SleeperZ Posted December 12, 2003 Share Posted December 12, 2003 Bastaad525, I did quite a bit of pontificating on the subject on some of your own threads, as well as Jersey's. All I can suggest is to do a search on some previous turbo or FI threads. As it is a very important point that still seems to be missed, I'll try to make it again. If your ECU can directly measure air, screwing with the fuel pressure (as in "FMU" ) will only confuse it. This will hold true unless you have saturated (exceeded the limit) the air measuring sensor (AFM, MAF). Then you can add a RRFPR, but you will still not be able to tune it correctly, because your ECU will do some of the fueling at boost. You will have trouble with the "FMU" because it starts messing with the fuel pressure as soon as manifold pressure rises above atmospheric. The Nissan and other ECUs that measure air are straight-forward to modify for larger injectors. The AFMs can be tightened, or run in parallel (popular with MKIII Supras). The MAFs can have air bypassed. It is NEVER as simple as just "adding more fuel", that is a dangerous and un-scientific way of approaching the problem. The RRFPR is only a bandaid to get a marginal amount of power out of a system with stock injectors in a ECU that was never designed to be boosted. Can you say 'HONDA'? I'd be happy to debate this issue futher, with Alex, or anyone else. But I speak from experience. Not flaming anyone, just trying to keep it civil, professional, and free from hidden agenda. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 12, 2003 Share Posted December 12, 2003 Bastaad525' date=' I did quite a bit of pontificating on the subject on some of your own threads, as well as Jersey's. All I can suggest is to do a search on some previous turbo or FI threads. As it is a very important point that still seems to be missed, I'll try to make it again. If your ECU can directly measure air, screwing with the fuel pressure (as in "FMU" ) will only confuse it. This will hold true unless you have saturated (exceeded the limit) the air measuring sensor (AFM, MAF). Then you can add a RRFPR, but you will still not be able to tune it correctly, because your ECU will do some of the fueling at boost. You will have trouble with the "FMU" because it starts messing with the fuel pressure as soon as manifold pressure rises above atmospheric. The Nissan and other ECUs that measure air are straight-forward to modify for larger injectors. The AFMs can be tightened, or run in parallel (popular with MKIII Supras). The MAFs can have air bypassed. [b']It is NEVER as simple as just "adding more fuel"[/b], that is a dangerous and un-scientific way of approaching the problem. The RRFPR is only a bandaid to get a marginal amount of power out of a system with stock injectors in a ECU that was never designed to be boosted. Can you say 'HONDA'? I'd be happy to debate this issue futher, with Alex, or anyone else. But I speak from experience. Not flaming anyone, just trying to keep it civil, professional, and free from hidden agenda. OUCH Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 12, 2003 Share Posted December 12, 2003 Bastaad525' date=' I did quite a bit of pontificating on the subject on some of your own threads, as well as Jersey's. All I can suggest is to do a search on some previous turbo or FI threads. As it is a very important point that still seems to be missed, I'll try to make it again. If your ECU can directly measure air, screwing with the fuel pressure (as in "FMU" ) will only confuse it. This will hold true unless you have saturated (exceeded the limit) the air measuring sensor (AFM, MAF). Then you can add a RRFPR, but you will still not be able to tune it correctly, because your ECU will do some of the fueling at boost. You will have trouble with the "FMU" because it starts messing with the fuel pressure as soon as manifold pressure rises above atmospheric. The Nissan and other ECUs that measure air are straight-forward to modify for larger injectors. The AFMs can be tightened, or run in parallel (popular with MKIII Supras). The MAFs can have air bypassed. [b']It is NEVER as simple as just "adding more fuel"[/b], that is a dangerous and un-scientific way of approaching the problem. The RRFPR is only a bandaid to get a marginal amount of power out of a system with stock injectors in a ECU that was never designed to be boosted. Can you say 'HONDA'? I'd be happy to debate this issue futher, with Alex, or anyone else. But I speak from experience. Not flaming anyone, just trying to keep it civil, professional, and free from hidden agenda. OUCH All good points. Adjusting the afm is a proven method. If you don't want to mess with the afm then cut your bellows and install a piece of 3" pipe (on turbo side of afm) with a 1/2 inch o.d. elbow out the top with the outlet parallel to the bellows. Run the pipe out the front of the rad and install a filter on it. You are now tuned for 370's. You can mess with the timing if you want. Can't get much easier than that. And you should be able to find 370's for MUCH less than 200 bux. I think I paid 10 ea. for mine. That said I don't know how much power you could support with a fmu. With 370's you're good to about 370 hp or so at the stock fuel pressure. You could go quite a bit higher with a programmed eprom and higher base fuel pressure. What kind of fuel pressure would it take to support 370 hp with the 260cc injectors? Quote Link to comment Share on other sites More sharing options...
