vari length inlets

[GT6M]

D Walkers got some intresting stuff on His blogg soptt

this ones quite intresting

 

http://www.emeraldm3d.com/articles/emr-adj-length-intake/

 

an Harry Dents on thea too.

 

http://www.emeraldm3d.com/articles/may2012/

 

M

 

 

 

[MikeF]

Must have been the same article I read. My bro and I were well into any way we could get more performance without spending any money on expensive tuning/ mods.

After reading the article we did some sums and found the inlet manifold was almost exactly the right length for peak power at red line, exactly right with intake trumpets, Similarly exhaust was the right length for peak torque [Which of course they would be, read the links.]

We did try some experiments with variable length inlet trumpets. Our idea was to have a system to open and shut holes [think clarinets etc)s on the trumpets using an extension to throttle mechanism. With our crude trial set up we couldn't actually make a measurable change in road tests so we just polished the head instead,

 

Mike

[oldtuckunder]

Take a good look at the inlet system on the BOB engine Ford Scorpio Cosworth, last of the Colone V6's, sod VVT, VIL (variable inlet length) seems to produce some great results.

 

I have a serious desire to get hold of one of them!

 

Alan

[TriumphV8]

Many thanks for the interesting links.

Seems to be the proove of what I expected.

As I do not want to spend the money for testing on the bench

I made my improvements only hoping its the right way.

One of the results posted was that 5mm difference in manifold length

made a noticeable difference in the dyno chart.

 

All my calculations both on race cars and street engines

ended with the conclusion that the inner wings limited the

proper length of the inlet manifold because for a race engine

it is not helpfull to bend or turn the manifold and for the

street engine it was too much work for me to develop and fabricate one.

 

So all I did on the TR6 was to expand manifold length by 50mm with

aluminium tubes between manifold and rubber tubes to the plenum.

 

[Motorsport Mickey]

As you say the inner wing prevents the fitment of inlet manifold lengths that will help in maximising the power in the rev areas available, these are the manifold lengths required to show most gains. On these DU6s fitted (just for one race) in 1987 the wheel arch was beaten to death dressed to allow the fitment.

 

 

The DU6s originally used on the Coventry Climax DPF engine and the Sabrina engine TRs didn't react well to the extended length tracts and have subsequently found a home with a new owner using a standard manifold length.

 

Mick Richards

 

 

[littlejim]

Many years ago the motor bike blokes were into 'megaphones' at the end of the exhaust pipe, and trying to copy the shape of the blokes who did well was all the go.

Believe the idea was to have a 'negative' shock wave at the exhaust port just as the valve opened.

[Motorsport Mickey]

Many years ago the motor bike blokes were into 'megaphones' at the end of the exhaust pipe, and trying to copy the shape of the blokes who did well was all the go.

Believe the idea was to have a 'negative' shock wave at the exhaust port just as the valve opened.

Yep Littlejim, a combination of the negative shock wave reversing direction and rebounding off the back of the exhaust valve just prior to it opening helps the piston on the exhaust stroke "scavenge " the most expanded charge out of the cylinder as possible. Hence the importance of the "tuned " length in exhaust systems to maximise the timing of the pulse of energy which "ping pongs" between end of exhaust and back of exhaust valve., wrong length reverse's the outgoing pulse "plug" and sends it back to the exhaust valve as the valve is open, choking or impairing the exhaust charge exiting.

At the other end of the engine the "pulse" we are hoping to harness as described above with "tuned" inlet lengths, is between the inlet valve opening and the piston sucking in the charge being fed or forced in via the carbs. If you get it right a combination of the two forces affecting both inlet tract and exhaust system can "overcharge" the cylinder more than it's 100% of volume even on naturally aspirated engines.

Apologies to all who are familiar with the application of the forces described above and my ad hoc description, if anybody wishes to expand or correct it, please do.

 

Mick Richards