superlen

Thanks, The time it takes to bog may be a red herring, but I would be interested if you can detect anything. The FI filter is much more fine than a carb version of course, so it may not take much to cause issues. Hopefully that will cure a majority of it. Zeds idea is good and would be useful, a bit scary perhaps. ? Len

Steve, Can you tell when you lose power, does it happen rather fast right after you encounter a load, or is it delayed a bit? My thinking is that if the problem is the ECU map then the lean condition might be fairly quick & responsive. However, if it's the filter then it may take a bit for the filter and associated fuel rails to lose pressure. Fast and slow here are relative terms or course, and this is just conjecture on that one problem would behave opposite the other. If I had to guess, I would say that the fueling tables are just a bit off, but I do think you are on the right debug path with changing the filter first. The filter is easy to change and could quickly rule it out as culprit or contributing factor. Sorry, I'm not familiar with the GM fi operation so I'm not much help there. I would definitely datalog the AFR if possible. You lose power faster when you fall off 14.7 in the lean direction, but the same thing happens on the rich side too (just have to be farther away). It's possible your tables are too rich under load. If possible, switch off the car right after the event and check the plugs. Any backfires under load? Len

Chas, Thanks for asking. Yes, it's been since my daughter was born. I had forgot just how fun little ones are and how much your world revolves around them. Everything is going well. Busy, as usual. My oldest child (27) just got married, and my youngest (5) just started kindergarten. Looking forward to finishing up the HellFire & related projects now. I miss working on the Z. Len

Steve, I figured out what/who (I hadn't checked my pm box in 4yrs) & have emailed them . Apologies in the open forum for my lapse in returning the part, remedies in the works. Len

Steve, I just saw this post and wanted to clarify/or ask what parts you are referring to? I'm not aware of borrowing any parts and not returning.... If so, and I owe somebody something, please let me know so I can correct this. I know I loaned out some known working stock ECUs to a few people so they could verify if theirs was good/bad so I do recall some items being shipped around, but don't remember have a loaner of someone elses. Do you know what the part was? Was this something of yours? Len

Hello all!! As some will remember, I was working on a drop in replacement ECU for our Z's & had to take a hiatus when my daughter was born. This week she started kindergarten (my how time flies when you have young ones underfoot). Last month I began un-mothballing the project and gearing up to finish. Apologies of course for the delay, but rest assured I haven't forgot about this. The status when I paused was this: 1 - The prototype board came up nicely and I was driving my car around using 100% stock L-Jet components (save for the HellFire ECU of course)....poorly tuned at best & no enrichment code was in place which caused some stumbling when I floored it. This was expected & I didn't care, I was all smiles that it worked as well as it did. 2 - The primary GUI functionality is present, but has a *LOT* of debug screens and added test buttons here and there. It's quite cluttered as I continue to test/debug, but will be getting cleaned up as I progress. The GUI does look good and I'm mostly happy with the interface. Still quite a bit of legwork to make this clean and presentable. The communication with the ECU has been rock solid & realtime data is sent continuously to the pc to see while the engine is running. Firmware update via the Laptop needs to be finished. 3 - 20 ECU boards are assembled & just need programming to production firmware. 4 - Sensors (Primarily the pain the arse AFM) still need to be calibrated & the tables loaded with qualified data. Currently I have data that is *close* but can be better. I built a flow bench to calibrate the AFMS. I have about 20 or so AFMs from various years to play with. It will be interesting to see how they have aged. I'm guessing poorly. ? The flowbench still needs some attention & will be the first on the list to work on. 5 - I need to qualify/test the stock injectors to characterize their average opening time and flow rates. I have some stock numbers in the tables now that work, but they can be improved. 6 - Various tuning tables need to be added, (acceleration, cold start, other enrichments) 7 - Then I need to tune it of course to the stock engine. I have one bone stock 77 engine and another that is bone stock plus the addition of a mild cam. I have a wideband O2 on the engine that I will use to assist with tuning. I keep wanting to build a dyno as well, but sanity so far has kept me from running down that rabbit hole. It feels good to be back on the project & I'm excited to make some headway. I'll post some progress pics on the flowbench and AFM results when they are available, and feel free to pester, prod, poke, or ask questions about the project. Len Here's a link to the last thread:

