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Discussion Starter · #1 ·
I made 26 pulls on the dyno today in an attempt to finish the tuning with the newly installed Magnacharger. We seem to have run into a glitch at 4800 rpm with the a/f ratio. Regardless of what we did, we could not smooth that line out. Even changing one cell at a time at 1% increments failed. I believe we tried .50% increases/decreases as well. Take a look at the following graph.



I have a copy of ALL 26 pulls in order. If anyone has the knowledge and is willing to take a look and help out, I would certainly appreciate it.

We are stumped! :confused:
 

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Discussion Starter · #2 ·
 

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Discussion Starter · #4 ·
redhardsupra said:
what were you changing? PE? MAF? VE? OLFA?
Well, the tuner was adding or subtracting fuel just like you would with any other tune. Isn't that VE??
 

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nowhere near....

'Adding fuel' is a horrible phrase left over from LS1Edit days when you didn't have access to VE, only injector settings, so you'd lie about the size of injectors, trying to make a right with two wrongs. This method can produce pretty dyno graphs, but it cause horrible drivability issues, as injectors table is only pressure referenced (MAP), and not RPM and MAP dependent like the VE table is. Therefore, if you set it up to run well for WOT conditions, it will run at the same settings at any rpm, as injectors table simply cannot express that level of detail. It's 2D vs 3D, you're actually losing an entire dimension of expression and precision. Do you really think your car needs the same amount of fuel at at the same pressure at 1000rpm and 6000rpm? :/ This method simply cannot work right for anything but producing dyno graphs.

The real problem is that all the 'pros' that learned to tune back in the days of LS1Edit, have failed to catch up with the times, and realize there's a lot better, easier, more flexible way of doing things. Unfortunatelly to harness all that new power, you need to spend a lot more time on each car, which to them is simply financially suboptimal if they're still gonna get paid the same money.

Now, with the LS2s, a new problem arrived--the VE table is all kinds of new and unknown and few people have figured out how to deal with it correctly yet. So, they've gone back to hacking MAF and IFR, just like in LS1Edit. I've looked through a lot of tunes on this board, and they're largely old-school hacks on new-school hardware.

Post some logs and tunes and I'll show you what I'm talking about.
 

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EFILive Junkie
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Where was the wideband sensor placed when doing the pulls? If the car has Cats then you need to ensure it is placed BEFORE them as that will throw off the readings you see.
 

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Discussion Starter · #7 ·
Black02SS said:
Where was the wideband sensor placed when doing the pulls? If the car has Cats then you need to ensure it is placed BEFORE them as that will throw off the readings you see.
No cats...O2 sensor placed in header just below front right wheel.
 

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Discussion Starter · #8 ·
redhardsupra said:
nowhere near....

'Adding fuel' is a horrible phrase left over from LS1Edit days when you didn't have access to VE, only injector settings, so you'd lie about the size of injectors, trying to make a right with two wrongs. This method can produce pretty dyno graphs, but it cause horrible drivability issues, as injectors table is only pressure referenced (MAP), and not RPM and MAP dependent like the VE table is. Therefore, if you set it up to run well for WOT conditions, it will run at the same settings at any rpm, as injectors table simply cannot express that level of detail. It's 2D vs 3D, you're actually losing an entire dimension of expression and precision. Do you really think your car needs the same amount of fuel at at the same pressure at 1000rpm and 6000rpm? :/ This method simply cannot work right for anything but producing dyno graphs.

The real problem is that all the 'pros' that learned to tune back in the days of LS1Edit, have failed to catch up with the times, and realize there's a lot better, easier, more flexible way of doing things. Unfortunatelly to harness all that new power, you need to spend a lot more time on each car, which to them is simply financially suboptimal if they're still gonna get paid the same money.

Now, with the LS2s, a new problem arrived--the VE table is all kinds of new and unknown and few people have figured out how to deal with it correctly yet. So, they've gone back to hacking MAF and IFR, just like in LS1Edit. I've looked through a lot of tunes on this board, and they're largely old-school hacks on new-school hardware.

Post some logs and tunes and I'll show you what I'm talking about.
The tuner is an "old school guy" using LS1 Edit, but does have several other tuning programs. He has tuned LOTS of big money, big horsepower cars (new and old) with lots of success. However, he will be the first to tell you he doesn't know it all, and it was his suggestion that we post up and see if anyone here would be able to help. He is open to all discussion!

As for the tune itself. He spent an entire day doing the "part-throttle" tuning. He has explained to me in detail why this needs to be done before the WOT tuning. So, it kinda debunks your first guess.

Here is an example of what I mean. Look at the first graph. What he did was to try and lean out I believe the 4800 cell and slightly richen at 5200. The % increments we used were 1% and look what happened!

 

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Discussion Starter · #9 · (Edited)
Look at what a 1% increase did at 5200 rpm? What the hell??

For some reason the changes made at those rpms are EXTREMELY sensitive, and the computer seems to over-react.

Someone mentioned that the MAF is maxed out at that time so the fuel tables are even more touchy? Any truth to this thought? If that were the case, isn't there a little bigger maf to try? Just wondering....
 

