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Discussion Starter · #1 ·
So over the past few weeks I've noticed my LCDBC showing a few counts of knock here and there, on the "peak boost/knock" screen. Every time I've seen it confused me because the driving leading up to seeing it wasn't even in boost or driving aggressively. Today I narrowed it down to when I am turning the car(left or right) more than about 45 degrees and I'm on the throttle either accelerating out of the corner, or downshifting and rev matching going into the corner. The knock counts are usually under 10 as shown on the LCDBC, but sometimes have shown in the 20s if I take a corner hard. It is usually pretty intermittent but seems to be the most consistent when I'm starting from a stop, and shifting into 2nd while still turning. If I'm in gear and "shake" the car with sudden steering inputs it does not send off any knock counts.

In a straight line I can stomp on it in 2nd/3rd/4th and it will hold 13lbs to redline with no knock reported whatsoever. Last pressure test shows the only boost leak I have is a small one at the BISS screw, and my LCDBC reports around a -9.5psi at idle with AC off(so around 20inHg). I do know my stock BOV is bad(it hoots sometimes), and I have a replacement that I need to get welded on, but don't really see how it could be the cause of this. The fuel pump relay bypass has also already been completed so that isn't the problem either. Any ideas?
 

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If it is just knock counts and not knock sum (like the ECU sees, from 1-26 max), then you have nothing to worry about. I used to get knock counts in the 20s on my SAFC2 while just commuting on the highway. This was especially true during really hot weather. If you are getting "real" knock [sum] then i would want to investigate a little further. FWIW i have also seen nonzero knock counts on my SAFC2 even when knock sum is zero as reported by the ECU (monitored/logged through BlackStealths OBD2 converter and Torque app). As you mentioned the most important thing is no knock during high load situations.
 

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The problem is I'm not entirely sure if the LCDBC shows "knock count" or "knock sum". I mean it is getting it's information from the ECU...so would it be knock sum?
I dont use LCDBC so i am not entirely sure which one it is reporting. You may have to search or ask BlackSealth directly.
 

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Discussion Starter · #5 ·
From the LCDBC manual:
The third value is knock sum reported from the ECU.
So it seems it is knock sum. I went ahead and ordered a serial to USB cable. Now to find a laptop so I can actually log with. But the question still remains, why does it tend to knock when turning but not in a straight line?
 

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From the LCDBC manual:

So it seems it is knock sum. I went ahead and ordered a serial to USB cable. Now to find a laptop so I can actually log with. But the question still remains, why does it tend to knock when turning but not in a straight line?
Interesting, i also confirmed back in my torque thread where blackstealth said "Knocksum range is between 0-26 for 3S cars. SAFC2 reads only raw knock voltages, and no filtering -- this is why it is majorly different. "

Not sure i have a good answer to your question... Do you experience any NHV (noise, harshness, vibrations) under the conditions where it knocks? Based on your description it sounds like it could be some motor/drivetrain mounts where the knock sensor is picking up vibrations at a certain frequency. That could be very difficult to track down.

It would be interesting to see if the ECU is pulling timing when you get that knock, since the ECU should see it as "real" knock. Do you have the capability to log timing (once you get the cable)?
 

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Discussion Starter · #7 ·
Not sure i have a good answer to your question... Do you experience any NHV (noise, harshness, vibrations) under the conditions where it knocks? Based on your description it sounds like it could be some motor/drivetrain mounts where the knock sensor is picking up vibrations at a certain frequency. That could be very difficult to track down.

It would be interesting to see if the ECU is pulling timing when you get that knock, since the ECU should see it as "real" knock. Do you have the capability to log timing (once you get the cable)?
Nothing out is really out of the ordinary when it happens as far as I can tell. And yes it should show timing advance if I use something like evoscan.
 

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interesting, I was seeing "phantom knock" from the lcdbc too especially when i leave my house. I never checked to see if it was happening while doing sharp turns, but I guess that is possibly when it happens to me. I had assumed it was some pot hole in the road but I will have to watch it more closely.
 

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Discussion Starter · #9 ·
interesting, I was seeing "phantom knock" from the lcdbc too especially when i leave my house. I never checked to see if it was happening while doing sharp turns, but I guess that is possibly when it happens to me. I had assumed it was some pot hole in the road but I will have to watch it more closely.
How exactly did you determine the knock was phantom? Also I've definitely noticed it showing up more often when I leave my house as well.
 

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everyone on this site told me it was "phantom knock", so I just assumed they are all right. :)

I have to take a number of turns out of my neighborhood.
 

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Discussion Starter · #11 ·
everyone on this site told me it was "phantom knock", so I just assumed they are all right. :)

I have to take a number of turns out of my neighborhood.
Hmm okay. I wonder if I got the infamous 1g leaky ECU capacitors. I can pull it and check but I would think it would be showing the knock all the time and not just turning.
 

