Calm down, i was quoting you to support what you were saying. I quoted it because your original post was back on page 1. One thing to always remember too is that the components of the system need to compliment one another. Many stock systems don't which often has more to do with performance gains than the actual tube size.

For example, the stock Y-pipe on many V10s was designed to prevent the flutter sound, but is restrictive. Some have argued that the performance mods did little or nothing, but left the stock y-pipe in place. Replace that pipe with one that is better designed, and a lot of power can be freed up. The difference is noticeable whether or not you have any other power producing mods.

I recently read an article where they tested headers. The article was true so far as the results, but was also misleading. They were supposed to be testing headers, but they were replacing more than just headers in the test. So they had too many variables to come up with a good conclusion. For example, they said the shorty headers produces 8 more peak HP versus stock, but they also did a catback at the same time. How do they know the stock manifolds wouldn't have produced 8 more HP with the catback too? in this test they also did longtube headers which also replaced the entire exhaust system. The system ran out as true duals with an x-pipe. It had freer flowing cats, and everything. Just too many variables to say which part of the system was responsible for the greatest gains. So in reality, they were testing and comparing headers, they were testing and comparing complete exhaust systems.

 

BUCCI delivered his theory, in a way, that got my attention...

I am going to try this, the next time, I have access to a dyno... I will try different pipes... Usually when at a dyno, an engine, be it stock, or mild cam ,or race. Has an RPM range, from degreeing or other. One where it make tq, the other HP. I honestly while reading posts , made me wonder, if the difference in opinion come in, with this possible variable. Cams, and where they make power at...Carbs, or throttle body size, changing where the engine used to make power to where it actually now makes power.

It seems that no matter where I post this, there are variables. Not so much on My K & N post, becuas there it is agreed everywhere, that over oiling is the culprit.

I have applied, the variables/theory, to only on the intake side. As the cam is only open so long to charge the cylinder. Like a venturi in the carb, it needs to make volocity, to move swiftly.

 

Yes these guys would be favoring components that produced the most area under the curve.. even if it sacrificed a few peak HP.

That's exactly what the standard Flowtech headers are.. part # 12502FLT

 

Think they will fit a 74' F-100 302 2wd?

 

Hello new here,
I have an 01 super crew with stock manifolds and cats with 3' piping from the cats back into a 3' inlet/outlet borla muffler and 3' piping out to corsa one side double 3' tips and wouldnt change it for anything! Great sound, without it being noisy inside.

 

Assuming you have a 1977 or newer vehicle that has cats on it......it basically boils down to this, the greatest restriction in the system is at the cats, anything that is after that has only a little/slight effect on exhaust flow/back pressure, which is what you are "touching" anyway- ya know a chain is only as strong as it's weakest link- even if the straw you are sucking (or blowing) on is 6 inches in diameter, if the smallest point is 1", then that is what the maximum flow will be! Each vehicle does have typically a unique "quirk" (such as the V10 y-headpipe) that if modified can help a bit on the flow.

No pre-1977 (no cats), its a very different story as the length of the exhaust manifold collector, exhaust port/shape/diameter, placement of the muffler, exhaust pipe diameter, tailpipe diameter does play a definite role in "complimenting the powerband of an engine".

For today's vehicles, they are very well engineered (not that there aren't improvements to be made), but even the best manufacturers (such as magnaflow) have to struggle (ie work very hard) to gain 5-10hp increases in many vehicle applications.

 

Fact is, New cats flow much better then old cats. Old meaning 70's version...

Fact is, new engines come out of the factory, although engineered, arent tunes properly, That causes the market for tuners, exhausts ext... If they where engineerd and tuned, there would be no market for Magna flow, or sct tuners...

Also as far as 6 inch pipe in to 1 inch straw then back, yea??? but isnt that what a venturi is? speeding up airflow, and as it rushed out, would create a vacuum???

I agree maybe not 6 to 1,,, but 4 to 2 1/2?? then back to 4???
That is why collectors are a certain size, 4--1 5/8 tubes... into 1- 3 inch collector? The rushes out, actually causing a vacuum, and you could use that vacuum, by connecting it from the collector to the PCV system, causing neg crankcase pressure... This is anoth issue, but plays into big exhaust pipes.

I was grasping what BUCCI said earlier. But I am gonna be doing some tests here in the near future myself...

 

[QUOTE=Mustang6147;7943804]Fact is, New cats flow much better then old cats. Old meaning 70's version...

Fact is, new engines come out of the factory, although engineered, arent tunes properly, That causes the market for tuners, exhausts ext... If they where engineerd and tuned, there would be no market for Magna flow, or sct tuners...

Also as far as 6 inch pipe in to 1 inch straw then back, yea??? but isnt that what a venturi is? speeding up airflow, and as it rushed out, would create a vacuum???

