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Want to tune DFCO and timing to blow flames during shift: 2000 C5

 
Old 12-05-2017, 08:53 PM
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Originally Posted by G Atsma View Post
That's because most around here are FAR more concerned about tuning for POWER. Tuning for sound is for posers...
Yup, all that POWER tuning goin on around here. That's why there are FAR more 12 second heads/cam LSx cars than 10 second heads/cam LSx cars. Now that we've gotten the insult portion of the evening over Would you like to help make some sweet BRAAAPS or continue arguing Either way is cool with me! Be careful, you might need some hip waders with all the POWER TUNING going on here on this most serious forum on the whole internet.
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Old 12-05-2017, 09:02 PM
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My my, SOMEONE got their panties in a wad! Can't take a little ribbing?? lol
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Old 12-05-2017, 09:12 PM
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Originally Posted by G Atsma View Post
My my, SOMEONE got their panties in a wad! Can't take a little ribbing?? lol
Oh, I'm totally fine. Did someone lose their sarcasm glasses, old man?
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Old 12-05-2017, 09:25 PM
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I can't SEE, no, no, no.
Naw, it's all good, man! Good to see we can all have a little fun!
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Old 02-06-2018, 09:53 AM
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Glad you guys kissed and made up

Here's an update for anyone interested

From HPTuners board:
Originally Posted by VodeAn View Post

We aren't looking for a a visible flame under load, we are looking for a flame between shifts or on decel.

nsogiba, try running less timing, maybe 0 degree or even -5 degrees. Even on bone stock vehicles timing can go negative during TM events. Additionally, to the right of your highlighted point timing increases and then ramps down, you need to look at your timing tables and get it to hold the lower timing, not go from WOT timing to 5 degrees then back up to 20ish and slowly back down like it does in the log. Look at the idle spark tables, not just the main spark tables.
Thanks for replying, I am still working through this.

Part of the issue what that graph was that I had Idle Timing tables that differed. Specifically, they didn't have much timing retard (if any), whereas the main spark tables did.





So I made some changes to retard timing above 3000 rpm at cylinder airmass values in the Idle tables (both in gear and in park, whatever that means since this is a 6 speed manual C5) to match - now I can get a really steady and angry crackle on decel. However, this only occurs with a tiny bit of throttle input on decel (don't recall exactly how much, but only a few % I'd say). I wonder if this has something to do with the "Tumble Flap Closed" values, which by the description decides when the PCM disables main spark tables (what does it start using then? Idle tables?)



My settings seem to have the main spark tables permanently disabled since I'll never go above 250 mph - but going above 1.2% will also do something - so I wonder if that overrides that max speed requirement. Is it one or the other, or must both values be satisfied to enable that effect? Also, does it use Idle Tables when it's not using main spark?

Finally, the last thing I'm looking for is to retard timing DURING a shift (only while No Lift Shifting using N2MB WOTBOX). Is there some sort of condition in which the g/cyl or cylinder airmass changes during a no-lift shift that I can take advantage of to fool the PCM into retarding timing?

I will work on posting up a log during some No lift shift events

Last edited by LQ4-E39; 02-06-2018 at 10:21 AM.
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Old 02-06-2018, 11:11 AM
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Here is a log from some No Lift Shift events (full throttle, press clutch to floor, quickly perform shift, release clutch. Never let off the gas). You can follow it by watching the TPS stay close to 99.6%, and speed will actually spike (wheelspin) as I left the clutch out, followed by a drop in revs as it regains traction.





Unfortunately there aren't any big airmass changes which at this point is the only control I have over changing timing during an event like this. But, there must be some other parameter I don't know about that's rapidly changing during a NLS (look at the O2 sensors switching as the mixture goes full rich when the spark gets temporarily shut off). I'd love to take advantage of that and use it as a control to retard timing...

The last ditch effort is adding fuel above 5500rpm (which is where NLS occurs) but this will probably kill some power and have negative effects elsewhere so I'd rather not pursue that
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Old 02-06-2018, 02:14 PM
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Originally Posted by LQ4-E39 View Post
Here is a log from some No Lift Shift events (full throttle, press clutch to floor, quickly perform shift, release clutch. Never let off the gas). You can follow it by watching the TPS stay close to 99.6%, and speed will actually spike (wheelspin) as I left the clutch out, followed by a drop in revs as it regains traction.





Unfortunately there aren't any big airmass changes which at this point is the only control I have over changing timing during an event like this. But, there must be some other parameter I don't know about that's rapidly changing during a NLS (look at the O2 sensors switching as the mixture goes full rich when the spark gets temporarily shut off). I'd love to take advantage of that and use it as a control to retard timing...

