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2011 Evora NA 6MT
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Discussion Starter · #1 · (Edited)
One of the first things I noticed once purchasing my car last month, is that the exhaust is very quiet.

The previous owner mentioned it had the optional Sport valved titanium exhaust but once I started to peel back the covers, it turned out my car had a base model non-valved steel system.

First thought was to de-cat the system to save a little weight and perhaps that would be enough. I went ahead and ordered the factory decat tube from gatormotorsport and as soon as it arrived, I set out to do the installation. Removing the factory muffler and 3rd cat was pretty straightforward, so I expected the decat pipe install to be simple as well. I was wrong. Turns out, the de-cat pipe I received has the mounting flange mounted at an angle that will not orient the pipe in the same way that the 3rd cat sits on the car.

All chances of a bolt in job were now out the window. That led me to review other options that are readily marketed for the Evora NA. I started with looking into a Plack exhaust. After hearing the system on youtube vids, I wasn't sure if it was going to be too loud for my taste, so I mounted up the new decat pipe I had just bought.
Too much.
I can see how folks with a track car can get along with it, but the DB level, the raspiness, and the drone left me thinking this sound is better suited to a flathead Ford V8 than a supercar sounding DOHC V6 motor.

So, this means Plack was out. As well as the Top Speed system I saw which would require me to keep my 3rd cat (since I did not have a workable de-cat pipe). Also, to bring up another point, the stock muffler and 3rd cat turned out to be heavy. It weighed 44.75 lbs on my hanging scale.

So when you gotta have what isn't out there, you then make your own, right? So, I cut the decat pipe so it had a turnout, and drove my Plack style muffler-less car to a local muffler shop whom I've used many times before. While there we tried out three different mufflers on the decat pipe to determine what sounded the best. He had some C5 corvette takeoff mufflers, a magnaflow muffler, and a flowmaster. Of the three, the flowmaster was the rowdiest, but in a good way. It also was the lightest, at 11 lbs for the muffler alone.

I decided on the flowmaster, P/N 842580. Basically a can with a few baffles. No fiberglass packing or mesh inside it anywhere. The closest thing to having a straight pipe, back pressure wise without making your ears bleed.

Once done, the car sounded exactly like what I was looking for - a badass exotic. The drive home was awesome, I could actually hear the exhaust now from inside the car. I also noticed that I there wasn't an rpm band that would cause NVH issues. No drone, no vibrations. Perfect.

Got home, removed the system, and weighed it on my hanging scale. 14.03 lbs. A weight savings of 30.72 lbs! I painted the new system with high heat black and buttoned everything back up. What a great day :)

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Nice work. Do you possibly have a sound clip?
 

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Cool packaging!

Have you thought about pulling the y-pipe out and running a dual path with two mufflers. I've seen a controlled test that shows it picks up 20-30 ft lbs (with or without headers) in the midrange with no power loss up top. It would be another 15-20 lbs heavier but likely worth it. I've been meaning to build one for months, but my car is in many many pieces because of the loss of the autocross season.

donour
 

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Illegal Alien
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Cool packaging!

Have you thought about pulling the y-pipe out and running a dual path with two mufflers. I've seen a controlled test that shows it picks up 20-30 ft lbs (with or without headers) in the midrange with no power loss up top. It would be another 15-20 lbs heavier but likely worth it. I've been meaning to build one for months, but my car is in many many pieces because of the loss of the autocross season.

donour
Please point to the data or source. None of the factory or private race teams have done this including those in Lotus Cup that use the stock engine save for cams, intake, exhaust and tuning.
 

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2011 Evora NA 6MT
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Discussion Starter · #7 · (Edited)
Cool packaging!

Have you thought about pulling the y-pipe out and running a dual path with two mufflers. I've seen a controlled test that shows it picks up 20-30 ft lbs (with or without headers) in the midrange with no power loss up top. It would be another 15-20 lbs heavier but likely worth it. I've been meaning to build one for months, but my car is in many many pieces because of the loss of the autocross season.

donour
I don't think the smog gods in California would appreciate the CEL I'd have if I removed the pre cats. I can get away with the third cat because it doesn't throw any codes due to the secondary O2 sensor location previous to the 3rd cat.
 

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Please point to the data or source. None of the factory or private race teams have done this including those in Lotus Cup that use the stock engine save for cams, intake, exhaust and tuning.
It's pretty well documented by all the folks that do 2GR-FE swaps. Tests are all NA. Wilhelm did a bunch of dyno time when he was building his MR2 (2GR-FE Power Gains). This isn't really surprising given the architecture of the engine. If you change the valvetrain, the dynamics of the exhaust flow change and these boosts at 4500 RPM at not important.

I think we need to try it!

donour
 

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Discussion Starter · #10 · (Edited)
It's pretty well documented by all the folks that do 2GR-FE swaps. Tests are all NA. Wilhelm did a bunch of dyno time when he was building his MR2 (2GR-FE Power Gains). This isn't really surprising given the architecture of the engine. If you change the valvetrain, the dynamics of the exhaust flow change and these boosts at 4500 RPM at not important.

I think we need to try it!

donour
Thanks for the link! I loved checking out what Wilhelm did with his 2GR-FE. I enjoyed digging into what they did on the induction side. The lower intake manifold porting and 17190-0P031 Toyota Venza intake manifold swap looks like it would be nice modification for us NA Evora owners.
 

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Illegal Alien
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Cool packaging!

Have you thought about pulling the y-pipe out and running a dual path with two mufflers. I've seen a controlled test that shows it picks up 20-30 ft lbs (with or without headers) in the midrange with no power loss up top. It would be another 15-20 lbs heavier but likely worth it. I've been meaning to build one for months, but my car is in many many pieces because of the loss of the autocross season.

donour
Thanks for the MR2 link. I see that the twin pipes (w/ Xover) gains its power below 4500 rpm while the y-pipe retains the lead above to 6500 and even from there up.. Tester left in teh X pipe system as in total their is more power under the curve. However the way I drive my Evora on track (and I don't think i'm the only one) is I use under 4500 rpm once and that is to get going, from them i'm shifting in 5 to 7 k band, so power curve importance is 4500 to 7200 rpm.
 
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1991 MR2, 2GR-FE V6 Swapped
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Thanks for the MR2 link. I see that the twin pipes (w/ Xover) gains its power below 4500 rpm while the y-pipe retains the lead above to 6500 and even from there up.. Tester left in teh X pipe system as in total their is more power under the curve. However the way I drive my Evora on track (and I don't think i'm the only one) is I use under 4500 rpm once and that is to get going, from them i'm shifting in 5 to 7 k band, so power curve importance is 4500 to 7200 rpm.
Hi Julian,
I'm Alex from Wilhelm Raceworks. I just joined to comment on another thread, and then found a few other places where people here had linked to my site so I figured I would jump in.

The test where the y-pipe beat the x-pipe in the top end was a bit of an odd one in that it only did that after I re-installed the cat, muffler, and Helmholtz resonator. Open y-pipe vs x-pipe exhaust was much closer, with the x-pipe pulling away again after 6500 RPM. In previous tests I saw no difference in power between an open y-pipe and a y-pipe with straight through mufflers, and it doesn't seem to be the catalytic converter adding 5hp, so my only theory is that it's the Helmholtz resonator. Without that there doesn't seem to be much difference between the x-pipe and y-pipe in the 5000-6500 range, and outside of that range on both sides the x-pipe makes more power.

That said, it's not MUCH more power above 6500, and if the y-pipe is substantially easier, cheaper, or lighter weight it's probably not worth going to the x-pipe if you are mostly in that 4500+ range.
 
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