News

308 carb airbox restriction discovered

Discussion in 'Technical Q&A' started by snj5, Feb 20, 2005.

  1. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Thanks for posting pics. Informative.
    Philip
     
  2. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Dana, it looks like you topped me on that mod! nice work.
    Instead of foil, one might consider a ceramic insulating coating to cut heat ln the intake tract, with a wrinkle finish powdercoated over that for a stock look.
    As to the length, torque issue, I looked long and hard at it when I designed them. If you measure the differance, they are only 3/4" shorter, which IMO is not enough to alter the power curve, and the addition of better air flow covered it nicely, and may have cause somewhat of a plenum effect. If it were 1.5" shorter I would expect to see a change in power band.
    Next on the agenda is the HORRID 2 valve air filter assembly. Flow Benching a 4 valve air filter assembly produced 98% of the range tested. Without even shutting the Bench down, I pulled the 4 valve and replaced it with the 2 valve housing, only to see a 71% flow!
    As the 2 valve element is the same width, but a bit shorter in length, thicker too. I tested the elements next. Using the 4 valve housing, with a short piece of foam to cover the 2 valve elements length, damned if the 2 valve didn't out flow the 4 valve by 3 CFM. BUT... The temp was a few degrees higher, no doubt due to the deeper flutes on the element causing friction in the air flow. So IMO that is a wash as to power output, a few more CFM, but warmer.
    They angled the element at an awkard angle on the 2valve. dont ask me why, LOL. Maybe it was Wine Festival Week. The new housing will fit the stock one directly, even in the Mondial, where space is a real problem, and will use a stock element size. that way, you will still be able to use whatever element you allready have. (NO K&N debate here).
    Glad your'e having fun with it!
    Kermit
     
  3. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    I will be running a stock type Baldwin element in lieu of a K&N. From what I have read, based on performance gains or lack of, the main advantage to using a K&N is reusability. Not much in the realm of increased performance numbers.

    I think with the opened up box and "short stacks" I will be getting all of the air I need under "normal" conditions, (a relative term, and you know how we feel about relatives).
     
  4. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    I must confess that I had always believed that while in theory, the cold air ram idea of the stock airbox was nice, but did not make that big of a difference in actuality - i.e, the smaller individual Pierce filters would outflow the stock box to overcome any temparature or ram effects. What's more, the stock sound was not more 'Ferrari' sounding than the individual and much louder individual filters.
    I have now reinstalled my stock air box after removing the sound deadening material which obstructed the airflow outside the reduced diameter of the inflow tract.

    Now, I do not believe any of that crap I used to anymore.

    The stock box was re-installed with the Durable1 short velocity stacks, although I wanted initially to go back to the stock air horns to try to pick up some low end response that was missing with the 'shorties'. I anticipated that even if the flow improved , I would still have a good, but reduced response. The K&N filter was re-installed, and the duct from the side scoop to the airbox was sealed tightly.

    The first thing you notice is the sound change at start-up. With the stock muffled box, the induction sound was nil, and driving around really all you heard was mostly the exhaust sound with some induction noise blessedly without the tinniness of the previous FI. With the Pierce filters the induction sound at idle is a manly rough pulse that later overwhelms the exhaust note at speed with a rough wahhhhhh and a loud hiss on top as engine compartment air is sucked into the 8 gaping 40mm throats, much like a racing car. You can here many small babababababa - just exactly like you would think - all at about 90+ decibels.

    With the new opened airbox, K&N and shorties, the previous rough sound I gues resonates within the large open airbox as the sound is not a distinct pulsating sound, but a smooth low purr on top of the exhaust note. Damn, I thought - how sophisticated - it was as close to a 12 cylinder as I have ever heard any eight. No crap. And at speed - Woo-Hoo! the purr developed a smooth wooooooooom without the hiss on top of the lower exhaust note. I will be stoned for saying this, but kinda like a GTC4. And all at about 80 decibels. It's just so friggin' smooth. And off throttle cruise it's damn near perfect.

    Any doubts I had about lack of throttle response were soon dispelled. It has never picked up so fast at all rpm ranges. While I did not run it up past 6K, you can just tell after driving this car with so many variables that it is breathing like a big dog.

    I gotta guess the cold air ram in conjunction with 12X increase in filter area made a big difference combined with the short velocity stacks. Holy crap. Who'd a thought?

    For all of you with carburetted cars with sound deadening, the difference after removing the obstructive sound material shown in this thread, in my case combined with the inexpensive short stacks, is remarkable for sound and response - especially bang for the buck - and you don't need a dyno to feel (and hear) the difference, although will try to get to one soon as I am wildly curious...

    best to all
    Russ
     
  5. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    Thanks for the update Russ,
    Very encouraging to hear your report. I am hoping to have the engine buttoned up by Saturday night and the car ready to drive by the end of Sunday. I'll be driving it around the countryside the following Saturday.