Jersey Posted December 12, 2003 Share Posted December 12, 2003 Probably enough pressure to blow the stocker 260cc'rs apart Bernard. LOL. Why waste $ on a bandaid and limit yourself with the 260's when you can just about the same exact $ and have much more room to increase power? I must be missing something here. Maybe that the FMU item is a lot less work to install than to install injectors and making a/f adjustments via a/f meter and other options? I guess bolt-on applications are the way of today. It was an easy decision for me when it was my turn at the build - Aprrox $90 for 6 370's and another $110 for the Warlboro pump, which gives me room to grow - Total=$200 Leaving the stock, old, half worn pump (no charge) and $200 for an FMU type unit, which will limit me shortly when i go T3/T4 and will possibly cause the stock 260's to spray erractically - Total=$200 Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 12, 2003 Share Posted December 12, 2003 Either way you need a fuel pump. Mine wouldn't even support what the stock injectors could push. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted December 13, 2003 Share Posted December 13, 2003 Making a factory fuel map isn't a good idea anyhow IMO. FMU nor larger injectors. With FMU, you get the partial throttle driving way too rich and with larger injectors on MAF system, your timing gets wacked because you are making the ECU to think it's getting less air. So thec orrect way to to Eprom it I guess. No offense. Quote Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted December 13, 2003 Share Posted December 13, 2003 No E-proms for L28 electornics so throw that out the window. Sleeper how the hell do you think the factory swing door AFM is gonna directly meter incoming air? Have you taken a close look at the factory L28 AFM? No hot wire like modern day AFM found on Z31 ECU's. So your nuts if you think the factory ECM is gonna correct the fuel ratio or it can trully be adjusted. You guys give the factory ECM way too much credit. At the most you can slightly slow down the injecton time at idle and possibly control the slop of enrichment, once the AFM is fully open you have the same injection time with a larger injectors as the originals. It is all pre-mapped in the computer for a T3 at 6.5lb of boost on a 260cc factory injectors to make 180hp with a very safe ignition advance. The FMU only brings up fuel pressure when boosting, so part throttle will be barley effected if you know how to tune a FMU. This stuff is old deal with it. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 If your ECU can directly measure air, screwing with the fuel pressure (as in "FMU" ) will only confuse it. This will hold true unless you have saturated (exceeded the limit) the air measuring sensor (AFM, MAF). See that's where I"m misunderstanding... from what I understand, this IS the case... running 10psi, WOT, isn't the AFM way past being maxed out? THAT's why I keep thinking I need something like an RRFPR, because my understanding is that the AFM was NEVER designed to measure THIS MUCH air... heck some people here are conviced that even at stock boost the AFM flap is fully open at WOT by 4000rpm. I dont particularly believe that, but I do know Nissan designed a lot of parts on these cars to be pretty much at the limit at the stock level... very little room for improvement or upgrade, and when you suddenly turn up boost, and add better intake and exhaust, you're suddenly now flowing way more air than this particular system was designed to measure accurately. In a case like that it would seem that bigger injectors mated to the stock EFI is just as much a bandaid... you're still 'tricking' the ECU and making it supply more fuel than it thinks it is. Adjusting the AFM is a tricky thing... this much I have learned for myself... while I'm sure it may work okay to get the car running well, I dont see it giving me any more of a perfect mixture across the board than using an RRFPR... I tried that method with my built up, high CR N/A motor and it was a compromise... I could get it rich enough on the top end not to ping, but I couldn't get it to run right at ALL RPMS and ALL driving conditions (by right I mean close to stoich). When I later added an adjustable FPR, I got much the same result... I was only able to adjust the fuel mixture as a whole, and not compensate for rich or lean 'spots'. Wouldn't I get roughly the same results with bigger injectors and tweaking the AFM? Can anyone tell me with a 100% exactly when or how much air the stock AFM can measure before it becomes maxed out? Then you can add a RRFPR' date=' but you will still not be able to tune it correctly, because your ECU will do some of the fueling at boost. You will have trouble with the "FMU" because it starts messing with the fuel pressure as soon as manifold pressure rises above atmospheric. [/quote'] This statement is untrue in the case of the Cartech unit, I dont know how it applies to other RRFPR's. The cartech unit has settings for both rate of gain and onset of gain... in other words, it allows you to set the point that you want it to start affecting the fuel pressure. For example, you can set it to have ABSOLUTELY NO EFFECT on fuel pressure until the boost pressure in the manifold reaches 7psi... so all the way up to stock boost, the FMU is doing nothing, and above stock boost, it starts to add extra fuel. This was how I intended to set it up. You can also adjust how much extra fuel it adds, as