Prospeeder Posted July 17, 2005 Report Share Posted July 17, 2005 what! dont laugh, i swear to god some1 named aaron or somthing on the site had a colledge degree on automotive swear to god Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 17, 2005 Report Share Posted July 17, 2005 sorry, it's just that i've seen pics of Aaron's work and it's....uh....well i probably shouldn't even go there i could be wrong but i don't think he has gone to an automotive school. if he has i would have to wonder about the school's credibility. Link to comment Share on other sites More sharing options...
Prospeeder Posted July 17, 2005 Report Share Posted July 17, 2005 ohhh, i read about that, the Z34 he sold to that one guy with fuel line problems and what not Link to comment Share on other sites More sharing options...
Aaron Posted July 17, 2005 Report Share Posted July 17, 2005 But, I guess if you welt to like 60 or higher, you could make it to where the ECU couldn't control it, but you'd also be losing high amounts of power, even if the ECU could control it. so are you saying it could control it or not? the first part of the sentence you say it couldn't and the second half you say it could. also, why would you be losing high amounts of power if the ECM could control it? because it would be running way too rich! i don't believe the ECM has that much control. not even close. The ECU can control it, to a point. Fuck there are few factory ECU's tht could control 60s, even like AMG ones. You would be losing power becuz there is an optimum, as I stated before. 70-70% of max flow is the optimum for power/drivability. Any smaller, and the ECU has to hold them open too long, meaning you still have a fuel charge in the runner when the valve closes, essentially causing the car to lean out of optimum A:F. Too big, and they open/close so fast that the fuel cannot atomize or spread evenly throughout the air charge. I am going to school for Fire Protection and Safety, not automotive. Automotive is just a hobby for me, a very expensive time consuming one too. I sold my car, the kid who bought has had a couple issues, which IMHO is expected when buying the most highly modified 3.4 out there that we know of. And I did the best I could on the swap in the time he gave me. Notice I had 3 days to do the entire swap, which includes making the custom intake arm, adapting the throttle body, getting the cables to work, re-wiring every sensor, rebuilding the back 3 plug wires, running 6 vacuum lines, etc. Link to comment Share on other sites More sharing options...
Brian P Posted July 18, 2005 Report Share Posted July 18, 2005 In a perfect world the computer could control any flow rate injector, but on a MAP based fuel management system, it's pretty far from perfect. Put, say, twin cam injectors into a 3100 and it may take a LONG time before the computer can begin to compensate. At least that's what I've determined from MY experiences. I mean the way you talk about it prospeeder there'd be no need for tuning, ever. Ben would be outta business :? Link to comment Share on other sites More sharing options...
Aaron Posted July 18, 2005 Report Share Posted July 18, 2005 In a perfect world the computer could control any flow rate injector, but on a MAP based fuel management system, it's pretty far from perfect. Put, say, twin cam injectors into a 3100 and it may take a LONG time before the computer can begin to compensate. At least that's what I've determined from MY experiences. I mean the way you talk about it prospeeder there'd be no need for tuning, ever. Ben would be outta business :? But the ECU can control any flow rate injector. But as I said above, changing the sizes will most of the time take away power, as the injectors are perfect from the factory. Larger or smaller injectors will just fuck with your idle, with no gain in performance. So they can make a car run like shit, but they are still being controlled. So basically, there is enough fuel for the A:F to be dead on, but its mixture and/or its ability to fully enter the cylinder, is compromized by the size of the injector being non-optimal. Sort of. The ECU uses maps, which are pre-determined MAP, O2, TPS, and every other sensor values. From these, it basically figures out which map to use, there are millions. But when you add headers, different cam timing, etc, the ECU can't find a map to how those affect your sensors, so it uses the closest one. Ben just creates new maps for it to use, essentially. If you put 3.4l DOHC injectors into a 3100, it will tkae the computer about 15 minutes to compensate. But, theoretically it will only take it 2 seconds. When the car is cold, the O2 does nothing. Therefore, it runs the 3.4 injectors as if they were 3100s, and assuming they won't mess with the idle (They will), it will not fix them until the car is warm enough for the O2 to start reading. Now let's assume somehow the enigne is warm enough for the O2, and the exhaust gases/manifolds are instantly up to temperature. Now it will only take the ECU 2 seconds. It will read a rich condition, and start shortening the open time of the injectors. So actually, it will compensate extremely quickly, probably under 2 seocnds, probably more like .1 seconds between the time it reads rich, to the time to cuts fuel. You say long time, becuz in reality, it needs warm up time before it can detect a rich condition. Now realize that even though it has compensated, and theoretically your A:F should be dead on, it won't be. This is becuz the injector is too big, thus causing it to not atomize evenly. Now if the fuel somehow managed to atomize perfectly (It won't, but for example), then the car should run perfect. (Depending on size, it should still idle with 3.4s, but too big and it will fuck up the idle, as the ECU simply cannot open and close it fast enough at idle). Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 18, 2005 Report Share Posted July 18, 2005 Now let's assume somehow the enigne is warm enough for the O2, and the exhaust gases/manifolds are instantly up to temperature. Now it will only take the ECU 2 seconds. It will read a rich condition, and start shortening the open time of the injectors. Aaron, what happens at WOT when the ECM ignores the O2 sensor and is in open-loop? Link to comment Share on other sites More sharing options...
