Building a Microsquirt Daily Driver

[Piledriver]

Do you have "map averaging" on?????

Before that was a feature, my map would go from 115 KPA to ~85 KPA between 3900 and 4100 RPM, then slowly rise as RPMS climbed..
It wasn't REAL, there was no loss in performance, but setting the VE table up to compensate for it was a PITA.
it was the natural resonance of the intake and the MAP sampling aliasing//picking it up.
The actual airflow had little>nothing to do with it.

The high rate MAP oversample/averaging option fixed that perfectly, and WOT pulls give a rational MAP reading.
(That's why it exists)


The box the air filter resides in is ~guaranteed to produce a resonance, a lot of factory cars rely on that, and superbikes lose ~15% off the top if you remove that "restrictive" airbox/plenum.

That's part of why I find the typical ricer cold air intake so hilarious.
I haven't seen a factory air filter box that wasn't fed by cold air made in the last ~20+ years.
(This included VW T3s with DJet 40+ years ago)

[supaninja]

Shoot type 3's had cold air intake since day one 52 years ago

[turbobaja]

I'll have to see if I've got "map averaging" on. I'm as green to tuning with MS as they come, so I've got a steep learning curve ahead of me.

I couldn't agree more with the "cold air intake" fad being absolutely ridiculous. I find it amazing how many people pay good money for an intake that replaces they're well designed factory "fresh air intake" with a noisy, fancy looking intake/filter assembly that actually draws in warm air now from behind the radiator, inside the engine compartment. See it literally every day at work

I assume the inlet on the stock air filter housing was designed for more than good looks, but there's some point where it seems like it would become a restriction, especially with the T-body bore being quite a bit larger than the air inlet. It seems like a better match for the 34 PICT3 carb feeding a stock displacement engine. With another ~190cc to feed and a 1 3/8" merged header/heater box exhaust, the stock intake opening seems like a logical source of restriction. However, I can see how resonance could create what "looks" like a restriction depending on how the data is interpreted.

Can't wait to test it out

[gearheadgreg]

It's a bit of an aside, but relavent to these posts - back when I was in college in IA, I worked at a VW Porsche shop that had a flowbench. Spent every free minute on that thing. One day, I set up a complete Rabbit CIS intake system - complete! Looked funnny all proped up in there. The most restrictive part of the entire intake system? The largest cork - was the air filter housing! Putting on large throttle bodies, or cams, ported heads, etc. wouldn't do much because the bottle neck was the air box inlet. Cutting holes moved the restriction to the next thing. You very will could be exactly right.

[Piledriver]

The later model airboxes often had holes from the factory.
Might have been so it made a "sportier" sound as much as for airflow.

OTOH the resonance effects may have had more significance than the raw steady state airflow would indicate.
In intake tract makes for a serious audio driver.

[Clonebug]

Just put a little exhaust driven air pump on there and the restriction is gone......

[turbobaja]

Just put a little exhaust driven air pump on there and the restriction is gone......

I WISH!!!

I finally had a chance to test drive the slightly more open airbox intake and recorded my first data logs. It seems to have changed the MAP readings, but not necessarily for the better. It still struggles to read within 20% of atmospheric pressure during WOT operation around 2,500-3,500rpm, but does swing up to almost 100kpa by 4,000. I measured the stock trumpet ID right at 32mm. The throttle body bore is almost 40mm. The opening now is an oval, close to the throttle blade in cross section, but w/out the nicely rolled trumpet lip. I'll figure out the inlet shape later, for now I'm gonna take a couple logs with the top completely removed and see what changes. I also disassembled the T-body and ground the lips off the inside of the bore on either side of the throttle blade opening to (hopefully) give an earlier/smoother throttle tip-in. Also relocated the IAT from the T-body bore to the air box base.

[Devastator]

Are those sealed throttle shaft bearings?

[turbobaja]

Are those sealed throttle shaft bearings?

Yes they are.

[Piledriver]

It still struggles to read within 20% of atmospheric pressure during WOT operation around 2,500-3,500rpm, but does swing up to almost 100kpa by 4,000.

It still tells me you probably don't have averaging on and you are possibly making tuning choices based on resonance artifacts instead of actual valid MAP data.

