Performance: Gronk's Mod vs. Screaming Eagles

[sportysrock]

Originally Posted by gronk62

Different noise regs here in OZ means slightly different baffles.

I assume you mean punching out the plug down the centre of the baffle.
A few people have tried this and run into tuning problems.
Something to do with "reversion"

I also tried this back in 96 and I thought they sounded weird.

My 2004 stockers have 14 rows and 7 rows of holes. The plug is in the middle where the weld bead is located. I think punching the plug out changes the geometry and causes or can cause reversion issues. Your mod keeps the length basically the same which seems like a good idea.

I was wondering today about doing this mod on several sets of muffs and seeing what the best drill size would be for streetable power. That would be cool to do if someone had access to a dyno.

Ok, I'm a computer geek and can't help wondering about stuff like that.

[iBloke]

Originally Posted by sportysrock

I was wondering today about doing this mod on several sets of muffs and seeing what the best drill size would be for streetable power. That would be cool to do if someone had access to a dyno..

That would be cool.

I'd be interested to know what performance differences there are between stock and gronk modded muffs.

[HacksawsGarage]

am i to assume grunk mods have NOT been done on tapered muffs? like standard equipment pre 2004 sportsters?

i have an set of NOS black harley mufflers. i want to run them on what is now black chromed straight pipes. i like loud motorcycles, however i dont like tickets. what i want to do, is modify the stockers to look stock, be a little quiter than straights, but still have some bark when the throttle is cracked. wont ride a bike that wont bark.

i am thinking some kid of modified gronk would do the trick, if i knew what was inside of the old standby stock tapered muffs. i would also like to lighten them. are they filed with wool or some other fiber junk??

[iBloke]

Originally Posted by HacksawsGarage

am i to assume gronk mods have NOT been done on tapered muffs? like standard equipment pre 2004 sportsters?

I first did the gronk mod on the stock tapered mufflers on my 96 Sporty.
Tapered mufflers on Sporties go waaay back and are still standard equipment on the new models.

Originally Posted by HacksawsGarage

i have an set of NOS black harley mufflers. i want to run them on what is now black chromed straight pipes. i like loud motorcycles, however i dont like tickets. what i want to do, is modify the stockers to look stock, be a little quiter than straights, but still have some bark when the throttle is cracked. wont ride a bike that wont bark.

Maybe the gronk mod is not for you. They do not "bark".
One of the main reasons for the gronk mod is to keep the sound level to a socialy acceptable level whilst still having a reasonably full sound. Unlike the chuff chuff noise of the unmodded stockers.

Originally Posted by HacksawsGarage

i am thinking some kid of modified gronk would do the trick, if i knew what was inside of the old standby stock tapered muffs. i would also like to lighten them. are they filed with wool or some other fiber junk??

There is some fibre packing inside the stockers which is held against the inside of the main muffler body by perforated tube.
I doubt removing this would save much weight.

Follow my instructions for the gronk mod and you will be able to see inside for yourself how they are built.

[Don Burton]

Originally Posted by gronk62

Different noise regs here in OZ means slightly different baffles.



I assume you mean punching out the plug down the centre of the baffle.
A few people have tried this and run into tuning problems.
Something to do with "reversion"

I also tried this back in 96 and I thought they sounded weird.

I like Phil's "Gronk Mod" ideas. I would not "punch out" the center baffle plate as it should be cut out if it is to be removed. Unless I had ten sets of mufflers to try, I wouldn't cut it out at all as, without testing, I would worry about possible reversion and tuning problems. My neighbor did that to his 05 1200C and they sounded weird as well, so now he has a set of stockers that he can't use. I suspect that a small hole drilled through the middle of the center baffle plate (in addition to the Gronk Mod) probably wouldn't hurt too much but I'd stay small. In fact, I wouldn't bother for myself. I ride like Phil says he does so absolute maximum performance isn't an issue with me. If it was, I'd try some other set up. With that being said, if one drills enough larger holes in the side of the tubes, I think that one can get better performance with Phil's mod. Frankly, I'll take a little more performance but more importantly, I like a little more noise for safety reasons. I don't want it to bark as loud as the Cycle Shacks do when I'm just tooling around. Why offend people or ruin my hearing? I do want an obstructive baffle in there just in case some "local yokel" pulls me over and wants to shove a stick up there to check.

