[Becker]

You won't see higher pressure because like Matt said it's regulated in the tank. The BAP is there to maintain the 58 psi at the rail,also like Matt said. However , JonW was dead on about the boost knocking back the fuel that actually sprays out of the injector. So even at optimum pressure at the rail you will suffer fuel pressure loss at the injector which makes it more critical your fuel system is working right. You need to make sure the BAP is working right...or better yet a pump thats actually capable of delivering the right pressure without a BAP.

Finally, an explanation that pulls all the different opinions together and makes sense of it all. Thank you.

 

[JBW]

I noticed that there are quite a few people who are more concerned about fuel pressure than AFR, which IMO is the wrong focus. I understand that without sufficient fuel pressure and proper injector size that obtaining optimum AFR is not possible, but some people are installing fuel pressure sensors before installing an O2 wideband sensor.

I understand boosted applications require more fuel and in most cases a BAP or additional fuel pump is warranted, but if my fuel pressure is @ 30psi and my AFR is staying within range, let's say 11.2 - 11.7 for boosted applications, why should I be concerned about my fuel pressure? However, if my fuel pressure is @ 30psi and my AFR is >13.0, then I should concerned about my fuel pressure.

Am I missing something?

 

[Becker]

I noticed that there are quite a few people who are more concerned about fuel pressure than AFR, which IMO is the wrong focus. I understand that without sufficient fuel pressure and proper injector size that obtaining optimum AFR is not possible, but some people are installing fuel pressure sensors before installing an O2 wideband sensor.

I understand boosted applications require more fuel and in most cases a BAP or additional fuel pump is warranted, but if my fuel pressure is @ 30psi and my AFR is staying within range, let's say 11.2 - 11.7 for boosted applications, why should I be concerned about my fuel pressure? However, if my fuel pressure is @ 30psi and my AFR is >13.0, then I should concerned about my fuel pressure.

Am I missing something?

My AFR is just fine and in that 11-11.7 range, but the fuel pressure looked low and I like all the numbers to look good.

 

[Hemi31]

I noticed that there are quite a few people who are more concerned about fuel pressure than AFR, which IMO is the wrong focus. I understand that without sufficient fuel pressure and proper injector size that obtaining optimum AFR is not possible, but some people are installing fuel pressure sensors before installing an O2 wideband sensor.

I understand boosted applications require more fuel and in most cases a BAP or additional fuel pump is warranted, but if my fuel pressure is @ 30psi and my AFR is staying within range, let's say 11.2 - 11.7 for boosted applications, why should I be concerned about my fuel pressure? However, if my fuel pressure is @ 30psi and my AFR is >13.0, then I should concerned about my fuel pressure.

Am I missing something?

to start with fuel pressure and injector scaling is all based off of 58psi. Most S/C kits out there give you injectors based off of 58 psi. Most builds are not overkill enough that a serious drop in pressure can be made up for by telling the injector to flow more fuel. So 90% of the time if you lose fuel pressure you will lose AFR as well. But if you have a gauge on your rail like BigBoy and see 8psi less than you are supposed to have at idle would you even want to ramp up into a WOT situation and hope you catch your AFR gauge fast enough?

 

[JBW]

to start with fuel pressure and injector scaling is all based off of 58psi. Most S/C kits out there give you injectors based off of 58 psi. Most builds are not overkill enough that a serious drop in pressure can be made up for by telling the injector to flow more fuel. So 90% of the time if you lose fuel pressure you will lose AFR as well. But if you have a gauge on your rail like BigBoy and see 8psi less than you are supposed to have at idle would you even want to ramp up into a WOT situation and hope you catch your AFR gauge fast enough?

I was just using extreme examples concerning the fuel pressure, but you bring up a very good point in that you shouldn't solely depend on AFR since there is some "lag" time between what's going on in the cylinders and what's being measured at the wideband sensor. At high rpms it could only take tenths of a second to run into dangerously lean conditions. Thanks.

