hite337
Hite Performance
Magnaflow band clamps might be better than my summit band clamps. Mine are as tight as they can be and leak on both sides of the clamp at the seam.
Benefits of the X-pipe on LS V8 exhaust
- Thread starter RigsLS
- Start date
Magnaflow band clamps might be better than my summit band clamps. Mine are as tight as they can be and leak on both sides of the clamp at the seam.
elephantrider
Dedicated LVC Member
my band clamps dont leak either. of course, you have to get a quality clamp.
No excuse....aren't you or didn't you just haul a load of tampons? :N
FDR
Dedicated LVC Member
Smaller diameter pipe increases velocity, but also increases pressure with constant flow rate. On the other hand, larger pipes increase the time individual exhaust molecules spend in the system, allowing them to cool and further increase the mass of exhaust in the pipe, increasing pressure at the engine end.
You may say that's two negatives for a larger pipe, but only one for smaller, so the choice is obvious. However, it is more complicated since actual numbers must be used to find how much it actually effects it. We need to know values at both ends of the system to find a real answer involving temperature, pressure, velocity, mass in the system, and the gas constant for exhaust. A dedicated owner could probably mock up some sensor rigs using the O2 bungs... Maybe even a third set of measurements at the first O2 bung to get the engine's output. Maybe only those readings are ncessary
You may say that's two negatives for a larger pipe, but only one for smaller, so the choice is obvious. However, it is more complicated since actual numbers must be used to find how much it actually effects it. We need to know values at both ends of the system to find a real answer involving temperature, pressure, velocity, mass in the system, and the gas constant for exhaust. A dedicated owner could probably mock up some sensor rigs using the O2 bungs... Maybe even a third set of measurements at the first O2 bung to get the engine's output. Maybe only those readings are ncessary
cammerfe
Dedicated LVC Member
The band clamps I have came from Summit and, as I remember, the brand name is Dynatech. They were fairly pricy but there has been no hint of leak.
KS
KS
Telco
Dedicated LVC Member
You can try smearing some Ultra Copper silicone around the pipes where the clamp goes around. Tighten it finger tight, let it sit overnight, then tighten it all the way the next day. I've been using Ultra Silicone to seal exhaust seams for years and it works great.
The obvious solution, of course, is to use a larger diameter pipe up front and a smaller diameter to the back. This allows you the room for the hot gas to be able to get out, but maintains exhaust velocity as it cools down. On the LS, I'd suggest running 2.25 duals from the engine to the muffler, then 2 inch duals from the muffler out. The engine is only 3.6/3.9 liters, which is a small engine, and going too large on the pipe diameter destroys cylinder scavenging which makes a huge difference in low end torque. For what it's worth, GM used a 2.25 inch dual exhaust on the 1970 Chevelle SS 454 (almost twice as big as the LSV8) and it turned out 450HP. Larger pipes would be better for drag racing, of course, but if you want to retain low end torque I wouldn't go any larger.
RigsLS
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Imagine all the ladies in PA I serviced? They be like "Thank goodness, BigRig brought me these!"
I went to my favorite muffler shop about a year ago. I was getting replacements from end to end, but the owner said that he had ordered a kit for a kid with a fox body mustang, GT40 or something like that. It had X pipes and Flowmasters and he offered it to me for 100 installed so I jumped. Bad idea. While it did improve the power a bit, the noise is awful, I mean it sounds great outside, but it is loud inside.
cammerfe
Dedicated LVC Member
That's due to the Flowmasters. They're well known for their noise. I'd also look to be sure that the exhaust system isn't making contact somewhere in such a way to transmit the sound into the interior.
