So neither of you can explain the physical phenomenon in terms of physical characteristics of the media (temperature, velocity, density), wave mechanics or thermodynamics; you just parrot equations you found in a book with no understanding of the underlying physical phenomena.
And you're telling me that something definitely doesn't work.
Like I said... conventional wisdom is... conventional.
Long tubes for the Northstar are coming... I just need to scratch build a new rear suspension to be able to package everything more efficiently. I'm not sure if I'll be able to fit 180 degree collectors or not. If I can, I'll do dyno testing on multiple types of collector termination.
I always thought it worked like this: Easier out = Good, Harder out = Bad. Big Pipe = Good, Small Pipe = Bad. Larry
It's not that simple. There are a lot of variables and dependencies in the system. There is a such thing as too large a pipe, and exhaust gasses expanding or evacuating too quickly. Intake and head flow capability, ignition and cam timing, firing order, number of cylinders, and displacement all play a apart in what the optimal system would be, as well as simply length and diameter of the pipe. Equal length long tube headers in a true dual configuration on a 2.8/3.1/3.4 60 degree V6 will result in a sacrifice of lower RPM range power (which is where those engines really shine), will almost certainly have reversion in that range, and will likely sound like the engine has a hesitation/miss; especially with poor collector design and the exhaust after that not being up to snuff, as was mentioned by Will.
The "density" of the exhaust gases? Please give me a break.
Hotter = faster Width of pipe is well documented.
As I said already, I did not answer your question because of your attitude.
And, every question you've asked is already in print. I suggest you look it up.
Arn
The diameter of the exhaust pipe isn't really so well documented. There are rules of thumb that say what range of horsepower-per-cylinder is acceptable for various standard tubing sizes, but none of the heuristics address the real tuning variable: primary tube velocity. Just like in intake porting, there is a target velocity that gives best results. That velocity is a function of how much mass of exhaust gas has to go through the port and how much time it has to do so. The temperature and pressure in the cylinder at EVO represents the energy available to accomplish that, with a bit left over at the end of the exhaust event to kickstart the tuning of the intake event during the overlap period.
That means a 12:1 engine is going to have different residual energy at EVO than an 8:1 engine and takes different exhaust tuning, even if both are running the same cam and displacement.
Exhaust gas temperature affects the speed of sound in the gas and therefore can change the tuning RPM of the pipes.
Equal length long tube headers in a true dual configuration on a 2.8/3.1/3.4 60 degree V6 will result in a sacrifice of lower RPM range power (which is where those engines really shine), will almost certainly have reversion in that range, and will likely sound like the engine has a hesitation/miss; especially with poor collector design and the exhaust after that not being up to snuff, as was mentioned by Will.
Absolutely not true. If correctly calculated to the volumetric capacity of the cylinders, the long tube header is WAY superior in low end torque. The reason is the scavenging effect. Short stout headers are made for WOT and are poor at low end torque. You just had it backwards. This is the reason rail dragsters have "tuned" shorties. You would have to drive an equal length long header system on your sequential v6 to understand the drastic difference
Originally posted by Arns85GT: Absolutely not true. If correctly calculated to the volumetric capacity of the cylinders, the long tube header is WAY superior in low end torque. The reason is the scavenging effect. Short stout headers are made for WOT and are poor at low end torque. You just had it backwards. This is the reason rail dragsters have "tuned" shorties. You would have to drive an equal length long header system on your sequential v6 to understand the drastic difference
Arn
You have it backwards. Dragsters don't have "tuned" shorties. Unless you're talking about zoomies on a top fuel car, and they aren't "tuned" for scavenging the exhaust. They are tuned for providing downforce and slight forward thrust. Sportsman class dragsters have fairly long primaries, and a properly designed collector for the primaries. WOT on those cars is also pushing close to 8000 RPM, something you're never going to do in a relatively stock 2.8 V6. Unless you really want to watch it explode, at least.
You have it backwards. Dragsters don't have "tuned" shorties. Unless you're talking about zoomies on a top fuel car, and they aren't "tuned" for scavenging the exhaust. They are tuned for providing downforce and slight forward thrust. Sportsman class dragsters have fairly long primaries, and a properly designed collector for the primaries. WOT on those cars is also pushing close to 8000 RPM, something you're never going to do in a relatively stock 2.8 V6. Unless you really want to watch it explode, at least.
Downforce? Forward thrust? Are we talking star ship cruisers or dragsters?
