eclou

No. That is totally incorrect. The only place the pulse waves travel and reflect without any cancellation waves is in the primary tube. Downstream of the primary the pulses from the other primaries will negate most of the effect of any reflection from the tailpipe.


Also totally incorrect. Sound velocity in gas is proportional to temperature i.e. as temperature increases so does the velocity of sound. Sound transmission is faster in liquids than gas, solid than liquid due to particle density, but that is totally different than velocity in a gas where the most important factor is temperature

rflow306

This is were physics and terminology can become tricky. In the header it acts more like a pressure wave than a sound wave at atmosphere. The speed at which pressure waves travel is greatly affected by temperature: higher temperature means faster wave speed lower means slower. To calculate the wave speed you use this formula.
c=(KRT)*1/2
The term c is the speed of wave. It is dependent on the temperature T (in degrees Kelvin) of the incoming flow, the air ideal gas constant R, and the specific heat ratio k.

eclou

Actually terminology has nothing to do with it. The sound in a gas or air is always a compression / pressure wave. Sound velocity will be the same in the header as in the atmosphere with regard to temperature - it is always faster in higher temperatures. Air pressure has an almost negligible effect. The main difference in propagation in a gas vs solid is that in air the gas particles are not in contact with each other and thus do not increase the transmission by direct vibration.

rflow306

It has everything to do with and you just proved it the sound in a gas or air is always a compression/pressure wave. A Sound wave at atmosphere can travel through solids and liquids. I agree with your statement I was trying to explain it in the nicest way.

eclou

Got it. I was worried that I had somehow woke up in another universe where the laws of physics and chemistry and I would have to walk across the Mass Ave bridge again in minus 10 windchill to relearn everything

rflow306

Dam Harvard bridge. My hats off to you that means you went to Harvard or MIT. I on the other hand got a degree in EE from Suntan U. (Aka University of Miami).

eclou

Hats off to you. You went to an environment thick with exotic nubile young women vs the Boston feminazi's gorging on Marble Slab and fighting to change the spelling of "women" to "womyn." These are the finer points that no HS counseler ever mentioned....

E55 RUSS

Did anyone actually tried them out ???

PTE

WELL I sleep at a Holiday Inn Express!! and wo ke up in the school of Hard Knocks

I Would like too GIVE many Thanks to the War vets , for helping us keep the many freedoms we enjoy every day
Thanks ___PTE___

sly55

Gee, this thread is HEAVY! I never really liked physics... Can we throw together a simple summary of peoples real world gains and maybe the cons and pro's so that the non-physics people can more easily decide which headers to buy?

SleeperX

As we debate which headers are bettter, 4 into 1, 3 into 1, equal length, etc, are we overlooking something here. What is the number one enemy of a FI car. Isn't it heat.

Consider how much heat these headers must be putting into the engine bay vs. the stock exhaust manifold. I think out of the headers highlighted in this thread: renntech, evosport, Kleemann, and Supersprint, the Evosport headers make the most sense for our cars because they are coated to keep the heat inside. This could be why DJE55's car is so powerful. Not because of the shape or size of the headers, but because they are coated. Think of all the heat that these headers are letting off. Hot air rises --- right onto the air intake tubes of these cars. If the intake tubes are not thermally wrapped, the headers will cause the air going into the throttle body to be much hotter than an exhaust manifold would. I think it is almost imperative to get the air inatke tubes thermally wrapped or have the headers coated if you would to see tru performance gains. I have the Renntech headers and am happy with them, but think I will need to get my air intake tubes thermally wrapped now becuase of the headers.

rflow306

That's why you get the headers hpc coated. The renntech headers shown in this thread look like they are hpc coated unless they are just polished, hard to tell from the pics.

SleeperX

I believe they are just polished. What is HPC coating?

E55 RUSS

Is there any difficulties/tips installing Headers on E55???

rflow306

There are different company's that do it but Airborn, Jet Hot and HPC are probably the most famous. Here are the links http://www.hpcoatings.com/,http://www.jet-hot.com/,http://www.airborncoatings.com/

SleeperX

Thanks! Interestingly enough, I am pretty sure that the Renntech Headers do not come coated from the factory..

GTA23109a

I had my Renntech's coated by Jet-Hot. It's simple to have done and not very expensive.

SleeperX

Did you notice a difference in performance. Are your air intake tubes wrapped?

GTA23109a

I did several other mods at the same time, plus I never ran the headers uncoated, so it's impossible to quantify the results of the coating by itself. Based on experiences with my race cars, coating the headers greatly helps reduce heat-soaking and usually requires one or two jet sizes more in the carb to keep the mixture right. Basically that translates into the car wanting more fuel/making more power. Plus, I can work on the car without melting my hands (best part IMO).

I have not wrapped my intake tubes. IMO, the only benefit to this would be slightly less heat soak sitting in traffic, at a light, etc. Once the car is moving again, it should only take a few seconds for any ill effects from hot tubes to be negated by the fast-moving air. I know that having the headers coated assists in keeping underhood temps down, but there's NO WAY to completely alleviate the problem on ANY car. I've tried. For me, the PITA of wrapping the tubes combined with the look of the wrapped tubes themselves FAR outweighs any marginal, potential performance increase.

vader

PTE....we went to the same school !!!!!!!!!! Only difference is the Ford motor you played with..I STILL play with 427 Chevy motors !! Grumpy and Eclou...you guys know your stuff !!! This is a great thread. Kind of like being in the pits and listening to Grumpy Jenkins and Austin Coil talk...except less expletives. The part that is taking me the longest to get used to since getting this car is the fact that it's a MERCEDES and here I am in the middle of Super Car world again !! Who'da thunk it !! =

stevebez

Gee I really love this physics lesson ... would be nice to get a 55 on a dyno and swap out headers to see if theory = observation ...

Wondering if the return pulse wave (from where-ever it comes header end or tail pipe) hits the exhaust valve when closed - can it cause damage to the valve / stem over time or is it too weak ?

I was told that I would need to retune my ECU if I fitted the Evosport headers ... why would I need to do this ? The header has same diameter tubing but longer tubes - albeit with one substantially shorter than the others ... is this why ?

Also ... is this why the individual cylinder mapping on the new SL55 will benefit most from any header design ?

siswati

Guys

thanks for a really awesome thread - this in depth discussion (by those that really know their *****) is one of the main reasons I live on this board.

Well of course I do tune in to see the latest Improviz outing or the latest ClayJ duck-and-dive-and-threat manouver. Hey where are you guys?

So Grumpy, Eclou, Albert and all you fine tuners out there - keep these informative posts coming - I learn something new every day.

many thanks

Finny

I have these on mine... they work very well.

Grumpy666

At 6000 RPM, an exhaust valve is opening and closing 50 times per second with hundreds of pounds of spring pressure acting upon it. Those pressure waves cannot compete with this amount of physical abuse. The waves will not affect the valve.

Headers flow significantly better than the stock exhaust manifold. In open-loop mode this will cause the A/F ratio to become leaner. The retuning is to address this.

The individual cylinder mapping, if we're talking about the same thing, addresses detonation on an individual cylinder basis by retarding timing on the offending cylinder(s). If installing headers improves any A/F ratio differential between cylinders, then yes, there could be an improvement - but I doubt that it would be measureable.

eclou

The SL55 system as I understand it allows for individual fuel metering of each cylinder by going away from batch-fired injector pulses to individual injector control. There are some aftermarket stand alones that do the same thing. I have never heard of individual ignition timing but it would be an interesting concept. Back in college a couple of my roommates and I tried to pitch a concept of electromagnetic valve timing to Ford, which was not taken too seriously.