FJ40 Aisin Jets

[PabloCruise]

Where do you live spectre?

I'm on the phone, so I don't get all the details I would if I were at the computer.
I'm up by Fort Collins area. My '74 Pig has 3fe, and my 40 has a Jim C rebuild on the factory Aisan.

You sound like you might work at NREL (currently or in the past)?

 

[subzali]

Problem with Aisan carbs (from my perspective, so take that for what it's worth), is that for almost every year throughout the 70s they were jetted a little differently each year, and, as it would seem, almost randomly. If you look at SOR's chart you'll notice this:
http://www.sor.com/sor/cat042d.tam

If you take, say, 1974 model year w/ EGR, the primary jet was supposedly 1.20. Being at altitude we would need smaller jets. So 1.18 is available, which might lean you out to where you need, but then it appears that no jets are available until you get down to 1.12. That might be too big of a jump. So you're going to end up compromising, and maybe just accepting the fact that you'll be running a little rich because there are no jets readily available to give you that perfect mixture. Toyota/Aisan just didn't make them.

In addition, when we go wheeling in this state, or even just driving from one end to the other, the elevation gains are so drastic that you'll be throwing off your "perfect" mixture. I'd rather be than sitting on the side of the road changing jets, because frankly my FJ40 doesn't care whether it's at 4,000 feet or 13,000 feet, it runs pretty much the same (I know that's not technically true, but it is practically true). I monitor my spark plugs and they're fine.

If you want to be real anal about it get a wide-band O2 sensor bung installed and hook up a laptop and monitor it while you're driving and adjust your jets accordingly. But these are Land Cruiser engines, I really don't think they care that much. Maybe a little, but not that much. The Aisan carbs weren't really designed to be that adjustable in the first place, unlike some other brands of carbs.

[/opinion]

 

[spectre6000]

I'm up in Coal Creek Canyon just under 8K', just below the north entrance to Golden Gate Canyon State Park. I used to work for the largest biodiesel refinery in the US and headed up an experimental feedstocks program that got canned when the economy (and the company) tanked. Presently I own a software startup.

According to the F Engine manual, the stock jets in the carbs are for sea level, and the "altitude" jets in the plugs are for 2,000M/6,600' (which is so perfect for me as it's dead in the middle of my daily commute!). As for changing year to year and availability and such, there are tiny ultra fine reamers you can get (or hopefully borrow) that will open a jet up, and you can braze some brass in there to close them up (which obviously requires re-reaming). It's best to have factory jets (especially because you always know what you're starting with), but if you have to ream them, be sure to mark them! There's nothing worse than dropping in a pair of jets only to find that one isn't what it's supposed to be (after checking everything else of course). Even with the factory recommendations, the second you deviate from the factory setup (to include the wear and tear unique to each engine) you alter the ideal jetting.

Tuning carbs is not difficult if you have the education and the tools ($$$). It can be pretty straight forward if you have all your senses, a few gauges, and a strong familiarity with the vehicle (the seat of the pants method). If there's any interest, I might be convinced to do a writeup on tuning carbs the über old school way. I'm not a carb tuning genius by any stretch, but I run 'em clean and strong!

 

[subzali]

How about this:
http://www.ih8mud.com/tech/carbinfo.php

People have reamed out jets and not re-stamped them (happened to a guy in RS recently, he found out after much head-scratching and frustration). That sucks.

 

[FJ40Jim]

Boring an engine .50mm O/s will have zero effect on carb settings.

Stock jetting changes every year in the 1970's as the emission limits were cranked down tighter each year. The carbs get more and more lean up through 1978. In 1979 the jetting goes all the way over to slightly rich (from dangerously lean) thanks to the addition of a cat converter.

So bear in mind that the stock jetting was wrong from the factory, and it's more wrong now due to RFG.

 

[Pighead]

Dang.

 

[PabloCruise]

What is RFG?

 

[subzali]

Re-formulated gas. You can do a Google search on it. We have it in the Front Range

 

[subzali]

Boring an engine .50mm O/s will have zero effect on carb settings.

Stock jetting changes every year in the 1970's as the emission limits were cranked down tighter each year. The carbs get more and more lean up through 1978. In 1979 the jetting goes all the way over to slightly rich (from dangerously lean) thanks to the addition of a cat converter.

So bear in mind that the stock jetting was wrong from the factory, and it's more wrong now due to RFG.

I believe other carb internals changed as well to work in concert with the different jet sizes (in fact I know some did, like the AAP and power valve). And I don't believe Toyota ever had jets in every size like I imagine are available for some carbs (maybe I'm wrong). Only some sizes.

 

[spectre6000]

Reformulated Gas (RFG) is gasoline, again with a different set of additives. The additives make it less volatile (it doesn't evaporate as quickly) and it burns more completely. The additives are essentially there to oxygenate the gas. The old school one was MBTE, but these days it's all ethanol. Which brings us back to where you're looking at a maximum net loss of 2-3% energy content. About the same delta as the increase in displacement being discussed. Ergo, still not worth re-jetting for.

That's not to say the factory jetting is completely accurate as the best case scenario, just that it's your best starting point (assuming stock configuration). If you're desmogged, find the factory recommended jets for the most similar setup to yours, then start tuning from there.

 

[PabloCruise]

I'm up in Coal Creek Canyon just under 8K', just below the north entrance to Golden Gate Canyon State Park. I used to work for the largest biodiesel refinery in the US and headed up an experimental feedstocks program that got canned when the economy (and the company) tanked. Presently I own a software startup.

Tuning carbs is not difficult if you have the education and the tools ($$$). It can be pretty straight forward if you have all your senses, a few gauges, and a strong familiarity with the vehicle (the seat of the pants method). If there's any interest, I might be convinced to do a writeup on tuning carbs the über old school way. I'm not a carb tuning genius by any stretch, but I run 'em clean and strong!

Very cool spectre!
I found my 40, and bought it from the original owner, out by White Ranch Open Space Park, not too far from where you are.

Put me down as interested in your carb tuning write-up!

 

[Nhirsch]

I've run my 1980 with the stock sea-level jets (and with the HAC system intact) up to 13,000' and it did just fine.

What's your stock jets size? Thanks

 

[1911]

What's your stock jets size? Thanks

It's been so long since I had my carb apart, that I don't remember, sorry!