Installed ARH midlengths on my C7 Z51 and lost that snap crackle pop on decel??

[TriPinTaZ]

When my mods were AFE intake, ported IM/TB, and Borla catless X with S-type NPP (stock exhaust manifolds and primary cats), I would get lots of good gurgling snap crackle pops on decel when going in or out of DFCO.

I added ARH midlengths with hi flow cats, adjust the tune slightly for the changes but nothing that would affect decel MAF area or DFCO. When looking at my logs everything looks great. DFCO is still kicking in like it should and everything is almost identical from a log standpoint prior to the ARH install.

BUT, the big BUT, I've lost the real good pops and crackles from the exhaust. I get louder burbles but it doesn't pop like it used to and I really loved that sound. I was actually hoping it would pop and crackle even more. I tried adding some fuel in the VVE area on decel, but it just started to throw my LTRFT's off (started going too far negative in that area).

MAF, MAP, Timing, Fueling etc all match up prior to the headers in the logs, but the pops are gone. It used to pop real nice when cold, but even that isn't the case anymore. Is this something I just have to accept that I lost, or is there another way to bring them back on the Gen V stuff?

Thanks

[Higgs Boson]

GenV are torque based and don't have tables for DFCO spark like we used to. Low spark values would let the pops through.

[TriPinTaZ]

Right now it has about 15 degrees of total timing on decel after modifiers and TMA. Should I drop it a lot closer to zero?

[Ben Charles]

You want pop pull timing out

[TriPinTaZ]

Thanks guys!

I'm going to try dropping it so that its at or near 0 degrees of timing on decel after the Torque Management Advance modifier(pulls about 22-25 degrees).

Taz.013.ARH.POPPOPBANG.hpt

[lt1z350]

So on older stuff it was normally caused by overly rich and dumping fuel into exhaust and burning as on my big cam cars I had to get the ve all correct and went away. So this new stuff its more timing causing it? or lack of timing? I have a ats 2.0t the kid wants it to pop and gurgle and told him now with trims in line and running well it wont do it. So just drop timing in the decell zones to negative and thats it?? I told him not jacking the tune up just to make it gurgle.... lol oops

[TriPinTaZ]

I lowered the High Octane table in the decel area and it made a very small difference. But it seems like when I lower the timing, Torque Management Advance doesn't pull as much timing out when I lift off the throttle. I'm going to try just setting everything in the airmass 0.12 and lower to 10 degrees and also changing the DFCO enable/disable speeds in gears 1-3 to make it fall out of DFCO sooner during decel like the C6 Z06s do. I'll report back if it makes a difference.

[TriPinTaZ]

Update: With the decel area set to 10 degrees of timing in the High Octane table I am able to get some pops again. It's nothing like my C6 Z06 was, but there is no way to control the DFCO blend times and such. I'm actually going to remove the enable/disable speed values and return them to 0. I get the most pops during the transition into DFCO. By setting a MPH it actually is delaying DFCO beyond the sharp throttle change when you lift the throttle and I only get burbles when that happens. So as far as I can tell right now, it makes the most noise in the transition to DFCO when spark is very low. I have it set to 10 degrees and then Torque Management Advance pulls even more.

[TriPinTaZ]

OK with DFCO entry and exit set to stock values, and decel timing set to 10 degrees I get some really good pops and bangs. Now that I know it works, I'm going to reduce the popping since I am running high flow cats. Too much popping and banging can super heat the cats.

But folks I would say this one works. Set timing to 10 degrees in your High Octane table at .12 airmass and below between 4000rpm the exit point of DFCO (1200 RPM for a manual Corvette) and you will get some real good cackles and a few bangs.

[TriPinTaZ]

I'm going to try something new today. I'm going to try leaving the timing higher but using the cam advance(technically retard) in the airflow cam baro tables to see if that brings the crackles back. I forgot I had zero'd out the decel part of the the table so the car wasn't pulling any cam timing back but only torque management advance. I'll report back if this method works too.

[TriPinTaZ]

OK so putting the High Octane spark table back in the 40's (stock values) allows torque management advance to pull more timing out on decel but not enough to really make it pop. But when I add the cam retard back in on the Lo/Med/Hi Baro tables it helps the pops a little. I think I'm going to leave it this way.

But I can confirm, anyone looking for some real loud pops and bangs, just drop the decel timing area to 10 degrees. Likely not a good idea long term if you have cats since it will heat up the cats more. But if you are catless, you can have a real good time with these settings.

[TriPinTaZ]

Another follow up. I was able to get the OEM pops back by putting the decel timing back in the 40s and allowing torque management to pull the timing out on DFCO entry. And I was able to get torque management advance to act more like it did when stock by adjusting my DD tables slightly. So basically it was all in the DD tables.

If I had no cats, I would drop the spark to 10 degrees on decel and then add speed values to the DFCO table like the C6 Z06's have. When I tested this I was getting all sorts of super loud pops and bangs. But it generated a lot of attention around town and I was worried about my Cats getting to hot.

