Upgrading secondary injectors, why the need for an aftermarket FPR?
08-22-17, 10:22 AM
#1
RX-7 Bad Ass
Thread Starter
iTrader: (55)
Upgrading secondary injectors, why the need for an aftermarket FPR?
Hello everyone -
So I've been building an FD for a buddy of mine, starting to get to the engine part of the deal. Long story short, his old FD was wrecked, he bought a roller and we're going through every nut and bolt in the car. Got most of the interior done and suspension, starting in on the engine.
Anyhow, it's common knowledge that when you get past a certain power level it's wise to get some more injector headroom. For a long time going with 1300cc injectors was a good, easy plug in option for more power on the twins. As of late it seems like a lot of these have had issues - sticking open or closed, etc. Don't want a bad injector to ruin a good engine!
That said, going with an aftermarket fuel rail and ID2000's or something of that nature is a good way to go. But, you are also looking at having an aftermarket FPR as well. What used to be a reasonable cost for 1300cc injectors is pushing $1000 for a rail, injectors, FPR, fittings, etc.
At what point is the stock FPR a weak link? If you're not needing to adjust fuel pressure, it seems like it would be fine.
Also, I SWEAR I saw someone that made an aftermarket secondary fuel rail for top feed injectors that used the stock FPR, it had the O-ring port and two threaded holes to bolt that on. Now, however, I can't find it.
To get back to the car in question, the car will be running twins, maybe BNR's at some point, but he's not looking for big power, 350hp maybe. Definitely not going single or anything. All controlled with a PowerFC.
Any thoughts?
Thanks,
Dale
So I've been building an FD for a buddy of mine, starting to get to the engine part of the deal. Long story short, his old FD was wrecked, he bought a roller and we're going through every nut and bolt in the car. Got most of the interior done and suspension, starting in on the engine.
Anyhow, it's common knowledge that when you get past a certain power level it's wise to get some more injector headroom. For a long time going with 1300cc injectors was a good, easy plug in option for more power on the twins. As of late it seems like a lot of these have had issues - sticking open or closed, etc. Don't want a bad injector to ruin a good engine!
That said, going with an aftermarket fuel rail and ID2000's or something of that nature is a good way to go. But, you are also looking at having an aftermarket FPR as well. What used to be a reasonable cost for 1300cc injectors is pushing $1000 for a rail, injectors, FPR, fittings, etc.
At what point is the stock FPR a weak link? If you're not needing to adjust fuel pressure, it seems like it would be fine.
Also, I SWEAR I saw someone that made an aftermarket secondary fuel rail for top feed injectors that used the stock FPR, it had the O-ring port and two threaded holes to bolt that on. Now, however, I can't find it.
To get back to the car in question, the car will be running twins, maybe BNR's at some point, but he's not looking for big power, 350hp maybe. Definitely not going single or anything. All controlled with a PowerFC.
Any thoughts?
Thanks,
Dale
08-22-17, 11:03 AM
#3
RX-7 Bad Ass
Thread Starter
iTrader: (55)
Well, there ya go 
. Looked it up, looks like stock fuel pressure is about 37 psi.
Does this hold true with other aftermarket injectors?
Dale
. Looked it up, looks like stock fuel pressure is about 37 psi. Does this hold true with other aftermarket injectors?
Dale
08-22-17, 11:27 AM
#4
Dale,
Fuel injection pressure has increased over the years, so it depends on what era you are talking about.
In the very old days you had continuous fuel injection with a fuel distributor and nozzles that ran at lower pressure, closer to a carb fuel system or a mechanical diesel injection system. That was on a lot of European cars and some American cars. This was the old Bosch K-Jetronic based systems, with the K standing for the German word for "continuous." Other simple multi point injection, like you would find on old 3 and 5 series BMW's or say a Datsun 280ZX, ran at very low pressure compared to modern port injection.
Sequential multi port injection started to get popular in the mid 80s, starting with the Bosch "Motronic" system that was at least partly licensed by Denso and used in Rx-7's. In the age of the 2nd and 3rd generation Rx-7, 2.5 bar (37psi) were common fuel pressures, and the fuel systems were running return lines. In the late 90s you had more 3 bar return fuel systems. Once the mid 2000s hit, like in the era of the Rx-8, it was not uncommon to have 4 bar (60psi) or higher systems running returnless. For a returnless port injected engine the regulator is in the fuel tank and the ECU is compensating for manifold pressure changes by adjusting the injector pulsewidth. That's in contrast to the conventional regulator where the rail pressure is physically changing according to a pneumatic manifold pressure signal.
