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11-01-2005, 01:29 PM | #1 |
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Persistant 1-count knock, need advice w/logs
Setup:
WRX heads/Sti block, 8:78:1 CR, VF39, TBE, UTEC/Tuna, modified stock injectors@55psi base. For some reason unknown to me, I consistantly get 1 count of knock around 6100-6300rpms. The AFR is only 10.5-10.8:1 (it happened as rich as 10.2:1) and timing is retarded to 15 deg. I can run 18 degress fine, but when pulling it as low as 15 it still does this. It does it with boost lowered to 13psi too. I'm begining to wonder if it's false knock, but then it got 2 counts once (shown below). To sum things up: 13 deg @10.8:1 (opposed to normal 19-20 that it can take below 6100) Code:
6277 +15.1 4.4 100 80 00 W/B +37.7 56.6 +13.0 -3.4 350.00 3.4 10.78 6349 +14.5 4.4 100 80 01 W/B +38.7 55.5 +5.5 -3.3 350.00 3.4 10.80 Code:
6150 +13.3 4.3 100 80 00 W/B +27.7 56.1 +15.0 -1.5 350.00 3.3 10.29 6195 +13.5 4.4 100 80 01 W/B +34.8 55.8 +10.5 -1.5 350.00 3.4 10.30 Code:
6349 +12.1 4.3 100 60 00 W/B +38.1 55.9 +17.0 -0.3 350.00 3.4 9.99 6397 +12.1 4.3 100 70 01 W/B +38.5 55.8 +12.5 -0.3 350.00 3.4 9.99 And I've tried values of timing, boost, and AFR in between (even knocks at 12psi, 10.5:1, and 15 deg). So, next is det cans. If they say it is real knock I'll really have no clue. I mean, AFR, timing, boost, and octane are the only things that can cause det (and my plugs are NJK 7's as I said). I might put some 100 octane in tomorrow just to rule this out. If it knocks on 100 octane, it can't be detonation. Can't be. If I go past 6100 (set knock cor to 2) I'm peppered with 1 counts untiil redline (about every other load point). Pardon my crudeness but, W_T_F?
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Last edited by TypeC; 11-08-2005 at 09:28 AM. |
11-01-2005, 02:01 PM | #2 |
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The dropping RPMs is clutch slip or possible wheelspin. It is climbing an average of 100-150 rpm per data point, then jumps up to 6410, then it starts catching again. The RPM logged by the UTEC does tend to jump around a bit anyway, like the first two data points it goes down by 30 RPM. I'll account that to the way UTEC logs the RPM (i.e. not very accurately).
I've seen several people post logs of clutch slip and getting knock at the same time. It could be coincidence, or it may be the load is actually much higher and contributes to knock? If RPM is falling with TPS 100%, that means the load torque is greater than the crank output torque, thus the load 'wins' and RPM falls. I wish I could be more helpful, but I can say that higher CR is going to have an adverse effect on the amount of ignition advance you can run. +15 @ 6000+ is very conservative compared to a non-hybrid EJ207 or EJ257, but your CR is also 0.5 to 0.7 higher than either of those engines. Hopefully a fellow hybrid WRX head/2.5 block user can help out more specifically. As for false knock, I think I'm going to start a new thread on knock headsets... I'm very interested in one for myself. Good luck. |
11-01-2005, 02:20 PM | #3 |
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Its not clutch slip, the UTEC does not always show the RPMs moving up. Not any more complicated than that. Also you are knocking in those lines so its possible with the pulled timing that the RPMs did actually decrease.
As for the knock...how are your plugs? |
11-01-2005, 02:25 PM | #4 | |
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Quote:
The plugs are NGK 7's with a .275 gap with about 2K miles on them. I mean, I don't see how it can knock with so little timing (intentionally retarded) and conservative AFR. |
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11-02-2005, 11:44 AM | #5 |
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Here is a log with the timing retard all the way to 13 degrees. Notice I still get one count.
Code:
5282 +15.3 4.3 99 80 00 W/B +29.5 50.9 +13.0 -3.5 325.00 3.3 10.73 5341 +16.1 4.3 100 90 00 W/B +30.6 53.4 +13.0 -3.5 350.00 3.3 10.74 5428 +15.9 4.3 100 90 00 W/B +30.9 53.8 +13.0 -3.5 350.00 3.3 10.81 5546 +16.1 4.3 100 90 00 W/B +31.5 52.6 +13.0 -3.5 350.00 3.3 10.83 5727 +16.1 4.3 100 80 00 W/B +31.9 53.2 +13.0 -3.5 350.00 3.4 10.89 5777 +15.1 4.3 100 80 00 W/B +32.3 53.7 +13.0 -3.5 350.00 3.3 10.93 5737 +14.7 4.4 100 80 00 W/B +33.0 53.8 +13.0 -3.5 350.00 3.3 10.89 5931 +14.9 4.4 100 80 00 W/B +34.2 55.1 +13.0 -3.5 350.00 3.3 10.83 6049 +15.1 4.4 100 90 00 W/B +34.8 52.5 +13.0 -3.5 350.00 3.3 10.83 6071 +16.1 4.4 100 90 00 W/B +34.5 55.2 +13.0 -3.5 350.00 3.3 10.89 6127 +15.7 4.4 100 80 00 W/B +32.7 55.6 +13.0 -3.5 350.00 3.4 10.86 6242 +15.1 4.4 100 70 00 W/B +37.9 56.2 +13.0 -3.5 350.00 3.4 10.78 6277 +15.1 4.4 100 80 00 W/B +37.7 56.6 +13.0 -3.4 350.00 3.4 10.78 6349 +14.5 4.4 100 80 01 W/B +38.7 55.5 +5.5 -3.3 350.00 3.4 10.80 6349 +14.5 4.4 100 80 01 W/B +38.7 55.5 +5.5 -3.3 350.00 3.4 10.80 |
11-02-2005, 11:50 AM | #6 |
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typec- for what its worth, ive retarded my timing much the same like you...
