Need help understanding Mazdaspeed HPFP problem

VersaTuner for Mazdaspeed6, Mazda 6 MPS, Mazdaspeed3, Mazda 3 MPS, CX7
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suchamoneypit
Posts: 18
Joined: November 26th, 2019, 5:03 pm
Location: New Hampshire

Need help understanding Mazdaspeed HPFP problem

Post by suchamoneypit »

So I know the stock HPFP is famous for not being able to maintain pressure at high load, as seen in this picture:

Image


The stock internals tend to drop down below the 1600psi stock. I see on most of the provided tunes, 1799 is requested. What makes the pump fail? Is this something that just breaks and happens mid-WOT without you knowing and thats the problem? Will a bad pump always be bad, and it can be seen in the logs? Im not sure if my car has HPFP internals, but I think it might, based on its mods (bought car at auction). I believe before the car was tuned, it peaked at pressures 2100psi+ (I cant remember when, but it definitely hit those numbers on logs, i think maybe when I was using the free log only version of VT). On these tunes, I haven't messed with fuel pressure, but my car always maintains the pressure right around the requested 1799 PSI.

Do this mean my HPFP is upgraded? Does this mean I could just have a non-faulty OEM? If my OEM one is working fine, is the problem that it could without warning stop maintaining the requested pressure? Is it safe for me to increase pressures (what happens on the OEM?)? Using Versatuner and logs, is it possible to confirm if I have HPFP or is physical disassembly absolutely the only way?

Worth noting my friend who definitely has stock HPFP, his pump maintained the 1600 psi solid during WOT. Is he good then? Is his liable to fail at some point? Everyone always says "dont tune without HPFP", but never explain on a deeper 'tuning' level explanation of what this is.
2011 Mazdaspeed3
Street Unit TMIC - Cobb SRI - Cobb Catback - Corksport BPV - HPFP - Cobb RMM - Rear seat/sub/spare tire delete - Rays Mazdaspeed Forged Alu. Wheels - 1 mazdaspeed sticker (+10hp)
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Need help understanding Mazdaspeed HPFP problem

Post by mituc »

Upgrade the HPFP internals. Don't even wait.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Polish_Eagle
Posts: 21
Joined: December 3rd, 2014, 2:33 am

Re: Need help understanding Mazdaspeed HPFP problem

Post by Polish_Eagle »

There's nothing to understand. The factory fuel pump was designed for specific amount of fuel flow and adding mods exceeds its design.

Just upgrade the pump and move on in your life. Or, don't upgrade and then we'll see you in a few months asking why the motor is blown.
suchamoneypit
Posts: 18
Joined: November 26th, 2019, 5:03 pm
Location: New Hampshire

Re: Need help understanding Mazdaspeed HPFP problem

Post by suchamoneypit »

mituc wrote:Upgrade the HPFP internals. Don't even wait.
Polish_Eagle wrote:There's nothing to understand. The factory fuel pump was designed for specific amount of fuel flow and adding mods exceeds its design.

Just upgrade the pump and move on in your life. Or, don't upgrade and then we'll see you in a few months asking why the motor is blown.
Thats not the question im asking. Its not about me exceeding fuel flow by tuning. Its about if the pump fails spontaneously, or if it is just known to not be able to provide the requested fuel. I might already have HPFP. I'm asking if there is a way to verify if I do by using logs. I'm looking to learn about why this part fails and if there is a way to use versatuner to confirm if you have stock or upgraded internals. I'm well aware if my pump doesn't deliver the fuel it needs it goes boom.
2011 Mazdaspeed3
Street Unit TMIC - Cobb SRI - Cobb Catback - Corksport BPV - HPFP - Cobb RMM - Rear seat/sub/spare tire delete - Rays Mazdaspeed Forged Alu. Wheels - 1 mazdaspeed sticker (+10hp)
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Need help understanding Mazdaspeed HPFP problem

Post by mituc »

So a few things, including the answer to the question you're asking (which was partially answered).

1. Stop commanding 1800PSI of fuel pressure. Tell the guy who made you that tune to stop using that approach because it is wrong. There is no measurable advantage over commanding 1700-1750. the pressure relief valve starts cracking open at about that fuel pressure (maybe a tad earlier) and it's fully open at 1850PSI, meaning it bleeds out fuel from the fuel rail meaning the HPFP will work for nothing (or will work to recirculate).

2. These pumps are moved by the intake cam lobe, meaning that the number of pumping cycles per minute is dependent on the engine speed. Because the HPFP piston moves fuel by displacing volume inside the pump it means that the fuel flow is dependent on the engine speed, assuming you have no recirculation or regulation in place (which they are kind of shut down when demanding full power). This means that the HPFP will be able to move about 50% more fuel in the same amount of time (say, per second)) at 6000rpm compared to 4000rpm. Also, for the same injector duty cycle, the injector pulse width at 6000rpm will be 2/3 of the injector pulse width at 4000rpm, Let's assume that the engine takes in the same amount air in a time unit (say, per second) from 4000 to 6000rpm (which is common and pretty much the case for stock turbo cars with no bolt ons or just a few, where we see like 230-240g/s of air at 4000-4500rpm and 250-260g/s of air at 6000), and for simplicity let's assume the same commanded AFR because the variation is under 10% anyway. So this means that the amount of fuel that needs to be pumped into the cylinders is about the same at 4000 and at 6000rpm, just that at 6000rpm there is an excess of fuel of 50% compared to 4000 where the injectors have to stay open for longer and drain the rail of fuel.
So this is how HPFP fuel starvation occurs in the mid range where we shoot for high boost and torque. And this is why you need to upgrade the HPFP as told in many occasions here instead of re-studying the same things we did back in 2008-2009 when probably 30% of the tuned Mazdaspeeds and MPSes over the world blew with shitty OTS tunes, EcuTek tunes and Piassini/Dimsport tunes which never paid attention to what the fuel pump can do but were promising 475Nm or torque at 3000 (fuck!!!) rpm and 300-305bhp at 5500 (well, poor factory turbo!). Later they got wiser and were promising only 450Nm of torque and 290bhp, and they were still blowing (actually EcuTek tunes still damage MPSes even these days for those silly and lazy enough not to get VT, AP or at least Mazdaedit.

3. gen2s (like yours) are a bit more sensitive to fuel pressure variations because I think the spill valve is commanded differently by the ECU (which is also different than the gen1s, 6MPS/MS6 and CX7 gen1) to make them more emissions friendly. 1600psi instead of 1700 is not a problem. 1500psi is already a sign. From 1300 down you can grenade the engine pretty much at any time.

4. To be safe stay below 1.9-1.92 commanded load anywhere between 3000 and 5000rpm. Ideally don't go higher than 1.9, but the truth is that the load a car can take depends on a lot of factors: contamination, injector efficiency, fuel quality, tuning (AFR, timing), and so on. I've seen cars doing fine at load 2 with factory pump internals, and I've seen some almost spitting their guts out at 1.85 after TC/DSC/ESP was triggered and ECU decided to enrich the mixture down to high 9s.

So stop running shitty tunes commanding fuel pressures close to the PRV full opening and follow the advises you get here. Trying to experiment on your car may cost a bit more than just getting an answer on a forum to a question asked right or on google search after searching for the right things.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
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