Falling out of lean burn on 94 VX

[OG VX]

Hey, made this video today for the question posed in this thread. Hope it helps!

https://www.youtube.com/watch?v=6_OJ...ature=youtu.be

[pgfpro]

OG VX Very well done!!!

[jeffcat]

Originally Posted by firehawk618

It's physically impossible for your RPM to MPH correlation to have changed without any modifications *transmission* or clutch slipping *which would not be a consistent 100rpm difference*.

I would place the blame on either the speedometer or tachometer being inaccurate.

Considering the weather you describe and a massive amount of idle time 35Mpg seems pretty good to be honest.

I believe these guys who get north of 50Mpg in their VX or HX are very careful drivers.

I thought maybe it could do with the drag or something as I went out today and it was back at 2100rpm at 65mph, so I'm not quite sure what to make of that.

I'm aiming for 70+mpg highway on this vehicle, which doesn't seem too far fetched based on what I've seen from others. I was at getting 52mpg in lean burn 4/5th of the way between 65-75mph. Even being in lean burn the whole way would put me at around 60mpg(previous owner supposedly hit 62mpg once) or even a little over which I've heard of others hitting before. I'm "satisfied" with 52mpg considering all I've done so far is change the fluids, but I need to clean up the rest of the engine a bit.

It's kind of a pain to get an "accurate" mpg value without data acquisition, because it gets such good fuel economy you need to drive it forever to get an accurate sample size in gallons, and with the highway MPG rating, that's a hell of ways. I could drive across the entire state of Ohio right now and only use 4.5 gallons of gas doing it. I'm actually slightly undereporting right now too I believe since my tires are slightly larger than stock. I'll have to get some data acquisition and take it out for a few rides and see how it does. I have to go Cincy and and Mid Ohio quite a few times this year, so it will get some trips on it to have as more accurate long data points.

[jeffcat]

Originally Posted by OG VX

Hey, made this video today for the question posed in this thread. Hope it helps!

Thanks for the vid. It helps with the visualization. I hear what you mean by there being multiple stages as there are times where it's hard to tell if I am or am not in lean burn probably because I'm in an "in between" stage. I can kind of tell when it's in lean burn, but it's easier to tell when I'm cruising, it falls out with the definitive pick up in power, then for a split second, I let off the gas, then get back into it to unload the engine a bit and then it feels like I need twice the throttle input to keep it at speed since it's in full lean burn and can't maintain the speed it was going with that power.

I'll have to look up how to set up the vac guage and and MPGuino. I know I want to set them up sometime, so I'll have to get on that task sometime in the future after I get a few things sorted. Where did you get that particular vac guage at?

[jeffcat]

While attempting to change out the fuel filter(still leaking) today on the VX and putting in the "proper" 4 heat range rating NGK plugs in today, I put in a new air filter and I got to thinking a bit.

Lastly, is the MAP even serviceable as in cleaning? I know it has a diaphram that goes to a digital input, but I didn't know if you could clean it up with something like MAF sensor cleaner or not.

[firehawk618]

Originally Posted by jeffcat

While attempting to change out the fuel filter(still leaking) today on the VX and putting in the "proper" 4 heat range rating NGK plugs in today, I put in a new air filter and I got to thinking a bit.

The MAP sensor is 1 of 4 I believe factors that are put into the lean burn equation for the VX. I know everybody is running warm air intakes and and so forth, but would a high flow, closer to the throttle body conventional "cold air intake" actually improve fuel economy? The reason I ask is because you if you are running a dirty stock air filter, this would inherently increase manifold pressure since the suction effect is decreased by the dirty filter. Likewise, a high flow "cold air intake" would decrease the pressure in the manifold over the stock setup simply because the suction of the cylinder would have less resistance to overcome wouldn't it? I could be all wrong about that, but I just found that to be somewhat interesting.

Lastly, is the MAP even serviceable as in cleaning? I know it has a diaphram that goes to a digital input, but I didn't know if you could clean it up with something like MAF sensor cleaner or not.

Map sensors are not serviceable.

A side note: On my HX tonight I discovered that obsessively trying to stay in LB *definitely LB* on the HX was actually using more fuel vs just shifting to the highest gear I could. I verified this via MPGuino and several trips up and down the same highway.

[user removed]

Originally Posted by OG VX

Hey, made this video today for the question posed in this thread. Hope it helps!

This post is one of the most significant I have read on this forum in a long time, especially since I am an advocate of highest gear when ever possible.

I do know the VX trannies 3rd gear is good for close to 120 mph at redline.

Please don't take this wrong, doesn't the vertical location of your guino on the windshield pillar interfere with your vision, especially in such acritical area as where a head on swerving into your lane would be "recognition delayed" by the guino location.

Personally, I would move it higher or lower, outside of the sight line to oncoming traffic on 2 lane roads. It might be considered nit picking but that exact area of visibility has saved me from a few catastrophic head on collisions, giving me time to swerve to the right to avoid the impact, which could have killed me.

I highly admire your work in it's quality and execution and this post could be interpreted as "picky-petty", which is not it's intent.

regards
mech

[user removed]

I forgot to respond on your vacuum gauge analysis which is perfect. The 110 mile column of air, entering the intake manifold is relentless in it's insistance on entering the engine.

I generally rest my accelerator foot on the tranny tunnel on the right side of the foot, to minimize even the minuscule variations in throttle position, since using a vacuum gauge.

Preheating the intake air on the Sentra has created some interesting effects as temps here rise. Throttle response in top gear has dropped noticeably and it wants to downshift
(automatic trans) more readily. Based on your posts I think I'l lleave the WAI connected, since the only way I could accomplish anything similar to a "lean burn" benefit is by the reduction is effective atmospheric density due to the WAI.

regards
mech