Side Pipe SPL

[Machiavelli]

For those using the factory provided JBL side pipes, are they loud? I thought I heard (or read) they are a glasspack design which should attenuate somewhat. What's loud? Good question, 6am warm up in the driveway will wake up the neighbors? You can still hear the motor over the wind cruising at 70mph? Anyone have a good comparison in SPL that comes to mind?

[Richard Hudgins]

Machiavelli.

The JBL designed sidepipes as supplied in the past have the following characteristics:

Note this is Compression ratio based. There are other factors which increase sound pressure and I leave that research up to you.


9-1 Can cruise at 80 mph and still carry on a conversation at the top of your lungs.

10-1 Can cruise at 80 mph and not go completely deaf until one has covered 10 miles.

11-1 Can cruise at 20-80 mph and set off every alarm within 1500 meters as well as have bystanders throw various bits of fruit and vegetables at you as you go by.

12-1 Cannot attain any speed whatsoever or do anything if the engine is running without wearing earplugs or permanent hearing loss occurs.

Any compression ratio above the ones cataloged above just make your ears bleed no matter what you do. (Chicks dig this one for some reason.)


But these sound levels are what the customer base demanded and we responded as all good race car folks do.

Not sure what Larry is doing now.

Hopefully he has not pussied out on this design standard.

[Machiavelli]

Hi Richard,
Appreciate the feedback, I think I've been shunned by the others here. Don't blame 'em, nobody likes a smart ass lol. Looks like I'll experience hearing degradation after 5 miles @ 80, be a fly-by alarm tester for the paranoid and catch a tomato headshot now and then. Quite frankly, if Larry is getting in touch with his female side more often these days that's ok with me. By the way, I've started my mental exercise program for the roadster - I read myself to sleep with the below.
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Turn 1
Although it doesn't seem like much of a turn but is possibly the scariest. Since the approach to T1 is uphill and the turn itself is on the crest, this can leave the rear end light at high speed on fast cars with low downforce. For now just picture yourself winding out full throttle at 90-95 mph in 3rd or just having shifted to 4th and hitting 100-105 having just cleared the Start / Finish hitting a speed of 90-100 miles an hour as you approach the Andretti Hairpin. This is a full throttle corner that has poor approach visibility. That's the challenge. A 'chicken lift' rising over the hill means less pucker and a lot of lost time. With the lift your approach to Corner 2 is about 90-95 instead of 100-105 mph. My first visit to Laguna I lifted for about 30 consecutive laps before getting up the gumption to go full out. A big smile followed my 31st attempt. Exiting, you should be aiming for the #1 or #2 Brake Marker (BM) of Corner 2.

Turn 2: "The Andretti Hairpin" 190 deg left hand hairpin - 45mph 3rd gear or 2nd if challenged:
Corner 2 is the first corner you hit if you enter right after exiting the pits the way the Champ Cars do. Motorbikes use the FIA entrance which enters the track after corner 2. I've used both and prefer the FIA entrance for safety (this enters the track right *after* the hairpin. Single Apex Method (Novice): Usually when approaching this corner I'm aiming for the #2 or #1 Brake Marker (BM) and hard on the brakes at or just before #4. You need all of the braking you can get since you're going about 100-110mph if you have done Corner 1 correctly. You heel and toe downshift from 4 to 3 (or 2) but be sure to get speed down below 50 before releasing if in 2nd or you will have a big problem. The key (on the single apex approach) to this corner is remember to stay outside until at nearly halfway around the corner. By this time you should have come in from the right about 1/3 of the way. Remember to hit a late apex here since an apex too early is how my friend made his S2000 a sub-compact. Use all the track and the rumble strip to "track out". Come back in to the left slightly and straighten and THEN turn toward the BM 4. Get over left and then turn along the outside of the track. A slight right kink will force you to turn right slightly... brake in a straight line between 2 and 1 and turn at one. Stay in 3rd unless you are heavily challenged. Double Apex Method: If you are trying for higher times you might try the double apex approach to Corner 2. Use the same approach to the corner but instead of braking hard at brake marker (BM) 4 to BM 1 turn in to the corner on the left and brake late (BM2?) which takes you right at the apex to the outside of the hairpin. then turn in and hit the exact same apex at before.

Corner 3: right hander - 50-55mph 3rd gear or 2nd if challenged:
Corner 3 approach is as above and in 2nd or 3rd you hit a moderately late apex and track out. Turn in is BM 1 (this is the standard on this track) and use the rumble strip if necessary (this is optimal). You are now on the far left of the track... stay there going under the big tire. If you have entered T3 at the proper entry speed and hit your apex, you should gain good momentum to carry you through T4 and up to T5 where the uphill really begins.

