| Author | Message | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 413 Registered: 4-2002 |
I should also add that headers have a downside. At an RPM below where the header is tuned, the positive pressure wave (the second wave) can arrive at the moment when the intake valve is opening. When this happens, spent mixture is blown from the exhaust through the cylinder head, and up the intake. This is the dreaded header 'hole' in the throttle response, and the cause of the 'engines need a little back pressure to run right' lore. It is also the reason that the 355 exhaust system holds the common manifolding closed until 3500 RPMs. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 412 Registered: 4-2002 |
A manifold allows exhaust gasses to leave the cylinder. A header allows the latent energy of the cylinder to be used to extract more energy from the engine. A heater is a tuned device and connects 3 events in the operation of a reciprocating engine. These three events are: opening of the exhaust valve, opening of the intake valve, and closing of the exhaust valve. As the exhaust valve opens, there remains about 60 PSI of pressure, this pressure blows down the header like an expanding balloon lead by a positive pressure wave. When the high pressure wave enters the collector, it meets a (reletively) low pressure region and a negative pressure wave reflects back up the header. If the header has the correct length, this negative pressure wave arrives at the still open exhaust valve and enters the combustion chamber and arrives at the opening intake valve. This negative pressure wave then begins to pull fresh intake charge into the cylinder even before the cylinder starts to move downward. Since the negitive pressure wave originates from the exhaust, and the exhaust valve is open, the fresh charge is pulled into the header. Meanwhile, back at the collector, the positive pressure wave has reached the end of the collector, and (finding a narrow exhaust pipe) reflects with a positive pressure wave. This positive pressure wave travels up the header and pushes the fresh mixture back into the cylinder just before the exhaust valve closes and while the piston is decending. The sum total is that you can get 5% more power out of an engine in street tune (where you have to be very careful with the mixture that enters the exhaust) and 15% or more in racing engines--just from the exhaust and cam tuning. Headers can be equal length or unequal length; constant diameter pipe, or step increasing diameter pipe. The major difference (between manifolds and headers) is that the header allows the engine to breath at more than 100% volumetric efficiency | ||
| Ken (Allyn)
Member Username: Allyn Post Number: 793 Registered: 10-2001 |
Uh, Rob, I have carburetors. Could it still be an intermittent misfire? It seems to run smooth enough... | ||
| Jens Haller (Jh280774)
Member Username: Jh280774 Post Number: 389 Registered: 9-2001 |
Rob, So what do you thing: Is it worth to spend so much money for the Tubi headers if you already have test pipes, Tubi sport exhaust and K&N AND your normal Ansa manifolds haven�t cracked up yet? (Current situation with my 348tb) Do you think the power gain would be noticeable? Is there better (or louder) sound than with the normal manifolds? Con saluti cordialissimi, Jens Haller P.S. Lots of questions again, sorry! | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 416 Registered: 11-2002 |
Sounds like simply misfire on closed-throttle deceleration, quite normal for an injected car which continues to fire injectors with closed throttle. OEM exhaust systems quiet this, it still happens, you just can't hear it. FWIW, Honda's do this too with louder exhausts if you keep the throttle open slightly on deceleration. Honda shuts off injectors at fuel and emissions strategy on closed-throttle. Also, the "straw" color you see on Ferrari exhausts is not mild steel, it's a stainless steel alloy which turns this color after repeated heating/cooling. Modern Ansa OEM built exhaust's are not mild steel, mild steel cannot be baked in the heat shroud around factory headers. Ferrari wraps the headers to keep exhaust temperatures up to improve efficiency and emissions. | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Member Username: Vwalfa4re Post Number: 859 Registered: 5-2001 |
I have heard bad things about Ansa too, mainly that they rust like a Fiat 850. I have had no first hand experience with this. I only know what previous owners have told me | ||
| Ken (Allyn)
Member Username: Allyn Post Number: 791 Registered: 10-2001 |
When I downshift during heel & toe I get that popping too when I'm blipping the gas, which I didn't get with the mild steel headers. I take it to mean then that my SS system really IS tuned to my car, like the manufacturer claimed! | ||
| Frank Parker (Parkerfe)
Intermediate Member Username: Parkerfe Post Number: 2013 Registered: 9-2001 |
Now now Manu, Ansa exhaust systems are hardly rubbish. | ||
| Manu (Manu)
Member Username: Manu Post Number: 673 Registered: 2-2002 |
In the UK, Tubi manifolds are offered with a lifetime warranty when fitted to road cars. I bet a lot of F355/348/BB etc owners would really appreciate that on their stock Ansa rubbish...... THAT (amongst other things) is what you pay for... | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 409 Registered: 11-2002 |
