Thanks for looking.. I'd be interested in see what their Flow Rate vs KPA table looks like however. Is it a straight line, or does it retain a slope in the IFR modeling?

I do it this way... (Basically from the tutorial on HPT I linked previously)

Depending on your fuel pressure, 80's are rated to flow...

Static Flow Rate: 80 lb/hr at 43.5 psi
Static Flow Rate: 92.38lb/hr at 58 psi

Soo, if you need the higher pressure and flow for E85, I've seen a 58psi base pressure, if not I'd use 43.5psi. You could probably use any other value, and use the HPT built-in fuel injector calc, but that wouldn't be perfect unless you had the injectors flowbenched. My car ran great at 58psi with these setting for the whole day it was running before. I am on pump gas however, so I don't need nearly that much pressure, so I'm likely going to run at 43.5psi.

For 43.5psi, the Flow Rate Modifier vs Volts is 2 and Flow Rate vs KPA is 40 for 80lb/hr total. For 58psi, I used Flow Rate Modifier vs Volts as 2 and IFR of 46.19016 to get the 92.38lb/hr flow.

Follow the lead from the 60's return style tuning tutorial posted about to see how to setup the the Offset vs Volts vs VAC table using the proper pressure offset. You need to adjust the table for the offset of the base pressure from the stock 58psi pressure. For example subtract the stock base from the new base and convert to KPA. Then find the corresponding KPA column value and copy that across the entire table. For the 58psi you copy the -1 column and 43.5psi uses the -101 column if I remember correctly.

Can anyone add anything..?

 

Pressure gauge probably isn't needed but it's nice to use for trouble shooting. It will not help at all for PCM programming. The idea that you can calculate things out by pressure and just program it all in is incorrect. Doesn't work out like that.

AFter going boost referenced as option 2 (recommended), you want to basically keep a similar fuel chart to what you had but flatten the line. In our experience, not toally flat. Just take that slope if it's going from 40-60 over the chart and cut it to 50-60 or something like that.

Of course you should adjust the voltage for larger injectors too since the chart doesn't go far enough to do it all in the injector chart but this is stuff ZZP isn't offering support on. Buy our PCM if you want us doing it. Some people don't use the voltage modifier for 60+ # injectors and for them we'd have to figure out their file to get advice, esp if they changed the MAF. This is why we tend to keep the advice basic. It's not fair to ZZP to expect us to rework your PCM when you aren't buying the file from us. If someone bought our file, our BRFP, then we would help. it would be easy for us because we'd already understand the file and have base files to start from.

 

If setting your fuel pressure to a certain setting and inputting those parameters into the tune works for a return style setup, how does it not work for the BRFPS setup when the kit does the same functionality?

When I had my car working at 58psi, I tuned mine with a flat IFR, and my fuel trims were right inline, only a couple % off at most, and the car idled and drove very smooth.

Can anyone else share some tuning advice for this setup? Does it get tuned as a return style system, or do you have to maintain a sloped injector flow rate table as ZZP suggests?

 

You simply got lucky if that's how it panned out.

 

I clearly stated earlier in this thread that you need to flatten out the injector flow chart.

You've said three times since then that you don't understand why we wouldn't flatten out the chart.

 

You may have said it, however Zooomer in his previous posts just said that a sloped injector table is used.

It would be impossible to model the injector flow rating without knowing the fuel pressure. The flat IFR table is the best solution. I've asked around on the HP Tuners forum and that is what I've got. I'm not discrediting your method of tuning the system, I am simply asking for information and verification on what you do. If in fact the method you are describing is correct/proper/better/etc, then I would please kindly ask you to share with the Cobalt community this method so that we may better and more effectively use the product.

 

Let me clarify my statement about the gauge.

Yes, you change the PCM because you are referencing the fuel pressure to manifold pressure.

No, you can't do math on a piece of paper and expect your car to be exactly dialed in. There are too many variables. You will never know the exact flow rate of your injectors, you will never know the exact fuel pressure, regulators very rarely work exactly 1:1 with boost/vac, flow or the pump changes at different pressures which affects pressure based on how a regulator works. (flow to the injector isn't related to flow of the pump in that statement).

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In the cobalt with 60psi stock the actual injector flow rate changes as manifold pressure change because it works on pressure differntial so if you have 10 psi of boost, it's really only 50psi of fuel pressure.

The idea of boost referencing or return style or whatever you call it, is to change the fuel pressure along with manifold pressure. I believe it's -1 psi for each 2hg of vac (guessing, can't remember) and 1psi per 1psi of boost. That way the injector always sees the same pressure differential and PCM wise you can have a flat injector chart.

The problem comes in when you apply this with a restrictive type pressure regulator. It doesn't work 1:1 exactly and so you end up either skewing the MAF chart or leaving some angle in the injector flow table to have thing work properly in real world tuning. Of course the amount of skew in the table can vary but the idea is to take some very sloped and flatten it out. Mabye it's 5 different from one side to the other. IDK. Once the car is idling and dyno tested or wideband checked you can see how close it is.