I personally wouldn't cut/modify any more stuff up until you have valid data to base decisions on.
(Unless you have unlimited time and plenty of cheap spares)

Also: Make SURE to properly map VEALS lambda delay.
It's the difference between works ~OK (with default values) or works awesome.

Save it out as a table once done: It doesn't auto-migrate to new projects (not part of the .msq you import)

[turbobaja]

Thanks for the input Pile. While most of your suggestions go right over my head at this point in my MS tuning experience, it does give me plenty to think about. Baby steps so far. Of course time and money are not limitless....I just wasted 2 weeks chasing a very irratic/backwards traveling TPS, so my time has been spent stumped on that instead of researching how to actually tune MS. Fixed the TPS problem finally and it's time to start moving forward .

[andy198712]

just gotta put it behind you now and enjoy the fun part

[turbobaja]

Here's what it's running with.

Just figured out how to generate AFR/VE tables

[Piledriver]

Leave the lags at 100 unless you have an actual noisy signal that needs cleaned up.

IMHO the "MAP averaging" should be the default setting, as it works noticeably better in 99% of cases.
(Number carefully extracted from thin air, but likely ~correct, based on my own experience and many folks on MSextra)

The other 1% probably need MS3, as the timed samples can vary by RPM and MAP.

MS2 default timed sample is one angle/window angle per cycle,(which is guaranteed to be non-optimal most of the time) so choose wisely.

It's best used at to help that on untunable spot at low RPM if you have an issue at idle or such with a single lung beast.
The max rate full cycle sampling/averaging reportedly works better in virtually all other cases.

I'm just trying to save you some pain and some gas.

[turbobaja]

I'm just trying to save you some pain and some gas.

Your help is very much appreciated, thank you for all your input. Guys like you make it possible for guys like me to successfully jump into tuning w/EFI. I have an idea of where I want things to be, it's just a matter of finding out what it takes to make that happen.

The "new" engine has about 15 mi. on it, so I did oil change #2 today and tightened up a couple valves. I pulled the sump plate off and inspected the screen, all was beautifully clean with just a few small clumps of molly assembly lube in the screen. I'll run a leak-down and cranking compression test on each cylinder once it clocks a few more miles to see how the rings are seating.

Mario gave me a HUGE headstart with the tune by setting it up on his own engine first. Since his engine is 1,585cc he simply added 10% more fuel to the tune to get me started and it worked really well. Today I used the table generators to build new fuel tables based on 1,775cc that pulls 35kpa @ idle, guessed 70hp @ 4,100rpm and 100ft/lbs @2,800. Then used the "Required Fuel Calculator" w/24lb/hr injectors and it dropped the constant from 18 where it'd been running good, down to 11.8. Sure enough it was dead lean on the cold start with a lope and stumble, running18:1...but still running . I bumped the fuel constant back up to 18 and it cleaned up and gave me a 13.5:1 cold idle. I need to verify fuel pressure @ idle and under load ASAP.

With the fully functional TPS I set the TPSdot to 200 and get a definite rich swing with every tip-in, a little too rich actually. It's also way too rich up near 100kpa near 4,000rpm @ 10:1 AFR and power falls off very quickly. This camshaft closes the intake valves earlier than the stock cam and has less duration too, it's freakin' tiny. But it pulls really good from about 2K on up with 12.5-13:1 AFR and should make a great driver for someone who's been happy with stock power/rev range thus far. Just need to work with the fuel curve a little more .

I also made my own ignition table by hand. It was the only way I could figure out how to manipulate the values within the load range I wanted to work with, one at a time. I went for a quicker advance ramp through the lower rpms and put a little "vacuum advance" in it where I knew I would be cruising with very low MAP in the upper rpms. With 7.7:1 static CR I set it to 32° @ full load above 2,200rpm. In the mid 40's by 2,600rpm with lower MAP.

The weather turned wet here lately, so driving w/out the aircleaner top wasn't an option. I decided to reinstall the 32mm stock trumpet for this new tune and see what happens with the lags turned all the way up to 100. Depending on gear/load/rpm it still won't read ~atmospheric @ WOT until it's near 4K rpm (haven't tested 4th gear on the freeway yet). It should be really easy to make back-to-back tests on the same hilly test loop with various intake configurations to see how they each affect MAP readings.

Can't wait to try out the VEAL feature soon