Hendrik Posted March 24, 2008 Share Posted March 24, 2008 Is it worth to change the standard plenum to a 71mm ported TVR one? does it give an improvement? what are they worth? Thx H. Quote Link to comment Share on other sites More sharing options...
pugwash Posted March 24, 2008 Share Posted March 24, 2008 on a standard 3.9 it wont make a jot of difference. Standard plenums flow plenty enough for a stock 3.9, if however you have flowed the heads and changed the cam, then there "may" be a benefit at the top end. Like the twin and triple plenum setups they are really only worth it if you use the car hard all the time. If you want to spend some money get the heads ported or the rotating assembly balanced properly- both will pay dividends. Quote Link to comment Share on other sites More sharing options...
Young bobtail Rhys Posted March 24, 2008 Share Posted March 24, 2008 I think that I am right in saying that, the more modifications you do to your engine, the more each mod works with all and the end result is therefore much greater. However, ported heads, gas flowed plenums, balanced cranks, internals etc. will add upto more than your rangie is proberly worth! If you haven't already go for the easier and cheaper upgrades like the tubular manifolds, kenlowe fan, straight through air filter etc. There will be a big difference from these few, and they are alot cheaper. I have just moved my airflow meter so it now is facing the side of the bonnet with a k&n cone on the end and a vent in the side of the bonnet. Now the air travels straight to the plenum and I have to say that the throttle responce has improved and along with the tubular manifolds it is freer reving. These two mods work together quite well as it now takes in air with less restrictions and releases the gases with less restrictions. Although it would now benefit from an ecu remap to it is then set up for the mods. Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted March 24, 2008 Share Posted March 24, 2008 All you will achieve is an engine that will be difficult to tune and you will also lose some low end torque.......... That plenum would be fine if you have big valve fully ported and flowed heads, ported and matched inlet manifold, and a high compression ratio......... also it is only of any real use on engine sizes above 4.5L ............ The standard plenum is good to at least 250 - 300 bhp in terms of air flow and distribution..................... Sell it on Ebay .................. anybody with a tuned 5L will bite your hand off............. Ian Quote Link to comment Share on other sites More sharing options...
Hendrik Posted March 24, 2008 Author Share Posted March 24, 2008 All you will achieve is an engine that will be difficult to tune and you will also lose some low end torque.......... That plenum would be fine if you have big valve fully ported and flowed heads, ported and matched inlet manifold, and a high compression ratio......... also it is only of any real use on engine sizes above 4.5L ............ The standard plenum is good to at least 250 - 300 bhp in terms of air flow and distribution..................... Sell it on Ebay .................. anybody with a tuned 5L will bite your hand off............. Ian Thats the answer I was looking for! Thanks (again) Ian! rgds H. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted March 24, 2008 Share Posted March 24, 2008 ^^^^ As they all say Big bore plenum must also have big trumpets and ported inlet manifold and ported heads, otherwise its as mucgh use as trying to f*rt into a hosepipe. Going rate is around £100-£150 for a good 2nd hand one, normally they are from memory 72mm not 71mm..... and upwards for the real exotic (and then triple entries) ? Nige Quote Link to comment Share on other sites More sharing options...
general-confusion Posted March 25, 2008 Share Posted March 25, 2008 The man to talk to about this is Tim Lamont at www.actproducts.co.uk what he doesnt know isn't worth knowing Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted March 25, 2008 Share Posted March 25, 2008 Agreed............. Tim produces some exceedingly nice carbon fiber trumpets and plenum's ........... again, these would be absolutely wasted on a standard 3.9. Tim can often be found lurking on Piston Heads ................and he is a throughly nice all round bloke to talk to............... Ian Quote Link to comment Share on other sites More sharing options...
duni Posted March 27, 2008 Share Posted March 27, 2008 Agreed............. Tim produces some exceedingly nice carbon fiber trumpets and plenum's ........... again, these would be absolutely wasted on a standard 3.9.Tim can often be found lurking on Piston Heads ................and he is a throughly nice all round bloke to talk to............... hi .. how do you tell difference between standard plenum and modified? Ian Quote Link to comment Share on other sites More sharing options...
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