Chickenman, Thanks for the info..good stuff. I knew many of the systems blended or switched between MAF/MAP/Alpha but didn't know any of the details on the specifics. My only experience with Alpha N is on my bike. It's a Victory Vegas and the signal coming off it's MAP was quite crazy at times. The stock ECU only uses it to sample BARO at startup is my understanding. The fueling system on it is completely Alpha-N from that point on. I have a MAF from an Infinity Q45 to play with on HellFire but I haven't tested it yet. I'm going to plumb it ahead of the AFM for an interesting test as I should be able to read both signals and correlate airflow/IAT and massflow. I'm a bit wonderous about how the intake routing will affect the signals. I Len

8300 RPM assuming 78% VE at that rpm. Also, I want to revise my last thought on maxing out at top speed, its not the VE tanking at top speed, its just sheer power not enough to combat the wind resistance and power requirements to go faster. It *could* be the VE tanking if you had a really really crappy intake manifold design with too small of runners, then the VE would fall dramatically at the higher RPMS. However, you're typical cars intake is of course sized properly, which is good. We don't want it to be the deciding factor. Len

I'll keep you guys posted if I make it out this summer. HellFire is back up on the stack of projects so you should see some status updates on the project thread soon. Len

S, I'm trying to follow what you typed....(not your description, my weak mind) What you are describing is a drop in the VE (volumetric efficiency) of the engine due to intake manifold design (lets say a really poor one), and yes if the VE tanked while you still had the same amount of fuel being sprayed you would begin to richen up. However, in practice, I don't think you can get there. The reason is the feedback. The power source causing the increased RPMS is derived from the air flow. If your VE (and thus your airflow) tanks then your power delivered drops and the RPMS then drop accordingly which raises back up your VE. If your VE went totally to zero, NO air would flow and 0 rpms would result. Now that I think about it, I'm pretty sure this is exactly what happens when you just run out of power at top end during a race or snappy visit to the supermaket, the engine simply can't breathe anymore air due to shrinking VE -> which creates less power -> decreases RPMS -> raises VE back up -> raises RPMS...rinse repeat. As for the injector overlay, I don't remember the number offhand, but I'll run the HellFire GUI in the morning at work and take a screen snapshot for you. I have a simulator in there that shows the injector pulse width and where things break down. With the stock 180cc injectors & two sprays per cycle, I seem to recall around 9000rpm as the theoretical limit before overlap. Some degree of fudging is in that as I don't have an accurate VE map for the stock intake/cam/head. Depending on what state I left the GUI in, I can email you a copy so you can play with the simulator as well. Ping me on my HF email if you are interested in that. Len

MIke, There is a chance I will be in NM/CO this summer. If I do & you still have issues, we'll try to schedule a time to get together. For that matter even if it's fixed and schedules work out, I wouldn't mind meeting another Z'er. I'm still unsure about my travel plans. Len

Just checking in to say I'm still alive. Still not a lot of progress on HellFire, but I'm seeing a little bit more shop time around the corner. Len

It sounds like you've covered a lot of bases. I think I'd drop back to dead simple basics for your MPG issue. 1. Check compression 2. Adjust/check the valves 3. Timing, ignition (new plugs) 4. Gearbox/rearend oil (mine was installed my Moses ) 5. bearings/wheel drag After that, then go back to fuel delivery issues. The high RPM problem you mentioned i don't think is related, but sounds ECUish or maybe AFM. I don't remember if it was mostly rpm related or load related. Load related points to AFM. RPM regardless of load is an ECU issue, Also, really triple check your ignition. The ECU gets it's primary fire signal from the flyback on the positive side of the coil. It's possible that this signal is breaking up at the higher RPM & confusing the ECU (it could miss a pulse and go lean, or see multiple pulses and go rich). Note: the coil could still fire the plugs normally, but the flyback through the primary and what ultimately shows up at the ECU input could be funky. A quick check would be to try a new coil and/or ignition module. Even new plugs might fix this if thats the problem. Note: I wouldn't normally think this as a possible solution, but when you try the normal culprits and it's still broke, we get creative. Len

