308 header length - does it matter? | FerrariChat
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308 header length - does it matter?

Discussion in 'Technical Q&A' started by Peter, Jan 25, 2021.

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  1. Peter

    Peter F1 Veteran
    Owner

    Dec 21, 2000
    6,440
    B.C., Canada
    #1 Peter, Jan 25, 2021
    As I'm in the midst of rebuilding my motor, I have been examining the headers and it's always been curious to me, that nearly all other V engines have headers that are more-or-less equal length/proportions between respective banks, yet these, are clearly not.

    The front header has somewhat lengthy secondary pipes that turn 90 degrees to meet to the final, single collector and the rear header, has virtually no secondary pipes and terminates to the single outlet. It too has a very short run into the muffler and the front header has an additional pipe that's about 2 feet long and then goes into the muffler.

    Does this "unequalness" really have any bearing or influence on flow/back pressure/exhaust wave pulses? I understand fully that it is this way because of packaging reasons, and it really isn't conducive to making it any better, if one wanted to make it truly, equal length.

    Has anyone ever done any flow tests on these? I'm curious to know if there is a difference. Thanks.

    (very old pic by-the-way):

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  2. Ferrari Tech

    Ferrari Tech Formula 3

    Mar 5, 2010
    1,217
    Georgia
    Full Name:
    Wade Williams
    #2 Ferrari Tech, Jan 26, 2021
    It makes a difference. However, with the performance level of the typical street driven 308, you will never feel it. There are a number of ways to evaluate this. Dynomation 6 allows one to change, alter, switch or in any other way you would like adjust the header and exhaust and see what it does to your engine. Of course the input of data is the most critical part to get an accurate estimate of your engine. Burns Stainless https://burnsstainless.com/pages/race-engine-spec-form has this form you can fill out and they will evaluate and give you there recommendation.
    Custom headers and exhaust are very expensive. They work and will make more torque and HP but is it worth it? That is up to each individual and what they want. If you are adding a 360 crank and bigger sleeves for more displacement along with different cams and bigger valves with the port work to go with the valves. Then you will want EFI to make it all tunable. Then, custom tuned hand fabricated exhaust system just becomes part of the plan.
    In my opinion, if you are rebuilding your 308 and it is all stock. Just clean it all up. Put new donuts on it and bolt it back in.
    Oh, pick the muffler that gives you the sound you like. I do think that is worth it just for the sound alone.
     
    Peter likes this.
  3. wmuno

    wmuno Formula Junior
    Silver Subscribed

    Dec 24, 2007
    522
    Wilmette, Illinois
    Full Name:
    Bill Muno
    #3 wmuno, Jan 26, 2021
    Tuning of exhaust headers is both art and science which usually requires dyno testing to verify the results. Flow in the exaust pipes is actually a series of positive and negative pulses. For a given RPM, the length of the pipe will allow a negative pulse to occur during inlet and outlet valve overlap. This allows the extraction of residual exhaust gas and the injection of fresh charge into the cylinder. The length of your longer rear pipe can still be tuned to allow a negative pulse to occur during exhaust overlap. I would not be concerned about the difference in lengths. I'm certain Ferrari has dyno tested your exhaust system to produce maximum power for the upper RPM range.
     
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