Aaron Posted July 18, 2005 Report Share Posted July 18, 2005 I'm not ultra-positive on this, it is more an educated guess that makes sense...lol I'm guessin git goes to open loop to be on the safe side, as WOT is the hardest, most dangerous part of an engine's operation. So it uses currect values from other sensors to find a MAP, then runs that map to be safe. In addition, at WOT, the ECU/O2 may not be fast enough. For example, the factory dyno on my stock Z34 shows the A:F line going up and down throughout the run, not bad, but enough to take note on. If the O2 was working, and the ECU could not process and choose a map fast enough, it would exagerrate these bigtime. These would make it go really far up and down, whereas the factory line is for the most part strait. So like when the factory line is down, rich, it'd pull fuel, but by then the line has gotten to a leaner stage, now it is running too lean, and the ECU can't compensate fast enough. Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 18, 2005 Report Share Posted July 18, 2005 I'm not ultra-positive on this, it is more an educated guess that makes sense...lol I'm guessin git goes to open loop to be on the safe side, as WOT is the hardest, most dangerous part of an engine's operation. So it uses currect values from other sensors to find a MAP, then runs that map to be safe. you're right. it goes to a predermined fuel table at WOT. IOW, open loop. the ECM completely ignores the O2 sensor, so it has no way to tell if it's running too rich or too lean. it's not just to be safe. WOT operation is all about making power, NOT fuel economy and to some extent not even emissions. it doesn't need the O2 sensor at WOT. the ECM is programmed to run 'right' with stock injectors. installing larger injectors on an otherwise unmodified engine will cause the engine to run rich at WOT, becuase the computer still thinks it is controlling stock sized injectors. the ECM has no way of changing injector duty cycle at WOT since there is no oxygen feedback. In addition, at WOT, the ECU/O2 may not be fast enough. For example, the factory dyno on my stock Z34 shows the A:F line going up and down throughout the run, not bad, but enough to take note on. If the O2 was working, and the ECU could not process and choose a map fast enough, it would exagerrate these bigtime. These would make it go really far up and down, whereas the factory line is for the most part strait. So like when the factory line is down, rich, it'd pull fuel, but by then the line has gotten to a leaner stage, now it is running too lean, and the ECU can't compensate fast enough. it's really not about the ECM or O2 sensor not being 'fast enough' at WOT. like i said, WOT is about making power, so the ECM just doesn't need (or use) its input. Link to comment Share on other sites More sharing options...
Brian P Posted July 18, 2005 Report Share Posted July 18, 2005 I'm not ultra-positive on this, it is more an educated guess that makes sense...lol okay then, so regardless of what you're saying, just the fact of WOT and running in open-loop (cold) the engine will run rich, therefore you can't just toss any injectors you want in there. It doesn't matter if the ecm could control it great during other times. Link to comment Share on other sites More sharing options...
Aaron Posted July 18, 2005 Report Share Posted July 18, 2005 Like I said above, if the engine is cold, then it cannot read the new injectors until it warms up. Even though it is in open loop at wide open throttle, I would think that the time spent cruising before that, to let it warm up, it would have a chance to read the bigger injectors. Now whether or not it can adjust the A:F at WOT, without imput from the O2, based solely off of values it recorded at cruising prior to going WO, I do not know, but I assume it could do that, otherwise you can run into engine damage. Link to comment Share on other sites More sharing options...
Jcrow Posted July 18, 2005 Report Share Posted July 18, 2005 At WOT the computer modifies the injector pulse based on if it was running lean or rich before WOT. I changed from 15lb/hr to 17 lb/hr (not for performance but because they are newer and out of a '98 3100) In my expirience this is about as far as you can go that the computer will compensate (around 10%) My scan tool shows a block learn of around 100 now, when it should be around 120. IT runs good but sometimes will stall going from reverse to drive when cold, and if you idle for a long period of time in park it will give a Rich enging code. but it does run better than 250,000 mile stock injectors Link to comment Share on other sites More sharing options...
