From Sea Level to 10,023 ft

That is some serious awesome! I'm stealing that!

To expound a tiny bit on WHY Alpha-N(throttle position based fueling) works better with ITBs(individual throttle bodies) than a MAP(manifold air pressure) sensor:

With ITBs, once you open the throttle plate beyond 10-20% there isn't a real good vacuum signal as it is pulsed every time the intake valve opens for that cylinder only.

The MAP sensor relies on a stable vacuum source to determine fueling. This works very well in single throttle body situations, and works better with more cylinders and especially with a big plenum in the manifold. Stable vacuum is VERY important.

Once I get mine dialed in as good as Mike, I may play with adding a second fueling map to add/subtract(blend) with the main fueling but only at small throttle openings as in cruise situations.

Mike, can I borrow Marianne? Barring that, I'll have to log the data and tweak later...

Interesting......OK.  so how's this relate to jetting. ?  Like how much smaller would you go for instance if you were jetted for sea level ?What would you do for your injection ?.......Bruce

@DannyP posted:

Mike, can I borrow Marianne? Barring that, I'll have to log the data and tweak later...

We were having lunch up at Kula Lodge and marveling at how we've stuck together for 53 years (49 married).

She's NOT a computer gal, but she's been a good sport about helping me tune a number of EFI projects over the last 20 years.

I must admit the tuning help today cost me some time sitting outside a curio store while she picked out some required objects.

Good trade. I'm sure she'd be happy to help you out for the same deal 🙂

@aircooled posted:

Interesting......OK.  so how's this relate to jetting. ?  Like how much smaller would you go for instance if you were jetted for sea level ?What would you do for your injection ?.......Bruce

I'll give it a (somewhat) edumacated guess- with 8 data points from 0- 10,000 ft- a (very) rough guide would be aprox 5% reduction in fuel VOLUME every 1200-1500 foot rise in elevation.  I mentioned volume specifically because a 5% change in the diameter of a circle is an almost 10% change in it's area (or in the case of a tube, volume).                                                                                                                                        If I'm totally of base here someone with more knowledge please chime in...

@Michael Pickett- when you were correcting was it rich or lean on a regular basis or sometimes one and then the other?

Your guess is better than mine, @ALB. I went to EFI after my kadrons told me that 5000 ft didn't agree with them. There are some real jetting wizards here and I'm not one of them.

To answer your correction question, I was always leaning out the fueling as we gained altitude. In this case, it took more throttle to fill a cylinder with a certain volume of air since the air pressure was lower. Without Baro correction the ECU looks at the throttle position and sends more fuel than matches the air in the cylinder.

The Alpha-n setup sends the matching volume of fuel based on where you set your ideal tune. I spend 90% of my driving at sea level so that's where I set my base tune. I've got a table of throttle positions and rpms that's filled with my desired air:fuel ratios (Target AFR). After getting a rough tune (you turn the TunerStudio Autotune on), the laptop will adjust your fueling map so it's close to your AFR targets.

You then just datalog your driving for a few days and use a finer grained program (MegaLogViewer - MLV) under lots of driving conditions (low speed, full throttle runs through the gears, highway cruising, etc). MLV will take the log files, exclude whatever you want (records below a certain temp, rpm range, etc) and give you a revised tune based on your AFR targets.

Rinse and repeat making the changes smaller and smaller (you can set it Easy to change, Normal, Hard, and Extra Hard to change). At the end, you've got a 95% good tune that you can do minor tweaks to.

So, I'd done that already at seal level and liked the tune. I could then just head up the mountain and tell the Baro table the percentage of fuel I wanted it to take out of the known good fuel table.

I know it's complicated, but not having to take the tops off of the kadrons and finagle the jets at the bottom of the bowl is rewarding.

Sharing your AFR targets feels a little like telling what oil you use, but here's what I like for how I use the car. RPM is at the bottom and % throttle on the left.

I thought you had already done elevation tuning with intake manifold vacuum as main load so I was wondering how off that was as you went up- how much correction did you have to do and how far out did you find it went when remapping at sea level?

@ALB posted:

I thought you had already done elevation tuning with intake manifold vacuum as main load so I was wondering how off that was as you went up- how much correction did you have to do and how far out did you find it went when remapping at sea level?

Turns out that elevation adjustment using intake manifold pressure (MAP) works very differently than using throttle position (TPS).

Here's the logic with a MAP setup: you start with a well tuned fuel map at sea level with RPM as the X axis and MAP (engine load) as the Y axis. The contents of the fueling map are the amount of fuel needed at that RPM-MAP point.

