Topic: H8PVMNT's Aisan 22r Carb Tech /Study

[H8PVMNT]

So now we have this free flowing setup and we have shed a whole bunch of vac line spaghetti.  When you hit the secondary's there is an audible sucking noise.  Actually it's pretty danged loud when you are in it. The acceleration was noticeably better with the open filter but it felt whispy and lean in the upper RPMs.  So I swapped my main jet from the 116 to a 120 Hitachi motorcycle carb main jet from JetsRUs and tweaked my secondary butterfly opening a bit so it gets perfect vertical at wide open throttle. Adjusting the butterfly relationship is a combination of a screw that you'll figure out in the throttle linkage and bending the little tab that hits the secondary (from the zip tie mod earlier in this thread ).   It feels solid all the way up to 5,200 now.   Not sure if I'm totally dialed in yet but now this thing really gets it on.  This morning I was able to advance my timing a bit more with no pinging.  Pulled one of my test hills 7 mph faster than usual and went 80 all the way to work in 5th gear.

I think I'm getting there .

[Gnarly4X]

Geezz... I LOVE this stuff!!! 

Correct me if I'm wrong, but you could not do this type of "tweaking" with a 22RE without, perhaps, a MegaSquirt and some serious programming?


Gnarls.

[H8PVMNT [OP]]

Geezz... I LOVE this stuff!!! 

Correct me if I'm wrong, but you could not do this type of "tweaking" with a 22RE without, perhaps, a MegaSquirt and some serious programming?


Gnarls.

You can pick your friends, and you can pick your nose, but you can't pick your friend's nose.

I tried a few of the cheap things with the 22RE like MAF tuning and intake and got nowhere near the changes I have experienced with this thing.

[H8PVMNT [OP]]

OK now I will take a break on tuning and discuss a couple off road mods. The Aisan carb is a pretty good off road carb all ready. I have heard of guys lowering the float and using a fuel pressure regulator with some success.  This seems to work well but I think these methods are band-aids for design issues that can be addressed with a couple of small mods.  I am running stock float settings and stock fuel pressure right off the pump.

The main issues I found that the Aisan carb has are with very, very, extremely steep angles climbing due to the float bowl vent dumping fuel into the carb and one lesser realized issue with the passenger side lay over due to the "Outer Vent Control Valve" passages also dumping fuel.

My solution for the float bowl vent is the simple run a line to a charcoal canister method.  Here is on my new filter but it's even easier on the stock filter box.  Now we can be pretty much vertical with no flooding.

[H8PVMNT [OP]]

Here is the "Outer Vent Control Valve".  It is made to vent gas fumes from the bowl and the carb and has a little plunger that goes in and out when it has 12V to it or not.  Venting vapors to a charcoal canister is not necessarily a bad thing but the problem is with the little hole in the passenger side of the inner carb casting. Fuel dribbles through this hole from the float bowl when you are laid over at an angle on your passenger side and it will flood the carb.

You can see the passages in the pics below and I also point to where the little problem hole is (last pic).

The solution I found was to simply block the flat passage right on top of the float bowl (2nd pic down) by jamming a bit of squished fuel hose in there flat.  This way it doesn't really interfere with the valve plunger that lives in the in the round hole so you can still close it all up by putting the valve back on.  A guy could make a block off plate if you wanted.  I suppose you could just JB weld the thing shut too.

Anyway, now we can lay way over on our drivers and passengers side with no flooding!

[_HOIST_]

Subscribed. Excellent thread. Keep it up for all us still using decades old technology!

[helipilot77]

The Asian carb on my 4wd Tercel has a bad diaphragm on the AAP (Auxiliary Air Pump) which causes it to idle poorly at cold temperatures before it has warmed up. I have a replacement that I've been meaning to install, but I just haven't yet. I this thread.

[H8PVMNT [OP]]

The Asian carb on my 4wd Tercel has a bad diaphragm on the AAP (Auxiliary Air Pump) which causes it to idle poorly at cold temperatures before it has warmed up. I have a replacement that I've been meaning to install, but I just haven't yet. I this thread.

Hey if your Tercel has the carb with the vacuum secondary check out the mod where they flip the secondary diaphragm and/or spring around backwards. I guess it really wakes them up .  There is a youtube of it floating around.  I don't want to post it here because it doesn't pertain to the 22R carb at all and it would really confuse people.