[TriPinTaZ]

One more update to anyone that reads this. I have found that the answer is in the Minimum Final Spark tables. Change these to allow spark to drop lower where you want the pops on decel. It is very effective. This way Torque Management does its thing on decel but is allowed to pull more timing out and you can blend it to the RPMs where you want the noise.

This way you don't have to drop your High Octane spark table at all which can cause an annoying drivability issue when you are at cruising speeds and let off the gas. If you change your High Octane table and you let of the throttle on the highway you can feel the car buck back and forth. If you let Torque Management worry about this and just lower your Minimum Final Spark the weird twitching goes away. It's much smoother this way. Also, if you try to do this with the High Octane spark table, you don't actually get a longer period of pops and crackles. You just get a couple of loud ones because timing falls so fast but then it is still limited by the factory values in the minimum spark advance table.


Final Answer : Minimum Final Spark tables is where to get this done properly

[Frost]

I spend so much time getting rid of that noise... it's very hard to imagine the customer that wants MORE of it, but I guess, they all want something different.

[TriPinTaZ]

I spend so much time getting rid of that noise... it's very hard to imagine the customer that wants MORE of it, but I guess, they all want something different.

I think it sounds wonderful. I can't imagine why anyone would want less of it.

[lt1z350]

Depending on your exhaust it can become annoying. I found on stock mufflers it’s not bad on some straight through like a buddies 07 vette with borla it was so loud it drove his wife nuts when daily drove the car being it’s a manual so seems to do it worse then autos. As you can raise the values in the wot area to get rid of so much power cut on shifts it’s nice to know you can also use this table to achieve this outcome. I do have some 2.0t customers wanting this but did try it on the camaro and ats and didn’t work as well but seems to work great on v8. Maybe it’s just the e80 that’s not liking the changes. Been playing with it on a 2017 ats as customer really wants it but yet to hit it and done all the common changes including this and the long term table. I had to raise virtual torque on that car so I guess it could be as simple as when it blended my changes it now commands too much timing to meet requested torque. Maybe I need to go crazy and really drop the timing as was staying in the -10 to -20 range.

[HeavyChevy305]

Depending on your exhaust it can become annoying. I found on stock mufflers it?s not bad on some straight through like a buddies 07 vette with borla it was so loud it drove his wife nuts when daily drove the car being it?s a manual so seems to do it worse then autos. As you can raise the values in the wot area to get rid of so much power cut on shifts it?s nice to know you can also use this table to achieve this outcome. I do have some 2.0t customers wanting this but did try it on the camaro and ats and didn?t work as well but seems to work great on v8. Maybe it?s just the e80 that?s not liking the changes. Been playing with it on a 2017 ats as customer really wants it but yet to hit it and done all the common changes including this and the long term table. I had to raise virtual torque on that car so I guess it could be as simple as when it blended my changes it now commands too much timing to meet requested torque. Maybe I need to go crazy and really drop the timing as was staying in the -10 to -20 range.

I brought it down to zero degrees and now it gurgles a lot but doesn't pop as much as I would like. Kinda rather have it the other way around. Going negative on decel won't hurt anything?

*edit* Went to -5 degrees and now it's good.

[Frost]

I think it sounds wonderful. I can't imagine why anyone would want less of it.

It's a noise that draws attention while doing NOTHING for you; at all. The car doesn't drive better or make more power, or pickup response or mileage from making this noise.... It's like guys that buy Harley's and just immediately move the exhaust just to open pipes and sit around at stop lights revving. But maybe that's all they really wanted out of their "performance experience", was to have others look at them, not to actually be faster. Also the internet can be hard to read and the reply you made could have been sarcasm. In which case, I am on the same page!

[TriPinTaZ]

It's a noise that draws attention while doing NOTHING for you; at all. The car doesn't drive better or make more power, or pickup response or mileage from making this noise.... It's like guys that buy Harley's and just immediately move the exhaust just to open pipes and sit around at stop lights revving. But maybe that's all they really wanted out of their "performance experience", was to have others look at them, not to actually be faster. Also the internet can be hard to read and the reply you made could have been sarcasm. In which case, I am on the same page!

I have a manual, so unless I want it to pop, it doesn't just do it. Normal driving it does not make any more noise than usual. But if I'm holding a gear at a higher RPM and go into a deep decel it makes lovely noises as it enters DFCO.

[TriPinTaZ]

I brought it down to zero degrees and now it gurgles a lot but doesn't pop as much as I would like. Kinda rather have it the other way around. Going negative on decel won't hurt anything?

*edit* Went to -5 degrees and now it's good.

You're talking about your minimal final spark tables right? Both Base and Long?


You don't need to do anything to your High Octane tables. Mine are still in the 40's in the decel area. But when you drop the minimum spark table it allows Torque Management Advance to pull out more timing in the decel area. This is what makes the pops and crackles louder and longer. I have found it pretty much works just like altering the DFCO spark blend tables on the Gen4 stuff. The Gen5 stuff doesn't have those tables but I have a hunch the Minimum Final Spark tables have replaced the DFCO blend tables from the Gen4 stuff.