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

[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

[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??

[TVR Beaver]

Alexdaredevilz said:

Heres mine

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

[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??

[TVR Beaver]

450Nick said:

A lot more than bhp gained from doing it... I have a graph from ACT somewhere, it has been tested extensively in the past, and superflare trumpets give a thicker power curve all the way up. Blended base gives a couple of bhp extra at the very top. I'd go superflare trumpets every time - torques what you want in a road TVR.

Agree.... I lost torque I'm sure going TO the trumpets from the original straight pipes... This also followes... but it did make the engine rev more freeley... and go to higher RPM's...

[TVR Beaver]

I think the volume of the trumpet has a lot to do with it and the torque loss / gain...
again, going back to the OE 500 base, they were 44mm but straight.. where as the trumpets are 45mm at the base and flare out...
Would be good to get a few set-up's side by side and see how they perform for sure...

[TVR Beaver]

How big are the holes in the manifould?... no point going to 50mm if these are only 45mm or less...
You could ulimatley get rid of the base by cutting it out.... and blend the top of the manifould

[TVR Beaver]

v8 racing said:

Smaller the plenum the better for me!

Rob.. why?.. does it result in a more direct feed?.. how would it benefit??

This one looks the works.. anyone know what happened to it?.. may be setting the two up would be a problem?..

Edited by TVR Beaver on Tuesday 15th March 21:15

[TVR Beaver]

Paul... Only 'Blades' I can find is Kevin Finney... Is this the guy?

Looks a piece of work anyway.. what did it do?.... any info on it... as I would love to make one

[TVR Beaver]

DNB.. so that's what it stands for

As in Harry Potter fame

This also may go someway to answer a question I asked here about the LCD in the dash http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Mmmm.. may be worth a word.... I do indeed like to look...

Edited by TVR Beaver on Wednesday 16th March 15:13

[TVR Beaver]

v8 racing said:

Hi John, the downside to large plenum chambers is the lack of throttle response, obviously the bigger the volume between the valve and intake butterfly will reduce throttle response, an engine doesn't need a chamber to breathe it just needs an adequate air entry, the dnb/clive intake system is a good system and i talked to tim at act about doing something similar about 15 years ago, but it wasn't really marketable due to costs and having to run after market ecu's etc,

I suppose more air in the existing plenum system helps with things like reverse flow on overlap so helps to smooth out the intake a bit... So this is why people add spacers and say it helps with shunting and the like... Reduce the volume you'll get better responce but the shudders and shakes that come with it?

But as you say with the more dirrect feed of the set up in the pic... it's a win / win..
Does look interesting for sure.. More along the Cerby style

[TVR Beaver]

Sure have!.. Thanks for that.. very interesting indeed... and I can imagine the time taken to get it set up etc... the SS fabrication would not be too much of an issue for me, but the ECU and that side of it would all be very new.
But I'd love to give something like this a go... There must be better ways to feed these units than the original Plenum and it's associated problems and this looks like a good one..... and as it's fabricated, relativley cheap in comparison with casings / machining etc....;)
Will continue to look around this season.. and may be have a go next winter.... I like these projects rather than doing up wishbones / painting outriggers etc

[TVR Beaver]

eliot said:

Alexdaredevilz said:

But with blending you could get say 50mm hole?

But with trumpets you cant really get more than 45 ID

Indeed - but do you need a 50mm hole. Only guessing, but you probably need a 5L + engine reving north of 7k rpm to justify it - which is into high end wildcat teritory and therefore ££££££££.

I think this is the best solution:

Long runners and individual throttle bodies.

Edited by eliot on Sunday 13th March 08:44

Just seen this pic.. added after we went over the page I think... Like this a lot.... Who's is the manifold.. any ideas??..

[TVR Beaver]

Mmmm interesting all the same... sort of keeps it std over the LS??... but as you say.. a lot of dosh ...
Wonder what its claimed / tested to do?...

[TVR Beaver]

That is true.... I had a very sharp 90 deg inlet elbow fitted initialy to the car (MAF to Plenum),... and thought myself it could be an issue so changed if for one with a bigger bend... and it helped a lot for sure!... can't quantify it.. but made the thing feel much freeer flowing...

[TVR Beaver]

Wow.. nice... even the reduced figure would be good.. and torque to match I guess.... not that it matters as I can't afford it.. but nice to dream...
have to start busking or something?..