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My 2007 Corvette has a Vararam intake and an axle back exhaust. But otherwise it is a stock 6 speed LS2. I'm learning my way around hp tuners. I am tuning using the factory narrow band O2 sensors for now. I have been optimizing the cruise VE tables (coefficients) and I think I have that process figured out. I started looking at the spark map to see if there was any low hanging fruit there. I had read people get some improvements with modest timing advancing. So I went for a drive and datalogged to see where I was. I'm seeing spark retard values like this:
I have not touched the stock maps yet.
Fuel is 91 octane. The best we get in Colorado.
Altitude is 5800'. thats why the WOT run is at 80-85kpa.
Can someone help me decipher what I am looking at? It doesn't look like I should be advancing timing if I am reading this correct.
Last edited by Ken Lanham; 02-16-2017 at 10:48 PM.
Reason: Attaching log file
Obviously it looks like a bunch of knock but I'd like to see a log and see if it's actually knock or some oddities that come with the new Scanner that I'm trying to get changed
You also need to set the graph up to match your high octane table. Cyl airflow on the row axis, so you can better see where the knock is. Right now you'd be comparing apples to oranges.
Thanks for helping get me on the right track here. I've been tuning cars with aftermarket standalone ECUs for years. This GM ECU stuff is so much more complicated. I was under the illusion that I might actually know what I was doing inside a tuning suite.
In the image above, below the grid you can see a snippet from the log during the WOT pull, and some Knock Retard Blips. I'll make the changes you mentioned and try again tonight. Do I just attach the log file?
Originally Posted by schpenxel
Post the actual log
Obviously it looks like a bunch of knock but I'd like to see a log and see if it's actually knock or some oddities that come with the new Scanner that I'm trying to get changed
You also need to set the graph up to match your high octane table. Cyl airflow on the row axis, so you can better see where the knock is. Right now you'd be comparing apples to oranges.
The real question is whether it's real or not. Does it go away if you reduce timing?
A somewhat easy test is to add some Torco to a 1/4 tank of gas or so to bump the octane up quite a bit.. if it goes away then then it was probably real. If not, then probably not
Do you still have the low octane table less than the high octane table or did you make them the same?
The real question is whether it's real or not. Does it go away if you reduce timing?
A somewhat easy test is to add some Torco to a 1/4 tank of gas or so to bump the octane up quite a bit.. if it goes away then then it was probably real. If not, then probably not
Do you still have the low octane table less than the high octane table or did you make them the same?
My low octane table matches high octane in the log here. I was tying the VVE table with the tables set up that way. I also had the maf failed...
I was thinking about octane booster. I'll give that a try. Most of my cars at high altitude can take another couple degrees of timing. But maybe not the case here. Maybe the fuel is really that bad.
Pull 8 or 10* out of the low octane table and then also log knock learn factor. If the knock goes away after the first few times then it's probably real. It will bias towards the low octane table when there's knock then slowly go back towards the HO table over time.
My car totally stock I ended up almost entirely on the low octane table, there was that much KR even with the 100% factory tables and "93" octane fuel from around here.. I was never really able to add any timing at all. Then I added the supercharger and meth and E85
Also, It doesn't matter if you have the MAF failed, the high and low octane tables still work like normal on gen 4 ECM's. Gen 3's, not so much..
OP, This will be a stupid question, but noticing you're in Denver, with a pretty good winter like where I'm located.
Is the fuel in the car fairly fresh from a gas station or something that may have been in the gas tank since maybe November when the weather turned bad and maybe now you're just getting the chance to do a little testing? Just a thought...
