JMS Voltage booster on Blown car
 

I am going through tuning the car and when we started the BAP was not functioning correctly. I was able to get things figured out and got a test run in and, wow, what a difference.

Watching the fuel pressure (low side) prior to the BAP working I saw the pressure start in the 60’s and drop to about 43psi at redline (55% E on a 4th gear WOT pull). - HP Tuners

After getting the pump to work correctly I repeated the test and the fuel pressure jumped to 70psi and stayed there the entire run. It was a thing of beauty.

It does bring up a concern, however. How would I know if my BAP quits working? In theory I might see my AFR gauge indicate there is a problem. But at WOT there is no chance I can take a look at the gauge since I am holding on tight and watching the road. Maybe it will get easier when I have tires that won’t let the car spin at 70mph. :eyebulge:

I’m glad I installed one of these as well. As far as knowing if it stops working, I suppose the only way would be a fuel pressure gauge inside the car. Unless there’s some way to rig up an alarm of fuel pressure drops below X PSI, which I’m sure is possible but not sure of the expense. Gauge setup would be fairly cheap though.

Did you command higher voltage in HpTuners - FSCM? I did that and it holds 70+ to 6k then 65psi no problem to redline without BAP. OP, did you have the fuel drop only with E85 or 93 also?

I would have to go back and look, but I am sure it’s a function of adding a bunch more power and the fuel requirements for e85.

I do know that when I was on the dyno with the blower, LT1 fuel system we advanced timing enough to see a difference in what was demanded and what was supplied. With the stock system, that was at 575whp (in 5th...which likely means we are looking at 600whp).

Now that being said, in your setup without the BAP, you might have seen the right power one time and then the next time you won’t because of the variable power setup. The advantage of the BAP, is it guarantees your FP will always have the same voltage.

I think the easier thing would simply be to watch afr. Figure with the BAP, we have more fuel and can run more timing. That would mean that there is a risk of leaning out. If my afr gauge would retain the peak value then it would be easy...but it doesn’t.

all this concerns me also, it would be nice and maybe HP tuner can already do it? To have a red led turn on and stay on under either of these two conditions: 1 low pressure on the lp side while under performance load, 2) lean condition detected under performance load. With said LED warning the tune should actually back off timing and throttle.

The Aeroforce Interceptor has an Annunciator feature that you probably can setup to flash if the Rail pressure drops below a certain threshold. I currently use my Annunciator as a shift light but if you have the A8 or don't need the shift light you'd be all set.

On mine, I have it set for voltage all the time at 12.5v vs 11.2(factory), boost voltage at 14.6v vs 14.0, and then 10min vs 1min for the duration. I had it at 14.8v but that would peak at 15.2v with upper 70psi and over 80psi when the vehicle would shift. This also got rid of the lower voltage reading in the vehicle which really annoyed me.

I noticed the fuel pump max request is 15.5v (ZL1 program 15.5v from 190-508 fuel flow rate vs 14.7 on LT1) from the vehicle, but the car could never give it with the factory settings. Then doing WOT pulls, you're correct that it would have pressure and then die off or not be there the next time. This was due to the 1min of boost voltage increase only and the low 11.2v starting voltage. I do have LT4 fuel system which I don't think makes a difference in the voltage programming and what I found to fix my inconsistency issue.My assumption is LT4 stuff just flows more fuel than LT1. It's the same every time now, so I'm just putting it out there for guys that might be having the issue also and not actually need more fuel that the system cannot deliver. I'll be doing E85 when I get some time, so I'll see how it goes then with fuel supply :thumbup:

HpTuners does have a minimum fuel pressure psi setting, so if it drops below the setting it will warn you - check engine light/protect mode, something I'm sure. Didn't look that far into it, but maybe someone knows what it will actually do.

What timing numbers were you at?

Good questions...but unfortunately, I really don't know. That would be a question for Ted if he wants to jump in. I would assume the number is probably different based on configs for each car?

We obtained access to the FSCM with HPtuners not too long ago, so maybe the voltage booster was the answer until recently...even at that it might be one of those left in the dark topics since not a lot of techincal info gets shared around here.

Well, if you can dial the voltage up, that’s great, but when I went through and set the voltage booster, it is set to kick in at half throttle and push the voltage to 17.xx. It sounds like with the stock system you can take it to 15? If so, that’s still short of what the voltage booster does, right?

I'm not 100% sure. I do know lingenfelter sets the BAP's to 15.2volts max when they use them.

Thanks for the info. It will do 15.5v all day long, so a little shy of the 17v. I bet we can up that some and be fine. To what amount :noidea:

I think the BAP actually does closer to 17.5.

I just did a little test and with e60 and the BAP turned off, the fuel pressure started falling. I didn’t mess with the tables after that, just turned the BAP back on and pressure was back. I didn’t want to experiment too much on WOT runs...I will let you do that. :sm0:

I think the problem is that e requires so much more fuel...E does provide the equivalent of 105 octane...but you simply have to push more fuel. My guess is that you are gonna run into problems with e...but then again, if bumping the minimum to 17.5v works...maybe not.

The other issue might be that we run out of fuel anyway. At some point the injectors simply don’t have a large enough window to add fuel, right? I guess my point is, you might be able to tweak the tuning to adjust with stock parts, but the BAP makes it so easy and the impact was so clear.

For me, BAP is the way to go. That being said, I went forged pistons and will likely take a winter project to add rods and main studs. I do prefer to over build sometimes. Looking forward to your findings. :respekt: