Terminal F/E; What's yours?!

[brucepick]

If you drive 60 or 65 you will find the others that are going that speed.

Also, just ask yourself if those 70 mph people are paying for the gas you need to drive at that speed. I don't think so.

[nbleak21]

Driving 60mph, I can't stay in lean burn under up hill loads, netting me sometimes as little as 20mpg vs 65-70 where I only drop to a min. 28mpg. Traveling the interstate, I generally pass only 2-3 vehicles (speed limit is 70) in my 60mi commute. Usually those are semi trucks struggling to get up hills, which is the last thing I want to be behind.

[Ecky]

Here's mine:

Honda B18B1 engine, B16A transmission (very short)

Idle, 800rpm
0.23G/H

Neutral, 3900rpm
~1.05G/H

70MPH, 3900rpm
~2.2G/H

So even running at 3900rpm I could achieve a theoretical 67MPG at 70mph. Looks like there's a lot of room for improvement aerodynamically in my car.

[user removed]

I once posted to someone on some forum that my first gen 2002 Insight used the same amount of fuel going 40 MPH as his V8 pickup truck did idling. Not sure he got the drift of my meaning. It also looks like you need twice as much fuel to maintain 70 MPH as the engine uses running at the same RPM with no load.

Best testament to higher overall final drive ratio I think I have seen.

I think the last car I owned that revved that high at that speed was an 82 280ZX Turbo with an automatic tranny. Needed a 5 speed badly with a 3.54 rear axle ratio and a .75 OD 5th.

regards
Mech

[Ecky]

Crazy thing is, this is a 5 speed. The transmission was originally mated with an engine with a redline of 8200rpm and 2 cam profiles. The gear ratios were close to allow that engine to stay in the upper cam profile (engages at 5400rpm) when accelerating. At all reasonable highway speeds it was still able to cruise in the lower cam profile.

The new engine has a larger displacement (due to much longer stroke), redlines at 6800 and has a very simple head, so this tranny isn't really suited for it. I should've replaced the transmission when I had the engine dropped in but I didn't know much about cars at the time.

[brucepick]

nbleak21,
Ahh, Lean Burn Honda powered cars. I spent quite a bit of time figuring mine out.

Mine had a requirement of about 63 mph or better (in fifth gear) for lean burn. That was a minimum of about 2300-2400 rpm. Interstate upgrades would defeat lean burn due to speed lost while climbing.

I use a ScanGauge to monitor engine status: Lean Burn status, load, temperatures. Do you have one?

And I discovered - after 2.5 years of lean burn frustration - that 2 ounces of Marvel Mystery Oil per ten gallons gas enables lean burn down to about 1900 rpm, or about 45-46 mph in fifth gear in my car.

It takes most of a tank before you start seeing clear improvement. After 3-4 tanks you will likely have low speed lean burn available as long as the other engine parameters are within range. I'd recommend 4 oz per ten gallons the first time, that's the recommendation on the bottle. After that you can go down to two oz per ten gallons.

If you're thinking this can't make sense, do a search on this site for marvel mystery oil and read the posts by the other Honda lean burn owners who have tested it. Try 2-3 tanks.

[nbleak21]

Originally Posted by brucepick

nbleak21,
Ahh, Lean Burn Honda powered cars. I spent quite a bit of time figuring mine out.

Mine had a requirement of about 63 mph or better (in fifth gear) for lean burn. That was a minimum of about 2300-2400 rpm. Interstate upgrades would defeat lean burn due to speed lost while climbing.

I use a ScanGauge to monitor engine status: Lean Burn status, load, temperatures. Do you have one?

And I discovered - after 2.5 years of lean burn frustration - that 2 ounces of Marvel Mystery Oil per ten gallons gas enables lean burn down to about 1900 rpm, or about 45-46 mph in fifth gear in my car.

I am actually artificially forcing Lean Burn on a non-lean burn engine (F22b1) using a VAFC. How I've done this:
-Vtec Engagement has been dropped down to 2250rpms
-TPS < 16% (relative) at 2200-2950rpms is adjusted to 50% fuel reduction

I also use the Torque App (for android devices) to monitor my parameters.

I did recently pick up a couple bottles of MMO and I plan to run some through it as well.



Ecky, Thanks for your post as well... quite a difference in the no-load GPH for two honda engines!

[serialk11r]

Originally Posted by Old Mechanic

I think the last car I woned that revved that high at that speed was an 82 280ZX Turbo with an automatic tranny. Needed a 5 speed badly with a 3.54 rear axle ratio and a .75 OD 5th.

regards
Mech

Sadly, Toyota was making cars that revved that high up till 2005. Celica/MR2 Spyder equipped C56 transmissions do exactly what Ecky's car is doing, and they do so with a long stroke 1ZZ-FE too (HIGH friction at high rpm, BSFC goes up dramatically after 3500). Needless to say, I am content to cruise at 55mph while everyone blasts past me. I'd guess that 2/3 minimum of the fuel is going towards spinning the engine alone, afterall I can roll around with only 22% load on the engine in 5th at 25mph, and idle is 18%.

Ecky's transmission has it good, he has an 8200rpm rev limit and he uses less than half of it at 70mph on the highway! My 6700rpm rev limit is half used up at 70mph.

[Ecky]

The old engine that was meant to go with this transmission was oversquare (81:77) but my new engine has a much longer stroke with the same bore (81:89). It's not as long as the 1ZZ-FE's but I still notice a very significant drop in gas mileage after 45mph (2500rpm).

Going from 45 (2500rpm) to 55 (3000rpm) results in a cruising gas mileage drop from 48 to 38 - that's almost a perfectly linear drop, 21% less FE at 22% higher speed. From 55 to 65mph I go from 38 to 32, which is an 18% drop at 19% higher speed. My gas mileage remains around 48 from 45mph down to about 20mph.

Swapping out my transmission for one from an Integra LS would allow me to go ~21% faster at the same RPM in 5th, or cruise at the same speed with 17.5% lower RPM. Another way of looking at it, I could do 56mph at the same RPM I run now at 45mph.

[arcosine]

Lets see, 2.2/1.9*2700/2042*65/70*(120+459/70+459)*45 mpg = 74 mpg at 70 mph

relative displacement * relative RPM * relative speed * relative intake temperature= relative * mpg = relative terminal mpg