Fuel Economy and RPMs and VEs

[derekf]

1 week, 87 views and no responses?

Surely someone has an opinion, some knowledge, or at least a pointer at the right folks to ask? Or did I not really phrase the question well?

[Q ship]

1 week, 87 views and no responses?

Surely someone has an opinion, some knowledge, or at least a pointer at the right folks to ask? Or did I not really phrase the question well?

Derek, it's a good question and one that is actually vitally important to me. Once my Caprice is running again, it will become my daily commuter for a 200 mile/day trek. (And no, I will not consider anything smaller-I'm doing that now, and it sucks!).

First, I'd say you have to look at what GM is doing to get high 20's out of the C5 Vettes. Low RPM's at cruising speed, VERY advanced computer mapping, and an aerodynamic shape go a long way.

I have wondered a lot about what causes the most internal losses in an I.C. engine. Would a short stroke 327 be more efficient than a 383? A hydraulic roller cam would seem to be a given, as would a well dialed in EFI setup.

My ballpark plan? TKO tranny(500 or 600), 350ish displacement, and 3.08's. The boxieness of the car can't be helped, and I have been led to believe the drag figures aren't as horrible as they would seem.

I would be very interested to see this thread advance-everyone wants to talk about HP and timeslips, and the room gets very quiet when you start talking MPG.

[CHILI]

I've always heard that your greatest efficiency (best MPG) is at the highest vacuum reading. Mount a cheap vacuum guage in the car and play around. It would probably help if you have cruise.

I don't think it's just a factor of engine speeds. With my car I turn about 2100 RPMs at 80, but I'm only pulling around 10" of vacuum (big cam). My mileage sucks too for an EFI car with so much overdrive (TKO and a 3.08 rear).