As you gain altitude, the MAP readings drop because the air is less dense. However, for the most part, the ECU just looks up the appropriate amount of fuel for that manifold pressure and everything is fine.

However, another thing that's happening as the barometric pressure drops is your exhaust back pressure also drops. That makes your engine more efficient and means you need MORE fuel for that particular MAP reading and RPM. So, the baro compensation table needs to add a little fuel as you gain altitude.

Throttle position (Alpha-n) setups don't know nothing about manifold pressure (unless as Danny notes, you tell it to blend in a bit of compensation for MAP - hard to setup).

As you gain altitude your engine gets less and less air(oxygen) in the cylinders on each stroke making less power and you push down on the throttle to compensate. The TPS based setup sees more throttle and squirts as much fuel as it would need to match that setting at sea level. So, it runs richer and richer as you get thinner and thinner air. The exhaust back pressure drops making the volumetric efficiency a little better, but TPS tuning runs so much more rich, it still can't use all the fuel. With a TPS setup, the Barometric correction tells the ECU to squirt an appropriate percentage less fuel as you gain altitude.

Temperature impacts on fueling needs are compensated by the coolant and intake air temperature sensor tables.

The other thing that will affect fueling needs is the humidity. I don't worry about that 🙂

More than you wanted to know about how EFI controls things that our carbs don't have a chance of responding to.

Don't get me wrong, carbs are perfect for most folks who spend most of their time around the same altitude. There are some edge cases like mine where EFI is better.

Cheers

I recall way WAY back when with my A Coupe, having to change out my air correction jets when I got to Denver.  It Was not hard to do, and I could not tell you one way or the other if it made a hill of beans difference.  But the guys said do it, and so I did before scaling the Rockies. Two little Solexes, 32s I think.

As to EFI on Type 1s: sounds like a really cool theory.  Also sounds like a whole lot of theory and somewhat less actual fine reality, rather too hard to nail down.

Too hard? No such thing. It's the challenge of it.

And I have to say, even in my non-warmup compensated EFI with a beginner's fuel map, the car runs smoother, stronger, and cleaner than it ever did before.

As musician Howard Jones said, "Things Can Only Get Better".

Is there any way to get a 1979 VW fuel injection motor  to run with another  computer?
We have a motor out of a 79 convertible sitting in the shop,

Also later Mexican bugs were Fuel Injection . No idea how they are setup

I've seen the OE injectors and throttle bodies run with Speeduino or Megasquirt.

I like wires, software, and debugging. Plus, I caught some OCD when I went unmasked to a science exhibit when I was but a wee child.

So, like Danny, I'm the poster boy for homebrew EFI setups. Most people aren't and that's ok. I'm still hoping he'll turn his passion into another part of his "retirement" business so others can enjoy cars that run "smoother, stronger, and cleaner!"

So.

Freaking.

Cool.

I know you guys want me to really get into the EFI "package" deal. I am not sure that is going to be my focus. I really enjoy mechanical and wiring fabrication, routing, installation. I like the challenge of making things fit AND work well together. Packaging and problem solving are my thing.

Perhaps Mike and I can team up, as I REALLY enjoy building and fitting, and he likes the programming, debugging, and tuning. This might work, as I've emailed my tune and datalogs to Mike for analysis. And he's been really helpful to me, an EFI tuning neophyte.

That might be the solution to those fearing air cooled engines  … ah yes bUt then it still leaves the valve adjustment that needs to be done stone cold… sober .  

Honestly it is a great idea!  Hats off to you guys !

Are you even serious, Ray?

I'll take a valve adjustment ANY day of the week over coolant, hoses, radiators, water pumps, and yes, COOLANT LEAKS!

To get no valve adjustments, you have two choices: hydraulic lifters(which are an option, but not for me) or a watercooled engine with no adjustments needed.

Not to mention all the extra weight you're carrying for all that crap. And don't forget air bubbles and bleeding...

I'm going with air cooling in my clown cars, thank you.

@DannyP wrote: "Perhaps Mike and I can team up"

Yeah, and that yearly "Business Meeting" on Maui could be written off, too.

I'm Jus' Sayin'........

@Gordon Nichols posted:

@DannyP wrote: "Perhaps Mike and I can team up"

Yeah, and that yearly "Business Meeting" on Maui could be written off, too.

I'm Jus' Sayin'........

Wait, I thought the yearly meetings were going to be in Galax

@Michael Pickett posted:

Wait, I thought the yearly meetings were going to be in Galax

May I suggest you meet "halfway" (between Maui and NY) in the People's Republic? We have corn AND beans.

Not so much on the elevation changes.