Downforce? Really............
All high output drag engines have specific exhaust requirements. Headers have been made out of 1.5" and 2" tubing forever. Short fat pipes are great for WOT, especially at high rpm, however, F1 cars have tuned long tube headers for rpms exceeding 10,000 rpm. Their valve timing is so exteme that their low end torque is not particularly spectacular. But the high end torque is huge. F1 cars have specifically designed exhausts to scavenge. Typically a supercharged or turbocharged car does not but if you are really competitive in international high speed racing, your supercharged car will in fact have a tuned exhaust.
BTW, Just so you know, I've spoken to power boat racers who have routinely run 60 degree v6's to 8,000 rpm.
If you are talking funny cars and rail dragsters, you can bet your sweet bippy they have their exhaust size and length very specifically measured and calculated fo the air flow and gas pressures expected.
In the case of the 60 degree v6, there is a logical argument for 1.25" primary pipes. The reason I went to 1.5" was that they do better at the high end. Hedman for instance, builds its headers out of 1.5" with 2.5" collectors for v6. All equal length and long. (They also make shorties)
If you combine a 32" primary pipe with 4 degree valve timing advance, you'll have low torque coming out the wazoo. Listen to the guys who know.
Phone a cam company and ask them about valve timing and torque. Be educated.
Arn
[This message has been edited by Arns85GT (edited 06-24-2013).]
Originally posted by Arns85GT: Downforce? Forward thrust? Are we talking star ship cruisers or dragsters?
Downforce? Really............
Yes, really. The still-burning nitromethane and exhaust gases escaping the engine generate around 800-1000 lbs of downforce, in the exact opposite direction at which it exits, meaning that it also helps to push the car forward.
So please stop trying to be sarcastic; and learn something for once in your life, even if it's not how to deal with any type of EFI instead of how to turn a screwdriver on a carb to adjust the idle speed.
If correctly calculated to the volumetric capacity of the cylinders, the long tube header is WAY superior in low end torque.
"Long" just mean "Length chosen to have the desired effect on the system" vice "Length chosen to be conveniently packaged".
Long enough primaries can operate at low RPM. The momentum tuning effect operates over a wide range of RPM, the resonant effect over a narrower range. Getting the headers synched up to your cam, your intake tract and the RPM capabilities of your heads is where the magic happens.
However, "Long" can mean something very different than "32-36 primaries". That's probably a 4th reflection design around the stock V6 cam and RPM range. A higher RPM range, longer duration cam will make shorter pipes better, while going to a 3rd reflection design will make the ideal pipes longer
F1 engines turn enough RPM that they can have reasonable length primaries while taking advantage of the very powerful first reflection.
[This message has been edited by Will (edited 06-24-2013).]
Will we are talking about small displacement v6's. Do the math and you'll see the outcome on a 173ci is about 34" optimum. I did 33" for space convenience.
The range of 32 - 36 is the correct range for anything from 2.8 up to 3.4. We aren't talking about "long" for a 5.0 or larger after all
Will we are talking about small displacement v6's. Do the math and you'll see the outcome on a 173ci is about 34" optimum. I did 33" for space convenience.
The range of 32 - 36 is the correct range for anything from 2.8 up to 3.4. We aren't talking about "long" for a 5.0 or larger after all
The problem is that you aren't doing enough math. You're only doing a very small subset of the math required to determine the optimal exhaust design for any engine. The formula you keep referring to does not take into account all the complexities of an internal combustion engine.
That is all Will has really been saying. And all you've been saying is "It's right, because I think it's right, and I used a single formula which says it's right."
Originally posted by Arns85GT: How is this in any way related to making true dual headers for a 173 ci v6 engine? I don't get it.
I don't know. You're the one that exclaimed rail dragsters have "tuned shorties" for WOT runs to make maximum power. I simply explained that isn't how that exhaust setup works.
An optimal true dual system for a 2.8-3.4 60 degree V6 would be similar to the Taiwanese true dual setup, which many on here have confused for being 120 degree (or 180 degree) headers. It may not actually be true dual, but it appears to be, and is very difficult to tell from the pictures available if it is not.
