MAF Mod

[Red_Chili]

I have so many things that could pay for themselves, I should be living on the residuals and put the difference in my IRA...

I do know that keeping my throttle at 1/8, coasting wherever possible, and keeping my speed down has certainly paid for itself. Helped with that accepting, inner peace thing too.

 

[Hants]

I have so many things that could pay for themselves, I should be living on the residuals and put the difference in my IRA...

I do know that keeping my throttle at 1/8, coasting wherever possible, and keeping my speed down has certainly paid for itself. Helped with that accepting, inner peace thing too.

Keeping an 80 at 1/8 throttle would just burn gas -- you'd be going basically nowhere!

 

[Red_Chili]

The joys of 3.4 litres and 5.29s on 35s... towing, now that requires a bit more throttle.

 

[corsair23]

Jeff, I still have your Scan Gauge II. I'll bring it to the RS meeting next week, unless you want it earlier.

I'll probably swing by and grab it and the net one night this week. I'm going through SG withdrawls . Plus, we are heading to Grand Lake Saturday morning so it would be nice to have it for the trip and get Hants his data

 

[Nay]

Well, I just spent a few days in Keystone with a side trip to Vail, what a great difference up towards Eisenhower, I was often passing instead of puttering in the right hand lane, was always able to easily cruise at the speed limit. Coming up west Vail Pass is still slow, and west to Eisenhower is still slow, but much better.

Fuel economy? Well, I averaged it out over 2 tanks and got 14 mpg on 1/3 city 2/3 highway. This with family of six onboard with gear. 5.29's and 35" Intercos.

I don't think my fuel economy is much improved since I've been getting these results with 5.29's anyway, but no question how much better it is breathing on the high passes. My wife even noticed as a passenger.

I'd say for the high passes that the MAF mod has done as much as the 5.29's, or perhaps best to say they complement each other very well.

It doesn't need to pay for itself. I'll spring

 

[Hants]

Based on my recent testing, you'll probably see a boost in MPG by keeping the RPM below 3550 on the passes.

 

[Nay]

Based on my recent testing, you'll probably see a boost in MPG by keeping the RPM below 3550 on the passes.

Yep, it's feeling pretty ideal for what this rig is. I don't hit those kind of RPM's up the passes because my gearing in 3rd is lower and in 2nd is quite a bit higher, but I'm easily in stock range for fuel economy on a hardly stock rig. No way I'm touching 17 mpg, but 15 highway when I keep it at 65-68 mpg is right on.

Problem is all this good stuff keeps tempting me to go 37's

 

[corsair23]

I'd be curious to know the following:

1. Set your SG to monitor LOD, RPM, OPEN/CLOSED, TPS
2. Monitor OPEN/CLOSED LOOP as you're driving
3. At what RPM/LOAD/TPS combinations does it switch to OPEN loop?
4. When do you hit those combinations?

I used to hit Open Loop merging onto the freeway and going up even moderate grades. Now, I only hit Open Loop going up steep grades at high altitude (and then, only when I force 2nd and keep the RPM too high).

Hants, I have some data for you

I set my Scangauge II up as requested above and noted the following during a recent trip to Grand Lake (up and back and then up and back again )

Some baseline numbers first:

Idle at a stop light, AC off: LOD = 19 to 21 | TPS = 8 | RPM 610 to 625
Idle at a stop light, AC on: LOD = 25 | TPS = 8 | RPM 700ish
Off throttle (coasting) to a stoplight, AC off: LOD drops to 10 then gradually climbs back up to ~20 when stopped.

Now, here are some readings when my rig went into OPEN loop:

LOD - RPM - TPS
58 - 2500 - 38
61 - 4300 - 66
63 - 3400 - 58
60 - 4200 - 60

Some general observations on when the rig would go into OPEN loop:

• Anytime you lift off the throttle and coast
• Pretty much anytime RPMs > 3750 (maybe even a little lower)
• Pretty much anytime the TPS > 60

Obviously when TPS > 60 and RPMs > 3750 the LX would most certainly be in OPEN loop. It appears max TPS (for me at least) is 75 based on testing which would be WOT. So at 60 TPS that is 80% WOT.

As for when the above scenarios fit. The first one (58/2500/38) was pulling away from a stop light in town, going up a slight hill, before the trips. The other occurrences were all while going up Berthoud pass mainly although anytime I hit TPS > 60 and/or RPMs > 3750 the LX would be in OPEN loop which was pretty much anytime I was trying to climb a hill

It will be interesting to try this test again after I install the MAF housing and new MAF and see what changes.

