Looking for that "magical" exhaust note

[Iconic Ride]

While the forum was "down", and looking for my Esprit "fix", I ventured over to that other fine site, LEW. Have perused many of its pages in the past, but elected to concentrate on the muffler/silencer/exhaust area. Many have commented on the, shall we say, "less than stellar" exhaust note of the stock Esprit exhaust system. Several have attributed this to the "flat plane crankshaft" feature of the V8. Not being a harmonics expert, I have always wondered just how this design characteristic could produce its "unique" tone. Is the "firing interval" perhaps significantly different from a "normal" crankshaft?

While examining the various options available, either from Lotus (i.e., the "sports exhaust"), or as an "aftermarket" retrofit (Larini, among others, seemed to be a viable and attractive offering), I came across a comment that appeared to state that the "U.S. specification" exhaust had a "good" sound to it. Am I to take it that all Esprits shipped to the U.S. arrived with a "non U.K." exhaust? Do U.S. Esprits actually sound a bit different from the U.K. stock version?

Lastly, are there any sites that can produce with true fidelity on laptop speakers what the different systems put out? Desktop speakers maybe?

Cheers,

John

p.s., am not looking to remove the CATs.

[Fred Basset]

Others can probably give more information but my UK V8 has the federal pipes which exit in the centre. These do indeed sound "nicer" than the normal pipes or the sport box which exits either side of the rear valence without being too noisy. I like them.

Regards

Fred

[aerobat]

I don't have any sound clips, but I do have a North American V8 with the dual centre exhausts, and I have just gone to de-catted Larini's. The note is very nice - not harsh, and not overly loud. But it does have a definite performance note to it..... and that is good.

B)

[Günter]

John, there is an naturally difference in the rev's vs. firing note of 90

[Iconic Ride]

Thank you Fred, John, and Gunter for your replies. Sounds like the different exhaust notes are all over the map, figuratively and literally. It never occurred to me (but makes sense) that there would be a difference between the "old" style side exits and the "updated" center exhaust. Anyone out there with the Larini system WITH cats still installed (and with the old style exits)?

Would still like to know if the UK "Federal" exhaust is of a different design than the "U.S. spec" on the old style pipes.

Gunter, regarding the flat plane crank, are you saying that the number of ignition firings per complete revolution of the crank is greater than a 90 degree crank? In other words, is it the case that, for a given RPM as displayed on the tach, the 918 motor is actually putting out more "impulses" than "normal" motors? Now that would be interesting! Is there any (other) inherent advantage to the flat plane crank?

Regards,

John

[act2007]

1...are you looking at upgrading to high-flow cats? or just stick w/stock cats?

2...One of the best combination on the V8 that I've heard was Larini high flow cats with the US center exit exhaust...very very sweet tone.

3...you can take a looking at this video for a US center exit exhaust + test pipes...similar tone but not as loud.

4...I had the US center exit exhaust with stock cats before, and the tone is very sweet as well, but my complaint was too quiet.

Alan

Edited August 1, 2008 by E5PR1T

[Günter]

@John H. : maybe my explanation wasn't detailed enough? What i meant is the difference of how many equal positioned firings you have in one bank/per revolution. Or in other worts our engines sound (and work) as two separate in-line 4cylinder systems. That means it revs-up easily, but there is no "shakin"-sound of an US engine.

[Iconic Ride]

Hi, Gunter. It's becoming a little clearer, but I'm still not sure what "equal positioned firings" describes.

[Günter]

normally all worldwide V8 have an firing every 90

[Iconic Ride]

1...are you looking at upgrading to high-flow cats? or just stick w/stock cats?

2...One of the best combination on the V8 that I've heard was Larini high flow cats with the US center exit exhaust...very very sweet tone.

3...you can take a looking at this video for a US center exit exhaust + test pipes...similar tone but not as loud.

4...I had the US center exit exhaust with stock cats before, and the tone is very sweet as well, but my complaint was too quiet.

Alan

Great "link", Alan. Thanks.

As with all things Esprit, it comes down to costs vs return in value (and what "Mama" will permit me to expend). I'm operating under the assumption that the cats have to stay (standard or high flow) in order to pass the annual emissions test. It's, of course, a totally personal judgement, but I'm not a huge fan of the center exits unless the taillight mod is done concurrently, and that bumps up the total to an amount I'd rather spend on other things (gas, food, college tuition for the older son, etc.) Plus I'm quite content with the "classic" (almost Testarossa-like ) "uber wide" look of the standard taillight treatment.