Long before I did the "continuation" on this thread, the plan was to put the finished installation on a dyno (after putting some miles on the engine) to see the results. There is a local Fiero with a closely similar 3.4 (manual, not auto) and relatively stock exhaust. I have not yet asked the owner if he was willing to dyno-compare, but I suspect he will be willing. The point is, my gripe about all the "you just don't get it" posts is, I NEVER SAID it would be better (or worse). What I have said from the getgo is, I think it will be a better exhaust than stock, based on the evidence and my past experience (albeit with VW boxers, Formula Fords and Sports 2000 which, I know, ARE NOT 660 engines), I am willing to give it a try and the proof (or not) of the pudding will be when it gets a dyno workout. When dyno results are available, I will post them. That has been the plan from the getgo, and that plan is not gonna change regardless of what is posted in this thread.
It is a great advantage to be able to construct them with the cradle free. I did mine with the cradle in the car, and did the whole job from measurements due to the car being still operational while they were done.
With my current engine I also had a free cradle borrowed from DPWood.
I don't know. You're the one that exclaimed rail dragsters have "tuned shorties" for WOT runs to make maximum power. I simply explained that isn't how that exhaust setup works.
An optimal true dual system for a 2.8-3.4 60 degree V6 would be similar to the Taiwanese true dual setup, which many on here have confused for being 120 degree (or 180 degree) headers. It may not actually be true dual, but it appears to be, and is very difficult to tell from the pictures available if it is not.
This is not a true dual exhaust...
It is a system that pairs cylinders 1-4, 2-5 & 3-6 and collects 3 into 1... good discussion and actual re-engineering (as in, running in a car) over at 60degreeV6.
[This message has been edited by carbon (edited 06-25-2013).]
I don't know. You're the one that exclaimed rail dragsters have "tuned shorties" for WOT runs to make maximum power. I simply explained that isn't how that exhaust setup works.
"tuned shorties" are a term used for running on primary pipes only. Interestingly enough, if you measure the pipes used on rail dragsters I think the average is around 30" long. Some are shorter, but most are over 2'. hmm........
Haven't heard them called that; "Zoomies" is the term I've always seen and used to refer to "uncollected primaries".
It's interesting that Fiero people swear up and down that a crossover does no good, but BMW people take it for granted that their exhausts perform best with a crossover.
Because both engines are even-fire 6's, there isn't any difference between the exhaust tuning on a 2.8 V6 and an M20, M50 or S50 inline 6.
Originally posted by carbon: This is not a true dual exhaust...
It is a system that pairs cylinders 1-4, 2-5 & 3-6 and collects 3 into 1... good discussion and actual re-engineering (as in, running in a car) over at 60degreeV6.
I don't think the exhaust on that 3400 exhaust and the one on that Fiero are the same (though they may sound similar). The one in the Fiero is not a triplex exhaust. It is 1-5 paired, and 3 re-joins them afterward, and 2-6 paired, with 4 joining them later, on the other side. Basically, it's a Tri-Y system, with one cylinder missing from the picture on each side. It appears to be a true dual system, but the pictures are dark, and a couple of spots suggest it might not be, but it's not exactly clear if it is true dual or not. The description on the blog site, and the pictures however, clearly do show that it is not a triplex system with cylinders on opposites being paired up.
Originally posted by Arns85GT: "tuned shorties" are a term used for running on primary pipes only. Interestingly enough, if you measure the pipes used on rail dragsters I think the average is around 30" long. Some are shorter, but most are over 2'. hmm........
What class of "rail dragster" are you talking about exactly? An 8000 HP top fuel hemi engine is worlds apart from a 1200-2400 HP BBC, or an 800 HP SBC. The top fuel dragsters exhaust is only about 18" long, not 30", and the primaries are about 3" diameter.
"Tuned shorties" is what I would call all the shorty header options offered by Banks, Gibson, etc… for the LSx trucks, Camaro, etc… which have been dyno tuned to help improve low end torque and fuel economy.
Originally posted by Will: It's interesting that Fiero people swear up and down that a crossover does no good, but BMW people take it for granted that their exhausts perform best with a crossover.
Because both engines are even-fire 6's, there isn't any difference between the exhaust tuning on a 2.8 V6 and an M20, M50 or S50 inline 6.
Also, the Countach exhaust picture I posted on the first page of this thread. I guess it's so appalling that such expensive race-bred supercars come with complex exhaust systems with crossover pipes.
I remember a guy named Smokey doing a V6 hop up and he used a 6 into 1 header to get the best performance. Due to a 6 cylinder cam, a dual setup isn't worth the bother, unlike the V8, where a dual setup does better. But a dual system on a V8 using an H pipe or X pipe does better than a dual only... Nice to be able to use a shop with dynos and flow benches...