The last ditch effort is adding fuel above 5500rpm (which is where NLS occurs) but this will probably kill some power and have negative effects elsewhere so I'd rather not pursue that
I was just watching a YouTube video of a guy that wired his iat into a normal open switch on his clutch so when he depressed it, it pulled timing and dumped fuel. Impressive fireballs. I'll try and find it again when I'm home.
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Old 02-06-2018, 02:35 PM
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I remember you talking about that trick, I hope it doesn't come down to having to add more wiring since there are plenty of C5s and other LS powered vehicles that blow flames without having to do the IAT trick.
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Old 02-06-2018, 03:25 PM
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Originally Posted by truckdoug View Post
I was just watching a YouTube video of a guy that wired his iat into a normal open switch on his clutch so when he depressed it, it pulled timing and dumped fuel. Impressive fireballs. I'll try and find it again when I'm home.
this it? similar concept.

https://www.youtube.com/watch?v=GwSl...ature=youtu.be


I suppose the first step is to unplug the IAT with engine off, key on while scanning with HPT and see if the IAT reading goes to 14F. hopefully it does. Then it should be as simple as using the clutch switch (cruise switch actually) to trigger a relay to kill the IAT connection. That would be wired to a pushbutton switch so that I don't have the "fireball mode" kick in during normal driving using the clutch.

The only question is if "unplugging" the IAT will throw a code, I don't want to deal with a CEL. Maybe use an inline resistor to trigger it to the correct "temp"? I need a chart that shows resistance vs IAT for a 2000 C5...
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Old 02-06-2018, 06:37 PM
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I cant find the video again but i'm sure that resistance chart should be easy to find. GM uses the same IAT sensor in just about everything.
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Old 02-06-2018, 06:38 PM
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Ok, scanned the C5 with HPT with the engine off.

IAT plugged in (ambient garage air temp): 45*F
IAT unplugged: -38*F

Looks like I'm gonna start sketching a wiring diagram for this
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Old 02-06-2018, 06:41 PM
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double post

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Old 02-09-2018, 06:42 PM
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Please keep us updated on the progress on this. I have the heads and intake off right now and I also really miss my snap crackle pop I used to have before stroking out my LS3.

I was also considering doing the IAT grounding trick, because I love playing with switches... lol. By far my favorite switch in the car is my electric cutout switch. Got a pair of QTP's on the headers... It is deafening, but awesome. I call it 'merica mode. Normal is labeled "suppressed"... It is more than useful when a Honda with a can on it starts barking at my door. I just "tune them out" and I am pretty sure their ***** shrinks when their car starts vibrating from the sound. Not a single one of them has had the ***** to try and run me. If I were them I wouldn't either.

But yes, IAT ground switch would be most convenient to wire in now while my engine is back apart for more go fast mods. I have an auto though, so I won't have the NLS option, but it would be cool to be able to turn the crackle on or off... As you described "fireball mode" lol. It might also be actually useful for some spray too.
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Old 07-04-2018, 03:24 PM
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Hi, any update with this. I have a TVR Cerbera with a supercharged LS1. The USP of a Cerbera is its pops and bangs on the overrun, completely mental from the factory as TVRs always are. I been trying for ages to replicate the effect.

With Dfco switched off and timing set to around -3 deg (1200rpm up) for the top row of the spark tables I get a good cackle on decel but only from about 2000rpm with the throttle shut. I too need to add a bit of throttle on decel to get the same effect further up the rpms. Setting the top timing row to -15 gives a great cackle effect but again it needs to small throttle input to work.

Ill try adjusting the tumble flap min TPS value. But Im wondering if it more air related, maybe need to look at the IAC position during decel but would assume this would be open at high rpm to catch the idle as the rpms drop

Cheers
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Old 08-13-2018, 09:50 AM
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Originally Posted by ChopperDoc View Post
Please keep us updated on the progress on this. I have the heads and intake off right now and I also really miss my snap crackle pop I used to have before stroking out my LS3.

I was also considering doing the IAT grounding trick, because I love playing with switches... lol. By far my favorite switch in the car is my electric cutout switch. Got a pair of QTP's on the headers... It is deafening, but awesome. I call it 'merica mode. Normal is labeled "suppressed"... It is more than useful when a Honda with a can on it starts barking at my door. I just "tune them out" and I am pretty sure their ***** shrinks when their car starts vibrating from the sound. Not a single one of them has had the ***** to try and run me. If I were them I wouldn't either.

But yes, IAT ground switch would be most convenient to wire in now while my engine is back apart for more go fast mods. I have an auto though, so I won't have the NLS option, but it would be cool to be able to turn the crackle on or off... As you described "fireball mode" lol. It might also be actually useful for some spray too.
This has been on the back burner for a while since I've been wrapping up the LS3 swap, but I might get back into it soon.

Originally Posted by TVR_Ric View Post
Hi, any update with this. I have a TVR Cerbera with a supercharged LS1. The USP of a Cerbera is its pops and bangs on the overrun, completely mental from the factory as TVRs always are. I been trying for ages to replicate the effect.

With Dfco switched off and timing set to around -3 deg (1200rpm up) for the top row of the spark tables I get a good cackle on decel but only from about 2000rpm with the throttle shut. I too need to add a bit of throttle on decel to get the same effect further up the rpms. Setting the top timing row to -15 gives a great cackle effect but again it needs to small throttle input to work.

Ill try adjusting the tumble flap min TPS value. But Im wondering if it more air related, maybe need to look at the IAC position during decel but would assume this would be open at high rpm to catch the idle as the rpms drop

Cheers
Any update on the tumble flap setting? I never ended up messing with mine.
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