Have we decided on which is our official Mega/MicroSquirt thread yet? If so then merge this into it.

I recently took the Microsquirt 914 on a 5-hour each way journey from Connecticut to New Jersey Motorsports Park. I was a bit hesitant to substitute my comfy radio-A/C-and-DSG-equipped GTI for a 45-yr-old ride through the wilds (and traffic) of NYC, but the weather was forecast to be a nice Fall day so I went for it.

Loved it. Car ran flawlessly and the engine was a smooooooooooth as I've ever experienced it. No stumbles, no faults, ran cool on CHT and oil, just an absolute pleasure. 27.5 mpg average on 89 pump gas.

But of course, with no radio (by choice) I had a lot of time to think about my tuning as I was tootling down the parkways and interstates, watching the Android tablet display of engine parameters...it runs good, and it sounds good, and it feels good, but...is it actually good?

One of the biggest issues I faced/am facing with tuning is not the mechanics of the process; I quickly figured out how to use TunerStudio and Megalog, and I'm logging to either laptop or an Android tablet (ShadowTuner) via Bluetooth. And the VE Analyze function of Megalog makes it quite easy to review the AFR outputs in the logs and make changes to meet my AFR goals.

No, that's the easy part. The hard part is knowing where our engines want to be, for example in terms of AFR and ignition timing.

"Take it to the dyno!" you'll say. And you'd absolutely be right. But there's two problems with that.

First, dyno time ain't cheap if you want to do it right. It's not just a matter of showing up and tuning the VE tables to meet the AFR goals (and I can do that on the street). No, to do it right you need to spend an afternoon, or even a day, with a skilled tuner who can run the engine through a series of tests and tickle the edges safely to discover things.

The second factor relates directly to the first: finding a skilled tuner that not only understands the concepts of dyno tuning but also understands the needs and desires of a 75-year-old air-cooled engine design. Sure, the basics are the same as other engines, but I suggest the edges are much much fuzzier.

If I had someone with that talent in my area I'd absolutely leverage them. But I don't. I have some local guys that are good with their dynos but they're Honda guys, or Chevy guys; When I bring my 914 to them (and I have) they're glad to take my couple hours' money but other than tuning to my settings they're not really qualified to tickle (and if they're smart, they're not comfortable trying to tickle the unknown edges on a customer's car).

So any dyno work I've done was to my AFR and ignition settings. And I really don't know what I'm doing either.

I don't know what air-cooled dyno tuning experience there may be on this board, but I'd love to begin sharing some info on where we're going with these Micro/Mega installations. Where do these engines want to be? How much can (or should) we push them? What symptom(s) are we looking for to decide if we need more or less of anything? What's the sweet - and safe - spots?

I'm atttaching my AFR target and ignition tables, let me know what you think. Am I in the ballpark?

I'm not asking you for any secrets. I'm just looking for some feedback to understand if I'm setting myself up for problems in the future. This is not my race car, I'm not looking for that nth hp advance; this is my street car, one that gets driven only 3000 miles a year (if I'm lucky, especially lately). I want to enjoy it and not worry about it. And maybe I'll learn something in the process.

And...discuss! - GA

Good stuff, Greg, thanks for posting. I've got many of the same questions. I have contacted a couple of dynos relatively near to me (but still over an hour). I haven't pulled the trigger on any of them yet as a) it ain't cheap in our neck 'o the woods, and b) I'm not convinced they know how to really tune this setup. I may end up doing it, but for the time being, my car is a blast to drive and only really has a few minor annoyances.

EDIT
Basic engine specs:
2270
Raby 9950 cam
9:1 CR
Speed density, Wasted spark, 3 wire Idle Air Control, running closed loop idle....what else is relevant?

