How to scale the HPFP pressure sensor

[socks]

It supposedly opens at 1850psi. I cant find the specifications on it in the FSM.

I think its just a safety measure. I may attempt to block it off. I'm hesitant to do that though. If i block it off, I hope that the HPFP relay can control pressure well enough to not obnoxiously ramp the rail pressure.

[SpeedSixxx]

Originally Posted by Lex Is that pressure relief used during normal vehicle operation or is it a safety measure? If it's a safety measure alone and you assume the risk, you can simply block it off. You can also make the feed orifice to it smaller by introducing a washer with a smaller hole between the valve and the rail. This will reduce flow and should maintain higher rail pressure. You can play with hole size until you get it right.

I like to play with the hole..until i get it right.

just FYI DJ, LEX and Socks

I have an 07 spd 6 as well so I assume I should not worry about that.

I do honestly wonder why the spd 3 and 6's have different features when it comes to fuel and fuel pressure seeing how they are the EXACT same motors.

I assume maybe it has something to do with the spd3's safety features with boost in 1st and 2nd gear?....fuel is in a direct relationship to controlling / limiting boost...just an assumption...

again tho...this is why this is true...

MS6>>>MS3 =-)

[socks]

According to Dustin, the relief valve likely has NPT fittings, so its probably a generic pressure relief valve sourced from a vendor. Suppliers might have changed, etc. although, dustin is an 07, and im an 07 and we have different results. Who knows, are speed6 and speed3 produced in the same factory?

Theres a million reasons they could have different values.

[djuosnteisn]

Okay, here's the plug dimensions if you want to go that route (which is probably fine unless your spill valves break and your rail builds up 6000+ psi, lol)

Here's the fuel rail:


Here's the valve:



You can see a round 1/4" disk would work perfect to block both holes. The hole on the rail is concave ish, kinda like dished. So a disk would press nicely in there.

As for why the 6 and 3 are different... well it's obvious to me...

6>>3 lol.

[Lex]

I suggest machining a disc with a hole with 1/2 the diameter of stock.

Then, run the car, but ramp load up very slowly. That way the system can cope if it relies on the pressure relief valve.

The only time to be careful is when letting off the gas after being at high load. The injectors close at the engine being at high RPM produces the most amount of flow. Ease into these situations and watch that rail pressure remains controlled.

[socks]

i wonder if a quick test could be done, clamping the return line to the fuel pump?

[djuosnteisn]

Would the system really rely on this as mechanism for pressure control?

Sean had to scale the pressure half way before he started hitting the clipping, which is like 250ish psi, and kinda agrees on the 1850 ish i remember reading about.



Here is where i read about the 1885psi:


This is a scan from the mazdaspeed6 service manual someone emailed me a long time ago.


Hmmmm. This is from a 6 manual, but the 6 doesn't seem to open???

[Realgib3]

Originally Posted by socks so, on the mazdaspeed3 at least, there is a fuel rail pressure relief. if it goes above 1850 (spec) psi, the valve relieves pressure. but, im able to see that with the dial turned up half way, im reading 1550psi when its relieving pressure, and all the way up, im reading 1420 when it relieves pressure. so you can see that this with the dial all the way up, its scaling voltage enough for 430 or so more psi. If we can somehow raise the relief valves pressure, we can assume that when we're reading 1780-1800psi, we are really getting 2200psi. however, until i can adjust that valve somehow (whether it be a new spring, or hopefully as easy as a shim), im stuck at 1850psi. Dustin is having different results on his car, so the pressure relief may not exist on the speed6, or its at a higher pressure.

Ok, so I have an 08.5... and with my MAF cal done and trims damn close to 0... I was holding 1900+ and spiking well past 2100 with my KMD internals at 11.8:1 AFR... Was I really hitting these pressures??? or was the AP reading wrong??? Just wondering if maybe they changed something with the newer models that allowed for more pressure without relief...

[SpeedSixxx]

send me a copy of that service manual....spd6 right?

[djuosnteisn]

It's not the whole thing, just some random scans some guy sent me. I'll send it to you though for sure. PM me your email.

[Lex]

the relief is not exact so don't expect it to be

[djuosnteisn]

Plus, when running higher pressure, it would be less work for the spill valves, right? Spill valves work most when doing light load at high rpms, trying to maintain like 400psi or something while cruising at 5000rpm.

Do you think there is any difference between the hpfp cam lobes between the two?

[Lex]

I doubt it and it wouldn't matter. Yes, the spill valve does the most work at high RPM and low load.

I do think we spike past relief valve pressure when under load (high pressure, high RPM) and then abruptly letting go of the gas completely. This is really the only scenario I would be concerned about the pressure relief valve as the electronically controlled spill valve may be overwhelmed.

[socks]

When i scale my voltage, the fuel pressure clearly flatlines. no spike, nothing, just hits X psi and holds it.

when its scaled halfway, it hits 1550psi and holds it. doesnt go past it, doesnt fluctuate, just clearly 1550psi.

When its scaled all the way, it hits 1420 and holds it. Again, no fluctuation, just 1420psi.

