BamSHO
SHO Member
Owning a SHO, you are in an very exclusive club. Seems like everyone has a mustang, Camaro, BMW, etc. Just think how often you see a SHO. You become part of a family, it's hard to explain.
Limitations of fuel system?
- Thread starter iminhell
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Blackhawk77
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With 3 kids I needed the room. The SHO is a sweet car but I'm not sure it would be in my top 3 if interior space wasn't a requirement.
Does it have the "upgraded" intercooler though? I still think at DD levels, the SHO would be detuned to remain reliable. If it is a DD with near 600 AWHP, that would be quite the feat. Looking forward to those promised timeslips!
You're correct, it does have a fancy FMIC on there...he himself has directly said he's been using it on the street as a DD at the 588 level.
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shomethe$$$
SHO Member
On e85 it won't even come close to this.
BlownSkillet
New Member
Hey iminhell, getting ready to sell my 2000 M-5 and start looking and the 4th gen SHO's. Interested in somewhat of a classic? Last of the stick M-5's! 
Hey iminhell, getting ready to sell my 2000 M-5 and start looking and the 4th gen SHO's. Interested in somewhat of a classic? Last of the stick M-5's!
Nice car but no.
After all the BMW's I've test drove in the last few months, the 135 is what I want if I get a BMW.
I did test drive a '13 SHO the other day, my first. I have never been in a seat so comfortable. The transmission was butter smooth. I was actually pretty impressed with the car, not the ignorant and fidgety salesman.
Drove a 370z right after. What a POS. Dynamic alignment isn't it's best attribute.
Capri83RS
Member
There are three of them at my work, including mine.
Cruxin
Member
So getting back to the original topic of this thread..... It is very common in the Subaru world to do a Walbro 255lph fuel pump upgrade. Is that the first "Fuel System" upgrade to do on the SHO?
Capri83RS
Member
I dont think that will help, as your DFI system is running 2300psi stock. You either have to swap out the entire system, or make do.
From what Ive read in my research, the driveline will give up before the fuel system does.
From what Ive read in my research, the driveline will give up before the fuel system does.
I'm quite sure you business partner would be able to provide a better explanation but,
In the SHO fuel system you're dealing with 2 fuel pumps and 2 pressure ratios.
The Low Pressure Fuel Pump, LPFP, is in the tank and sends fuel to the High Pressure Fuel Pump, HPFP. The LPFP Runs at around 65psi (depending on year). But that pressure really doesn't matter unless it falls off at high RPM. It's the volume the pump can flow that matters. If at high RPM/WOT the LPFP pressure falls, then a larger pump is needed.
The reason the pressure of the LPFP doesn't matter is that it doesn't contribute or add to the pressure coming out of the HPFP. Gasoline is, for the most part, not compressible. Meaning that if you start with 65psi and add 2,000psi you won't end up with 2,065psi. It will only be 2,000psi.
The rotor of the HPFP is a fixed volume and being Gas isn't compressible, you'll always have the same volume of fuel per RPM at the same pressure.
The way to determine which you need to upgrade is this,
Datalog the pressure of both (I don't know the specific PID's) vs MAF Flow (Load) and RPM. Also do the same with Injector Duty Cycle (or similar).
Graph it out.
If pressure, MAF and INJDC all follow similar trends, nothing is wrong and you have not reached any mechanical limitation. If one doesn't follow a trend, then you have reached a limit.
If INJDC goes up and pressures go down, you have reached a flow limit. This is a easy find. From there you need to look at LPFP vs HPFP. If the LPFP is falling with the HPFP, the LPFP is the first limitation, upgrade it. If only the HPFP is falling, then it is the limitation, I'm not sure of the solution to this W/O adding PFI.
From what I've read, most of the limitations are based on circumstantial evidence and much hearsay. I have not seen datalogs proving anything, to a limit or against. My personal belief is more tuning is needed to prove or disprove anything.
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