Hi everyone! Excellent discussion by all. I think everyone ended up on the same page, but I'll throw in my notes from a quick read through. 1. The 4500 is "arbitrary" in that it just happens to be where the AFM Vane maxes out with a stock Z engine. By maxs out, we mean any more airflow does not move the vane (& the corresponding voltage read by ecu) any appreiable amount. 2. The ECU does not stretch the pulse ANY based on RPM value. Don't confuse this with more fuel delivered with more rpms. That happens because you get two squirts/cycle...more cycles, more squirts, more fuel, not because the ECU reads rpm and decides we need more fuel. I think we all know, but I'll reiterate there aren't any tables in the stock ECU, it's done with multi-stable vibrators, comparators, & op amps. There is zero circuitry in the ECU to modify pulse width based on RPM. 3. If the load (read airflow) continues to increase, after the AFM has maxed out, a stock Z will begin to lean. 4. Read #3 again. At first It seems wrong or counter intuitive, but that is the way the ECU operates. Actually many ECUs do this regardless of what load sensing device (LSD) they use. If the LSD runs out of headroom, the ECU pulse width stops increasing. Remember LOAD drives fuel required, not rpms, 5. WTH, that can't be right. This sounds like a bad scenario. What gives? Well, the short answer is we don't care. Why? because the overall fuel system is designed to do this at the theoretical max our engine can perform. Its at the extreme top end of load so we don't need to measure any more than that. You may worry that leaning out at Full load is really *bad* and it is....well kinda. Being LEAN (AFR above 14.7) at full load is VERY VERY bad. Leaning out at full load (meaning the AFR in increasing due to stalled pulse width - NOT really a lean condition), is not bad. Fuel delivery systems are design to run a lower AFR at full load/WOT by default. Our Z's are no different. Digital ECUs do this with tables and our ECU does it with the transfer function of AFM vane position vs. pulse width and a WOT input as a kicker. So when our AFM Vane maxes out, we are probably at 10-12:1 AFM. If we continue to draw more air (we've robbed a beer truck and are fleeing from the local POPO), the AFM Vane doesn't increase any more, the ECU doesn't strech the pulse any more, and the AFR begins to go leaner, 10.5, 10.6. 11, 11.1, 12.1, 12.4, 13, 13.1, 13.2, 13.2, 13.2. (Actual numbers will vary of course depending on your AFM setting/engine combo) What saves us is the system is designed so we can't get into that 15,16,17:1 ratio at full load. I haven't measured the Zs AFR at this condition, but I would guess that 10:1 isnt too far out of line as the target starting point. It is desirable to run a fully loaded engine rich for a few reasons. First, the farther away from the lean kaboom condition, the better insurance you have against murphy's law. Second, excess fuel being dumped into the engine will help cool the combustion chamber. The only determinent is that you lose a *tad* bit of power, but not much & not worth the risk. Even the latest/greatest ECUs with the best sensors around won't try to run the engine near 14.7 at full load. Perhaps, in some race engines. 6. The stock AFM measures out on the flow bench to handle about 190hp before maxing out so more than enough to operate the stock Z. Take this number for now with a grain of salt as I'm not sure what constitues a stock AFM. I have 20 or so AFMs and they are all different. Rob, you can take it verbatum, as I did the math when your AFM was on the bench. One thing to note however is that it's not *too* much greater than stock. This is the reason that when you add a cam and headers, the stock system starts acting up. You now can max the AFM easier and the ECU doesn't have any way to know this. Typical fixes have been larger injectors, tweaking the clockspring, or rising rate regulators, but all of these fall down in particular areas. The Stock ECU was great for the stock system, it just isn't very forgiving of changes. The ability to make it robust enough to handle unknown conditions just doesn't exist in its analog circuitry. 7. I don't remember who mentioned it, but a minor point is that Speed Density systems (using a MAP sensor) do NOT work well with radically cammed engine. The valve overlap makes a really nasty manifold pressure signal, its' not a lot of vacuum, it's fluctuating all over the space, & there are multiple resonances happening. All of this makes the MAP signal a bit annoying/impossible to use, also MAF sensors in these conditions can also suffer some of the same problems as the pulsing waves cause some airflow inversions in the intake track. In these cases, designers fall back to Alpha-N (TPS), or a combination of Alpha-N and MAF. A correctly tuned Alpha-N will work great with an engine, but it takes a bit of tuning to get it set up. In theory, the throttle response of an Alpha-N will be a bit better than AFM, MAP, or MAF. In practice, I think it's a moot point as engines that need to use Alpha-N are already pretty responsive as they are gulping air at idle & ready to take off when you crack the throttle. Well, that's all for now. Again, this is a great thread on the AFM. It's a pretty misunderstood, yet critical piece of our cars. Len

