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Stratos induction system on 246GT

Discussion in '206/246' started by Pantdino, Aug 28, 2005.

  1. Pantdino

    Pantdino Formula 3

    Jan 13, 2004
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    Jim
    #1 Pantdino, Aug 28, 2005
    Last edited by a moderator: Sep 7, 2017
    WARNING: THE FOLLOWING POST CONTAINS DESCRIPTION AND GRAPHIC PHOTOS OF POST-FACTORY MODIFICATIONS. THOSE WHO CONSIDER ENZO FERRARI TO HAVE HAD GODLIKE STATUS AND PAPAL INFALLIBILITY SHOULD PROCEDE WITH CAUTION. PLEASE DO NOT READ IF YOU WILL BE UPSET TO THE POINT OF HEART ATTACK, STROKE, OR SEIZURE DISORDER. :)


    I thought I'd contribute to the education of the folks on this list, who may want to know that such a modification is possible.

    In the early 1970’s Cesare Fiorio was Competition Director for Lancia, which gave him access to the 2.4 liter Dino engine as used in the Ferrari 246GT. The Lancia Stratos used this same engine to win the World Rally Championship three years straight, 1974 - 76. However, to do this it needed different carburetors. The stock Weber DCNF carbs on the Dino are very short, and it is my understanding that they were designed especially for this application, because normal carbs would be too tall for the low-lying engine cover. Because of the compromises necessary in their design, 1) their venturis are too short to provide optimal fuel atomization and cannot be changed, 2) the jets cannot be changed easily, and 3) they starve the engine of fuel on left turns. Many Dino owners will have experienced number 3.

    Most mid-engined cars, the Dino included, suffer from trailing throttle oversteer. This means that as you lift off the throttle, the tail moves out. If you are at the limit of adhesion, this could result in the car leaving the road in a spin. Therefore, this left turn fuel starvation issue is not just a nuisance, because it does the same thing as you lifting the throttle.

    The Weber IDF (or DFI) carb is essentially the vertical version of the DCOE. Not only is this carb taller than the DCNF, but the Stratos intake manifold is taller, to provide more torque at lower revs for rally use. Between 1971, when it left the factory, and 1974, when it left Italy, Dino 246 number 2840 was converted to the Stratos induction system. Some creative individual was faced with the challenge of modifying the engine cover to allow the air filter to protrude above the stock engine cover. This was done by making a fiberglass copy of the raised area in the cover and mounting it 5 cm (2 “) above the cover, the cover itself having had an aperture cut in it to allow the air filter to protrude through it. Because of the shadow created, the air filter is not visible within. An air filter assembly with a velocity stack for each carb throat was created, these being brazed to a flat alloy plate that formed the bottom of the air filter unit. A K+N trapezoidal filter surrounded each pair of carb throats, with another flat alloy top plate sealing the upper surfaces. Recalling the plexiglass velocity stack covers on the hoods of the great Ferrari front engined racers of the 50’s and 60’s, I made a Lexan top plate to replace the alloy one. Combined with a single Fram air filter element, the velocity stacks can now be seen without having to remove the top plate.
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  2. PaulK

    PaulK F1 Rookie
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    That is indeed very interesting, and thank you for sharing. I would love to see some preformance numbers with this new found torque and added power.
     
  3. Kram

    Kram Formula Junior
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    Interesting! Is it harder to get Stratos carb parts than Dino?
     
  4. Pantdino

    Pantdino Formula 3

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    Since they only made 400 Stratos and about 4000 Dinos I suspect Stratos parts are indeed harder to find.

    I did have the car on a chassis dyno to jet the carbs, but chassis dynos are only good for tuning, not for absolute number comparison. So I don't know how the HP and torque numbers compare to a stock system. And my car has had the cams reground, so that would be a confounding variable anyway.
     
  5. stratos

    stratos Formula Junior

    Dec 9, 2003
    637
    Switzerland
    Stratos inlet manifolds are manufactured in Italy as we speak. They're expensive but do procure advantages over the original 246 design.
    IDF carbs and parts are easily source.
    Finally no need to do the "not so tasteful" engine lid modification.
    Qualified aluminum craftsmen will be able to make an engine lid identical to the original 246 item with the exception that the bulge is taller to accomodate IDF carbs and the longer manifold that accompanies them. Very hard to tell the difference unless you put an unmodified 246 next to a modified one.

    Cheers.
     