 

[Becker]

to start with fuel pressure and injector scaling is all based off of 58psi. Most S/C kits out there give you injectors based off of 58 psi. Most builds are not overkill enough that a serious drop in pressure can be made up for by telling the injector to flow more fuel. So 90% of the time if you lose fuel pressure you will lose AFR as well. But if you have a gauge on your rail like BigBoy and see 8psi less than you are supposed to have at idle would you even want to ramp up into a WOT situation and hope you catch your AFR gauge fast enough?

Just to clarify I'm seeing 3-8 psi down on my fuel pressure gauge at WOT. All other driving it's at or a tad above 58 psi.

Edit: Just added a 392 fuel pump, so things might change.

 

[Hemi31]

Yep....if you are losing pressure you are running out of pump. The 392 pump with a BAP will help a little but it's only about 20lph over the 6.1 pump. Honestly spending the money on the Arrington setup will eliminate the BAP altogether and give you all the fuel you will need up to about 750rwhp with that 392 pump you just put in.

 

[HEMI~C~]

No, your BAP is working. Again, the fuel pressure is controlled by the relief valve in the pump assembly. The BAP controls fuel FLOW. The additional flow supplied by the BAP prevents the PRESSURE from falling below 58 psi ( ALTHOUGH YOU CAN SEE A SLIGHT PSI DROP AT THE RAIL AT WOT). The BAP pressure switch activates the BAP only when the engine is in boost.
We have no record of an actual BAP failure in the last 6 years. MILLIONS OF MILES, NO FAILURES. It is used on all KB kits. The concept is now also used by our competition on their kits. It is very reliable. And the BAP on a Dodge will support up to 775RWHP. That's 400HP over stock.
We have our own Dual Pump System designed but +775RWHP applications are rare so the sales picture isn't all that attractive. Also, multiple pump systems are VERY expensive, they heat the fuel, require re-tuning, rewiring and re-plumbing to a return style system. The only application we recommend dual pumps for is the +775RWHP. As the old saying goes "If it ain't broke, don't fix it."

Matt, can I send my 40a - 20v KB BAP off to you guy to have it checked out as it just stopped working on me last week? I had to rewire bypassing it while on the side of the highway to get back home. With that said, it has served me quite well for the last couple years powering two stock pumps and supporting over 1100rwhp.

 

[[email protected]]

Matt, can I send my 40a - 20v KB BAP off to you guy to have it checked out as it just stopped working on me last week? I had to rewire bypassing it while on the side of the highway to get back home. With that said, it has served me quite well for the last couple years powering two stock pumps and supporting over 1100rwhp.

Yeah we can test it for you just PM your name, address and phone number to me and I will give you a RA number to put on the box. We will repair or replace it no charge if there is a issue with it.

 

[[email protected]]

Yep....if you are losing pressure you are running out of pump. The 392 pump with a BAP will help a little but it's only about 20lph over the 6.1 pump. Honestly spending the money on the Arrington setup will eliminate the BAP altogether and give you all the fuel you will need up to about 750rwhp with that 392 pump you just put in.

No matter what pump you have there will be some loss in pressure between the pump which is regulated at 58 psi at the pump end and the fuel rail at WOT because there is always a loss in a
fuel line. To minimize that, install a bigger fuel line, not necessarily a bigger pump, and only when it is required at higher hp levels. It is not unusual on a mechanical return-less system to see as much as 10 psi loss or more at WOT depending on the hp level simply due to the loss in the fuel
line. We have compensated for this in the tune as any good tuner would. It is not necessary to upgrade the stock fuel pump as long as the BAP is being used. It is not the pump that is "giving up". It is the loss in the fuel line you are seeing. Adam at ST Motorsports ran more than one car all the way to 770 rwhp using our 21 volt BAP and stock pump/fuel line. That's just over 900 engine hp. Our company test car does the same and all data is verified on our Fuel Flow Bench.