a ratio of psi of fuel to psi of boost. I read that it can be adjusted to add from 2:1 all the way up to 12:1... that's a lot of flexibility. Jersey - I agree with you on a big point... if it were in the plans for me to do some really big upgrades, better turbo or whatever, then yes, there would be no getting around needing bigger injectors. There isn't much flexibility or room to grow with the stockers, RRFPR or not, I dont' dispute that at all. But I'll say again... my goal all along has been to only go so far as a mostly stock EFI could carry me... I've always had a HP goal of about 240-250hp at the wheels, can safely run about 13psi (I dont want to tax the turbo any further than that) and a car that could run low 13's in the 1/4. I know I can get there with stock injectors, and I know I can get there with stock EFI. Whether or not at this point the stock injectors become erratic or are operating at their maximum duty cycle is beyond me... but from everything I've read this is the number that keeps coming up as the limit, so I assume this means the limit at which they will perform well? The question is do I NEED to augment the stock fuel system with stuff like RRFPR or better fuel pump to get there... apparently the fuel pump is hands down yes, but other items are debated... it's pretty confusing!!! Okay... I'm back off the idea of getting the RRFPR for now... I need to learn more about this whole thing... I just want to make the right choices here, in what paths I take to get more, safe power... but I also want to save as much $$$ as possible, and have the ability to tune it when it's done, and w/o being too damn mickey mouse I've always relied on you guys to point me in the right direction... so get to pointing! Quote Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted December 13, 2003 Share Posted December 13, 2003 Very well said. I wouldn't enrich anything at 13psi and if your car runs correctly it will make perfectly good power there. I guess I am saying thats how far I would push a stock EFI system. A FMU is easy to install cheap and if you use it correctly very effective. I tune cars to no more than 70-85 psi of fuel pressure between 18-23psi of boost on FMU's. Not all cars are the same but generally your gonna be good right about there. Like SleeperZ said, I do sell these things and you I don't mind helping. Good luck, I'm out of this topic! Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 13, 2003 Share Posted December 13, 2003 No E-proms for L28 electornics so throw that out the window. My l28et ecu has 3 eproms. 2 for main code and 1 for Ram. It uses the same processor as the z31 ecu's. Easily programmable if one was inclined to do it. Sleeper how the hell do you think the factory swing door AFM is gonna directly meter incoming air? Have you taken a close look at the factory L28 AFM? No hot wire like modern day AFM found on Z31 ECU's. So your nuts if you think the factory ECM is gonna correct the fuel ratio or it can trully be adjusted Airflow is calculated by voltages changing by arm moving across the tracks inside the afm. That together with air temp sensor is used to calculate air mass. And lastly rpm is thrown in to calculate load to output injection pulse and timing. Same idea done in a more crude way as the z31 ecu's. If you want to change your acceleration enrichment you need to figure out where the arm is at the load poiint you wish to adjust and solder in a potentiometer in place of the resisters on that track. With leads long enough to go into the car you can do it on the fly. Btw you could do this across the entire afm range. And I think Sleeper is nuts too. At the most you can slightly slow down the injecton time at idle and possibly control the slop of enrichment, once the AFM is fully open you have the same injection time with a larger injectors as the originals You can't adjust idle much at all as far as pw goes. The saving thing is they are usually set so lean to begin with you merely have to adjust the idle bypass a little and that's it. Adjustments on the afm spring on a dyno and you would have a pretty good fuel curve. You're right about the injection time. This is not the optimal setup but I think it's good for someone looking for more power and leaves a lot of growing room. I never tried a fmu so I can't honestly say how good it would work. It would seem to work as the stock ecu doesn't take afm reading into acount after about 4-4.2k. And it would be much easier to install the fmu then to change the injectors and tune it. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 Okay so now I guess we are all agreed that I DONT need the FMU. If the stock fuel system will be sufficient up to 13psi w/o it... that's good news to me . Sounds like I really need to prioritize getting a better fuel pump above everything else. Sleeper - I know we have gone back and forth over this a couple times before in some threads of mine... I just always ended up leaving those threads just about as confused and unsure as when I originally posted them. So I posted the question again. When I have the $200 in hand it's really hard to decide what to put that money into.... usually you guys are a great help with that stuff, but in this case of the RRFPR there is so much debate and all of the arguments seem just as valid... sorry that I keep getting you to repeat stuff you've already said... not trying to be a pest just trying to understand, which I still really do not. I find I try to just reference other peoples setups for the answer here, and there are quite a few people running this type of unit on their turbo cars... it makes a good case for getting one myself. But then again... there are lots of ricers putting rear wings on their front wheel drive cars so... that's why I keep asking. I will say this... I had NO idea injectors could be picked up so cheaply, and now that has once again become a valid option that I will definately move up on my list and keep in mind. And with that, I may lean back towards getting the HKS AFC thing, to help adjust them properly... I'd rather do that than start messing with the AFM, and from what you're telling me I can do this whole setup for not much more than the FMU would have cost. