I got the new Jegs catalogue yesterday, and lo and behold, they have a dual exhaust kit for thirdgens! $125.00 or so.

 

It's not the dynomax one is it?

 

Yep It is

 

he-he

 

lol

 

just get a single 3 in catback and y-pipe w/ headers. itll flow alot better then those duals will and be easier to install.

 

lol... :sillylol:

 

Blaaahahahahaha:sillylol: .........thats some Funnys **** man!


>hey BTW you have got a nice ride in that sig there. Any updates?

 

sadly no updates

 

They use 3 inch piping not 2.5........geez....

 

So, what exactly is the problem with this kit? Keep in mind that I have stock 305 with heddmen hedders.

 

the pipes are small (2.25 in if i remember). Youd be better off getting a 3 in catback and Y-pipe. It will outflow that dual kit. Basically having that dual kit is overrated. Doesnt do much for performance, just gives your exaust note in stereo. Heh... of coarse i still have my single 2.25 in stock I pipe and muffler hooked up to my headers so i cant talk. Im sure that does alot to contribute to me having a high 14 second 350 powered car.

 

A single 3'' will not outflow dual 2.5'' the only reason people say that is because they can't put duals under there cars. If you put a crossover tube in with duals, you gain all the low end torque of a sinlge exhaust with the mid and high end torque of duals. 2.25'' duals will flow just as much as a single 3'' if not a little less. What you want is scavenging. If you have 2.5'' sinlge then it will scavenge better. That's what you want. Then again, there will always be someone to tell you different without ever driving a car with duals, then again you have people that have and will tell you different because you get better torque with single tube, only if the duals haven't been equalized. Hope this helps somewhat with this debate. Don't flame me.

 

I generally try not to flame, and when I do, it is usually just my smartassticisim showing...

So, basically what you are saying is, the kit will work fine for both low and high end if I stick a crossover or x-pipe in it?

It just seems to me that it would be cheaper to get the kit then pay to have a custom exhaust done my a shop around here.

Also, does anyone know if it exits out the back, or to the side in front of the rear wheels?

 

The kit exits in front of the rear wheels and yes it will restore the lost low end torque that you lose from the single switch over. You can get a crossover kit from Summit Racing under the Summit name or the Flowmaster kit. It would be expensive to have custom duals for our cars done right.

 

So, with the side exits, are there any exhaust fume issues?

 

P/N 289-89009, correct?

One problem with Tom's illustration - they don't fit headers (look in the application listing, not the general information).

Make that two problems; no mufflers, either...

 

I think it's just the shorty headers that it doesn't fit. If you use the long tube headers, it'll bolt right up to those.

AJ

 

Dynomax muffler suck...they'll just rot out. (fiberglass)

 

hey how much more hp do u gain with the kit i might buy it. i got dynomax headers for my 65 elcamino then look fine

 

As I said, I have heddmen hedders...so hopefully it will bolt up to them...I'll probably have to call or e-mail dynomax to find out for sure.
As far as mufflers, I already have 2 glasspacks, so that is covered as well. Worse comes to worse, I can get some adaptor pipes from the parts store to fit the mufflers on.

 

When's the last time you saw a Corvette rot away?

That's probably what happened to my skateboard!!!

AJ

 

Yeah, a vette body gets as much heat as a muffler...sure. Go with an all metal design like a flow of spintech -89IRO

 

any one who says dual 2.5's flow better than single 3 should go back to math class. it is a simple solution of pie to figure crossectional area, that is why I run a 4" mufflex instead of the dual 3" system I used to run.

 

That's all good and well when you are usng the equation for fluid. Try that with air and it turns out much different.

 

actually if you hook a few feet of 3" and a pair of 2.5" to a flow bench drawing 28" of water with radiusus on the ends of both it just confirms the cross section finding.

 

I was hoping somone else could back this up! I'd done the fluid problems in calc before but nobody ever seemed to listen when I said something about it. I always figured you'd get more scavenging effect with a single as well, since you have more exhuast pulses firing through the same tube. IMO duals aren't worth it on our cars unless you don't really drive it on the street. Or you live in a town with really smooth roads and no speedbumps.