Aaron Posted July 18, 2005 Report Share Posted July 18, 2005 Yah that is what I meant by bigger injectors messing with your idle. I'm surprised it messed it up with such a minor upgrade (2#) Link to comment Share on other sites More sharing options...
biff85ta Posted July 19, 2005 Report Share Posted July 19, 2005 Ypu will run rich with a bigger injector if you do not change the injector constant in the chip or add an AFPR. The computers injector tables are based off the injsctor flow and without changing what size the injector constant is your computer will still be trying to control the stock size injector and using the WRONG info to control your bigger injectors. Link to comment Share on other sites More sharing options...
Supreme Cutlass Posted July 19, 2005 Author Report Share Posted July 19, 2005 Thank you for re-stating what three pages of comments said already.... Link to comment Share on other sites More sharing options...
biff85ta Posted July 19, 2005 Report Share Posted July 19, 2005 Thank you for re-stating what three pages of comments said already.... I just read three pages of someone saying that within reason the ecm could adjust via the O2. I just thought I would clear up the fact that it couldn't. Link to comment Share on other sites More sharing options...
Aaron Posted July 19, 2005 Report Share Posted July 19, 2005 You are right and wrong. The injector will be controlling it as if it is a smaller injector, but it will not run it rich. Once the O2 reads it running rich, it will change tables/maps to one that runs less fuel, thereby pulling fuel, using the right table to get the air/fuel right. So it won't know there is a bigger injector, it will just think that there is too much fuel, so let's add less. This is why bigger inejctors can affect idle and drivability, if they are too big or small. Link to comment Share on other sites More sharing options...
Aaron Posted July 19, 2005 Report Share Posted July 19, 2005 So the O2 is worthless? GM spent $20 a car, which adds up to billions of dollars, for nothing right? Link to comment Share on other sites More sharing options...
Supreme Cutlass Posted July 19, 2005 Author Report Share Posted July 19, 2005 Sorry, guess I didn't really read what you said. I tend to take Aaron and Turbo sedan's advice over yours, they have both obviously done more research. Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted July 19, 2005 Report Share Posted July 19, 2005 You are right and wrong. The injector will be controlling it as if it is a smaller injector, but it will not run it rich. that makes no sense the injector will try to control an injector? what? Once the O2 reads it running rich, it will change tables/maps to one that runs less fuel, thereby pulling fuel, using the right table to get the air/fuel right.So it won't know there is a bigger injector, it will just think that there is too much fuel, so let's add less. This is why bigger inejctors can affect idle and drivability, if they are too big or small. well, yeah, that's what i've been saying all along! you on the other hand have been arguing that bigger injectors would be just fine; that the ECM could simply adjust to them. to a point maybe. but again, the ECM still doesn't know if it's running too rich or too lean at WOT or any other time it is in open loop. i don't see why it's so hard for you to understand this? Link to comment Share on other sites More sharing options...
Supreme Cutlass Posted July 19, 2005 Author Report Share Posted July 19, 2005 god willing this thread will be locked soon... this has more than answered my question and now it's an arguement over misunderstandings... Link to comment Share on other sites More sharing options...
Prospeeder Posted July 19, 2005 Report Share Posted July 19, 2005 I think he means, that when the o2 is cold, it cant read, u get poor idle, and running rich, but when it does warm up, it will read the rich fuel mixture, and cut fuel Link to comment Share on other sites More sharing options...
biff85ta Posted July 19, 2005 Report Share Posted July 19, 2005 I think he means, that when the o2 is cold, it cant read, u get poor idle, and running rich, but when it does warm up, it will read the rich fuel mixture, and cut fuel To a point but nothing will be ideal without changing the injector constant in the chip. The computer will try but it may or may not be successful. If you do not want to change the ecm to compensate for your mods you really need to leave it stock. Link to comment Share on other sites More sharing options...
biff85ta Posted July 19, 2005 Report Share Posted July 19, 2005 Sorry, guess I didn't really read what you said. I tend to take Aaron and Turbo sedan's advice over yours, they have both obviously done more research. I have done plenty of research on how GM ECM's work. I may not mod my W but I have big plans for my f-body. Link to comment Share on other sites More sharing options...
Brian P Posted July 19, 2005 Report Share Posted July 19, 2005 Josh, seriously I gave up already. I suggest you do the same. This thread is like a tire fire: let it burn..... Link to comment Share on other sites More sharing options...
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