Haha... Thanks Captain! Yes, you see my marketing ploy now, never give the year!!! Len

Hi all, just a quick update. My daughter just turned 10 months old a few days ago. Holly cow, time flies! I was out in the shop this weekend moving stuff around so I can try to get back to work on AFM and HellFire calibration. Wish I was further along. I haven't been loggin in much lately, so ping my email if you have any questions that are time sensitive rather than pm. Chastising and harrasment are welcome. Len

Oh, I forgot to add that an quicker way to reach me instead of PMS (I've not been checking in that often) is to hit me at superlen*hellfireproducts.com. The webpage is just a hello world, but the email is all functional. Len

Time for an update & some pics. Don't get too excited, I'm still mucking about with the AFM and flow bench pulling some numbers, but it's somewhat interesting so here are the pics. The first is my 3d printer making an adapter/bushing for the Infinity Q45 MAF Sensor. These are $30 new from Ebay and I think will be handy two ways. 1. As a research tool, it's another sanity check on calibration of the AFM. My flowbench gives a number, this MAF gives a number, and the AFM gives a number. In theory, they should all agree. That's what I'm studying currently. 2. In production, it would make a good choice for an aftermarket MAF if someone doesn't want to pay to get their AFM rebuilt or buy a new one. This MAF is cheap and easy to secure and the HellFire will ship with the calibration already in place for this model. You can of course use any MAF you drag up from anywhere, but this one would be a drop in. The second pic is of the flow bench test setup. You can see the AFM (it's actually Bob's, he make recognize it & I left out the copy of today's paper as I'm sure he thinks I have it kidnapped. ) at the start of the airflow then onto the Infinity MAF using the adapter I printed, then down into the flow bench. Inside the flow bench is a calibrated orifice that I measure pressure drop across. All of the measurements of course are done with the HellFire board itself. The user calibration feature of the GUI makes it easy for me to drop in any kind of sensor and just type some numbers into a spreadsheet to scale/calibrate it. The MAF is read directly on the channel that in the stock world is the AFM reference signal as we don't use/need that reference. To measure the PSI drop across my flowbench orifice I had to scab on another differential pressure sensor and blue wire it's output to the EGO monitor. Now, I just need to find some more time to measure/test/measure/test...ect. Len

Hi All, Sorry for the slow/non-existant updates. I've been playing with the new baby & friend/family projects have been needing my attention when I did have some free time this summer. I had seriously forgotten how much time a cute baby can occupy. Of course, my older boys have been blowing engines, & 4 wheeling in the creek...with the car! It seems to never stop. I've been slack on HellFire progress, but it's still on like Donkey Kong. I have 10 prototypes built up and ready to send out once I get some code finished up. (primarily bootloader code and AFM calibration numbers). Capt. O and I did some brainstorming on the phone a few days ago on a good plan to get an accurate picture of the AFM. I just need to get my test setup wired up and run some more numbers. Look for some good data within 2 weeks. If not, start blowing up my email/PM on why I'm loafing. Len Len

10-4.

