Trumpet removing?

[bhpjon]

Afternoon Folks, does anyone have a definitive answer to how much difference removing the trumpets makes on a twin or triple plenum. I understand from my limited knowledge (gleaned from here) that it affects the torque of the motor, has anyone got any ideas please?

[sparkythecat]

A few people were blowing their trumpets on this thread

www.pistonheads.com/gassing/topic.asp?t=275060&f=8&h=0&hw=trumpet

[spend]

I do like the look of Eliots 'insert' ~ would have thought it was easy to take a mould from & get injected by a plastics company hint-hint.

But you still need to gorge out the base to 45mm~ so why not just chamfer the alloy edge as part of that process as in the Jamie/Joolz method.

I am also a little confused why the insulator goes under the trumpet base ~ surely between the inlet manifold / head would be the best place for it?

Dave

[GreenV8S]

Under the trumpet base is easy because it's in a single plane. Between the manifold and heads would require machining the manifold to avoid it 'riding up' in the V and messing up the port alignment. In any case since the manifold is water heated, trying to insulate it from the heads isn't likely to achieve much.

[spend]

Points taken, thanks Pete ~ still itching to try the Black Satin on it tho

Dave

[bhpjon]

What about removing the trumpets altogether and flaring out the trumpet base?

[GreenV8S]

bhpjon said:

What about removing the trumpets altogether and flaring out the trumpet base?

I understand TVR Power did this for their Taraka warmed over engine. In theory it means the inlet tracks are different lengths and a bit too short for optimum power, in practice it did seem to work OK.

[andy-w]

GreenV8S said:

[quote=bhpjon]In theory it means the inlet tracks are different lengths and a bit too short for optimum power, in practice it did seem to work OK.

Would it be safe to say that if each of the cylinders was trying to suck in so much air it would balance itself out...i know there is the theory but you can sit there and work things out using pure math but when it comes down to it trial and error works a lot better...???

[spend]

My take is ~ at full bore the less restrictions the better. Ignoring the torque characteristics (well we aint towing caravans are we?)

I think somewhere Joo posted a comparison of flared trumpets & his self blended base (IIRC he did'nt spend a lot of time on it)

Personally cant see how the trumpets are not an obstruction to flow + if you look at the pattern the cylinders sucking thru the manifold it doesnt encourage an even distribution from the plenum (which also I can only see the trumpets hindering). There are arguments for flow patterns around trumpets curved lips on TB's but I struggle to see how this works in the plenum. Any flow thru pipe has some resistance - the bigger the pipe or shorter the run the easier it is to suck thru in my simple appreciation.

All my own personal opinion & prob out on a limb a bit

Dave

[GreenV8S]

Induction tuning is usually based on the principle of tuned lengths, using the inertia of the air in the pipe to cram some extra charge in at the end of the induction stroke. The length of the pipe is a critical factor to determine the rev range that this effect is strongest over. If you could magically remove the whole intake manifold and leads the heads nicely radiused to air, you would probably find that it runs like a dog. In this case we're only talking about an inch or two shorter than the optimum which isn't the end of the world, but it's still away from the optimum.

[trackcar]

I'm not convinced that there's any tuning potential to come from the trumpets if you have a restrictive inlet upstream anyway. All my back to back testing has shown that anything with a good blend on the entry (radiused trumpet or blanded trumpet base) works well no matter what the length.

I have never been able to determine for sure any diferences in the hp curve that proves running trumpets is any better to a blended trumpet base. the std TVR 500 pieces of pipe are not restrictive until well over 280bhp and there's not many cars out there running AFMs with this power anyway.

Time spent blending the base (for free i you do it yourself) is good time spent IMO.

[bhpjon]

trackcar said:

I'm not convinced that there's any tuning potential to come from the trumpets if you have a restrictive inlet upstream anyway. All my back to back testing has shown that anything with a good blend on the entry (radiused trumpet or blanded trumpet base) works well no matter what the length.

I have never been able to determine for sure any diferences in the hp curve that proves running trumpets is any better to a blended trumpet base. the std TVR 500 pieces of pipe are not restrictive until well over 280bhp and there's not many cars out there running AFMs with this power anyway.

Time spent blending the base (for free i you do it yourself) is good time spent IMO.

Thank you again Julian for being so willing to assist even the technical F*%^*@ts out here who make your life so much harder with the constant phone calls, picking your bursting brain, wondering whether two or three jaguar throttles is the way to go!! (PS i am working on a cunning plan as we speak)