Corner 4: right hander - 70mph 3rd gear:
Corner 4 is probably my favorite. Hard on the gas to BM 2. Punch the brakes for a spit second to slow slightly and turn in early... about 2/3 the way between BM 2 and 1 (like BM 1.3). Don't shift. You'll be on the power still in 3rd as you turn and hit a surprising EARLY apex. Weird, I know, but it works. You are going to take this very fast and will need to get 2 tires on the left hand rumble strip. This sets you up nicely for a sweeping kink with no name. I call it "the sweeping kink with no name". Run through this at full speed and if I'm getting the hang of the track I'll be shifting into 4th and hitting nearly 105 before hitting the brakes for 6.

Corner 5: left hander - 50-55mph 3rd gear:
The biggest challenge for me in Corner 5 is the inevitable downshift to 3rd. This is a pretty fast corner so getting the shift completed without upsetting the car is tricky. Other than that... textbook. Brake between 4 and 2 turn in at 1, moderately late apex and on the gas to the right outside of the track to set up for 6. Due to the slight kink prior to the bridge preceding the turn, T5 can be deceiving. Watch your markers and brake earlier than you think in order to exit this corner quickly and safely.

Corner 6: left hander - 70-75mph 3rd gear:
I love Corner 6 for its high speed and the cool little gutter on the apex (left side). You don't brake much in the approach... say BM 3 to 2. You will take this uphill lefthander VERY fast. Maybe 70-75mph. If you can hit a medium apex and get two tires in the "gutter" it will swing you nicely around the corner and zoom up the hill. The temptation in a well executed corner is to NOT track out. WRONG! Track out using the rumble on the right to set up perfectly for the uphill climb to the "little kink". By doing this you have just straightened the entire climb to Corner 7 and probably gone as quickly through Corner 6 as you can. T6 is another deceptive corner. You can enter this corner a little faster if you can nail it correctly.

"The Rahal Straight": This is a long uphill straight that actually has a little kink going up the hill that's hard to see on the map. The kink is a left hander - full throttle 3rd gear:
Here I'd like to describe an important feature of the track. There is a slight "little kink" in the track between corners 6 and 7. It is right after the bridge (or is it a sign?) and kinks to the left. You should aim for the spot one third to the right of the left side of the sign ( If this is the sign, aim for the asterisk |.....*..........| ) This will have you run OVER the rumble strip and completely straighten the kink. You will now be approaching Corner 7 perfectly.

Corner 7: right hander - 50-55mph 3rd gear:
When you are through the "little kink" as described above you will approach Corner 7. This is barely a corner at all but is super important as a setup for the Corkscrew. Just before Corner 7 the up hill approach steepens abruptly. There is typically a bunch of rubber laid down on the track here. The beginning of this rubber is my start braking mark. Nebulous I know but that's how I do it. The track attitude will level off at this kink, leading blindly right into the corkscrew (T8). The fastest times will require careful braking and bravery. As you crest this area of the track watch where your car is pointed as it may go light. I take this corner differently than I did the first time out at LS and now brake hard setting up for seven. Let off and turn long the outside (right side of the track and STAY to the right. i.e. do not track out. I then hit the accelerator a second and brake again for the Corkscrew.

Corner 8A & 8B: "the Corkscrew" left right "S" curve - 50mph then 60mph 3rd gear or 2nd through 8A and short shift to 3 on the "straight" part:
Here it is. What everyone is waiting for. Corners 8A and 8B are the Corkscrew. The key to the Corkscrew is to straighten between A and B. The natural inclination is to use an "S"... don't. Turn through Corner 8A with a moderately late apex and then straighten for a split second aiming for the oak... then turn to a medium to late apex on 8B and use all the track. Then aim for the last oak on the left to brake straight and set up for the dreaded Rainey. Careful modulation of the throttle will keep gravel in this famous turn from spinning your car. After the sharp downhill your suspension will load up allowing you to feed in the power prior to Rainey Curve (T9).

Corner 9: "The Rainey Curve" left hand sweeper - 65mph 3rd gear:
Pointing straight at the last oak get on the brakes for about 100 feet. Then let off and begin the turn. Easy does it on this corner carving out a long sweeper. Hit a VERY late apex on the Rainey and run off using all the track on the right to "track out".

