Great awful commute fuel economy
 

Car is running great since I did the head gasket job, flushed my cooling system, installed 15" wheels for the taller gearing, and made the rear wheels quite smooth to the airflow.

I drove a 130 Mi round-trip yesterday for work that averaged 64 miles per gallon. But what was most fun about it was that I did very little engine off coasting. I did at least 50 miles of steady throttle cruising. I did some engine on coasting. And my EOC was mostly in the stop/go LA traffic.

Before the repairs and the new wheels, I had noticed a breaking point in the fifth gear cruising characteristics of the car that looked like this: it wasn't possible to stay at or over 60 miles per gallon if I was at or over 40% engine load and it also wasn't possible to stay under 40% load if I was trying to travel over 55 miles per hour. Now I can do 60 miles per hour at 60 miles per gallon at 45% load. 40% load has become the breaking point for 70 miles per gallon.

Looking good! I wish my car did that well on the highway... so all that you done was the head gasket and taller tires?

That's all that changed recently, but the car is moderately, some might say heavily, modified. I cruise 60 mph at 1900 rpms and kill it. There are dudes that woukd call that lugging the engine, but they suffer from an imprecise definition of lugging. :turtle:

I don’t call that lugging, I call it good tall gearing... on two lane roads I P&G up to 60(2200RPM) and back down to 40(~1500 RPM)... on the freeway I cruise at 75-ish at just under 3000... my speedo is uncalibrated for my tire size increase of 5.3% so I’m sure I’m driving faster than I need to... however, on the topic of lugging, I’ll use engine power from as low as 1000 RPM in 5th gear, and from as low as ~800 in 4th and down... I feel that the key is to slowly roll onto the throttle and only use 40-50% load until you’re under way and over 1000

It's all about what's on the brake specific fuel consumption map. Your method might work really well. I think there's a map out there for a 1.9 liter Saturn engine. Have you seen it? I left a something out of my response in moment ago. My wheels are more aero, probably. I replaced open spoked VX 13" wheels with 15" 7 hole MINI rims, but I blanked the seven holes for a "smooth" surface. Here it is before I put the wheel skirt back on:
http://ecomodder.com/forum/attachmen...1&d=1523916431

I thought it looked a little better than just using moon eyes.

EDIT: here it is I'll upload it for you if you haven't seen it:

http://ecomodder.com/wiki/images/e/e...FC_cleaned.png

Well of course you are getting better mpg now, your valvetrain was probably worn, now it's basically a brand new head with way less leakdown. Also, I'm going to assume you had the head shaved to make it flat again? If so, that's also a small compression bump. Not much, but everything counts I guess.

Yes to all of this. I was a little disappointed at the machinist didn't seem to do a check for warpage before flattening. But he did a great job. I'd recommend them to anyone. But you asking these questions reminded me that there's still another modification that I forgot to mention in the original post for this thread. I set the valve lash in a way that was meant to improve internal EGR. The valve lash is still all set within specs but the exhaust valves are open for as little as possible within spec and the intake valves are open for as long as possible within spec.

I wish that were my BSFC map, but I have the 2.2L Ecotec that’s also found in the Malibu, Cobalt, Cavalier, etc...

Ah. I also don't have a map for my specific engine, either. But I always do pulses at 75%-80% load in the best gear to keep me 1700-2200 RPM (sometimes 1500 and sometimes 2500). There is a general lesson from reading multiple BSFC maps for NA gasoline engines and that is that the 75% load, maybe 80%, from 1700 RPM, maybe 1500, up to maybe 2500 RPM is the area of best BSFC. And if that is not the exact best in my car, it would be damned close. Then I can experiment.

I think the general lesson might be that you could be leaving some potential untapped with the 40-50% load, high gear acceleration you described. On the map I posted above--and some others--50% load at 1000 rpm is in the 325 band, whereas if you down shifted and hit 75% load at maybe 2500 rpm you would be in the 250 island. That is maybe 20% more efficient. I got that right, yes?

I only intentionally limit load when under 1000RPM in 5th gear, as the engine doesn’t seem to like it and just shakes/vibrates... sometimes when I’m losing speed on a hill in 5th, with foot on floor, I’ll let it drop to 900 or so, IF I’m close to the top and I know I’ll be able to let off soon... sometimes when taking off really gently downhill, I’ll be in 4th gear as early as 10-12mph(600RPM) but I limit load st that low of engine speed

Anytime else that I’m accelerating and over 1k, I usually flatten the pedal, and UG reports 78-82% load...yes I do know that if I backed off a little I could accelerate in closed loop... sometimes I go the extra and can get better mileage hit usually I don’t