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ECMlink E85 - Knocking under load.

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A Sharp

Proven Member
158
13
Nov 18, 2013
Platteville, Wisconsin
This is for my 2g rebuild.

1). Any boost, vac, or exhaust leaks?

BLT'd up to 20 PSI a few weeks ago.

2). Verified mechanical timing?
Adjustable cam gears. Probably could be dialed in a bit more, but they're in the neighborhood of correct.

3). Verified base timing?
No. (2g cas/crank sensor)

4). Ignition system
COP or Stock Coil: Stock
Wire brand and Age: New (forget brand)
Spark Plug brand, type and Gap: NGK BPR7ES -- gapped to .028, and then tried again with .022"

5). Motor health (Compression Test)
Cylinder 1: 150
Cylinder 2: 150
Cylinder 3: 150
Cylinder 4: 150

6). Performed basic throttle body adjustments?
Idle Switch: Simulated through link
Throttle Cable: yes
TPS: yes
BISS: yes

7). Compression ratio
About 8.5:1 (stock).

8). Any known bad sensors or brittle wiring?
I wouldn't rule this out.

9). Any DTC/CEL codes?
Emissions stuff. Nothing important.

11). Base fuel pressure and injector values
Base Fuel Pressure: 43 PSI
Injector Size (cc/min): 1000cc PTEs

12). Properly calibrated and configured wideband sensor
Sensor Brand: LC1. Just bought a brand new Bosch sensor.
Calibration Date: Today.

13). Type of fuel
Type: e85
Percent of Ethanol: Haven't tested it yet, but my fuel trims indicate that it is probably close to 85%.


I keep getting small amounts of knock (1-4 counts) under load. It happens at partial throttle and WOT, usually past 5000 RPM. I'm only running a 16g at 15 PSI, for the moment. The tune is conservative for now (stock 2g timing table and 11.5-11.0 AFRs, gas scale).

Do you guys think this knock is real? In the log I attached, I got 2 counts of knock in a second gear pull. The pull starts 190 seconds into the log.

Thanks.
 

Attachments

  • log.2017.04.16-02.elg
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  • e85_part_throttle_knock.elg
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Timing is supposed to be around 16*. I thought I was pretty careful not to go crazy tightening the knock sensor. Knock sensor is new btw.
 
Is this on a stock 2g MAF as your log suggests? You make no mention of a MAF at all in the DSM profile I suggested you create...
 
Update: dried some different AFRs, but it didn't really seem to help.
  • Pass 1 - 11.8 AFR with 2* timing pulled past 4.5k RPM. Still saw a raw knock of 1 at the very end of the pull.
  • Pass 2 - It seemed like Pass 1 was an improvement, so I leaned it out to 12.0. Check engine light came on at partial throttle (4 counts of knock), so I got out of it. It seemed pretty knock happy here, so I didn't go any leaner.
  • Pass 3 - Said f*** it and gave it an AFR of 10.6. Still had the sliders set to pull 2* of timing. Did WOT to 7k RPM, saw 0 knock.
  • Pass 4 - Same settings as Pass 3, but saw a knock count of 1 in the middle of the pull.
From what I could tell, leaning it out didn't help and enriching it didn't make it worse. Also, the engine seems to run smoother with a rich AFR. Could just be my imagination though.

Edit: I previously stated that I did some pulls with only 1* of timing taken out. This is wrong because I never pushed save :p. All these pulls had 2* taken out.
 
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EDITED:
Just going to stop trying to help. I feel I do not have enough experience in this area to be of any real help.

If you want VERY PROFESSIONAL help google shadowerks and talk to Steve, I'd also recommend Enthalpy.
They're HUGE Nissan tuners, but they mess with other stuff, especially Steve.
But anyways, they're about the best in the biz and (I'm not going to say cheap) 'valuable' when it comes to advice per dollar spent....
 
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Thanks for the advice, but I'm only going to seek professional help if there's no other option.

Still have a few things to play with... I'm going to try torquing the knock sensor again. I'll go barely past hand snug and just hold it with loctite.
 
