I am about to add a second fuel pump (walbro 255lph inline). How much will this change my tune? Just out of curiosity and will I be able to start the car to at least drive it somewhere to be tuned??

PJ

 

Shouldn't be a problem to start and drive. The only thing i would think is that it would be rich on the big end.

 

yea had the same thought process I guess we will find out lol

PJ

 

Take it from me, it will change it completely. You will probably be able to drive it to be tuned but it will be beyond Pig Rich!

 

which twin pump setup are you using?

 

having one custom made with an inline instead of intank pump.

 

If you have a good fuel pressure regulator, and the fuel pressure has not changed at all, you should be good to go as far as driving and start, but it is possible that if you were running out of fuel flow up top before and were tuned for this, you will need to recalibrate.

 

If you have both pumps ON all the time, the tune will change drastically even with a good regulator, you will have to upgrade the return line too or the pressure is going to go up at idle.

Driving it to get it tuned should be possible either way.

I'd recommend using either a pressure switch or a relay to trigger your second pump. Our double pumper uses a pressure switch for the secondary pump. Idle and part throttle/low boost are uneffected doing it like that.

 

dave,
where could i aquire a pressure switch like this. I was going to run them both all the time but now understand why not. Any help would be appreciated. thanks

 

Hobbs switches available at auto parts stores are pretty popular. Others can be found online with all kinds of variations in their specs.

 

Yes, you can get them just about anywhere, just find a Hobbs switch. We do not sell any of the parts to our double pumpers seperately. Do a quick search for Hobbs switch.

 

awesome thanks for the input guys i will get one

PJ

 

www.atpturbo.com

Buy one, your gunna need a T Vacuum fittting, vacuum line and some electrical line(i think 8 guage) to wire it all up.

Scorke

 

thanks scorke. Anyone have input on what pressure to set the second pump to kick on?


PJ

 

I would do it where ever your turbo is still climbing into boost slowly before it is spooling really quick, however higher than low boost numbers that you hit when just mildly cruising.

I am going to set mine for 10-12 psi opening, even though it is going to be increasing boost/rpm quickly at that high, I don't want to have to deal with tuning for the switchover at boost leves were I will be when just slightly into the throttle.

*I don't know if this is a good, advisable, or bad idea, just what I am doing...


Scorke