Andrew Cleland Posted January 23, 2011 Share Posted January 23, 2011 [if you're wondering about my other recent thread on tuning my MS, I've decided that as I have a Thor intake waiting to go onto the engine it made more sense to fit in now rather than sort-out the hotwire manifold and then have to start again when I fitted the Thor manifold]. Anyhow, I'm working on fitting a Thor inlet manifold to my Megasquirted 3.9 in the 110 and have most of the bits together. I've dealt with enlarging the water take-off to take a thermostat but am now looking at the fuel rail. The Thor fuel rail is the 'returnless' type (just a single pipe going into it) and uses the ECU in combination with a fuel pressure sensor and the fuel pump to keep the pressure constant rather than a fuel pressure regulator and return line. I can't see anyway for the MS to control this setup as it doesn't know about fuel pressure (and in anycase, I don't want to buy a new fuel pump). One option would be to replace the Thor fuel rail with the hotwire fuel rail and regulator. There are two hitches with this - firstly I'd need to use the hotwire injectors as they're physically bigger than the Thor injectors (which won't reach the hotwire fuel rail) which I'd rather not do as the Thor injectors are younger, the nicer 4-hole type and are more compact, which helps with fitting the LPG injectors I have sitting here. Secondly the fittings to bolt down the hotwire fuel rail are in a different place to the holes on the Thor manifold, so they'll need to be carefully cut off and then brazed back on in the correct place. Option two, my preferred one, is to use the Thor fuel rail and injectors and find some way of controlling the fuel pressure. There seem to be aftermarket regulators with a pair of inlet/outlet ports, along with a separate return port, which suggests that they might work for a situation like this. DIYAutotune sells one brand, SX Performance, which makes me think that they might be used with Megasquirt. I was wondering though if it would be possible to use the hotwire regulator stand-alone by puting a T-piece into the high-pressure feed pipe just before the regulator to feed the Thor fuel rail and then using the normal HP feed and LP return pipes. I can't be the first person to have used MS with a Thor manifold though, so what have other's done? Cheers, AndyC. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 23, 2011 Share Posted January 23, 2011 I was wondering though if it would be possible to use the hotwire regulator stand-alone by puting a T-piece into the high-pressure feed pipe just before the regulator to feed the Thor fuel rail and then using the normal HP feed and LP return pipes. I see no reason why this wouldn't work, assuming it all physically bolts up. You are right too, there is a post on here about MS and Thor somewhere... so you are not the first. Quote Link to comment Share on other sites More sharing options...
Dave W Posted January 23, 2011 Share Posted January 23, 2011 I use a Mallory fuel pressure regulator on mine, it's adjustable and has a feed pipe, a return pipe and an outlet. It also has provision for vacuum adjustment although I've not used that as I prefer to have the MS adjust the fuelling. Either the 4305M or the 4307M will do the job, depending on your desired fuel rail pressure. Quote Link to comment Share on other sites More sharing options...
Andrew Cleland Posted January 24, 2011 Author Share Posted January 24, 2011 Thanks both. I'll have a shot with rigging the hotwire regulator, if not, one of those Mallory jobbies it is. The fuel rail does have a take-off for a pressure gauge, so I can keep an eye on it and see how things go. Cheers, Andrew. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 24, 2011 Share Posted January 24, 2011 I thought the fuel pump just had its own internal regulator (ie in-tank, and overspills straight back into the tank rather than going all the way to the engine bay & back). An earlier Hotwire fuel rail & reg should work fine. Quote Link to comment Share on other sites More sharing options...
Andrew Cleland Posted January 25, 2011 Author Share Posted January 25, 2011 I thought the fuel pump just had its own internal regulator (ie in-tank, and overspills straight back into the tank rather than going all the way to the engine bay & back). An earlier Hotwire fuel rail & reg should work fine. I think you might be right after having read through the RAVE section (again). I was thrown by the presence of a fuel pressure sensor, which I'd assumed was involved in fuel rail pressure control (like most petrol Fords, which PWM the pump to control pressure) but I think it might actually be for the EVAP system, rather than pressure control. I plan on hooking-up the hotwire reg and seeing how that goes. Cheers, Andrew. Quote Link to comment Share on other sites More sharing options...
Escape Posted January 28, 2011 Share Posted January 28, 2011 I think Quentin used the fuel rail and injectors from a broken Bosch engine we had lying around when he put MS on his 3.5 flapper. I'll check. Quote Link to comment Share on other sites More sharing options...
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