Corner 10: right hander - 60-65mph 3rd gear:
Full bore on aiming at the BM#1 for corner 1 and hard brake between 3 and 2 using the BM#1 as the turn in point. hard on the gas here just before the apex. This is surprisingly high speed and you get a lot of room on the left to track out... but you need it.

Corner 11: 110 degree right hander - 35-40mph 2nd gear:
You only get a little while to accelerate because #11 is a b*tch. Brake hard between 4 and 1 and downshift to 2nd. Late apex on this corner OR ELSE! Track out to the right but geez watch out, that wall is made of concrete.

Start/Finish Straight: 2nd to 3rd to 4th 90-95 at the S/F line:
Stay right on the straight 'til about halfway down to the bridge. Then aim for the "AZ" in "MAZDA" This helps straighten out the kink and set up for Corner 1. Right at the bridge is where you'll hit about 90 and shift to 4th. I think next time I'm aiming for the "Z" to keep me more to the right for Corner 1; driving the kink down the middle and turning in to the left to straighten Corner 1 instead.
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Next week I go to Toys-R-Us and pick up a plastic car so I can actually go through the motions. Haven't figured out how I'm going to explain it to the wife yet, maybe just let it happen and see if she can figure it out. (If she leaves and comes back with diapers I'll speak up)

[SMOKNAC]

Well put Richard,
I usually where ear plugs when driving my car, and set off every alarm I drive by.
I’m known as the one with the loud car on the block. And Yes it will wake up your neighbors.
I haven’t been in a parking garage yet, but my friends tell me it’s a BLAST!! setting off alarms...

[Machiavelli]

I don't buy it, you guys are talking migraine every time you hop in the car Checklist: keys check, jacket check, gloves check, tylenol check, LET'S GO! I'll be hearing several tomorrow at the local Starbuck's gathering, I'm betting pipes with glass packs give a pleasant rumble not offensively loud. If you're running straight pipes, yeah that's loud - been there done that with a Harley.

[Machiavelli]

Welp, I heard 'em - who can recommend a good ear plug? Not obtrusive at idle, but let's face it - the neighbors WILL here me leave at 6am (unless they're blessed with a wife that snores like mine). But as with any fact finding mission I undertake, there is always a new question that arises. Ceramic coated aluminum vs.stainless steel? Big dollar difference there, but if stainless with internal baffling is a "good for a lifetime" proposition (like ERA thinks), then it becomes a trade study of cost & time to repack and/or replace vs. install and forget (except for the occasional polishing to remove yellowing or bluing). I did mention this to Larry some time ago, if I recall the conversation - there were other issues with stainless steel that didn't make spending the extra $$ a worth while consideration. I can go either way, but for the extra money stainless steel does need to last a real long time.

[Richard Hudgins]

Told you so..............

Stainless is a waste of time and money for the application. Aluminum cannot be used due to temperature.

Mild steel is the choice.

Ceramic coating lasts a very long time and is maintenance free in my experience with it.

The thing to pay attention to is the length of the actual muffler section. The longer you can make it the quieter it will be. (Relatively speaking of course.)

The cost of the sidepipes is actually quite low and I recommend one for road use and another for track use.

But per your post about Laguna you may wish to just have the street pipes as Laguna has a pretty low DB limit and race pipes might not make it past the noise cops.

[Machiavelli]

Thanks Richard, that's probably what Larry told me but I couldn't remember. Didn't know Laguna was touchy on noise, but makes sense, the race track is in a canyon so mountain echo must be a real problem. I'll ask Larry to go with the longer muffler if there is one.

[jdean]

Check with Eric at Classic Chambered mufflers. He has a variety of options on length and inside diameter....so you can decide the best mix of sound vs. power

[Machiavelli]

jdean,
Just went to their website and checked them out, sounds like a real good solution. The performance gains they have posted do seem high to me. Are you running these pipes, and if so what's your opinion of them? No mention of ceramic coating on their website, but I imagine a recommended last step. I'll give Eric a call and get some more info, thanks for the tip.

[vector1]

i have a few of the different designs on the jbl and here is my experience.

one set had the holes inside the muffler, another had the inverted fish scale look, there was a difference in sound with the holes being slightly louder, but not what i would call significant.

would be my opinion to use something with the largest internal diameter cause it's going to be loud no matter the design. also depends on where the outlets are pointed but be careful, if you point them down it can raise a pretty good dust cloud, to the side breaks the db level. both my engines are low compression and neither is terribly loud.

on one of mine i set the muffler up so it sits in a craddle with two springs holding it in, i can switch it out with a straight pipe by loosening the v-band clamp on the entry and removing the two springs, about a 10 minute ordeal.

sent you a pm also.

