Quote:
Originally Posted by thejeremyman9
I run E30 fuel on the MHD stage 2+ E20 map. I sometimes get a very brief dip in HPFP pressure before it stabilizes the rest of the pull. I know i am operating near the stock HPFP limit. In other words you can see brief dips in HPFP pressure without a full "crash", especially if you are pushing the hardware limits with your boost/fueling.
We (I) know very little about the system/sensor that controls the HPFP pressure. There was a little discussion about it a while back but all speculation and I've never seen any official documentation/description of the system/sensor. The general guidance/rule of thumb is just upgrade the HPFP if you need the extra fueling - in other words no way to manipulate the system that's controlling the high pressure to get anything more out of the mechanical HPFP. Just increase fuel supply.
The main question I've always had is that, if your HPFP pressure "crashes" (i.e., because you are demanding more fuel than it can supply), does this actually mean that the system controlling it is fully closed and you aren't returning any to the tank? I don't think we know for certain...
In OP's case the similar question i have is, is this system just responding too slow? Maybe its returning too much fuel to the tank for that brief moment causing the pressure dip? Presumable hes not demanding too much fuel or else his HPFP would continue to fall behind, but this depends on his fuel used, or it could be a situation similar to mine.
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Thank you for the detailed response. The reason I asked is because I've had a similar dip in my car. The lowest HPFP reading came in at 1678 PSI. In my case I'm on the BM3 Stage 1 map. I got in the habit of adding 1.5 to 3 gallons of E85 to my 91 octane fuel. The dip happened while on higher ethanol content (2.5 gallons of E85). I've since lowered it to 1-1.5 gallons of E85 and the dip has not returned. Granted I've been adding E85 inconsistently on a weekly basis. That is to say sometimes I'll add 3 gallons and other times just one.
I noticed the dip took place right when the car hit full boost and the quickly normalized with no other dips. The car accelerated smoothly with no hiccups.