OFFICIAL: S2 Fuel Pump Thread - RX8Club.com



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Old 03-13-2016, 07:53 PM   #1
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OFFICIAL: S2 Fuel Pump Thread

Pre-face: It will take some time to post up all the photos and info so please be patient. Already typed most of this and then lost it somehow, so already off to a great start.

About 6 months ago I sent a brand new S2 fuel pump assembly to Deatschwerks for testing. Four tests were made. One pair of tests is run at 10 Volts to simulate low speed resistor mode and then also at 13.5 Volts to simulate high load conditions. The other pair of tests are for the factory Denso pump that comes in the OE housing and then also for the Deatschwerks DW65C 265LPH pump installed in an otherwise unmodified factory housing.

The purpose of the tests is to determine the real output of the OE S2 pump assembly and then also the modified output from the 265LPH pump. This removes all the BS assumptions and guesstimations.

First and foremost observation is that the internal relief valve blows off around 50 psig and once that starts happening the true total output is unknown because what's going through the relief valve can't be measured without a lot of headaches and is just too much effort. If I had to do it again I probably would have asked for 45 psig to be used as a testing point, but I think we can't make some reasonable estimates there regardless. Ultimately what's going out the housing discharge fitting is all that matters to the engine.

The S2 pressure relief valve differs from the S1 in that it's an integral, fully enclosed, replaceable metal housing assembly that is held in place by the snap-lock for the sock filter. It can't blow apart and doesn't require melting, etc. modification like the S1 PRV. In theory you could swap it out for a different pressure set-point or adjustable PRV if you can find one with a similar body profile, or even make a plug to block it off entirely if you decide to install an external PRV instead. The overall design changes from the S1 pump are a definite improvement in many areas.

The OE Denso pump is pretty decent. At 13.5V and 45 psig it's output is approx. 210LPH. If fitted with a Kenne Bell 17V Boost-A-Pump it should be enough for high boost but not too crazy 2-rotor turbo engine on gasoline or a reasonable boost 2-rotor turbo engine on E-85. At the same volts and pressure the DW65C 265LPH pump has approx 230LPH output flow, so an improvement over OE, but maybe not really necessary for most. Assuming I ever get motivated and finish putting my RX8 with E85 NA engine back together it's certainly way more than enough for my needs. The 265LPH rating is for 40 psig and we can see it's actually exceeding this in the test. Of course everything is brand new, so no shocker. It appears that the OE housing and replaceable internal filter assembly when new isn't excessively restricted in any way. They also now offer a DW300 pump that will fit the same profile and is rated for 340LPH, but it hasn't been tested by me.

In the low-speed (10V) resistor mode, the two pumps are not too far apart at 45 psig; 145LPH for the OE Denso pump and 165 LPH for the DW65C pump. I haven't ever seen any testing for low speed mode and was just curious to have the data. Now we know.

The electrical amp data is self explanatory, but it provides a good idea of what electrical loads can be expected and planned for.

The tests cost me around $120 if I recall correctly, but then it came with the DW65C pump already installed in the OE housing. No biggie as I had already torn it down previously and will post up pictures of everything at some point. This is for the usual suspects that say I never contribute anything useful to the forum ... heh.
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OFFICIAL: S2 Fuel Pump Thread-s2-fuel-pump-test0001.jpg   OFFICIAL: S2 Fuel Pump Thread-s2-fuel-pump-test0002.jpg   OFFICIAL: S2 Fuel Pump Thread-s2-fuel-pump-test0003.jpg   OFFICIAL: S2 Fuel Pump Thread-s2-fuel-pump-test0004.jpg  

