Quote:
Originally Posted by Bullyveldt
I notice that exact same thing
Now I had a chance to see what drafting is all about the other day. Well yesterday. I was in the slow lane driving and a dump truck passed me but realized he would be losing speed for the upcoming hill and changed lanes in front of me. Well I was reading 10Hg on the flat part of the road and when he pulled in front of me, say 5 car lengths, the vacuum began to rise and sat at 15 Hg with the truck in front of me. I figured he was too far ahead to obtain a measurable difference from his wake but I did, so I moved a bit closer after the hill, which needed less throttle then usual with him in front of me, and the vacuum read 15-18Hg. His exit was approaching and he merged off the road and my vacuum then dropped to 10-12Hg almost imediatly after he merged and I had to tip the throttle a bit to maintain my speed, approx 85km/h.
Just another observation
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I've not tried drafting trucks in a long time, but I have also noticed that when one gets in front of me my engine vacuum will increase several In/Hg at distances up to 200-300 feet. Next time I go on a road trip I may see if I can find a truck that isn't driving but 60-65 mph and draft him at a couple hundred feet which is about 10-12 car lengths. That should be a good safety cushion.