plenum mod/bodge Worthwhile????
Discussion
See
www.pistonheads.com/gassing/topic.asp?t=274296&f=8&h=0
and yes I've done it on a couple of 4.0ltr cars, 1 wedge, 1 griff and it works a treat
Matt
www.pistonheads.com/gassing/topic.asp?t=274296&f=8&h=0
and yes I've done it on a couple of 4.0ltr cars, 1 wedge, 1 griff and it works a treat
Matt
neal1980 said:
Whats the baffle plate??
It's something you buy from www.magnaparva.com unless you know what you're doing and have the resources to make your own.
If you read all of the other thread you'll see I reccommended 15-20mm off all the trumpets, first you have to remove the trumpet tubes from the ally base (use an oven to get it all hot and then wiggle out with water-pump pliers) then hacksaw off 12mm or so from the NON- flared end and then true things up on the lathe. you might find that some trumpets are already loose and rattling around inside..... seen this on a couple of cars now.
Press the shorter trumpets back in with some loctite 648 and job done
As with all tuning mods you'll get the most out of it by having the fuelling adjusted / re-mapped
Matt
>> Edited by 350matt on Thursday 1st June 16:41
Press the shorter trumpets back in with some loctite 648 and job done
As with all tuning mods you'll get the most out of it by having the fuelling adjusted / re-mapped
Matt
>> Edited by 350matt on Thursday 1st June 16:41
Matt, some plenums have tubes that are not flared at all (ie mine), just parallel sides to an abrupt termination. Any experience with these? What overall height (above the plenum deck) is aimed for? (just want to check mine have not been reduced already as some things have been done previously).
Cheers
Cheers
On the 5.0 ltr cars TVR fitted a larger bore tube (45Ø as opposed 38Ø
with a sharp edge / no flare, I think these are already shortened compared to the std rover part so probably best left alone although if you could put a flare on the end that would be worthwhile.
The insulator plate would still work though
Matt
with a sharp edge / no flare, I think these are already shortened compared to the std rover part so probably best left alone although if you could put a flare on the end that would be worthwhile. The insulator plate would still work though
Matt
This might be a silly question, but wouldn't it be simpler to raise the plenum top slightly therefore de-restricting the airflow to the trumpets without shifting the power curve up the rev rnage..?? There is quite a bit of space between the plenum top and the bonnet.
>> Edited by M@H on Friday 2nd June 10:01
>> Edited by M@H on Friday 2nd June 10:01
I agree, I wondered if there was a market for an insulating spacer between the trumpet base and the plenum top. The sort that are becoming conventional go under the trumpet base. Presumably this works better because it insulates more of the intake system. Shortening the trumpets is probably a better way to increase the clearance though, because it shortens the intake tract which means it tunes at a higher frequency.
Long and short of it, I suspect people do it the way they do because it works better.
Long and short of it, I suspect people do it the way they do because it works better.
Right you lot... 15 mins at 'leccie 180 degrees and a kitchen full of oily fumes 
The trumpets have walked right out (glad something's gone to plan for a change), and I'm ready to get chopping... haven't got easy access to a lathe or mill, so any ideas on getting a true finished edge without? Decent pipe cutter?
The trumpets have walked right out (glad something's gone to plan for a change), and I'm ready to get chopping... haven't got easy access to a lathe or mill, so any ideas on getting a true finished edge without? Decent pipe cutter?
pupp said:
Right you lot... 15 mins at 'leccie 180 degrees and a kitchen full of oily fumes
The trumpets have walked right out (glad something's gone to plan for a change), and I'm ready to get chopping... haven't got easy access to a lathe or mill, so any ideas on getting a true finished edge without? Decent pipe cutter?
Dremel?
ATG said:
Can someone explain the theory of trumpet length and power to me? I assume it is some sort of resonance thing? Also, if the optimal length for these things is shorter than the standard length, why were they manufactured "too long" in the first place? Ta!
The engine was originally designed as a stump puller which topped out at about 5000 rpm. TVR retune them to run up to rather higher revs, but keep most of the standard intake system. Shortening the intake system means it tunes at a higher frequency i.e. works better at higher rpms.
I flared the pipes in a 5 litre griff that made 280 bhp .. after flaring the ends it made 282 .. not worth the effort. the std 5 litre pipes seem to work well at hp up to around 280bhp .. over that it may well benefit from flaring but i've never had a test car making more than 280bhp to find out 
Well, as no-one came up with any brighter ideas, dived in with the trusty hacksaw and file. Quite pleased with the results and easier than I thought to get a true (enough) termination. Next Q... should the base be heated again to press back in or will cold be ok? Want to seal with a bonding agent and I'm not sure how the heat will affect that so prefer cold if the final result will be as secure.
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