 

[nakman]

I realize now that I'll probably never see the big benefit to this mod. I never exceed 4000 rpm's, and rarely go above 3500, would only do that going up I-70 towards the tunnel or something. So I probably never get into open loop?

I've always had this theory that the my big ol' 1FZ-Fe will last longer if I didn't push it so hard, and 5 minutes more drive time is nothing plus I'll use less gas and oil.. but maybe I'm just a pansy.

 

[Hants]

Great data, Jeff!

My Idle load is 13-15 (from memory). The lowest I've seen is 3, when coasting down a steep hill.

The OPEN on no throttle is related to the fuel cutoff. Mine isn't 100% consistent (most times goes to OPEN when I let off the throttle at highway speeds, but not always, sometimes goes to OPEN when I let off the throttle in the city).

My mas TPS is 76, IIRC. There's a separate switch for WOT. On my rig, it triggers just before I hit the floor.

I think there's a correlation between LOD and RPM to go into OPEN loop. On mine, if load is >60 (maybe a bit more), I go into OPEN as soon as my RPM goes over 3550. If load is <60, I have been able to get as high as 3900 RPM in CLOSED loop (maybe even higher -- I haven't really pressed this limit).

The only time I see OPEN loop these days is going over passes. And that's controllable by shifting into 2nd and driving at 50MPH (instead of the 60 to 65 I used to push). On my rig, 50 is right at 3500 RPM. This sometimes means running 1/2 throttle in 2nd (not enough power to hold 3rd).

We just returned from a trip to Breckenridge. We normally travel the back roads (Hoosier pass down to the 24 to Colorado Springs. In this case we took a "slight" detour to Crested Butte over Cottonwood pass. Drove from Breck down to Buena Vista, across Cottonwood Pass, over county roads (mostly unpaved) to just South of Crested Butte, then into Crested Butte and drove around some neighborhoods up by the lifts, then retraced our route across Cottonwood pass, and back home. Had a large pod (hangs off the back, and covers most of the sunroof, width is just narrower than the rails) on the roof, and a full load. I got 15 MPG on the whole trip. I'm amazed at the MPG I get now that I'm more careful with the throttle.

I'm surprised by that first OPEN transition on yours. I haven't seen anything like that since I've been monitoring.

I suspect that you'll see lower LOD values across the board once you install the MAF. I don't recall if the SG actually reads the MAF on our rigs. I have a different ODBII reader that does. The max MAF I could get stock was just under 17 lbs/min of air. With the new MAF goes over 19.

I'll be curious if your LOD>60+RPM>3750==>OPEN pattern continues. I wonder why the difference?

 

[Hants]

I realize now that I'll probably never see the big benefit to this mod. I never exceed 4000 rpm's, and rarely go above 3500, would only do that going up I-70 towards the tunnel or something. So I probably never get into open loop?

We don't have a enough data on various rigs yet to really have this OPEN/CLOSED thing characterized yet. If we can get more locals to post up their info, we'll get a better idea of patterns.

I'll bet you see noticeable differences. If nothing else, the little extra oomph is a blessing.

I've only seen one post here or on MUD of NO increase in MPG, and, IIRC, that was only on one particular route.

Do you have a SG? If so, monitor when/how often you're in open loop (at a minimum), before and after the MAF.

 

[Nay]

I realize now that I'll probably never see the big benefit to this mod. I never exceed 4000 rpm's, and rarely go above 3500, would only do that going up I-70 towards the tunnel or something. So I probably never get into open loop?

I've always had this theory that the my big ol' 1FZ-Fe will last longer if I didn't push it so hard, and 5 minutes more drive time is nothing plus I'll use less gas and oil.. but maybe I'm just a pansy.

I never saw, and haven't realized, mpg as the benefit. Engine smoothness under better power delivery at higher RPM has been the clear benefit for me, and it sounds like I drive more like you do (I cruise at 65-70).

This mod may allow more driver behavior flexibility, and therefore mpg increase via throttle management, but without changing any variable but the MAF/sensor I haven't seen any increase in fuel economy. I can actually pass up high on I-70 now, where before I was always in the slow lane, and my engine isn't really loud during the process.