 

Thanks for the clarification. I was simply asking for some others to share their tuning of the kit since ZZP does not want to specifically share their tune, which is understandable due to all of the variables involved.

 

Chris' car didn't have full boost reference. It was setup to maintain 60psi until you surpass 17psi. Then the fuel pressure would rise once the boost is too high for the injector chart.

 

Hmmm interesting...i thought you guys initially had said (idk who specifically, just 'ZZP' in general) that Chris's car had a return style fuel system installed when you guys put on the twincharge, im pretty sure i read this in twincharge thread and i believe he told me the same thing...but we know it didnt so i assumed that was referring to the BRFPS...

Regardless, I guess if the BRFPS accomplishes alot of, if not all, the same things the return style does, it does save some cash

 

LSJs already have a return style fuel system. The factory just sets it up to return right after the fuel filter. Our boost reference system also returns at this point. We just add a boost referenced regulator. Returning from the front of the car doesn't add any advantages unless you prefer to have your regulator there for access reasons.

 

so is that option 1 then?

 

if you are using a base pressure of 58 wouldn't the kit be doing the same as the option 1? Or am I way off here?

 

Yes.

No, because having a 58psi base would still mean that the fuel pressure drops to around 50 at idle using option 2.

 

so the option 2 continuously raises or lowers pressure depending on boost where as the option 1 only changes past 17.5 psi?

 

Yessir.

Opt 2 controls fuel pressure entirely, raising and lowering it based on engine demand. I'm running a 43.5psi base pressure now, and with idle vacuum the pressure dips into the 35 range, making the 80's idle sooooo good at 750rpm.

Opt 1 retains the stock regulator, so your fuel pressure stays at 58psi until the boost raises enough to kick the ZZP regulator above 58psi, hence raising the fuel pressure and providing more fuel.

I'm not sure where the 17.5psi comes from though? I think it's supposed to be stock base around 60psi - 17.5ps = about 42psi, which is what they say the regulators come set at. There will definitely be some variance there, but it shouldn't matter since it's only raising the pressure.

 

The stock PCM is sort of a BRFPS but only setup to maintain 58psi. But it only increases FP up to 17.5psiof boost. After that, it does not adjust the FP based off of boost. That is where option 1 of the ZZP BRFPS steps in. It adds one psi of FP for every psi of boost past 17.5.

Check out your Injector Flow Rate vs Kpa Vacuum table. -120 kpa vacuum equals 17.5psi of boost.

 

You said two conflicting things. Maintain and increase are different. The stock system does maintain ~58psi. It cannot fluctuate the FP because it is literally a ball, o'ring, and a bent metal arm spring that restricts fuel flow (to roughly 58psi).

I know the table max is 17.5 in KPA in the PCM. That wasn't what I was saying. What I was saying was that if ZZP's system is supposed to add fuel pressure at exactly 17.5psi, it would need to be perfect calibrated to 40.5psi as 58-17.5=40.5psi. This isn't the case, and it doesn't actually matter, as so long as it adds the proper amount of fuel around 17.5psi, it all runs the same. I spoke with Ryan from ZZP who designed the kit, and it is 'supposed' to be ran as option 2 anyways. Dropping the tank isn't too hard, so it's benefical to just do it right one. Or in my case have problems for a week lol.

The PCM has the values for different engine airloads so that it can accurately model the injectors at different values. Injectors will flow differently and have different dwell time, etc, in different conditions. This explains the slope in the stock system, and a flat rate in a 'return style tune' (boost referenced regulator adjusts injector 'sizing' by varying FP).

Just wanted to clarify for the people reading.

 

You mean boost/vacuum? That is what I am saying.

If you were running the stock fuel system and flatten that table it would effect your fueling.

 

Yes, basically the MAP values the engine see, vacuum/boost. And yes, modifying that table would effect the fueling.

I would love to hear some feedback from someone who has this option 2 setup tuned as a 'return style system' to compare info on.

 

bump

 

What's to know?

I have mine running as option 2 and I have my car tuned for a 1:1 regulator just like you would a full return setup.

I'm sure it's not exactly 1:1 and there is probably a slight slope like Matt said, but until I get a Fuel Pressure Gauge in the car and log it with HPT, I have no way of knowing the slope and pressure to tune around.

My car runs fine with the way it is setup now, though.

 

Glad to hear it's running good Wes.

Mine finally is as well. 43.5psi base pressure, ~36psi at idle, should be ~66 or so under full boost, which is more than enough for pump 93. Car idles great now! I just need to get my tune dialed in fully.

I was just bumping for more information. There isn't much info out there on this kit, and maybe more people would try it out if they understood it better?

 

Does someone has or can post pictures of this fuelab brfps? Please I need help bad with this install

 

Did You installed it? I need help too