IME, the term "headers" is loosely defined. It does not imply equal length primary tubes, the only implication is that the part utilizes tubular steel construction as opposed to a more general "manifold" which typically is cast in iron or iron alloy, and in the case of domestic US manufactures in the past, consisted of a "log" into which each cylinder dumped it's exhaust gas without regard to wave tuning. FWIW, Honda and other manufactures do a darn good job at cast iron "headers" in that their design does indeed wave tune the exhaust for improved exhaust scavenging. Wave tuning is what header design is all about. Controlling / influencing / taking advantage of the energy in the exhaust. Visualize the exhaust as a pulse or wave which starts when the exhaust valve pops open to release the pressure left over from combustion. This energy travels like ocean waves into the exhaust system, with a wave front of high pressure, followed by relatively lower pressure "trough". Optimized systems utilize tubular construction to promote adjacent cylinder savaging by creating lower pressure in that particular exhaust port at the exact time the valve opens, the passing wave creates low pressure which effectively "pulls" the exhaust gas out of the adjacent chamber and into the exhaust system. This occurs at the junction of (in a V8) of the four primary tubes called the collector. There can also be further wave tuning downstream at a large crossover tube joining the two four-cylinder groups. Also, Ferrari's OEM Ansa built exhaust manifolds are indeed close to optimized wave-tuned systems. Tubi's look different because of their increased cost to manufacture (appearance is of greater importance) and they're tuned a bit differently to produce actual or assumed power increases. As a side note, the popping sound we all enjoy coming from an F1 car or other race engine is the sound of a tuned exhaust to create super-sonic exhaust flow to promote combustion chamber scavenging. | ||
| John Delvac (Johndelvac)
Member Username: Johndelvac Post Number: 274 Registered: 11-2001 |
Oh - OK. Thanks guys. I knew they were in the same place. | ||
| Roel de Fouw (Spawnz)
Junior Member Username: Spawnz Post Number: 119 Registered: 6-2002 |
Very well said Dr Cosgrove. Also, like Frank said, headers have equal length runners. And to me, this is usually where the beauty lies. Because the runners coming from the cilinders furthers to the back have to be of equal length as the ones up front, they often contain some additional curves to make up for the extra length. These designs are sometimes simply works of art. | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Member Username: Vwalfa4re Post Number: 849 Registered: 5-2001 |
Does Tubi (or anybody) make a header system for the 308's? | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Member Username: Vwalfa4re Post Number: 848 Registered: 5-2001 |
Think of a manifold as 4 exahust pipes merging into 1 right out of the head. A header is more like 4 exhaust pipes leaving the head and remaining individual pipes a long way away from the head, then probably merging into 2, then finally into 1 exhaust pipe way down stream. A LOT less restriction then trying to blow everything into 1 pipe right out of the engine. | ||
| George Ascherl (Georgef360f1)
New member Username: Georgef360f1 Post Number: 16 Registered: 8-2002 |
Does anyone have the Tubi headers on there 360? Would the tubi test pipes work with a fuchs exhaust? Does removing the cats result in a decrease of back pressure and loss of power in the 360? | ||
| John Delvac (Johndelvac)
Member Username: Johndelvac Post Number: 273 Registered: 11-2001 |
Frank - So are you saying that headers are a upgraded replacement for manifolds? They do the same thing, but are not of the same construction? | ||
| Jon P. Kofod (95f355c)
Member Username: 95f355c Post Number: 518 Registered: 8-2001 |
Guys, I have a set of Tubi headers along with the rest of Tubi's GT racing system. I cracked my factory headers numerous times on the Challenge car and finally went with the Tubi system. No problems whatsoever since then. It's a much better construction and hold up to my abuse well. Just to give you an idea a few years back two 355 GT's ran in the 24 Hours of Daytona race. One had the Tubi headers the other had stock headers (slightly modfied). The Tubi car had no problems with the headers the other car cracked the headers at the 4 hour mark. Tubi is the way to go. As far as HP increase I only got 2 hp but I was already running test pipes and no cat before the Tubi went in. Regards, Jon P. Kofod 1995 F355 Challenge #23 | ||
| Jens Haller (Jh280774)
Member Username: Jh280774 Post Number: 380 Registered: 9-2001 |
Ahhh, Then I know! The manifolds from Tubi are thermally insulated and thus far better suitable for racing use where there is a rapid change between cooling off and heating up. These rapid changes in temperature and the fact that the cats are placed too near to the manifolds in the 355 (thus heating up the manifolds even more)causes them to crack faster than usually. From what Manu told me the thermal insulation with the Tubi manifolds prevents these cracks. Additionally the exhaust flow is optimised resulting in a slightly better power output. The hp gain shouldn�t be really big or noticeable unless combined with test pipes, sport exhaust and K&N air filters as far as I heard... Hoped that helped a bit! Con saluti cordialissimi, Jens Haller | ||
| Frank Parker (Parkerfe)
Intermediate Member Username: Parkerfe Post Number: 2009 Registered: 9-2001 |
