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ATT videos

Big T said:
Technically the 6.5 had a soot trap. There's no catalyst in it.
Click to expand...

The emissions sticker says "catalyst" on my 1995. The kitty plugs up with soot. IMO this is where the "joke" of "soot trap" came from.

"So how do precups affect performance? And why do some hurt and others help?"

The 6.5 is a indirect injection engine. The combustion starts in the precup that is in the heads with the injector and glow plug. The flame then travels through the precup throat into the cylinder. The swirl makes for high MPG on the low tech injection equipment available 30+ years ago.

There is a fine line between swirl, MPG, and the amount of power you can get out of them. Emissions, smoke, swirl speed in the combustion chamber are all forgotten factors. Bottom line is small precups generally get the best MPG with the lowest power. Turbo application is a different ballgame because you can only get so much air through that small hole in a specific time. I read about the fuel charge possibly separating out at high speed/power levels.

Precups are really small for econo engines. The smallest were on P vans for chip delivery like at 120 HP Naturally Aspirated, NA.
Next size up you have NA 6.2 precups in several flavors.
Slightly larger are military 6.2 NA precups.
Larger are 6.5 NA precups.
Then you have several flavors of larger yet 6.5 turbo precups. The last design was the diamond precups.
Next you have some experimenting with even larger machined out precups.

I ran a 6.2 NA engine in place of my blown 6.5. With the GM3 I couldn't run much fuel to notice the precup difference. With a larger turbo and more fuel the small 6.2 NA precups become an issue. Same setup on my 1993 with the A Team Turbo having 6.5 NA precups doesn't have the same smoke and sluggish issues. I have found the only way to clean up 6.2 precups is to through a lot of boost at it.

Pics:
http://www.thetruckstop.us/forum/showthread.php?29211-A-little-6-5-turbo-NA-and-6-2-precup-info
 
Three more videos in cool weather:

 
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Just some fun I had back in the day. Was going through old folders and found this. Never uploaded it before. Quality really suffered on the video when uploading it but the sound is the same. You can hear the scream from the exhaust really well. Sounds angry at low rpm's haha enjoy
 
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