SuzukiSavage.com - Evolution of a Hot Rod Part 3

DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #15 - 06/07/21 at 00:03:31 Braze it up.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #16 - 06/07/21 at 00:04:14 The 1.75” OD side of the adapter fits into the Harley muffler. The 1.75” ID side of the adapter goes over the header pipe. The adapter will be loose on the pipe. Make a sleeve to fill in the gap. Take a short section of 1.75” OD exhaust pipe and cut though it with a hack saw.
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DragBikeMike

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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #17 - 06/07/21 at 00:04:43

Slip the sleeve over the header pipe until it hits the shoulder. Position the cut in the sleeve facing down. Fill in the cut with silicone sealant. Permatex Ultra Grey can handle the heat. Then assemble the muffler and adapter onto the header pipe and sleeve. This shows the sleeve on the pipe with a bead of sealant in the cut, ready for assembly. The picture was taken from underneath the exhaust system.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #18 - 06/07/21 at 00:05:37 The muffler has a built-in mount slot. A 5/16” bolt fits in the slot.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #19 - 06/07/21 at 00:06:21 The bolt goes through one of the mount grommets in the muffler bracket. This shows what it looks like from underneath the muffler. A match made in heaven. It couldn’t be any easier.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #20 - 06/07/21 at 00:07:19 The finished installation looks OK. A little VHT paint will doll it up. It would be better with a nice heat shield, but for this test, I’m good to go.
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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #21 - 06/07/21 at 00:08:28

Let’s do a review of the current modifications before we start testing.

The airbox cover has been removed to supply more air to the engine. The stock air filter element is installed, and the carburetor has been rejetted. We have installed a #55 pilot jet and a #150 main jet. The slide needle has been raised .047” by replacing the .110” plastic spacer with a .063” plastic spacer. I refer to this needle position as +.05”, meaning it is .05” higher than the stock position.

We have replaced the stock muffler with the Dyna muffler. The stock header pipe has been retained.

Let’s fire it up.

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DragBikeMike

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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #22 - 06/07/21 at 00:10:57

I did a noise test with the NIOSH app. Noise levels at 1300/3000/4000 rpm are 61/74/78 dB. I was surprised. I thought it would increase more than 1 dB @ 4000 rpm. It sounds good, much better than stock. It has a nice low-frequency thump, and it’s quiet.

A few laps around the block felt good. It seemed to have more punch and the jetting was close. Time for test & tune.

Best performance was achieved with a 152.5 main jet and the slide needle raised an additional .033”. I will refer to the needle position as +.08, meaning it is .08” higher than the stock position. I raised the needle because it had a lean surge at high-speed cruise.

Acceleration tests showed a significant improvement.

Second Gear 4K to 7K: 3.70 seconds Improvement: 0.62 seconds

Third Gear 4K to 6.5K: 7.56 seconds Improvement: 0.48 seconds

Fifth Gear 3.5K to 5K: 6.91 seconds Improvement: 0.87 seconds

Fifth Gear 3.5K to 5.5K: 11.64 seconds Improvement: 1.98 seconds

Now, it will pull all the way to 5800 rpm in fifth gear, where before, with just the airbox mods, it would not pull past 5700 rpm. The less restrictive muffler is helping a bit. The 5th gear pass simulation feels great. Most Savage owners would be satisfied with this level of performance.

Fuel mileage went down a bit. I averaged 53 mpg over several tanks of gas. Fuel economy dropped 2 mpg. That’s fine with me. The improvement in performance is worth 2 mpg. Chalk one up for the +.08” needle position.

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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #23 - 06/07/21 at 00:12:58

We now have a vastly improved induction system and a moderately improved exhaust system. The modifications are simple and inexpensive. Everything that has been modified can be restored to the stock condition. No internal engine work has been performed.

What happens if we amp up the exhaust flow a little bit. Let’s see if that crazy exhaust fitting works. The one I posted back in 2019. That would be this old post.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1554878768

The special fitting mockup was good for about 4% more flow on the test bench. I had never tried it on the motorcycle. Now was a good time to test one.

A chunk of scrap tubing and a 1.25” washer.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #24 - 06/07/21 at 00:13:38 Hack away and braze one together.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #25 - 06/07/21 at 00:14:14 Fit the pipe just right.
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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #26 - 06/07/21 at 00:14:49 And it fit the port too.
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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #27 - 06/07/21 at 00:15:14

After a full day of test & tune it was evident that my brilliant exhaust fitting was a dismal failure. It ran fine. You really couldn’t tell much difference seat-o-da-pants. But the stopwatch always tells the real story. It was measurably slower, not a lot but slower is slower. It’s a flop. I will update that old post to let folks know it doesn’t work. If any of you try it and have better results, by all means tell us your story.

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DragBikeMike Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 4210 Honolulu	Re: Evolution of a Hot Rod Part 3 - Exhaust System Reply #28 - 06/07/21 at 00:15:59 How about a better muffler, one that is way less restrictive? A quick trip to the auto parts store for a 2”OD x 1.75” ID adapter, a little work with the hack saw and map gas torch, and voila, we have a new high-flow muffler hangin off the stock header pipe.
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Re: Evolution of a Hot Rod Part 3 - Exhaust System
Reply #29 - 06/07/21 at 00:17:50

The LCGP muffler flows a lot better than the Dyna muffler. It pulled a meager 31.5 inches H2O on the trusty two-shopvac test bench. You can find the details on the LCGP muffler in this old post.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1609379913

Can the modified induction system keep up with this hi-flow beauty?

I did a noise test with the NIOSH app. Noise levels at 1300/3000/4000 rpm are 64/77/79 dB. It’s about 3 dB louder than the Dyna at low rpm, but only 1 dB louder at 4000 rpm. Certainly acceptable. It sounds good, much better than stock, a little better than the Dyna. It has a cool low-frequency thump, and it’s reasonably quiet.

A few laps around the block felt OK. It was rideable but seemed a bit on the lean side. Time for test & tune.

Best performance was achieved with a 152.5 main jet and a compound slide needle still at +.08. You really can’t raise the slide needle more than .08” because you get to the point where it will exit the needle jet at WOT. I have run it at +.12 but it’s erratic, you can’t repeat test results. I was able to eliminate the lean condition by sanding a compound taper into the needle. It works OK. This shows the details on the taper.

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