[H8PVMNT [OP]]

I've been asked what is the minimum I need to make it run.  Here is a sketch of what I am running right now.  This is probably a little more than the bare minimum.

-I like the HAC (High Altitude Compensator), which adjusts timing and mixture for altitude.  This is probably the main reason I wanted to run the stock carb in the first place. It's a little hard to figure out but the Haynes manual has a good diagram I posted before on page 1. Three lines hook to ports at the top of the carb body and one tees into the vac line that goes to the second advance port on your distributor. There is a check valve on the carb side of the tee for some reason.

-The AAP (Auxiliary Accelerator Pump) adds a bit more fuel when the engine is cold so it doesn't run as stupid before it warms up.  I just don't think that's a bad thing.  This fills with fuel when it is pulled on by manifold vac through the TVSV, or you might have a BVSV on a later model.  These are just a temperature operated vac switch that swaps from one port the other when the engine warms up.  The cold/on side works the AAP and the choke breaker and the hot/on side works the choke opener.  Basically you want to hook your AAP and manifold vac to the two ports that you can blow through when the switch is cold. You really want to check which ports on the TVSV or BVSV are open when the thing is cold.  If you get the vac lines wrong, your AAP will be on all the time wasting gas. My AAP is hooked to the top port, manifold to the middle port and he bottom one is capped off since I am running a manual choke and the choke opener doesn't exist.

-Then you have the vac advance to the advance port on the carb and the secondary advance if equipped.

-Then we have two charcoal canisters, one for the fuel tank vent and one for the Outer Vent Control Valve and our float bowl vent, which I teed into the line from the Outer Vent Control Valve.  These canisters typically get vac from an electric operated vac switch on the 4WD model which seems to be controlled by the vehicle speed sensor.  I deleted the switch and hooked them to the appropriate vac port on the carb like in the 2WD diagrams. I don't think the vac switch was hurting anything, but since I am trying to delete things I thought I might as well go for it.  I have had no ill effects so far.

Arguably you could ditch the HAC and leave the AAP unhooked and just run ported and manifold vac to your distributor and call it good.  I guess you would still need one vac line to a charcoal canister for the tank vent. 

In summary, you don't need much to make the Aisan carb run properly after all.

[helipilot77]

Hey if your Tercel has the carb with the vacuum secondary check out the mod where they flip the secondary diaphragm and/or spring around backwards. I guess it really wakes them up .  There is a youtube of it floating around.  I don't want to post it here because it doesn't pertain to the 22R carb at all and it would really confuse people.

Found the video you mentioned. They all seem to refer to the 4A-c which is the big brother to my 3A-c. I know that the AISIN carb on my 3A-c has vacuum operated secondaries. I bet it would work I just wonder how it will affect fuel economy? Thanks for the tip! I might just give it a try. Of course it will never be as powerful as this:

[Gnarly4X]

Hey H8PVMNT,

Not to change the topic or digress, and could be another new thread…  Distributor Curve?

I realize you have played with ignition timing.  Have you experimented with the distributor curve on carb disty?

Ignition timing and properly curving a distributor is critical to getting peak performance.

Just curious. 

Gnarls. 

[H8PVMNT [OP]]

Hey H8PVMNT,

Not to change the topic or digress, and could be another new thread…  Distributor Curve?

I realize you have played with ignition timing.  Have you experimented with the distributor curve on carb disty?

Ignition timing and properly curving a distributor is critical to getting peak performance.

Just curious. 

Gnarls. 

So far I have used a Celica distributor that had slightly less total advance and some lighter springs than the truck one.  It did make it a bit more eager.  That was a re-manned distributor that seized up and now I am using a stock 20R pickup distributor.  It honestly feels like a better match overall but I think there is more to be had there if I learn how to do it.

I would like to play with advance curve again but I need to find a good source for weights and springs.

[H8PVMNT [OP]]

Here is a good "What do I run" vac layout that would be good for someone running the stock choke parts and a stock filter box. This one is less the HAC too.  It's pretty simple and has the basics but not much else.

[H8PVMNT [OP]]

This thing is really feeling nice.  Way better acceleration.  I would describe it as buttery smooth good pull throughout the rpm range. 2nd and 3rd gear I would say it could roll right with my 3RZ.

Hold it's own against the head winds better too.  After getting the performance closer to what I want I seem to be loosing economy though.  My commute has a couple  good hill pulls and almost always a strong headwind at least one way, so it's not nice highway driving, but I was getting 14.5 mpg most of the winter and now I'm down to 12.5 after switching from the 116 to the 120 main jet.  The Aisan carb may just end up being a porky pig when you get it dialed in for performance.  This may be the downfall.  Can't have it all I guess .

