What is the advantage of Ford's SHO Split-Port intake manifold? 1

[dbmonkey]

As you can see in these pictures, Ford (with the help of Yamaha) produced this intake manifold where each cylinder has 2 intake runners of different length.
Engine info: 1989 to 1995 Ford SHO engine, 3.0L
What is the advantage? Do any other engines do this? Is there a valve enabling and disabling half of the runners? Is each runner routed to a single intake valve, and if so are the intake valves of same size, orientation, and function?

Thanks in advance!

 

[GregLocock]

https://www.google.com/url?sa=i&rct...ZknH4Nw7X_2yM7lymM-F6lVQ&ust=1393304955069658

There might be a butterfly in the branch of the plenums of the one you posted.

It gives you a fatter torque peak.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[dbmonkey]

Now that I look closer, it does seem that there is a vacuum operated valve on the shorter runners.
Could someone confirm this?

 

[yoshimitsuspeed]

http://en.wikipedia.org/wiki/Variable_length_intake_manifold

 

[MikeHalloran]

It has to do with acoustic resonance producing torque peaks at certain speeds.
Long runners favor low speed, and conversely, so having two switchable runners of different lengths gives you at least two torque peaks. ... and probably at least two torque valleys also, but if you put the peaks where you can use them and push the valleys to where it doesn't matter, you can gain a performance improvement over a simple manifold of fixed geometry.

BMW produced a fairly complicated scroll- style intake manifold that changed the effective length of the runners, continuously, by rotating a part of the manifold with an electric motor, theoretically allowing the engine to run at intake resonance, and hence best torque, over much of its rpm range.

Fancy intake manifolds are more common than ever before, but there are so many features contributing to the performance gains in modern engines that it may be difficult to separate out the gains associated with any one feature. ... and the guys who really know this stuff have substantial commercial incentive to reveal as little as possible, about anything.



Mike Halloran
Pembroke Pines, FL, USA

 

[yoshimitsuspeed]

I doubt the short runner has anything to do with resonance since even 10 in of runner would just barely put the fourth harmonic within the stock power band.
The long runner may be tuned for some target range but I would guess the short one would be more for open unrestricted flow.

You could have some fun with long staggered runners though.
These are some super rough numbers just to throw a little theory on the wall.

With say one 18 in runner and one 24 in runner you could alternate between the two something like this.

24 in 4th harmonic 3000
18 in 4th harmonic 3600
24 in 3rd harmonic 4000
18 in 3rd harmonic 4700
24 in 2nd harmonic 5500
18 in 2nd harmonic 6600

Only trouble is switching between the two runners would be a nightmare which is why most systems like this only actuate one.

I have thought it would be fun to build some sort of telescoping manifold some time.
That is far better but also not as cheap or easy.

 

[SomptingGuy]

Before the FIA banned it, intake runners on F1 engines were known to vary by up to 30mm in length across the (very narrow) operating speed range to maximize BMEP. Actuated by stepper motors.

For flamboyant intake systems with switchable air path lengths, take a look at some of the offerings from Ferrari in their V8 engines of recent years.

But the ubiquity of the turbocharger is killing off the art of intake system tuning now.

- Steve

 

[GregLocock]

I agree the short pipes tend to be untuned.

Here's a dyno graph comparing a log manifold with a BBM

http://i204.photobucket.com/albums/bb160/H2Micr0/Misc/XR6BBMvsLogDynoGraph01.jpg

Careful study of the vacuum actuator reveals that at idle both pipes are used, and then above idle the long ones, and then at something over 3000 it reverts to the idle setting.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Lou Scannon]

But the ubiquity of the turbocharger is killing off the art of intake system tuning now.- Steve

Quite true. With a boost-controlled system, the torque curve can be tailored to an ideal shape for driveability and [at least mainstream] driver satisfaction, doing away with the need for compromising with a peaky/lumpy torque curve that probably isn't appreciated by most drivers.


"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[Tmoose]

Danny Ongais ( earned nick name was "on-the-gas" ) was a driver who enjoyed success in a wide variety of motorsports.
Drag racing champ in the 60s, through the 70s and 90s he competed in open wheel racing like CART, USAC, INdy RacingLeague, Indianapolis 500, and even dabbled in Formula 1 for a few years.

One of his last rides was at Indy in 96 ( he was 54) where he took the (stock block) Buick Menard Lola from last place to 7th overall. Various years turbo'd stock blocks were allowed up 55 inches of boost.

I believe one of his street cars of choice back then was a Porsche 911 Turbo (930). The controls available to broaden and smooth the power back then were a bit limited compared to today, as is described in this 2013 refresher road test -

http://www.caranddriver.com/reviews/1978-porsche-930-turbo-tested-today-review

,
Others are a bit more blunt -
" Legendary turbo lag and an associated reputation as the scariest handling Porsche 911 of all have made the 911 Turbo into a legend."

http://www.historicracer.com/driving-reports/911-turbo-a-seventeen-point-history/

Not too surprising then Danny Ongais comment back then to one of the car mags was " nobody can drive those things fast ."

Compare that to the computer generated flat torque curve and resulting progressive power everybody enjoys today.

http://giantmaw.com/Photo Album/Image Library/Cars/BMW/n54/335i20TT20Torque20Power20Curves.jpg

Or, the hard hitting jump in power of a peaky piston port mx bike on page 52 here -

http://honda-elsinore.alp-sys.com/publications/magazine/Cycle/73Mar-cr250m/73Mar-cr250m.pdf

The sharp throttle response of this bike would only add (significantly) to the feeling.

 

[Tmoose]

Passive version of inlet tuned for broader or less holey torque curve -

http://www.speedhunters.com/wp-content/uploads/2011/06/one32_YP5q_7.jpg

http://www.performanceboats.com/gallery/data/500/Crower_Injectors.jpg

Chrysler's sonoramic manifolds of 50 years ago came in 2 versions.

http://www.forwardlook.net/forums/forums/get-attachment.asp?attachmentid=60015

Originally with the center divider all the way to the carb, about 30 inches long for lower rpm power.

http://img.photobucket.com/albums/v628/BigBlockMopar/1960ChryslerNewYorker/RamInduction.jpg

Then they cut the divider back so the tuned length was only about 15 inches long.

http://www.allpar.com/mopar/images/sonoramic4.jpg

 

[Lou Scannon]

In the version I've read, both versions were available simultaneously, the long ram version being standard in the applicable models/options, aimed at the street driver, and the short ram version being optional, aimed more toward race driving.
This was the situation at least with the 1960 & 1961 Chrysler 300, the model in which this feature was first introduced by Chrysler, if I'm not mistaken.
The same concept was also applied to the Dodge Dart and Plymouth Valiant, with the Slant-Six "Hyperpack" option, which if I recall correctly, allowed Chrysler to more or less sweep the short-lived compact NASCAR series in the early sixties. Naturally, there was more to the Hyperpack option than simply ram-tuned intake manifolding.


"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[NormPeterson]

Here's the page out of the factory shop manual for Mazda's Variable Resonance Induction System for the 2.5L V6 that was available in 1995's 626 and MX-6 and Ford's Probe.

You absolutely can feel the difference when either of the solenoid valves stops working and you're running along one of the "wrong" torque curves.

And yes, this engine will safely rev to 7500.


Norm

 

[NormPeterson]

Note that torque improvement in four distinct rpm ranges is possible with the TWO butterfly arrangement.


Norm

 

[GregLocock]

Excellent

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?