LocostUSA.com

Thanks for the tip MV8. I think I will run a bead of weld along the top of the upright bracket to the 1/4" tab that had been intended for the UCA attach point and leave the thru bolt as configured. That should be very rigid.

Spring is finally here, and as many of you may have noted, we returned from our Wisconsin COVID hideaway to the Boston suburbs for my wife's work (she had been able to work remotely) where the Locost is. So, I have been back at work on the car.

I am now working on the exhaust. I went back over Nick47's web site and saw his progress over time with the exhaust changes.

My questions to are which muffler choice to make.

When I acquired MGB the motor from my friend, he also included an almost new exhaust system with a header pipe, resonator and stainless muffler. It had been an aftermarket system purchased thru Moss Motor. The resonator is a small, long bullet style unit. The muffler is a large round can with a polished stainless case.

I had thought about installing the resonator on the side next to the body, like yours. Then trying to sneak the 1 3/4" tube under the frame at the wheel arch and place the stainless muffler across the back under the rear of the car. This would reduce the size of the muffler hanging on the side and move a lot of the exhaust noise to the rear of the car.


Some of the original Caterham 7s had this config.



Caterham had the large muffler at the side and a resonator in the rear.

But, as the photo shows, the ground clearance gets very close where the tailpipe tucks under the frame close to the inside of the tire.

My other two choices are:
1. Use the stainless muffler as I show in the earlier mockup post, mounted to the side and use a 90-degree exit just before the rear tire.


2. Use the smaller resonator muffler on the side and use a 90-degree exit just before the rear tire.


As Moss motors described the exhaust system back when, the resonator reduced the high tones, and the muffler reduced the low tones. So, as a system it would give a mellow tone on acceleration and cruising. Using just one or the other will change the overall effect.

The last photo shows the muffler across the back. It will tuck up a little tighter into the back than shown.

Would love some feedback here from the group!

_________________
Thom

I'd shorten the primaries to bring the collector as far forward as possible. If the resonator/glass pack is short enough, weld directly to the muffler and collector. If it is too long, glass packs are cheap and come in many ods and lengths.
If the muffler has an offset outlet, I'd make sure it is toward the ground, then add a mandrel bend to go under the LCAP and kick inboard as needed for droop clearance, then straight back or diagonal toward the pax side rear corner. Run a little more ground clearance if needed. The tight spot for gc will be the LCAP wrap.

If it is too loud, you can buy or make an insert for the tail pipe or you can use a walker quiet flow for an oem app then wrap it in a stainless cover to be pretty. Use summit to find the largest od round muffler and longest length that will fit and have ends no greater than 2 inch so the internal dims will work well with your displacement. Lots of options.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Thom,

I really like the idea you have of putting the muffler on the side and the resonator across the back of the car.

In a crude way, I've relocated the side parts (collector and muffler) in the reworked photo below to position #1. As MV8 suggested, put the collector as far forward as possible. I'd attach the muffler as close to the collector as I could. So, all that would remain in the area I labeled as #2 would be exhaust pipe and likely a heat shield so a person's leg wouldn't contact the pipe on entry or exit.


When you go under the chassis, it will have to run outboard of the control arms, and inboard of the brakes, etc. Maybe tucking it under the chassis just before the seatback area would do? Since the pipe underneath the chassis will be largely protected by the height of the wheel and tire, you should be OK.

The only big issue I see would be the possibility of the rear axle contacting the pipe at full droop. You'd have to make sure that couldn't happen by either making sure the coilover wouldn't allow the axle drop that far, or maybe a limiting strap on the axle.

I think having both the muffler and resonator plus exhaust exit at the rear would be very helpful in terms of enjoying the car.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

A small locating pin through the flange will do the trick. I used a sheet metal screw (#6 I think). No problems after 10 years/60K miles.

If you decide to mix and match for fit or noise, these are good mufflers and resonators.

Wlk-21028 '60s chevy trucks v8s and L6s.
Wlk-18199, 21949, volvo models 240 and 142, 2.0-2.3L4, 74-93.
WLK-18553, 18251, ford Aerostar 2.3L4 and v6.
WLK-22483, 90s toyota pickup. Same muffler I have on the GO4 Interceptor with a mazda sohc 1.3L4 (B3) and a couple feet of pipe to the rear bumper. I thought it was a bit too loud and made a copper insert to quiet it down.
I think the quietest will be the volvo (slightly smaller pipes) quiet flow 21949 but all will get louder with use since I expect all have some packing that will settle.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

@MV8

Man, I love those prices.

They've labeled all as mufflers, and none as resonators. Do you think of the glass packs as resonators?

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Definitely. Good AND cheap

Generally not pretty though. A couple tabs welded on to hold a stainless cover is a given for the mufflers.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

A single muffler, no matter how big, will be loud. I started with a 15” x 4” D Walker muffler, lived with it for a few years, then bought a 24” . It’s loud but tolerable.

