Discussion
I have a 1996 Griffth 500.. and am curious to know what size are the standard trumpets. Understand a 45mm trumpet base is a common modifcation... but how much bigger is 45mm over the standard ones.
I assume the same applies to the inlet manifold in the fact the standard trumpet base is matched to the standard manifold... and when moving to 45mm trumpets, a matching inlet manifold is also required( or atleast recommended!!).
Many thanks..
cinquecento said:
I have a 1996 Griffth 500.. and am curious to know what size are the standard trumpets. Understand a 45mm trumpet base is a common modifcation... but how much bigger is 45mm over the standard ones.
I assume the same applies to the inlet manifold in the fact the standard trumpet base is matched to the standard manifold... and when moving to 45mm trumpets, a matching inlet manifold is also required( or atleast recommended!!).
Many thanks..
.The 'std' trumpet size is usually 38mm,but some of the earlier 500's seem to have had 44/45mm ones from the factory(still with the awfull straight 'exhaust' pipe trumpets though!.The upgrade would be to go to 45mm if you dont already have them,and the manifold would need porting to suit,in order to make the mod worthwhile realy.Hoover. said:
not sure on trumpet siszes...... but replacement upgardes are shaped at the head tp allow smooth air flow.... the standard ones in griff are just cut tubes with no shaped tops......
The ones that look like plain old bits of exhaust pipe just shoved in are actually carefully taped and work very well. Somebody (Joolz I think) reported that they'd tried replacing them with properly formed trumpets the same bore and got no benefit at all.
GreenV8S said:
Hoover. said:
not sure on trumpet siszes...... but replacement upgardes are shaped at the head tp allow smooth air flow.... the standard ones in griff are just cut tubes with no shaped tops......
The ones that look like plain old bits of exhaust pipe just shoved in are actually carefully taped and work very well. Somebody (Joolz I think) reported that they'd tried replacing them with properly formed trumpets the same bore and got no benefit at all.
Yes the standard 500 tubes are tapered from about 47mm down to 44mm ish, Have done lots of back to back testing with these against proper flared trumpets always found a gain with trumpets, V8 developments dyno test a few years ago showed up to 9 Lb ft across the whole rev range.
Plenty of photo's of the TVR, ACT and many other trumpets and manfifolds can be found on my archive page:
www.mez.co.uk/ms12.html
Just added more photo's of an early prototype rover manifold and got some more stuff coming from JED to add also.
Dyno's pulls with ACT trumpets can be found here:
www.mez.co.uk/TuningTheRoverV8-pt3.html
Eliot.
www.mez.co.uk/ms12.html
Just added more photo's of an early prototype rover manifold and got some more stuff coming from JED to add also.
Dyno's pulls with ACT trumpets can be found here:
www.mez.co.uk/TuningTheRoverV8-pt3.html
Eliot.
I did a lot of testing with induction stuff a while ago and on a std griff 500 I insulated the inlet pipes, replaced the 90 degree elbow in silicone, tried a trumpet base isolator, large bore plenum, flared trumpets (not ACT trumpets so the results may not be representative of their trumpets, i flared them myself using the std pipes cut, welded and dollied in the vice but that did have a nice flare to them) and different air filter .. just all the usual stuff that's sold for TVRs really. My trumpets gained 2bhp on a car that went from about 260 to 280 hp with all the above mods on. The best mod by far was the trumpet base isolator and 90 degree elbow .. netting over 12hp increase for just 70 quid!! bargain.
trackcar said:
The best mod by far was the trumpet base isolator and 90 degree elbow .. netting over 12hp increase for just 70 quid!! bargain.
That sort of experience is invaluable. I do wonder whether the gains on rollers are always representative of performance gains in the real world though. I imagine that the engine bay will be ventilated far better when the vehicle is moving, so some of these measures to address heat soak might appear more effective than they really are. I'd be interested to know if anyone's done research on pressure drops and temperature rises through the intake system in the real world. I've only dabbled briefly in this on the V8S, mainly because I don't have access to rollers whenever I want to play, but I found it was possible to get sensible readings using fairly mundane temperature and pressure sensors. The main problem I found was that a lot of the behaviour is transient which makes the settling time of the instrumentation critical, and I have no way to calibrate that really. So I can see where the pressures and temperatures seems to have improved slightly, but hard to quantify the actual gains. Ultimately you end up charting speed against time and just making guesses at *why* it might have changed.
Edited by GreenV8S on Saturday 19th May 15:54
I have thought the same thing peter, so when i do things like thermal testing I have a big fan blowing across the engine bay to try and minimise the effects you're describing. i don't for one moment imagine it truly represents the effects of 70mph of road speed, but it's better than nothing. PS did you like the video in my S thread : www.pistonheads.com/gassing/topic.asp?h=0&t=384291
trackcar said:
PS did you like the video in my S thread : www.pistonheads.com/gassing/topic.asp?h=0&t=384291
Hadn't noticed it until you pointed it out. I guess it's showing my misspent youth but I was expecting to see fuel mist at the trumpets. Waddya mean you don't have upstream fuelling yet?
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