...i see other people with similar mods running much more ignition advance, yet i still see the same 1 count knock values anywhere from 17 to 22* at redline. are you running the stock knock sensor? i am running the TUNA knock sensor, and have wondered if i tightened the knock sensor down too much...i have just been too lazy to go check with a torque wrench...but i believe the proper setting is 17lb/ft. i dont even think i used a torque wrench the first time. ...something to look into? |
11-02-2005, 05:51 PM | #7 |
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[dork] dont be so retarded. ahaha, retarded, get it. [/dork]
set your knock correction threshold parameter to 2. save you some headache. plus you have it pulling 8 degrees on a 1 count? wow! |
11-02-2005, 05:56 PM | #8 | |
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Quote:
Also, with the exception of that last log, it is pulling around 4.5 degrees. I didn't change it from the default StageIV params. Any more input is appreciated. I'm really getting sick of shifting at 6K. Last edited by TypeC; 11-03-2005 at 12:23 PM. |
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11-02-2005, 06:08 PM | #9 |
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TypeC I'm having the SAME exact promlem you are have I also have a 2.5l with wrx heads. I've tried the timing as low as 5 and as high as ~20ish and it still knocks in the same exact spot. So I woul take the last posters advice and justset the threshold to 2 instead of 1 I hadn't even thought of that i'll give that a try after the car gets put back together this weekend.
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11-02-2005, 09:24 PM | #10 |
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Sounds like you may need some detcans to figure out if it really is knock or not and if it'll be safe to increase the knock correction threshold parameter.
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11-02-2005, 10:21 PM | #11 |
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right, plus you can also change the knock sensor sensitivity just above 6000 if you want.
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11-02-2005, 11:31 PM | #12 | |
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11-02-2005, 11:54 PM | #13 | |
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Quote:
To sum things up, I went out tonight determined to find the cause: 13 deg @10.8:1 (opposed to normal 19-20 that it can take below 6100) Code:
6277 +15.1 4.4 100 80 00 W/B +37.7 56.6 +13.0 -3.4 350.00 3.4 10.78 6349 +14.5 4.4 100 80 01 W/B +38.7 55.5 +5.5 -3.3 350.00 3.4 10.80 Code:
6150 +13.3 4.3 100 80 00 W/B +27.7 56.1 +15.0 -1.5 350.00 3.3 10.29 6195 +13.5 4.4 100 80 01 W/B +34.8 55.8 +10.5 -1.5 350.00 3.4 10.30 Code:
6349 +12.1 4.3 100 60 00 W/B +38.1 55.9 +17.0 -0.3 350.00 3.4 9.99 6397 +12.1 4.3 100 70 01 W/B +38.5 55.8 +12.5 -0.3 350.00 3.4 9.99 And I've tried values of timing, boost, and AFR in between (even knocks at 12psi, 10.5:1, and 15 deg). So, next is det cans. If they say it is real knock I'll really have no clue. I mean, AFR, timing, boost, and octane are the only things that can cause det (and my plugs are NJK 7's as I said). I might put some 100 octane in tomorrow just to rule this out. If it knocks on 100 octane, it can't be detonation. Can't be. If I go past 6100 (set knock cor to 2) I'm peppered with 1 counts untiil redline (about every other load point). Pardon my crudeness but, W_T_F? Last edited by TypeC; 11-03-2005 at 12:57 AM. |
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11-03-2005, 11:17 AM | #14 | |
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11-03-2005, 11:21 AM | #15 |
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Possible you also have a coil that can't keep up or a plug. I'd replace the plugs first since its cheap & easy. While you have the coilpacks off measure them for resistence to see if they are also still good.
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11-03-2005, 12:02 PM | #16 |
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FWIW, you're not the only person in this hell. I have been battling the definition of my Knock Threshold curve with my Hydra Nemesis for months.