Since you showed us yours, here are mine:

Click to view attachment

You have a lot more advance than I do. I had mine over 30 until a few weeks ago, and I noticed I was getting some knocking on hard acceleration, so I backed off and took the max advance back to 27. That didn't fix the problem, so then I realized I was probably running lean under hard acc instead. So I fixed that in the fuel table, but I haven't bounced the max advance up again yet for some reason. Maybe I can do that now...

Click to view attachment

Your AFR table is a bit richer than mine. I'm not sure how much to trust AFR numbers. I've leaned these out over time because a) I'd like better efficiency - still seem like I max out at low to mid 20's in terms of MPG, and b) there is some evidence that I may be running slightly rich (e.g., plugs, etc.). I don't have any head temp issues, so other than the knocking as mentioned above (which I addressed), I don't think it's causing me issues. Still goes like stink through the whole driving range. But yes, this is where an experienced dyno guy who knows type IV's could really help.

Other than fuel efficiency, the only other real annoyance I have is that cold start Raby 9950 cam that can't get enough air and won't idle steady without some throttle feathering for about 30 seconds. I've messed with cold timing advance, mixture, and of course, IAC, until blue in the face, but it still happens. Not a big deal, really. I'd like to try a bigger IAC, but again, not a priority.

Great idea on sharing this info, Greg. Thanks again

Nowhere near your level of expertise/experience but would data logging exhaust gas temp be a good guide too?
I would weld a female 3/8” NPT half nipple on the heat exchanger near head output and use a through hole brass 3/8npt to 1/16” Swagelok and a 1/16” SS k-type thermocouple poking in to measure the hot gas.
Would this info help on the tuning?
Implementation is simple.

Those go hand-in-hand. I'm running fatter more as a safety measure, but I'm comfy with more timing mostly because it's a street car and I don't tend to run it hard. Any hard running I do will be momentary, rather than extended such as if I were doing lapping days.

Don't we normally set our stock D-Jet cars up at around 29 degrees total advance? With good gas and better fuel management I suspect they'll tolerate more timing.

Plus, I normally run it on 91 pump gas which should be more than enough for this 9:1 FAT 2056 engine, and a conservative cam. I ran it on 89 for my NJ trip because I knew I'd just be highway cruising all day in the middle of the tables...plus have you seen the price of 91 lately...??

I'd like to get a better idea if, for example, I were to do a track day of 15 minute sessions, am I setting myself up for trouble?


Sure. But as with AFR, timing, and CHT (all of which I'm logging now), what's the bogey numbers for EGT? My prob is that I have all this data, which sounds great, but I don't know what to do with it...thus my thread.

We have a large historical dataset of what we don't want CHT to exceed on these engines, but the other stuff seems to be mostly wizardry and guesswork.

I've given thought to using either CHT or EGT to swap to alternate tables - for example if CHT or EGT exceeeds xxx then go fatter and pull timing - but again I'm not even sure what I'd do with that. - GA

A good idea is to include the specs of the engine along with the tuning info so readers can know what engine size and spec the tuning is for.

Good point, Mats. I'll edit my thread to reflect that.

Mine already has it -- unless it's "TL;DR"... Not sure what you mean by "tuning info"...isn't that we're trying to figure out?

Though, I doubt that detailed engine specs will change much of the underlying concepts. I don't expect (or intend) that we'll have someone coming along and saying, "Hey, Greg, take 3 out of Cell XX/YY" because, frankly, I wouldn't do it anyway b/c that kind of advice indicates they may be FOS . It's also why I will not give anyone my map tuning files (unless I really really know them) because it could do real damage to someone's engine, even with monir differences.

I'm certainly glad to discuss underlying concepts, and tuning strategies and tactics. We need some general engine technology and starting points and goals; if you're smart enough to be tuning an aftermarket EFI then you're likely expecting to do some level of W.A.G.ing along the way...just looking to minimize it. - GA

Thanks for setting up this thread. I am several weeks away from my first attempted engine start, but hope to learn from what you all have done.

