Georgia Fiero Club Forum
All Things Fiero => Tech Tips, Tech Questions => Topic started by: f85gtron on April 23, 2015, 09:20:00 pm
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Other than detonation, what would cause high knock counts?
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You're running a knock sensor? Where is it installed? Hope it isn't picking up a rod or wrist pin knocking, if that's even possible.
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Anything that makes a vibration can be interpreted as a "knock".
Some of the 3800 swaps were actually picking up internal transaxle noise as knock. (i remember reading that, years ago.)
Not to say that that's what yours is hearing.
It's probably not gonna be a lot of fun to find.
Did your 7730 come from a V8 car or a V6 car? I've got a 7730 that came from a V6 car. If yours came from a V8 car, I'll trade memcals with you, if you're interested. (The knock module is part of the memcal, as I understand it.) This is assuming your PROM is removable. My 7730 is going on a 4.9. Someday.
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Mine came from a 3.1 Corsica. Sorry. Otherwise, I would trade. It happens only at part throttle. Not during lugging, not at wot, not at idle. I think it's some kind of vibration? I hope it's not wrist pins!
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I forgot to answer where it's installed.
I installed it trunk-side (rear) at the water jacket plug location. There's a 3/8ths? plug there.
I have no exhaust leaks, I think my timing is right (I'll have to double-check), but I need to check for metal clanging.
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The knock module sits over the memcal in mind if a piggyback fashion. The knock module is a weird, cyborg-looking piece of electrickery. I think it's held in by six pins.
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If I remember my old school (read that as shade tree) technology, if you have an engine knock at cruise or deceleration, it's a rod. If you have a knock at acceleration, it's a wrist pin.
Isn't the fan switch removed or disconnected, leaving that space available for a knock sensor? I believe I read that because the 7730 actually controls the fan that some placed the knock sensor in the fan switch location. I know this would require changing your harness, but it may not be as sensitive to extraneous noises. Am I correct, Steve?
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I'm not a good person to ask about engine knocks.
My first swap was a 2.8 that had a knock, that I believed to be a rod.
The person I sold it to (actually, I sold the engine stand and "threw in" the engine) told me that it had been the timing chain making the noise. Although the engine was still worn out.
As for knock sensors... I have seen them placed in lots of different locations. The water jacket drain plug is one place. My 4.3 had one on the rear of the block, just behind the left head. My 5.3 LS engine (in my truck) has two of them - one in each end of the valley cover, under the intake.
Hadn't thought about the sensor hole, but it sounds like as good a place as any, to try.
In terms of all of our "retrofits", it seems like a guessing game, anyway.
One of the guys on Pennocks sent me a datasheet that described which knock sensors responded to which frequencies. I forget whether it mentioned applications or not. I might still have it if anyone might find it useful. To me, it was kind of "information overload".
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If I've got a rod making noise, then it's probably a good idea to change bearing before they spin. Maybe this is a good thing.
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Can you hear anything suspicious?
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No Suspicious noises. The timing chain thing makes sense, though. My timing marks jump around at idle, but are clear while revving up and down. Its been bothering me for a while.....but it's not loud. I'm sure it's stretched.
No pinging that i can hear. I lugged it in fourth up a hill and can't get it to run up anything but one or two knocks. Definitely some other harmonic or noise.
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Another suspect you may consider is the harmonic balancer. If the rubber ring has gone bad it will allow the timing marks to jump around so the timing never gets set correctly and you are getting an occasional spark knock.
Remove the drive belts and try to move the HB pulley. If there is ANY movement by hand, it's bad. There would only be movement when a great amount of torque was applied, such as when you stomp on it or at high RPM's, to keep the crank in balance.
If it sounds like a gremlin banging on the inside of the engine with a hammer,then its likely a rod. Send us a .wav or .mp3 file of it so we can better analyze.
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It happens only at part throttle.
I missed this.
"Part throttle", as in "steady state, highway cruising"?
That's when the EGR functions, or is supposed to function. A "dead" EGR (that the system thinks is functioning) can easily cause the engine to ping. A malfunctioning EGR can cause high NOx emissions without an audible ping, but maybe enough for the sensor to "hear"?
Just for grins, run the tank down as far as your comfortable and fill it up with premium. Or dump some alcohol or (I've heard) naptha into the tank. If any change in the fuel fixes your "knock" issue, it's probably "real". Or maybe just a tuning or EGR issue.
Of course, if your EGR is disabled in the tune, the fuel and spark tables should also be set up to accommodate it. If your datalogging is working, you might try to determine the exact parameters when it happens. what RPM, throttle opening, MAP reading, and etc. Send it to Ryan and he can probably tweak it.
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I brought it up to him and I offered to do a log. I sent out to him and he didn't say anything other than the knock counts are excessive.
I'll run more logs and pin down the exact condition it happens.
A bit of info I picked up from the ricer forums that may help:
Don't worry too much about knock counts.....worry about knock retard, which is when the ecm actually reacts to these events.
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Don't worry too much about knock counts.....worry about knock retard, which is when the ecm actually reacts to these events.
...and I misunderstood.
It's not actually retarding the spark? Just seeing random knock events?
That's a whole 'nother thing. And a lot less worrisome, to my mind, anyway.
Keep in mind that I've never done a tune for knock, or knock retard.
Most of my ignition tuning is done by ear. I crank it forward until it pings, and then back it off until it doesn't. Of course, that might be a bit difficult with DIS. :D
On that topic, I think the timing ring on my damper must have slipped, because the car is pretty gutless with it set to spec, using a timing light.