What I did take away from the video link (I watched and listened to several examples) was the fact that ALL of the cars sounded REALLY GOOD at about 3,500 RPM and up. In the cabin you don't get the full benefit, what with all the other sounds (road noise from the tires, wind noise, etc.) competing for your attention. But it's nice to know the effect is being transmitted to your audience outside. With this in mind, I have decided to bump up my idle to 3000 RPM in order to get "a head start" towards reaching the "sweet spot", and as an added advantage my "hole shots" have improved significantly--just kidding, not looking to have to replace the clutch each week.

Bottom line: I'd consider the Larini side exits through existing cats (am assuming this is an option), but would like to hear what it sounds like. Would it be "pointless" to use Larini without the high flows?

Regards,

John

[quote name='G

[Günter]

as bore and stroke create the swept volume, maybe. 'our' engine capacity's over here are normally in an range of 1.8-2.5 L for 4cylinder family cars -and up to 4 or 5L V8 /6L V12 for luxury's. So you cant compare them directly in my eyes !

[neal]

The advantage of a flat plane is that the crank is a lot lighter since it only requires strength in one plane whereas the cross plane requires strength in two planes. Also, the cross plane requires big counterweights on the crank to cancel out the vibrations. This allows the the flat plane to rev higher and produce more maximum power. However, the lower revving cross plane gives more bottom end torque.

However, the counterweights on the cross plane cancel out the vibrations perfectly but the different type of vibrations on a flat plane can't be cancelled out so the cross plane is a lot smoother.

But what makes the difference in engine sound is the firing order. If the cylinders are numbered:

1 2 3 4

8 7 6 5

the flat plane fires:

1 - 5 - 3 - 7 - 4 - 8 - 2 - 6

whereas the cross plane fires:

1 - 5 - 4 - 8 - 6 - 3 - 7 - 2

Notice for the flat plane the opposing banks fire in order: R - L - R - L - R -L - R - L. But on the cross plane it is: R - L - R - L - L - R - L - R ( - R - L). So for each 720' on the cross plane two cylinders on the left bank fire successively and two cylinders on the right bank fire successively. This is what gives the cross plane its burbling sound.

Ironically, although it sounds cool it further hinders the cross plane's power if you have a simple exhaust header on each side which combines all the exhaust outlets from that bank. If the engine is NA you can't tune the sound waves in the exhaust header to achieve maximum exhaust gas scavaging, because of the uneven flow of exhaust gases. Likewise if it's a turbo you don't get a steady flow of exhaust gases to each turbo. A few crossplane V8s (e.g. the GT40) got round this with a H shaped twin exhaust header with one cylinder from the left bank running over to combine with three cylinders from the right bank and vice versa but such a system is heavier and bulky (and you lose the burble).

The sound of the Esprit V8 kind of lost out on both fronts. It didn't have the burble of a crossplane, and because of the dampening from the turbos didn't have the whail of a NA Ferrari flat plane V8. But if you lose the cats and exhaust it does have the hell and thunder rasp of the F40 - which was also a turboed flat plane V8!

Edited August 2, 2008 by neal

[Günter]

Neal, PERFECT ! What i meant with 'equal firing' comes out much better in your explanation

I'm not an perfect 'teaching type' of guy to explain thing so clear. .. . For me it's that situation that i work every day with it , and do the things instinctive , especially as I'm a bit blind taught that all around me know the basics.

Anyway, for us over here the limitations in things like cat/decat and 'sound of thunder' makes it nearly impossible to imitate an real race like sound. Especially as the police does stop cars in traffic and inspects all noticeable changes from stock conditions... . You can't be so "creative" as in GB or overseas!

PS. An mechanic in the garage counts the cylinders every time from the belt side -

1234

5678

it means you can try 16354728 or 18364527 for flat plane firing ,right ?

Edited August 2, 2008 by G

[act2007]

Here is another clip:

http://www.speedandmotion.com/pages/videos/ccesprits.html

Alan

[Stuart]

John,

I had both the standard Cats and Lotus sport exhaust to start with. I then changed to the Larini exhaust. This in fact was quieter than the Lotus unit at idle and lower revs. When driving and the revs start to climb, about 3500 and above then the Larini really comes on song. In short it was less annoying than the Lotus unit for me when puttering around town and easy driving, but when you put your foot down then it sounds much better, not louder but more rich if that makes sence.

I have now the Hi Flow Cats as supplied by SuperDave (many thanks Dave) These Cats together with the Larini exhaust are much better, the throttle responce is a little quicker. As for the sound this is improved considerably. Still at low revs the exhaust is reasonably quiet for the type of car it is fitted to, but when you put your foot down then it truly sings.

I recently ran down to southern Spain through France in the car and when the entire exhaust and Cat setup was hot then the sound is much improved. Going through tunnels high revving in third it sounds fabulous.

