Trumpet base and trumpet length... why are they not similar?

[TVR Beaver]

Just changing the fuel pipes so have removed the plenum and trumpet base to get better access... and when you look at the trumpet length, they are not all the same relative to the cylinder... ?
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the 4 outside ones that cross over on the manifould are the same.. but the centre 4 are not... 1 tall, 2 mid size, and 1 small... ?.. wonder why they do that?.. I can understand them grouped in 2's as they would not go in all the same length unless you trimmed the trumpet like on the carbon ones... but why have 3 size on the central ones?.. I thought keeping them all the same 4 and 4 was the best for smooth running.. do you think this will have any effect?.. may be it's done to spread the torque band or something??

It's a V8D base so may be Rob's on and could tell us?.. if not I may give them a call tomorrow...
Just an observation if anyone knows the answer?.. cheers

[eliot]

Because the distance to the valve is different in the manifold, so they even it up in trumpet base.

[clive f]

ideally all of the inlet tract lengths should be the same, so your trumpet lengths are different because the lengths on the tracts in the inlet manifold itself are different, for example the inlet lengths inside the manifold for cylinfers 1 and 2, and also 7 and 8 are longer than 3,4,5 and 6, hence the shorter trumpets.

[Alexdaredevilz]

If you ask me, its so you can get the buggers in!

[clive f]

spend said:

I'm not convinced the picture above corrects anything, the middle four are pretty much the same and the outside ones vastly different (front-back & side-side IYSWIM)

your right Dave, the middle ones have the egdes cut so they fit nicely together at the trumpets.

Edited by clive f on Tuesday 8th March 22:28

[TVR Beaver]

Yes.. would have thought 4 and 5 would be the same though... why one long and one short?
The 1,2 and 7,8 tracks must be much longer than the middles anyway??...
Plenum roof comes into it somewhere

[spend]

Stop posting those blinkin fire engine pictures Cliff, I've spent a fortune on Nitromors getting it off, as well as all the rubbing and don't want to see it ever again

[Alan Kee]

Trumpet lengths don't have to all be the same length, or more correctly inlet tract lengths don't have to all be the same lengths .. it's not uncommon to have staggered inlet lengths to spread a pulse tune rpm band .. the rpm band is broadened but the peak effect is reduced. Got to say though the lengths involved here aren't anywhere near enough and it looks more like it's done for ease of fitting than any tuning benefit.

[TVR Beaver]

Alan Kee said:

Trumpet lengths don't have to all be the same length, or more correctly inlet tract lengths don't have to all be the same lengths .. it's not uncommon to have staggered inlet lengths to spread a pulse tune rpm band .. the rpm band is broadened but the peak effect is reduced. Got to say though the lengths involved here aren't anywhere near enough and it looks more like it's done for ease of fitting than any tuning benefit.

May be... I know on my Freelander the inlet is on one side resulting in increasingly long tracks to each port... They also have blanked off tubes on them like 'Pan Pipes'... I assume these help with the same??

[Alexdaredevilz]

Heres mine

[rev-erend]

Alan Kee said:

Trumpet lengths don't have to all be the same length, or more correctly inlet tract lengths don't have to all be the same lengths .. it's not uncommon to have staggered inlet lengths to spread a pulse tune rpm band .. the rpm band is broadened but the peak effect is reduced. Got to say though the lengths involved here aren't anywhere near enough and it looks more like it's done for ease of fitting than any tuning benefit.

Agreed on both counts !

[TVR Beaver]

Alexdaredevilz said:

Heres mine

Thats even stranger.. you have outer ones longer than the middle ones??

[spend]

Maybe he's got a Thor inlet manifold

[dbv8]

[Alexdaredevilz]

To be totally honest if I were to to it again, I would have a blended base, that way you can get a few more mm's

[dbv8]

Who cares about the size of the inlet when chemical supercharging does all the work

[Bluebottle]

dbv8 said:

Who cares about the size of the inlet when chemical supercharging does all the work

Till the bottle runs out those look like the SC Power trumpet collers?...my trumpets were a bigger Dia. than their collers so i couldn't fit mine.

[dbv8]

Bluebottle said:

dbv8 said:

Who cares about the size of the inlet when chemical supercharging does all the work

Till the bottle runs out those look like the SC Power trumpet collers?...my trumpets were a bigger Dia. than their collers so i couldn't fit mine.

Yes Hamish SCpower - still at a lowly 38mm. Gave me 273 bhp on my tired old 450 which io didnt think was too bad at the time.

As for the nitrous running out the formula is 0.8lb per 100bhp per 10 seconds.

As i run twin 11lb bottles this means i can either have a 50 bhp boost for over 9 minutes or 300 bhp for over 90 seconds (or 9 drag races)

[Pasco]

spend said:

Stop posting those blinkin fire engine pictures Cliff, I've spent a fortune on Nitromors getting it off, as well as all the rubbing and don't want to see it ever again

So whats up with a blended base ? who needs trumpets anyway

[TVR Beaver]

Pasco said:

So whats up with a blended base ? who needs trumpets anyway

How much torque is lost doing the blended base?.. Any idea??