fl327 Posted October 10, 2003 Share Posted October 10, 2003 High fuel pressure doesnt make you run funny, Its not unusual to see me outrageously bump up the fuel pressure when I turn up the wick for boost. Currently I run 44 psi, since Ive heard from folks that an injector cc rating is measured at 43.5 psi, while stock the car runs about 36psi Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted October 10, 2003 Share Posted October 10, 2003 Ahh...I knew I would stir the pot with my coments, sleeper that is a great E.T. at low boost but the injectors are still small for 300HP that everyone is trying to beat. Fuel pressure adjustment crack me up also, bring the fuel pressure up at idle but not at WOT on boost, wut up with that? I tune smaller injector cars on boost to 85psi fuel pressure if they need it at high boost always with good result. If you have to bring the static pressure up to make a car run right most likly you have something wrong. Think about it why would you? Do you have a cam, running a ported head anything that would add air capacity that would require a richer mixture. But to each his own and not all cars or elevations are the same so keep doing what you doing enjoy the ride and what not...... Alex C Link to comment Share on other sites More sharing options...
SleeperZ Posted October 10, 2003 Share Posted October 10, 2003 Ahh...I knew I would stir the pot with my coments' date=' sleeper that is a great E.T. at low boost but the injectors are still small for 300HP that everyone is trying to beat. Fuel pressure adjustment crack me up also, bring the fuel pressure up at idle but not at WOT on boost, wut up with that? I tune smaller injector cars on boost to 85psi fuel pressure if they need it at high boost always with good result. If you have to bring the static pressure up to make a car run right most likly you have something wrong. Think about it why would you? Do you have a cam, running a ported head anything that would add air capacity that would require a richer mixture. But to each his own and not all cars or elevations are the same so keep doing what you doing enjoy the ride and what not...... Alex C[/quote'] Why do you still say the injectors are small for 300hp? They support that at 12.0:1 a/f. And something also tells me you don't understand fuel pressure in conjunction with a sensed-air FI system - the ECU measures the air, and supplies the fuel off of an internal map. If you have non-linear fuel pressure (like an FMU ), you get varying a/f ratios across the rpm band and differing with boost. That makes less sense to me than just raising the fuel pressure to get your desired WOT a/f mixture. The 280ZXT ECU is less capable than the Z31 I use. The Z31 adjusts the cruising mixture on the fly with the O2 sensor. WOT a/f ratio tunes very elegantly with fuel pressure. Unless you need a clean idle for emissions testing (not anymore for me, but I still pass easily), who cares if the higher fuel pressure affects the idle mixture. You crack me with the comments about cams and such. You presume the "added air capacity" is not measured? Let me state this again: The Nissan ECUs measure the air, and meter the fuel. That means 1) the Nissan is not a Honda. 2) you dont need to correct the a/f mixture or change fuel pressures to "compensate" for a cam or porting. Those are measures taken by someone who runs a speed-density ECU, or someone who simply doesn't understand fuel injection. Link to comment Share on other sites More sharing options...
Garrett76Zt Posted October 10, 2003 Author Share Posted October 10, 2003 ok well back to the problem . . . I just bought some extra fuel hose, so I will run the fuel gauge up to the windshield and see what is happening with fuel pressure at WOT. It seems to me that the problem must be A/F realated since the car ran extremely rich when the problem originated. SO if the regulator is stuck open what should I be looking for at WOT as far as pressure goes? Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted October 10, 2003 Share Posted October 10, 2003 Oh Nathan maybe your right and I don't know a thing about fuel injection. But do you think fuel map corrections are not neccessary at a spacific area on the map when you add a high lift or duration cam? Or are you telling me a factory 280ZX turbo or non-turbo efi system will correct for this change? Explain how a swing door AFM knows the mass of air truly flowing threw the intake, and how does that AFM correct on a preset analog computer? As for 300hp on a stock injector, the math says it shouldn't happen not me. I'm all ears buddy let us know. Alex C Link to comment Share on other sites More sharing options...
SleeperZ Posted October 10, 2003 Share Posted October 10, 2003 That's a good idea Garrett, and that's how I knew my old pump was not providing enough flow at pressure. If the regulator is stuck open, you'll not see much fuel pressure at all. More likely it's just not responding to manifold pressure. You should see fuel pressure rise with boost, exactly 1 psi per pound of boost over your baseline pressure. Oh Nathan maybe your right and I don't know a thing about fuel injection. But do you think fuel map corrections are not neccessary at a spacific area on the map when you add a high lift or duration cam? Yes, for a factory ECU that measures the air. All that is needed is to match the mass of the air with the appropriate amount of fuel. Anything else is a bandaid. Or are you telling me a factory 280ZX turbo or non-turbo efi system will correct for this change? Explain how a swing door AFM knows the mass of air truly flowing threw the intake, and how does that AFM correct on a preset analog computer? As for 300hp on a stock injector, the math says it shouldn't happen not me. I'm all ears buddy let us know. An AFM "swing door" approximates the air flow, and with preset corrections, it is calculated to an equivalent mass. It's not very accurate, but it works to a certain degree. The Z31 unit measures air mass, and fuels dead accurately. That's exactly what I explained above. Maybe you need to re-do your math; it's the real world results that count and the math's job to explain it. There are more than 5 people on this forum that have made 300hp with stock injectors and fuel pressure, and safely, so you telling me it can't be done carries no weight. Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted October 10, 2003 Share Posted October 10, 2003 Oh OK, ya your making lots of sense.... Link to comment Share on other sites More sharing options...
awd92gsx Posted October 10, 2003 Share Posted October 10, 2003 I think what he's saying is that although bumblebee's aren't supposed to be able to fly, they do...and nobody can tell them that they can't...they don't care what the physic majors and mathmeticians say... Link to comment Share on other sites More sharing options...