It's interesting that Fiero people swear up and down that a crossover does no good, but BMW people take it for granted that their exhausts perform best with a crossover.
Because both engines are even-fire 6's, there isn't any difference between the exhaust tuning on a 2.8 V6 and an M20, M50 or S50 inline 6.
Different body configuration Will. The X pipe breaks up the pulse before it gets too long and feeds back on itself.
It also spreads the pressure on each pulse. Good idea on a front engine car IMHO.
The Fiero has a real problem when designing an exhaust. You have to have done one to understand
The X pipe breaks up the pulse before it gets too long and feeds back on itself.
Hey, that sounds a lot like...
quote
Originally posted by Will:
In order to do its job, a collector needs to have a specific length. The features that define that length are the merge point of the tubes and something at the other end which provides a change of impedance to cause the pressure pulses to reflect back up the collector and primaries. The collector being open to the atmosphere does this. The collector dumping into a large enough enclosed volume ("termination box") also does it. I've been wondering if the impedance transition associated with an X or merge pipe would be enough to assure that the collector works correctly.
quote
Originally posted by Arns85GT:
The Fiero has a real problem when designing an exhaust. You have to have done one to understand
The problem is no room. We need a "barrel of snakes" design a la 60's formula one cars. They must hinge up so we can open the deck to check the oil. You guys have taken this exhaust design thing way too far when we can barely improve the constipated stock setup.
They must hinge up so we can open the deck to check the oil.
Huh?! What is "hinge up so we can open the deck" supposed to mean? As for checking the oil, the headers for Asterix were fabricated so access tubes/dip sticks to check both oil and trans are unchanged from stock. The oil filter location is now remote so it can be accessed from underneath, and is changed to use a NAPA Gold 1515 filter (or Wix 51515).
Let's look at some design elements on the issue of true duals. And we have to remember that true duals may not be strictly superior to a single out system as some single out systems are just fine.
First, let's talk about my initial offering
These are strictly a long tube header set. This is the set I taught myself to weld on. So they took a long time to fabricate, and the job had to be designed with the engine in the car because I couldn't pull the car out of service. They really woke up the engine, particularly through the lower rpm range, but, allowed the car to really sing. They also had to be fabricated a little like spaghetti on the rear side due to space. Asterix has solved that problem.
Then let's look at my 4.9 exhaust.
This is a case of limited budget, but also, a case of a quicker fab job. Using the stock exhaust logs, (which are way better designed than the Fiero BTW) and a modified CAT back system, it in no way is designed to increase torque or hp. It simply is designed to fit. There is enough torque with the engine that I really don't need to soup it up.
But, there is no gain at all.
Now here are the headers Will has posted. Nicely fabricated and look way better than my 4.9 exhaust.
However, do they offer improved performance? In short no. Look at the primary setup. You have very short primaries flowing into a kind of plenum where you get zero scavenging effect. They system will serve well, and probably sound wicked, but, performance wise? No better than my stock/cat back 4.9 setup.
Now let's look at Asterix.
Now this is the superior example of the lot. Well executed and well thought through. This system has scavenging designed right in. The Magnaflow muffler is actually a perforated straight pipe, and the collector function is satisfied. Notice how he has maintained a smoother pipe flow with large radius curves to help speed the gases along. This setup will scavenge at low rpms and sing when the engine is wound up. With all that heat though, he'll be well advised to install heat shields on the fire walls, and wrap those puppies. That system will be a blast furnace under the hood.
However, it is the best true dual system I've seen.
Whether it actually outperforms Tueleo's is hard to say. On balance I think the longer primaries will give it a different torque curve that Trueleo's, and it would be really interesting to compare Trueleo's all into one setup with it. BTW, I highly respect FrancisT's work and I would have bought it had I known about it before I started my true duals.
If you look at the hedman long tube headers for the S10, you get a good comparison
These headers have more straight run, and the front engine design allows for it, however, the length and pipe size is very similar to Asterix and to mine.
Doubtless the experts who designed these know exactly what needs to be done.
They also design mid and shorty length headers for other applications, and will tell you quickly, that the long tube ones are the best if you can fit them.
Interesting to see some of the different approaches to our midengine setup.
The problem is no room. We need a "barrel of snakes" design a la 60's formula one cars. They must hinge up so we can open the deck to check the oil. You guys have taken this exhaust design thing way too far when we can barely improve the constipated stock setup.
