Mi16 Inlet Tract Length

[miamistu 1]

Keep seeing that people use 90mm long trumpets with Jenvey throttle bodies which presumable give the same tuned length overall as the original manifold (including the little manifold, bodies and trumpets themselves)

 

Does anyone happen to know how long the whole system is supposed to be from the head to the inlet of the trumpet though?

 

Cheers!

 

Stu

[Mandic 0]

Yeah, interested in this myslef...

 

Cheers

 

Ziga

[Jonmurgie 2]

I can measure mine in the morning but at the moment I can tell you that the Jenvey Bodies are 118mm deep (long or whatever) so with 90mm trumpets that's 208mm, just need the depth of the inlet manifold...

 

Having spoken to Richard Jenvey himself about the inlet tract length he led me to belive that Peugeot along with Longmans had experimented with several different options and found that unless your building a 300bhp N/A Touring Car engine there's little need to deviate from the 90mm trumpets which give the best alround tract length for the Mi

[miamistu 1]

That would be great, cheers Jon

[James_R 3]

For the calculations on inlet tract length it's from the base of the valve, so if anyone has that measurement that woudl be handy too

[Jonmurgie 2]

Although that's a measurement that people don't/can't change so not as important... everthing from the OUTSIDE of the head can be changed and with the more common Bike Carb's route with home-made inlet manifolds I guess it's important to know what kind of inlet tract your aiming for!

[petert 586]

I think it's in the range 290-330mm, valve seat to trumpet. There's a few calculators on the net. Do a search.

[petert 586]

Read this,

http://mgcgti.clarkeandclarke.co.uk/Page28.html

and this,

http://www.civ.ed.ac.uk/~jchick/Y5/thesis/...ic_html/pt7.htm

and this,

http://www.rbracing-rsr.com/runnertorquecalc.html

 

I got different results for the 285 deg. example on the MG site. It's interesting that whilst the formulas for the first two sites are the same, the method of calculating the ECD differs considerably, giving vastly different results.

Edited April 13, 2006 by petert

[B1ack_Mi16 67]

Length of port in head: 80mm

Length of Jenveys (red ones), small manifold and 90mm trumpet: 280mm

 

I'm not 100% sure of the standard inlet manifold, but I believe it's close to 280mm that one too.

[Jonmurgie 2]

Cool, so that gives us the figures as follows:

 

Head Ports: 80mm

Inlet Manifold: 72mm

Jenveys: 118mm

90mm Trumpets: 90mm

Total: 360mm - though as the 80mm head ports don't get changed it's the 280mm figure that would ideally nee to be matched in any other setup

[miamistu 1]

You sir, are a star. Thankyou very much

[petert 586]

Mine differs a little:

 

manifold - 100

TB's - 88

trumpets - 75

 

so a total of 343mm (inc. inlet port)

[petert 586]

Here's another one, exhaust and inlet:

 

http://www.btinternet.com/~mezporting/exhaust_length.html

 

 

and another one:

 

http://www.bgsoflex.com/intakeln.html

Edited April 13, 2006 by petert

[Bonzai 2]

my setup currently stands at

 

Inlet Manifold: 180mm

Jenveys: 118mm

Trumpets: 45mm

 

although this is all only sitting on a shelf looking sexy for now

Edited April 13, 2006 by Bonzai

[miamistu 1]

my setup currently stands at

 

Inlet Manifold: 180mm

Jenveys: 118mm

90mm Trumpets: 45mm

 

although this is all only sitting on a shelf looking sexy for now

 

are the trumpets 90mm?

[Bonzai 2]

oops no, i just copied and pasted jon's format edited now...

[Galv 0]

Measured mine, I've got longman manifolds and weber 45's with 45mm trumpets and the distance from the head is 245mm overall. I'm not sure there is enough room for 90mm trumpets without some major mods to the slam panel

[JR20516V 6]

Peugeot has probably spent a motza on getting the inlet manifold to the correct length etc which leads me to my question....would it not be best to attach TB's to the existing factory manifold. Has anybody done this and has pics, info etc. Very interested on your comments!

 

Also is the Longman manifold an improvement on the stock factory jobbie?? If so ....why???

[Rippthrough 98]

Peugeot has probably spent a motza on getting the inlet manifold to the correct length etc which leads me to my question....would it not be best to attach TB's to the existing factory manifold. Has anybody done this and has pics, info etc. Very interested on your comments!

 

Also is the Longman manifold an improvement on the stock factory jobbie?? If so ....why???

 

 

The bodies would increase the tract length though.

[Rik 0]

How come this thread has gone quiet?

 

I'd of thought this would be a hot topic with the amount of people running bodies.

 

I'm not looking for a necessary standard length, but a length and some assumptions/definates of the effect on torque of the induction length

 

So far i've seen the following assumptions.

 

For torque lower down in the rev range:

 

-Injectors should be close to the head...

-The inlet tract should be as long as possible...

 

Now the standard manifold does all the above if modified for TB's, so i'm thinking of using the standard manifold and using the calculations posted, try and create a length of around 280 - 300mm, without the use of trumpets. as the standard induction headers are fairly long.

 

i'll be using samcos etc.. to fit them to the manifold so i presume the length can be adjusted fairly easily to achieve the best torque curve.

 

Any got any views on this

 

Rik

[Sandy 191]

The relationship between cam timing, inlet tract diameter, taper and length, all conspire to make the "ideal" length incalculable without pointlessly extensive modelling. Then you alter the inlet cam phasing and it all changes!

 

The best bet is to make some provision in your set up for experimentation and commit some dyno or roller time to playing a bit, you'll be looking at a compromise of some sort either way.

 

That said, in my meagre experience, maximising inlet length tends to bring more useful gains than settling for the easiest layout. And for gods sake drop the radiator and fit a heatshelild to ensure the hot air of the rad isn't your inlet supply, or your worrying about the wrong thing completely!!

[petert 586]

The relationship between cam timing, inlet tract diameter, taper and length, all conspire to make the "ideal" length incalculable without pointlessly extensive modelling.

 

and rod/stroke ratio

[Sandy 191]

Haha, true, that kinda comes under cam timing?