    Dyno on March 12th. I have last years chart for comparison.

    I hope the jetting works out on mine without having to change emulsion tubes.
     
  6. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    Spasster
    I think 135 mains sounds good - I think you'll feel it with the airbox changes,
    Your ET's are fine.
    Excellent documentation photos on your airbox.
    Good luck!!
    Russ
     
  7. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    16,957
    USA
    Full Name:
    Hugh G. Rection
    DJ,
    This is really going to be interesting!! Looking forward to it. ;)
     
  8. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,683
    North shore, MA
    Full Name:
    THE Birdman
    Damn! Where's my air grinder???

    How hard is it to take that sound deadening crapola outta my airbox?? Sounds like a good weekend project!

    Birdman
     
  9. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    If I make 10 more HP with this I'll be pretty happy, at least for a little while. I'll probably start thinking about Mark's blower again..................................
     
  10. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    Hopefully the weather will be good on the 5th or 6th for a check run up to B'ham:p
     
  11. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    Bird,
    The "crap" comes out with a die grinder in about 15-20 minutes. Getting to it is the time consuming part.

    Pop the rear hatch OFF the car
    Pull the airbox lid
    16 nuts on the V-stacks
    Pull the rubber bellows

    Throw it on the bench and HIT IT!
    Little spot welds hold the screen in. A little Dremel and a cut-off wheel work pretty good.

    I repainted with Dupli-color 1200 degree engine paint and Duplicolor high heat clear found at the local NAPA store.
     
  12. snj5

    snj5 F1 World Champ

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


    Carlisle's BBQ on 6th Ave South, east of medical center. Have some great BBQ for me.

    I never could get the crinkle paint to work well, so I use spray in pickup bedliner which gives a nice tough texture. :)

    best of luck and have fun!!
    rt
    UAB '84
    'There is no great BBQ in Texas'
     
  13. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
    2,149
    way north california
    Full Name:
    chris morse
    Cool Ram air would be more hp productive than hot engine compartment air.

    BUT, I wonder about the air pressure/vacuum in the engine compartment at speed, 40,50,80-100+ mmph. I have no idea what the pressure is likely to be "at speed". For sure, the engine is generating vast quantities of heat, but how does the air flow??? out the top louvers, in at the bottom??? For sure in at the side scoops air is brought in, but is it sucked out at the same or greater rate, yielding a negative pressure in the bay?? or a positive pressure. I recall once reading a post done by a contributor, but he used a psi gauge, which i am supposing may be a bit on the insensitive side.

    any thoughts on this one???

    chris

     
  14. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    #39 snj5, Feb 22, 2005
    Last edited by a moderator: Sep 7, 2017
    Best I can tell, the airflow is from bottom to top, with most of the flow coming over the top of the engine coming over the front bank.
    Note brilliant time consuming professional illustration. With the heat and air flow, there will always be a lower charge density (due to heat) and lower manifold pressure for equivalent throttle openings (due to relative low pressure area due to bootlid louver flow)
    I think this is why the cold air thing works, apparently more than I thought.
    best
    rt
    Image Unavailable, Please Login
     
  15. hanknum

    hanknum Formula 3

    Nov 1, 2003
    2,043
    Santa Barbara
    Full Name:
    Henry
    Kermit,

    The stacks are only 3/4" shorter...I'd guess they were closer to 1.5"?

    What exactly is the "plenum effect"? Can you enlighten me?

    The 2 valve airbox you speak of...is that a FI airbox? I believe the carbureated and FI boxes are completely different.

    Thanks

    Henry
     
  16. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Russ
    You have a captivating literary style. I also like the message.

    For my part, I'd like to say thanks to you and Kermit for identifying this and having the initiative to pull out the dremel tool and attack it. While a new air box is always available, it always leaves a sinking feeling when something somewhat expensive gets bug***ed up. Great job.

    Your sense of the part throttle response of the two stacks would be appreciated. I suspect Kermit's shorties will flow more at WOT, the question is transient response/smoothness and responsiveness of part throttle openings.

    Oh, and which sounds better?
    Back to cleaning up the starter motor. Another one of those "while you are in there" jobs.
    Philip
     
  17. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    #42 snj5, Feb 22, 2005
    Last edited by a moderator: Sep 7, 2017
    Henry - here is a side by side comparison photo prior to installation.

    Philip - Thanks. It's not Tennyson, but "into the valley of the airbox rode my Dremel tool...". Will drive the two velocity stacks side-by-side this weekend, probably with the A/F meter on board.

    best
    rt
    Image Unavailable, Please Login
    Image Unavailable, Please Login
     
  18. hanknum

    hanknum Formula 3

    Nov 1, 2003
    2,043
    Santa Barbara
    Full Name:
    Henry
    Chris,

    I wonder this too. I guess someone needs to do some sort of test to see what the positive/negative pressures are present at certain speeds. Also, it would be good to measure the temps at those speeds. Anyone willing...not sure how you'd do it though.

