I was just thinking about how the technology of variable turbine geometry for turbos has been around for a while to reduce turbo lag but nothing has really been done to solve the long/short runner length tradeoffs in intakes. Do you think it is possible to do such a thing by either shortening/lengthening the runners or widening/narrowing their diameters based on rpm like the previously mentioned turbo technology? If not, why? Or, if so, is anyone currently working on this?

 

You mean like the Integra GSR? The engine is the b18c1 and uses dual runners in the intake manifold. I think it uses some sort of butterfly valve, but I haven't read up on them in a long time and may be wrong.

 

There are a lot of OEM designs that use two different intake port paths to get what you are talking about. F1 WAS allowed to use variable length trumpets to do this, it's the best way to go about it, but it's better to change the length over the cross sectional area.

Bret

 

I'm pretty sure the Ford SHO V6 motors did this. Not sure if the SHO V8s.

Didn't the LT5 have something like this too, or was each runner for each intake valve?

 

most oem stuff only have two diffrent lengths. i think they switch from long to short back to long as this gives the best power and torque over the whole range!

now F1 was much more complexe, using constantly changing lengths to match the sound pulses of the inlet air. this ment they where getting 100%+ cylinder filling N/A!!! and why they made soooooo much power on such small engines.

this would be very hard to do, as you would need to keep testing and testing to get the best inlet lengths of each rpm.

i think i read about some using stepped inlet runners to get rid of the sound wave and stop the bad effects it has at certain rpms! that might be worth a look into for the racers!!

thanks Chris

 

How are these variable lengths controlled though?

 

Most if not all OEM designs don't have continuously variable runner dimensions, just 2 different options--long/small and short/big. I'll use the SHO for example, though a lot of foreign manufacturer's have been doing this. At low RPM, the engine breathes through longer, smaller diameter runners, and then once at ~3500, the vacuum operated butterflies blocking off the short runners open, thus the engine breathes through both runners (Though most air comes in through the shorter fatter runner--least resistance). This allowed the engine to make a very wide torque curve, with a strong high end.

The LT5 was different in design. Each cylinder had 2 runners, but both were the same length. With the control key off, each cylinder would only use one intake runner and one injector (Making about 285hp). When you flipped the key to full power, it opened the butterflies and allowed each cylinder to breathe through 2 runners and use 2 injectors. This bumped, rather smashed, power up to 375-405, depending on year.

While these intakes are good, IMHO they are very overrated. Most engines we're messing with today have more than adaquate low end. Why worry about tuning, the added weight, and the complexity of dual runner when you don't need the low end power at all? Just stick to tuning for the upper RPM range, and leave it be. The low end torque gains just aren't worth the effort.

For example, I play with the GM 3.4l DOHC V6s, the engine created to equal the SHO Yamaha V6. Both motors are pretty much equal in performance. The power levels are pretty much equal across the board. The only place where the SHO really makes more than 5-10whp is after 6,000rpm, since our motor was tuned for the midrange with long runners and mild cams. So that huge and complex intake, and the only place it really made a difference was after 6,000rpm. , pulling to 7. On the other hand, if someone could defy my thousands of attemps at a continously variable dimension intake manifold, I think it is VERY worthwhile. Combine that with an awesome EFI (Individual cylinder WBO2 trimming), VVT, and a CV header, and you'd have the most advanced internal combustion engine ever IMHO.

 

It isn't difficult to get over 100% Volumetric Efficiency. Our FSAE engine saw 120+ % on the dyno with fixed lengths and an intake restrictor. The reason F1 made so much power from a small displacement is because they rev the snot out of them. Horsepower is proportional to rpm * displacement * cylinder filling pressure. With rules mandating everything else stay constant, revs had to rise. The best runner length to use for a given rpm can be calculated easily enough. The only testing needed is to verify the calculations.

F1 used sliding trumpets to lengthen and shorten the intake tract and increase the powerband size. They weren't getting 100+% VE at every rpm though. The camshaft decides the powerband more than intake and exhaust tuning. I know BMW made an intake manifold for their street cars that utilized constantly variable runner lengths. Several years ago, last time I was at the FSAE compretition, at least one of the teams built a manifold that utilized it as well.

Al

 

Here's an article for BMW 7 series that Al is thinking of.

http://www.canadiandriver.com/articles/jk/020213.htm

You'll find most of what you need in that write up.

If I remember correctly, there are some motorcycle engines that have this
technology incoporated as well.

 

Interesting write-up. I don't fully comprehend how the intake manifold works, I want to see cutaways and pics of it. Maybe I'll run by the BMW dealer and see if/when they get a 7-series that needs intake gaskets or something.

That being said, what a waste. All of that technology, adding complexity that has the potential to fail and leave the vehicle stranded, all for 75hp/l? That low of a specific output is nothing special nowadays, especially when BMW themselves have at least 3 engines topping 100hp/l, without variable intakes, and with traditional throttle plates. So the advantage must be gas mileage, but I bet the I6 gets equal if not better, all with static intake runners and throttle plates. Furthermore, it makes more power still.

 

Here are some numbers to compare. Whether it's a waste for the money,
that remains a discussion.

2005 LS2 6.0L

Engine type OHV V-8
Aluminum block and heads
Bore x Stroke 4.00 in x 3.62 in
Compression ratio 10.9:1
400 HP @ 5200 rpm
395 lbs./ft. @ 4000 rpm

Fuel Economy 28 MPG Highway (Corvette with 6 spd manual).