 

So you are saying that you put the single 3'' exhaust on a flow bench run it then switch it too 2.5'' duals with a crossover tube. The 3'' will outflow the dual 2.5's? Do you have any proof? I'm not trying to start anything I just want proof. The airflow thing I done here at work with compressed air. The bigger air hose couldn't have with dual hoses. I'm not saying you are wrong, I just want proof not equations or theories. The test I done could have been biased, so I may be wrong. If I am, then I will delete all the posts in this thread. Show me some proof please.

 

using compressed air is the problem, that is why flow is calculated as air rushes to fill the vacuum

 

This is my thought:

dual 2.5" pipe = 2(pi*(2.5/2)^2) = 9.8125 in^2
single 3" pipe = pi*(3/2)^2 = 7.065 in^2
dual 3" pipe = (above doubled) 14.13 in^2
single 4" = pi*(4/2)^2 =12.56 in^2

As you can see, Dual 2.5" pipes have a larger crossectional area than a single 3" pipe, as dual 3" pipes have a larger crossectional area than a single 4" pipe. In the real world, however, it is hard to route a dual exhause on these cars without creating restrictive bends in the pipe. Even with mandrel bends, every change in direction is a restriction.

 

If you do the math, two 2.25" pipes have more flow area than a single 3" pipe (assuming the same wall thickness like 3/32").

But, that doesn't mean dual 2.25" will out flow a single 3". Things like boundry layers come into play, and the duals will have more surface area to create those boundry layers. And, blanket statements never take in to account the details, like bend radii.

About the only way to know for sure is to build a set of each and test them. On the dyno with the engine you'll be using them on would be the best way.

The general info on the Jegs site does mention being able to fit stock manifolds or headers. The application info excludes mounting to their shorties (like AJ said). Makes you wonder if the "flexibility" they tout includes being able to hook them up to long tubes without modification.

 

there are frequency issues too higher frequencies flow closer to the outside and lower flow through the center. Like I said , I switched from dual 3"s to a single 4". mufflex has cars making curently over 600 hp with this system I am going for 500-700hp. I have full length headers and will be looking to try dropping the exhaust at the track for a test when the car is completed. if you go to the track I urge you to try this test (NON-power adder cars only) it will cost you up to a second in the 1/4. I get so tired of hearing guys tell me that their cars are faster at the track with the exhaust off, I once bet a guy the $45 entry fee that his 68 bird was faster with exhaust on, needless to say I raced for free that day.

 

I'm entered in two classes for the Mile High Bracketnationals - that's $90. What to bet me then? I'll take the "Uncorked is quicker than corked" side. I'll be running the '57.

 

which of the two following catagories is your car in, the power adder or the higher compresion seriously cammed class or both. those are a few of the cars that CAN benefit from un-capping. My chassis dyno sez so. besides for all I know your "corks" are a pair of turdbo mufflers (ick ick) or worse

 

Neither. Mild 270 advertised duration cam, 9.7:1 compression, dual plane intake, etc. The "corks" are dual 3" Warlocks w/2-1/2" tailpipes, "uncorked" is removing the Warlock plug. The difference shows up in 60', and ET & speed all the way down the timeslip.

 

That's EXACTLY the muffler (not mufflers) that I'm gonna run on my car when I'm done dropping in the 350.

I wanna run the 3" muffler, with one of those elec. controlled cutouts from www.quicktimeperformance.com where the "cork" would normally go.

How are those mufflers (dB level)? Do they get a lot louder with the plugs out? They seem like a great idea, but that doesn't always mean it IS a great idea.

Thanks,
AJ

 

Uhh, frequencies don't travel in certain parts of the pipe.

The frequencies you hear are shockwaves bouncing all over the place in the pipe, they don't pick a certain route.

 

When you're pulling into the neighborhood at 12:30 a.m. after a night at the track, they are pretty loud. But, when you're out at the track with them corked, you can hardly hear them. Just depends upon the "standards", if you know what I mean.

Uncorked, they are a straight pipe from the collector. Act as a torque tube. Quite loud then.

Where were you planning on mounting it? If in the stock muffler location, then there wouldn't be much performance benefit from being able to open them up, since the losses would be occurring in the upstream part of the system. If in the cat position, then it may be helpful.

