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A little further along. Squared everything up, and went to bolt the flanges together with 1/4-20 bolts and realized I tapped the flange for 6mm. So, chased the threads with the correct tap and mocked it back up. Went ahead and welded the flange to the neck pipe. Oddly enough my Ryobi belt sander's top drum has the correct diameter to radius the mouth nicely. Once tacked in place I'll loosen the bolts enough to keep weld spalls from sticking to either thread. PITA to clean them up...
Then mocked the neck to the main tubes and thought I'd get a lot better aligned hole drilled if I went ahead and tacked the neck flange to the main. So now I'm going to space the neck pipe flanges apart the thickness of the main pipe because I wanted the neck to have a good transition into the main. Wouldn't have needed to if I hadn't welded the neck flange already. Kind of a PITA but a good reminder of why we need to think a couple steps ahead. I'll also bore the holes in the boxes before finalizing the pipe fitment. I'll need to leave at least a small gap between the boxes to get the pipes out.
As a side note I've picked up @ 1.5 mpg running the OEM box. I don't think it's more efficient so much as quieter so I'm not pressing the go pedal as far as often as before...
Yep, sure of it. I'm going to do 'something' at the back, just not sure what. I'm a little concerned about the rigidity of the chamber with the thin stainless walls. The round tube in the back was supposed to be temporary. I never added the final brace across the back.
Well, after some suffering and pain the dang thing is in. Getting the stock box back off absolutely sucked. Dang nubs on the hangers would not let go. Once done fighting that, forgot how heavy the stock box was as it fell on me. Then someone forgot about the tow hook and one of the resonators hit it hard. Lopped off an inch and it hit the inside muffler. Birds mouthed it and got it to fit. Fired the car up and is sounded like someone installed some steel pan drums under the car right off idle. Gawd awful sounding things. I actually LOL'd it sounded so bad. So, back off with the resonators, drilled them for some 8mm stainless all thread I had laying in the corner and welded two pieces per resonator. No more Caribbean racket from out back.
Took the car for a spin. Exhaust sounded pretty good, like it was before just more subdued. Hit the interstate and damned if the exhaust wasn't quiet enough to hear snapped fingers at speed. I didn't feel compelled to turn the radio up to hear it and the car just motored along fine. Stopped by the river and took a short walk to clean out some of the welding smoke from my lungs. Took a couple pics of the car.
Sunny bright green.
Shady dark green.
It's funny, but once the exhaust was warmed up it sounded a lot better neutral revving it. Pretty cool and I'm happy with the results. Not the same sound as the stock box and I will make something that sounds like an F type down the road. Overall great engineering exercise and thankfully it actually worked.
It's funny, but once the exhaust was warmed up it sounded a lot better neutral revving it. Pretty cool and I'm happy with the results. Not the same sound as the stock box and I will make something that sounds like an F type down the road. Overall great engineering exercise and thankfully it actually worked.
Well, after some suffering and pain the dang thing is in. Getting the stock box back off absolutely sucked. Dang nubs on the hangers would not let go. Once done fighting that, forgot how heavy the stock box was as it fell on me. Then someone forgot about the tow hook and one of the resonators hit it hard. Lopped off an inch and it hit the inside muffler. Birds mouthed it and got it to fit. Fired the car up and is sounded like someone installed some steel pan drums under the car right off idle. Gawd awful sounding things. I actually LOL'd it sounded so bad. So, back off with the resonators, drilled them for some 8mm stainless all thread I had laying in the corner and welded two pieces per resonator. No more Caribbean racket from out back.
Took the car for a spin. Exhaust sounded pretty good, like it was before just more subdued. Hit the interstate and damned if the exhaust wasn't quiet enough to hear snapped fingers at speed. I didn't feel compelled to turn the radio up to hear it and the car just motored along fine. Stopped by the river and took a short walk to clean out some of the welding smoke from my lungs. Took a couple pics of the car.
Sunny bright green.
Shady dark green.
It's funny, but once the exhaust was warmed up it sounded a lot better neutral revving it. Pretty cool and I'm happy with the results. Not the same sound as the stock box and I will make something that sounds like an F type down the road. Overall great engineering exercise and thankfully it actually worked.
That is great news!
I have found an OEM XKR exhaust which I probably will buy and when it's on the car I might try something on the loud exhaust.:-)
Can anyone do the math for me cause I find it difficult to understand how to calculate all the values and get a number that says how big my helmholtz resonators should be!?
Ranchero50,
Your perseverance is astounding, and is what I find the most compelling part of all of your enjoyable posts. You are not willing to be just "satisfied," your modifications have to meet your expectations. BRAVO!!!!!
Thanks guys. Honestly I do it because I love learning about stuff. If you think about it, the exhaust is like a musical instrument so it needs tuned to make the sounds you like and also tuned to eliminate the noises you don't like.
Peter, take note of the RPM that your exhaust drones the most at. Divide that number by 15 to get the resonant frequency in HZ. Plug that into the calculator along with @ 100`C for the temperature so the calculator can figure the speed of sound at the operating temp. With those data points you can figure out the neck area by measuring the pipe you plan to build it from (3.14*r*r) and play with the neck length to get the chamber volume that will fit in your space.
I ran my car today and confirmed something I noticed after yesterdays test drive. The exhaust tone changes as it warms up. The free rev note is pretty wimpy when cold and very aggressive when warmed up. I also noted that I still have some drone around 2k but not nearly as bad as it was before. The resonator made the car remarkably quiet from 1500 up to 2700 or so. That's a huge frequency span (100 - 180 hz) and not something I expected. I suspect it's because the shortened resonator is working at a higher frequency (I think it calculated out to 160 hz). I have a tonal shift at 3k where the main pipe resonators warble. So the whole span of cruising RPM has the exhaust tone attenuated. I took a short video on the way to work but haven't had a chance to listen to it. I'll try to get it posted up and maybe do an honest walk around one 'soon'.
Uploaded a short video of the car post drone. Funny thing is you can't hear it running in comparison to my voice talking at a normal level. Blame it on the GoPro or the Helmholtz resonators are working that well?
So, after a week of not doing anything today I might tackle the rear wheel bearings. The alley is finally opened back up so at least it'll be in the garage vs. the street.
Got everything broken loose without much grief out back. Now the half shaft absolutely does not want to let go of the hub. I sprayed the bejesus out of the fit and pressed until I fear the hub puller will break and nothing. I'm going to let it sit under pressure overnight and see what happens in the morning. Hopefully it'll pop off on it's own. If not, torch time...
09-07-2017, 09:27 AM
Moving forward?
Oh blessed relief.
sort like a growl.
