MJ, doing its part keeping our air clean

[fiatslug87]

Just took the '88 in for its biennial smog test, INCREDIBLE numbers!!! 

[Jesse J]

that's crazy. 

[Eagle]

Back in the day (as the saying goes), the Jeep 4.0L engine was considered to be a low-emission engine. For all the advances they've made in emissions technology in recent years, much of it has been through add-ons and gimmicks. The parent of the 4.0L (and 2.5L) dates back to AMC in 1964.

 

So here's a true story: During the pony car era, I owned a few Javelins and 2-seat AMXs. I was friends with the son of a local AMC dealership, who sort of semi "sponsored" our chapter of the Javelin/AMX Sports car Club. So I spent a lot of time hanging out in their shop. At the time I also owned a 1954 Hudson Hornet. (For those who don't remember, AMC was created by the merger of Hudson and Nash.) Just for grins and giggles, one day I drove the Hudson down to the shop and we decided to hook it up to the emissions testing equipment. The Hudson, of course, had NO emissions equipment whatsoever. My '68 Javelin, on the other hand, had an air pump that shot fresh air at the exhaust manifold to help burn whatever was coming out of the engine that hadn't burned in the cylinders, and it had a throttle delay thingie that didn't allow the throttle plate in the carburetor to close fast, because fast closing caused the engine to run rich for a second or two.

 

The Hudson, which was at the time about 16 years old and had over 100,000 miles on it, tested cleaner than the nearly brand new Javelin, with all the gimmickry.

 

One reason is that all the Hudson engines were long stroke engines. Most (maybe all) V8s are short stroke -- the bore diameter is larger than the stroke. Long stroke engines are inherently more efficient than short stroke engines.

 

[89 MJ]

1 hour ago, Eagle said:

One reason is that all the Hudson engines were long stroke engines. Most (maybe all) V8s are short stroke -- the bore diameter is larger than the stroke. Long stroke engines are inherently more efficient than short stroke engines.

 

I love learning about engines. Do you know some of the science behind this? If so, please explain.

[fiatslug87]

If you have not read this yet, it's worth your time. https://www.fourwheeler.com/how-to/engine/129-0711-1987-2006-jeep-40l-inline-six/#:~:text=Like most modern engines%2C the,is smaller than the stroke.

[Eagle]

23 hours ago, fiatslug87 said:

If you have not read this yet, it's worth your time. https://www.fourwheeler.com/how-to/engine/129-0711-1987-2006-jeep-40l-inline-six/#:~:text=Like most modern engines%2C the,is smaller than the stroke.

 

That's a good intro to the stroker engines.