naviathan Posted April 11, 2007 Share Posted April 11, 2007 I've been tuning the hell out of my car over the last two weeks. I started with it running lean in the upper RPMs. I've adjusted the AFM so many times I could probably map the the internals out in my sleep. But I finally got it to stop detonating above 4500rpm (result of the super lean condition). Of course it took forever to find a happy medium between idle, cruise and high RPM mixtures with the AFM (anyone have a colortune they'd be willing to sell cheap?). Now I've got that all set, but my idle seems to surge. For instance, coming to s stop light, the rpms drop, it sits a little high for about 10-15 seconds (900-1000rpm BCDD I assume). Once it drops back to 750-800 rpm it will surge randlomly dropping down as low (and this is the low) as 500rpm coming back up to 850-900 then back to 750 back to 850 down to 500/600 back up. I'm thinking she's a bit lean at idle. I might have the AFM air bypass screw out too far. Just looking for other expert oppinions. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 11, 2007 Share Posted April 11, 2007 You realize the AFM has absolutely nothing at all to do with fuel delivery above 3500rpms, right? To tune fuel delivery above 3500rpms, the only practical method is fuel pressure. Normally the methodology is to stick incrementally larger injectors in the car, and tweak the AFM spring tighter so your idle and light cruise is 'leaner' in the stock ECU, but once the cam kicks in at 3500 and starts flowing air (and the AFM is wide open by then) you go solely on the pulsewidth generated by the preprogrammed curve in the ECU combined with the larger injectors to give more fuel on the top end... Wind the spring too tightly, and indeed you set up a condition whereby the ECU gets confused signals, throw in the 35% open "Full Throttle" TPS switch and you get even more ECU confusion. For $400 and two hours of hacking, the MS will cure this Bodge-Job of Bosch Nightmare-Tronic! The idle air bypass screw will skew the AFM trace through the off-idle to 3500 rpm range. Close it further, and your 3500rpm point will change incrementally. while you richen the idle by not allowing more air to bypass, you thn move the AFM flapper to an incrementally different position at the same time... "54KPA, 700RPM, Shift-ARROW UP, ARROW UP, ARROW UP, ARROW UP Check O2 Feedback, .7V, next load block...." Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 11, 2007 Author Share Posted April 11, 2007 I'll check the fuel pressure again, but I don't believe this is the problem. Of course today I've come across another issue. I'm losing coolant somewhere and can't figure out where. There's no oil in the coolant or coolant in the oil so I can't imagine it's getting in the cylinders, but I'm not finding any evidence of leaks either. This whole car needs to be gone through and checked over. Gee it's only got 216,000+ miles on it... Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted April 11, 2007 Share Posted April 11, 2007 Tony, I thought it was true as well that the AFM doesnt do anything above 3500rpms. Although When I tested this.. I got something different. using 311CC injectors I tested the stock AFM. at wot and 13psi I was getting a nice 11.8 air/fuel, I then tightend the spring 5 teeth. and then was a nice 14's cruising and when I went WOT it was leaning out bad. I returned the afm back to stock and it runs like it did before. Nice 11.8-12.0 at WOT.. but cruising is around 13's or so. I sure cannot wait to play with MSnS.. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 11, 2007 Share Posted April 11, 2007 Like I said, if you tighten the spring too tightly, and the ECU gets funky signals and doesn't process them right. Tightening the srping RAISES the RPM whereby the ecu reverts to "preprogrammed" WOT injector pulsewidths. You experience confirms this....eventually your AFR's should have gone back to the same 11.8-12.0 when the Flap reached the 'full open' position. But if it doesn't reach that by the time the ECU reaches 3500rpm, where it's SUPPOSED to go back into open loop regardless.... See what I mean about confused ECU? There is a fine line between this tweak and that tweak, and in many cases, simply because of the way the system is designed, you can't adjust just ONE variable at a time---you end up affecting more than one because of the way the program interacts. What you need to realize is that while the flap is in play, and the O2 sensor is active (if you don't have a heated O2 sensor on the ECCS this may never happen) the O2 sensor wil ltrim another 10% out of your fuel. As long as the injectors you added did not exceed the 