Captain, Bob's definitely got a spring loose. However, his AFM offset is primarily because the wiper is mechanically shifted on the carbon track so even at rest it can't show a small enough airflow to the ECU, so the ECU then meters too much fuel (particularly at idle). I see this in the data, I see it fuel my car poorly at idle (rich of course), and Bob (rcb280z) was reporting the same thing. The curve on the AFM actually isn't too far off. He did some spring adjusting and got it really close in the upper RPMS by of course loosening his spring (way to go Bob), but with that offset, there would have been no way to get it back perfect. Idle is where the problem is. He would have failed smog with this one for sure! As for knowing what "normal" looks like. I'm not there yet, & I'm still kinda going in circles, but the circles are getting smaller. Once I play with my flowbench some more and begin to trust it's numbers, I'll bring in a factory calibrated unit and check my work. I have a buddy with an "in" at Oreilys and he can get me one to play with for a few hours without actually have to BUY a new one. I'll only need it for 30 mins. I hate to just buy one to confirm what I already know....in theory. Len

Undefined, What you called the transistor unit is in fact the ECU. (Drivers side kickplate) What Datsun calls the ignition module, but is could be called the transistor module, is much smaller and is tucked up under/behind the glove compartment. If you have spark when it's not firing, you can ignore it and focus on the fuel delivery side of the equation. You've probably figured this out already. Len

Scary stuff! You're right on the return line. If everything is working properly shouldn't have high pressure on it. Having said that, I would do the same thing you did, use FI rated hose on it too. Len

sscanf I think once you dig in to it, you'll find the drift is actually in the multivibrator stage, not in the conditioning circuit from the CLT sensor. Not the entire multivibrator just the section that the CLT conditioning circuit feeds. Note: This is just my gut instinct as I didn't do a lot of digging back when I was investigating. That was several years ago. As you might guess, I have craploads of old boards. If you want, let me know and I'll send you a care package. This will give you a bunch of spare parts and several copies to do some comparisons with. I've already thrown away about a dozen I bet, but don't worry I have more. I cut the wires soldered to the output transistors & the cable that connect the two so if you wanted to put them back together in your box & actually fire them up, you'll have to do some soldering. +10 on what Zed, Fast, and Captain said. No electrolytic caps which is one of the reasons these ECUs are still even halfway working today. Electrolytics have there place in the world, but not in automotive applications. While you are in there, if you wanted to detail and create a schematic of their coil input conditioning circuit, that would be interesting to see as well. Captain and I both did some theorizing and testing on it, but I never traced it out. I'm not sure if Captain did or not. Lenny

Just a quick update. We have finally settled into a routine with the new baby & I can slice up some time for HellFire. I began flow testing the AFMs I have today. Bob, yours is one of the three I'm playing with now. As we discussed, it has an offset that should have been running your car waaay rich. I can see it in the flowbench numbers. woot woot! Why am I excited that his AFM is way off? Well, it somewhat confirms my flowbench I built is at least in the ballpark. I did have to modify my bench to give me more resolution at lower cfms & I also determined that I was giving up too much resolution on the actual AFM input to the HellFire. Some quick resistor changes on the HellFire board brought the signal back to where I want it at, and I had to machine some smaller flowbench orifice plates to bump up my signal for reading the CFM through the AFMs. Give me a few days to digest the data and actually understand it a little better & I'll post a summary and some graphs. Lenny