[Machiavelli]

victor1,
PM'd you back. I've been digging more into side pipes, have emails out to some of them. One looks interesting, cutting edge - but we'll see.

Richard/Larry,
Do you have a side pipe supplier you use that you can share with us, the parts list doesn't give specifics - just $470 a set.

[jdean]

Yes I had the original mufflers cut off the collectors and replaced them with mufflers from Classic Chambered. Better flow and not terribly loud as far as Cobras normally go. When hwy cruising the wind is more noisy than the pipes.

[Machiavelli]

jdean, good to know and thanks. What about a noticeable performance increase, they are touting some incredible numbers with their pipes.

[MaSnaka]

For what it's worth, I was really self concious about what my neighbors thought about my noise. Turns out they love it. Well atleast the guys do. I think they are living through me vicariously. I have left pretty early in the morning and just don't rev it it up too much and just as quietly as I can leave. Now the 20 year old a couple doors down from me has to rev up his 50's ford for 10 minutes before he can leave. That bothers me. Letting people hear a Cobra is a gift. I also have Eric's Classic Chambers and gained 70 HP over my stock exhaust.

John

[jdean]

Unfortunately I dont have any before and after numbers, and I made the change in the mufflers without even running the first set, which had a smaller diameter inside. But others have seen some significant improvements which is why I chose them in the first place. Changing them out is an easy 20 minute job for an experienced welder. Then you can have them coated however you wish.

[Machiavelli]

MaSnaka, you're probably right, if it sounds good and not too loud they may like it.

Larry, I'm damn close* to asking you to put pen to paper and come up with a maximum length we can go with. Want your chassis welder too, that's the guy for this job!

*Richard, would this be acceptable to you, I need engineering approval before I can proceed

[Machiavelli]

jdean, I'm pretty much sold at this point, just waiting on engineering

[Machiavelli]

Thanks for all the input guys, much appreciated.

[vector1]

since you are playing with exhaust length numbers, here is something that might interest you, it is probably very similiar to your 427. i've read of some significant differences in hp with exhaust length.

--- Single Primary Pipe Specs --- for 427.650 CID from 3500 to 6000 RPM
Diameter= 1.722 to 1.847 Length= 39.4 to 42.2 inches long
--- 2-Step Primary Pipe Specs ---
1st Dia. inches= 1.722 Length= 19.7 to 21.1
2nd Dia. inches= 1.847 Length= 19.7 to 21.1
--- 3-Step Primary Pipe Specs ---
1st Dia. inches= 1.722 Length= 19.7 to 21.1
2nd Dia. inches= 1.847 Length= 9.9 to 10.6
3rd Dia. inches= 1.972 Length= 9.9 to 10.6

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3.163 to 3.413 Tuned Lengths= 21.5 best and also 10.8 or 43.0

--- Header Collector Specs (Megaphone or Diffuser Cone Shape) ---
Diameter= 2.663 taper to 3.663 Megaphone/Diffuser Length= 21.5 inches

Best HP/TQ Tuned Collector Lengths= 21.5 , 43.0 , 86.0 , 172.0 inches long

Worst HP/TQ Loss Collector Lengths= 32.3 , 64.5 , 129.0 , 258.0 inches long

Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness

---- Primary Pipe's Harmonics ----
1st Harmonic = 170.7 inches long ... typically never used
2nd Harmonic = 65.3 inches long ... longest recommended
3rd Harmonic = 39.4 inches long ... highly recommended , best Torque Curve
4th Harmonic = 27.8 inches long ... shortest recommended
5th Harmonic = 21.1 inches long ... typically never used
6th Harmonic = 16.8 inches long ... typically never used
7th Harmonic = 13.8 inches long ... typically never used
8th Harmonic = 11.6 inches long ... typically never used

---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----
1st Harmonic = 172.0 inches long ... longest with Mufflers and TailPipes
2nd Harmonic = 86.0 inches long ... longest recommended with Mufflers
3rd Harmonic = 43.0 inches long ... more bottom-end Torque
4th Harmonic = 21.5 inches long ... highly recommended , best Torque Curve
5th Harmonic = 10.8 inches long ... reduced Torque , more top-end HP sometimes
6th Harmonic = 5.4 inches long ... reduced Torque , not recommended

the collector measurement is from the inside merge of the 4 pipes to the exit.