Aftermarket injectors always follow OEM grade designs, 5-10 years after the OEM design goes into the market. The ID injectors are modified Bosch EV14, which is the current (or at least very recent) generation Bosch port injector. It's mostly designed for returnless fuel systems and operates better at higher rail pressures. I'm not sure if newer generation injectors will come out, as all the serious research is being done on progressively higher pressure gasoline direct injection. 10 years ago they were 120 bar systems, then 150-160 bar, now 200 bar is normal and 250 is on the most advanced systems, with 300 bar just entering the market now. Port injection is not developing so fast, as the main application now are port + direct injection systems.
The other thing to consider is that when you rewire the fuel pump to delete the 2-speed voltage resister you increase fuel rail flow at idle. The stock fuel pressure regulator can't bypass all that fuel, so you can get a richer idle even on stock injectors.
Fuel injection pressure has increased over the years, so it depends on what era you are talking about.
In the very old days you had continuous fuel injection with a fuel distributor and nozzles that ran at lower pressure, closer to a carb fuel system or a mechanical diesel injection system. That was on a lot of European cars and some American cars. This was the old Bosch K-Jetronic based systems, with the K standing for the German word for "continuous." Other simple multi point injection, like you would find on old 3 and 5 series BMW's or say a Datsun 280ZX, ran at very low pressure compared to modern port injection.
Sequential multi port injection started to get popular in the mid 80s, starting with the Bosch "Motronic" system that was at least partly licensed by Denso and used in Rx-7's. In the age of the 2nd and 3rd generation Rx-7, 2.5 bar (37psi) were common fuel pressures, and the fuel systems were running return lines. In the late 90s you had more 3 bar return fuel systems. Once the mid 2000s hit, like in the era of the Rx-8, it was not uncommon to have 4 bar (60psi) or higher systems running returnless. For a returnless port injected engine the regulator is in the fuel tank and the ECU is compensating for manifold pressure changes by adjusting the injector pulsewidth. That's in contrast to the conventional regulator where the rail pressure is physically changing according to a pneumatic manifold pressure signal.
Aftermarket injectors always follow OEM grade designs, 5-10 years after the OEM design goes into the market. The ID injectors are modified Bosch EV14, which is the current (or at least very recent) generation Bosch port injector. It's mostly designed for returnless fuel systems and operates better at higher rail pressures. I'm not sure if newer generation injectors will come out, as all the serious research is being done on progressively higher pressure gasoline direct injection. 10 years ago they were 120 bar systems, then 150-160 bar, now 200 bar is normal and 250 is on the most advanced systems, with 300 bar just entering the market now. Port injection is not developing so fast, as the main application now are port + direct injection systems.
The other thing to consider is that when you rewire the fuel pump to delete the 2-speed voltage resister you increase fuel rail flow at idle. The stock fuel pressure regulator can't bypass all that fuel, so you can get a richer idle even on stock injectors.
Last edited by arghx; 08-22-17 at 11:36 AM. Reason: a lesson on fuel injection history
08-22-17, 02:11 PM
#5
Apologies if I am mistaken, but I don't recall any upgraded FPR when I went to this system offered by Rotary Performance; fuel rail + secondary injectors.
https://rotaryperformance.com/collec...ant=1119537800
https://rotaryperformance.com/collec...ant=1119537800
08-22-17, 03:05 PM
#6
However, note that my car has stock primaries and ID2000 secondaries, base pressure (with an aftermarket FPR) is set to 37psi, and car boosts to 9psi only (270whp), and max duty cycle on ID2000s hits whopping 62% for this power level. Hence I assume 37psi on IDs is not the way to go.
08-23-17, 10:05 AM
#7
RX-7 Bad Ass
Thread Starter
iTrader: (55)
Good stuff here!
First, makes sense about the ID injectors needing more fuel pressure. I would imagine that they would work at lower pressure but they just won't deliver the full 2000cc volume and the spray pattern may not be as good.
I have 1300cc injectors on my car that I got quite some time ago - knock on wood they've been dead reliable for me. From what I've heard newer ones have had issues. That said, I'm making in the 350hp ballpark with good headroom on duty cycle. This is with a rewired Walbro 255 fuel pump. Stands to reason the 2000's at 37psi should do well, you would want more fuel pressure to fully utilize them or for a single turbo/400hp+ setup.
