I was at the pick a part and there was another 3L Mivec diamante there (3rd gen shape) and the intake plenum was off. unlike the 3/3.5l ones we have, it has two sets of inlet runners on the inside, one curves around underneth to join up just after the top row. this top row are closed with a row of throttle body style plates. the first row are longer so im assuming they are for low revs for low down torque and the shorter runners are opened when mivec hits to increase flow and shorter runners are better for top end power. has anyone else seen these plenums before, and would there be an advantage to using them on our sohc engines with a switch of some sort to open the short runners at a set rpm. just brainstorming, will try get pictures.

it is definitly not a new design or theory, for example toyota have been using it since the early 80's..

1983 when toyota made the first 4AGE, known as the 'bigport' 4AGE, and the device is known as T-VIS (toyota Variable Induction System), had a dual runner inlet manifold, and a set of butterfiles that closed below 4200-4400 (depending who you talk to) and opened up above that mark.. a slight kick in the bum would be felt in the transition, but nothing like VVTL-I or V-tec systems.. just a bit more noise was generated, and willingness to rev..

the theroy was to have 2 engines in one.. the 4AGE back in 1983 in the AE86 Sprinter made about 94-96kw (agian depending on sources) and was used in our aussie AE82 corolla in later years (down to 88kw),

they had a massive inlet port, and to keep air speed up at low RPM, the butterfly would close, giving the engine low end power/torque, whilst still giving an agressive high revving top end with a large port..

this was later revised in the 90's for the 'smallport' head, which actually shits all over the bigport in terms of flow etc etc..

other engines used the T-VIS like the 3SGE and 3SGTE, 7M variations also..

plenty of other manufacturers have used it before toyota, and many after toyota, nissan had it on thier CA18DET's..


EDIT - toyota even used ACIS, which was more about volume, than changing the actual runners.. best i can describe it would be a 'chamber' that added 'volume' to the inlet tract, which also aided in Drive by noise emmisions..

I'd say there would be a difference if the runners can flow enough to meet the engines demand. The EL-AU Falcons used an inlet system like this, and work on them, so reason it won't do the same for a Magna.

Basically with a road cam they are a waste of time unless the car is very heavy and the engine small and revvy and gear ratio spread is useless.

If you are trying to make a big cammed engine a bit more roadable then they are OK but a full variable length system is far better.

They are a good advertising tool so were popular with the Japanese from that angle. European makers use them too but usually to get a screamer 2ltr 145kw/200hp engine street useable in a 1300kg car, or to help a 2ltr 4 cyl pushing a 2 tonne BMW. As well as low rpm torque they also help fuel economy. Some systems block one inlet valve to increase mixture motion and help low rpm burn/emissions.

Cheers,
Alan

the same plenum or similar one can be found on the 1st gen diamantes and our 2nd gen magnas (except throttle body is on the opposite side), you can actually feel the switch between the short and long runners based on my experience with the KS i have.

Yes, the 2nd gens 6g72 had them, they are known as variable length inlet manifolds. Long path at low revs to increase torque and short path at high revs to maximise power. THe 3rd gen 6G72,6G74 and 6G75 got rid of them.

Ahhh ok thanks guys, it looked quite cool inside, the longer bottom set of runners were capped in a plastic trumpet within the plenum. would using it and removing the butterflys result in a streetfighter like plenum, ie two sets of runners with different lenths? be interesting to try, but the throttle body is on the opposite side. if you guys want ill get a pic...

Basically with a road cam they are a waste of time unless the car is very heavy and the engine small and revvy and gear ratio spread is useless.


Why are Ford using it on their low rev large displacment 4L I6?

i think they are. not sure about current models tho.
was introduced in the EF series,
"intake manifold was changed to include a dual length system which involved intake runners of two different lengths and a valve to switch between the two"

Why are Ford using it on their low rev large displacment 4L I6?

Do you mean "are using" or "were using"? I wasn't aware that the 4 valve DOHC engine has variable length runners. In the SOHC engine it was to cover the big gear spread. I think the auto was only originally 3 speed and the car was heavy. It was later when the 4 speed came along.There were NVH concerns too that the dual runners may have helped with reducing certain resonance frequencies. Jaguar were employed to redesign the sump and a few other bits for that reason. Or there may have been emissions issues. Ford regularly had trouble getting through tests. Runner design can help get through but can knock top end performance unless free breathing secondary runners are added.

Cheers,
Alan

Yes, the 2nd gens 6g72 had them, they are known as variable length inlet manifolds. Long path at low revs to increase torque and short path at high revs to maximise power. THe 3rd gen 6G72,6G74 and 6G75 got rid of them.

These manifolds were also used on the V6 pajeros. I'm not sure which engine variant this was on but I had one in at work once that had an LPG backfire in the inlet manifold that bent all of the throttle bodies at a 90 degree angle.

Do you mean "are using" or "were using"? I wasn't aware that the 4 valve DOHC engine has variable length runners. In the SOHC engine it was to cover the big gear spread. I think the auto was only originally 3 speed and the car was heavy. It was later when the 4 speed came along.There were NVH concerns too that the dual runners may have helped with reducing certain resonance frequencies. Jaguar were employed to redesign the sump and a few other bits for that reason. Or there may have been emissions issues. Ford regularly had trouble getting through tests. Runner design can help get through but can knock top end performance unless free breathing secondary runners are added.

Cheers,
Alan

Sorry meant to say "were" as in the EF/L-AU. They had by this stage already been running the 4 speed automatic gearboxes. These engines made a fair wack of torque int he low-mid range rpm band, so had no troubles with the tall gearing witch was mainly due to a low final drive ratio. I actually played around with this intake on an AU falcon and while there definitely a little loss of low down response with the manifold stuck in the short runner setting, it didn't really effect how the car drove.

Do you mean "are using" or "were using"? I wasn't aware that the 4 valve DOHC engine has variable length runners. In the SOHC engine it was to cover the big gear spread. I think the auto was only originally 3 speed and the car was heavy. It was later when the 4 speed came along.There were NVH concerns too that the dual runners may have helped with reducing certain resonance frequencies. Jaguar were employed to redesign the sump and a few other bits for that reason. Or there may have been emissions issues. Ford regularly had trouble getting through tests. Runner design can help get through but can knock top end performance unless free breathing secondary runners are added.

Cheers,
Alan

The BA/BF 4L non turbo falcon used a dual "path/variable length" inlet manifold with the switching butterflies in it to make it a short or long tract. The BA model also had dual variable cam timing (D-VCT) which on the BF models became dual "independant" variable cam timing (DI-VCT in ford speak)

When ford fitted the dual length plenum on the EF/EL falcons they had the 4speed BTR auto in them (was actually part of the "EA" model falcon update in 1990)

Ahhh ok thanks guys, it looked quite cool inside, the longer bottom set of runners were capped in a plastic trumpet within the plenum. would using it and removing the butterflys result in a streetfighter like plenum, ie two sets of runners with different lenths? be interesting to try, but the throttle body is on the opposite side. if you guys want ill get a pic...

Madmagna has proven with the butterflys out it actually decreases performance (of a SOHC 12v)....actually come to think of it......sounds almost like the SF

You guys could probably get it working using a TR auto ECU, give it a crank and cam sensor inputs, so it thinks its running a motor, and use the VICS outputs to control it..

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You guys could probably get it working using a TR auto ECU, give it a crank and cam sensor inputs, so it thinks its running a motor, and use the VICS outputs to control it..

Could get it working with somthing like a cheap Jaycar kit for a shift light. That way you can adjust the switch over point to suit the best performance.