I'm going to try out the 118 jet for a few days and see if I can still get the power but improve the mileage a bit.

[H8PVMNT [OP]]

Success!  A quick swap the 118 jet and a drive it like you stole it run out to my buddy we buy hay from and I got 14.6 mpg!  I can live with that. The best part is the thing has even MORE balls on the 118 jet.  I haven't read plugs yet but I'm guessing the 118 is on the lean end of perfection since the 116 wouldn't get top end and the 120 porked fuel.

Carb is fun .

[H8PVMNT [OP]]

Last check on a very responsibly driven 45 miles got me 10 mpg .  I am going to run about 3 commutes and check again.  I got nearly 15 driving like an idiot climbing grades and pushing head winds.  It may be that you have to drive like a dummy to get good fuel economy with this setup.  It also may be that when you finally get the Aisan carb dialed in for decent power that it is a fuel hog.

I will check my AAP this week just in case it's messed up so I don't jump to conclusions. 

Maybe to get decent MPG I will have to put the stock filter setup back on.  I'd sure love to keep this thing opened up though because it is FUN to drive like this.

[emsvitil]

Set up the primary bbl for economy and secondary bbl for power........

[Gnarly4X]

Set up the primary bbl for economy and secondary bbl for power........

This type of carb tuning is possible.... but if you go too lean on the fuel, the engine may not feel responsive while running with just the primaries.  You can go bigger on the jetting with the secondaries, but again... too much fuel without added air and you will most likely just burn more fuel and not gain any added power.

Ideally you want to have enough air to burn all the fuel in order to reach AFR and stoichiometric mixture.

Without a wide band O2 sensor or some kind data logger to record the AF during testing... from low RPM driving to WOT, you may be guessing, or going by your butt dyno - which may provide some interesting feedback.

Remember you are at elevation above sea level, so your air has less oxygen. Power loss in your engine will be between 3 and 4 HP for every 1,000 feet above sea level.  If you are running around 4,000 feet above sea level, your engine will see about 12 to 16 HP loss.

Does this carb have vacuum operated secondaries or total manual with throttle linkage control?

How can you get an accurate MPG reading with only 45 miles of driving?

That's just my opinion - it may be worthless.

Gnarls.

[emsvitil]

Is there the equivalent of a power valve or metering rod on the primary bbl for enrichment when only on the primary bbl?

[Gnarly4X]

Hey H8PVMNT,

Have you been able to do a compression test?  I'm am very curious.

At what RPM are you feeling peak pull?

At what RPM are you at "cruise"?.... final gear and at your typical highway MPH?

What fuel octane is performing the best combination with ignition timing?

Gnarls.

[H8PVMNT [OP]]

Hey H8PVMNT,

Have you been able to do a compression test?  I'm am very curious.

At what RPM are you feeling peak pull?

At what RPM are you at "cruise"?.... final gear and at your typical highway MPH?

What fuel octane is performing the best combination with ignition timing?

Gnarls.

I have not done a compression test, I don't have the tools, but I did a pristine rebuild about 40K miles ago and the cylinder walls looks perfect when I had the head off so I wasn't too worried about it.  I understand I am taking a bit for granted here, but I have got up to about 17 mpg with this setup in the very recent past with the stock intake and have had nothing happen that would mess up compression since then.  All the changes are intake and tuning related since then.  Chasing un-claimed throttle response and horse power you know .

At this state of tune I get a really nice pull from about 2,000 rpms all the way to about 4,200, then it still pulls pretty good to about 5,200.  I would estimate "peak" torque is in a nice broad patch from 3,200 to about 4,000.

I am running 5.29 gears and 35s, my cruising speed on my commute is between 3,200 and 3,500, usually in 5th gear, between 70 an 75 mph.  Going slower at less rpms gets me less gas mileage, oddly enough.

I have been striving to run on 87 octane.  With the leaner jet I had to run colder plugs, with this jet I can run the stock plugs on 87 octane and I can advance my timing a bit more where I like with no detonation problems.

I will read the plugs today after a good pull.

[H8PVMNT [OP]]

Set up the primary bbl for economy and secondary bbl for power........

