2GR Exhaust Burbles On Overrun

[scc.131.fe]

Searched for this and didn't find it, so here goes nuthin'.

Can anyone offer some compelling evidence or a well-supported argument for whether the 2GR-FE in the Emira is giving us natural engine burbles on overrun, or if this is a "burble-tune" that Lotus has created in the ECU?

It's probably obvious that I'm asking because I suspect that this is synthetic, or at least "augmented" by software. My primary reason for this suspicion is that the overrun burble pattern seems dead-on exactly the same on my car every time, in every gear, at every RPM, in every drive condition. It seems to lack that sense of randomness, or some standard distribution, that I would expect if the burbles were the result of naturally-occurring "2GR+Lotus exhaust" dynamics.

I'm happy to be proven wrong; I'd love to believe this is the natural "breathing" of the engine on closed-throttle. But if my hunch is correct, I'd honestly consider an aftermarket tune (after warranty expiration) to eliminate any "programmed" burbles. I just want to hear the engine in it's natural state.

Thanks for any insight!

 

[Tomwa]

I'm pretty sure its programmed burbles. I actually find them to be a lot more consistent and louder at low RPM. I don't know if there's a good way to get an answer to your question, other than.

Do early model Evora's have burble? Has anyone tuned an evora GT or otherwise and eliminated burble? I'd say if you are annoyed by it, just drive the car with the exhaust valves closed instead of in sport.

 

[seriously]

I’m just glad it does not pop. Overrun Burbles I like. Pops are obnoxious. I can’t remember how many times I jumped thinking a gun just went off. Oh, no. That’s just a BMW M car.

 

[scc.131.fe]

I'd say if you are annoyed by it, just drive the car with the exhaust valves closed instead of in sport.

Fair point, but of course we love to optimize. Responsibly closing the exhaust valve means Tour mode, which means a different throttle map and less sound on-throttle. After a few months with the car, I just love driving in Sport or Track for the improved throttle response and more howl when I want it. This is squarely within "first-world problems", but as we all grimace or sneer at BMW M cars for piping in "augmented" engine sounds through the stereo, I find myself wanting closure on whether our V6 Emira is simply showing off it's true character or if there's a bit of synthetic theater.

The most ironic, and irrational, part is that if someone proves this isn't a burble-tune, then I'll embrace the sound as authentic and enjoy it more. Some of us are weird that way!

 

[DaaS]

My Evora GT does not burble at all. Every now and then the exhaust will do a loud bang when decelerating and downshifting, which is fun, but no burbles.

 

[cyanmauve]

You know how I know you’re a car enthusiast? This. Existential crisis over the authenticity of exhaust sounds.

I didn’t give thought to this before, but now I do, thanks to you, and it haunts me.

Then again, doesn’t everyone suspect they’re a phony, on some level, deep down inside? Can’t we just embrace it while we’re here, for Pete’s sake?

I’m glad that ABS has been standard on every new car made since I’ve had my driver’s license, otherwise I’d have to make mental apologies to myself to justify buying a sports car with it.

 

[Adam Brouillard]

Well I don't think they are faking any sounds electronically if that is what you are asking. I'm sure the burbles are real in that we are getting fuel ignition in the exhaust, but they have programmed it this way on purpose simply to make that sound because some (a lot of?) people like it. With today's well controlled fuel and timing systems all burbles, cracks, pops, backfires, flames out the exhaust are on purpose although some have reasons other than sound such as anti lag or cylinder cooling. That's generally for racing applications where they don't care about engine/exhaust longevity or emissions though.

 

[Speedy Emira]

Interestingly when I fitted the Milltek full exhaust with cat bypass pipe the burbling sound increased. This was not just at a higher Db but for a more prolonged period. Could this be a byproduct of the exhaust and not programmed in because if programmed it would just be increased Db?
Maybe it’s a mixture of natural burbles and a tiny bit of fuel injected into the exhaust to enhance it.

 

[Tomwa]

There's no fuel being Injected directly to the exhaust, there would be a lot more drama if that was the case.