KS
FDR
Dedicated LVC Member
That is not the obvious choice at all. Velocity doesn't mean anything, despite everyone getting caught up on it. Flow rate matters. You can have an extraordinarily high velocity in a tiny pipe flow a fraction of the exhaust in a slower, larger pipe. Maintaining exhaust velocity doesn't do anything if the smaller pipe creates enough drag and friction that the systems creates more back pressure. As for the SS 454 (7.4 liter), engine speed is also a factor. IIRC the 454 redlines at 4400 RPM vs our 7000. A rough estimate for the same gas, ratio, etc of volume*rpm/2 (to account for only half cylinders exhausting per rev) gives a flow rate of 16,280 liters/minute for the 454 and 13650 for the 3.9. Yes, the 454 still puts out more exhaust, but it's not double the LS. Like I said, rough estimate, but the point is it's more complicated than just pipe diameter and engine volume. Pipe shape, size, length, bends, mufflers, cats, engine volume, mass of exhaust, temperature, pipe material, all kinds of things.
And before anyone says you need backpressure, the answer is simply no, you do not. Plain and simple. There are two things at play resulting in the backpressure myth: killing scavenging effects and going to too large of a pipe. A poorly [re]designed pipe can kill the scavenging effect. A pipe that is too large can put too much mass in the system, allow it to cool and condense enough, and shift from laminar flow to turbulent flow and make it much harder for the engine to push exhaust out. The only engines that need backpressure are 2 strokes. Even then, it's complicated. It's pulsed backpressure that sends pressure waves backwards through the system to keep the cylinder's fresh air/fuel in place, since the compression stage begins with the piston below the exhaust port. Manufactures that care put a lot of time into designing the exhaust system to send that pulse at the right time.
[edited to change "manufacturers that car" to ___ care"]
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cammerfe
Dedicated LVC Member
VERY well said!!!
KS
KS
Telco
Dedicated LVC Member
I'm going to disagree with you here. Not taking extremes, reducing the diameter as the exhaust cools to maintain velocity helps the scavenging effect. As the exhaust moves, mass is moving and when mass moves there is a high pressure zone to the front and a low pressure zone to the rear. You get better scavenging this way.
Here we agree. This is why I didn't say "the 454 came with 2.25 diameter duals so the LS only needs 1.125 diameter duals." While it's true that it's more complicated than the simple figures I used, pipe diameters only come in certain sizes and exhaust flow varies greatly according to throttle position. You can use larger pipes if you are going to live more at the higher RPMs, but for how 90 percent of us use our Lincolns 2.25 to the muffler then 2.0 out the back will more than suffice.
I sometimes wonder if this isn't used by exhaust shops to talk people who don't know what they're doing out of putting 4 inch duals on rice rockets. It's a lot simpler to say "You need back pressure or it won't run right" than to spend an hour explaining how it works.
I actually did this a long time ago, before I knew more or less what I was doing. Had 3 inch duals with mandrel bends and Flowmasters on a 350, with the intent of dropping a 454 under the hood. It was a slug. Later put 2.5 tail pipes behind the mufflers and low end torque really came up. Unfortunately, I never did put the 454 in.
FDR
Dedicated LVC Member
Keeping the velocity up will not improve scavenging inside the pipe. The only thing pushing exhaust down the pipe is the flow of new exhaust at the engine. Yes, exhaust is at a higehr pressure than atmospheric and will "push" itself out, but if you had a single puff of exhaust come out of the engine, it would expand and cool until it reached equilibrium, with a significant amount of exhaust form that single puff in the pipe (if not all). With the engine running, each additional puff pushes the next one out. Any low pressure points downpipe that pull the following pulse forward will also pull back on the high pressure point in front of it. The useful scavenging comes from timing exhaust pulses from different cylinders to put one cylinder's low pressure section at another cylinder's high pressure section. This is done with equal length headers and crossover pipes, but once the pulse is in the same pipe, it can't just pull following pulse forward. That force has to come from somewhere. Namely, that somewhere is the pulse ahead of it.
roncoinc
Well-Known LVC Member
He,hee,heeee....
as a newb i find this thread VERY entertaining !!
sounds more like two stroke tuners arguing about exhaust wave forms !! LOL !!
you know your talking about a little bitty engine with not much power and cat's and mufflers required and such ??
but keep on !!
as a newb i find this thread VERY entertaining !!
sounds more like two stroke tuners arguing about exhaust wave forms !! LOL !!
you know your talking about a little bitty engine with not much power and cat's and mufflers required and such ??
but keep on !!
