Trumpets again
Discussion
Im looking at a trumpet mod to my 97 450 chim ive got a few options in mind, has any one any experience or input in the following ideas?.
ACT carbon fibre trumpets and exchange base(had a chat with Tim sounds a good idea)£300 ish
Cutting down my own.....free but grief also the whole car bits in the oven issue with her indoors
OR changing to a 5.0 set up..... Not sure on cost or sure how involved this would be, all i know is its not the same plate and trumpets as the 450 also is it worth it?
Cheers Meatball
Hmmm... the trumpets are only part of the equation. Not much point having free flowing stacks if the runners are restrictive. Not much point flowing the runners if the ports are restrictive. Not much point sorting the ports if the valves are too small... 
All depends on budget... the cutting them down mod with an insulator plate is a great one for the dosh/time and is very satisfying but, as with everything, you can go further if you 'need' to
All depends on budget... the cutting them down mod with an insulator plate is a great one for the dosh/time and is very satisfying but, as with everything, you can go further if you 'need' to
I've asked this before without getting a serious answer:-
Why do the insulator and heatshield mods work, if indeed they do?
IMO all they do is stop heat escaping from the engine/inlet manifold NOT prevent heat entering with the intake air which must only take milliseconds to get from the air filter to the combustion chamber and therefore can't take on much extra heat.
Does retaining heat in the engine/inlet manifold improve power/torque?
I would welcome some serious well thought out opinions on this subject - not just 'Well it does - so there!' comments.
C'mon all you TVR experts (you know who you are)educate me please.
Ricardo
Why do the insulator and heatshield mods work, if indeed they do?
IMO all they do is stop heat escaping from the engine/inlet manifold NOT prevent heat entering with the intake air which must only take milliseconds to get from the air filter to the combustion chamber and therefore can't take on much extra heat.
Does retaining heat in the engine/inlet manifold improve power/torque?
I would welcome some serious well thought out opinions on this subject - not just 'Well it does - so there!' comments.
C'mon all you TVR experts (you know who you are)educate me please.
Ricardo
simonb9 said:
There is problem an obvious answer to this but I don't know what it is so here goes -
Why are the trumpets different lengths ?? And what does cutting them down do ?? I assume they have to be cut down in a certain way to keep them unequal - if you see what I mean.
Why are the trumpets different lengths ?? And what does cutting them down do ?? I assume they have to be cut down in a certain way to keep them unequal - if you see what I mean.
At a guess it is so that the overall inlet tract of each cylinder is the same.
...one of the things tim (ACT) mentioned was the carbon trumpets are actually longer than the standard ones.Ok... there is a pulse tuning effect according to inlet tract length that has an effect on power curve/engine response. The end of the trumpet sets up a pressure wave/standing reflection that interacts with valve timing/overlap etc that impacts on cylinder filling/scavenging (and, in turn, is dependent on whether the trumpet is 'flared' or parallel sided). As with exhaust tuning that works in the same way, there are gains to be had in places in the range with consequent losses elsewhere. Within reason, shorter tracts shove the sweet spot further up the rev range and this effect is prononced on Rv8s that started off as relatively low revving units where inlet design has seemingly not developed along with improvements to the rest of the motor... might tbe wrong but remember reading the basic inlet design/dimensions had never really changed from inception whereas the later motors operate at much higher revs. An added benefit of cutting them down is that more area is available for airflow over the top and they are cut by equal amounts as it is the runners that differ in apparent length (the trumpets just sit at different heights in varying recesses in the base).
Quinny said:
simonb9 said:
There is problem an obvious answer to this but I don't know what it is so here goes -
Why are the trumpets different lengths ?? And what does cutting them down do ?? I assume they have to be cut down in a certain way to keep them unequal - if you see what I mean.
Why are the trumpets different lengths ?? And what does cutting them down do ?? I assume they have to be cut down in a certain way to keep them unequal - if you see what I mean.
I'm not an expert, but the way I see it is this.
The legnths are different in an attemt to keep all inlet tracks the same.
And the reason for cutting them down is to create more volume in the plenum, and to attenpt to get the air to flow straight into the trumpet, rather than enter the plenum then have to change direction upwards, find the entrace to the trumpet and get drawn in downwards.
No idea if thats right or not but it sound feasable
Sounds like a great explanation to me !!
until meatball posted that the ACT carbon trumpets are actually longer.....!!
Edit
more information has been added, read then go to bed to sleep on it.) Edited by simonb9 on Tuesday 12th December 23:18
Ricardo Bertone said:
....
