What are you guys seeing in terms of issues when running the doubler pumps off a hobbs switch? I understand that when the second pump comes on the map will need adjusting.

BUT, is the transition smooth and repeatable over varying loads and throttle positions. It seems like it could be tricky to find all the transition points correctly in the non-WOT areas of the map.

 

The map should not need adjusting. The FPR should keep the pressure the same.

 

just remember to bring the second pump in soon enough that your not already overrunning the flow of the first pump, or then no matter what it will take some tweaking.

10-15psi or so seems to usually be the norm.

 

I've heard 5 psi, and 15 psi...

 

Does this really work in practice and not just theory? I thought it was not the case. It would seriously reduce my hesitations on going double pumper...

 

I know there are lots of guys on double pumpers... anyone else got info.

 

Thought I read something else on this needing some work as well, perhaps it was someone who was running out of fuel already though... can anyone else add to this?

 

people think this about the walbro too but i didn't notice any afr changes after installing my walbro. not to say people wont with a double pumper.

 

I think people who have pushed a single pump to the area where they drop pressure and consider that "tuned", and then later install a double pumper have the issue. It doesn't seem like it should mess with your A/F's unless you were dealing with fuel pressure issues before.

But I'd like someone with experience to say "that's is correct - sucka foo".

 

when installing the double pumper the air to fuels will be a bit richer! you will need to re-tune it! At least with the last 3 double pumpers Ive installed with 93 to e85 all of them needed to be re-tuned!

 

Or you can run the pump simultaneous to be safer. The only thing that you have to do is to change the FPR and return line which way to small for double pumper on low loads.

I speak from my experience. I put 2 pumper on the stock FPR and return line, and at idle i had 5 bars of pressure. Imagine how the engine worked.

I tried to open the pump at some pressure but i realise that the possibility to burn the pump or the relay is huge. The pump starts and stops hundred times per day. Another problem is that if you want to have a smooth transition, you have to start the second pump when the first is really on the max. That means to be very close of the danger zone.

I don't have to tell that if you go wot and the pump is not coming, it is not very good. Combine that with high timing and high boost and you will need a new set of pistons soon.

Bottom Line:

Does really worth a engine rebuild the price of a good fueling system, corectly dimensioned and low stress on the pumps????


On all the high power evo that i do, i go Sard. 2 fuel pumps in a buffer tank filled by the walbro 255 from the original tank. And on high-climbing cars, 2 bosch loud pumps.

I wish the turbo to fall rather that the fuel pump

Sabin

 

fail forum, deleted everything I wrote...

Anyway, long story short now: You can also increase the size in the return fitting for the correct venturi effect, but then you still have twice the noise and flow.

I think having the pump turn on at high loads is the last thing you want to do (EMS or stock ECU). Seems unpredictable and uncontrollable for a transition between gears/loads.

I didn't think about wear on the relay, but I wouldn't think that is a big issue. I wouldn't think the pump would care much either.

Mainly you would just need a smooth transition in the maps for the pumps delay in turning on and off if the FPR could not keep the pressures consistent. If you are not dropping the fuel pressure below what you expect because you are flowing enough and the FPR could do its job then things should be seamless as far as drivability is concerned. Obviously if you didn't have enough pressure in the line before then you would need a re-tune in the places that was occurring. I would just hope drivability remained pretty good...

.... but that is the question, can the FPR keep up in places we currently assume it is being overrun? (aside from the venturi mod at idle)

 

When I read the thread title my first thought was "someone is putting a 4bbl carb on their evo???" haha

Running two pumps and staging them will have no effect on tuning so long as the rest of the fuel system is correct. Fuel lines large enough to not restrict flow and an FPR that can keep up. If all is good, turning the second pump on or off will not change a thing from my experience. So if you have problems it is time to do some upgrading.

 

Set it up to turn on at a pressure you rarely see.

For example, on a street car, you will see up to 10 psi pretty often as just cruising down the freeway and going to pass a car at part throttle is likely enough to get the boost up there even on larger turbos. You only see 15+ PSI when you are getting on it heavily though, so turning it on at 15 PSI means it only turns on when you need it instead of cycling it a ton every day. The problem with this though is it may turn off between shifts causing a fuel pressure drop and spike that may mess with the tune a bit. Let's face it though, much like light bulbs, pumps typically burn out when you turn them on yet will run for a very long time if you just leave them on. Switching it off and on constantly will likely burn out the pumps faster.

On the drag strip, you're either in vacuum or boost, so you set it to turn on at a low pressure like 5 psi so that it doesn't shut off between shifts (boost pressure never drops if you drive it like a man though, so I guess it's a moot point).

I can't say much about the EVO with a double pumper, but I have seen other cars go very rich using double pumpers set at low boost levels with adjustable FPRs and large lines. The trick is to find that boost pressure that doesn't make the fuel pressure change much and doesn't make the second pump turn on unless it is needed.

 

I think somebody has switched the "." and the "1" key on your keyboard again. However what I want to know is how in the hell they wired it up so that when you hit the "1" key the "shift" button is also activated so as to print out a "!". I've read quite a few of your posts and I'm sure this has to be the issue. I've actually never seen a post made by you where the period is used properly. Its either that or your an idiot. Perhaps the latter is closer to the truth.