Tuning with a adjustable fuel pressure regulator

[mystickb1996]

So I recently bought a new fuel system and will be installing it this weekend. It consists of a Glenn's sumped tank, magnafuel 750 pump, -10an feed, -8an return, fore f2i regulator, mmr rails, 80s on e85.. I'm tuning with PRP and Iv never tuned for an adjustable fuel regulator. My plan is to set base fuel pressure to 42lbs add 30% fuel across the board from my 93 tune to make up for e85. With the FPR being boost 1:1 referenced what do I need to change in the tune when the car sees boost? If the regulator is adding pressure throughout the pull will I need to take fuel away from the upper rpm range? I'm taking my current 93 tune that was tuned on a stock regulator and will be adding these fuel components. If the regulator is adding fuel as boost rises and the tune is also then won't I need to pull away some from the tune?
thanks for any guys

 

[flyboy1294]

I'm running a very similar setup with my car.

First off, set the fuel pressure with the car off and cold, and the fuel pump running. The fuel pressure gauges are very susceptible to heat soak depending on where you mount them. The fluid inside the gauge heats up and builds some internal pressure, so it shows your fuel pressure as less than it really is. Datalog "Pressure_drop_across_injectors" to verify that you are at your target fuel pressure. This is measuring off your FRPS and is very accurate in my experience.

You should not need to take away any fuel under boost. Your fuel pressure regulator's job is to keep the delta fuel pressure at whatever you set it at with the car off. When the vehicle is off, there is no boost or vacuum being applied to the regulator, so you are setting the true base pressure. When the car is at idle, you will see the fuel pressure drop to roughly 32psi or so because the car is in vacuum. 32psi -(-10psi <-vacuum)=42psi which is what you set it to. Then when you go into boost, the car will add 1psi fuel pressure for every 1psi boost that you make. So if you are making 10lbs of boost, you will have a max fuel pressure of 52psi, but the delta fuel pressure will be 52-10=42. Does that make sense?

You will need to adjust your injector specs to account for the 80s before you do any tuning. If I were you, I would first tune the car on 93 to run with the return fuel system and 80s, just so you were only dealing with a few changes at once. Heck you might even want to start off just tuning for the return fuel system with the 42s, then switch to the 80s and tune for them, then switch to e85. That is what I did with my setup since I am a slow learner.

There are 2 different ways to account fuel e85 needing to run richer. You can do like you said and add fuel across the board and that will give you a starting point. There are a lot of tables you need to add fuel to, though. It is easy to miss one.

There is actually a place in the tune that lets you set your lambda for the fuel, though. For gasoline, yours is probably going to be set to 14.64:1. You can change this to stoich for e85 which is 9.7587:1. This should get all of your AFRs reasonably close. I am going to use this method on my tune. There is just less stuff to screw up, and you won't encounter any surprises this way.

 

[mystickb1996]

Wow nice write UP thanks for the help that what I was looking for. Yes everything your saying makes sense. Glad you explained how to set base fuel pressure because I would have been making the base while running 42 instead of 42 while just the pump is running. The car already has 60s so I'm aware to change the tune for 80s which I plan on doing with sct value files then go from there. Also for adding fuel I will be doing this via the maf transfer function table. The car is a 96 cobra with an 10:1cr aluminator and t trim @ 15-16lbs. Reason for new fuel system is I'm maxing out what the stock rails and lines can handle. Should be around 660-700 on e85 I'm hoping.

 

[flyboy1294]

Wow nice write UP thanks for the help that what I was looking for. Yes everything your saying makes sense. Glad you explained how to set base fuel pressure because I would have been making the base while running 42 instead of 42 while just the pump is running. The car already has 60s so I'm aware to change the tune for 80s which I plan on doing with sct value files then go from there. Also for adding fuel I will be doing this via the maf transfer function table. The car is a 96 cobra with an 10:1cr aluminator and t trim @ 15-16lbs. Reason for new fuel system is I'm maxing out what the stock rails and lines can handle. Should be around 660-700 on e85 I'm hoping.

Glad I could help! The base fuel pressure confuses a lot of people, myself included haha.

Sounds like you have your ducks in a row. I'm sure you know this, but assuming you are running the Siemens Deka 80#, Ford Racing gives really good injector specs for them. Here is a link if you want to compare them to the SCT value files just to make sure everything is cherry. https://fordperformanceracingparts.com/parts/ics/m-9593-lu80.pdf

I have never tuned a car by adding fuel across the board like you are doing, but I would think you will atleast need to go into the base OL fuel table and richen the commanded AFRs by 30% or so across every load range, otherwise your MAF curve is going to need to be tweaked a lot haha.

I'm sure it'll be a beast! I'll be happy if I hit 500rwhp with my auto this year lol.

 

[jblood37]

Ah, Flyboy is here too haha.

 

[ctgreddy]

Agreed with what's said above. When I switched to e85 I changed one thing, stoich value. It got it VERY close. Just had to do some very minor tweaks from there.

 

[cbrown9064]

I wouldn't mess with the MAF transfer, if it is right now, it will be right later. Take a look at this article http://info.efidynotuning.com/fuel101.htm what he is saying is to make sure your wideband and computer match. Once the wideband is showing what the car is commanding. Then change fuel tables to be what you want. To me, changing the MAFx to get the AFR you want (not necessarily what the car is commanding) is a hack job.