[barkster99]

I posted something in the Exhaust section about this, will add it here too.

I ran did the whole stage 1 thing with SEIIs and decided it was just too loud. Did Gronk's Mod and love it. The stage 1 - whether with SEIIs or Gronk's - has made a nice difference in just plain rideability. Perhaps a couple ft/lbs of torque were lost when switching from SEIIs to Gronk's though you sure couldn't prove it by me. I can't tell a difference.

I see someone's posted some dyno results with Gronk's Mod's in the dyno section. I'm not smart enough to know how to read them and there's still not a direct comparison to SEIIs or other aftermarket mufflers.

If you're considering doing Gronk's and want some more comments about the process you can check out my post in Exhaust section for more detail. Gronk's my new hero.

Hey Gronk? How's it feel to have a mod named after you? Has anyone started selling "Gronk's Mod Mufflers" on ebay yet? It won't be long. Better get that patent complete. Seriously, I think the interest in quiet, free-flowing exhaust is only going to increase. There's a great market there. Hey Gronk, want to go into business? I'll be your North American distributor/promoter. In a few years someone will be rich off this and we'll all be going "Damn! I should have done that."

[iBloke]

Originally Posted by barkster99

Has anyone started selling "Gronk's Mod Mufflers" on ebay yet? It won't be long. Better get that patent complete. Seriously, I think the interest in quiet, free-flowing exhaust is only going to increase. There's a great market there. Hey Gronk, want to go into business? I'll be your North American distributor/promoter. In a few years someone will be rich off this and we'll all be going "Damn! I should have done that."

I kinda wish someone would start selling mufflers that filled the gap between stock and LOUD.
There's obviously a market for them.

I ain't interested in goin' into business though. Someone else can have that headache

I'm glad you're happy with the end results. I've had mine on for about 15 months and I dig 'em.

[bmonty72]

i just checked, no gronks on Ebay yet... I plan on keeping my original mufflers stock (just in case, i don't know why). I have a set off stock mufflers with the baffle plug punched out, and I was planning on trying this...
http://xlforum.net/forums/s...ad.php?t=30198

Couple of ??'s

Should I use 1 1/2" or 1 3/4" exhaust pipe?
Do i still need a baffle plug? Or will the cut and press section restrict enough?
4 Columns of 8 holes, or 8 columns of 6-7 holes?
How much flare on the end of pipe to hold in muffler?
All help will be GREATLY appreciater.

1 more ? How much difference between K&N Filter in the Ham Can and a complete stage 1 intake such as the hurricane or ramflo. And has anyone tried the Kuryakyn Hi-5 AC?


I'm outta breath now...

[iBloke]

Originally Posted by bmonty72

Should I use 1 1/2" or 1 3/4" exhaust pipe?

If it was me I'd use 1 1/2" ..but why not try both.

Originally Posted by bmonty72

Do i still need a baffle plug? Or will the cut and press section restrict enough?

The cut and press section is the same as used in SE II's. No baffle plug needed...unless you want one.

Originally Posted by bmonty72

4 Columns of 8 holes, or 8 columns of 6-7 holes?

I don't think it matters. Try it and see.

Originally Posted by bmonty72

How much flare on the end of pipe to hold in muffler?

Enough to make it fit snug. Then just use a cuppla short beads of weld to hold it in.

[bmonty72]

Now, do you know what difference it would make it I were to meve the columns of holes closer to or farther from the end of the exhaust pipe? I assume closer would give you more of a bark since the gas is actually coming out there, and farther away would make it deeper because it has time to resonate in the pipe???