Thanks for starting this thread! It's almost like you read my mind. As some of you know, I'm planning to megasquirt over the winter and think I have a pretty good plan but am in a bit of a holding pattern to finish up a few house projects and also for Mario to reopen his online store so I can buy some sensors. In the meantime, I've been doing the most dangerous thing which is watching youtube vids about tuning and reading this book by the DIYAutotune folks.



I've come out with the same thoughts as Greg that I don't see a dyno being an option. I have only found one car dyno in the area (there are a few motorcycle dynos) and this is Montana so you can probably guess what kind of cars (hint - trucks) they are versed at tuning. Even the area Euro car specialist mechanic has stopped working on aircooled cars even though they are Porsche guys and one of them has a 914. Also, while that book outlines what seems like a pretty safe procedure for tickling the edges with a dyno, it's all geared toward water cooled engines so not very helpful.

Also, I've read through this thread about AFR several times learning about what is safe for an air cooled Type 4. http://www.914world.com/bbs2/index.php?showtopic=304320. In particular, I'll be taking @Mark Henry 's advice to stay on the fat side to keep CHT down.

To that end, I thought I'd start with an ignition table pretty much like Rob's which looks to be close to a stock curve just to be safe. I still have a lot to learn about when it is safe to run more advance, and what you gain so am enjoying the discussion on that. I was also a bit surprised to see areas going to stoich and even leaner on both of your tables - again, thinking about CHT and being a total ignoramous on the subject myself.

I mentioned this on my megasquirt thread but it seems like a closed loop fattening the AFR or dialing back advance when CHT starts to climb beyone spec would be ideal, but the only out of the box solution I've found is using alternate AFR and Ignition tables triggered by CHT as Greg mentioned. A loop seems like it would be a good way to tickle the edge from the efficiency side at least by building finding the edge into the algorithm. I am not shy of diving in and writing some custom code, but not when a bug could cost me my engine.

As usual, I have only questions and no answers but am bookmarking this thread as it is surely going to be a great resource as I move through my project. Oh wait, I do have one bit of advice, Hey, Greg, you should take 3 out of row 2 column 11.

Well Brent, I just made mine a little more aggressive last night after reading this thread Reminded me that I solved my hard acceleration pre-detonation with fuel rather than timing but forgot to put it back the way it was. Haven't uploaded to the ECU yet, though.

I've got a CHT that's pretty prominent in my console, and my head temps are surprisingly cool, all the time. I don't get above 300 very often. It may be the ceramic coating on the combustion chambers, the general engine combo, or something else entirely. I guess I'm also aware that the CHT may not be telling me everything. Oil temps are a different story, however. They are manageable, mostly, but not necessarily ideal In hot weather it sometimes changes my driving style. For example, I may violate the cardinal rule of air cooled and cruise at lower RPM's, e.g., under 3K. Seems to keep oil temps down without bothering head temps too much.

Again, my tuning "pain point" other than cold starts is fuel efficiency -- I suspect I'm not running as efficiently as I could be based on MPG and a couple of other indicators. The nice thing about these systems, of course, is you can have multiple tunes. Want a max efficiency tune for a long drive? Load that version into the ECU. Want a really fat tune for performance at the next AX? Boom, load that one in. When you're done, put the efficiency tune back on for the ride home.

I must admit I'm not 100% sure of the relationship between the AFR and VE table. I probably should do some research on the forums, but here's what it says in Tuner Studio:

Including the AFR target with the speed-density, alpha-N, ITB or map/baro algorithms, this allows the VE table to be a 'real' VE table and the desired AFR to be specified in the AFR table.
With AFR not included, the AFR table is for reference only and the 'VE' table takes full control.

With the MAF algorithm, this MUST be enabled to factor the target AFR into the fuel equation.

Note that this function does not require or use feedback from an O2 sensor.

That last sentence has me a bit confused. Does that only apply to MAF? (For reference, I'm running speed density. I updated my first post above to reflect that, as that's kind of important to know.)

