Lancia Motor Club

Model Technical and Interest => Fulvia => Topic started by: RobD on 14 January, 2015, 06:42:19 PM

Title: Unequal length trumpets
Post by: RobD on 14 January, 2015, 06:42:19 PM
Targa Florio Classics are flogging a significantly modified Fulvia on eBay. I was interested to see it sports unequal length inlet trumpets and wondered if anybody had any experience of these.
Presumably the staggered trumpets are supposed to compensate for the V4s unequal length inlet tracts but I would have thought the only way to do this properly would be to stagger the distance of the throttles rather than the length of the trumpets so that the mixture has the same distance to travel. This would of course require four individual carbs using bike carbs or similar and I must confess I'd recently considered the possibility of doing this using some single choke 36mm Dellortos I've got knocking about, hence my interest.
My first thought regarding the staggered trumpets is that it looks quite radical but probably does very little but I'm always open to persuasion.
 Does anybody know if there is any science or Fulvia experience to back it up?

Title: Re: Unequal length trumpets
Post by: stanley sweet on 15 January, 2015, 10:33:33 AM
I've been meaning to ask about this for some time. It doesn't seem logical to me. As you say, they are staggered long, short, long, short. But if the inlet manifold is basically similar in design to say my standard 1300, then the outer inlets are longer than the inner two. I thought the idea is to equalise the length. So to me they should be short, long, long, short. Be interesting to hear the explanation.

Title: Re: Unequal length trumpets
Post by: peteracs on 15 January, 2015, 10:44:18 AM

Looking at the picture, I think the answer may be a simple, equal length ones would not fit as the inlet end flange on them would interfere with the next one, so they used unequal ones which just give the clearance, bit bonkers to my mind, but if that was his only choice....


Title: Re: Unequal length trumpets
Post by: stanley sweet on 15 January, 2015, 03:33:36 PM
To be honest, I didn't look at the Targa Florio photos until afterwards. I was basing my comments on lots of others I've seen on the internet. The clashing of the trumpets seems the only answer, Surprised (especially with some of the Italian tuning places) that nobody has come up with a siamesed pair similar to the old Ferrari V12's. Shouldn't be beyond a competent engineer. Unless of course, as RobD said, the difference is so miniscule it's not worth it?

Title: Re: Unequal length trumpets
Post by: Richard Fridd on 15 January, 2015, 03:48:44 PM