I discussed this with DS in the past, after seeing the different knock thresholds between the cylinders, the only logical explanation that I could come up with, is because its due to the proximity of the sensor in relation to the cylinders.
It should take less voltage from 1 and 4 to trigger "KR" than 2 and 3, because they are further away from the sensor. Considering that the knock sensor is pretty much smack in the middle, it makes perfect sense.
Sure that could be the reason.
I rememmeber DCR got the idea for their twin stock turbo by stating that they saw much higher pressure around cyl #1 and wanted to eliminate it. So I was think that cyl #1 must have higher rates of reversion and chamber temps then the other cylinder and THATS why it had a lower Knock threshold. The problem I had with this is that it didn't really explain the lower threshold on #4.
your reasoning sounds more simple and more likely.
Although a few inches may not sound like much, waves(sound, light, electromagnetic doesn't matter) lose intensity proportional to the square(d^2) of the distance. So you'd assume that the farther away a cylinder was from the sensor, the lower or more sensitive to knock it should be. Simply becuase the knock is losing intensity as it travels the longer distance to the sensor.
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Last edited by duster360 : 08-20-2009 at 07:53 AM.
1) Its real hard to trust the knock sensor once the pistons are changed
2) no "Real" tuner tunes off the knock sensor. Get it on the dyno, find the new MBT with high octane fuel and work backwards with pump gas using auxiliary knock detection equipment
Very true... This is where that old "plug reading" stuff comes into play... Like anybody knows how to do that stuff anymore...
I love reading stuff like this from people that know!
It used to be the only way to know what was going on.
I remember doing this after each pass at the strip on my old 86 Daytona.
25psi on cast pistons, with old school 8v head. 12.9@112mph...
not too shabby.
but your right, who knows how to read plugs anymore!
I do.. I do..!!! lol
Here is a link for informative reasons. Obviously, these are examples.. and there are many different steps in each condition,.. but example A (top pic) lol is pretty much what your after... without the ashy looking deposits.
Every time I check my plugs, the look pretty much new, with a brown tinge to them.
Stage 1 ECM (NOT stock), Diablosport Predator, 3 bar map and tip, Interceptor Scangauge, AEM wideband, 750's (no return-line), MPX BFMIC, Walbro 255, DCR top end modifier, AGP WGA, 3 in O2 housing, QTP 3in downpipe with E-cutout stock catback, Nitrous Oxide Systems 65 HP shot, motor mount inserts.
Best MPH to date on the bottle,119.04 --- Off the bottle 113.55. --- best ET 12.44. on borrowed DR's. Stock turbo, stock Mani.
Last edited by Nosfurato : 08-22-2009 at 03:49 AM.
Mine look exactly like that first pic so I guess i'm alright
I saw some trans am the other day with 2 huge black, practically painted spots around the tips of his muffler...poor car was probably drowning in AFRs
Well, in an ideal condition.. you want to check your plugs right after a wide open pass. That will give you a pretty good idea of how things are running.
I kinda cringe a bit at doing that in a turbo car,.. simply because of the heat related issues, and shaft speeds of the turbo itself.
Kill the engine, you kill the oil flow, and coolant flow (if water cooled) If the car had an electric water pump, (water cooled) I wouldn't hate the idea so much.. without it?.. personally.. I don't care much for that idea.
I suppose it wouldn't be a huge deal if you run good oil,.. and let the turbo spin down for a min or so before clicking it off.
Come to think of it, I just thought of a potential solution to my little "worry"..
Disconnect the harness from the coil, as soon as you can.. have someone in the car that can turn the key. While they turn the key.. make sure they have the gas pushed to the floor. The car will NOT start, because during cranking conditions if the car is at WOT.. the injectors are turned off!
This will help keep coolant, and oil circulating. Granted, you don't want it cranking the entire time.. but, a few seconds or so each time should help things out.. (and not drain the batt too much)..
Also, it shouldn't change your plug readings at all,.. even if they are still in the motor.
Well, in an ideal condition.. you want to check your plugs right after a wide open pass. That will give you a pretty good idea of how things are running.
I kinda cringe a bit at doing that in a turbo car,.. simply because of the heat related issues, and shaft speeds of the turbo itself.
Kill the engine, you kill the oil flow, and coolant flow (if water cooled) -Will.
Yes you want to shut down the engine ASAP but,,,,,,,,,,,,leave it in gear and coast to a stop. oil still pumps and water still pumps.
by the time you slow down, everything is much cooler.
With a built bottom/top end knock characteristics may be thrown off due to the frequencies/harmonics changes.
After knock detection is done with an external device operating outside of the ODB readings the only real way to correct for proper timing control is to decrease knock sensitivity electonically via CMR tuning. In other words, until the sensitivity is corrected for, the PCM is still going to freak out and start messing with timing when it detects what it thinks is knock, so essentially you will not be running to full potential.
I see water/meth injection often recommended as a bandaid, but thats more to help equalize the varying gas you tend to see at the pump is it not? If the PCM is detecting false knock due to the changed harmonics vs stock pistons, I can't see meth correcting the issue?
How much will just going to a lower compression piston aid with this? Assuming you are still on a built head and the lower compression pistons will change the harmonics, how prone is the sensor to false knock detection?
On a number of other turbo cars I've seen aftermarket knock detection/timing control systems but haven't really seen anything used on the SRT4.
With a built bottom/top end knock characteristics may be thrown off due to the frequencies/harmonics changes.
After knock detection is done with an external device operating outside of the ODB readings the only real way to correct for proper timing control is to decrease knock sensitivity electonically via CMR tuning. In other words, until the sensitivity is corrected for, the PCM is still going to freak out and start messing with timing when it detects what it thinks is knock, so essentially you will not be running to full potential.
I see water/meth injection often recommended as a bandaid, but thats more to help equalize the varying gas you tend to see at the pump is it not? If the PCM is detecting false knock due to the changed harmonics vs stock pistons, I can't see meth correcting the issue?
How much will just going to a lower compression piston aid with this? Assuming you are still on a built head and the lower compression pistons will change the harmonics, how prone is the sensor to false knock detection?
On a number of other turbo cars I've seen aftermarket knock detection/timing control systems but haven't really seen anything used on the SRT4.
I don't see water/meth as a bandaid.I just got tired of paying for race gas for a tune i ran only at the track.Some think these cars pick up a lot of false knock from a lot of places...i'd also question the accuracy of the aftermarket knock detection.
i did a little testing the other day. PIDS are few due to the Tinity log issues, so don't bust my balls about it. There's a new Tinity crom to fix the logging issues so this will be the only substandard log from me.
I have 5KR but thats not such a big deal once you know my A/F was 13.0-13.6 on 92 OCTANE Thats why I shut it down at before 5K.
It was so lean because this was the first log after I got my 03 PCM scaled for my S1 injectors.
After adding 10%-15% fuel, the A/F settled down under 11.5-11.8. One of the two WOT got 1.5 KR, but big deal, its good enough for generic 92 octane: Deposit Files
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lol
oil still pumps and water still pumps.
Thats why I shut it down at before 5K.
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