255 + 450 double pumper
#31
I know people use'em. But show me a REAL built race car or OEM car that would use a pressure switch to control a fuel pump. Too many failure modes there for me. If the LOAD is calculated by MAP only then I see what your saying about the fidelity of control being the same. I was under the impression (at least for the Evo X) that the load was much more involved than just MAP. If that was the case why have a LOAD value in the ECU at all and just reference everything from the MAP tables. I suspect there is more to the LOAD value. I did do some data diving and in my thread measured and plotted LOAD vs. BOOST and yes they are MOST of the time similar and linear but there is variance. The long term reliability is in question, Mitsubishi couldn't even get the switching correct for the Evo X and the fuel pump relays die like crazy. With big big pumps a progressive controller tied to injector duty cycle would be ideal.
#32
Originally Posted by Jaraxle
I know people use'em. But show me a REAL built race car or OEM car that would use a pressure switch to control a fuel pump. Too many failure modes there for me. If the LOAD is calculated by MAP only then I see what your saying about the fidelity of control being the same. I was under the impression (at least for the Evo X) that the load was much more involved than just MAP. If that was the case why have a LOAD value in the ECU at all and just reference everything from the MAP tables. I suspect there is more to the LOAD value. I did do some data diving and in my thread measured and plotted LOAD vs. BOOST and yes they are MOST of the time similar and linear but there is variance. The long term reliability is in question, Mitsubishi couldn't even get the switching correct for the Evo X and the fuel pump relays die like crazy. With big big pumps a progressive controller tied to injector duty cycle would be ideal.
This isn't an EvoX, it's an 8/9, and at that power it should be on speed density, which means load and map are interchangeable. Most EMS systems do use boost isn't of a load number on the timing and fuel tables actually...
You talk about failure modes with a Hobbs switch, but your method requires the addition of 2 or 3 relays. Sounds like just as much failure potential to me...
#33
Thank you sir. Someone was running 255+450. I just thought, I would run 255 with stock wires and stock fuel line and 450 with hobbs switch using evap line as a fuel line for it.
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xRoguex (Sep 4, 2019)
#34
Looks like the stock wires can handle 450 on cruising (stock low/high voltage) and I could do double 450. But I would like to have 6mm2 wires for both pumps, when on boost. So the stock wires wouldn't overheat and both pumpd get good voltage. I know people run 450 twins and the 1st pump is only on stock wires, but I don't feel comfortable to do it.
#35
On the EvoX you get weird averaging because it mixes MAP and MAF.
This isn't an EvoX, it's an 8/9, and at that power it should be on speed density, which means load and map are interchangeable. Most EMS systems do use boost isn't of a load number on the timing and fuel tables actually...
You talk about failure modes with a Hobbs switch, but your method requires the addition of 2 or 3 relays. Sounds like just as much failure potential to me...
This isn't an EvoX, it's an 8/9, and at that power it should be on speed density, which means load and map are interchangeable. Most EMS systems do use boost isn't of a load number on the timing and fuel tables actually...
You talk about failure modes with a Hobbs switch, but your method requires the addition of 2 or 3 relays. Sounds like just as much failure potential to me...
#36
The solid state relays I used have a 1000 year operating time. Sounds insane but it's in the data sheet for it. No moving parts, internal optical isolated. The thing is that if the ECU decides to kill power to the pump (aka: a crash!) You REALLY WANT All pumps turnoff. You would never want a scenario where a fuel pump is feeding a fire! I know people do the Hobbs method and I almost did too,. but instead went a safer and more reliable method. I documented everything here on this forum only. Just trying to help.
I don't know how they could even come up with a number like that. To my knowledge there isn't a potting compound in existence that could last that long, maybe they invented the roman concrete of potting compound.
#37
#38
The solid state relays I used have a 1000 year operating time. Sounds insane but it's in the data sheet for it. No moving parts, internal optical isolated. The thing is that if the ECU decides to kill power to the pump (aka: a crash!) You REALLY WANT All pumps turnoff. You would never want a scenario where a fuel pump is feeding a fire! I know people do the Hobbs method and I almost did too,. but instead went a safer and more reliable method. I documented everything here on this forum only. Just trying to help.
And... 1k years... lol.
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MR ArcticC (Aug 8, 2019)
#39
#40
And check out this plot I made from my car (and taken from my fuel pump thread):
Notice how at around 18psi the injectors can need anywhere from 40% duty cycle to 80%+ duty cycle !!!
This is what I meant by using boost only to trigger a pump seems sloppy. You can be off by the actual fuel consumption needed by the engine by 100% !
Notice how at around 18psi the injectors can need anywhere from 40% duty cycle to 80%+ duty cycle !!!
This is what I meant by using boost only to trigger a pump seems sloppy. You can be off by the actual fuel consumption needed by the engine by 100% !
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2006EvoIXer (Aug 8, 2019)
#42
Duty cycle is function of the time it takes for the engine to complete a cycle (this goes down as RPM goes up) vs dwell time. As rpm goes up, the injectors have a smaller window of time to inject fuel. So a 5ms PW at 3k rpms is lower duty cycle than a 5ms PW at 8k rpm. But its the same amount of fuel...
IDC is not a value to determine the fuel demand/fuel flow required. All it tells you is when you're out of injector (or pump if you see pressure dropping). IPW tells you the amount of fuel being used.
Originally Posted by google search for an easy example
At 6000 rpm it takes 20 ms for two revolutions. If a fuel injector is activated for 15 ms (the IPW) at 3000 rpm the duty cycle is 37.5% (15 ms/40 ms), or rpm times IPW divided by 1200 equals IDC in percent. If an injector is powered for 15 ms at 6000 rpm, then IDC is 75% (15 ms/20 ms).
#44
The big turbo car I have here that makes 860whp, runs two AEM 400LPH 044 style pumps in a surge tank, fed by twin walbro 255's in the stock tank. The 255 run full power full time. We only run one 044 until 18-20psi, then the second pump comes. Works like a charm.
We tried runn just one 255 until 5-10psi, but we found there would be random times the surge tank would go dry, so we wired them up to run full time.
We tried runn just one 255 until 5-10psi, but we found there would be random times the surge tank would go dry, so we wired them up to run full time.
#45
The big turbo car I have here that makes 860whp, runs two AEM 400LPH 044 style pumps in a surge tank, fed by twin walbro 255's in the stock tank. The 255 run full power full time. We only run one 044 until 18-20psi, then the second pump comes. Works like a charm.
We tried runn just one 255 until 5-10psi, but we found there would be random times the surge tank would go dry, so we wired them up to run full time.
We tried runn just one 255 until 5-10psi, but we found there would be random times the surge tank would go dry, so we wired them up to run full time.