  6. synchro

    synchro F1 Veteran

    Feb 14, 2005
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    The original Weber carbs were well enough to allow flowthrough with the big changes here seem to be the manifold and the velocity stacks. I'd like to see what this does to the bottom end as my Dino is really a rev'er and lacking in torque from a stoplight.
     
  7. Davato

    Davato Guest

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    #7 Davato, Aug 30, 2005
    Last edited by a moderator: Sep 7, 2017
    Hello,

    The Stratos GR4 have different type of inlet manifold and carbs.

    The early cars had 44 Webers and were produicing 240/250 HP.

    The late cars had 48 Webers for 260 to 280 HP at 8000 rpm for the very best engines.

    They also had high lift cams, high compression ratio pistons, modified sump, connecting rods, crank etc ...

    Maglioli and Facetti built some of them. Though being very powerful and loves high revs a GR4 still has a lot of torque, it doesn't make the car difficult engine.

    A nice one !

    The inlet manifold for GR4s is available in Italia and the carbs are not so difficult to find.

    The Dinos that raced at Le Mans Historic last year had Startos GR4 type engines, a frend of mine has a Dino with a 250 HP engine, it's a very nice driver !

    Click the following link to find a report about my Startos in th Monte Carlo 2004.

    http://www.florentmoulin.com/web/evenements-_00.01.06.00.0000_topfiche_1.html

    All the best.


    Florent
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  8. stratos

    stratos Formula Junior

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    The connecting rods where standard Dino items even for works Stratos entries.
     
  9. synchro

    synchro F1 Veteran

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    48mm carbs?
    Yowza!
     
  10. Davato

    Davato Guest

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    ... wrong they are lighter and stonger.

    A real Group 4 engine can revs very high, 9000 rpm is possible ( though not suitable ) with original ones the fate of the engine and the crank would be sealed.

    Regards.

    Florent
     
  11. stratos

    stratos Formula Junior

    Dec 9, 2003
    637
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    I maintain that Gr.4 cars had standard conrods. They were only lightened. This information was personally passed to me by Claudio Maglioli.

    12V dinos reached a max output of 282bhp at 8400RPM in the Stratos.
    24V dinos reached 307bhp at 8700RPM in the works cars.

    But this is not the place to discuss Stratos specifics as it's a Ferrari forum, right?

    Regards.
     
  12. bigodino

    bigodino F1 World Champ
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    #12 bigodino, Aug 30, 2005
    Last edited by a moderator: Sep 7, 2017
    I personally don't mind a discussion about Stratos - I love them! And they have a Ferrari connection.

    Anyway, here's a picture of s/n 06748. If I remember correctly it had higher velocity stacks than stock. It looked funny with the bonnet permanently open (mounted on extensions).

    Ciao, Peter

    Edit: found a picture with the bonnet open.
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  13. Pantdino

    Pantdino Formula 3

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    The Dinos that raced at Le Mans Historic last year had Startos GR4 type engines,
    Florent[/QUOTE]

    Do you have a photo of these Dinos that ran GR4 Stratos engines? How did they deal with the induction system height problem?

    Jim
     
  14. Pantdino

    Pantdino Formula 3

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    Actually I find this modification reasonably pleasing to the eye. Yes, a metalworker could make a cover with the center portion 5cm taller, but it's going to look like a big lump on the othewise svelte design. The visual effect could be improved by extending the bulge onto the trunk lid, but then you're really changing the look of the car.

    The fact that you have seen modified engine lids that are not noticeable means little, as we don't know how tall the velocity stacks, if any, were on those cars. I'm pretty sure the stock Dino airbox has no stacks at all inside it to minimize height, and those cars may be the same way.

    Also, one advantage of the raised "hat" style is that the engine is sucking mostly cold air thru the gap under the hat rather than hot air off the surface of the engine--most of these modified systems don't have a "snorkel" tube sucking cold air from the side of the car like the stock system does.
     
  15. Slim

    Slim Formula 3

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    I suspect they could rev higher than that. I rebuild my 2400 dino engine myself with larger valves and custom high comp (claimed 10.4:1) forged pistons, new springs, etc. and I reved it over 8000rpm almost daily. One would hope a race engine would rev much higher. BTW, it is indeed suitable to rev it that high (if it were possible) even on a stock dino engine while in lower gears as the torque put to the rear wheels is more at 9000rpm in 1st gear than would be put to the rear wheels if one shifted up to 2nd gear. Similar for the 2nd vs. 3rd gear shift point. After that, because the gear ratios get closer, one can shift earlier and be making more torque in the next gear.
     
