JohnD Posted November 20, 2015 Share Posted November 20, 2015 Yes, Nick's not mine - and urge's. I only expanded the diameter of my plenum, from 3 to 6" . To do so, I cut off the tube, leaving the original bell mouths on a strip of metal that I attached the new, wider tube to. See pic. I assumed that Triumph knew whereof they manufactured (a big presumption, as it was 50 years ago, but they did have lot of empirical experience) and it made my fabrication a lot easier! John Link to comment Share on other sites More sharing options...
Urge Posted November 20, 2015 Share Posted November 20, 2015 I still can't agree with the protruding bell mouths in nicks plenum. My suggestion to use a ring doughnut type bell mouth attached to a flat rear deck has merit. Put simply. Look down nicks plenum through the metering device. How much of the opening in the bell mouth can you see. If you push these bell mouths further in you see less. Pull them out (so they stick out less) you see more of the bell mouth opening. The bell mouth can't use air in the plenum that's downstream from the metering device. It would cause a vacuum. The air will come from the least residence. Thats the opening of the metering device. Link to comment Share on other sites More sharing options...
Urge Posted November 20, 2015 Share Posted November 20, 2015 The bell mouth can't use air that's downstream of the bell mouth. It takes it frim the direction of the metering device. If it used air in the plenum down stream of the bell mouth from the metering device. It would cause a vacuum Link to comment Share on other sites More sharing options...
Millstone10 Posted November 24, 2015 Share Posted November 24, 2015 Ummm. But where is the lowest pressure... Past the bell mouth or created by the engine in the bell mouth ... Have a think about that one. Link to comment Share on other sites More sharing options...
Urge Posted November 24, 2015 Share Posted November 24, 2015 I am referring to what's happening inside the plenum housing. As I have pointed out before. It's not an air filter. The bell mouths can't use air from all directions as they do in a air filter. Each bell mouth in turn draws air from the direction of the metering device. The bell mouth is not fully used because of this Link to comment Share on other sites More sharing options...
Nick Jones Posted November 24, 2015 Author Share Posted November 24, 2015 I disagree. The point of the plenum is to be a sufficiently large buffer to mimic an atmospheric entry (albeit at lower pressure when at part throttle) so the bell mouths are drawing from all around. Of course, this will depend a bit on the plenum volume and presumably why best top end power is made with bigger plenums (which can maintain this effect even at high flows) with smaller ones giving better low end torque and sharper response. Nick Link to comment Share on other sites More sharing options...
Urge Posted November 25, 2015 Share Posted November 25, 2015 Ok . So if we was to just talk about bell mouth number 3. The third bell mouth away from the metering device/butterfly. If this bell mouth was to draw air from all around its circumference. The air that's just been used by the engine/bell mouth would need to be replaced. How is it going to get from the metering device, past the bell mouth to the opposite side of the bell mouth of the metering device? ????? Don't forget. If the air is taken and used. It will need to be replaced or you have a vacuum. Take for instance a inlet valve in the head. On a flow bench it seems to work Ok. Put the head on a block. And the bore can cause the same valuve to only flow part of its opening. This is valuve shrouding by the bore. The same kind of thing is happening because of the pressures difference in the plenum. Said proposed plenum is on the small size. The fact that it has walls/ sides means the air finds it easier to come in a direct line from metering device direct to bell mouth that's in use. Ever seem a lake with a stream running through the middle. The sides of the lakes can be very still water. It's has a lot to do with the speed of travel. Link to comment Share on other sites More sharing options...
motov8id Posted November 29, 2015 Share Posted November 29, 2015 (edited) when the air flow into the intake runner changes direction it delaminates at the bend. also if the plenum volume is too large you will have poor throttle response. maybe a solution This is for a restrictor race series but interesting research https://www.academia.edu/4839777/Intake_Manifold_Design_using_Computational_Fluid_Dynamics Edited November 29, 2015 by motov8id Link to comment Share on other sites More sharing options...
Urge Posted November 29, 2015 Share Posted November 29, 2015 Isn't what's going on in pic one exactly what I have been saying!!!!! A stream running through a lake. The bell mouth that's getting the air is NOT seeing air from all its curcumfrence And what's happening in that pic is from a middle postioned opening port ( metering device ) Not like nicks one. That's at 90deg to all the bell mouths. Have not read the link yet Link to comment Share on other sites More sharing options...
motov8id Posted November 29, 2015 Share Posted November 29, 2015 I didn't want to post too many pics so added the link They have an end fed plenum that shows each successive runner has less velocity so less cylinder filling. Maybe a tapered plenum could help that. Link to comment Share on other sites More sharing options...
Urge Posted November 30, 2015 Share Posted November 30, 2015 Well hopefully there's lots of info that has already been said. Inc yr link so as to help nick achieve what he wants Link to comment Share on other sites More sharing options...
esxefi Posted December 2, 2015 Share Posted December 2, 2015 I wouldn't overly worry about perfect air metering,... https://www.youtube.com/watch?v=c8hqoE1_7bA https://www.youtube.com/watch?v=vcyT18qk8ls the speed the air has to travel to get through this lot must be phenomenal. Link to comment Share on other sites More sharing options...
motov8id Posted December 4, 2015 Share Posted December 4, 2015 Great video. I was waiting for it to explode. 14k is an amazing rpm. The valve and spring don't rotate until a very high rpm. I wonder if is related to the type of spring used to attain that high engine speed? Link to comment Share on other sites More sharing options...
Urge Posted December 4, 2015 Share Posted December 4, 2015 The ramping of the cam lobe will play a part in this. At very high rpm with a sharp rise in cam lobe you will of course have valve flutter issues to deal with Link to comment Share on other sites More sharing options...