It is as Adam stated, just a part of the timing mapping and so forth. Functionally it is likely inefficient, and just there for the fun. It's not to say it is electronic, or there's a dial to turn it up or down.

But just like the popping M-tunes, with a direct injection engine actually add fuel when exhaust ports are open and you'd have that sort of popping and maybe flames. There is little to no aspects of modern cars that "aren't controlled". Is burbles on off throttle any less "natural" than induction noise? The pitch of the exhaust based on muffler choice?

 

[Six Speed Stephen]

It’s not coming from the speakers if that’s what you’re asking

 

[Adam Brouillard]

Yeah sorry if I wasn't clear. They aren't adding fuel directly into the exhaust. They primarily just retard ignition timing so that combustion is not complete when the exhaust valve opens and so it continues into the exhaust system. They can also add more fuel depending on how much extra bang they want. I guess with a direct injection system they could probably add more fuel during combustion/exhaust too, but not sure if that is done or not.

 

[Nova]

Yea, the burbles appears to have been something programmed into the Emira. It's there with the stock exhaust. It even burbles in touring mode - just very quiet because of the muffler. But if you listen carefully, you can hear it. In sport/track mode, the burbles becomes louder, of course.

As others have observed, there is also *less* burble at high RPMs. Usually I find that if I lift off 2-3k RPM, I get a long trail of burbles, but if I lift off at 5k, I get a much cleaner engine sound. There doesn't seem to be loud pops - or if they happen they are much quieter than the typical pop and bang tunes.

All in all, very entertaining.

 

[Dragoon]

My pops and burbles are inconsistent and seem to change depending on how warm the engine is, how much load it's under, and possibly even exterior temps. I have an exhaust sound video coming soon that might help show this.

 

[scc.131.fe]

You know how I know you’re a car enthusiast? This. Existential crisis over the authenticity of exhaust sounds.

I didn’t give thought to this before, but now I do, thanks to you, and it haunts me.

Then again, doesn’t everyone suspect they’re a phony, on some level, deep down inside? Can’t we just embrace it while we’re here, for Pete’s sake?

I’m glad that ABS has been standard on every new car made since I’ve had my driver’s license, otherwise I’d have to make mental apologies to myself to justify buying a sports car with it.

This is spot-on, thanks for sharing. And yes, life is great by every measurable standard if we even have 5 mins to comment on things like this for cars this great. But I was haunted by the uncertainty and just needed to know!

 

[scc.131.fe]

My Evora GT does not burble at all. Every now and then the exhaust will do a loud bang when decelerating and downshifting, which is fun, but no burbles.

exactly the type of info I was hoping for! thanks!

 

[KAR120C]

I really like the burbles that Lotus allows a lot more than my M2C which had a lot of pops and sometimes was a bit much. If you play around with it, there is a throttle sweet spot where you're off the throttle enough to get the burble but not completely off. You can get a looong series of nice burbles going. I do this every time I pass my corvette-owning neighbor's house, just on principle.

 

[FST]

I love the burbles on the overrun and some pops, can even be ‘programmed’ more for me

 

[Vampyre]

Emira with 3rd cat Delete and Valve controller - I get a great amount of burbles and some pops.

Evora GT with 3rd cat delete - very little to no burbles and pops.

 

[Speedy Emira]

Emira with 3rd cat Delete and Valve controller - I get a great amount of burbles and some pops.

Evora GT with 3rd cat delete - very little to no burbles and pops.

I totally agree and glad it doesn’t come through the speakers.
It could be an issue for some of the maps available. My M3 was mapped and because I didn’t specify pops and bangs it kinda lost a lot of the burbles.

Am I correct in thinking the i4 Emira has sound played through the speakers like the AMG A45?

 

[FlyNavy01]

While I don't really mind the burble tune, if I had the choice I would remove it. I personally like real engine noises and not pre-programmed inefficiencies just for extra theater. Not really an issue either way though. The stock exhaust with the valve open is almost perfect otherwise.