Running higher fuel pressure with stock 550cc primaries, are they happy with it? I imagine the map will need some tuning to compensate for the higher pressure so you aren't rich and idle/cruise/light load.
Topolino, THANK YOU, that RX7.com fuel rail is the one I had seen. With their injectors that would be $510 for the upgrade. Going with a Full Function rail and 2000 ID injectors you're at $875, that's some substantial money.
Dale
First, makes sense about the ID injectors needing more fuel pressure. I would imagine that they would work at lower pressure but they just won't deliver the full 2000cc volume and the spray pattern may not be as good.
I have 1300cc injectors on my car that I got quite some time ago - knock on wood they've been dead reliable for me. From what I've heard newer ones have had issues. That said, I'm making in the 350hp ballpark with good headroom on duty cycle. This is with a rewired Walbro 255 fuel pump. Stands to reason the 2000's at 37psi should do well, you would want more fuel pressure to fully utilize them or for a single turbo/400hp+ setup.
Running higher fuel pressure with stock 550cc primaries, are they happy with it? I imagine the map will need some tuning to compensate for the higher pressure so you aren't rich and idle/cruise/light load.
Topolino, THANK YOU, that RX7.com fuel rail is the one I had seen. With their injectors that would be $510 for the upgrade. Going with a Full Function rail and 2000 ID injectors you're at $875, that's some substantial money.
Dale
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08-23-17, 07:31 PM
#8
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Jobro and i found the early (1993) Q45 fuel pressure regulator *looks* like it would fit the FD, and it runs at 43psi. its not a huge difference from stock, but its also small enough where the stock ECU would even still run ok.
i dont have the Nissan number handy, but BWD is 24001, Standard is PR219, beck arnley is 158-0820
i dont have the Nissan number handy, but BWD is 24001, Standard is PR219, beck arnley is 158-0820
08-24-17, 10:28 AM
#9
Aftermarket fuel rail
Dale,
I had been using The Rotary Performance aftermarket fuel rail for almost two years with 550cc primaries and 2200cc Bosch Ev14 secondary's with the stock FPR with no problem at all. This is with twin '99 sequentials still. I was boosting around 15 psi with injector duty in the 65% range on the PFC and WOT AFR's in the mid to high 10's. RWHP was likely around 340-345 (dynoed at 326RWHP at 14 psi). I plan on using this same setup with the newer Hitachi SP turbos with WM injection after my current whole car rebuild is complete. I believe there is enough headroom to even get up to 400-425RWHP if needed.
Mike
I had been using The Rotary Performance aftermarket fuel rail for almost two years with 550cc primaries and 2200cc Bosch Ev14 secondary's with the stock FPR with no problem at all. This is with twin '99 sequentials still. I was boosting around 15 psi with injector duty in the 65% range on the PFC and WOT AFR's in the mid to high 10's. RWHP was likely around 340-345 (dynoed at 326RWHP at 14 psi). I plan on using this same setup with the newer Hitachi SP turbos with WM injection after my current whole car rebuild is complete. I believe there is enough headroom to even get up to 400-425RWHP if needed.
Mike
08-24-17, 12:38 PM
#10
RX-7 Bad Ass
Thread Starter
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Nice! It looks like that would be a good setup for what he's looking to do.
Thanks on the Q45 regulator, I'm going to have to look that up. That's a neat idea! I know there's also a NISMO regulator that's similar in appearance but has an adjustment bolt on the top to adjust fuel pressure. Not sure what the range of adjustment is though.
Dale
Thanks on the Q45 regulator, I'm going to have to look that up. That's a neat idea! I know there's also a NISMO regulator that's similar in appearance but has an adjustment bolt on the top to adjust fuel pressure. Not sure what the range of adjustment is though.
Dale
08-25-17, 08:02 AM
#11
Dale I happen to have new oem fpr if u r interested. My cay dyno at 400 @15 psi, with oem 50 and ID2000, with Sard fpr (pressure set at 40) and and Radom Engineering FPD and duty cycle of the injectors are 65%, on a 8374 IWG setup. According to Speedone (Dave) this past May when I got tune fuel is not an issue with the setup, it was getting too much fuel and had to scale it down.