The MegaSquirt Project has experienced explosive growth other the years, with hundreds of new MS installations occurring every week - a phenomenal success! MegaSquirt has been successfully used in all aspects of Internal Combustion engine applications including R&D, Industry, Race, and Research. The MS project has transformed itself from a simple R&D project into a full-featured mature engine control system. To reflect this the support structure has also changed to meet the needs of MegaSquirt Users.
Moving forward, the R&D forums for MegaSquirt project are in a read-only mode - no new forum posts are accepted.
However the forums will remain available for view, they still contain a wealth of information on how MegaSquirt works, how it is installed and used. Feel free to search the forums for information, facts, and overview.While the R&D forum traffic has slowed in recent years, this is not at all a reflection of Megasquirt users, which continue to grow year after year. What has changed is that the method of MegaSquirt support today has rapidly moved to Facebook, this is where the vast majority of interaction is happening now. For those not on Facebook the msextra forums is another place for product support. Finally, for product selection assistance, all of the MegaSquirt vendors are there to help you select a system, along with all of the required pieces to make it complete.
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jonfx4com wrote:And before anyone tells me that in http://www.sdsefi.com/techsurge.htm the fuel bleeding out of the fuel pressure reg is going back into the swirl pot- forget it! After 5 mins in traffic the recirculating fuel gets so hot it starts vaporizing in the lines
I understand the argument here. However.. if the fuel was vaporizing (I read this as the fuel turning into a gas), wouldn't it float to the top of the surge tank and return to the fuel tank?
No not really, it just turns the entire contents of the surge tank into a homegenous mixture of fuel and vapour. For sure once you stop the pumps running it settle out within a few seconds but the flow (and hence the problem) is highest when the engine is using the least fuel, that is when idling in traffic and that keeps it all mixed up quite nicely.
jonfx4com wrote:No not really, it just turns the entire contents of the surge tank into a homegenous mixture of fuel and vapour. For sure once you stop the pumps running it settle out within a few seconds but the flow (and hence the problem) is highest when the engine is using the least fuel, that is when idling in traffic and that keeps it all mixed up quite nicely.
Perhaps a good reason then not to skimp on the surge tank size.
Do you have an internal or external high pressure pump for your surge tank setup? I wonder if an external pump wouldn't heat up the fuel as much as a submersed pump might.
1995 Ford Probe GT ~ Megasquirted & Boosted
275whp/242wtq @ 5.5psi ---- 317whp/287wtq @ 8.5psi
^^^ (thanks to MSnS-E and dyno tuning by me!)
2003 GSX1300R (Hayabusa)
yes, a big tank will help if you have the space. Also carefull attention to the positions and angles of the pipes would help, as would a refridgerator or running the pipes to the nearest ice cored planet, but all this compared to mounting the pump next to or in the tank and running in a fuel return to the tank like the oem's do? Seems like whole lot of work for nothing. Also worth thinking about what happens when "a very small leak" of fuel, possibly at high pressure happens under the hood. There are many areas to save some work and some money on a car but imho this area is not one of them, especially when it will cost the same or more than doing the job right.
As mentioned earlier, it is possible to convert older fuel tanks to accept a modern drop-in efi pump setup. Here are pics of the pump assembly, mounting flange, and slosh cup from a late 80's rx-7. Swapping these bits onto my 1979 fuel tank is on the project list for this fall. This conversion will reduce the number of fuel line connections to about 1/4 of what I have right now, and also reduce the chatter noise from my two external pumps.
Roger.
1979 Mazda RX-7, running MSnSExtra029L for fuel and spark control on a turbocharged, intercooled, and
(of course!) injected 13B rotary.
jonfx4com wrote:compared to mounting the pump next to or in the tank and running in a fuel return to the tank like the oem's do? Seems like whole lot of work for nothing.
Wouldn't you need to have the surge go back to the tank even if you did start with a full surge tank in the event the low pressure pump pushed air into the surge tank?
Previously, I had always planned to go back to the tank at the top of the surge tank.
1995 Ford Probe GT ~ Megasquirted & Boosted
275whp/242wtq @ 5.5psi ---- 317whp/287wtq @ 8.5psi
^^^ (thanks to MSnS-E and dyno tuning by me!)
2003 GSX1300R (Hayabusa)
Yes, if you use a surge tank the return must come from the top but if you use a pump in the tank or level with the bottom of the tank you remove the need as it becomes very unlikley you will suck a bubble. An isolated bubble is not too problematic as the majority of the fuel in an oem setup goes right round the circuit and only a small amount of the total is injected so the bubble flys through the fuel rail and down the return very fast. I would think if you do go with a surge tank you ideally want the cool and non aerated fuel from the tank to come in low down on the swirl pot to displace any hot aerated fuel upwards towards the tank return, basically to assist the natural tendency of the hot fuel to rise. Yo also want the hot fuel from the regulator aimed such that it in not inclined to mix with the cool fuel lower down. Of course unless your LP pump is higher capacity then your HP pump the heat will still build up, just more slowly as you will not be changing the fuel as often as you circulate it through the rail.
Also, following cooling system swirl pot design, use a cylindrical tank, and feed the high velocity return fuel in tangentially part way up the tank. This swirling action forces the vapour bubbles to the centre where they can rise up to the vent line that returns to the main tank.
1979 Mazda RX-7, running MSnSExtra029L for fuel and spark control on a turbocharged, intercooled, and
(of course!) injected 13B rotary.
renns wrote:Also, following cooling system swirl pot design, use a cylindrical tank, and feed the high velocity return fuel in tangentially part way up the tank. This swirling action forces the vapour bubbles to the centre where they can rise up to the vent line that returns to the main tank.
That was a pain to weld up, but that's what I did. Both the return from the regulator and the inlet from the low pressure pump hit the surge tank tangentially near the top, so no bubbles are introduced within 7 inches of the bottom of the surge tank where the HP inlet is located. I also used a vane near the bottom of the tank, at the HP inlet to minimize the swirl right at the pump inlet.
FYI - My tank is on the smaller side. I used a piece of chain link fence post. Only 1 5/8 inches in diameter, but about 10 inches high. It's about 2/3 of a liter in capacity and should provide in excess of 10 seconds of fuel, assuming no fuel is added from the tank.
Jack
Good judgment comes from experience.
And where does experience come from?
Experience comes from bad judgment.
. . . . . . . Mark Twain