2005 BMW 4.4L

DOHC 32 valve
Aluminum block and heads
Bore × stroke 3.62 in × 3.26 in
Compression ratio 10.00:1
333 bhp @ 6,100 rpm
330 lbs./ft.@ 3,600 rpm

Fuel Economy 34 MPG Highway (BMW 745i 6 spd auto).

(from one source) If you find differences, post'em up!

 

Bumping this thread from the dead.

Does anyone have any good pictures/drawings/discriptions of how the valving works that closes off the shorter runners at low RPM on the dual runner setups?

Or any comments on how adventageous a dual runner setup would be on an FI application?

I know some of the new ford Focuses run these, could anyone name some other cars that do also? I would really like to get my hands on one to see how it works.

Im designing an intake for a 600cc turbo charged motorcycle engine, thought these looks really interesting.

 

On the SHO and most other dual runner manifolds, it is pretty simple. Each cylinder has two intake ports, two tracts if you will. One tract is shorter than the other. Below 3500rpm (On the SHO), the engine only breathes through the longer runners, the short ones are closed off via a throttle plate located in the runner. At ~3500rpm, the throttle plates open via a common shaft for each side, and the engine breathes through the short runners. I believe at high RPM the engine can breathe through BOTH runners, but most of the air will come from the shorter one (Less resistance). I believe the plates in the runners are vacuum operated.

They would be advantageous, to a point. Remember, when you have FI, flow equals power. There is no arguing that. Harmonics don't matter. The bigger and shorter the runners, the more power you'll make, period. However this also has a negative affect on off-boost power, and spool time for a turbo. Having a dual runner manifold would enable you to have really good off boost response and torque, and would spool a turbo faster. But the negative would be a loss in on boost power, assuming the single runner manifold flowed more. But if the dual runner manifold still flowed more (Possible having two runners per cylinder), then we can safely say it'd make more power.

The Tauras SHO is the only car I can think off off hand. The LT5 5.7l DOHC 32v V8 by GM had a similiar setup, but good luck finding one, and then paying for it.

Stick with the motorcycle's Independent throttle body setup if it has one. Turboes react to ITBs really well (Smooth power and great response, plus a lot of flow).

 

i have just seen how the Farrarei one works on the 360 and 430. they run two inlet Plenum that have two cold feeds for nice fresh air! then each cyclinder has two inlet tracks, one running toi each of the Plenum. i assume half way down each inlet track is a butterfly that can be electronically opened and closed. this system give you a short and long runner length. and quiet a neat solution to!

thanks Chris.

 

Ya so basically the same as the 10-15 year old SHO, except the SHO has a single plenum/throttle body. But it looks like dual plenums, they are just connected. I doubt they have the butterflies on the long runners, I bet at high RPM the engine can breathe through both runners. I see no reason not to do this, just added airflow.

You can kinda see them here. The 6 on top are the short runners, which are on the same bank side as the cylinder itself. The 6 runners that enter the plenum lower than the other 6 are the longer runners, and they cross to the other bank side. You cannot see the plates, they are in the lower intake manifold. The Ford Contours with the Duratec 2.5l and SVT 2.7l had dual runner intakes, nearly an identical manifold to this SHO piece, just visually different.

 

Audi has been doing it for several years, the actually have 3 different runner lengths, i am trying to attach a few pics for you

 

That manifold is a lot like the LSX intakes, just as the runner wraps around the plenum, it has different valves that open to shorten the runner. Really not a bad design, but I still think it isn't worth the complexity/price, especially if one has to be custom built.

 

Design I imagine.

Runners extend into the plenum like some of the newer LS1 designs, with bell mouth entry and all.

Plenum is a big **** bread box which covers the entire arrangement and not close enough to any runner to cause air distribution issues.

Runner can extend and shorten similar to a "trombone". Figure runner that can trombone max 4" or 5", to max the tq curve over the range.

If runners have butter fly per runner, the butter fly of course is up closer to the head and the "trombone" portion is after the butter fly exiting into the plenum.

 

Here are some animations and a video of the variable intake on Yamaha's 2007 YZF-R1.
http://www.motorcycle-usa.com/Articl...ID=3819&Page=1
http://www.yamaha-motor.com/sport/pr...nnovation.aspx
http://www.r1-forum.com/vids/07R1_stacks.wmv

 

Very interesting. Unfortunately the link for the video does not work.

Judging from the animation and the pic below, I do not think this system is fully variable, I think it is just a dual-stage. This hasn't been presented in motorcycles before because of space and weight contrainsts. From what I can tell, the top section just elevates at high RPM, and the engine breathes through the shorter runners only. This doesn't surprise me, motorcycle engine technology is always behind automobiles (Again, space, weight, and cost).

That being said, it presents another method of getting a truly variable runner length. It really is quite simple. Have a "tube inside of a tube," and as RPMs raise, the upper tube, which has a velocity stack on top, slides down into the lower tube. Really quite simple. However this does present problems. For one, the runner diamater can't change. And since this tuning would be for high RPM, the diamater would favor the higher RPMs, thus being really large. Two, there would need to be a seal between the two "tubes." All that being said, I think this could work. It can be set up mechanically (Where a solonoid slides the tubes along a tract linearly to RPM), or electronically with an extensive ECU (Where the tubes truly are tuned for RPM/Throttle position/outside conditions--though probably still set to slide along a tract).

I just thought of another problem with this. Motorcycles place the injectors Formula1 style, clipping to the velocity stack, barely inside of the intake runner. Thus there would need to be a way to make the fuel line to where it could move up and down with the upper tube. Since the extension would only be 2" max, some sort of flexible line should work fine.