According to our own flow bench pump "ratings" can be misleading. The stock 392 Dodge pump assembly flows 217LPH at 60 psi and a whopping 401 LPH with the BAP. That's not just a "little" more flow. It's 184L more or 84%!! Now let's take the "big" advertised aftermarket pump ratings and see what the BAP does for flow.

The BAP will increase an Aeromotive 340L to 562L (+182L) or a TI 400L pump from 352L to 568L (+216L).

Almost all manufacturers of late model supercharger kits ( Dodge, Ford and Camaro) use the BAP or a similar concept- and for good reason(s). Why replace the stock pump or assembly with all that labor cost when 99% of the applications are covered by the simple, less costly easy to install and proven BAP? And don't forget another often overlooked disadvantage to running dual 255's full time- HEAT!

Our test indicate dual 255's heat the fuel from 70 degrees to 100 degrees in 30 minutes. Since gasoline boils at 77-90 degrees (depending on octane) "full time" dual pumps is truly the "hot" set up- and why Ford and GM went to return-less pulse width systems. Isn't that why racers use cool cans? And who believes hotter fuel makes more HP?

Finally, do not be mislead into believing that two 255L pumps in a common canister will flow 2 times the rated flow of one 255L. They will NOT. Doubling the rating is not real life. Big misconception.

Example: 255 @ 60 = 257L x 2 = 514
Two 255L's in common hat = 420L or 18% less ( 420 vs 514)

Again, the BAP with the 392 is 401L without the dual heat build up. And this data is not guessed. It was conducted on our Fuel Flow Bench and dyno with company or customer vehicles.

As you can now see, there is more to pump engineering that meets the eye. There is line loss, hat restrictions, flow vs pressure, back pressure, relief valves, calibration etc. Look for a big upcoming informative Dodge Pump Tech Feature in Mopar Action Magazine. There are a lot of considerations in fuel system design other than adding a pump. We hope the info helps.

One of the Kenne Bell flow benches. A stock fuel line system is being tested for flow and pressure loss.
The bench is capable of levels of up to 1400LPH or 2324 lbs of fuel. That will support 4600HP at .5lbs fuel per HP.

 

[Hemi31]

sorry that some of us don't believe in BAP's.

 

[HEMI~C~]

No matter what pump you have there will be some loss in pressure between the pump which is regulated at 58 psi at the pump end and the fuel rail at WOT because there is always a loss in a
fuel line. To minimize that, install a bigger fuel line, not necessarily a bigger pump, and only when it is required at higher hp levels. It is not unusual on a mechanical return-less system to see as much as 10 psi loss or more at WOT depending on the hp level simply due to the loss in the fuel
line. We have compensated for this in the tune as any good tuner would. It is not necessary to upgrade the stock fuel pump as long as the BAP is being used. It is not the pump that is "giving up". It is the loss in the fuel line you are seeing. Adam at ST Motorsports ran more than one car all the way to 770 rwhp using our 21 volt BAP and stock pump/fuel line. That's just over 900 engine hp. Our company test car does the same and all data is verified on our Fuel Flow Bench.

According to our own flow bench pump "ratings" can be misleading. The stock 392 Dodge pump assembly flows 217LPH at 60 psi and a whopping 401 LPH with the BAP. That's not just a "little" more flow. It's 184L more or 84%!! Now let's take the "big" advertised aftermarket pump ratings and see what the BAP does for flow.

The BAP will increase an Aeromotive 340L to 562L (+182L) or a TI 400L pump from 352L to 568L (+216L).

Almost all manufacturers of late model supercharger kits ( Dodge, Ford and Camaro) use the BAP or a similar concept- and for good reason(s). Why replace the stock pump or assembly with all that labor cost when 99% of the applications are covered by the simple, less costly easy to install and proven BAP? And don't forget another often overlooked disadvantage to running dual 255's full time- HEAT!