10% range this should occur. You can NOT adjust to 14.7 by the AFM, it has to be slightly RICH and the O2 sensor has to do the final trim or it will never work. With the size injectors you have you are supplying 15% more fuel than stock, juuuuust outside the O2 sensor's range. Did you try only two or three clicks, and make sure your O2 sensor feedback loop was being enabled? (The flashing lights under the ECU?) If the O2 sensor is not working, the ECU will default to the 'safe' program, and that only compounds the issue. If it sees rich for (I forget the number) X cycles or seconds, it reverts to the failsafe map---which isn't the greatest under boost. If you are cruising at 13's the O2 sensor is dead, try replacing it with the heated type from an 87 Z31 T and try tweaking a bit more. Those mods aren't so bad they would disable the O2 circuit, you are right on the edge of plug-n-play actually. Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 11, 2007 Author Share Posted April 11, 2007 Tony, so if I have a friend hold my engine at 3500 rpms and adjust the AFM so it hits the end point of the wipe pattern right there it should be set correctly at that point right? Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 12, 2007 Share Posted April 12, 2007 Blue's techtips page has a procedure to calibrate the AFM to factory spec, and that is what you want. if you really need the link i will post it. Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted April 12, 2007 Share Posted April 12, 2007 Very interesting!.. thanks a bunch!! Still cannot wait for MSnS lol.. Very good info here.. Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 12, 2007 Author Share Posted April 12, 2007 Yes I know all about Blue's tips for calibrating the AFM. However I wasn't exactly wanting to go through all that. Seems I'll have to though. Quote Link to comment Share on other sites More sharing options...
Clifton Posted April 12, 2007 Share Posted April 12, 2007 Tony, so if I have a friend hold my engine at 3500 rpms and adjust the AFM so it hits the end point of the wipe pattern right there it should be set correctly at that point right? It would have to be WOT, under load. You can measure the voltage when you drive. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 12, 2007 Share Posted April 12, 2007 On an N/A car it should come to 3500 and that flap should be wide open regardless of load. On a TURBO car, then, YES---then the car must be under load for the turbo to load up fully and suck the proper amount of air to "pin the flap". Like I said, the systems all interact. If you are trying to avoid work DITCH the stock system. To tweak it closely and properly is FAR MORE effort than the couple of hours needed to hack the harness and install the MS-n-S, AND TUNE IT FOR BETTER THAN STOCK DRIVABILITY! Quote Link to comment Share on other sites More sharing options...
Clifton Posted April 12, 2007 Share Posted April 12, 2007 On an N/A car it should come to 3500 and that flap should be wide open regardless of load. It would need to be wot to open the flap fully. He can't do this in the garage holding it at 3500 as he can't get wot without load for more than 1 sec if that. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 12, 2007 Share Posted April 12, 2007 Good point, yeah, WOT. I don't think it's a viable way to test it anyway. Like you mentioned, getting onto a hill, with a VOM and piercing probes in the correct wires, and going WOT in fourth gear will creep you up to the point where you can read the correct voltage. Nobody said tweaking the stock system was easy, right? LOL Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 12, 2007 Author Share Posted April 12, 2007 Good point, yeah, WOT. I don't think it's a viable way to test it anyway. Like you mentioned, getting onto a hill, with a VOM and piercing probes in the correct wires, and going WOT in fourth gear will creep you up to the point where you can read the correct voltage. Nobody said tweaking the stock system was easy, right? LOL Yes this I understand. The stock system is far from easy, but I don't have the money to keep the MS2 system I just built. It's gotta go and quick so I can pick up a couple more kits to sell. Anyone looking for one? Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 13, 2007 Author Share Posted April 13, 2007 AHHHahah.. Got it! On whim last month I bought an O2 sensor. Not sure why I just did. I checked the green led on the ecu tonight and it was solid, no matter what the car was doing. I swapped out the O2 and it's good to go! Quote Link to comment Share on other sites More sharing options...
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