garrycol Posted November 9, 2017 Share Posted November 9, 2017 The Thor RV8 engines have a complex fuel pump, which is 'In Tank' and ECU Controlled - as such there is not fuel return from the fuel rail. I want to install a MS3X on my Thor using a different fuel tank (has a fuel return) and pump etc. From Megasquirt for V8s I have purchased a suitable 120psi fuel pump and fuel regulator that can reduce the pressure to the required 52psi that the fuel rail and injectors need. The issue I have, is where to place the fuel regulator in the fuel circuit as the fuel rail does not have a fuel return. The MS documentation has this diagram which has the style of regulator I have with fuel return etc. But as there is no fuel return on the fuel rail it will not work as is. Fuel Diagram 1 by Garry Collins, on Flickr I have changed the above diagram so there is a T piece in the fuel line before the fuel rail connected to the regulator. I have removed the fuel return from the end of the fuel rail in the above diagram so the new circuit looks like this. Fuel Diagram 2 by Garry Collins, on Flickr With this arrangement I think the regulator should be able to maintain the required 52psi between the 120psi pump and the fuel rail while still allowing the excess fuel to go back to the tank. Is there anything I have missed? Thanks Garry Quote Link to comment Share on other sites More sharing options...
Dave W Posted November 9, 2017 Share Posted November 9, 2017 I think you're giving too much credit to the Thor system, it simply has a regulator in the tank as part of the pump assembly, there's nothing special about it and can be used as is although, presumably as a result of the regulator, replacement pumps are outlandishly expensive. My guess is that they did it that way to save a few quid on pipework but then I'm a cynic... Regarding your design, the two reservations I would have are: 1) Purging air from your design will require the air being passed through the injectors, possibly leading to a lot of cranking being required to purge the air. 2) Heat soak might be an issue given that you have a dead end rather than a flowing circuit. That being said, the Thor system has a similar setup to your second option and it seems to work OK so should be fine, the schrader valve on the end of the fuel rail allows you to bleed off some air if needed (fuel pressure measuring point) although I've never needed to do it. Quote Link to comment Share on other sites More sharing options...
Quagmire Posted November 9, 2017 Share Posted November 9, 2017 (edited) Older 90's BMW's have the reg built into the filter, so you have just a single line running forward to the engine bay. This would work. Try googling for e39 fuel filters... The plus with this setup is that it's cheap for OEM quality parts, and the fpr should be at the right pressure for the ev6 injectors. Edited November 9, 2017 by Quagmire More info added Quote Link to comment Share on other sites More sharing options...
elbekko Posted November 9, 2017 Share Posted November 9, 2017 Just use the Bosch fuel pump. It's in no way ECU regulated, as others have said. The only modification it might need is changing the length of the metal strips on the side so it fits in your fuel tank. Yes, they're fairly expensive, but also pretty robust and there are aftermarket ones available. Quote Link to comment Share on other sites More sharing options...
garrycol Posted November 10, 2017 Author Share Posted November 10, 2017 Thanks for the comments - as the fuel rail and injectors are all standard Thor stuff I don't believe heating and air in the system is an issue as the same problem would occur with the standard engine. I bow to all comments on the fuel pump not being controlled by the ECU in the original setup but that differs from advice on the web and the wiring diagram does show some sort of control from the ECU but that is neither here not there for what I am trying to do. The OEM fuel pump is exceptionally expensive and does not fit my tank without major modification to the tank so that precludes using the OEM fuel pump - I am sure Nige at Megasquirt for V8s would have taken into account the pros and cons of various pump arrangements before coming up with what he has for the Thor. Quagmire - I can see what you mean about the e39 fuel filter and I will keep that in the back of my mind. Once I get the engine all up and running I might replace the standard fuel filter with an E39 with a fuel line direct to the fuel rail and see what happens - with the knowledge that the engine already works. So unless someone has a reason why what I have proposed will not work I will proceed on the lines I have proposed - if it doesnt work it will be easy to change to maybe the e39 filter/reg with little dismantling. Thanks Garry Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted November 10, 2017 Share Posted November 10, 2017 I'm sure it will be fine, no need to mount the for up at the engine though, you could put it right by the tank and reduce the return line length by loads Quote Link to comment Share on other sites More sharing options...
garrycol Posted November 10, 2017 Author Share Posted November 10, 2017 Thanks - my 101 is almost mid engined with the fuel tank just behind the engine on the outside of the chassis. The plumbing is all there just got to chase the mud wasps out of the fuel return line before I connect it all up. cheers Quote Link to comment Share on other sites More sharing options...
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