Dragstrip still getting knock retard.

[Wilburbill]

I have still been tuning my ECS supercharged LS2. Hard driving on the highway and in town I had no spark knock. Today took it to the 1/8 mile drag strip and made 2 runs. In the first run the log showed spark knock so I took 2 degrees out and made one more pass. I still had some so I decided to stop until I could hopefully get some advice on what I need to do to fix it. The car ran well and pulled hard on both passes. I do see on the log that the air intake temp got up to 126 so I'm sure that doesn't help. I did let the car cool off for 1/2 hour between passes and I didn't have to wait in line. I am attaching both logs and my tune. Could someone guide me in what to do to get rid of the spark knock?

[07GTS]

need more fuel by the looks of the log, your commanding 0.780 but the WB says up to 0.983 so ur close to stoich under boost which wont be good for timing, with that dialed in should help, your IAT's go well into the table that removes timing so u may have to get better iat cooling or lift up the zero part if its safe to do so, i dont take out timing till IAT 80c with PD blower which i never see that high but yours is into the 50's and u start to remove mid 40's so u will loose a little from that also

[NJ_Phil]

I'd enter PE at a lower kPa, not 90 and run a flat PE of 1.28 across the entire RPM band or at least richen it up on the low end. You can see the KR under low rpm/high load during the burnout and when it launched.
High IATs aren't helping either but spraying meth would help a lot if that's possible. Not sure what tires you were running but they shook pretty hard at the top of 1st and 2nd...looks like after you pedaled it though

[jsllc]

MAF is off and need calibration, transient fueling needs adjusting. You are hitting 14.5 under 6psi of boost while commanding 11s. Until you get these fixed I would use 1.3125 in PE at least. Way too lean under boost. Change manifold volume to 13k and delay to 25 under transient for starters. After you fix you fueling then look at knock. Unless you have changed compression greatly you should be able to run at least the 12 degrees of timing you have under full boost assuming 91 octane. More details about build and fuel would help.

[Wilburbill]

Thanks guys! I'm out of town a few days when I get back I will make the changes.

[Wilburbill]

Jsllc, the car is an 07 vette LS2, 1 7/8 Long tubes with x pipe no cats, ECS supercharger kit, Novi 1500 supercharger with restrictor plate around 9.5 lbs boost, ID1050 injectors. I am running a SD only tune with 93 octane fuel.

[jsllc]

Who did this? You do not have an SD tune but rather a VVE. VVE will never be as accurate as SD because it is not a table but rather a set of formulas using coefficients. Your VVE is NOT ready for racing. It needs serious work. Is there some reason you are running this with MAF failed and only VVE?

[Wilburbill]

Yes, the reason is it surges with the maf. What's wrong with the vve? I'm sure it still needs some work but car runs pretty good over all. Looks like I need to add some fuel under boost..Hp Tuners doesn't show me an option to switch to a ve tune for my operating system. I have a DSX ecm that has the custom ve operating system and intgrator delay but car does not run well with it so I switched back to original ecm.

[jsllc]

Yes, the reason is it surges with the maf. What's wrong with the vve? I'm sure it still needs some work but car runs pretty good over all. Looks like I need to add some fuel under boost..Hp Tuners doesn't show me an option to switch to a ve tune for my operating system. I have a DSX ecm that has the custom ve operating system and intgrator delay but car does not run well with it so I switched back to original ecm.

Here is your VVE. There is no way fueling should change like this. The reason it surges is MAF needs tuning. Nothing wrong with VVE but it is a close enough is good enough technology. Was always considered secondary to the MAF. This car can run great just needs some TLC on the tune. FYI the ECM always uses both if they are there no matter how you try to force it. Unless it finds one failing. All we get to do is tell it which one is more important or points to switch importance.
9-26-2017 9-31-54 PM.png

[Wilburbill]

So what should a supercharged VVE look like? Should I start over on the VVE and if so what do I use for a base to work from?

[jsllc]

They are different for every car and application. So no standard just what it should be for your car. In your case fueling issues are affecting timing and all of that is changing the shape of the VVE. GM's approach is this is a fail back table. If you want to run with it fine but in order to get it right you should get the rest right then tune it and run it.

The VVE is a view into how air/fuel and timing are affecting the efficiency of the engine.

I tune in this order:
1. injector data. All injector data including injector tip temp and eoi
2. MAF and basic idle
3. timing
4. finish idle
5. VVE

Others may have different orders. This way works for me and produces consistent results from car to car and day to day. Without this being completed you are chasing issues caused by other things. Lastly i work on TQ management. When all this is done it seems (if it is my car) I go back and do it all again and again in search of perfection.

Sorry no quick fixes here.