Last edited by TeamRX8; 03-14-2016 at 12:06 AM.
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Old 03-13-2016, 07:53 PM   #2
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Old 03-13-2016, 07:54 PM   #3
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Old 03-13-2016, 07:54 PM   #4
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Old 03-13-2016, 08:54 PM   #5
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Is this for a stock S-II with stock pump and fittings?
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Old 03-14-2016, 10:35 AM   #6
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Awesome stuff, thanks for sharing. I think I will be going with the S2 pump and a KB boost a pump. That should be plenty for my setup.
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Old 03-14-2016, 11:07 AM   #7
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Thanks, that is some interesting info. One thing I don't understand is how the fuel line pressure can be higher than the relief valve set point. The spec is 54.4-60 psi, and on my car it is 59 psi at idle...
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Old 03-14-2016, 11:37 AM   #8
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The unrestricted flow for 10V is 145LPH @ 45 psig. I could calculate it out, but the flow to the engine at idle is only a small fraction of that. Since the fuel system is non-return that means all the excess is going through the PRV, which is not that big. In short, dumping everything through the PRV creates a lot of backpressure on the pump at low flow to create that pressure spec. We didn't test that, but it could be done by throttling an outlet discharge valve back to a calculated idle flow rate.
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Old 03-14-2016, 04:01 PM   #9
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Good write up, like posted before, i changed the oem pump inside s2 assembly for a denso 265 and i ran it like that for 1k miles last year on rew swap, no return.

This year ill install a external fpr and run a return line and hook it up to a radium jet venturi and see how it works. Im doing this because fuel pressures are unstable at the moment and will be hard to tune that way

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Old 03-25-2016, 05:01 PM   #10
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On you Mark, thanks for the info.
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Old 03-26-2016, 06:59 PM   #11
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Quote:
Originally Posted by TeamRX8 View Post
The unrestricted flow for 10V is 145LPH @ 45 psig. I could calculate it out, but the flow to the engine at idle is only a small fraction of that. Since the fuel system is non-return that means all the excess is going through the PRV, which is not that big. In short, dumping everything through the PRV creates a lot of backpressure on the pump at low flow to create that pressure spec. We didn't test that, but it could be done by throttling an outlet discharge valve back to a calculated idle flow rate.
Interesting ..... I found when I put a DW300 in a S1 assy. that i had bad pressure spikes when the pump switched over to 'hi' . After drilling out the siphon , i lost the spikes , but pressure did not drop from where it was . I'm thinking maybe the PRV cracks at lower psi but doesn't full open till 55-60 .
Just looking at the way flow drops away more dramatically on the dw65 ......... maybe it's going to flow a lot more in the actual car as the flow increases to the injectors and the siphon isn't flowing much.

Wait a cotton pickin' minute ! is this the same 'Team' that disappeared without trace last year ?

Last edited by Brettus; 03-26-2016 at 07:20 PM.
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Old 03-28-2016, 09:37 PM   #12
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Does anyone know a way to remove the internal fpr in s2 assembly
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Old 05-13-2016, 12:24 AM   #13
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Autozone offers only one brand available for the RX-8 - the Spectra one priced at approximately $299.99 - 349.99. is that a good brand?
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Old 05-13-2016, 10:09 AM   #14
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Here ya go, Requiem:

The great and powerful Paul over at Mazmart can help you get a quality fuel pump

MAZMART - Serving The Mazda Community Since 1980. RX8 Fuel Pump & Parts
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Old 06-13-2017, 03:05 PM   #15
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TX

Does anyone know if the S2 pump has the same pressure specs as the S1? I have an 04, which I have replaced the pump with an S2 pump and assembly as the S1 pump assembly gave me much trouble at the track (left-hand turns, etc. as discussed in many other threads). I bought a used S2 pump about 1.5 years ago (~30k miles at the time). I have put about 6k on it and done 10 track weekends on this time. Recently my car feels sluggish at high-end RPM +7k, my AFR are quite poor 13.3-13.6 at those RPMís while data from last year was about 12.4. The Engine is quite recent (~1.5k), and I do feel the SSV opening for what I consider normal.

I have replaced coils, cables, and plugs. Checked for vacuum leaks and I havenít found one, also cleaned the MAF and inspected the eccentric shaft position sensor (just in case). Current codes are P0410 (Air System), and P0037 (HO2S Heater Control Circuit Low Voltage), due to the removal of the air pump and the lack of a cat on the mid pipe.