I have a friend with a Birkin that had the exhaust routed out the back. It was nice and sporty, a lot quieter than mine, but he eventually ditched it because of clearance issues in certain situations. He now has a single muffler with the exit ahead of the rear wheel. It’s still quieter than my car. Go figure.

One thing I would probably do differently next time is use smaller pipes. 1-1/2” or maybe 1.625. Car sounds a little too deep right now, rumbly rather than sporty. But who knows. It’s all kind of trial and error.

I looked at your suggestion. Thought it might work, but the muffler and collector were too long to make the fit. Too bad!

MV8- great suggestions and great pricing!

Nick- I think you answered my concern about just a "glass pack" style muffler or resonator. I think I will try the muffler that I have. It is a slip joint so it will be easy to sway out if too loud.

_________________
Thom

I agree with Nick47 100%
Just fabricating a rear exiting tail pipe will reduce the noise level. If building a rear exit exhaust system, the turn under the floor will be the most difficult part of the fabrication. Because a tight turn is restrictive, I elected to increase the exhaust tubing in the tight turn area by ¼” in size. For the turn, use a “U” formed tube. You need to basically cut the “U” in the center with the first half turn down and the second half at a 90* under the floor. Your commercial exhaust bend will probably be too large of a radius. I made a “Y” cut in the inside radius of the tube and welded upper cut edges together and the fill the lower gap with the “V” section from the original “Y” cut to tighten the turn under the floor. I also flatten the tubing into an oval to increase the clearance to both the floor and ground. Just putting on a rear exhaust exit dumps the noise behind you which has the effect of reducing the noise level 2 or 3 db’s. My second muffler is a short 10” motorcycle glass-pack welded to the end of the tail pipe. I tip the end of the exhaust system with a short bend turn to a 45* angle and trimmed at a tangent to the ground. The rear third of the exhaust system is suspended by a coiled tension spring attached to the rear side rail frame tube. I also put a heat shield between the rear muffler and the gas tank.

I continue to "test fit" items to make sure the "whole" of the car pieces as designed work together before I blow it apart to finish weld and paint. I still marvel at how the chrome moly frame does not show any signs of corrosion and the TIG welds of the frame builder are so excellently done! However, the mild steel I used for the floor and footwells are starting to show a slight bit of corrosion. Will definitely have to paint it.

I covered the top of the center cover with a marine vinyl- turned out OK.





Had to fiddle a bit with the 1st rear fender centered on the wheel.


I had acquired a set of early style Bug Eyed Sprite rear taillights like the original Lotus 7s used. Due to the curve of the fender, it does not sit quite flat. There is about a 1/4" gap at each end. I may try to build it up with fiberglass. I have a quite a bit of glasswork to to on the nose. When the previous owner widened the nose, he ended up with a lot of cupping at the splice. I will have about 3/16" to fill and feather. So, I went online to view additional images. It turns out they used a rubber fitment that filled the gap- top & bottom. I looked on ebay in the UK and found a used set- $100 delivered! I will find a different solution, I'm cheap!

I re-mounted the rear spare tire mount. I used one of the rear tires which is larger than I will mount back there, but it still fit though close to the 3rd brake light.



All of you have given so many good suggestions on the exhaust that I am still mulling all of that over. That is one of the reasons I started bolting additional items to the frame, I needed to see where the exhaust would land and what clearances I have- where.

The RCI fuel tank is a 15 gallon unit. It pretty well fills up the back of the rear. I think there will not be space for any storage. So I may make a hard cover covered with the same marine vinyl. It will have fixed side covers at the roll bar location with a larger center section with a piano hinge just behind the headrests. Someone had suggested quite some time back to weld in a small trailer receiver for a rear mounted luggage rack. I may revisit that thought.

_________________
Thom

I'm assuming that's a plate mount at the lower left? I like that & may copy something similar when I get to that point.

_________________
1975 MG Midget
http://www.locostusa.com/forums/viewtopic.php?f=36&t=24382
13B Powered Rotus Geauxkart
http://www.locostusa.com/forums/viewtopic.php?f=35&t=20899

Looking good Thom.

Here's what I used for rear fender fitment to body on all my 7's.

_________________
Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle

Which rear fenders are you using, Thom? They look wide enough that they might work for my build.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

One cannot underestimate the noise level of a side exhaust, especially when on the side of either a driver or passenger. It is loud! So are the wind and tire noise level. There is little one can do with the last two. I measured 90+dBA of tire and wind noise alone doing 45-50 MPH, clutch in-engine idling. That was measured between the seats at head level. Osha limits are 90dBA for an 8hr workplace. NIOSH limits are 85 dBA. IMO, earplugs are a necessity regardless of where the exhaust exits.

FWIW noise measurements are logarithmic. A 3dBA increased is double the sound pressure. Pointing the exhaust tip pointed downwards is also not good as the noise does bounce off the hard pavement. Straight out is the quietest. Out the back helps a lot. even if it may be only a -3dBA improvement.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

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