[jsllc]

Remember this opinions are like rear-ends. We all have one. You have to decide if you are in this for the haul or not. If not hand it off to a "TRUE" tuner and wash you hands of it and love it when you get it back. I say true tuner not referencing any one but rather do not assume you email some guy with $250 and life is wonderful. I have seen tooooo many of those.

[Wilburbill]

I was just trying to figure out what part of the VVE needs serious work. I have looked on the tune repository but I have no idea if those are right. I have looked online and all those are different also. It's confusing to me to figure out what's wrong with the VVE when someone just says it needs serious work. I'm not trying to be a smart ass or be difficult I'm trying to learn how to do it right and how to tell what a basic properly done VVE table looks like. For example some are real smooth with no bumps or valleys but there was a post on the forum not to smooth them too much. Some have more peaks and valleys than mine. There has to be some basic principals and rules to a good VVE table?

[jsllc]

Every one is different. You cannot look at one and apply to another. After you look a hundreds/thousands of tunes you start to look at tunes and can see little issues. I really do it in this order

1. injector data. All injector data including injector tip temp and eoi
2. MAF and basic idle
3. timing
4. finish idle
5. VVE

Based on your logs VVE has need of work to clean up lean spots. For me on GM e38/e67 I would run them MAF/VVE like intended. If I was to go to SD I would make sure to have the ecm that supports the SD OS patch from HPT. That is just me.

I have no details about the build. To do a tune you really need to know every detail.
Your injector data needs work for EOI (cam specs) and injector tip temp. If changed later causes you to have to redo other things.
Your MAF needs a little work then the data from it can be used to build a base VVE
Timing needs to be solid. If changed later it changes VVE. So you want to be very close to final
After all of that is done your VVE will be off. Take some math from logging, build a base VVE and then use WB to adjust the errors. This will give you a usable VVE that does not have lean spots. It however will never yield and exact match to commanded because a formula cannot truly represent an exact match to the volumetric efficiency of the engine

I have no step by step manual. Most here will help. I know there are info manuals and training offered by some that will help start this process with you. I bought many tutorials when I first started. When complete you will have a car that runs like you want. Here is a VVE from a 2012 ZL1 turning 1150HP. It won't match yours. Cam is different, boost is different, timing is different, injectors and fuel pump setup is different. That is why it is not a quick fix by copying from another car. Even if they were identical mechanically I seen differences in the VE. Sorry I wish there were better simple fixes. It just takes a little time and some TCL. You will get it there.
9-28-2017 11-54-41 PM.png

[jsllc]

Here is an example of the same car with VVE and MAF tuned. It is getting a new cam today so VVE will all have to be gone back through.
9-27-2017 9-29-59 AM.png

[GHuggins]

I think what's throwing off your VE table is how your gathering data - your compensating for a transient fuel problem as Scott has pointed out that you have, with your main airflow model... Here's your next problem - your barometric pressure "another important part of the airflow calculation" is changing every time you go into boost and when in SD calc mode - this can and will change your fueling up to 10 percent depending on your altitude (higher altitude = the more it'll be thrown off / lower altitude = may not even notice it much) - that alone will usually cause never ending tail chasing...

Best thing I could recommend is going back to the other ECM, apply the 2 bar OS upgrade, copy over your current tune file, make sure injector data is correct then do as Scott said and tune in your SD table with slow steady state throttle movements using stft's and wideband error... If it's lean during stomps and your air model is tuned in like it should be then you have transient errors and should only adjust that portion of the tune... Main difference in your VE table and Scott's posted one is that yours will keep increasing with boost and rpm - centri's don't really cap out - normally - and as previously stated - this will all be different with your engine setup...

[Wilburbill]

How do I stop the baro. sensor from changing? I have a DSX ecm https://dsxtuning.com/collections/tu...nt=30980907595
It has a base tune with the 2bar os loaded in it. I just cant get it to run right with it. It just doesn't want to rev up quickly (feels like I'm pulling a trailer with a dump truck on it. The stock ecm works better. I'm sure it's my lack of knowledge in tuning that is the problem with it. I would be glad to use it but I spent days trying to get it to run decent and I finally gave up as I had several trips planned and needed the car.

[jsllc]

If this ECM has the 2 bar patch and is SD then it should not be changing the BARO. It also should have a SD table. Is this the tune below??????

I have customers with those and the OS is different. This is an older OS. Did you somehow flash from the older ecm over the newer one?

[Wilburbill]

The original ecm is in it now. The tune I posted is out of original ecm. The ecm with the 2 bar patch is sitting on my work bench. I can't get it to work. I can post a tune from that ecm later when I get to my computer.

[GHuggins]

The baro update is built into the core OS from GM - you can't keep it from updating without the enhanced 2 or 3 bar OS available from HPT that is on your other ECM... It's not hard to load a different vehicle onto another ECM - just can screw things up if the ECM wasn't compatible with it and then not to mention burn through some credits...