What is an acceptable amount of knock? I'm in the none category on this and just want to hear others opinions.
What is an acceptable amount of knock? I'm in the none category on this and just want to hear others opinions.
under what conditions? at WOT? none. at part throttle? a couple random degrees of knock once in a while is ok, IMO. constant knocking is never ok.
I mean ever. I personally can't trust a knock sensor. So when it shows me knock I can assume two things. It's real or it's not. I am going with its real as that is the safe thing to do. Now whether your tune is reading it is adding timing or 0 or even retarding timing. If it senses knock the car will retard the timing. Regard less of where you tell the ecu where to start and where to try to get to the knock sensor will see knock when it's going to see knock. What positive knock means to me is the starting value was to high and you you were relying on the sensor to save the engine. I want my numbers as close to 0 or even a little - knock. I think some one heard 2-3* off knock is okay and started spreading this information. The truth really is 2-3* off timing adder is okay. Knock is never good. Again regardless with the numbers being close the sensor will give you the best total timing. If you are seeing positive knock you are relying on the accuracy that the sensor isn't missing any knock. I don't trust knock sensors.
I don't have much imput that y'all don't already know, but that other guy I swear must have went to the BAMA school of tuning, circa 2011, when they were popping motors. I can't take anyone's opinion seriously when they say it's ok to have 3 degrees of knock at damn near 7000 rpm at WOT. I mean why tune a car on the ragged edge with spark advance when you can make more power on conservative spark by playing with VCT?? The both increase cylinder pressure, but more spark advance puts you closer to detonation. Whereas VCT doesn't necessarily, and better VCT setting increase VE of the motor= better bang for the buck, so to speak.
I'll put it in reference to my own personal experience with a popped piston. I had a 2012 wrx that was tuned by one of the best known tuners out there. The car made great power for what was done to it. However, 1 tank of bad gas, and BOOM, I had a cracked ring land. Why? Because it was tuned on the ragged edge with good gas. Never again will I go through that ordeal. That's why I'm tuning this car myself.
Also murphie, you were 100% correct with what you said, it doesn't matter if you're tuned at the ragged edge getting positive knock or if you tuned conservatively where the knock sensors are adding timing, the car will make the same power.
I had to come to a tuning forum to check with experts. I saw this crap all over the Subaru forums and just accepted it and even tuned my Subaru like this. I was ignorant Back then I should have associated the frequency of engines popping and the tuning style. Note I'm seeing it in a new Ford community and it's just scary that no one has a good explanation for this. The best I got was YDBT. And that's considered a joke.
Yea I totally agree. The running joke in the local Subaru group was you weren't officially part of the group until you popped a piston, lol! Bottom line, I know my car isn't knocking, and if it ever does, I know I can fix it. So therefore I won't be replacing my shortblock anytime soon. I know that goes for y'all too. Now the other guy, good luck to him.
I'm starting to feel comfortable enough with tuning that I can tell the good tuners from the bad just by how they are handling support. If a customer says they have positive knock and they tell them that the tune is fine that scares me. That's why in the other thread I had to ask how did the car feel or even another dyno run after the tune. Just trying to see who I should recommend for tuning cause I sure don't feel like starting a business out of this just want to spread good information.
just to clarify for others who might read this thread, the "other guy" you reference is from another thread on a different forum. :-)Originally Posted by rhinogt
Oops, sorry Higgs, I should've just said that.
Murphie, I'm in the same boat, I have no plans of being a orofessional tuner. At most I might work with my close friends, but that's the absolute extreme of it. I went hptuners because I wasn't satisfied with the tuning options out there for the S550s. With the S197s, it's a different story, but for the s550s there just aren't a lot of good options out there. So I figured, why not do it myself. I'm glad I did.
Honestly, I normally don't post things on any forums, unless I have a question. Or I KNOW what I'm saying it true. I'm here to learn, because you never stop learning. We have two ears and one mouth. So we should listen twice as much as we talk.