John, exhaust manifolds and headers are NOT the same thing. Manifolds are usually rough cast, the runners are of unequal lenghts, are not smooth in shape nor texture and thus and are not designed to allow the best exhaust flow . Headers on the other hand are tubular,of smooth shape and texture, of equal lenght runners and thus allow the highest flow of exhaust and thus the most horsepower. | ||
| John Delvac (Johndelvac)
Member Username: Johndelvac Post Number: 272 Registered: 11-2001 |
Manifold is the same thing. How come no one mentioned the 355's tendency to melt the stock aluminum headers (manifolds)? | ||
| Jens Haller (Jh280774)
Member Username: Jh280774 Post Number: 378 Registered: 9-2001 |
Sorry to ask: Does headers mean the same as manifolds? If not what are headers? Couldn�t find anything else offered in the TUBI catalogue! No real result in my english dictionary as well! Con saluti cordialissimi, Jens Haller P.S. Really sorry for this rather stupid question but couldn�t find out  | ||
| EFWUN (Efwun)
Junior Member Username: Efwun Post Number: 219 Registered: 2-2003 |
Try the tubo-solo pipe for the 355 before you go the header route. This system has no muffler at all, just pipes from the cats back. Wonderful scream, and I'm pretty sure a little top end kick. | ||
| Frank Parker (Parkerfe)
Intermediate Member Username: Parkerfe Post Number: 2005 Registered: 9-2001 |
Tino, Bitter about what ? I have no doubt that headers help with HP and that Tubi makes some of the best if not the best out there. I just think that charge way to much for what they are. You can buy a set of quality SS or cermanic coated headers for an American V8 for a few hundred dollars. In fact, you can buy a set for a V12 BMW for less than a grand. But since Tubi knows that most people that own a Ferrari have the money to pay, they charge way more than they're worth. I guess thats the law of supply and demand. I have just chosen at this time not to demand any from their supply. If I ever were to buy headers for a Ferrari I suspect I would buy Tubi though. | ||
| Ken (Allyn)
Member Username: Allyn Post Number: 790 Registered: 10-2001 |
When I got SS headers and exhaust on my Lotus there's no doubt I got more HP and torque. The engine breathes a lot better. The PITA was resetting the carbs and timing to deal with it, but in the end it was well worth it. I'm curious if the newer F cars have to have the engine tweaked when you put a Tubi on. | ||
| John J Stecher (Jjstecher)
Member Username: Jjstecher Post Number: 388 Registered: 1-2002 |
Tino, I got my 348 Tubi off of you a while back and am just curious what a set of 348 headers run around. I am guessing in the 2k range. No matter what they cost let me know and I might be interested in picking up a set. On a side note it is interesting that I just got a set of custom made headers for my Porsche 914-v8 conversion that cost me $500 with coating!! Headers are a great way to make more power, way better than anything else you can do to an exhaust. | ||
| Tino (Bboxer)
Member Username: Bboxer Post Number: 255 Registered: 8-2001 |
Why so much bitterness, Frank ? I used to think you're just a "provocateur" but you lately sound like a wounded man.<g> Seriously though, I KNOW that a better built set of headers does improve HP. I did tests on my own NSX (same day dynos) and recently on other cars. While you may not notice or effectively see an increase with a cat-back muffler, you will see a good difference with headers. And BTW, yes, self promotion is always at the tip of the tongue when the opportunity arises; only morticians and undertakers don't peactice that craft ! | ||
| Frank Parker (Parkerfe)
Intermediate Member Username: Parkerfe Post Number: 2004 Registered: 9-2001 |
And, buying a Tubi really makes a difference to the profit of TubiStyle, Spa.. | ||
| Tino (Bboxer)
Member Username: Bboxer Post Number: 254 Registered: 8-2001 |
I beleive Allan is talking about "Headers" not about a regular Tubi cat-back muffler. Yes it has been often seaid that the headers, specifically with the 355's have produced significant power increase if not restricted by cats and restrictive muffler. We have never dynoed this set up and compared to stock but will do so some day. I recall discussing this very point with Tubi's owner at the national FCA meet last May and he confidentally claimed an increase of 10% in HP and no measurable decrease in lower end torque (which is a risk with faster flowing exhaust/lower back pressure at low RPM). My 2c. | ||
| Jere Dunham (Questioner)
Junior Member Username: Questioner Post Number: 215 Registered: 1-2003 |
The improvement in sound at high RPM's is very noticeable. Not so much at low rpm's. You will lose about 4-5 mph on top speed but the improvement in mid-range acceleration more than makes up for it. Has a nice sound at idle. | ||
| David Stoeppelwerth (Racerdj)
Junior Member Username: Racerdj Post Number: 55 Registered: 1-2003 |
I can only speak from my limited experience. The Tubi (360) is a great step above the stock exhaust. The biggest difference seems to be at idle. A fellow chatter has Tube and the test pipes and his car is the best sounding Ferrari I have ever heard. My system is too new and I have only 10 miles or so on it. From other threads on this forum, I beleive alot of 355 owners are more satisfied with the stock system. However if you get the improvement I seem to have received, you won't be dissapointed. | ||
| allan fiedler (Allanlambo)
Member Username: Allanlambo Post Number: 360 Registered: 6-2002 |
Are Tubi headers worth the price for a 355? Do they make a difference? I would use them in conjunction with test pipes and exhaust. |