Not sure if this is the right forum to post this. If not, please move it.

I'm currently running 2 staged Walbro 450s on my twin turbo V8 Toyota truck (1045whp @ 25-26 psi) with 1300cc ID injectors. The pumps join together outside of the fuel pump assembly from -6s to a single -10 line. One pump is on all the time and the other is staged to come above 2800 RPM and/or 4 psi.

This setup held fine at 25 psi and E85 last season. After fixing some boost leaks here and there and running E99, my truck is now pushing 30psi using the same exact tune (it scales with more ethanol and reduces WG duty cycle along with it).

I did 3 passes and in all 3 it went into limp mode in 1st gear (1st pass) and 2nd gear (later passes) due to it being lean. Checked the logs and the differential pressure before and after the injectors was reduced from 48 to 37 psi from last season causing IDC to rise to 110-115%.

I had a similar issue last season where IDC was that high but it went down to 90% after increasing base regulator pressure from 40 psi to 43 psi. This time even though it became a bit better at 50 psi it still wasn't enough to make it not lean at high boost.

To fix this I thought I should just get more pump so I ordered two new Walbro 525 (hellcat) pumps to replace the 450s. But looking online they only flow 8% more (16% combined) and I'm not sure that's enough.

So what I'm planning to do is to keep the 450s and stage the new 525 pumps to come on with boost. The two pumps will be joined inside the fuel pump assembly so two pumps will share the same -6 line.

My question is, would I run into issues running all 4 pumps in parallel using two -6 lines into one single -10 line being they all have different flow rates? I know I won't be getting their maximum potential but I'm just looking for a little more fuel delivery/pressure to hold it steady at 30 psi of boost.

Wiring wise, I'm gonna use 4 40 amp relays that use the signal from the previous 450s signals (constant and staged).

 

If your looking to increase pressure you can put a pair of pumps in series. You wont increase flow volume this way but you will be able to run higher pressures at the current volume. I am not sure how this works with mismatched pumps though.

 

You're correct. I've been going through pump calculation theories and pumps in series increase pressure while parallel increase flow volume.

I decided to do this properly after discussing with a friend who can get me an fittings for cents on the dollar. Going to run four -6 an lines from the pumps into two -10 lines that are bridged before the regulator using -10 also and then feeding the rails using -10 fittings. After the rails I'm going to keep it the same with -6 everything. If this won't do it, I don't know what will.

 

I don't understand how you will more than double the volume, but keep the same -6 return line. Seems it would need to double as well

 

I'm not looking to double the volume tbh but I will definitely have an increase going from 2 to 4 pumps.

The way I understood this is, a return is just the minimum pressure you can set the regulator at. So if I turn on all pumps and my pressure is 70 psi and my regulator couldn't drop it anymore even if it is all the way loose then it's due to the -6 line (unless the regulator's return outlet is smaller).

When you're going WOT and your injectors are at +90% duty cycle, it doesn't really care what happens after the fuel rails as the flow lines before it are sufficient enough to supply that demand.

I myself doubt what I wrote is correct, so please correct me if I'm wrong. That's why I joined this forum

 

While i can't argue with your results, as they obviously kick ass, but this whole scheme seams wildly rube goldberg to me.
with 1300cc a minute injectors, eight of these flow roughly 600 liters per hour static open at 43PSI.
A single properly sized pump in my opinion would be alot more forgiving if you ever ran into any issues and had to diagnose a problem.
Or if hell bent on multiple pumps why not just rock a boost operated KB boost a pump? They have been proven reliable, especially with these factory pumps, are affordable, and require ZERO fuel system mods or fittings?

Because the pumps are staged, and by the time the extra set come on the engine is useing enough fuel to not need more then the -6 return line can handle at any pressure drop less then the regulator pressure.
In fact what he is describing means this engine does not actually need a return line once the pressure starts to drop as the regulator is fully closed.

 

Are there any single pumps than can flow 300-400 GPH (1100-1500 LPH)? This setup should theoretically flow +480 GPH (+1800 LPH). If it does, I won't need to worry about the fuel system ever again even if one of those pumps fail. My platform can't support a mechanical pump using the belt without spending thousands on fabrication. Inline fuel pumps as we discussed only add pressure not volume, not to mention they're loud. This is my daily driver after all.

I totally forgot about the boost-a-pump. But I've heard mixed reviews and I don't want to waste time messing around with it for a minor increase in performance. Having a bit of head room with 4 pumps gives some peace of mind as well, besides I already have them ordered and they should be here in a few days I'll provide results once I have everything installed and running.