Yup I don't just post things. I try to post with an explanation of why I think the way I think. I love it when people can correct me. It's when it's you are wrong and no explanation.
Yea for example when you and Higgs were bantering back and forth about cmcv's and playing with low load VCT, etc. I looked at what y'all were doing and went my own way which I'm happy I did, because my car feels better. But had y'all not brought it up I probably wouldn't have played with it.
Exactly why forums exist. I'm thankful that higgs is here to raise questions and post information. It all adds value. The point isn't to agree but to figure out why you don't agree.
Last edited by murfie; 01-24-2016 at 10:42 PM.
Exactly!
what did you do with it?
Yes good question. Why you holding out on us lol.
Well quite simply rather than changing cam timing in all the tables, I simply drastically reduced the fuel economy max load table values, as well as the best driveability load table values. Basically, it was all that was needed for me to minimize when the cams are in Atkinson down to very low loads by minimizing when those mapped points are used. When I'm applying throttle trying to accelerate, it goes into Otto now. I haven't gotten a chance to play with cmcv's yet to see if the help because I have been TDY for the last week or so, but all in all, if say so far so good.
I don't have the computer with me so I don't know the exact figures to show y'all, but it looks something like this:
Fuel economy:
.45 .35 .30 .15 .0 .0
Driveability:
.15 .15 .15 .15 .15 .15
Again, that's not exact, I'm just shooting from the hip off memory. However it makes VCT blend between the two at low rpm low load and anything above the fuel economy load I get Otto cam timing. On a side note, I'm sure it will reduce fuel economy some, however I doubt it will be more than 1-2 mpg.
Well that is good that it helped but there's timing in both low and high mapped points that would push the cams more atkinson. There's less in the higher mapped points. points. Ideally you want to change the mapped point values 0- OP. changing where it's pulling from is good but blending with undesirable values will always still happen. No getting around that.
How I have it set I intentionally left it so the would be some Atkinson in it. But you can always zero out the load table for fuel economy and set the best driveability down to say .15 across the board. That should effectively eliminate the fuel economy stray from being used. I haven't tested that out yet but I have logged my VCT with how I have it set. Currently, I am only seeing Atkinson type cam timing below about 2000 rpm and 45 load. Above that, it is all Otto. And don't get me wrong, I'm not saying I'm done testing. I'm just happy with how the car feels at the moment.
Yes, that was the first change I made since it's so obvious so good that you are thinking the same way. I set mine to FE Max .499 and BD Min .50 and OP to .8
I also have been testing with advancing the cams overall, but still in Atkinson, like moving from 40 to 25 and moving the exhaust the same amount. At the end of the day, I don't think it's worth it, IMO.
I have also installed the GT350 intake manifold and TB so now I am messing around more with the IMRCs, which I think I have good control over.....can't test enough!
Not to mention I finally finished tuning meth at WOT on my C7.....moved over 90 lb/min on a little 1500SL. :-)
Last edited by Higgs Boson; 01-25-2016 at 03:40 PM.
It is an easy way to make the car use drivability values sooner. I can say that. I just think we need to compare fuel economy numbers with drivability numbers and see which way they go. This will give us a good idea of which way we can go with the drivability numbers if we so choose to improve the stock values. It will be the only way you will see a good difference in dyno numbers. There might not be much there but I'm sure ford was conservative with it. It gets tricky though because the IMRC and VCT are so related and dependent on each other to get the improvement out of VCT changes.
GM tuners seems to really know what they are doing. Their newer cars are putting down so much power over stock. I also heard from the GM community that knock was never good. Tuning on the road dyno with a friend it wasn't wait until you see above 2-3*off knock before you tell me to back off. It was if you see any knock tell me to back off. This was one of many rules set to back off LOL
Last edited by murfie; 01-25-2016 at 12:32 PM.
Reply With Quote