More info. Here's an annotated AFR table. I spend 99% of driving time in one of these circles (very roughly). I initially struggled with idle, as mine has a higher pressure (kPa) (lower vacuum) than almost anybody else I referenced, air or water cooled. I don't know if it's the Raby cam or something else. After a while I stopped fighting it and "gave the engine what it wanted." Any AFR numbers way outside of those circles, or when moving between them during driving, are basically irrelevant.

Click to view attachment

I don't understand those paragraphs from TunderStudio either, but I do understand that Squirt uses the AFR input to adjust fueling to target your desired AFR. That's the EGO Correction you see happening as you're driving along.

Overrun: are you using "Fuel Settings", "Over-Run Fuel Cut"? If not, I suggest it. I spent a bit of time tuning mine to where it drives a lot like my GTI.

I like how you've noted where you drive, generally. You can also see that in Megalog Viewer, under "Scatter Plots". The Histrogram area also weights the amounts of driving you're doing within the cells. It's a hoot to compare my street 914 to my Megaquirt MR2 racer, two totally different driving area (as expected).

Greg, that's got to be the weakest part of TS: the contextual help info. I'm glad they include something, but it's sometimes not that clear or helpful. The way you describe the AFR correction is how I understand it. Just not 100% sure if that's the case.

I'm not using over-run fuel cutoff. I guess should try it and see what happens. I've never played with that, nor really acceleration enrichment, although I'd like to try both. Good tip.

I have Megalog viewer but haven't seen that histogram yet. Gotta check it out!

Try the overrun cut; here's mine. Should be damned close except you've noted your MAP is not strong; will cam really matter on a closed-throttle car? To remind, I'm using the D-Jet throttle body and induction bits.

Thanks for posting that AFR table with circles Rob. You helped me realize how dumb I was being about where idle was on that table. I was thinking it would be at the bottom where you have 15s because I wasn't properly thinking about load in terms of MAP. This makes much more sense. I also appreciate you posting your fuel cutoff setting Greg. I had read fuel cutoff helps eliminate popping on overrun and makes sense for efficiency. Why squirt fuel when it is not needed?

I was also confused by that same para in the Tuner Studio manual. In fact, I'm still rather confused about the point of a VE table in general. The AFR table makes much more sense to me and if mixture is being adjusted using EGO feedback, then what does the VE table do?

And Greg, can Shadow Tuner log mpg? I read about an app that can use your phones GPS and fuel data from megasquirt to report real time mpg. I think I downloaded the app to my phone, but it is not handy at the moment to see what it is.

Yes it can. I'm not sure what all the requirements are, as I'm not doing it, but I know others have this capability. You're already capturing total fuel during a trip, so it's just a matter of capturing distance.

I poked around and found this menu, which I hadn't really touched in a while (that's another issue with TS, so much functionality is buried in different places). I believe this is the relationship control between target AFR and the VE table. The VE table is what's actually used to adjust pulse width. But we understand AFR better (in general), but I believe this is how, and how aggressively, you can control VE using AFR targets.

Click to view attachment

Greg, I've got the fuel cutoff enabled now in TS. Just need to burn and take it for a spin...maybe this afternoon.

SOOOO much to comment on here, both general information and specific cases that have been posted.

I expect its going to take me a couple hours to address everything though so will be looping back on this when I have a little more time.

Uh-oh. I feel like I'm 10 years old sitting outside the Principal's Office waiting for him to call me inside...

LOL

Hey, If your car is running well no one can knock that.

But, if we are going to talk about what we can do to really dial in our tunes, as with everything else Megasquirt that becomes a a pretty big discussion.

Honestly the timing and AFR tables you posted are pretty inline with where I usually start out save for a couple minor points so I would imagine its running pretty well. Of course the reason I start with those numbers is that they closely mimic what the factory parts do. Where it starts to get interesting is that we can do a lot more with Megasquirt than the factory d-jet and mechanical distributor could but at that point we are entering undocumented territory so who is to say what is right and wrong? I mean at least until your heads melt or you crack a piston, then its usually safe to say someone may have been wrong.