 

You will gain volume with pumps in a series at equal pressures. Each pump will be sharing the pressure demand, and each will flow more at the lower delivery pressures. Its not a huge gain, but definitely a gain.

 

How much power do you think it makes at 30psi? Why do you wish to switch to E99? There is literally like .1 octane difference between e85 and E99. And about the same between E50 and E85. Really no reason to run E99 IMO.

Grab some barrel fuel E85 and hit the 2 pumps with a 18v if necessary. Should be more than enough. 4 pumps is needless overkill IMO.

 

How does this work? The first pump in the series can only push its rated volume. Is it because the first pump effectively runs at a lower pressure?

 

Yes, if you look at a volume VS pressure chart you'll se at lesser pressure the volume rises.

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But you're just barely out of pump right, so you want to increase your capacity by 120%???

 

I get where both of you are coming from. This is definitely over kill but from my perspective, it's worth it. Here were my options:

1. Simply replace the 450s with the 525s and gain 16% more flow and hope it's enough. Cost: Less than $300 for both pumps shipped.
2. Create a 3 or 4 pump setup that will insure I have sufficient flow no matter what. Cost: $300 for 2 new pumps and $200-300 new lines and fittings with a couple of relays and wiring. Total $600
3. Upgrade injectors to 1700cc or 2000cc. Cost: +$1800-2000.
4. Get a +200 GPH inline pump that will add more pressure and some flow. Cost: $500 Shipped + $100 for fittings/wiring + loud noise on a daily truck. $600. The inline pump can be staged so the noise isn't an issue tbh.

This is not factoring that I have already ordered the pump. But since I did, only option 1 & 2 make sense now. For only $300 more to go from 16% to 120% more flow, it's worth it for me to go with option 2.

Over here we have a test and tune every two weeks between November and April. That's only 12 test and tunes max without any cancellations due to weather, championships or holidays. The entrance fee is about $100 for just a test and tune and you can only run 5-6 times max because it's the only track in the region and everyone and their mom is here. I want to reduce chances of any issues as much as possible to make at least a full pass and dial it in.

Regarding boost and ethanol, I ran E99 from an industrial facility because it's half the price of E85 (by ignite) where I'm at ($360 vs $680 for a barrel respectively). at 30 psi I'm probably making 100-150hp more than at 25 psi, so 1150-1200whp. That's roughly 1400hp at the crank. I was going through my logs from last season and my IDC was hitting 99-100% at max boost. I'm pretty sure injectors shouldn't be pushed beyond 80% and even if they do, definitely not above 90%.

 

I wouldn't like the greater opportunity for pump, or system failure. 4 pumps, 4 relays...just more stuff to fail, and wreck your day. Plus, with dc where its at, blending your 99 with some decent gas makes the most sense to me. Just my 2 cents.

 

Same thing could be said about my current setup with two pumps, but with 4 I'll be fine even if one failed. Regardless, that's why I have limp mode enabled. To save my ass when all goes wrong.

 

Yeah, but with double the chances of failure.. It sounds like you have it all figured out.

 

This is the route i'd go. I personally can't imagine a situation that 4 pumps in some parallel setup is the best way to do this. If I were really concerned even with those pumps, then i'd be increasing line size pre-pump or looking into a large aftermarket pump or even a belt driven pump. Like everyone else, the thought of a 4 pump system gives me heartburn. Working at an OE auto mfg, We do like redundant systems, but this is a bit overkill and treads into the failure prone realm.

 

Something Aeromotive mentions about their in tank pumps is that ultimately you can wind up with issues in terms of sump capacity having multiple pumps.

 

I still vote BAP. KB tested a Demon pump at 21 volts where it flowed over a thousand LPH at 60psi. That means 2000 lph for both pumps if you whent demon pumps. The hellcat pumps, which are 340's flowed 730 lph at 60 pounds. You basically double the amount of flow you have currenty at 21Volts. Only when in boost, for around 300 bucks, without even smelling any gasoline. I've probably installed a hundred of these things, on everything from cyclones, grand nationals, cobra mustangs, lightnings, gt500's, ect, and not had one single problem with any of them.

 

Thanks for the input guys. I ended up not having much time before track day and just settled for upgrading the pumps from 450s to 525s and kept the fuel lines the same. However, I also lowered ethanol content to about 78-80% (I used E99 before but ECU only reads 91%). Turns out my Flex fuel sensor can't register ethanol more than 91%. With the new pumps and lower ethanol content my AFR was actually a bit rich and I have a lot of head room left. It's a good thing I listened to everyone's advice instead of wasting time and money on a 4 pump setup.