It seems like to me you are getting major timing deductions--- You need to find out exactly where these deductions are coming from
As an example let's assume you are hearing NO pinging at all--However you are asking for or commanding 20* of timing at WOT but the data logger shows an actual final timing of only 15*
Most often KR deducts if you don't hear pinging are all false
But 1st look at your actual IAT tables with the IAT data log info and the coolant temp tables to see if the recorded data log temps show that the high temps are the cause for the deducts---If so this is where they are coming from
ALL the tuning I do I always have to de-sensitize both the IAT tables and the ECT tables in the tune as the sensors often read higher than actual--This will eliminate the problem IF the deducts are coming from IAT or ECT temps
AS far as the IAT tables go it is not un common for the IAT temps to spike to 130* so I always remove these deducts at WOT up to about 130* as these IAT readings are FALSE--Same goes for the coolant temps but not near as bad or the cause
If you deem that neither the IAT or the ECT deducts are the culprit and still you hear NO pinging then you are getting false knock from the knock sensors--Can be from age or years on the clock or lazy knock sensors-----Again the fix is to "desensitize" the knock tables in your tune to eliminate this false knock---
I would start by subtracting like 5% to each cylinder in the knock tables---Data log again and see if the timing deducts go down---If you still hear NO pinging and yet you have KR then subtract another 5% and data log again---You should be able to remove all false knock--If you begin to hear pinging you went too far and simply back them off some
It is a trial and error process as every car is different
Good information - probably not IATs if the data are recent. February in Denver Co, not likely to see high IATs. I ran DLs just ten days ago in Phoenix and after several pulls, only saw highest recorded IATs at 48*
It's from knock according to the log, not IAT retard or ECT retard or burst KR or anything else like that. That's specifically why I asked him to post the log.
Subtracting from the knock sensitivity cylinder multipliers in HPT would make it MORE sensitive, not less, so that's not exactly good advice. Perhaps it's a difference in the two software packages.
I added a 16 oz bottle of 108 octane booster to a 1/2 tank of fuel. I bought it from the local Autozone that was the only brand they carried. It looked to have some MMT in it from reading the label, so I figured what the hell, good enough for a test. I let the fuel mix around the tank for 15 minutes and ran some more logging. And it seems that my knock counts went to almost zero everywhere. I had a couple 1 degree retards around 4000 rpm. But much improved.
And to take it one step farther and be a little more scientific with the octane theory I just filled the tank today and added 2 gallons of 100 unleaded and 8 gallons of 91 octane winter blend. The engine sounds a touch different under power now. I'll do some more logging and post later tonight.
And for the entertainment of you low altitude dwellers. My barometric pressure reading in HPTuners shows 12.1 psi. It is pretty much a 20% loss of air and horsepower living here.
Last edited by Ken Lanham; 02-20-2017 at 05:37 PM.
It's from knock according to the log, not IAT retard or ECT retard or burst KR or anything else like that. That's specifically why I asked him to post the log.
Subtracting from the knock sensitivity cylinder multipliers in HPT would make it MORE sensitive, not less, so that's not exactly good advice. Perhaps it's a difference in the two software packages.
I don't desensitize using the sensitivity "multipliers" I use the actual sensitivity tables---lowering desensitizes increasing sentisizes
I added a 16 oz bottle of 108 octane booster to a 1/2 tank of fuel. I bought it from the local Autozone that was the only brand they carried. It looked to have some MMT in it from reading the label, so I figured what the hell, good enough for a test. I let the fuel mix around the tank for 15 minutes and ran some more logging. And it seems that my knock counts went to almost zero everywhere. I had a couple 1 degree retards around 4000 rpm. But much improved.
And to take it one step farther and be a little more scientific with the octane theory I just filled the tank today and added 2 gallons of 100 unleaded and 8 gallons of 91 octane winter blend. The engine sounds a touch different under power now. I'll do some more logging and post later tonight.
And for the entertainment of you low altitude dwellers. My barometric pressure reading in HPTuners shows 12.1 psi. It is pretty much a 20% loss of air and horsepower living here.
Sounds like you have some carbon build up in your combustion chambers if with added octane increasers the KR went away
It may be time to have your upper cylinders de-carbonized
I like using Seafoam the best--But not just adding it into the tank but injesting it into your engine at any vacuum port on the manifold
The engine will poor out white smoke which is an indication of the carbon melting awa----I often do this 2 times with some driving in between Some quick lube shops offer this intake cleaning procedure if you don't want to tackle it yourself
I hadn't considered carbon buildup in the combustion chambers. I have used sea foam in other cars before. That might be a good idea to clean things up a bit. I have had the intake manifold off, and the backs of the valves were nice and clean. Nothing unusual there.
The logs show I'm running 5-6 degrees more advance in the 4000-6000 range with better octane fuel. I'm not planning to add 100 octane regularly. But it's probably not a bad idea if I go drag racing. I didn't realize these motors were tuned so close to the limit.
Last edited by Ken Lanham; 02-21-2017 at 12:19 AM.
02-16-2017, 10:06 AM
Tuning Timing, Knock Retard, LS2 HPTuner.