Here is a good article on how to tweak the MAFx http://www.rothfam.com/maf/doc-project/tuning_the_maf.html

Once the car is showing the AFR that the computer is calling for, you can start to mess with the fuel tables knowing that the AFR/lambda you put in the table will actually happen.

 

[flyboy1294]

Ah, Flyboy is here too haha.

Where else am I?

I wouldn't mess with the MAF transfer, if it is right now, it will be right later. Take a look at this article http://info.efidynotuning.com/fuel101.htm what he is saying is to make sure your wideband and computer match. Once the wideband is showing what the car is commanding. Then change fuel tables to be what you want. To me, changing the MAFx to get the AFR you want (not necessarily what the car is commanding) is a hack job.

Here is a good article on how to tweak the MAFx http://www.rothfam.com/maf/doc-project/tuning_the_maf.html

Once the car is showing the AFR that the computer is calling for, you can start to mess with the fuel tables knowing that the AFR/lambda you put in the table will actually happen.

I might not have came across clearly in my earlier post, but I agree with you 110%. I was not suggesting he just chop up the MAF curve until it matches what he wants. You do need to tweak the MAF curve with the injector swap or fuel type change though, even if you do change your stoich point in the tune.

The trick is to tune in terms of lambda instead of in terms of AFR. It's dummy proof then and you don't need to change your base fuel tables at all for the new fuel, just make sure the lambse and WBAFR agree while you have open loop forced. For instance, my tune is set for a 1.0 lambda at cruising and most part throttle low load conditions. Then at mid throttle input I switch up and command about .83 lambda after about 3000rpms. Then at WOT, I command .78 lambda because I'm on the stock bottom end and want to be safe for now. I switched over to E last Friday actually, and I was happy with where my fuel tables were set.

Even though my MAF was dialed in very well with the gas tune I was running, when I changed the stoich point to E85 and forced open loop, I noticed it running richer than lambse commanded. I'm guessing this has something to do with the injector slopes not being perfectly linear, so the PCM commanding roughly 30% more fuel all around is actually putting out a bit more than 30%. No biggy though, I just had to tweak the MAF curve to get the WBO2 and lambse to agree again.

I know some guys are able to tune via injector slopes to get the WB and lamdse to agree, and I will be the first one to tell you that is over my head. I've done reading and research on it, and there is more heresay than I am comfortable with. I just put in the manufacturer's injector specs and tweak the MAF to get everything to match up.

 

[txcharlie]

So I recently bought a new fuel system and will be installing it this weekend. It consists of a Glenn's sumped tank, magnafuel 750 pump, -10an feed, -8an return, fore f2i regulator, mmr rails, 80s on e85.. I'm tuning with PRP and Iv never tuned for an adjustable fuel regulator. My plan is to set base fuel pressure to 42lbs add 30% fuel across the board from my 93 tune to make up for e85. With the FPR being boost 1:1 referenced what do I need to change in the tune when the car sees boost? If the regulator is adding pressure throughout the pull will I need to take fuel away from the upper rpm range? I'm taking my current 93 tune that was tuned on a stock regulator and will be adding these fuel components. If the regulator is adding fuel as boost rises and the tune is also then won't I need to pull away some from the tune?
thanks for any guys

What car will this be installed on? If it's a coyote, the setup is different as there is no FRPS. The coyote uses inferred rail pressure. I'm no expert, but everything flyboy stated is spot on according to my research.

 

[txcharlie]

Where else am I?



I might not have came across clearly in my earlier post, but I agree with you 110%. I was not suggesting he just chop up the MAF curve until it matches what he wants. You do need to tweak the MAF curve with the injector swap or fuel type change though, even if you do change your stoich point in the tune.

The trick is to tune in terms of lambda instead of in terms of AFR. It's dummy proof then and you don't need to change your base fuel tables at all for the new fuel, just make sure the lambse and WBAFR agree while you have open loop forced. For instance, my tune is set for a 1.0 lambda at cruising and most part throttle low load conditions. Then at mid throttle input I switch up and command about .83 lambda after about 3000rpms. Then at WOT, I command .78 lambda because I'm on the stock bottom end and want to be safe for now. I switched over to E last Friday actually, and I was happy with where my fuel tables were set.

Even though my MAF was dialed in very well with the gas tune I was running, when I changed the stoich point to E85 and forced open loop, I noticed it running richer than lambse commanded. I'm guessing this has something to do with the injector slopes not being perfectly linear, so the PCM commanding roughly 30% more fuel all around is actually putting out a bit more than 30%. No biggy though, I just had to tweak the MAF curve to get the WBO2 and lambse to agree again.

I know some guys are able to tune via injector slopes to get the WB and lamdse to agree, and I will be the first one to tell you that is over my head. I've done reading and research on it, and there is more heresay than I am comfortable with. I just put in the manufacturer's injector specs and tweak the MAF to get everything to match up.

Someone way smarter than me told me to get the MAF dialed in on 93 and when you switch to e85, the only thing to change for fueling is the stoich. Start with 10 and adjust from there.