More than 1hp per cubic inch ain't half shabby for 2003........
roncoinc
Well-Known LVC Member
True,,i was surprised to find that out doing research.
pleased me to see that.
it should do well out on the road and have adequate power for passing and such.
i found it was quicker than my 4cyl volvo and almost as quick as my wifes toyota,,so it should suffice.
but it aint a muscle car,and cant be made into one.
it is what it is,,and i love it that way.
i dont think i have ever been as smitten with a vehicle as the LS !
on an exhaust note,,,
my 350 in the vette @400 dyno HP is running hooker super comp headers into open 4 inch side pipes.
no h pipe,no x,y,or z pipe.
aint never seen a dragster with cat's or mufflers or ANY restriction in the exhaust.
i haven't had a luxury car in awhile and i dont want one sounding like a ricer with a coffee can on the tailpipe.
but that's my opinion.
your mileage may vary.
thank you very much,,,drive thru....
It was NEVER intended to be one. It was/is a sporty entry-level luxury sedan. With enough money, it can be made into one whale of a muscle car!!
cammerfe
Dedicated LVC Member
Just as a point of comparison, at the time I set the ECTA record in E/F CC with my '02 Sport there were such cars also in competition as a 440-powered Mopar that didn't seem to be able to muster the speed in his class that I did in mine. Don't let your ignorance of reality lead you to diss the LS and its possibilities.
KS
KS
1LoudLS
Dedicated LVC Member
god it drives me crazy when people don't understand this...
the only time built up pressure is a good thing on a 4 stroke is when it is spinning a turbine wheel in a snail!
1LoudLS
Dedicated LVC Member
probably has something to do with drag cars not having to be streel legal...
now for those that would like to keep their cars street legal, they actually have to have exhaust, and there are things that you can do to minimize the negative effect on power loss. that is what this thread is about...
FDR
Dedicated LVC Member
A majority of each puff of exhaust leaves the pipe before the next one comes along. The pipes are so short they create negligible backpressure. Any arrangement to create scavenging will likely create more friction on the gas flow and add more backpressure than the scavenging improves.
Your Corvette likely had such short, smoothly bent pipes that the large diameter pipe was not a problem. You'd have to compare it to a smaller pipe of the same shape, not a setup with a full length exhaust system with mufflers.
Telco
Dedicated LVC Member
Exhaust will move down the pipe on its own because the piston gives it a pretty good push along and there's a lot of air pressure there. It doesn't just stop moving until the next pulse comes along. Consider this - the exhaust pulse is a high pressure mass of air that is moving somewhere in the range of 2100 feet per second, and it doesn't just stop to wait on the next engine pulse. It takes around 1/10 of a second for the exhaust to go from the exhaust valve to the end of the pipe on a 25 foot long exhaust system and there is a ton of energy behind it. Problem is, as it moves it also loses a lot of that energy in the form of heat, and colder air is more dense and harder to move. It also loses mass as it condenses down, so to keep the velocity up to get it out of the exhaust, you reduce pipe diameter a bit. Frank, we'll just have to disagree on this, but it's been my direct experience that reducing the pipe diameter a bit after the mufflers is beneficial on a street car. It wouldn't be beneficial on a race car, but then the normal use of a race car involves being WOT at all times, while a street car spends most of its time not at WOT.
Until you consider that 1HP per cubic inch barrier was broken in 1956 or thereabouts. Still, it's impressive how well that little tiny engine moves that big heavy car. While I still feel the LS should have had at least a 5.0 to realize its true potential, the 3.9 isn't bad.
Until you consider that 1HP per cubic inch barrier was broken in 1956 or thereabouts. Still, it's impressive how well that little tiny engine moves that big heavy car. While I still feel the LS should have had at least a 5.0 to realize its true potential, the 3.9 isn't bad.