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 I never tried a fmu so I can't honestly say how good it would work. It would seem to work as the stock ecu doesn't take afm reading into acount after about 4-4.2k. there it is again... I really wish we could get someone that knows w/o a shadow of a doubt to clarify exactly how broad of a spectrum of airflow the AFM is capable of measuring. And it would be much easier to install the fmu then to change the injectors and tune it. that's what I'M trying to say!!! It seems like it would be MUCH more of a PITA to me to install bigger injectors and try to get the car running right by tweaking the AFM. Maybe the costs are much closer than I originally thought, but the labor seems like it would be much less... and again... for the power level I'm shooting for the 370's seem like they would be overkill. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted December 13, 2003 Share Posted December 13, 2003 Why don't you just turn the static fuel pressure up and tighten the AFM some? that's keep the fuel delivery linear. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 13, 2003 Share Posted December 13, 2003 I was considering that as another viable option as well... that'd be the cheapest, best-of-both-worlds solution... that's why I mentioned I may just fall back on getting the MSD adjustable unit for $50. I had also mentioned that as a possible way of taking better advantage of a unit like the HKS AFR... turn up the pressure a little bit to keep it rich on the top end, then use the AFR to tune leaner at idle and low rpm. So many choices!!!! I have one side-question. Are the N/A ZX and ZXT stock FPR's identical? I know physically they appear so. I called auto zone recently, and they only have one listed universally, no difference between turbo and N/A. I would think they're not the same thing..... Quote Link to comment Share on other sites More sharing options...
Jersey Posted December 13, 2003 Share Posted December 13, 2003 I think they are the same 525 but not 100% sure. There was a post here not to long ago about that. This is my opinion on this whole FMU/larger injector topic - I'm not rich so, i think why spend hard earned cash on something that you'll be pulling out and placing on the shelf after one of your soon upgrades (because you know boost is addictive and once we go fast, we just want to be faster - my case anyway) when you can spend just about the same amount of $, have your Z run decent after a few adjustments and not have to remove this item for waste for a longer period of time? I guess if you sell items as these, it's a great way of making $. Gets the customer to come back sooner to buy more stuff. Me, i try to spend my "extra" cash on something that wont be useless after one of my next upgrades and that i know that can be incorperated into the performace stage that my Z is currecntly in. I guess if you're set in your mind that a certain HP is going to be exactly what you want forever, buying all the items that can take you exactly to that point and no further, items such as an $200 FMU, is for you. Me, 12.8 isn't cutting it. I'm not sure 12.5 or 12.2 will either if i'm ever as fast as some of you but i do know that my 370's wont restrict me from reaching those #'s, as i know the 260's would. Just my opinions. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 13, 2003 Share Posted December 13, 2003 Well said Jersey, I feel the same way. Why spend $200 for something you have to throw out when (not if) you want to make more power. I try to put my money into parts that can support more power than I need at the moment, so I get at least 1 season of use out of them. And one might think that "all you have to do is install an FMU" to make more power is mistaken. There is tuning involved, and you'd better do it on a dyno, because that motor's going bye bye if it's not adjusted right. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 14, 2003 Share Posted December 14, 2003 Jersey - again I do agree. Unfortunately that 250hp # is something I do need to stick with, it was a goal I set before the project started. Not to sound like a wuss, but it really comes down to my 'significant other', whom I have promised that a) this car would not be an endless money pit, with the constant unending need to spend more $$$ to go faster and faster... so I sat down, outlined a goal, and what it would take to get me there, and set a loose budget with a proposed maximum limit, and promised to stick with it. as much as part of me would love to have the fastest car on earth, I do believe there is a limit to what I need or what I would actually ever get to use. I dont really ever go to the track, and I'm TRYING very hard to avoid racing on