After doing that, I set it by ear, as above. When I checked it with a timing light, I had added a whole ten degrees to the "spec". Something doesn't smell right. But it runs good, now.
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Thanks for the help..
I've gone back and watched my log in real time because I was starting to worry myself to death! By Re watching, I've learned that my ecm has been reacting to each event by retarding the timing. On a 20minute drive home, that was 250 Events! Also, it doesn't happen during cruising, as previously thought, happens during acceleration, so I've got to have my timing wrong!
I'll check timing tomorrow and report back.
Leaning more everyday!
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Are you still using a distributor? I was thinking DIS, but that's not necessarily true, I suppose.
Don't know how much "help" I've been. Mostly rambling... ::)
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Tons of help. I'm trying to make sense of this and diagnose at the same time, so any thoughts and input are better than what I'm coming up with without experience to pull from.
Its a dizzy setup. In this case, I'm glad for it. Apparently, without chip burning experience (of which I have none), it's a hell of a lot easier to turn a distributor than change a spark advance table. ...maybe someday.....
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I forgot to mention that the egr is not functional and is blocked off completely at the upper plenum.
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Okay. The EGR being disabled removes some variables from the picture.
Before you do anything, I'd try filling up with premium fuel and see what happens. Unless Ryan has some other ideas.
If that works, you have three options, as I see it.
Keep running premium.
Back off the timing until it doesn't do it any more.
Ask Ryan to alter the tune. Maybe removing some advance from certain areas.
I'll add that when I had my 3.4 installed, it pinged at part throttle. (This is a common complaint, it would seem. At least on Pennocks.)
Crap gas made it worse. Premium gas made it better. Even radical amounts of change to the tuning didn't help much. (I was not doing the chips. Someone else was.)
The only time that it went away completely was after I took the engine apart and built it back up with ported heads and a big cam. (I suspect the cam made all the difference, since it was designed for higher compression than I was running.)
Before the "build" I could only run 8 degrees before it would ping. Afterwards, I was able to run nearly 12 degrees.
Sorry. More rambling...
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Thanks. I went out and backed off the timing. I had it at 12. It was fine with the old ecm. I guess this one's more aggressive. Anyways, i managed to strip out what was left of a stud where the thermostat housing mates up to the intake manifold. I previously jb welded a stud in because i snapped off the original built in it, then drilled for an easy out with a left handed drill bit and it still didn't back out. The easy out broke off and i couldn't drill it out and ate up all the aluminum around it, so that's where the stud (upside down bolt) set into jb weld came into play.....which held nicely until last week.
I'm on the hunt for either a 3800sc or an intake manifold.....whichever i find first!
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Raydar,
I found the data sheet I think you where referring too. How do you read it? Lots of numbers!
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Update:
Retarded the timing to 8 degrees and started using premium, still getting high knock counts and seems to have stayed the same. My exhaust is ported and I'm running 1.6 rockers, so I wonder if it's picking up resonance? I'll change the sensors location to the lower intake manifold and see what happens.......
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PROBLEM SOLVED!
The 2.8 is an EXTREMELY noisy motor. Of course, I don't need to tell any of you that. Anyway......
The solution to the problem was in the sensor mounting. As suggested previously, I installed a 90° 1/4" npt elbow and then installed the knock sensor to it. All the knocks went away. Just startup and shut down knocks....like it should be.
Idk what it picked up before, but it would hit religiously at 2k rpm and would tally 70+ an event. Driving 20min to or from work would yield 200+ knocks that would result in retard being applied. It's a totally different car to drive now!
Ron
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Where did you install the knock sensor and who recommended the 90 degree fitting? Was it down on the side of the block?
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The knock sensor is installed in the trunk side water jacket, where the vss wires run from the alternator. The 90° elbow suggestion came from ricer forums and Pennocks. I mistakenly remembered they originated from here (the best advice I've gotten thus far is on this forum ;) ). Without a reducer fitting, I was unable to install the sensor on the lim. All I had on hand was a stainless 90° 1/4" npt elbow. I purchased a 3/8" elbow and you should have seen me cussing while I was forced to understand, with coolant running up my arm and showering my head, that it was the wrong size! Bet the neighbors got a kick out of the spectacle.
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Why do you need the knock sensor?
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For tuning purposes and if you’re running the spark to the limit for more torques, you need some kind of protection. It’s saved my booty in other ways too, bad gas has set it off. There’s other things that you can use the sensor for, but that requires a turbo-Choo-choo rig.
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Adding the knock sensor gave you more torque?
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Adding the knock sensor gave you more torque?
With the knock sensor, the engine computer will learn how hard it can "push" the engine (by adjusting the timing) before knocking starts. Without one, it holds back a safe amount, and so the engine produces less power.
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I wonder how much power.
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Where do you get the bad gas?
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From the ma and pa gas station just across the river into South Carolina on Gordon hwy.
You can tune your spark tables, just like tuning the fuel maps (tables). However, unlike going too far with fueling, whereupon the consequences are cooler heads and fouled plugs along with wasting fuel, going overboard on the spark tables in the higher load areas will result in a hole blown through a piston, overheating, and an even bigger hole blown through your wallet! The insulation against those kind of activities is to utilize a knock sensor, that will dial back the amount of timing when knock is detected and save your wallet, er, I mean motor.