3" exhaust on a non forced induction truck?

[jamisobe]

Originally Posted by LC80Ducati996

Argh.. I give up..

Pulse tuning of primaries and secondaries is one thing. The back pressure caused by the muffler and tailpipe is another factor. Back pressure does effect the tuning of the pulses.

Want to really get techy?

Amazon.com: Scientific Design of Exhaust & Intake Systems (Engineering and Performance): Philip H. Smith, John C. Morrison: Books


Check out forumula 1 primaries... Steped primaries and the start out shaped exactly like the exhaust ports and gradually go round then step upwards in size for anti-reversion and pulse tuning.

Hmm so a 4 stroke inline 4cylinder sportbike has the gradually tapered up exhaust on it from the factory. Hmm for racing homologation purposes there are set displacement sizes that each mfg makes. All of them are building their exhaust like that. Since getting the most specific output from the engine is key in keeping up with or winning the output contest for that class of bike I have but one conclusion. They use it because the "stuff" works!

All that is well and good, but bikes as well as Formula 1 run at very high rpms which completely changes the dynamics required to achieve correct pulse tuning. I hear you talking regarding these applications, but I think you fail to recognize that car manufacturuers such as Toyota, Nissan, Honda, Porsche, Ferrari, and etcetera use longer secondaries also after spending $$$ on design and testing. The difference is clearly RPMs.

You might convince me otherwise, but not by referring me to a book that will likely confirm what I know. Post a link to a write up that explains why and how short, cone shaped secondaries increase exhaust scavenging at RPMs lower than 6k in street cars and trucks.

[jamisobe]

Originally Posted by alia176

jamisobe

Thanks for the info, it's much appreciated. You're making think seriously about going over the chassis rail - still not sure of the 3" size pipe yet....

Your welcome. I might go with 2.5 unless you are going to do some things that will be able to take advantage of the extra flow provided by a 3" diameter. Either way, I would try to use a Y collector for sure.

[landtank]

Originally Posted by LC80Ducati996

Its all about ETA and $ between your and their manifold..

An engine management solution will be required to tune it for the increase in induction.. I dont get smogged.. It will still run clean and not be big poluter but any aftermarket EMS will not have OBDII and the associated CELs.. Though many can be setup to run a EGR solenoid and setup properly there are some gains (minor) to be made MPG wise with a EGR system..

While I sell my designs to those who want them I'm not in it as a business. It will get done when it's done and if I never sell one that's OK.

No engine management needed with my MAF housing.

Sorry for the hi jack, I was simply letting people know how I did mine and for what reasons. I had to leave town Friday night and didn't get a chance to take some pictures. If this thread is still active when I get back I'll do so then.

[LC80Ducati996]

Originally Posted by jamisobe

All that is well and good, but bikes as well as Formula 1 run at very high rpms which completely changes the dynamics required to achieve correct pulse tuning. I hear you talking regarding these applications, but I think you fail to recognize that car manufacturuers such as Toyota, Nissan, Honda, Porsche, Ferrari, and etcetera use longer secondaries also after spending $$$ on design and testing. The difference is clearly RPMs.

You might convince me otherwise, but not by referring me to a book that will likely confirm what I know. Post a link to a write up that explains why and how short, cone shaped secondaries increase exhaust scavenging at RPMs lower than 6k in street cars and trucks.

I made no mention of short secondaries or that we needed any specific length, I know all about primary length. You have that peged.

YES F1 are shorter for high RPM and average hot street cars are longer. None the less stahl has made plenty of steped primary muscle car headers for pushrod v8s peaking hp wise around 6k rpm.

You just dont care about steped primaries which are something that is done in addition to tuning primary length for the desired RPM.. Nor do you aknowledge what is the best way to get CFM in a full street legal exhaust.

[LC80Ducati996]

Originally Posted by landtank

While I sell my designs to those who want them I'm not in it as a business. It will get done when it's done and if I never sell one that's OK.

No engine management needed with my MAF housing.

Sorry for the hi jack, I was simply letting people know how I did mine and for what reasons. I had to leave town Friday night and didn't get a chance to take some pictures. If this thread is still active when I get back I'll do so then.

Your caster plates are the shazlenit. Happy with them.

I just prefer a full standalone EMS with wideband, knock sensors, huge GM MAF in blow thru, EMS controlled boost (watchdog) and other cool stuff. I am probably planning on testing the PSI limits a bit more than others. I ran E85 fuel and 30psi on the street in AWD eclipse before with a full EMS. It takes a good while to get it all setup but is awesome for tuning and protecting the engine.

[jamisobe]

Originally Posted by LC80Ducati996

I made no mention of short secondaries or that we needed any specific length, I know all about primary length. You have that peged.

YES F1 are shorter for high RPM and average hot street cars are longer. None the less stahl has made plenty of steped primary muscle car headers for pushrod v8s peaking hp wise around 6k rpm.

You just dont care about steped primaries which are something that is done in addition to tuning primary length for the desired RPM.. Nor do you aknowledge what is the best way to get CFM in a full street legal exhaust.

You made mention of short secondaries by claiming a step after the cats would produce hp gains. A step after the cat means that the tube before the cat and after the merge collector is the secondary.

I visited the Stahl Headers website and found this:

STEPPED HEADERS
Stahl headers are available in a stepped configuration (multiple tube sizes in the same pipe). The stepped primary usually increases either midrange or top end power, depending upon the base header tube size relativity to its power level. Step headers are not cost effective for most types of racing and we have never seen more than 1% power difference.