Several 100 octane tank fulls + VERY conservative boost and timing. Datalogging for hours upon hours to generate a clear picture of my abnormally loud engine (ver8 EJ207 + WRX heads) and define a tight-but-not-too-tight Knock Threshold map. Several correspondences with Phil @ Element Tuning. On and on. And at this point, I am pulling my NGK 7 iridiums and trying NGK 7 coppers. Tuning with care is TEDIOUS. Hang in there. |
11-03-2005, 12:10 PM | #17 |
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I'd agree with all the above.
Hope this isn't considered hijacking, but I'd really like to get a knock headset myself. Does anyone have product recommendations? I'd almost like to actually record straight to my laptop as well, which should be as easy as plugging a cable from the headset output to my laptop and opening sound recorder. Not like I'm going to run around with a headset all the time. |
11-03-2005, 12:19 PM | #18 | |
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Quote:
If you search for "detcans" you'll see a couple threads containing links to a DIY detcan. Jon[inCT] posted the links (I know because I found them last night). edit: http://forums.nasioc.com/forums/show...4&page=1&pp=50 Back on topic. Last edited by TypeC; 11-04-2005 at 12:19 AM. |
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11-07-2005, 02:26 PM | #19 |
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sort of an aside: All the math I've seen about your engine combo puts the CR at about 8.6 to one, so a little lower than what you posted.
I'm still of the opinion that you ought to either raise your threshold to 2 or decrease your knock sensitivities a little in the higher rpm's. don't let my advice blow your motor or anything, but a 1 count is not really a significant knock event in my opinion (just engine noise, I think). one thing you could do for safety is have your injectors tested to make sure they flow equal, and you don't have one real lean cylinder that is being masked by the other 3. There's a place here in Houston that does it on Damico street or something you could "search" for it here, I remember seeing at least one post about it. I have a spare set I am sending out, if you want you can borrow them to reduce your downtime after I replace mine. |
11-07-2005, 03:04 PM | #20 | |
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Quote:
I plan to install detcans (record KS) and see if it's realy knock or not. Even though it's only 1 count, if It's real knock I don't want to just let it go. |
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11-07-2005, 06:00 PM | #21 |
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didn't you mention that you had a TUNA? that comes with a quite sensitive knock sensor, and you can plug headphones in and listen to the engine sounds. It's remarkably like det cans...
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11-08-2005, 09:28 AM | #22 | |
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11-14-2005, 05:34 AM | #23 |
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type c... Sorry.. I have been at SEMA and then Fishing/Hunting with my Dad..
Lets look at some facts. The reason you need to run a rich AFR is for detonation resistance. The extra fuel past about 12 to 1 is used for in cyl cooling. Cyl pressures are highest during the trq peak and just after the trq peak. I have posted links in the past to Airplane engine tuning guides that have graphs. Look them up. When on the dyno I tune using the Trq readout much more then the HP chart. There is a reason for that. When tuning use some sort of tool that will show you that you are making an improvement. Delta dash Dyno, Nology PDA dyno, Blitz monitor or even a hill that you can climb starting at the same point and same mph. You have a large motor with pretty high compression and a pretty large Combustion chamber of 52cc's or so. You have small ports and a small turbine section. All this adds up to a very knock happy motor. The trq peaks early and falls Very hard. I have tuned probably 50 or more setups like yours. I would bet you loose 100 or more ft lbs from trq peak to redline. During high Cyl pressures your motor is more likely to det and this is where the enrichment comes in. Past that you do not need the heavy enrichment. Running AFR's like you are doing now only raises Pressure but past the point of where it is actualy producing power. What I bet is going on is rich misfire. At 6000 rpm I suspect your preturbine pressure is 3-4 times your manifold pressure. What this means is that you have a Charge of Exhaust that could not get out, ALOT of fuel and a lesser amount of air... Added up this means misfire. Back the Fuel off past 5500.. At 7k run 11 to 1 or even 11.5 to 1. Dont force the turbo to do something it cant. You are better off with lower boost up top and more timing then vice versa. If you knock when you lean out pull timing or boost. For every 1 psi you remove add 2 degrees back. Hope this helps. Clark |
11-14-2005, 11:32 AM | #24 |
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What are your knock sensitivity settings? Since your block is not stock you may need a minor adjustment.
Have you ever pulled a dd log? I found that any form of knock would show up on knock correction before a hard knock occurred. The log you showed did not have the ecu pulling timing. This may not compare well but I think Clark is correct. dd logs showed I would get less knock correction (which is bad) with a more conservative tune (less boost, timing, etc.) meaning you can run too little timing and too rich a mixture and cause problems. I am also getting knock counts of 01 at a similar rpm but I have cp pistons (does not occur when I use the stock map which is weird unless the stock map turns off the cel for knock). I haven't had much chance to log since I just installed my utec but I suspect it is my pistons rather than knock. If your pistons have a bit more clearance than stock, then it should be louder. Greg |
11-14-2005, 02:30 PM | #25 |
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with drop in Forged pistons its common for me to take 10 points off the knock sensitivity settings in the Utec. However... You need to make sure you tune is correct and you are not knocking before you alter those settings.
Clark |
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