I agree maybe not 6 to 1,,, but 4 to 2 1/2?? then back to 4???
That is why collectors are a certain size, 4--1 5/8 tubes... into 1- 3 inch collector? The rushes out, actually causing a vacuum, and you could use that vacuum, by connecting it from the collector to the PCV system, causing neg crankcase pressure... This is anoth issue, but plays into big exhaust pipes.

OMG, yes i agree in concept with your reply, ex. engines have a generic tune to satisfy a variety of needs, you can fine tune them to have a little better pickup or tune them to get a little less power and better mileage. But, even if you take the gains of a complete exhaust system such as magnaflow did on the new lexus a couple of years ago (as seen on TV), with aftermarket headers and all custom exhaust out to the exhaust tips, they worked for 3 weeks on the dyno and got.....10 hp at peak.

Now here...

we are not changing the headers, headpipe or cat, so how much gain are we really going to get....

Maybe 1-5 hp within the engines powerband, but it will sound good.

and with regards to the venturi effect, yes that will happen but the internals (slope, return area) all has to be engineered to work, otherwise to get compression, not vacume effect.

Just like the large diameter fire hose & the storz couplings- they use to say you could reduce the couplings to 2 1/2" and there would be no loss of flow.....

Till SAFERS did a flow test and verified, yes there was a substantial loss of flow

I was grasping what BUCCI said earlier. But I am gonna be doing some tests here in the near future myself...[/QUOT

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Here is info that will blow some theories out of the water...

I have been busy putting together executive board meetings, and strategy plans for a club I belong to, also helping a buddy on his pit crew, as he has been short a guy, with family issue's. (Top Fuel Team)

OK... I recieved a call, from a guy, that repaired my furnace, and as he walked threw my garage, the car topic/ Race talk started. I showed him pics trophies ect... one thing lead to another, He has a 1988 S10 with a V6 (4.3) out of an Astro Van. He has been trying to tune the engine, and injection setup. He had 3 different exhaust set ups. Headers, manifolds, H pipes, 2 inch and 2 1/2 inch tubes. Cats (2) glass paks. So I told him my theory, as what I have always applied. I mentioned what I am reading on this post, and other peoples theories and past findings. I then refferred him to a dyno shop, who might let him do a few pulls, with different combo's, and said he can use my name, when he called. He called, the guy set him up with an appointment, after shop hours. said bring a 12 pack to (LOL) The guy landed up not charging me for the furnace call.

He did call me though today... His biggest gains were running Headers, threw dual cats threw 2 1/2 inch pipe back to H pipe then 2 1/2 pipeto glass paks, then 2 1/2 over, and out the back behind the tires. He said he had TQ numbers down with 2 inch pipe. He did say, they had to adjust the fuel pressure at the rail, top acheive these gains.

Keep in mind, he has an after market ignition(MSD) and an After market Fuel inj system... Not sure what brand. SO maybe this is correct, but 2 1/2 with a V6??? Maybe the fuel is the reason for TQ numbers, as the enigne will flow more, and run leaner, and it is after all a rich mixture that builds TQ...

As stated, I was not present at the time of the pulls, but did hear his truck today. I will say his tires will spin, pretty easily.

 

For testing theory, one of the most respected names for headers is JBA. Do you knw what or how the firecone collector works? Everyone will agree, they produce more horsepower and torque than the traditional header. But they do it by increasing the velocity and bringing the exhaust together into a smaller area. they do step up after the merge region. But their design scavenges better, and thats where the performance gains are happening. Doug Thorley does the same thing with the triple y- design. It works differently. But after each y, the pipe is only marginally larger pipe because it keeps the heat and velocity up. The triple y headers produce more horsepower and torque than even longtubes, and they produce the peak torque at a lower RPM, while shifting the peak HP higher up the range. Talk about widening the powerband. Friend of mine recently put triple y headers on his Camaro (track car) and for only a couple hundred, he dramatically improved his placements and ended up getting a better sponsor. Its amazing what velocity can do. What you are trying to do is not to get more power out of your engine, but rather to remove anything that restricts the power. So one way of thinking about it is that different designs restrict less power than others. Oversized piping is a stumbling block.

 

1 test I want to run, is to create a venturi if you will, in the exhaust. Kind of like the carburator venturi which takes air speeds it up, and it also pick up fuel in the process.

What would happen if a venturi type setup would be placed in the exhaust, maybe in the collector, or further back. or in the tubes, and then further back??? Speeding the air, would cause the suction, on the other side? The issue would be, not to creat turbulence, or EDDIES if you will, when the gasses go out into the pipe.

 

An H-pipe kind of does what you just proposed. However an X-pipe is smoother and creates less turbulence, and as a result works much better. You can't usually place these at the collector as proposed. It works better to do that after the collector once the turbulence from merging has had a chance to stabilize.

 

I lost low end torque when I took my muffler off. My Butt Dyno told me all I needed to know. Please don't give me a hard time for not providing real numbers. I'm just stating what I have experienced.

4.9L