  16. Davato

    Davato Guest

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    Hello,

    The Stratos has enough Ferrari blood to figure in this chat I think !

    I recently visited a frend who was rebuilding the engine from its original GR4, the connecting rods were not standard. They were different engine builders for these cars and they raced for almost 10 years.

    Anyway a Startos and a GR4 is a fabulous car.

    Regards

    Florent
     
  17. Davato

    Davato Guest

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    #17 Davato, Aug 31, 2005
    Last edited by a moderator: Sep 7, 2017
    Richard,

    This is the kind of thing that happens with the standard ratios gear box.

    GR4s have dog box with close ratios, when you shift, you are always at the suitable rev, first gear is very looooooooong !

    A nice engine has a lot of power from 4500rpm to + 8000rpm that is important and don't really need to take more.

    Once again one of the best quality of this engine is the torque regarding the capacity 2,4 liter. In Rally sometimes torque is more important than power, the GR4 one was designed for that.

    Last, some late engine used fuel injection ! especially IMSA ones.

    All the best,


    Florent
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  18. Slim

    Slim Formula 3

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    Ah! Of course! With close ratios things change. Thanks for pointing that out.
     
  19. stratos

    stratos Formula Junior

    Dec 9, 2003
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    The Stratos Gr.4 gear ratios were:
    Gear ratios - speed at 8000 RPM (depending on cascade gear set):
    1:3.143 - 56.3 or 70.38 or 82.62 Km/h
    2:2.24 - 78.99 or 98.74 or 115.92 Km/h
    3:1.762 - 100.43 or 125.73 or 147.37 Km/h
    4:1.417 - 124.88 or 156.1 or 183.25 Km/h
    5:1.154 - 153.34 or 191.67 or 225.02 Km/h

    The Stradale and standard Dino ratios are:
    Gear ratios - speed at 8000 RPM:
    1:3.554 - 64.83 Km/h
    2:2.459 - 93.69 Km/h
    3:1.781 - 129.36 Km/h
    4:1.32 - 174.54 Km/h
    5:0.986 - 233.67 Km/h

    Needless to say that but using the shortest ratios a Group4 Stratos would outaccelerate an F430 to 100mph...

    I'll post pictures of the modified engine lids today.

    Cheers.
     
  20. stratos

    stratos Formula Junior

    Dec 9, 2003
    637
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    #20 stratos, Sep 1, 2005
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  21. stratos

    stratos Formula Junior

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    #21 stratos, Sep 1, 2005
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  22. yasmin

    yasmin Formula Junior

    This sounds interesting.
    Please excuse my naiivity, but is it 'that' easy..just carbs and manifold etc

    If so, where can I get the parts.

    thanks.
     
  23. stratos

    stratos Formula Junior

    Dec 9, 2003
    637
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    You need:
    - Replica Stratos inlet manifold (Originals are near impossible to find). Can be sourced in Italy
    - Set of IDF of your choice (40-44 or 48) depending on the state of tune of your engine. Can be sourced easily at carb shops or off EBay
    - Mofidied engine lid to allow fitting the above

    You cannot fit velocity stacks as with this setup but can modify your current airbox to fit.
    The additional advantage is that you won't suffer fuel starvation on left hand corners...

    Cheers.
     
  24. Pantdino

    Pantdino Formula 3

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    Beautiful metal work!

    Did you have completely new engine and boot covers made, or were the originals modified?

    If the latter, do you have a cost estimate?

    The only disadvantages of this as opposed to what's on my car relate to the fenestrated vs. non-fenestrated cover over the velocity stacks. The fenestrated system will allow more cool air to the intakes and more of that sweet induction noise out for me to hear. Of course, some may consider the latter point to be a disadvantage. :)
     
  25. stratos

    stratos Formula Junior

    Dec 9, 2003
    637
    Switzerland
    The boot cover is original, only the engine lid is new, hammered out of aluminium sheet by skilled technicians. I think the cost is around 2K USD. The trouble however is that no two Dinos are identical. There are differences up to half an inch between cars in the bodywork of that area. I guess that since they were made by hand the bodyworkers where adjusting parts on every individual car?
    Bottom line, you can't have it made remotely...

    It's true you can't use velocity stacks. However there's no hot air issue are you are still using the original airbox which is fed fresh air by the left scoop.
     

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