittle]

The 1/2 throttle likely is only 1/2 throttle via your foot, the actual throttle plate is prob at 82 ( aka WOT ). Monitor ETC next time you drive, you'd be surprised how easy it goes into wot in the lower rpms.

I read some of the new "sky-activ" mazda's can run wot on the interstate while injecting small amounts of fuel. Pretty crazy some of this DI stuff is.

 

[razorlab]

The 1/2 throttle likely is only 1/2 throttle via your foot, the actual throttle plate is prob at 82 ( aka WOT ). Monitor ETC next time you drive, you'd be surprised how easy it goes into wot in the lower rpms.

I read some of the new "sky-activ" mazda's can run wot on the interstate while injecting small amounts of fuel. Pretty crazy some of this DI stuff is.

All of that you can map via the throttle tables, and look up what percentage request is via actual angle used. Some people like more 1:1 throttle mapping while others like a little bit more at lower load/rpm

 

[JPGC]

The 1/2 throttle likely is only 1/2 throttle via your foot, the actual throttle plate is prob at 82 ( aka WOT ). Monitor ETC next time you drive, you'd be surprised how easy it goes into wot in the lower rpms.

I read some of the new "sky-activ" mazda's can run wot on the interstate while injecting small amounts of fuel. Pretty crazy some of this DI stuff is.

I will check my logs when I pull them off of the accessport to see what the actual throttle plate was doing.

 

[me32]

Sounds like your getting bad winter blend gas that maybe causing your knock.

 

[FORZDA 2]

Sounds like your getting bad winter blend gas that maybe causing your knock.

When you're tuning pretty close to the combustion limits of the engine (me!), any small change in the fuel quality can result in knock/timing retard. I've just seen mine hit the set retard limit of -9 degrees on the last tank. It was quite loud when it happened and it actually blew some black smoke when I lifted.

I'm sure my problem was caused by my reliance on the NOS octane additive and the fact that I filled the tank without adding the NOS first to thoroughly mix with the fuel. I added the NOS afterwards and let the car sit overnight before driving it again. It obviously wasn't distributed enough for the full tank. The current tank was done "properly" by adding the NOS at the pump and filling the tank on top of it. No knock events either...

I'm not accustomed to having to add anything to the fuel at every fill-up (+$10 for the NOS) as my home state of Virginia has 93 octane, superb fuel. It is all 10% ethanol there now, but I have NO problems with knock in my supercharged Miata, turbocharged MazdaSpeed6, Ducati 1198SP, or Aprilia RSV4F superbikes. The Oklahoma 91 octane fuel just sucks. They even have pure gasoline at many stations, but it is all 91 octane crap.

I'm just pointing out my "errors" for others' considerations. I've decided to just back off a bit on the tuning until I get back to a state with decent high octane fuel.

 

[JPGC]

The 1/2 throttle likely is only 1/2 throttle via your foot, the actual throttle plate is prob at 82 ( aka WOT ). Monitor ETC next time you drive, you'd be surprised how easy it goes into wot in the lower rpms.

I read some of the new "sky-activ" mazda's can run wot on the interstate while injecting small amounts of fuel. Pretty crazy some of this DI stuff is.

Sourskittle, what plugs and gap are you running currently?

 

[JPGC]

Well, I got my new revision a few days ago, go it loaded and everything had been good. I put about 150 miles on it with all sorts of different types of driving...up and down in rpm's and light to medium to WOT.....until last night. I was on my way home from work cruising around 70 mph in 6th (2700 rpm-ish). I decided to go around another car at half throttle in 6th and was awarded a light tick tick and a -7.5 ign corr in cyl 1. Of course, I tried to replicate it after the fact on a log with no joy. This was on 93 octane shell (from a different gas station than before). Stock plugs and a .028 gap. It was about 52 degrees outside.

 

[Sourskittle]

I'm running .026-.028 gap

 

[JPGC]

I'm running .026-.028 gap

Well, damn...

 

[Sourskittle]

Mine were actually gapped about there from the factory.

 

[JPGC]

Mine too, I was wondering if you had changed the gap.

 

[Sourskittle]

Mine too, I was wondering if you had changed the gap.

My buddies viper powered challenger came with the plugs gapped at almost .050, lol. But my ford festiva had them right from the factory. I really expected them to be .036 or so.

 

[JPGC]

Sourskittle, i took your advise....I finally found an e85 pump about 40 miles from my house. So, I drove there and pumped 2 gallons in of e85 and filled the tank with Citgo 93. That puts me at e20 to e22 in the tank with a total of around 94.9 octane. The car seems to love it. I made my best attempts to make it do the above (knock and negative corrections) for 40 miles. It is chilly outside as well. In the rpm's that I was getting the random knock, I am now seeing up to +3.25 cyl ign corr. I am also seeing up to and over +5.25 at medium and WOT from 2000 rpm to 6500 rpm. I need to get me a 10 gallon jug and go get some more. Is there any issue running e20 daily until it warms up outside? I didn't have this issue during the summer, when it was warmer out, as far as I know. I also want to get a e30-e40 tune, eventually.

 

[Sourskittle]

I ran 3gal to a full tank for months before i got access tuner software. Razor yelled at me, but the car LOVED it.

2gals to 10gal of 93 oct is not going to hurt anything ever.

Justin can also give you a tune ment for E20-E25 extremely easy. Doesnt have to be a full E25 tune, but it could compensate just for the slighty different fuel stoich. It would take like 4 key strokes.

 

[JPGC]

The plan is to run through this tank of fuel with the e20 mix while monitoring it the whole time. If I continue to see no knock or issues, I'm going to email Justin about a tune update for the e20. At the same time, I'm gonna inquire about tuning for e30-e40. I think he charges something like $75 for the ethanol tunes if you already have a tune from him.
From my 40 mile ride yesterday, I really didn't see any difference in the actual air/ fuel ratio. I though that I would, but didn't. I have a couple of week off coming up and I am gonna put some time in reading through Cobbs documentation on tuning. I need to start learn the ATR software more to actually use it enough to make it worth the $150, lol.

 

[Sourskittle]

If more people had ATR, we'd learn a lot more. I'd personally share a lot.

Its not so much the AFR, its the stft ( short term fuel trim ). The ecu can swing 30%. But tuners like you to be in the 3-7% range. Mostly 3%. I used to see in the 20% range before buying access tuning.

Personally, i think JUST THE BOOST PER GEAR and LAUNCH CONTROL are worth the $150. Never mind the awesome Eth calibrating and timing, and all the other stuff that can slightly be bumped, the way you can tune your car to launch on the street is just awesome.

On a 70dedree day when the road is hot, I can launch harder on the street than the track when it ran 13.3. Of course... It was in the 50's when it ran 13.3