MazterDizazter Posted March 10, 2008 Share Posted March 10, 2008 Hey guys, I'm a bit new to the whole upgrading fuel injection area. I have an L28ET, which means I have 265cc injectors. I would like to upgrade to a Pallnet fuel rail but I don't want to keep the barb-style since I will be upping the power eventually and will want larger injectors in the future. My question is more about fuel injectors and flow in general. For example, if I were to drop in RX-7 550cc injectors, a Walbro 255lb/hr fuel pump, and an adjustable FPR without making any adjustments to the ECU, would the difference in size or impedance cause it to run differently or would the injectors essentially just run at a lower duty cycle? Any help would be appreciated; thanks! Quote Link to comment Share on other sites More sharing options...
Matt K Posted March 10, 2008 Share Posted March 10, 2008 You will require some way to tune for larger injectors. Keep in mind that most of these rails are for top feed injectors, and RX7 injectors are side feed (at least FD ones are, not sure about FC). If you had a Z31 ECU swap, you could ROM tune or possibly use something like an SAFC (not really recommended). Otherwise it'll have to be a standalone, such as Megasquirt. That's just too much of a difference...you MIGHT be able to get away with some SVO 310cc injectors with a rising rate fuel pressure regulator, but it would most likely not work out too well... Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 11, 2008 Author Share Posted March 11, 2008 So basically I'll be stuck with the stock injectors if I'm unable to modify the ECU currently. RX-7 FC injectors are top feed, sorry I didn't specify. What about Supra non-turbo or Z31 injectors? I'm just looking to get away from the barb-style injectors and fuel rail so that I can go for bigger injectors later without having to change the fuel rail, if possible. Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted March 11, 2008 Share Posted March 11, 2008 People do use up to 370cc injectors with the stock ECU. They adjust the teeth on the AFM (I think thats it) and they also get a RRFPR to help the fuel pressure at full boost. Bastaad has a cardomain page with good info on his mods. Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 12, 2008 Author Share Posted March 12, 2008 wtf is a RRFPR? Is that an adjustable FPR? Can someone confirm that I just have to adjust the AFM teeth? Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted March 12, 2008 Share Posted March 12, 2008 Here are some threads that have helped me understand fuel delivery: http://forums.hybridz.org/showthread.php?t=100044&referrerid=14434 http://forums.hybridz.org/showthread.php?t=104545&highlight=rising+rate+fuel+pressure+regulator Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted March 12, 2008 Share Posted March 12, 2008 Oh, I just noticed you're from Marshfield, MA. I used to go to the fair there. I'm from North Falmouth. Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted March 12, 2008 Share Posted March 12, 2008 People do use up to 370cc injectors with the stock ECU. They adjust the teeth on the AFM (I think thats it) and they also get a RRFPR to help the fuel pressure at full boost. Bastaad has a cardomain page with good info on his mods. I used MkIII non turbo supra injectors on my last setup.(stockT3-Stock ECU ) They are 311CC's I didn't even adjust my afm. It was a little fat down low but I could run 15psi of boost if I turned up the fuel pressure a little. I now run 440CC mkIII supra injectors with Megasquirt and spark. Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 13, 2008 Author Share Posted March 13, 2008 What impedance are the stock L28ET injectors, they weren't listed on the sticky. I am thinking of running 295cc Supra injectors, the yellow kind. They are high impedance. I think the difference will be minimal, and I'll be able to run a fuel rail that can accept larger Denso injectors later Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted March 14, 2008 Share Posted March 14, 2008 stock injectors = low impedence Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 15, 2008 Author Share Posted March 15, 2008 Oh... so to switch from low to high impedance I would have to do...what, change the resistor(s)? Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 16, 2008 Author Share Posted March 16, 2008 .....anyone? Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted March 16, 2008 Share Posted March 16, 2008 I'm not sure. I have noticed most turbo injectors are low impedance though. Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 19, 2008 Author Share Posted March 19, 2008 anyone else? Quote Link to comment Share on other sites More sharing options...
DCZ Posted March 19, 2008 Share Posted March 19, 2008 Here's how I understand it (anyone correct me if I'm wrong). The low impedance injectors need resistors to limit the current thorough the injector coil so they don't burn up. The early z and zxs had an external resistor pack to provide this function. In '82 I think they changed the ECU so that the resistors are internal. I don't think there is a problem going from low-to-high impedance injectors because you will just have extra current limiting resistance. I don't think there would be too much resistance to energize the coil. If you have an early ecu without the internal resistors you could bypass the external resistors. However I would be careful doing this and measure the resistances involved to make sure the high impedance injectors are high enough. Hope that helps. Quote Link to comment Share on other sites More sharing options...
SATAN Posted March 22, 2008 Share Posted March 22, 2008 Couple of things here. Think of your fuel injectors like jets for a carb. If you up your jets in the carb to a huge size, its gonna flood out, This is the same with larger injectors. The ECU has no clue what size injectors it pulsing. It just knows to pulse x amount of times a second. That could be a huge difference on injectors that are twice the size of the previous ones. Also. High impedance vs. Low impedance. Its not the injector you have to worry about burning up. It is the injector drivers in the ECU. Think of it like this. You have an audio amp. It says do not run anything lower than 4 ohms impedance. It says this so you dont burn up the amp from it pushing more power than it was intended to. If you knock it down to two ohms, the amp is now flowing more juice due to the lack of impedance/resistance. The same thing holds true for injectors and ECU's. Its not the injector that can get hurt. It is your power supply/ECU. Quote Link to comment Share on other sites More sharing options...
MazterDizazter Posted March 22, 2008 Author Share Posted March 22, 2008 That makes a lot more sense. I need to check what year my engine is from. Would bypassing the external resistors work, if I have them? Quote Link to comment Share on other sites More sharing options...
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