My next step is to check the fuel pump. I installed the Aeromotive quick-connect and a ProSport fuel pressure gauge and I went through the procedure to test the pump as described in the service manual. The expected pressures are between 54-62psi, with a holding of +29psi. My current pressures are 52-55psi with holding pressure 48psi. I have not seen a dramatic decrease in pressure at high RPMs, which I was kind of hoping to blame the pump and get on with it, but itís not the case. The running pressure does seem low, but I donít know if the S2 pump could have different specs and if the test could be any different. I havenít found any pressure test instructions specific for the S2 pump.

Does anyone have info on the S2 fuel pump pressures?

Thanks,
Piero
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Old 06-13-2017, 03:40 PM   #16
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Quote:
Originally Posted by visionario View Post
Does anyone know if the S2 pump has the same pressure specs as the S1? I have an 04, which I have replaced the pump with an S2 pump and assembly as the S1 pump assembly gave me much trouble at the track (left-hand turns, etc. as discussed in many other threads). I bought a used S2 pump about 1.5 years ago (~30k miles at the time). I have put about 6k on it and done 10 track weekends on this time. Recently my car feels sluggish at high-end RPM +7k, my AFR are quite poor 13.3-13.6 at those RPM’s while data from last year was about 12.4. The Engine is quite recent (~1.5k), and I do feel the SSV opening for what I consider normal.

I have replaced coils, cables, and plugs. Checked for vacuum leaks and I haven’t found one, also cleaned the MAF and inspected the eccentric shaft position sensor (just in case). Current codes are P0410 (Air System), and P0037 (HO2S Heater Control Circuit Low Voltage), due to the removal of the air pump and the lack of a cat on the mid pipe.

My next step is to check the fuel pump. I installed the Aeromotive quick-connect and a ProSport fuel pressure gauge and I went through the procedure to test the pump as described in the service manual. The expected pressures are between 54-62psi, with a holding of +29psi. My current pressures are 52-55psi with holding pressure 48psi. I have not seen a dramatic decrease in pressure at high RPMs, which I was kind of hoping to blame the pump and get on with it, but it’s not the case. The running pressure does seem low, but I don’t know if the S2 pump could have different specs and if the test could be any different. I haven’t found any pressure test instructions specific for the S2 pump.

Does anyone have info on the S2 fuel pump pressures?

Thanks,
Piero
375—450 kPa {3.83—4.58 kgf/cm 2, 54.4—65.2 psi}

http://www.normalexception.net/docum...p%20Manual.pdf
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Old 06-13-2017, 03:55 PM   #17
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Quote:
Originally Posted by visionario View Post
Recently my car feels sluggish at high-end RPM +7k, my AFR are quite poor 13.3-13.6 at those RPMís while data from last year was about 12.4.
What is your long term fuel trim under load ?
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Old 06-13-2017, 10:08 PM   #18
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Originally Posted by 9krpmrx8 View Post
375ó450 kPa {3.83ó4.58 kgf/cm 2, 54.4ó65.2 psi}

http://www.normalexception.net/docum...p%20Manual.pdf
Thanks 9k!

I see no difference in the specs... perhaps a weak pump.
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Old 06-13-2017, 10:26 PM   #19
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What is your long term fuel trim under load ?
I'm looking at the logs, but I see no short/long term fuel trims recorded. I use the dashcommand app; I may need to add the data channels. I will test it later this week and gather the data.
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Old 06-14-2017, 12:42 AM   #20
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If you go to my original test data the relief valve on the S2 pump blows off earlier than the service hold pressure. In a dead head or low fuel flow scenario when the pump is running those pressures are obtainable because the relief valve can't flow enough to keep the pressure down. However, with the relief valve pressure being lower than the stated hold pressure I don't see how it could prevent it from blowing off until the pressure gets down to where the relief valve closes.
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Old 06-19-2017, 12:35 PM   #21
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I'm looking at the logs, but I see no short/long term fuel trims recorded. I use the dashcommand app; I may need to add the data channels. I will test it later this week and gather the data.
I gathered some data, but it doesn't seem that the long term fuel trim data channel is recording properly, it is flat at zero the whole time while short term does fluctuate. I run for 15-20 minutes, but the long trim never changed. I may need to contact Palmer to check on the App settings/channels.
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Old 06-19-2017, 12:43 PM   #22
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ok, but perhaps that should go into a separate troubleshooting thread. This one is intended to be info only for that purpose.
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