Looking for experiences with Double Pumpers

[granatl]

I'm kicking the tires on buying a Double Pumper. I'm fairly sure that I'm right on the edge of what my single Walboro 340 can handle. The car can slip into the very high 11's on my street chip (Extender Extreme) now using pump gas, and I've never even tried the race chip (another EE). I have the boost set as low as it will go (18 psi) and still see 1600+ EGT's (and then quickly get out of it). I never think to check the A/F ratio on the LM-1. To boot, the sending unit in mine is so bad, it will read "10" when I first turn the key on [which seems fairly close] but then when I start the car it shows "F"

Anyhow, I'm trying to talk myself into this. Part of me thinks that this setup is tricky to tune, causing a rich spike as the 2nd pump kicks on. Those that run this, please chime in on your experiences. Also, what PSI do you choose for the 2nd pump? This is a 99% street car. Mods in the signature.

[RUQWKNF27]

Got one here! 2nd pump starts @ 15lbs. No problems in 1.5 yrs!

[pacecarta]

like said the second pump is run off a hobbs switch activated by boost and comes on at 15# boost or so , you can get an adjustable hobbs and start it even sooner , mine is an adjustable hobbs
as for 1600 egt thats where mine usually goes a little faster , i normally run 1585 with an 11.2 AF , Im running wideband correction so second pump turnon really isnt an issue
you shouldnt need duals yet at your level . single pump should support 600hp and should have no problem supporting mid- high 10s
normally you dont need to consider twins till 10.5
with alky a single 340 has gone 10.10

could be other things causing high egt
too rich - fuel being burned in the exhaust


do you see 1psi per 1 lb boost increase in FP when under boost ?
with 45 base FP psi (line off) you should see 63 psi FP(line on of course) at 18# boost , and it needs to stay at 63

oh and 83# injectors and that turbo you need dual pumps (or external race pump) to reach their potential ,about the most a single pump will support to 100% duty is a 55# injector, but even with 55s and one pump you could be doing mid 10s unless you're way rich on the fueling

[WSLN 6]

Yep, my single pump isn't done yet, no wideband issues or leaning out past 140mph, this is with alky though. If you are running racegas and are over 130mph it would be a very smart move to upgrade...

[GSX-PKV]

We have an ATR Doubel Pumper and have had no problems at all in 5 years of mostly street use.

[daviss]

I've got one also and it's hooked into a Hobbs @ 15psi. Wired in an led in the pillar pod to know when it comes on. Now with the alky and the shift light, when ever I get into boost, it looks like christmas.

Shouldn't have a fp spike when the pump comes on. Pressure will still be regulated. Just keeps the regulator fed so you don't go lean. It was on the car when I got it so I haven't messed with it but I wouldn't see the need for your level assuming your still seeing adequate fp with reference to boost.

I also had the relay go bad for #2 pump and still went mid 11's.

Hope this helps
Steve

[Razor]

Single 340 and alky have already gone 9.9 at 138.

For 120 MPH Buick.. waste of money.

[granatl]

I do have alky injection. I'll try to get the car out for a run soon to check FP psi, and A/F ratio.

[Razor]

Originally Posted by granatl

I do have alky injection. I'll try to get the car out for a run soon to check FP psi, and A/F ratio.

Then aside from the bum sender.. I would say leave things alone.

[turbofabricator]

You sound like you have a digital dash, and if so, then the double pumpers sold out there will not work as fas a sending unit is concerned. I have not been able to find a new digital dash sending unit anywhere. If anyone else has an answer, please chime in.

[granatl]

Someone wrote a detailed pictorial guide on how to fix the sending unit. I have it printed out at home, but have been too lazy to try it. That's strange that GM would use 2 different sending units. I do have a digital dash.

[Jack Armstrong]

Originally Posted by turbofabricator

I have not been able to find a new digital dash sending unit anywhere.

Ken,

Even John Spina @ Casper's Electronics

doesn't have one and/or knows no source for one?

[Jack Armstrong]

Beyond the Hobbs switch,

What are the various other ways to trigger the 2nd pump? TIA!

[Scott Atk]

Jack, Give me a call. I have some experience going much much faster with a single pump. I've also been able to repair a few sending units.

[8AV8]

What about the second pump on a manual switch? Just turn on the switch after the burnout?

I have a fear of a Hobbs switch failing. Don't know why...

[Slow91z]

Originally Posted by 8AV8

What about the second pump on a manual switch? Just turn on the switch after the burnout?

I have a fear of a Hobbs switch failing. Don't know why...

The problem with that is if you manually turn on the pump at idle your fuel pressure will run wild...Car will go rich and best case scenario will spool worse.

[8AV8]

Originally Posted by Slow91z

The problem with that is if you manually turn on the pump at idle your fuel pressure will run wild...Car will go rich and best case scenario will spool worse.

The regulator can't control idle fuel pressure with both pumps on?

[Slow91z]

The problem isn't the regulator it's the return line, it's too small.

This is the whole reason for the 2 pump setup is so you can turn on the 2nd one at higher boost when you are using more fuel so less needs to be returned to the tank...That and it works nicely with the stock tank...Other wise it would be easy to just throw a Big ass pump on there and roll.

[Slow91z]

Oh BTW I'm sure you could run the 2nd pump off of a RPM switch and a relay if you really don't like Hobbs switches.