Trumpets parp parp!!

adikt · Post by **adikt** » Tue Jan 16, 2007 4:02 pm

What are peoples views on the trumpets inside the plenum? I've heard of people taking them of completely, removing 35mm from the base, modifying the mouths, etc. Does anyone have any expierience of this?

Thx

Eliot · Post by **Eliot** » Tue Jan 16, 2007 4:46 pm

Depends on your engine combo, size and what its in.
I removed about 40mm from the std rr trumpets when fitting a 3.9 in a westfield (which has been gas flowed and a rc85 cam i think)

The big act carbon trumpets suit bigger power motors (tvr 5L etc)

some photo's to get your brain turning can be here:
www.mez.co.uk/ms12.html

ChrisJC · Post by **ChrisJC** » Thu Jan 18, 2007 8:02 am

As I understand it, the trumpets are there to give a smooth airflow through the old type flapper airflow meter.

And I guess they will also resonate at certain engine speeds (tuned pipe between valve and trumpet mouth). Not sure what speed that'll be though.

Chris.

chodjinn · Post by **chodjinn** » Thu Jan 18, 2007 3:22 pm

"As I understand it, the trumpets are there to give a smooth airflow through the old type flapper airflow meter. "

You got the airflow meter installed in the block then?!?

ChrisJC · Post by **ChrisJC** » Fri Jan 19, 2007 10:29 am

Eh?, what are you on about?

The air flow will be pulsed in each runner (obviously), but the AFM needs a uniform air flow. So by having the same distance between the valve and the top of the trumpet, the pulses all arrive in the plenum at equal time intervals. The plenum provides a reservoir of air and damps out the pulses to give a nice smooth flow through the AFM.

My AFM is where the sun don't shine.

Chris.

Ian Anderson · Post by **Ian Anderson** » Fri Jan 19, 2007 12:00 pm

See
http://www.gt40s.com/forum/gt40-tech-en ... study.html

At one point he talks about trumpets intersecting each other an describes it as a "no no"

OK flow model was for webbers but pretty well matches plenum except for "head height"

Ian