[cpolly69]

can't help but notice here that this pressure relief valve point would seem to be a great place to put a sending unit for some sort of aftermarket pressure gauge - to my knowledge none of the big boys make a pretty gauge that's made for di pressures - but there's got to be something mechanical in the diesel world out there that could be used here - i think this would be a really good idea to figure out before going further as all this math in one's head on the fly could get dangerous real fast

[Lex]

Are you able to machine a disc with a hole that has half the diameter and get to the spill valve?

Originally Posted by socks When i scale my voltage, the fuel pressure clearly flatlines. no spike, nothing, just hits X psi and holds it. when its scaled halfway, it hits 1550psi and holds it. doesnt go past it, doesnt fluctuate, just clearly 1550psi. When its scaled all the way, it hits 1420 and holds it. Again, no fluctuation, just 1420psi.

[djuosnteisn]

Right, Lex was saying that it may help relieve the spill valves under situations like when you let off the throttle at high rpms, when the spill valves have to recirc the most amount of fuel to alleviate pressure. There could be a spike there, and this safety valve would help.

This is speculation, but still should be kept in mind. Personally, i'd probably try blocking it, but maybe that's too much cow boy for some people, lol.

[Lex]

I certainly wouldn't want to run a mechanical gauge to the cabin at these pressures but hte idea is good. You can still make use of the unscaled sensor signal for measuring the actual pressure.

Originally Posted by cpolly69 can't help but notice here that this pressure relief valve point would seem to be a great place to put a sending unit for some sort of aftermarket pressure gauge - to my knowledge none of the big boys make a pretty gauge that's made for di pressures - but there's got to be something mechanical in the diesel world out there that could be used here - i think this would be a really good idea to figure out before going further as all this math in one's head on the fly could get dangerous real fast

[cpolly69]

what if you could find a sending unit that has the size oraphice you needed for restriction

[Lex]

Originally Posted by cpolly69 what if you could find a sending unit that has the size oraphice you needed for restriction

As long as it is spec-ed for the pressures at hand and gasoline fuel, it could be an option. In the end this can culminate into a "kit" where all bits and pieces are included to "raise your pressure"

I am glad to see the richer AFRs with the upper pressure. The injectors are still opening

[djuosnteisn]

Yup, i think this is going to work really really well!

I'll bring my scope home for the long weekend, and try to get some solid data on injector pulse widths and increased flows etc. Should be a very fun weekend.

[cpolly69]

Originally Posted by Lex As long as it is spec-ed for the pressures at hand and gasoline fuel, it could be an option. In the end this can culminate into a "kit" where all bits and pieces are included to "raise your pressure" I am glad to see the richer AFRs with the upper pressure. The injectors are still opening

by the way i said sending unit - was never talking about putting actual pressurized fuel into the cabin

[KoukiS14]

Well, if you wanted to do an electric fuel pressure gauge in the cabin, it should be possible. I looked around a bit, and 3000 psi sensors are available for under $100. It looks like the threads on the relief valve are straight cut metric threads and not NPT. You can see that it seals using the mating surfaces. I'd guess that it's 12mm 1.5mm thread. We'll have to measure the pitch to find out for sure. I've seen a few sensors with that size fitting.

A 3000 psi electric gauge is the tricky part. You'd probably have to find an aircraft gauge with a 0-5 volt signal input and 0-3000 psi measure. Either that or have your local electrical engineering friend with a fetish for Mazda fueling stuff build a custom digital gauge.

[djuosnteisn]

Originally Posted by KoukiS14 Well, if you wanted to do an electric fuel pressure gauge in the cabin, it should be possible. I looked around a bit, and 3000 psi sensors are available for under $100. It looks like the threads on the relief valve are straight cut metric threads and not NPT. You can see that it seals using the mating surfaces. I'd guess that it's 12mm 1.5mm thread. We'll have to measure the pitch to find out for sure. I've seen a few sensors with that size fitting. A 3000 psi electric gauge is the tricky part. You'd probably have to find an aircraft gauge with a 0-5 volt signal input and 0-3000 psi measure. Either that or have your local electrical engineering friend with a fetish for Mazda fueling stuff build a custom digital gauge.

If we're going to go this far...

The new sensor could possibly serve as a stock sensor replacement.

That would get rid of the 2100psi "clipping" on the stock sensor output, which is the current limiting factor on how high we can scale (until we find other problems, like injectors not spraying correctly, or possibly not even opening).

This may prove easier than a bmw sensor swap. Who knows. Lot's of options now!

[socks]

Originally Posted by Lex Are you able to machine a disc with a hole that has half the diameter and get to the spill valve?

No, I'm hoping to find washers the right size with no holes in them, that way i can make whatever size hole i want, or no hole at all...

Originally Posted by Lex I am glad to see the richer AFRs with the upper pressure. The injectors are still opening

I only think im getting ~100psi more than stock. I was seeing 1750's on average. if im hitting enough to open the relief valve, thats at 1850-1900. so at MOST im getting 150psi more.