Our test indicate dual 255's heat the fuel from 70 degrees to 100 degrees in 30 minutes. Since gasoline boils at 77-90 degrees (depending on octane) "full time" dual pumps is truly the "hot" set up- and why Ford and GM went to return-less pulse width systems. Isn't that why racers use cool cans? And who believes hotter fuel makes more HP?

Finally, do not be mislead into believing that two 255L pumps in a common canister will flow 2 times the rated flow of one 255L. They will NOT. Doubling the rating is not real life. Big misconception.

Example: 255 @ 60 = 257L x 2 = 514
Two 255L's in common hat = 420L or 18% less ( 420 vs 514)

Again, the BAP with the 392 is 401L without the dual heat build up. And this data is not guessed. It was conducted on our Fuel Flow Bench and dyno with company or customer vehicles.

As you can now see, there is more to pump engineering that meets the eye. There is line loss, hat restrictions, flow vs pressure, back pressure, relief valves, calibration etc. Look for a big upcoming informative Dodge Pump Tech Feature in Mopar Action Magazine. There are a lot of considerations in fuel system design other than adding a pump. We hope the info helps.

One of the better explanations I have heard. Most folks don't realize how fuel delivery needs to be addressed from end to end not just at the tank and at the injector. IMHO the BAP solution still remains one of the easiest way of getting additional fuel volume out of existing fuel pumps. Right now the choices are either BAP factory basket type solution or switch to multiple fuel pumps with non-sump'd fuel pump inlets on a flat bottom tank. Personally not a huge fan of exposed fuel inlets.

The discussion on pressure loss always peaks my interest because most folks don't realize the factory tuned solution already compensates for an expected amount of pressure loss from the fuel system due to small lines and FPR being in the tank. As long as you have the fuel pump volume to maintain XX pressure and you have enough injector to tune for it the tables are there to compensate for pressure loss. And actually any given fuel pump will flow the most fuel at lower pressures. It is for this very reason we tune with a static 58psi and no boost reference despite 20psi of boost. The two factory pumps I run, w/BAP, initially were barely able to provide enough volume to maintain at 79psi (59psi base + 20psi boost ref) and 900+ rwhp. However once we put the big injectors in and were able to tune for a static 59 psi, compensating for 20psi worth of boost induced pressure loss at the injector we had more than enough fuel volume. Food for thought....

 

[HemiJunky]

Great info! I have the KB Bap being installed and now know how it works. Thanks guys.

 

[gsochallenger]

I have a Fore Hat for sale if anyone needs it

 

[J-Z]

Ill give you $5 and a chicken.

 

[srt8-in-largo]

Bump for a good read.

 

[srt8-in-largo]

Matt, can I send my 40a - 20v KB BAP off to you guy to have it checked out as it just stopped working on me last week? I had to rewire bypassing it while on the side of the highway to get back home. With that said, it has served me quite well for the last couple years powering two stock pumps and supporting over 1100rwhp.

I just sent KB a two year old KB BAP for inspection... and they said it was bad. I feel lucky I did that before installing it.

EDIT: Turns out the BAP was not bad after all.

 

[zippy]

I installed the Arrington dual fuel hat solution as mention earlier. (KB 8psi setup with Adam's tune from ST)
I did take out the KB BAP but,

I am seeing approx 5lb pressure drop at WOT at 8psi boost (at the rail). Is this "normal ?

Could I use the Supplied KB BAP for both pumps? will the extra current draw burn the BAP out ?

Great read everyone. . . .

 

[HEMI~C~]

I drove two factory pumps with the 20a BAP for quite a while before it burnt out. I upgraded the BAP to the 40a dual pump versions since then and saw a noticeable drop in temps in the wiring/BAP itself.

5psi drop when going wot is about normal without the BAP and will not be an issue as long as FP can be consistently maintained and tuned for accordingly. I never saw a drop with the BAP activated.

 

[zippy]

Thanks Hemi-c. I thought so, I just bought a 40A new one from a member for my dual Arrington fuel hat.

I'll wire it it and have no worries

I will come on at 3 psi


Appreciate the feedback

zip