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

[JazzyO]

On another note, I've noticed strumpets are of unequal lengths too.


Onno

[450Nick]

TVR Beaver said:

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

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.

[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...

[Del 203]

Another for comparison

[450Nick]

spend said:

If the RR comparison you are thinking of was Joos test, that was not a blended base but an 'Eliot' plastic insert.

If your deductions are being made from that all I can say would be

No I'm thinking of Tim's back to back tests on a Taraka 5L on Austec's Maha dyno when developing both the trumpets and the multi-throttle Plenums - the triple plenum was actually taken to Rover who themselves assessed it and gave Tim some feedback in the design.

I know I've posted this a couple of times before but here's the graph from Tim @ ACT:

[clive f]

spend said:

If the RR comparison you are thinking of was Joos test, that was not a blended base but an 'Eliot' plastic insert.

If your deductions are being made from that all I can say would be

it was still crap Dave, blended nicely or not

[Pasco]

clive f said:

it was still crap Dave, blended nicely or not

Yes it was


I think he meant as compared to my blended base Cliff which showed no loss of Torque

[Wotland]

Hi,

I don't want to pollute your post but after the length which is the importance of ID trumpets ? 38mm-41mm-44mm-45mm. Superflared or not.

And for the length, generally big bore trumpet base respect the same different length than stock trumpet base for external trumpets.

But in the past I had a SC bellmouth trumpet kit on TVR 500 trumpet base and I remember the fitting instruction kit asking to short more external trumpets than internal trumpets for a better distribution.

[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...

[eliot]

spend said:

If the RR comparison you are thinking of was Joos test, that was not a blended base but an 'Eliot' plastic insert.

If your deductions are being made from that all I can say would be

I think It was clive that tested my flared plastic base back to back the ACT carbon trumpets. The Trumpets were a little better throughout the pull. So IMO the best solution is flared trumpets.
I would say my plastic insert should be marginaly better than a taraka base - but still not ideal. I have also done an improved version of the Taraka base, where i filled the voids with aluminium putty before machining flares into it.
Some pics here:
http://www.mez.co.uk/ms12.html


I suppose another approach would be using a thicker piece of plastic, but you would need to redesign the plenum cover because the air would just slam into the side of the plastic.

I had a GEMS plenum in for machining this week and I placed it next to a Hotwire plenum it was noticbly taller and would give more area aroud your trumpets. The bolt holes are identical. You would need to add the hotwire idle stepper and adpat the TPS, as im not sure its the same electical spec.

[Alexdaredevilz]

eliot said:

I think It was clive that tested my flared plastic base back to back the ACT carbon trumpets. The Trumpets were a little better throughout the pull. So IMO the best solution is flared trumpets.
I would say my plastic insert should be marginaly better than a taraka base - but still not ideal. I have also done an improved version of the Taraka base, where i filled the voids with aluminium putty before machining flares into it.
Some pics here:
http://www.mez.co.uk/ms12.html


I suppose another approach would be using a thicker piece of plastic, but you would need to redesign the plenum cover because the air would just slam into the side of the plastic.

I had a GEMS plenum in for machining this week and I placed it next to a Hotwire plenum it was noticbly taller and would give more area aroud your trumpets. The bolt holes are identical. You would need to add the hotwire idle stepper and adpat the TPS, as im not sure its the same electical spec.

Could you not make a spacer between the inlet manifold to the trumpet base so get your tourque back?

[spend]

I didn't know Clive had a rolling road to test it on

[eliot]

Alexdaredevilz said:

Could you not make a spacer between the inlet manifold to the trumpet base so get your tourque back?

Yes I guess so, but it would need to be 2" thick. Not sure the bonnet would close?
Seems more trouble than its worth considering trumpets do the job better.

[Alexdaredevilz]

eliot said:

Alexdaredevilz said:

Could you not make a spacer between the inlet manifold to the trumpet base so get your tourque back?

Yes I guess so, but it would need to be 2" thick. Not sure the bonnet would close?
Seems more trouble than its worth considering trumpets do the job better.

But with blending you could get say 50mm hole?

But with trumpets you cant really get more than 45 ID

[eliot]

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

[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

[Alexdaredevilz]

TVR Beaver said:

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

Well you say that, but the V shape you would end up having would speed up the air

IMO you would need a larger throttle body to compensate with the 50mm's

[spend]

Going to these esoteric sizes & shapes requires the manifold & bases to be welded up, to provide a bit of extra cast thickness in a few critical areas. However the 3d shapes and bends are not any different in concept from the porting that you do in heads.

If I were to say to you that you must have only circles in your heads you'd think I was barmy.. Why should the inlet & base be any different, it is just an artificial factor that you introduce using trumpets really.

ETA: An old article that took me some time to find, which seemed a proper evaluation tending to suggest girth is more important than length oerr:

Edited by spend on Thursday 17th March 17:21

[domV8]

eliot said:

Yes I guess so, but it would need to be 2" thick. Not sure the bonnet would close?
Seems more trouble than its worth considering trumpets do the job better.

The thicker the machined plastic insert, the more you are reducing the plenum volume.

So surely you would also have to compensate for the reduced plenum volume by adding a plenum spacer in between plenum top/bottom to regain the lost internal volume - thereby increasing the height of the assembly even further..?

Dom

[v8 racing]

Smaller the plenum the better for me!