Question about ITB trumpets

[Rice86]

A type


B type


a general question so i dont think using the templete is needed...
also couldnt find anything on google

are there any pros and cons with the trumpets shown above?
reason why i ask cause ive been looking at a few ITB setup and see that everyone runs 2 types of trumpets, type A and type B as shown above, the mouth (if i can call it that) of the trumpets are different and thats what i want to know...does it really matter how the mouth are rolled, lipped like type A or no lip like type B, also, does it matter what length you choose to use?..

reason is cause if they arnt any different, lipped or not lipped, short or long, then im just going to get what looks best in my eyes

Type A is a picture of mine, incase yous aren't aware =p

[Sam-Q]

in theory in an ideal world there is meant to be a 7 degree taper from the bellmouth to the intake throat. Improves air speed for my cylinder filling. Well it's one theory I have read anyway. I have no idea if it's right or not. I am guessing most companies make trumpets like that because it looks better.

[LittleRedSpirit]

When the motor is sucking in the air, it will be pulled in from all around the trumpet. Some air even comes up the shaft and around the lip to go in. This can be tested with a vaccuum cleaner and a cigarette if you have a trumpet there. You want to take any steps you can to smooth that air out. I think the ones with the rolled over lip are going to let air travel more smoothly into the engine. That said, in actual hp terms it will be maybe 1hp difference, barely measureable. Might be more of a difference if you rev to 15000 revs but thats not going to happen.

[ae86rally]

length is important too I think mine are @200 mm long from opening to the head, designed specifically to mid range power.

[Frak]

Length is very important

over the years I have done a lot of dynoing trying different trumpet lengths on 16v and 20v(it's actually a bit of a hobby testing trumpet lengths), the MOST important thing is to run them in an airbox

I have many many dyno prinouts of different lengths, in boxes, out of boxes etc, what you read about long = bottom end, short = top end isn't always true

optimising the trumpet can give awesome gains, on my daily AE111 I picked up 6kws at the wheel just with a trumpet change, on ST's I have done in the past on engine dyno, 10-12hp at the fly.

[sundee]

im pretty sure the taper is used to accelerate air into the stack itself - as air travels over a cambered surface the air speeds up, the greater the camber or curvature the greater the acceleration. im guessing that type B would create more turbulance under the lip then type A. Type A i would also assume would be able to draw air from below its lip at higher RPM/Velocities

[Rice86]

wow some really informational information

Frak, with ur experience, what do you think is an ideal length to use...best for power gain or response?...enlighten the thread if you can =D

[Sam-Q]

so can you confirm that 20V engines seem to defy all theory when it comes to having really long trumpets? any tips on shape and length for us unexperienced guys?

BTW airboxs are the best

[Hen may possibly be a nut]

I have no personal experience, however from things I've read and heard from people I respect apparently a surprising amount of air flows from around the edge of the trumpet, not straight down the throat. So apparently fully rolled lips (Type A) are better.

I guess there are some here who can confirm/deny.

Hen

[Sam-Q]

well on a flow bench a flared end gets 30% more airflow than a straight pipe and a full bellmouth has 3% more again