IMO all they do is stop heat escaping from the engine/inlet manifold NOT prevent heat entering with the intake air which must only take milliseconds to get from the air filter to the combustion chamber and therefore can't take on much extra heat.
........
Ricardo
IMO all they do is stop heat escaping from the engine/inlet manifold NOT prevent heat entering with the intake air which must only take milliseconds to get from the air filter to the combustion chamber and therefore can't take on much extra heat.
........
Ricardo
I'm not totally convinced that is the case, with my old V8S I had 3D mapped ignition and with that I had an air temp probe just prior to the plenum in teh air stream. If the car suffered from heat soak it took ages ( at least 30 secs) for the intake temp to drop back down to anywhere near normal. I think you would be surprised at how much latent heat can be stored in the old RV8 lump, waiting to transfer it to the air being drawn in.
Out of interest when running hot, intake temps of 40+ degs, even my 275 hp motor would drop up to 30hp
. Back on topic, agree with the comment about the Ali 45mm trumpet base, not as gucci as the carbon but just as effective, pretty much all you'll need imhe
Thermal management is a very good way of picking up hp, as harry said it's easy to drop significant hp with high inlet temps.
the std 5litre tvr inlets arent straight, they're gently tapered and i did a back to back comparison on a 5 litre griffith and changing from the std tvr inlet to flared trumpets picked up only 2bhp. it was a 280bhp car so this result may vary on higher hp cars.
By comparison fitting insulation to the long pipe leading to the filter (no need to change it, it flows lots of air unless it's collapsed internally - just insulate it) and a silicone elbow and thermal isolator base picks up 6-8bhp for about a third the cost.
IMO.
the std 5litre tvr inlets arent straight, they're gently tapered and i did a back to back comparison on a 5 litre griffith and changing from the std tvr inlet to flared trumpets picked up only 2bhp. it was a 280bhp car so this result may vary on higher hp cars.
By comparison fitting insulation to the long pipe leading to the filter (no need to change it, it flows lots of air unless it's collapsed internally - just insulate it) and a silicone elbow and thermal isolator base picks up 6-8bhp for about a third the cost.
IMO.
As well as ACT, Demon Tweeks also do a range of silicone elbows, etc. but I think they are more expensive. If you're dealing with a non-TVR specialist supplier you really will need to know 'your arse from your elbows' to ensure you get the correct diameter, etc.
I respect what you say Trackcar in relation to the bhp gains but can you explain why?
I didn't quite follow the other explanation - I'll have to think about that one - sounded like you were agreeing with me unless I picked it up wrong. The latent heat in the block you refer to is dissipated through the plenum, etc. Thermal insulation will only keep more heat in the engine as it is the sorce of the heat.
Ricardo
I respect what you say Trackcar in relation to the bhp gains but can you explain why?
I didn't quite follow the other explanation - I'll have to think about that one - sounded like you were agreeing with me unless I picked it up wrong. The latent heat in the block you refer to is dissipated through the plenum, etc. Thermal insulation will only keep more heat in the engine as it is the sorce of the heat.
Ricardo
Ricardo Bertone said:
As well as ACT, Demon Tweeks also do a range of silicone elbows, etc. but I think they are more expensive. If you're dealing with a non-TVR specialist supplier you really will need to know 'your arse from your elbows' to ensure you get the correct diameter, etc.
Best to stick with knowns on the pipe it would certainly seem 
Not directed at me and sorry to nit pick, but
Ricardo Bertone said:
..Thermal insulation will only keep more heat in the engine as it is the sorce of the heat.
- reads like the plenum serves a valuable service in keeping the engine cool. I always thought that was the purpose of the water and radiator Ricardo, I think you've got the wrong end of the stick re the insulation. It's not placed in order to retain heat in the engine. The thermal barrier plate is sandwiched between the plenum & the engine to prevent or at least reduce the amount of heat that transfers from the engine. the rest of the insulation wraps around the intake trunking. Again this is to keep the intake charge as cool as possible. Same reason most turbo systems have intercoolers to reduce the temp of the intake charge.
Cool air denser than hot, so makes for a bigger bang & hence more power.
Pete
Cool air denser than hot, so makes for a bigger bang & hence more power.
Pete
meatball said:
...one of the things tim (ACT) mentioned was the carbon trumpets are actually longer than the standard ones.
Yes they are, it was a complete sod getting the plenum back on, past the metal trim attached to the bulkhead.
Go on...do it!!
Have a look on eBay RPI normally sell the ACT ones a little cheaper
Rich
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