Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Intake developments. Porsche vs. Yamaha

Chris,

I think I may have found exactly the patent you were looking for. It is a Japanese patent. You can find it at: http://www.delphion.com/cgi-bin/viewpat.cmd/JP62210218A2

Chris,

Looks like EWF found something pretty close.
From the Taurus SHO guys, here's the one
that they forwarded to me...

Patent #4766853 http://www.delphion.com/cgi-bin/viewpat.cmd/US04766853__

Still looking for a message post that I can't
quite locate that talked about this...

Will post when I find it..

OK Chris, here it is. Keep in mind it was
geared for the boys with SHOs. BTW, guess
I didn't get the brains of the family...


Well, it's more clear now that gains can occur with a cross-over & valving.
How much? I don't know but there will be a gain.

To find out the gains, though, one of you will need to be the guinea pig.
Do this at your own risk, obviously.

To get right to the point, if you guys are interested in this, the next
time you get on a dyno someone try two runs. One with the crossover as
is and one with it plugged. Theoretically you can either plug the
crossover in the middle (tough to do) or cap the end of each plenum. Do
so with car, however, as duct tape won't cut it. What you WILL see is
that low-end torque will INCREASE, as will high-end power also INCREASE
with a drop in mid-range torque. I don't know the amounts or at what
RPM this will peak at but this will occur it's simple physics. Finding
how much of a benefit, well, that is up to one of you.

Rather than drive the car with the crossover always plugged in order to
boost low-end torque, the opportunity exists to have a valve in the
crossover to open and close at selected RPM. The proper mode of
operation is always a) valve closed at low rpm b) valve open at
mid-range rpm c) valve closed at high-range rpm. There is the
potential that you might find (I'd rather doubt it) that the SHO would
faster with this plugged all the time. Or possibly if you drive your
SHO on the track and spend all your time in the 4000-7300 rpm range,
maybe this modification is great for you.

Without overselling this too much, the bottomline is that someone has
got to try this. Please do so safely. Those plenums will suck anything
flexible right into your engine so a little bit of thought is necessary.


How does this work?

Briefly:

1) What happens when the intake manifold plenums are separated from one
another (split-plenums so-to-speak) the intake manifold generates TWO
tuning peaks. The tuning peaks occur based on a natural resonance that
occurs between the intake manifold runners and feeder pipe. Imagine the
air in the intake pipes and in 'feeder pipe' (that between the plenum
and the throttle body) as 'masses'. Imagine the air in the plenum as a
big spring. At some point the masses can begin vibrating both in-phase
(same direction meaning moving toward the port at the same time) or
out-of-phase (opposite directions). Resonance is helpful as it provides
pressurized filling of the cylinder just before the valve closes. In
general the tuning peaks associated with a split-plenum design are lower
in magnitude than that from a single plenum but it may allow improved
area under the torque curve (I'm guessing).

2) What happens when the intake manifold plenums are all connected.
There is no longer two tuning peaks (yes, we get two tuning peaks but
that is due to long & short runners). Instead just one tuning peak
occurs. This single tuning peak occurs with greater magnitude than the
split-plenum design.

So what else can you do about this.

If it is really found that this type of operation is either valuable
(with plenums continually closed) or lends itself to getting the best of
both worlds (opening and closing a valve in the cross-over), there are
possible changes that can be made to TUNE the manifold to more optimal
rpm values.

How???

Well, as I said before the masses in the 'feeder pipe' and runners are
the key items. Changing the manifold plenum size by 50% (hard to do)
makes only about a 200 rpm shift in the torque peak. Changing runner
lengths is hard to do. Changing the 'feeder pipe' length by adding a 50
mm spacer between the throttle body and the manifold will also shift the
low rpm torque peaks by 200 rpm. That's pretty easy to do even for the
mechanically challenged like me.

In any case, my disclaimer. Do this at your OWN risk and please use
your head about this. I claim no absolute improvements.

There is the potential here, primarily from using a valve in the
crossover which would open around 3000 and close around 5000 rpm to
boost your low-end and high-end. With the valve operating properly,
there would be no difference in the mid-range, as this is how Yamaha
tuned our manifold.

This is a sound practice and is on a manifold that I've just designed.
The benefits are not great but they are measurable for the performance
minded.

Thanks to John Weidenbenner for rekindling this topic and researching
it. Possibly there is nothing more than a few ft-lbs of torque and 5 hp
on the high-end to be gained. But that is all my LPM & 80 mm got me and
they were nearly $450 with the cone filter. I can imagine that one of
you can put together a $300 kit that does this with relative ease.

I was planning on just making the crossover pipe, and then later adding a butterfly valve for RPM tuning. Thanks for all that info!

This is great stuff. Welcome to modern hot rodding!

Great find! That is the exact patent!

Check out item #17. It clearly states:

"while under intermediate speed operation, only the valve 17 opens. "

Now we just need to find out optimal "intermediate" RPM speed.
Excellent find!

Pornstar* IS right.

The correct US Patent to read is 4,766,853.
This patent shows torque curves and explains when to switch things open and closed.

[Yamaha has no fewer than 15 patents on this manifold all in the 1986 to 1989 timeframe and some of them are even more wicked than the resulting manifold.]

********************************************

However, something, in page/column 7, strikes me as unusual.

1. Yamaha states to CLOSE the valve at low rpm (like the SVT is currently with no crossover).

2. Yamaha then states to OPEN the valve at mid rpm (unlike the SVT but like the SHO....this is where they suggest the gain is possible).

3. Yamaha then states to then LEAVE the VALVE open and open the secondary runners (again unlike the SVT and like the SHO). This differs last piece differs from theory a bit but may be because of the effect the secondary runners have on tuning. There should be a positive effect of eventually CLOSING the valve again at high rpm, but possibly for the SHO this occurs out of the usable power range or to close to the redline to make it worthwhile.

If someone tries this on an SVT, they should really do the following on the dyno from 1000-redline:

1) Crossover open, secondaries propped open
2) Crossover open, secondaries deactivated
3) Crossover plugged/off, secondaries open
4) Crossover plugged/off, socondaries closed

Why? Because it is possible that you might find that the best torque curve is developed by creatively timing the secondary and crossover valve opening. That is truly the only way to determine the full benefit of such a modification.

Bottom line, if you read this paper, and make the assumption that the SHO and SVT manifolds will react similiarly, then the SVT MIGHT have the opportunity to boost both mid and high end power with the crossover as it reportedly did on the SHO.

The tough thing is figuring out the level of the gain. To do that, someone has to be the guinea pig.

Good luck. At your own risk.

defector

And....

If you want to review the even-more-wicked manifold that Yamaha thought up for the SHO, read the incredible review of 4,763,612.

This manifold, has FOUR torque peaks instead of the 2 peaks that the SVT has.

Incredible stuff Yamaha was doing while I was daydreaming in study hall...

I recommend you guys have a look at Mazda's VRIS used on the 2.5L V6 Probe, MX-6, and 626 - it is a variable intake that has 4-stages of operation. The following page by Mike Paszti's does an excellent job of explaining how VRIS works and how it can be modified:

http://www.geocities.com/mikey9t6/car_uvwxyz_vris.htm

In particular, note the "short resonance tube" with butterfly valve - that is the crossover tube that we are trying to add.

I spoke w/ another engineer here and his suggestion (though he didn't have any of his analytical tools handy) said that the crossover should be as short as possible and to keep the size about the same size as the primary runners. We also discussed effects on resonance, etc. but that is what the valve would cover.

True, shorter crossovers work better.

But there is not much you can do to pull your plenums closer together, so bigger in diameter is better (up to the plenum diameter) to allow easier communication.