When I look at the maps @GregAmy posted my initial thought is "WOW, thats a ALOT of ignition advance" BUT then noticing that the WOT areas are more conservative I cant say for certain one way or another if it would be a problem or not as the increased advance is all taking place under part load and overrun where it is a little safer to do such things. Then however we have the other important question of is it gaining(or hurting) anything to run that much advance? Because of the nature of the mechanical/vacuum distributor the factory couldn't do things like this even if it was advantageous to so i suspect there are gains to be had but because optimal timing is a function of the mixture figuring that out for anything other that WOT without additional instrumentation is going to be tough.

While its not ideal I usually fall back on head temps and drivability to work out the rest (non WOT areas) of the map, but my MS car is currently only used for autocross so I haven't cared to much about optimizing anything but the part of the map that makes POWER, other than to keep it from melting down on my way to/from autocrosses. But on that point of melting down, I am "blessed" to live in one of the worst parts of the country for air cooled cars from a survivability standpoint so special attention needs to be paid to keeping a tune from melting heads around here. These motors can run on a surprisingly wide range of timing and AFRs however what runs fine on flat ground at sea level on a cool fall day might not work so well in the summer over one of the passes around salt lake with ~20% less cooling air density, 100+ degree temps and 5000ft elevation changes.

and I see a couple things that may be of concern if you were to run at the extremes.

anyways... this wasn't the post I was planning on responding to so... more to come when I have the time.

times a bit limited for me at the moment, recovering from knee surgery so basic stuff is taking a lot longer than normal.

So if you are talking about the setting I think you are talking about, the difference between the "incorporate AFR target" setting being enabled or disabled is best explained by showing exactly what it is doing

The basic fuel equation is:
PW = ReqFuel * VE(rpm,map) * MAP * GammaE

With incorporate AFR it becomes:
PW = ReqFuel * VE(rpm,map) * MAP * stoich / targetAFR(rpm,map) * GammaE

So... thats the math behind it, but why? Basically the idea behind it is that IF you had your VE tabled tuned so that they produced exactly the AFRs represented in your AFR table you could then enable the "incorporate AFR target" setting, at which point you could in theory just update the AFR values on the AFR table to change your tune.
...in theory

its a feature that requires a lot of prep work in that you have to have your VE table tuned to your AFR table perfectly before even enabling it for its function to make any sense. You absolutely dont want it enabled when initially tuning your VE table or you will cause yourself unnecessary headaches.

I just leave "incorporate AFR targets" disabled all the time.

That is not the only function of the AFR target table though as it is also used for the closed loop wideband O2 correction(if enabled) and with tunerstudios autotune.

In some cases it may be a bit subjective, I guess we should start by asking...

What is your measure of "actually good"?

Power? Fuel Economy? Not Blowing Up? Emissions? Something else?

I mean it sounds like you are at least fairly happy with it. I guess the blessing (and maybe the curse) of something like this is that there is almost always room for additional refinement and tweaking though.

Its hard to say without riding in/driving the car or at least looking at some datalogs if something is obviously out of whack, but if you are happy with it and it isnt blowing up, that seems pretty good.

Just glancing at your AFR targets and timing map though I would guess you have both a little power and fuel economy still on the table, but optimizing it is going to be a lot of trial and error, and fully optimizing it will probably need additional instrumentation.

James, thanks for helping out and sharing so much experience with us. It's amazing how deep this can get, and it does seem one can spend years trying to learn it, and many minutes hours trying to explain it. Uh, I'm also glad to see, based on your response, that at least I didn't completely step in it

That equation makes perfect sense. I had to look up "GammaE," but I guess it's the combination of any other enrichment factors currently enabled, correct (e.g., warmup, accel enrichment, etc.)? So really ALL the AFR table is doing is changing the pulse width by the factor of dividing stoich (14.7 for pump gas) by the target AFR (e.g., 13.9). So in this example pulse width would be modified by a factor of 14.7/13.9, or roughly 1.05, all other enrichments being the same.