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ChimChim is in the HD's trunk
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Have you tried hooking up a fuel pressure gauge? Maybe you are losing fuel pressure.
 

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Without knowing more details as to what exactly your tuner is doing, we could only guess. Talk him into posting up a bin file so we can look at it. Is he using HPTuners or which tuning package? If hes adding fuel 1% at a time to the VE table hes kinda wasting his time, but again, we can only guess.
 

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Discussion Starter · #12 ·
Owe5Goat said:
Have you tried hooking up a fuel pressure gauge? Maybe you are losing fuel pressure.
We did have a fuel pressure gauge hooked up. I watched it myself for about the first 10 runs and it held steady upwards in the 60 range if I remember correctly. I wondered the same thing again on my way home when the fuel light came on.
 

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You wouldn't be tuning the VE table under boost, unless the maf is disconnected and you've converted to 2-bar speed density. Once the maf is pegged you go to the PE table to adjust A/F. This is where I would change to speed density and ditch the MAF as it gets pretty sketchy tuning beyond this point in my opinion. I was there with my twin turbo LS2 GTO and I had to command 9:1 in my PE to get 11.8:1 A/F.

I did not think the Maggie would peg the stock MAF though, at least not at stock boost, although with mods, no cats, etc. it is possible.

Jody
 

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lanceygto said:
I just want to post here on behalf of those of you peek in and who do not understand the above post due to lack of knowledge. Right now I am reading a book on EFI tuning by Jeff Hartman which I recommend for all of us who have no previous knowledge of the above and related subjects. From the moment you in as much as add a KN filter should read this book.
that is an excellent starter book. then you should go through:
building and tuning high-performance electronic fuel injection by Ben Strader of EFI101 fame

then depending on your application, NA:
Four-Stroke Performace Tuning/Modern Engine Tuning (both by Graham Bell, cover a lot of the same ground so just get one)
Smokey Yunick's Power Secrets

and for Forced induction:
Forced Induction Performance Tuning by Graham Bell
Maximum Boost by Corky Bell

And if you still haven't had enough go for the mothership:
Internal Combustion Engine Fundamentals by John B Heywood just remember that if you can't do differential equations before breakfast, this might not be for you
 

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Whisky said:
As for the tune itself. He spent an entire day doing the "part-throttle" tuning. He has explained to me in detail why this needs to be done before the WOT tuning. So, it kinda debunks your first guess.
great! i'd rather be wrong than have you living with a shit tune ;) I'm just telling you how it usually is, because this board seems to have all the wrong tuner myths proliferated through it more than ls1tech, and that's an achievment! spending a daying doing VE is a very good sign, but of course, there's many ways to do that wrong too.

As for the graph, this is a severe hit. I'd check mechanicals first, especially that the big hit starts in the range where usually you got peak torque, something might just give up.

Another thing: Injectors--what do you have, what fuel pressure, and how is it configured?
 

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Discussion Starter · #16 ·
redhardsupra said:
great! i'd rather be wrong than have you living with a shit tune ;) I'm just telling you how it usually is, because this board seems to have all the wrong tuner myths proliferated through it more than ls1tech, and that's an achievment! spending a daying doing VE is a very good sign, but of course, there's many ways to do that wrong too.

As for the graph, this is a severe hit. I'd check mechanicals first, especially that the big hit starts in the range where usually you got peak torque, something might just give up.

Another thing: Injectors--what do you have, what fuel pressure, and how is it configured?

Injectors are Bosch 42lb. Fuel pressure was stable around the 60 during the earlier pulls. Wasn't watched after we established fuel pressure. Another thing about fuel pressure I was thinking is that after we left, the fuel gauge light came on, so I was getting near the eighth tank mark. During the dyno that thought never crossed my mind.

MAF: First, as I was looking at the fuel tables on the laptop I noticed that after 4000 or so rpm the numbers almost doubled. I asked him how come such a big increase and he showed me that around that point the maf sensor was maxing out and that differences had to be made up in order to ensure enough fuel. 10,000 ring a bell for the maf maxing out??

What just gets me is that it should not be that difficult to subtract a little fuel at the 4800 mark where I ran rich and add just a touch at 5000. That's all I want. The hp/tq numbers will be what they'll be. I want a straight line on the a/f!! The tune that is in the car now is the first graph, I just need to fix that little 4800-5400 mark.

Mechanicals? I'm wondering why it would only have an affect between 4800-5400 rpm.
 

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You may want to check to make sure your plug wires are not shorting out on your headers during a pull, if the plug wire get shorted out you will experience a quick drop in power and a big spike in fuel beings the injector is still pumping and the spark is out.
 

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Discussion Starter · #18 ·
Crash said:
You may want to check to make sure your plug wires are not shorting out on your headers during a pull, if the plug wire get shorted out you will experience a quick drop in power and a big spike in fuel beings the injector is still pumping and the spark is out.
Thank you. I will check that!
 

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What valve springs are you running?
 

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Discussion Starter · #20 ·
Rob said:
What valve springs are you running?
Yellow LS6 springs that came with the cam from LPE. I know EdHenderson has the same set-up and he seems ok with them. What was your thought?
 
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