[superskaterxes]

lol holy moly this is alot of info

[djuosnteisn]

Originally Posted by socks I only think im getting ~100psi more than stock. I was seeing 1750's on average. if im hitting enough to open the relief valve, thats at 1850-1900. so at MOST im getting 150psi more.

It'd be nice to see what the voltage on the sensor is when you "flat lineing". Also, what do your fuel trims look like with that extra 100psi (assuming the valve opens at 1885 ish)?

[superskaterxes]

how is the rail gona regulate pressure without that relief valve? this shit is so confusing. thanks for gods like DJ and his CKT haha

[Lex]

It's interesting because if 1420 is correct, then the real pressure would have been ~1730.

What probably happened is that the valve relieved/popped and then stayed open holding that pressure.

[superskaterxes]

time to plug that shit, hey ron care to comment?

[djuosnteisn]

Well, i'm gonna go take a nice long pee, then head home and install my new cp-e hpfp and start working on a tune. I'll hopefully have some hard data to post up after i wake up from a turkey nap. Might be as late as sunday. We'll see.

Keep us posted on any progress Sean, good shit.

[superskaterxes]

lol turkey nap!!! FUCK THAT SHIT WORK ON THIS OR ELSE!!!!

haha jk jk, if i know you as well as i think i do dustin, the GF will be screeming for you to come back in from the garage and your gona be like "JUST ONE MORE MAP REVISION SWEEITE!!!"

at that point she whips your ass and all of us loose =( see you on sunday

[cpolly69]

Originally Posted by Lex It's interesting because if 1420 is correct, then the real pressure would have been ~1730. What probably happened is that the valve relieved/popped and then stayed open holding that pressure.

you guys just keep coming up with more reasons/need for there to be an actual gauge
i'm going to talk to my diesel mech buddy about this tonight - to see if they are looking at fuel pressure with anything attached to the rail -
i searched hard today to try and find something online - fail

[superskaterxes]

PPE Diesel Fuel Rail Pressure Gauge

lol 30k psi anyone?

[Thestaplegunkid]

DJ, I just fired up my new forged motor today. I have the KMD version 2 internals. I'm waiting on the Bigger turbo/manifold I ordered to come in, but I'd be more than willing to test one of your circuits on my 08.5 MS3.

[SpeedSixxx]

Originally Posted by Thestaplegunkid DJ, I just fired up my new forged motor today. I have the KMD version 2 internals. I'm waiting on the Bigger turbo/manifold I ordered to come in, but I'd be more than willing to test one of your circuits on my 08.5 MS3.

you would be a great candidate

[m4tic]

so pretty much the pressure relief limit needs to be increased.... i dont think you want to plug it, forcing the car to run way rich (thats how my dad dials in his alcohol SBC, return more or less fuel to the tank to adjust afr) how about we cap or restrict flow at the high pressure return? <-- or is that the same thing

and dj this whole thing pretty much determines if i keep this car or not... its all on yooooouuu :p

[superskaterxes]

Originally Posted by bmorrisj and dj this whole thing pretty much determines if i keep this car or not... its all on yooooouuu :p

lol rofl dustin looks like u got some weight on yoru shoulders!!!


GO MSF COMMUNITY!!!!

[djuosnteisn]

Originally Posted by Thestaplegunkid DJ, I just fired up my new forged motor today. I have the KMD version 2 internals. I'm waiting on the Bigger turbo/manifold I ordered to come in, but I'd be more than willing to test one of your circuits on my 08.5 MS3.

It's my last one, and all yours! PM me your address.

Now we have three 6's and two 3's, should be good enough for the beta testing!

Originally Posted by bmorrisj so pretty much the pressure relief limit needs to be increased.... i dont think you want to plug it, forcing the car to run way rich (thats how my dad dials in his alcohol SBC, return more or less fuel to the tank to adjust afr) how about we cap or restrict flow at the high pressure return? <-- or is that the same thing and dj this whole thing pretty much determines if i keep this car or not... its all on yooooouuu :p

LOL, great....

The relief we're dealing with is likely an "emergency" pressure relief, to keep the rail / injectors from seeing too much pressure. I doubt it has anything to do with our afr's haha.

Restricting it like Lex suggested is probably the best thing to do. Or somehow rigging two of them in a row (essentially doubling the pressure they open at) would work. Last resort would probably be simply blocking it, cause then you lose all emergency relief capabilities.



New pump rocks! I'll have my "dial at minimum" tune done in probably one more map. And then i can start my "dial at mid-way" & "dial at full" tunes. Hopefully won't take more than a couple revisions each, but we'll see .

Also, i got a used dnp that i'm going to try and rig for ewg this weekend as well. That'll eliminate my boost creep issues from the equation, and make A-B comparisons better. Gonna be a long weekend, lol!

[Lex]

The relief valve in question here is a mechanical one and it is a safety pressure relief valve.

The daily running pump pressure is controlled in closed loop through an ELECTRONIC spill valve which we are not modifying.

Good luck with the tune Dustin, enjoy the turkey, and let me know how it goes.