Curious why you wouldn't use it? Is it because you are more comfortable with manipulating the VE table directly at this point?

Greg, I incorporated fuel cutoff similar to your specs and took her out for a spin yesterday. I like the change. We'll see if it increases efficiency, but I'm going to run with it for a while. I do recall that D-Jet incorporated a fuel cutoff logic on one or more model years (maybe '73?), but then discontinued it. IIRC the thinking was that it somehow impacted emissions negatively by introducing more variation into piston temps. Or something.

I also bumped my total advance back up toward 33 degrees, but guess what, I started getting pre-ignition under hard acceleration again. So I backed it down to 30, and it seems better there.

Here's the actual Megalog histogram (that I've never really used before) of my drive. Darker green is where I spend most of the time, I guess.

Click to view attachment

In some cases it may be a bit subjective, I guess we should start by asking...What is your measure of "actually good"?

Drivability. Reasonable power (it is, after all, a 75-yr-old engine design). Certainly some reasonable level of fuel economy.

My tuning standard is that I want my Honda-driving brother-in-law to be able to jump into the car, fire it up foot-off, and after figuring out where first gear is drive away slowly (I'd coach him being easy on it the first couple miles) and not complain how it drives. Smooth, no choking, no burps. You know, like his Honda.

I want him to be able to come back with the car, complain about first gear (they all do), and go "yeah, it drives OK, whatever."

It took a bit but I *think* I'm close right now. I still need to work on my sub-60-degrees ambient cold tuning, but I'm pretty solid in 70s-plus.

Power? Fuel Economy? Not Blowing Up? Emissions? Something else?

I'm not going for outright power, that's not the car's mission; I have the race car for that. But I want the option to be able to take it to a Track Night in America and enjoy an afternoon of 20-minute lapping sessions without worrying about blowin 'er up. I AM NOT convinced I've got that, as I haven't really played out there.

Fuel economy and efficiency is certainly a plus, but given the low miles it's being driven anually a 1-2 mpg difference will have neglible financial value. Given I averaged 27-28 highway on this last trip I can't think I could be greedy and ask for more, but I certainly wouldn't reject it, as long as it doesn't compromise driveability.

Emissions is not really a consideration, for the same reasons as fuel economy. But I'd not kick it out of the bed.

I am reasonably happy with it within the range of driving that I have been doing. But, as Rob, illustrated above, that's a narrow range and nowhere near pushing the edge where I could potentially cause damage (and/or have poor driveability.) So I'd like to have a better concept of where I should be at these extremes to where I can feel safe to tune out there, either at a dyno or during a track lapping day.

But within the current driving ranges, I'd be hard-pressed to justify any significant changes.

Here to learn... - GA

I dont run MS on my car but I figured I could post my tables and maybe there is something someone can learn from them. My engine is a 2256 cc, 10.3:1 compression running 40 mm ITB's so the table setup is reflecting that with Alpha-N and its running in wasted spark.

Click to view attachment

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The darker pink area in the ignition table is basically my cruise settings. Its usually done between 12-15% throttle opening. Cruise CHT temps is in the 280-330 range with cyl 1 being the hottest one and always 25-30 F higher than the others.

Click to view attachment

I have a friend thats tuned it for me and the priorities was.

1. Safety (never lean, no detonation etc)
2. Driveability (wide torque range)
3. Power (connected to the above)
4. Milage
5. Emissions (only measured every two years and at idle)

I dont know about learning anything, but I can tell from your fuel map that your cam sure isnt stock!!!

And I thought my motor was a screamer, that thing must be tons of fun once you hit 4k RPMs


Are the 40mm TBs large enough to feed that thing? I tuned a 2270 with a milder cam and some smaller (i think 42mm) Jenvy ITBs and I could see a noticeable intake restriction in the datalogs. could have been his tiny air filters though.