Nick Jones Posted December 18, 2015 Author Share Posted December 18, 2015 Got a couple mostly stuck together now Runners, flanges and injector pockets are identical. Plenum and treatment of the plenum - runner join are different This one you've seen before This one has the flares sat on top of the backplate, welded round then dressed into a full curve. Right royal PITA! Wished I'd welded 'em flush - would have been much easier to clean up. Nick Link to comment Share on other sites More sharing options...
esxefi Posted December 19, 2015 Share Posted December 19, 2015 nick,you know the easy way round it,..... stick a turbo on there Link to comment Share on other sites More sharing options...
Urge Posted December 19, 2015 Share Posted December 19, 2015 One reason why I am putting a turbo on my gt6 mk1 I have the latter head from a mk3 gt6. Ports are far to big for a 2 liter. Probably triumph took the latter gt6 head from a tr6 and or pi Cause the ports are just to big for the gt6. No help to you nick. Was just saying. Re yr manifold. The flate plate were the inlet pipes come in. We're you welded up and filled a bellmouth. Why didn't you bolt a doughnut bell mouth there in stead. I did mention this way back in this post. Could av saved you lots of work Link to comment Share on other sites More sharing options...
Nick Jones Posted December 19, 2015 Author Share Posted December 19, 2015 Ports are the same sizes on all the later 6 cyl heads. That is, all the ones common with the 2.5 from about 1969 on. Yes they are bigger than the Mk1 2000/GT6/Vitesse head ports, but I wouldn't have said hugely oversize. I've occasionally considered turbo'ing the Vitesse. Quite alot of packaging issues and added complexity, so much easier to just go 2.5 if I just wanted the extra grunt - with the usual concerns about busting transmission bits. Truth is, it's fast enough most of the time. It's a road car and a floppy old convertible at that. Spitfire, if looking for more than 15 - 20 extra bhp I'd stick a modern lightweight engine in there like Zetec SE, MX5 or Suzuki Swift GTi. Nick Link to comment Share on other sites More sharing options...
Nick Jones Posted January 10, 2016 Author Share Posted January 10, 2016 Little bit more this weekend. Fuel rail is now pretty much done bar pressure/leak testing (will be done with compressed air in the bath I expect!), a thorough swilling out and some paint. It's a Focus SE regulator though there are other cars that use items which are the same size and shape. Just need to come up with an elegant way of fixing the fuel rail to the manifold now. Nick Link to comment Share on other sites More sharing options...
Sprint95m Posted January 12, 2016 Share Posted January 12, 2016 Hmmm yes, what a fascinating topic! As much as I would try to fully understand the science, I know I would almost certainly end up with adopting a try it and see approach.... Ian. Link to comment Share on other sites More sharing options...
Nick Jones Posted January 12, 2016 Author Share Posted January 12, 2016 It is a big subject. However, I do think that alot of the really intricate detail ends up chasing the only the last few percent - especially as when converting old carb-fed cars to injection the packaging constraints like fitting it around the brake servo and under the bonnet. Looking forward to getting it on the car. One one in question is a well modded 1300 which currently runs a single Weber 45 and gives appalling emissions readings and rather crabby bottom end performance though it goes pretty well once the revs get up. It already has Megajolt on it (which made it less crabby low down) so we'll get a good idea of the effects of the injection. Nick Link to comment Share on other sites More sharing options...
JohnD Posted January 13, 2016 Share Posted January 13, 2016 Part of the difficulty of DiY injection is the accuracy needed in fabricating the common rail. Why is a solid common rail required? All moderns have one, but why? It can ensure that all the injectors receive the same pressure, by feeding them from the plenum of the rail, but why not a slightly remote plenum, with hoses between that and the injectors? Equal length hoses=equal pressures Boom! Fabrication is suddenly easier, although you then need a mans of attaching the hoses to the injectors. John Link to comment Share on other sites More sharing options...
esxefi Posted January 13, 2016 Share Posted January 13, 2016 ......and keeping the injectors in their holes. easier to use the solid rail to cover both purposes.(speed of installation on a production line is probably more relevant for using a solid rail) injectors have 'o' rings for sealing so there is a very tiny allowance for misalignment during construction. Link to comment Share on other sites More sharing options...
Nick Jones Posted January 13, 2016 Author Share Posted January 13, 2016 You can do it that way John. In fact a number of the older L-Jetronic installs are like that. I think the reason for the now more or less universal direct interface between fuel rail and injector is that it is simpler for mass production and uses fewer parts. The fuel rail is also used to hold the injectors in place. Problem for the DIYer today wanting to connect to the injectors with hose is finding injectors with hose barbs as they were used on just a few high-end vehicles mainly in the 70s. Most recent I know of is the Carlton 6 cylinder from the early 80s and they are all but extinct. Also low impedance which causes other complications. Fabrication accuracy is not that big a deal. Getting a leak tight seal (weld) is. Might try silver soldering next time! There is always the Ross Machine extruded aluminium rail. Nick Link to comment Share on other sites More sharing options...
JohnD Posted January 13, 2016 Share Posted January 13, 2016 (edited) Thanks, Nick, and esxefi, Always glad of a challenge, how about Jaguar XJ6 injectors: http://www.ebay.co.uk/itm/261877313255?clk_rvr_id=966046138278&rmvSB=true 1983, I believe. Also XJS/XJ12: http://www.ebay.co.uk/itm/261877313255?clk_rvr_id=966046138278&rmvSB=true Or is the length of hose to protect the seal in transit? Or, our own, our very own, TR7 injectors, that have exactly as I describe (I only have my genius to declare!) a short, equal length hose between a fuel rail plenum and the injector! Those were so easy to find that I'm sure I've got it wrong, somehow! John Edited January 13, 2016 by JohnD Link to comment Share on other sites More sharing options...
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