GM Truck Club Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
Hi I am new here and only joined to ask this question. I am currently in flight school and in our planes there is a lever to adjust the mixture throughout flight (full rich take off/land and lean for cruise). This would be so convenient for my +-4mpg 383 stroker and 3 speed. I was thinking like a choke but in the fuel line right before the carb and not have it exceed a certain point to not harm the engine? Is this type of thing even possible or have been done before?
 

Attachments

·
Registered
Joined
·
718 Posts
We call it HLC (Hiway Lean Cruise) but it's done on an electronically controlled system. When cruising above 40 or 45 MPH and light throttle it will lean out the AFR (Air Fuel Ratio) from Stoich ~14.7 to 16+, using an O2 sensor, depending on speed and MAP (Manifold Absolute Pressure). You can get up to 10% increase in MPGs ave. I don't have any idea how to do it with a carburetor.

Edit: I had a brain fart, the AFR is based on MAP not TPS.
 

·
Registered
Joined
·
3,226 Posts
Thanks for the explanation Peter, I was wondering what that was. Now I know.

Al
 

·
Registered
Joined
·
718 Posts
No Problem, I forgot to mention HLC also advances the timing. In this table it adds SA based on the MAP (Manifold Absolute Pressure) sensor so, I'm usually ~40 - 42* advanced. When KPa goes higher, your throttle is more open so, when it gets to 100 you're at WOT so, you don't want that much timing, you'll get KCs (Knock Counts)

167831
 

·
Registered
Joined
·
718 Posts
FYI, in case anyone's interested here's what HLC uses to adjust AFR.


167832
 
1 - 5 of 5 Posts
Top