Correct, its got a web 86 b/c cam. I wasnt sure what size ITB to get when I built the engine so I erred on the smaller side to keep the air/fuel velocity up to aid the low end.

Which reminds of two generic things I was thinking about.

Is the VE table an actual indication of fuel flow, other than internally relative, given possible (probable) differences in installed injectors/fuel pressure? Said differently, is the VE map calculated in such a way to be generic that it can be used across a similar engines, regardless of fuel pressure and/or injectors?

And, is the 3D VE map a good visual indicator of the torque curve?

GA

As I understand it the VE table is relative to the injectors and fuel pressure. The number in the cells is the injection time in milliseconds. Changing the injector size or fuel pressure would change the numbers so for the fuel map to be usable between two engines the setup has to be close to identical.

Edit: Maybe I'm wrong as the VE table says % after the VE? Time to google stuff.

IF (and this is a big if because a lot of people miss this and dont) you have the REQ_FUEL constant configured correctly for your hardware (injector flow rate, engine displacement, and fuel type) than the VE (Volumetric efficacy) table should represent exactly that, the pumping efficiency of the engine at the specific load bins. You will notice that the REQ_FUEL value is actually represented in milliseconds and this is basically the injector pulse required to get a stoch burn with the specified fuel if the specified displacement was able to fill 100% with fresh air.

I have seen a lot of people that treat REQ_FUEL as some sort of tuning parameter. It isnt, its a defined constant that should match your hardware.

If you have your REQ_FUEL and dead time set correctly you should be able to swap injectors/fuel pressures etc without re-tuning anything provided you know the old and new flow rates, simply by updating the REQ_FUEL and dead time constants to match your new hardware. This is also one of the reasons that people sharing fuel maps and/or entire tunes tend to usually not work out so well. If your REQ_FUEL and injector dead time settings are not spot on any tune you build on top of them is only going to make sense with your specific build.


I would say the VE map probably more closely mirrors Horsepower than torque. It for sure indicates where the engine is working most efficiently at ingesting air. Megalogviewer actually has some functionality to calculate horsepower based on log data however the accuracy of this (like everything else) requires that all the input constants for the calculation are set correctly in order to be remotely accurate.

Most type 4s I have worked with tend to see peak VE #s in high 70s to mid 80s on finished tunes. Some performance builds wind up being higher than that. You will find that the peak VE values on a map then should line up pretty close with the peak power output for the motor.

So just by looking at @falcor75 VE table, assuming the MAP is dialed in/accurate, one could assume his peak HP is probably happening somewhere around 5500 RPM, maybe a little higher. Stock 2.0Ls you will usually see the peak VE numbers closer to ~4700-4800 RPM.

Good to know, and that makes sense. Mine seem to follow that, with the bigger numbers coming around where I'd expect to see peak HP. Non-demoninational, non-religious, generic 3D chart enclosed; peak VEs are at 4300 and 4800.


Lol well I certainly done did it wrong, with many numbers exceeding 100 toward the top.

But, as you describe, my "Required Fuel" was an initial WAG. It was based on TS' calculations from engine displacement and rated injector flow (Five-O 280cc injectors). I'm running a Bosch 3-bar pressure regulator.

I don't see any value in changing it and re-doing the VE tables, unless that gives a knowledgeable tuner pause because he/she is working outside their comfort zone. I'd do it if I had to but I think I'd lose a lot of gain for where I am now. - GA

I'm learning

In my noodling around trying to get a remedial grasp of this stuff, I saw a lot of example VE tables topping out well above 200 which is what led to my question about why not just use the AFR table. One youtuber who seemed to have a decent grasp of what he was doing simply explained it as a relative scale for adjusting injector PW. Plugging in actual VE numbers with a max of 100 makes more intuitive sense to me even if either way produces the same result.