That is complete nonsense. There is plenty of room for an efficient exhaust system, in a Fiero. You can't reasonably say "there is no room" and then have people running true dual exhaust setups. The two just don't fit together. The stock exhaust is roughly the same as was on the 2.8 V6 S-10, Camaro, etc… of the era. It's not that restrictive a design, either. The main problems with the stock exhaust, are the stock intake, and the exhaust log manifolds and Y pipe. And the main restrictions in the exhaust itself, can easily be ground out. That combined with a new cat and new muffler, the stock Fiero exhaust is plenty enough for a 2.8-3.4 60 degree V6 to perform quite well. If you want a reason to go to larger diameter or true dual setup that's going to make a difference, you're going to need to solve the intake problem, and upgrade the valvetrain and cam, and probably swap to a 7730 ECM, DIS, and digitial EGR if you're not deleting it. Also, I think the 7730 can handle true duals with an O2 sensor on each bank, which you really need if you're going to run true duals with EFI.
When you're running a carb, there are some things you can just ignore and take for granted though, which is exactly what Arn was doing.
Actually, what most carb guys do is ignore all the electronics. They go mechanical instead.
But, the exhaust is totally unaffected by electronics. It is a strictly a pneumatics application. Where this overlaps is with the turbo applications where the electronics must be modified to accept the change in the pneumatics.
But, for an exhaust, the exhaust doesn't care if it is dealing with EFI or carb. The application is exactly the same.
What I ignored was the heat applications you get into with very high output engines. However, the length and width of primary pipes is a well documented and consistent formula used by many.
Originally posted by Arns85GT: But, the exhaust is totally unaffected by electronics. It is a strictly a pneumatics application. Where this overlaps is with the turbo applications where the electronics must be modified to accept the change in the pneumatics.
But, for an exhaust, the exhaust doesn't care if it is dealing with EFI or carb. The application is exactly the same.
The ECM on a Fiero absolutely cares about what exhaust it's dealing with though. And the exhaust is very much affected by the electronics. Those electronics determine how much fuel is being put into the system, when it's being ignited, etc… more so on even more modern engines, with DBW throttles and such.
By switching to a carb and dumping the electronics, yes, you get to ignore all that. But on a stock 2.8-3.4 V6, these things must be considered. You can't just run an O2 sensor for only half the exhaust, and expect the engine to function 100% correctly. There will be issues.
But on a stock 2.8-3.4 V6, these things must be considered. You can't just run an O2 sensor for only half the exhaust, and expect the engine to function 100% correctly. There will be issues.
If the injectors are known to be good (and flow the same as each other), and there is nothing mechanically broken on the engine, then on a batch fire engine like the 2.8 / 3.4 it won't make one bit of practical difference if the O2 sensor monitors one bank or the whole stream. The only difference I can possibly imagine is it may take a few seconds longer to heat up the O2 sensor.
Hell, even on my 3800 even though the manifolds both have O2 sensors in them (came off an F-Body), I'm only using one bank because my PCM is out of a 98 GP and only has provisions for one bank of fueling. The rear 3 cylinders provide a pretty decent view of mixture, and my motor isn't even batch fire.
Why are you so on fire to crap on other peoples' ideas / work? Seriously, just go work on your own stuff before covering us all in negativity.
By switching to a carb and dumping the electronics, yes, you get to ignore all that. But on a stock 2.8-3.4 V6, these things must be considered. You can't just run an O2 sensor for only half the exhaust, and expect the engine to function 100% correctly. There will be issues.
I have an O2 sensor on mine. And I use it. No reason at all not to use one. And, like the man said, the sensor can read one side only and get along just fine.
I sort of get your point, but not the forward thrust stuff.
How is this in any way related to making true dual headers for a 173 ci v6 engine? I don't get it.
Arn
If you have stood at the starting line at a top fuel event you would totally get it (the downforce and forward thrust part). Should be on everyones bucketlist.
[This message has been edited by DimeMachine (edited 06-26-2013).]
Originally posted by aaronkoch: Why are you so on fire to crap on other peoples' ideas / work? Seriously, just go work on your own stuff before covering us all in negativity.
Why are you so quick to turn any discussion into a personal detraction on someone else's own projects? Keep it to yourself already.
Good for you for having your 3800 running. I don't care if you have it running or not, or if you have it running OK with only 1 O2 sensor.