A possible 1% power gain for very limited types of racing is quite a stretch when suggesting significant power gains for the set-up in general for muscle cars, etcetera. Sounds like snake oil to me, especially since we are talking about street vehicles for which Stahl would apparently not recommend "stepped headers" and we are discussing secondary tuning rather than the primary tuning.

Try again, post a link to a write up that explains why and how short, cone shaped secondaries increase exhaust scavenging at RPMs lower than 6k in street cars and trucks.

[LC80Ducati996]

Originally Posted by jamisobe

You made mention of short secondaries by claiming a step after the cats would produce hp gains. A step after the cat means that the tube before the cat and after the merge collector is the secondary.

So if some one puts on a huge tip at end of the tailpipe it becomes the secondary?

SORRY but I dont consider things 2-3ft plus past the collector to be considered secondaries.

With the steped primare reference... it is only "1% gain" however it is still a gain. Yes not worth pursuing at the header on an 80 series then again it was not my intent. It was to prove that gentle expansion of diameter increases power.

We are way off from what I wanted to point out. It was simple.... going up to 3" gradually over a long conical section will out flow a short cheap necked adapter.

Farther back as the exhaust has cooled and slowed the LONG conical expansion section will show much more power than a sharp step up to the cat back diameter.



3 Degree Transition

They can even make a 2.25 to 3" that is quite long.


This is one is how NOT to do it.

[jamisobe]

Originally Posted by LC80Ducati996

So if some one puts on a huge tip at end of the tailpipe it becomes the secondary?

SORRY but I dont consider things 2-3ft plus past the collector to be considered secondaries.

No, the secondary is at the end of the original sized pipe off of the merge collector (the tail pipe exit if no muffler) or at the first appearance of an area of greater cross section.

Originally Posted by LC80Ducati996

I know all about primary length. You have that peged.

Nor do you aknowledge what is the best way to get CFM in a full street legal exhaust.

This is an interesting tech article found on The Sanderson Headers website:

The Complete Performance Exhaust System


Sanderson makes headers for V8s, but most of the principles are applicable. Worth a quick read. Here a couple of tid-bits I cherry picked from the short article:

• Anything that causes turbulence or back-pressure in your exhaust system reduces the power that intake or engine modifications can create.

• Changing the diameter up or down within the system will "confuse" the exhaust by creating turbulence and excessive backpressure.

[jamisobe]

Originally Posted by LC80Ducati996

With the steped primare reference... it is only "1% gain" however it is still a gain. Yes not worth pursuing at the header on an 80 series then again it was not my intent. It was to prove that gentle expansion of diameter increases power.

Dude, you said that:

Originally Posted by LC80Ducati996

"stahl has made plenty of steped primary muscle car headers for pushrod v8s peaking hp wise around 6k rpm.

The Stahl website said that stepped headers were an outside shot in few forms of racing for no more than a 1% difference at best. You claimed that they were selling them all day long to put on street muscle cars.

Please.

[LC80Ducati996]

Sanderson made no reference to how much of a change in diameter, how quicklly nor how far back. Being on the trail to someplace sandy (yet still in the US for now) I dont have my library of books with me.

I have seen studies where long conical increases to a larger diameter have increased output. As a general rule the way 99% of people change diameter when they install a larger cat back does infact reduce power. Most people use the short steps. Now look at a 3* or a 7* included angle transisiton... does this look like it creates a bunch of turbulence... I think not.

They are crazy with their cruisers and patrols over there...

Literally

YouTube - with nissan patrol - qatar

[jamisobe]

Originally Posted by LC80Ducati996

Sanderson made no reference to how much of a change in diameter, how quicklly nor how far back. Being on the trail to someplace sandy (yet still in the US for now) I dont have my library of books with me.

I have seen studies where long conical increases to a larger diameter have increased output. As a general rule the way 99% of people change diameter when they install a larger cat back does infact reduce power. Most people use the short steps. Now look at a 3* or a 7* included angle transisiton... does this look like it creates a bunch of turbulence... I think not.

Give it up man.

At least until you can come and link to a study that gives any credibility to what you are saying. So far, you have only diminished your own credibility as a reliable source by saying things that are not true while providing no sources for unconventional ideas you keep saying are true. Why should anyone believe you?

[jamisobe]

Originally Posted by LC80Ducati996

They are crazy with their cruisers and patrols over there...

Literally

YouTube - with nissan patrol - qatar

Ok. This is true. They are crazy.

[LC80Ducati996]

Originally Posted by jamisobe

Give it up man.

At least until you can come and link to a study that gives any credibility to what you are saying. So far, you have only diminished your own credibility as a reliable source by saying things that are not true while providing no sources for unconventional ideas you keep saying are true. Why should anyone believe you?

None of the above are true.

steped primaries increased power.. yes only marginally.. but not my whole point anyway.. Oh and excuse me for being a bit busy training up for deployment and calling home to get right on finding the article I KNOW for a fact supports my actual statements and not someone elses distortions of them.

RotorSports Exhausts

The A'PEXi N-1 Exhaust

Made for racing. Minimal bends with increasing diameter piping for highest exhaust flow

A'PEXi U.S.A. - Products: Exhaust

the metric measurements seperated by dashes indicate the diameters used. No transitions are abrubt..

I know for a fact I have seen it in more than one of my books back at home!

Not going to taper the whole thing but still makes a case for why a 3-7* angle transition between stock front pieces and a 3" catback would perform well..

If 2.5" or 3" is still up in the air to a degree as I have yet to see a chasis dyno back to back of the two for a cruiser... I do know that if induction modifications are on your list such as head work you can easily get a modified 1FZ into needs a 3" system hp range. Straight up stock 2.5" is probably fine.