    Henry
     
  19. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    I can't answer all of your questions but I am positive that the air flows upwards from the road and out the louvers in the top of the rear hatch on my 308. I find sand, bits of leaves and needles on the top of the rear cam cover often. There is no way for it to get there except up through the bottom.
     
  20. hanknum

    hanknum Formula 3

    Nov 1, 2003
    2,043
    Santa Barbara
    Full Name:
    Henry
    Great photos Russ. I also liked your diagram on the air flow, I hope you didn't spend too much time on it. Can't wait to hear your report (and Spasso's dyno #'s) on the difference of the stacks.

    BTW, I almost dropped you a line when I was out in San Antone the beginning of this month for business. Unfortunately, I was only there for a couple days at the River Center next to the Alamo.

    Henry
     
  21. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    "Kermit,

    The stacks are only 3/4" shorter...I'd guess they were closer to 1.5"?

    What exactly is the "plenum effect"? Can you enlighten me?

    The 2 valve airbox you speak of...is that a FI airbox? I believe the carbureated and FI boxes are completely different.

    Thanks

    Henry"

    I'll get to the answers after the following:
    I owe a humble thanks to Stewart Chung for being so gracious in loaning me his '79 308 for the tests. Without his assistance in allowing me to use his Ferrari as a test bed, this post and all it entails would not exist!
    Thanks a Bunch Stewart!

    Now, I just measured a stock Air Horn, and it came out to 1 3/8", while the LPHF horns are 1/2", so I was off a bit on the 3/4" measurement, as it works out to 7/8" in differance. Opps.
    Plenums are used widely in injected motors to allow a more even dispersal of the incoming air, as well as to assist in fuel mixture variations that occur during reversion. When Reversion occurs, as the intake charge hits the now closed valve, and bounces back up the runner, or Carb, it contains fuel. Then as it is pulled inward on the next intake cycle, it gets more fuel added, each time it goes thru. This can wreck havoc on mixtures, as it is "double dipping" at the fuel end and will be very rich. If you ever get a chance to watch a dyno run with open tops, it will appear as a fog over the motor. larger plenums tend to improve lower end performance, and smaller take it to the top end. The Factory added a butterfly valve between the two separate plenums on the 348 to "fool" the motor into thinking it had a larger plenum when that valve was open (3000 to 5000RPM). This no doubt helped smooth the power curve.
    And yes the two different 2 valve motors have distinctly different air filter housings The one I am in developement on is the injected model. IMO it is a very poor design, and backed by the Superflo testing, I would surmise it costs the motor a noticable chunk of power. I would expect that the factory realised this as the 4 valve was coming thru development, as it is considerably different in design.
    From what I gather in looking thru the parts manuals all of the injected 2 valve motors used the same set up. Mondy's included. I hope to get the flow up to the level that the later 4 valve air filter housing is doing.
    HTH
    Kermit
    BTW: A Holley velocity stack is very close to being a bolt on to the Bosch fuel distributor, if you really want flow!
     
  22. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,683
    North shore, MA
    Full Name:
    THE Birdman
    Does anyone know WHY Ferrari added the sound deadening stuff in the airbox? When did they add it? (What year?) If my '77 has it, (it does) then there aren't many possible years that don't. If the car can perform so much better without it, it begs the question WHY? Was this to meet yet another stupid Federal mandate?

    Birdman
     
  23. ham308

    ham308 Formula Junior

    Nov 3, 2003
    358
    NE Switzerland
    Full Name:
    Richard Ham
    This thread is kinda long.., can someone summarise it for a 77 carb GTB (like Birdman's?). The car has sound deadening material but is it restricting the airflow? Air filter seems to get dirty all round, not just by the snorkel.

    If it's restrictive and I dremel it, what will it sound like? Having run the carbs occasionally without any airbox, the noise was just incredible. Way noisier than the exhaust and frankly, PAINFUL. So will it be a lot noisier?
     
  24. ham308

    ham308 Formula Junior

    Nov 3, 2003
    358
    NE Switzerland
    Full Name:
    Richard Ham
    #49 ham308, Feb 23, 2005
    Last edited by a moderator: Sep 7, 2017
    I guess other people may have done this mod as well but it sort of fits in with this thread.

    To save having to take off the bonnet or the boot in order to get the airbox off, I cut the front-most pedestal in the airbox and re-welded it with a bolt in it. This way you just screw the bolt down and the box will come straight out. Hope this is clear.
    Image Unavailable, Please Login
     
  25. Spasso

    Spasso F1 World Champ
    Silver Subscribed

    Feb 16, 2003
    14,612
    Land of Slugs & Moss
    Full Name:
    Han Solo
    Great tip. Don't know why I didn't think of it before. I guess I was too wrapped up in building the snorkle to notice that the only thing preventing removal was the forward stud. I may have to drag the welder out to make the change before I put it back together this weekend.
     

Share This Page