I made some adjustments and tried again. I re-torqued the knock sensor. In the process of doing so, I found an empty brake fluid bottle sitting under the IM right by the knock sensor... I guess it got lost in there when I was putting the car back together :|.

Then I made some adjustments to my cam gears. Previously, I had advanced my exhaust cam and retarded my intake cam to decrease overlap and help vacuum at idle. I undid this, returning the cams to the mfg's recommended positions.

Finally, I set AFRs to ramp down from 11.8 to 11.5.

These adjustments seem to have helped. I'm no longer getting any knock in the middle of pulls. Sometimes, I'll see a single count right at the end of the pull when I let off, but I doubt that is real. I still need to add timing back in, so we'll see what it does then.
 

Attachments

  • Clean_pull.elg
    11.3 KB · Views: 68
I wish I had a dollar for every time I've had to tell someone "adjust your TPS sensor": http://www.dsmtuners.com/threads/adjust-your-tps.509898/

Your log looks decent overall. I'd say that's real knock you're seeing.

You can start by swapping to a non-projected (BR7ES) tip plug and see if that helps with the knock.

Like the others have mentioned, your DA fuel table is set too rich. You can download the generic one I gave another guy here: http://www.dsmtuners.com/attachments/96dsmftwdirectaccess-2017-04-16-01-eda.331308/

Lastly, test the ethanol content of your E85: http://www.dsmtuners.com/threads/sh...-where-to-go-from-here.504633/#post-153597043
 
I still need to physically adjust my tps and check ethanol content.

In the mean time, I got some BR7ES plugs and leaned it out. I took that fuel map template and made some minor adjustments to it, so that AFRs will ramp down from 12.3 to 12.1. Did a few pulls and got 1-2 counts of knock in the middle of the pull, just like before. Timing was around 15.5* after 6000 RPM (1.75 load factor).

As you suggested, this seems to be real knock. The projected plugs that I just took out had some noticeable peppering on the insulators.

I then pulled the BR7ES plugs and took some pics for you guys.
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Here's one of the projected plugs with a bit of peppering on it:
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I wish I had a dollar for every time I've had to tell someone "adjust your TPS sensor": http://www.dsmtuners.com/threads/adjust-your-tps.509898/
Done. TPS is reading 0.63V at 0% throttle, with no offset.

You can start by swapping to a non-projected (BR7ES) tip plug and see if that helps with the knock.
Tried the BR7ES and they didn't really help, unfortunately. I'm now using BPR8ES plugs, which also made no difference.

The fuel is dead on 85%, according to my test tube.

I ended up getting rid of the knock by pulling some timing out up top. It's running 14* at peak power and 15* at peak rpm. I'm just frustrated because this seems kinda low. I hear of people running over 20* of timing, with the same CR :confused:. But I suppose there are other ways to make power... aka more boost.
 
I've put at least four tanks of e85 in since making the switch. Also, I drained the tank down to almost nothing when I put E85 in for the first time.

I suppose taking a sample from the tank wouldn't be a bad idea though.

Thanks to everyone for the input so far!
 
The car has sat for some time, but I gave it some attention this weekend
-I did another boost leak test and found a lot of leaks that cropped up since my last test.
-Recal'd the wideband.
-added a second rad fan, even though it melted already :f-u:... Still got some decent pulls in while it was working - temps around 200*.
-fixed a large exhaust leak at the O2/downpipe junction.

Overall, it seems to be running better. It is much more consistent and I'm seeing knock less often. One thing that is really troubling me is my global fuel setting. To get the AFR to match the wideband, I have the global set to -11%. This is with PTE 1000cc injectors (I double checked the part numbers just to make absolutely sure). Global fuel should be around -30% for these injectors... so what gives? Just fyi, Maf comp is zero'd and fuel trims are within +/- 2%.

I took all the injectors out and hooked them up to a can of carb cleaner, just to see the spray pattern etc. They seemed ok, although this test was hardly scientific. Do you guys think they are dirty, or am I missing something?
 
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