Garrett76Zt Posted October 10, 2003 Author Share Posted October 10, 2003 Alright guys, Heres the results of my test run. My static fuel pressure at idle is 42 psi. with vacuum hooked up it is 32 I think. anyways, under full boost I am getting 50 psi, and the car continues to accelerate but feels like a dog. The car pulls real strong up until about 4000 rpms and then just feels flat. So what do these numbers tell me? I saw no drastic change in fuel pressure when I feel the car stop pulling. BTW I'm only running 8.5 psi boost right now Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted October 10, 2003 Share Posted October 10, 2003 Take off the kick panel on the driverside, push in the plug at WOT with your foot, see if it clears up. Probably harness gremlins. Link to comment Share on other sites More sharing options...
yo2001 Posted October 10, 2003 Share Posted October 10, 2003 A cam will effect the A/F ratio even on a MAF ECU. At least what I've seen. Specially if you are reaching 5V max before the redline. I've seen loading up on fuel after a cam swap into a JWT450 setup at idle too, I think that's got something to do with low VE on bigger cam. From my recently trap 106.6mph (carb weight 2800lb), my car made 260RHP x 15% drivetrain loss = 299HP. I did have to turn the fuel pressure up to 44psi static though. 11.8-12:1 A/R on a dyno Link to comment Share on other sites More sharing options...
SleeperZ Posted October 10, 2003 Share Posted October 10, 2003 A cam will effect the A/F ratio even on a MAF ECU. At least what I've seen. Specially if you are reaching 5V max before the redline. I've seen loading up on fuel after a cam swap into a JWT450 setup at idle too' date=' I think that's got something to do with low VE on bigger cam. From my recently trap 106.6mph (carb weight 2800lb), my car made 260RHP x 15% drivetrain loss = 299HP. I did have to turn the fuel pressure up to 44psi static though. 11.8-12:1 A/R on a dyno[/quote'] Yo, if the MAF peaks to 5V you have lost the ability to measure the air, and IMHO, that is the time to repair the MAF problem, not bandaid the the fuel system. I have run a performance cam on my Z31 setup, and it pulls like a train to fuel cut. That was low boost, about 10psi, barely over stock at sea level. I did not dyno that to see what the a/f ratio did. I intend to re-install that head this winter with my intercooled 16 psi - I will redyno, and see what my a/f ratio does. And Alex, kicking the wiring harness at WOT is a little bit risky, don't you think??? Link to comment Share on other sites More sharing options...
Guest Zcarsmakemyheadhurt Posted October 10, 2003 Share Posted October 10, 2003 Its more like pushing the connection, factory EFI still sucks. Link to comment Share on other sites More sharing options...
Garrett76Zt Posted October 10, 2003 Author Share Posted October 10, 2003 hahaha Well I took her out for another spin thinking I have nothing to lose. So I get into it and it falls on its face and I start kick . . .kicking the ECU harness and it was like Go . . .Go Gadget turbo!! THis is too funny. ANyways the connector wasn't seated all the way so now its all good. But hey I learned stuff in the process and I have a new fuel pump, filter and gauge! Now we return you to your regulary scheduled debate . . . Link to comment Share on other sites More sharing options...
awd92gsx Posted October 10, 2003 Share Posted October 10, 2003 ROFL... Glad you got it. Link to comment Share on other sites More sharing options...
SleeperZ Posted October 11, 2003 Share Posted October 11, 2003 Lol! Good one Garrett. Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 11, 2003 Share Posted October 11, 2003 Wow, my car is falling on its face during WOT and high boost as well. It ran great until I put in some older NGK's I had laying around and I fiddled with the ECU. I was convinced it needs new plugs but first thing tomorrow I am going to disconnect/reconnect the three plugs on the ECU. New NGK's are also on the way.....I hope one of these two things fixes my power starvation at WOT. By the way I put in the old NGK's because I couldn't live with the Autolites I had in there. Link to comment Share on other sites More sharing options...
fl327 Posted October 11, 2003 Share Posted October 11, 2003 Man, I tell everyone to do the ecu disconnect reconnect when they have a bug like this!!!!!!!!!!!. Good lord . It is true, a hotrodder will make things happen that math and physics says cant, why? The hotrodder will try it. Sometimes this will kick the hotrodder in the ass though, the door does swing both ways. Hey Alex- Im still looking into picking up a Haltec from you, Im in the midst of doing suspension, brakes, and a few things here and there before I get to the efi-even at 12psi, its starting to feel scary when boost hits. The starion guy I referred to you is still super interested, he lost your number so did I, please pm it to me. Factory efi can be tweaked a bit to make some power, but I dont think there is an arguement in the world that says a standalone isnt going to be faster when tuned-with similar turbo/engine setups, I would hope to think thats just logic. Cygnusx- factory ngk plug probably the best for your setup I think, Im ran them for a long time with no problem, I recently changed to a M3 plug with four electrodes, adn was running splitfires before that-both actually ran very well, but four electrodes is better than two. Lockjaw posted them and I went and got some, they are pretty expensive compared to an autolite or a ngk-but the last thing im worried about are my plugs not hitting through the mix-and thats worth it to me. Link to comment Share on other sites More sharing options...
BayAreaZT Posted October 12, 2003 Share Posted October 12, 2003 I can attest to the ECU trick. My car was falling flat at WOT and was getting progressively worse during the week. Today I cleaned the AFM and ECU connectors and now all is well . Gotta love it when it's that simple. Link to comment Share on other sites More sharing options...
cygnusx1 Posted November 18, 2003 Share Posted November 18, 2003 Just want to follow up here... Reconnected the ECU plugs and WHAM!@ Full power again all the time!! Cooooooool! Link to comment Share on other sites More sharing options...
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