3800Pro Forums banner
1 - 8 of 8 Posts

·
Registered
Joined
·
106 Posts
Discussion Starter · #1 ·
I just noticed the Caspers dual fuel pump rewire kit on the website. I have just put in a Walbro to run with my Kenne Bell Boost a Pump and 65# injectors. What inline pump are you guys recommending as a 2nd pump, where are you typically mounting the inline pump, and are you recommending a high flow fuel filter as well or are you sticking with the stock pump?

My blower seems to move some air and I want to be sure I can move plenty of fuel to keep up. The last time at the track, I had my boost a pump turned all the way up and when pushing 20psi, I ran out of fuel at the end of 2nd and 3rd gear was full of O2's of .840 :eek:
 

·
Registered
Joined
·
106 Posts
Discussion Starter · #2 ·
umm k, I guess nobody does this? :(
 

·
Registered
Joined
·
346 Posts
Sorry Mike I missed this until now. We had an issue about a year ago where a single in-tank Walbro was not flowing enough fuel for some of the INTENSE cars. A second pump in series will help support more horsepower and I had worked out the calculatiuons. Most people assume that second pump in series won't help, but that's not the case. It has to do with the fact that each pump will push against a reduced fuel pressure and will be able to flow more fuel. In other words, if under boost you're calling for 70 psi of FP, one pump may see 40 and the other may see 30 which will allow each of them to pass more fuel that just one could at 70. If you're interested I could dig up the calculations for you. They will allow you to calculate just how much flow you can get, how much hp it will support, and just what fraction of the FP load each of the two pumps will carry. (That is, until you hit the next bottleneck, see below)

I looked all over and there are two pumps I liked. There is an external Walbro that flows 255 lph, and Vortec makes a couple of T-Rex pumps. I like the bigger one of the two. The best place for them is just behind the fuel filter. There is plenty of room there.

A few of our cars tried them and they worked well, but they soon ran into the next bottleneck, which is the ID of the hard fuel line going into the fuel rails.

So in a nutshell, the concept works well, but you will also have to address your fuel lines. FWIW, I eventually got tired of running into one bottleneck after another so I just scrapped the entire fuel system and built one from scratch. The last fuel system my car will ever need.

My blower seems to move some air and I want to be sure I can move plenty of fuel to keep up. The last time at the track, I had my boost a pump turned all the way up and when pushing 20psi, I ran out of fuel at the end of 2nd and 3rd gear was full of O2's of .840
Didn't somebody warn you about that? ;)

John
 

·
Registered
Joined
·
106 Posts
Discussion Starter · #4 ·
Didn't somebody warn you about that?
haha, no, that was the last time I ran.. same scan you saw. I have since added an in tank Walbro, 65# injectors, and a new PCM but I wanted to look at a long term solution like you are talking about. (meanwhile, I've put on a bigger pulley to be safe.) My thought was that with this dual pump rewire kit, I would keep the in-tank Walbro, then pull the tank and braze a bulkhead fitting to the bottom. From there, run a 1/2" line to an inline pump, and then up to thicker fuel rails. The stock line would "T" into that. As and added benefit, I would put in a valve in the rear to allow me to drain fuel from the tank at the track so I don't have to play the cat and mouse game with the gas station on the way.

I would have thought the pumps would have run in parallel, not series. So this Caspers wire kit is what runs them in series?
 

·
Registered
Joined
·
346 Posts
Actually, the Casper's kit doesn't care if they're parallel or in series. It simply supplies power to the in-tank pump and "another" external pump. The plumbing will determine if they're in parallel or series and just how much gain you'll see.

Instead of using a T, try to use a Y for better flow and less restriction. Also try and consider failure modes. For example, what happens if one pump fails while the other one is running? Will it starve the car of fuel completely and have it die (safer on the track, possibly less safe on the street), or will it deliver less fuel (dangerous for the motor at WOT, but safer on the street)?

If you're going to run 1/2" line to an external pump, why not make it a GOOD one and forget about the in-tank Walbro altogether? The downside is that good fuel pumps are not cheap.

Sorry man, I'm not trying to sway you one way or another. I'm just giving you things to think about so you can make an informed decision.

John
 

·
Registered
Joined
·
106 Posts
Discussion Starter · #6 ·
johnt said:
Actually, the Casper's kit doesn't care if they're parallel or in series. It simply supplies power to the in-tank pump and "another" external pump. The plumbing will determine if they're in parallel or series and just how much gain you'll see.

Instead of using a T, try to use a Y for better flow and less restriction. Also try and consider failure modes. For example, what happens if one pump fails while the other one is running? Will it starve the car of fuel completely and have it die (safer on the track, possibly less safe on the street), or will it deliver less fuel (dangerous for the motor at WOT, but safer on the street)?

If you're going to run 1/2" line to an external pump, why not make it a GOOD one and forget about the in-tank Walbro altogether? The downside is that good fuel pumps are not cheap.

Sorry man, I'm not trying to sway you one way or another. I'm just giving you things to think about so you can make an informed decision.

John
Ok, I see what you mean., when I here parallel and series, I'm thinking in terms of electronics while you were talking plumbing. Likewise, I was thinking it would be less restrictive to run them in parallel but may be you are right in terms of just excluding the in-tank pump. Ah heck, maybe I should just buy a Scion? :D
 

·
Registered
Joined
·
346 Posts
Sorry, I didn't mean to be vague. Electrically, both pumps MUST be wired in parallel so that each gets the full 13.5 - 14 volts at WOT. The Casper's kit is set up that way. As far as the fuel lines are concerned (the plumbing), that's when you run into options and trade-offs depending on how you want to go about it. You can always call me if you have questions.

John
 

·
Registered
Joined
·
106 Posts
Discussion Starter · #8 ·
johnt said:
Sorry, I didn't mean to be vague. Electrically, both pumps MUST be wired in parallel so that each gets the full 13.5 - 14 volts at WOT. The Casper's kit is set up that way. As far as the fuel lines are concerned (the plumbing), that's when you run into options and trade-offs depending on how you want to go about it. You can always call me if you have questions.

John
When I have a little more cash to play with, I will take you up on the phone call.
 
1 - 8 of 8 Posts
Top