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328 Dyno Results: With Tubi & straight pipes VS. Stock Exhaust and Cat

Discussion in '308/328' started by davequick, Mar 6, 2004.

  1. davequick

    davequick Formula Junior

    May 27, 2003
    307
    Bellevue, WA
    Full Name:
    Dave Quick
    218.0 HP, 185.8 ft/lbs peak with STOCK EXHAUST AND CATS
    213.1 HP, 179.3 ft/lbs peak with TUBI AND STRAIGHT PIPES

    Yes, the graphs are as stated, 3 years apart.

    Timeline:
    January 2001, 30k mile service complete, tubi exhaust on the car with straight pipes.

    March 2001, Dyno test w/Tubi.

    No changes to spark plugs, no changes to anything other than fluids (i.e. full fluids flush, multiple oil changes) and the replacement of the tubi with the stock exhaust in

    The only change to the car is more miles and switching back to the stock exhaust.

    You can access more information abou the car and the dyno charts in HUGE jpgs at:
    http://ferrari.threefourfive.com (yep, car is still for sale - two semi-serious buyer types but haven't closed a deal yet - so spread the good word so I'll be one step closer to my 456!)

    Anyway, I was fascinated to see that I improved in HP and torque by moving back to the stock exhaust and cats. It pays to measure. :)

    Hope people find this of interest in some way.

    -dq
     
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  3. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,395
    MO
    Acutually, the differences are within the natural error of the dyno (you have like a 2.2% difference). In other words, sometimes you will get more sometimes you will get slightly less.

    Only way to be sure is to run the car with one setting, record, switch on the spot, run and record, and then compare.

    For even more accuracy, after doing the above set of runs, repeat by switching again running then switching. Average the results of each of the 2 runs.

    PS No way on earth the arachic cats in our 328s improve performance.
    Best,
    Auraraptor
     
  4. davequick

    davequick Formula Junior

    May 27, 2003
    307
    Bellevue, WA
    Full Name:
    Dave Quick

    Well, from the charts it doesn't appear to have hurt performance either.

    Regardless, I liked the sound of the tubi better, but the stock exhaust is on the car while I'm selling it.

    -dq
     
  5. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,064
    USA
    Full Name:
    Hugh G. Rection
    As a point of referrence, last year, my 1987 328 GTS with a recent major service, K&N air filter, stock catalytic converter and Tubi exhaust pulled (on the same dyno) 214.4 hp and 184.1 torque
     
  6. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Many thanks for posting the graphs!

    Very impressive

    If you look at the bottom graph, it's remarkable to me how the Kjet holds the mixture so very lean through the entire powerband. Interesting because it's so accurate and also because I've been taught max power occurs at 12.8 - 13.2. I've seen other Kjet engines run similar A/F and hp #'s, where Motronic progressively richens the mixture as power increases.

    That being said, have attached a dyno graph where all that was changed was a main jet changing the A/F about a full point across the range with no real change in hp. So would also comment that not that much hp would be found by richening the K-jet at the expense of emissions. It's just amazing how lean these cars run against what I've read.
     
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  8. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    I am not sure how the k-Jet works. But given the mixture is lean through the powerband, could it be that the greater flow of the Tubi et al were leaning it out further so that power dropped?

    There is no way I can see a less restrictive exhaust and omitting the cats would rob power.
     
  9. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
     
  10. mk e

    mk e F1 World Champ

    Oct 31, 2003
    11,505
    The twilight zone
    Full Name:
    The Butcher
    I agree with you Russ, it is much too lean. Re-tuning it to around a 13 a/f or so should give it about another 10 hp I think. That is probably why opening up the exhaust hurt the hp.
     
  11. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,395
    MO
    Just wondering, would switching to an electromotive setup increase power in any measureable value? Or is it better at smooting out the power/torque bandS?
     
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  13. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,350
    Osprey, Florida
    Full Name:
    Ali E. Haas
    PMA1010,

    You need to read about an exhaust process called scavenging. Then you will see why you cannot just remove parts and get more power. An exhaust system is a tuned circuit. Alterations frequently result in diminished power.

    Tubi does not just bolt parts together. They have tuned the system to work well with a lot of research. Many people think that as their system seems less restrictive it will give more power. This has not been my observation.

    aehaas
     
  14. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,395
    MO
    Yes but this could be the result of clever marketing. If we are told to look for something its alot easier to think we found it...
     
  15. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,350
    Osprey, Florida
    Full Name:
    Ali E. Haas
    I studied the power graphs. It is interesting that the power is about the same when you reach redline.

    At lower RPM the difference between the two is significant with much better power using the stock exhaust.

    aehaas
     
  16. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,350
    Osprey, Florida
    Full Name:
    Ali E. Haas
    The area underneath the power curve is more important than the peak power.

    My local MB dealer obtained 3 sets of S600 "Powerchips" from different companies all claiming much more HP. The head mechanic and I tested the chips at DeSoto Raceway in a single afternoon.

    The stock chip got my (at that time) brand new car through the 1/4 mile in 14.8 seconds. The next best chip (at a cost of 1,200) was 15.28 and the other chips were even worse.

    aehaas
     
  17. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,238
    Colorado
    Full Name:
    Dave
    Some years ago we had a Tubi rep come to a Fcar gathering. He went on about the sound and reduced weight, etc. I asked him about power increase. He went on for a couple of minutes and never answered my question. I assumed if they could demonstrate a power increase they would be happy to tell everyone about it.

    Dave
     
  18. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Un-arguable: Weighs a lot less; Sounds better (almost too much), looks great

    I do think tubis help hp *a bit* on some, but not all cars, based on exhaust system design. Carobu's side by side dyno tests showed the 308GT/4 profited across the board. Note this is a separate tuned system for both sides. But, I *do not* think it would help a single cat car so much:

    One of the advantages of a flat plane crankshaft is the two four cylinder motors on each side allow very good exhaust tuning and scavanging wave control. On the single cat cars, the two sides simply dump into a common collector after unequal tract flow lengths. The short length stock headers are tuned for upper end, so helps some. Have heard from others that if the two sides are kept truly separate, there is a noticible subjective hp gain. That being said, I do think on separate exhaust systems like the 355 it does help hp.

    I was always taught, you mostly buy a tubi anyway for the glorious sound and any hp increase is a bonus.

    just my 2 Euro.
     

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