 

To reiterate my earlier question, are there any issues with the exhaust fumes when the pipes exit to the sides before the rear wheels? I have seen the setup on stock Ford F150 Lightnings, as well as cars with actual sidepipes, but still.... the whole reason for my replacing the exhaust system is the horrendous leaks, and I dont want to go through all the time, trouble, and money with this kit if the fumes are still going to be coming into the car.

 

many states require that the pipes must at least exit behind the seam of the last passenger door some are more strict. I ran mine with the pipes exiting outward right in front of the tire behind the door. this was too loud so I pointed them down in front of the tire. when I put a 13:1 motor in the car it was so loud I pointed them at each other (facing inward under the car).

 

Thanks for the noise info! What about the exhaust fumes? Especially with them pointing down or inward?

 

With the exhaust pointing out at the rear wheels, then you will catch a wiff of exhaust when you stop or setting at a light. Once you get going you shouldn't have any fumes.

 

Not trying to flame here, but the numbers listed by Mello Yello are incorrect.

Dual 2.5--30.8113
Single 3--22.1841
Dual 3----44.3682
Single 3.5--30.1676
Single 4--39.4384

I listed the 3.5 b/c that is what I will be making once I get all the pieces home from work.

 

What equation are you using? If you're just calculating the cross sectional area, you're numbers are wrong.

2.5": 1.25^2*3.14 = 4.91
3.0": 1.50^2*3.14 = 7.07
3.5": 1.75^2*3.14 = 9.61
4.0": 2.00^2*3.14 = 12.56

x2 for the dual exhaust.

 

Well YOU forgot to allow for wall thickess of the pipe as five7kid mentioned earlier. The 3/32" part.

You have to subtract ~3/32" from the radius (or 3/16" from the diameter) to find the inner diameter of the pipe. After all, that's where the air is flowing, so that's all you want to calculate.

AJ

BTW, I used to be a firm believer that a 3" exhaust system would flow as well as, if not better than, a 2¼" exhaust system. But that would only seem possible on a non-muffled exhaust. If you're comparing exhaust systems that have a muffler (or mufflers) then 2 mufflers will out flow 1. There's just no argument there. However, some mufflers are designed to have all 8 cylinders flowing into them and may not flow as well with only 4 into each one.

That's the sad part of all this "dual vs. single" and ‘1 3/4" headers vs. 1 5/8" ’ stuff. It's all about POWER TO THE GROUND. Whatever makes the car accelerate faster, and there's only one way to find that out..... TAKE IT TO THE STRIP!!!!

AJ

 

Okay...just for the fun of it, let's see what happens...

These are my old numbers:
2.5": 1.25^2*3.14 = 4.91
3.0": 1.50^2*3.14 = 7.07
3.5": 1.75^2*3.14 = 9.61
4.0": 2.00^2*3.14 = 12.56

Here's the new ones:
3/32 = .09375
2.25": 1.03125^2*3.14 = 3.339
2.5" : 1.15625^2*3.14 = 4.198
3.0" : 1.40625^2*3.14 = 6.209
3.5" : 1.65625^2*3.14 = 8.614
4.0" : 1.90625^2*3.14 = 11.265

3.339x2 = 6.679 (dual 2.25"s) is just slightly more than 6.209. I'd still put money on it that the single 3" would actually flow more, since it would have less internal surface area to slow down flow. I don't have any equations for this, though. Just speculation.

I couldn't agree more...I just use any excuse I can to do a little math (I'm going through withdrawal since I've finished all my collegiate math courses ). Not to mention it's a helluva lot cheaper to crunch some numbers than set up scientific experiments to prove it (or go to the track).

 

2 1/4" this, 3" that. Does it really matter? All a matter of OPINION.

When you finish comparing exhaust sizes, are you gonna compare ***** sizes? Isn't that what this is all about anyway??

 

No...actually it's a pissing contest.

If you want, we can apply the same theories to that, then we can use the size of the ***** and the urethra as mathmatical theories to the velocity and quantity of urine that will be projected from the *****.

Would you like us to do that? Or should we all just get together and see who can **** the farthest?

:sillylol: :sillylol: :sillylol: :sillylol: :sillylol:

AJ

 

Farthest, or the most? Since this is a discussion about flow rates.

 

However, there's also the subject of velocity, so distance would be relative also. The inner diameter would also have an effect on that.

LMFAO!!!!

AJ