the streets in any way shape or form... I dont really need a 12 second car. Another 'sub-goal' I've set is to have the car be just powerful enough where traction on regular street tires begins to be a problem... to me this is an 'optimal' level of power, and another limit I've really imposed on this whole thing. To be honest the car already feels plenty fast for me... the last few mods I intend to do (intercooler, fuel pump) are more for safetly and reliabilty then solely for the intention of getting faster (though it's a nice side effect), and then I will move on to doing a few thigns to get it handling and stopping better (also as much for safety as anything else). The car is already fast enough to be somewhat scary for me and very scary to everyone I've given a ride in it so far! I dont need a 12 second machine.... and to be honest, even after enjoying the boost for a while.... I really dont WANT one. Sleeper - I think we've posted 'back and forth' enough by now for you to know me a little better... I know there would be absolutely no point in installing an FMU or any part that effects how the engine runs in that way, w/o immediately taking it to a dyno for proper tuning afterwards. Not only do I know that there's no way to just install it and have it make extra power, I really dont think the thing will give me any extra power at all, period! Again... I hadn't intended on installing it for that reason, rather, I am just looking into ways of increasing the safety margin when running this car hard, in this case, keeping it from running lean. Anyways I posted a lot of specific stuff to you a few posts up.... and was really hoping for some specific replies from you on those things. I think this is part of the reason I repost questions now and again... many times so many questions that I ask (and admittedly I do ask quite a lot!) get completely skipped over. With this topic though more than many others I really want to 'get to the bottom of it' and get some definate facts set right in my own head so I know and understand, w/o any doubt, just why this mod or that is not right for me. You've always been one of my BEST sources of info on these boards... dont get lazy on me now! Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 14, 2003 Share Posted December 14, 2003 I was considering that as another viable option as well... that'd be the cheapest' date=' best-of-both-worlds solution... that's why I mentioned I may just fall back on getting the MSD adjustable unit for $50. I had also mentioned that as a possible way of taking better advantage of a unit like the HKS AFR... turn up the pressure a little bit to keep it rich on the top end, then use the AFR to tune leaner at idle and low rpm. So many choices!!!! I have one side-question. Are the N/A ZX and ZXT stock FPR's identical? I know physically they appear so. I called auto zone recently, and they only have one listed universally, no difference between turbo and N/A. I would think they're not the same thing.....[/quote'] Here's the thing about the L28ET, IMHO. It was built well, including the ECU. It also has an extremely low CR. It is hard to hurt provided you run a sane air/fuel mixture, and intercool it. Factory fuel pressure, factory ECU, factory injectors will be safe. I've run mid-13s with that, no fancy fuel pressure regulator, just intercooled with a good pump. In my opinion, you don't need "more fuel". And the Z FPRs are all the same, turbo and n/a. Why not? The injectors are all rated for 37 psi, that's all it has to do. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 14, 2003 Share Posted December 14, 2003 Sleeper - I would have thought the (stock) turbo fpr would be different than the N/A one if only because the N/a one would never see boost, so maybe it wouldn't be designed as 'flexible' with as much range as the turbo one. Whether I get an adjustable, rising rate, or whatever, one thing is for certain, I do NOT trust the stock one that is on there right now... I have no way of knowing how old it is or how well it is functioning, but I DO know that the car still is not running perfectly, and I've eliminated/tested/replaced almost every other component of the fuel system... so I'm just going thru replacing as much as I can feasibly so I know where I stand with all the components of the EFI. Again I am leaning back away from the RRFPR since pretty much everyoen seems to agree I wont need it (though for different reasons)... and now just trying to decide if I should just replace stock with stock, or at the least get that low cost MSD adjustable unit with boost reference ($50). I dont know how much a stock unit costs to compare... I'll check around and see where I can get one today. Also... I'm just curious, how much boost were you running on that mostly stock setup to get mid 13's? And given the lower times of other guys like Jersey (low 13's-high 12's) with very similiar (mostly stock) setups, what do you feel was limiting your setup at that point? To run a mid 13 has been another part of my written goal of what I want my car to be able to achieve when I'm done with it. LORD I need my I/C installed.... Quote Link to comment Share on other sites More sharing options...
Jersey Posted December 14, 2003 Share Posted December 14, 2003 I was leaning at low 13's, high 12's. Bring that darn IC over here 525, i'll install it for ya! Quote Link to comment Share on other sites More sharing options...
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