Hope this helps, sadly my video camera packed up so I couldn't get any footage.

Stuart.

One thing of note is that I have had some cracking on the exhaust system. This I'm putting down to the rubber mounts being much tighter on the Larini muffler than on the Lotus exhaust. So there is not so much movement. There are other threads that have covered this so I'm not too surprised.

[Iconic Ride]

Thank you Neal and Gunter for explaining yet another one of "life's great mysteries" for me. 1 down, 1,378,294 to go. So if I want the "burble", all I have to do is rearrange some plug wires, right? (no, John, that's not how it works)

Thanks, Stuart, for your input as well. Sounds like there IS something to be gained by installing the Larini box alone---and more still by adding the high flow cats.

Alan had sent me his "link" by PM earlier, but I'll thank him again for providing a very pleasing display of Loti to the rest of the forum.

John

[Günter]

John, just use an angle grinder and an welding machine. With that you can create your very own special exhaust sound. And you can still use the standard box (in case some local policeman want to see an legal-manufacturer badge on it...)

PS. I've gone the other way to save my road certification (added several kilograms of heat insulation stone-wool ...)

[jfitz981]

Hey John,

If you can find a stebro exhaust, they have a great sound! Loud but not overwhelming. Under 3K it is not overbearing over 3k it screams (in a good sense). I dont have cats either and that enhances the sound even more plus my car shoots flames and that is incredibly cool.

Have a good one!

[th4neuk]

I have a federal centre exit exhaust on mine and love the sound. However I now have sports cats on and it now sounds as good as it gets. I think the V8 is too harsh with no cats (the silencer is fake!!) but you get an evil noise now and I love. Kills your fuel consumption though cos the noise is so good you are always tempted to make a bit more lol

[Iconic Ride]

I have a federal centre exit exhaust on mine and love the sound. However I now have sports cats on and it now sounds as good as it gets. I think the V8 is too harsh with no cats (the silencer is fake!!) but you get an evil noise now and I love. Kills your fuel consumption though cos the noise is so good you are always tempted to make a bit more lol

Hi, Alan.

I may have been adding some confusion to the issue by misuse of nomenclature. Does Lotus offer the "sport cats" AND the "sport box" (silencer) as independent items, or is it an "all or nothing" system? I am assuming that what they offer is available for EITHER the center or side exit systems, yes, no?

It appears that EVERYone with the center exits is a "happy camper". I will be dealing with my existing side exits for the indefinite future, so all my "tone" questions pertain to that setup. Thank you for your input nonetheless.

Regards,

John

Hey John,

If you can find a stebro exhaust, they have a great sound! Loud but not overwhelming. Under 3K it is not overbearing over 3k it screams (in a good sense). I dont have cats either and that enhances the sound even more plus my car shoots flames and that is incredibly cool.

Have a good one!

Rightious "special effects", bro!

Does Philly not have emissions testing, or do you just like living on the edge, Jason?

(Or do the cats magically appear annually as necessary?)

Cheers,

John

[Günter]

I taught all official selled "sport cats" are high flow race cats (made in DIY with welded in flat/round type aftermarket cats [as seen last year in *superdavelotus* online shop illustration], or made by professionals all in all in polished stainless steel ->Larini)

The sports exhaust from Lotus is the one with the direct exhaust from LH bank to left side exit, on the other side in the same style. The standard is the one that i have (with the reflection blade in the middle of the camber) . And the center style is just an Design upgrade for the late US-type "last evolution" cars.... ???

[Iconic Ride]

[quote name='G

[Günter]

i think there must be an picture in the forum with that sport box in it. If I'm right - [Hilly ,or who else ?] had opened one to modify it for some reasons. And there was an real simple conception shown it (Anyway, the standard box isn't rally more interesting- only difference is that the inlet ports are open ended tubes and there is that reflection blade in the middle..)

[jfitz981]

Hey John,

In PA once you get the car inspected you are fine from year to year if you do not drive the car over 3K per year. So it is just getting the initial inspection passed then you are fine from there as you are exempt. See if your state has a law similar to that. So many guys especially the hot rodders do this often...find out where the hot rods go!

Good luck!

Jason

[th4neuk]

My sports cats came from Superdave and PNM. They certainly sound great and I will see how they get on in the upcoming MOT test.

The centre exit I think is the nicest sound as there is a small balance pipe between the 2 exits which alters the sound a little. The centre exit is the genuine Lotus one btw.

Not to bad to fit if your turbo nuts are ok. I need to have 3 new studs on the left turbo though and will get this sorted at the next service.

Cheers