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Hmm okay. I wonder if I got the infamous 1g leaky ECU capacitors. I can pull it and check but I would think it would be showing the knock all the time and not just turning.
If you are concerned about knock being real, you can always drain/use all of your gas and put a few gallons of race gas in to see if the knock goes away. This is exactly how i diagnosed my "real" knock as being fuel related. I was getting crazy knock (up to the max of 26) anytime i started to go into boost. I ran my tank pretty much dry and put in 4 gallons of 100 octane and did a pull - knock was gone. Turned out i had some clogged injectors, which was causing a few cylinders to run lean despire overall AFRs being rich.

Yours truly does sound like phantom knock, especially because of the circumstanes under which it occurs and the fact that it does not occur when doing WOT pulls.
 

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Discussion Starter · #13 ·
If you are concerned about knock being real, you can always drain/use all of your gas and put a few gallons of race gas in to see if the knock goes away. This is exactly how i diagnosed my "real" knock as being fuel related. I was getting crazy knock (up to the max of 26) anytime i started to go into boost. I ran my tank pretty much dry and put in 4 gallons of 100 octane and did a pull - knock was gone. Turned out i had some clogged injectors, which was causing a few cylinders to run lean despire overall AFRs being rich.

Yours truly does sound like phantom knock, especially because of the circumstanes under which it occurs and the fact that it does not occur when doing WOT pulls.
I don't know if the one performance shop in town sells race gas or not, but I could try. Another option I thought of is maybe the fuel pump resistor bypass is causing me to run rich by overloading the stock FPR and causing it.
 

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I don't know if the one performance shop in town sells race gas or not, but I could try. Another option I thought of is maybe the fuel pump resistor bypass is causing me to run rich by overloading the stock FPR and causing it.
It's pretty difficult to get knock from being too rich... you have to be REALLY rich. Resistor bypass alone shouldnt cause that. Lean condition is usually what leads to knock.
 

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The LCDBC is only reporting what it's being told by the ECU... If it's counting up knock sum, the ECU believes it's real knock. Doesn't mean it can't be false knock from another source that's fooling it, but the knock algorithm is pretty good at filtering that stuff out, so it's somewhat uncommon. If it is a false knock situation, under the specific conditions you described, my first suspect would be outer axle joints.
 

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Discussion Starter · #16 ·
So upon further driving I may have misattributed the knock to turning. It may be a symptom of getting to the "cross over" before entering boost under partial throttle and being around 2500rpms. This situation typically arises while turning or slowing down so that might be where the confusion is coming from. I have a serial to USB connector arriving tomorrow, so logs to follow soon.
 

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So upon further driving I may have misattributed the knock to turning. It may be a symptom of getting to the "cross over" before entering boost under partial throttle and being around 2500rpms. This situation typically arises while turning or slowing down so that might be where the confusion is coming from. I have a serial to USB connector arriving tomorrow, so logs to follow soon.
There is another thread on the cross over right now, but not knock related.

I suppose it could be possible that you encounter a lean situation at the crossover point and get knock as a result. The race gas test should confirm if your knock is fuel related, if that is accessible to you. Do you have a wideband?
 

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Lower load conditions mean leaner mixture and more timing... That's when you will often encounter knock. Under those conditions, it's not really all that worrisome in itself, but if you get the counts up there, it will pull timing and rob you of power, as well as often light a fire that doesn't go out as you increase load.

What injectors do you have? what fuel control?
 

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Discussion Starter · #19 ·
Lower load conditions mean leaner mixture and more timing... That's when you will often encounter knock. Under those conditions, it's not really all that worrisome in itself, but if you get the counts up there, it will pull timing and rob you of power, as well as often light a fire that doesn't go out as you increase load.

What injectors do you have? what fuel control?
Everything fuel related is stock I'm assuming, some old dude owned my car prior to me and it has like 20 years of service history at a single Mitsubishi dealership in Alabama, but I can pull them and check. All I've done to it since I've owned it are a K&N, new Y-pipe(gasket on old one was ripped), fixed various boost leaks, the fuel pump relay bypass, coilovers, and the LCDBC and boost controller. Something did just occur to me though, I originally did the fuel pump relay bypass after completing the free boost mod(prior to lcdbc) due to the car getting what I believed was massive fuel cut right around 2500-3000 rpms. It was so bad the car would actually buck around violently due to the misfiring, the fuel pump relay bypass fixed that but kinda made it so the car doesn't like being driven around that 2000-2500 rpm range. I also noticed on a fill up recently I am getting terrible gas mileage, around 13-14 mpg, and granted I'm a bit heavy footed but that is terrible.
 

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Discussion Starter · #20 ·
Alright, did some logging. For some reason the site says the files aren't of an allowed extension....so here is a google drive link. The column "new item" is boost as reported by the LCDBC in PSI. I apologize that some of the logs are quite large due to me having to drive around hoping to catch the knock. I've also included a 2nd and 3rd gear pull of me getting onto the interstate at wide open throttle(which the TPS shows as 95% for some reason).
 
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