Well that's the thing you can get different main jets, which affect the primary side, but that's about it other than tuning the timing of the secondaries.  I have some more carbs I can take apart and see if they have different sized needle/seat bits but that's all there is available.

I am really happy with the power at this point but 10-12 mpg is not going to cut it for me. I would rather sacrifice a bit of power and pick up 3-4 mpg if I have to choose.

[H8PVMNT [OP]]

Does this carb have vacuum operated secondaries or total manual with throttle linkage control?

How can you get an accurate MPG reading with only 45 miles of driving?

That's just my opinion - it may be worthless.

Gnarls.

The 22r carb is mechanical secondaries with a flap that pulls up the secondary needle when it opens from vac.  I have considered messing around with the 20r carb, it has vacuum secondaries and despite the small 190 cfm size I have never been disappointed in it on my 20r pickup and that thing got 17-22 mpg with bad gearing and oversized tires all loaded down with camping gear or fire wood.

Yes you are right on the 45 miles of driving.  It is the same exact 45 miles of driving every day but to get a real base line I need a tank of gas or at least 10 gallons.  I wondered about expansion with temperature and all that with the top offs fooling my numbers.  I will do that the next few days.

Regardless of weather this thing can get economy and power at the same time I feel I have at least proven that the Aisan carb does have a lot more potential for performance and it will certainly run smooth without all the extra stuff on it.  I feel the performance I am getting is right there with or maybe even just a bit better than my buddy's Weber 32/36.  The only advantage I can see with the Weber at this point is that you can tune everything and all the parts are readily available.  I don't want to go down that road with this thread though.  I can see a twin sister thread to this one comparing the two coming soon if I can find a deal on one though .

[H8PVMNT [OP]]

Is there the equivalent of a power valve or metering rod on the primary bbl for enrichment when only on the primary bbl?

Just the main jet and when the secondaries hit is all I can change at this point.  There is a power valve but I haven't found any source for different sizes.  Might be able to change a spring on it.  Doesn't mean it can't be done, I just haven't found it yet.  The main limitation of this carb is the parts you can't get to make changes to it.  I think it is pretty well matched to the restrictive stock intake parts and when you mess with that the aspects of the carb you can't tune become more of a problem.

[H8PVMNT [OP]]

I thought this was pretty cool...

[H8PVMNT [OP]]

Took a look at my plugs after a good WOT pull.  Mixture actually read a little on the lean side but no sign of detonation. I typically play with timing until it feels right without pinging.  I might have had my timing a little advanced.  Pulled my timing back to 0 and reset the idle mixture for a nice 750 rpm idle.  I'm going to start from scratch and top off the tank, see what happens. 

[emsvitil]

Secondary:

Fiddling with the metering rod will fiddle with the AF for the secondary;  (diagram above)

Primary:

This seems to show a 'jet' as part of the power valve:

So you'd adjust the primary jet for economy, then the power jet for primary power.

[H8PVMNT [OP]]

Well I think I can adjust the height of the secondary metering rod at it's limit, in other words make it come out of the jet further or less, with a 5.5mm wrench and a tiny screw driver.  I plan on messing with that as soon as I can find a 5.5mm wrench. I have never successfully removed a secondary jet, for some reason they at all seized in there.

I had to go out and look at my loose carb to weigh in on the power valve.  So far every rebuild kit I've had will have a power valve/jet but it's not like you have any options there unless we can find another set of carb parts that shares the same power valve but has different jet sizes. Maybe we could drill it out? I need to take it apart again.

This is where we run into the limits of tuning the Aisan carb.  Changing main jets yields significant changes but I haven't figured out how to do much else.

[Gnarly4X]

I love this stuff!!

Your passion for “tweaking” is awesome, and then taking your time to share it is more awesome.. THANK YOU! 
 
If “micro-tuning” was a 6-pack of Bud Light, you’d be a Budweiser delivery truck!!

I think you may be reaching the boundaries of “micro-tuning”. 

I’m a little bit puzzled about your ignition timing and cam timing….. 

Generally, and what is typically changed/adjusted at elevations above sea level for naturally aspirated carb’d engines, to compensate for the lower oxygen and air density – slower combustion time - is advancing the ignition timing and advancing the cam timing.  Raising the compression also seems to help with the loss of power at elevation.

So you have adjusted your ignition timing back to zero and your cam timing is at 1 degree retarded?  I’m interested in that adjustment and why that feels better to your butt dyno ?

Gnarls.

[Gnarly4X]

Congratulations!....