GordonW Posted October 17, 2011 Share Posted October 17, 2011 In trying to do the sum I need to know the distance from the inlet manifold flange to the centre of the inlet valve, so that I can add it to the bits I do know the length of, anyone know please? Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 18, 2011 Share Posted October 18, 2011 not sure how accurately you need this but you could call SBD or QED as they are likely to have a bare head that they could measure. You could also try Simon Armstrong at Ultimate Performance. Mine's on the car so I doubt I could do it accurately enough for your purpose but, if you only need it to the nearest 5 - 10mm, I'm happy to give you a reasonable estimate. Paul Link to comment Share on other sites More sharing options...
GordonW Posted October 18, 2011 Author Share Posted October 18, 2011 Hi Paul, yes good idea re the specialists I just thought that since so much store is put by the overall length someone out there might know the head element. The expensive option of rolling road hours and a boxfull of trumpet options is OK if you've got a boxfull of cash but I would like to go close to a theroretical optimum as a first stage economically. If I get any joy I'll let you know if it's of any interest. What would your guesstimate be? Link to comment Share on other sites More sharing options...
alan c Posted October 18, 2011 Share Posted October 18, 2011 Hi Not in UK at present but I have a spare head on the workbench at home that I could measure in a day or so if that helps. Not sure right now how I would do it though. Also have three different sets of trumpets so be interested to hear what you think the optimum is? Did you see the recent link to the article on various trumpet lengths on the Emerald web site? Alan Link to comment Share on other sites More sharing options...
Paul Deslandes Posted October 18, 2011 Share Posted October 18, 2011 Dave Walker wrote an article for CCC a few years ago which was aimed at demonstrating that injection is infinitely better than carbs but also shows how induction length affects torque and power. The tests were done on a 2litre Vx and can be found here. I've attempted to measure roughly the lengths which are as follows: Trumpet = 90mm, TB = 115mm, manifold (gas-flowed standard CC Weber type) = 70mm, manifold/head interface to valve centre = 80mm. Bear in mind that the manifold is cranked so this figure is a rough mean length and the head valve measurement could be quite a bit out too as I can't get inside it and varies a bit from cylinder to cylinder. But it will give you the basis for a first estimate. The length of the trumpets, all other things being constant, will move the torque curve up and down the rev range, as will exhaust design. Changing from a 4-into-1 to a 4-into-2-into-1 exhaust made a huge difference to my engine shifting the usable torque lower limit down to 2500rpm and 75% of max available from 3300 to 8250 with its peak at 5250. I'd be very interested to hear what you calculations throw up. Paul Edited by - Paul Deslandes on 18 Oct 2011 18:20:27 Link to comment Share on other sites More sharing options...
GordonW Posted October 20, 2011 Author Share Posted October 20, 2011 Alan, yes thanks that would be interesting if you could. The ever helpful SBD say they will try to help also if they can find a loose head, I'll let you know if they do. Link to comment Share on other sites More sharing options...
alan c Posted October 20, 2011 Share Posted October 20, 2011 Hi I will have a go over the weekend but I think Paul has already given you an answer above but will see if get anything different. The article I mentioned earlier is here:- http://www.emeraldm3d.com/articles/emr-adj-length-intake.html I can never get links to work Alan Link to comment Share on other sites More sharing options...
GordonW Posted October 24, 2011 Author Share Posted October 24, 2011 Thanks all for the input, Alan if they work well the perfect answer to induction length experimentation is Emeralds new adjustables so I have ordered a set. Many thanks for the tip. The conversion from carbs is almost complete and the 'guesswork' map supplied by the excellent Paul Exon has got me running and seems good enough to get me to the rollers, I'm going to put a good old gunson colour tune on it to see if it is dangerously out first. (A mechanic mate quite rates them) My interest in the overall induction length was fuelled (sorry) by the views expressed by a couple of knowledgables that 305 or 350 mm (depending which one you listen to)was a good point to start so I was trying to get to 325 ish with my first set up. There do seem to some consistents as I'm sure you know, longer the better is one mantra. All good fun, hope I can get to the two steves. In the overall mix will be the noise issue, bonnet hole size and avoiding pedestrians with the trumpets. ITG made up a back plate with offset holes to lower the filter and the comparatively small bell mouth of the Emerald trumpet will happily allow the filter over their top lip which was a problem with the wide bell mouth alternative, however the top clip on the filter now fouls the fuel rail so a temp fix will be needed while the wallet recovers. Link to comment Share on other sites More sharing options...
EFA Posted October 25, 2011 Share Posted October 25, 2011 "ever helpful SBD" - Oxymoron. Link to comment Share on other sites More sharing options...
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