I also have been confused about stoich.settings. Of course "regular pump gas" these days is E10 which has a stoich of ~14.1 but all AFR examples I've seen are based on stoich = 14.7. Are they just assuming everyone runs pure gasoline? My stocker engine has 8:1 compression and runs just fine on 85/89 octane regular gas, so that's what I'll run most of the time. What's the proper setup and does what you use for stoich in the afr table matter if you are running closed loop with a wide band?

I dont think you got it wrong, if you are running the A280H injectors I am guessing you have REQ_FUEL set correctly as flow info and deadtimes actually come documented with them. Also, interestingly enough, when I switched from using stock 2.0 injectors to the A280H with a 3 bar regulator I saw my peak VE numbers jump above 100 as well. Why? Not 100% sure but i would assume the difference between the two injector sets is that everyone (myself included) has always guessed at the actual deadtime and voltage correction settings for the 2.0 injectors and so they were most likely wrong and throwing off my whole table, this was one of the major reasons I went to the new injectors. Knowing the exact injector specs I can now kick on my headlights at idle and not have my mixture shift on me.

The other reason why seeing numbers above 100 on the VE table makes sense is that 100 represents perfect efficiency IF we had the bin tuned at 14.7 AFR, but in those bins we are fueling to mid/low 12s which mathematically then looks like we are more efficient when in fact we are just running rich of stoch. We could do the math then if you wanted to know the "actual" engine VE, basically (Target AFR/14.7)*Table VE=Real VE So if you are seeing 105 VE in your table running at 12.3 AFR the pumping efficiency of the engine is really ~87% which is in the realm of believability for a mild performance cam. This of course assumes you don't have anything else factoring into the fuel equation at the time (like having turned on incorporate AFR targets)

CAM, Intake, and exhaust all impact VE as well.

Still working on this one, few things left to dial in Had some issues with the CAM sensor necessitating I pull the engine to adjust it but went in for knee surgery before I got it all done so now its waiting for me.

Testing the hard rev limiter here. I keep it on the conservative side at 6300 most of the time, but will bump that up on the day to 6500-6700 if the autox course demands it. I have reved this thing to 7k without realizing it before, hence the limiter

As you can see its a pretty peaky and rev happy motor. comes on cam hard around 3800

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This probably also worth noting as i know we have had some discussion in other threads around injector selection

Max duty cycle i am seeing with the A280H injectors @3bar on my motor (CAM'd 2056 with headers) is still only about 52% @6000rpm. Granted I am at only 85% atmospheric pressure here in salt lake, down at sea level this would probably be a little higher, still lots of headroom on these injectors though.

I swear ill get around to responding to the original posts on this thread at some point...

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Anyone want more math exercises or for me to explain why you should be running the %barro fuel algorithm instead of straight Speed Density?

A few reasons im not really interested in it at the moment

In my mind its just a feature that adds some simplicity by adding complexity and an additional factor to the fuel calculation. Also for it to make ANY sense your VE map has to be a dead on match to your target AFRs BEFORE enabling the feature, and for various reasons im not 100% sure I trust my O2 readings in all cases.

I think some of the bigger issues for me is that once enabled your VE table is no longer an accurate representation of the fuel going into your motor as it has a factoring table then calculated on top of it. It prohibits you from editing you VE table directly without royally screwing things up, which then means you can no longer run autotune either. I dont necessarily have anything against the feature, but its a feature you only turn on once you have everything dialed in as far as hitting your AFR targets and then its only real use is experimenting with changes to AFRs. I already know what I want my target AFRs to be when im dialing in the VE table to hit them and even then, if I want to adjust them after the fact its not a big deal, so yeah, just not worth the effort to me. VE table is easy enough to use, you want more fuel in a specific area, increase the number, want less, decrease it, then take some datalogs and see where you are at. I could never trust a factor is going to get my fueling exactly where I want it so im going to be checking the logs either way.