A15 Carburetor

[JustinB]

Soon I'll be done putting my A15 back together (i hope). I was wondering if anyone knows what carburetor I need to get. I was just going to use the one that's on the A14 that's in my car, but I'm pretty sure it needs rebuilt anyway. I want to keep the great gas mileage, but I wouldn't mind a little power if I decide to put my foot into it. Let me know what you guy's have done, and where I should get one, also. Thanks.

[DRIVEN]

Kits are around $20. Ebay carbs are around $100.

If it were mine, I'd bolt on the one you have first just to see how it runs. It may be ok with a quick cleaning.

[ggzilla]

A14 and A15 same year carbs are identical. Give it a try.

It will give you the best fuel economy and a little power when you put your foot into it.

[JustinB]

I suppose there's no reason not to. if it doesnt work i can replace it afterward

[BluEvo210]

The factory manual specified the same carb for all A-series engines (at least in my 1980 manual), but I'm pretty sure it specified different jets for each displacement. Not radically different, but an A15 might run lean with an A14 carb.

 

Then again, I think these engines have such low compression it probably takes more than running a little lean to make them knock.

[ggzilla]

Wrong. They are no low-compression engines. They have a healthy 9.5:1 ratio most of them.

 

The A15 carb is the leanest of the bunch. The 1980 A12A carb has different size venturis. The manual list the carburetor type as the same (DCH306), but there are different ones. The A15 for 1980 is DCH306-100 which I'm running on my A12 right now. The A12 carb is much richer.

[BluEvo210]

Wrong. They are no low-compression engines. They have a healthy 9.5:1 ratio most of them.

 

Maybe it varies by year or location. I distinctly remember my 1980 manual saying my A14 had an 8.9:1 ratio. That's pretty low for an engine with an aluminum cylinder head.

[ggzilla]

Even 8.9:1 is not considered low. Most 1970s american engines were in the 8.5:1 range.

What is low? Later Model Ts were about 5:1.

[BluEvo210]

Model T? I'm starting to think you're just being contrary.

My perspective comes from a 240SX that runs on regular unleaded with 9.5 compression, and an Evo that puts 21psi of boost through 9.0 compression. That's 1.5 atmospheres of boost, with more compression than my A14.

 

 

[JasonGW]

Wrong. They are no low-compression engines. They have a healthy 9.5:1 ratio most of them.

 

The A15 carb is the leanest of the bunch. The 1980 A12A carb has different size venturis. The manual list the carburetor type as the same (DCH306), but there are different ones. The A15 for 1980 is DCH306-100 which I'm running on my A12 right now. The A12 carb is much richer.

 

So leaner vs richer, what's the net effect in fuel economy/power on an A14 or A15? :)

[ggzilla]

The leaner carbs get better fuel economy but have some driveability issues (not as smooth). And they depend on the entire system working including spark timing, heated air intake working etc because they are jetted close to the edge.

 

The richer carbs are more forgiving of state-of-tune, and generally make a bit more HP on partial throttle (at full throttle, they all run a bit rich). I dunno how they'd work on an A14/A15 because all the A14/A15 here in USA were jetted lean and few bother to rejet the stock carb. Instead they fit a baseline Weber on it and live with the poor MPG because it runs good. If you professionally tune a Weber you can get excellent fuel economy and power both. You don't have to pay an expert, you can self-tune using old fashioned methods or using a wide-band O2 sensor. Or with the stock carb, just fit the same jets they used in japan, which are just a couple sizes bigger.

[2doorTurd]

Or you could sacrifice a few mpg and get an adapter to fit an L series carb which has great response, and vacuum secondary. Vacuum secondary is better for street driven daily car IMO because the carb only opens up as much as the engine will pull.

 

Better full throttle performance. And if jetted correctly, great response and similar mpg.