I think the mpg benefit is emerging in a $4/gallon world were justifying the cost to works when you can calculate a short term breakeven. I just don't think it's the MAF that's getting you there as much as it's driving style, outside of saying that more power can enable less of the skinny pedal.

Much like my 5.29's. I have picked up 1-2 mpg increase, but only if I keep speed down under 70. If I still want to drive 75, I still get 12 mpg. But I have good power delivery at 65 because I'm up in the power band with higher RPM, so if I'll cruise at 65-68 I get the better economy. Same would have been true I am sure with the stock gears, except RPM was so low it was bogging all the time at our altitude (notice the posts on MUD above improving mpg by going up to 285's at sea level).

So the big benefit on the label isn't mpg, but it may be an achievable output with a modification of driving style. You and I may have simply already had that modified driving style, so a bit mo' powa and NVH reduction are the only real benefits to this mod (I think those are bigger on a pig on 35's anyway).

 

[corsair23]

I realize now that I'll probably never see the big benefit to this mod. I never exceed 4000 rpm's, and rarely go above 3500, would only do that going up I-70 towards the tunnel or something. So I probably never get into open loop?

I've always had this theory that the my big ol' 1FZ-Fe will last longer if I didn't push it so hard, and 5 minutes more drive time is nothing plus I'll use less gas and oil.. but maybe I'm just a pansy.

Tim,

You would probably be surprised, as I was, at how often your rig goes into OPEN loop. It would have been easier to collect the data had I had a computer with software that would record the data for later analysis. As it was a challenged to try to monitor the SG for the exact moment the LX would go into OPEN loop while driving so instead I just started to watch for consistent parameters. I would say more often than not once the RPMs hit 3500 the LX would go into OPEN loop but it is hard to catch because the values change so quickly. Watching the LOD and TPS values is easier because they don't change as fast.

I'm seriously considering 4.88 gears despite only running 285s just to get the rig to run in a more efficient power band. Often just to get the LX moving on some of the switch backs on Berthoud pass after a tight 20 mph corner the tranny would shift down into first. Instant OPEN loop at that moment and the second the LX would upshift into 2nd it would start to bog down. If I could keep the speed up and the LX in the 3500 RPM range then I could generally keep her in CLOSED loop going up the hill. I wasn't trying to set any speed records, just stay close to the speed limit

Now that I have some baseline data for my rig I should be able to see what, if any, changes the MAF mod will have on my rig. I'm holding off until I get the tune up done so as to not have any of those effects blurring the advantages (if any) of the MAF mod.

 

[Hants]

Now that I have some baseline data for my rig I should be able to see what, if any, changes the MAF mod will have on my rig. I'm holding off until I get the tune up done so as to not have any of those effects blurring the advantages (if any) of the MAF mod.

Speaking of tune-ups: If your O2 sensors are > 100K, you should consider refreshing them along with your normal tune-up stuff (plugs, wires, cap & rotor, air filter). And check to make sure your exhaust isn't too crunched (particularly where it goes under the frame rail, and at the end after the resonator).

 

[corsair23]

Speaking of tune-ups: If your O2 sensors are > 100K, you should consider refreshing them along with your normal tune-up stuff (plugs, wires, cap & rotor, air filter). And check to make sure your exhaust isn't too crunched (particularly where it goes under the frame rail, and at the end after the resonator).

Hmmm...The LX has ~108K miles on it and I'm sure the O2 sensors are the originals. I considered replacing them but the comments I had read were to leave them be until they start throwing a code . Maybe I should consider going ahead and doing them anyway?

As for my exhaust...It is fine except the end which is squished, yet again, due to CM . But, I seem to be getting slightly better gas mileage since CM08 so I was thinking the extra exhaust restriction was helping

 

[Hants]

There are several threads on MUD regarding the O2 sensors and their (perported?) affect on performance. My experience with pre-hard-failure-replacement was positive (mileage up a bit, power up a bit, sleep quality much improved).

I finally gave up on my exhaust tip and took a sawzall to it.

 

[corsair23]

There are several threads on MUD regarding the O2 sensors and their (perported?) affect on performance. My experience with pre-hard-failure-replacement was positive (mileage up a bit, power up a bit, sleep quality much improved).

I finally gave up on my exhaust tip and took a sawzall to it.

Good info on the O2 sensors...I'll have to look into them then.

As for the exhaust tip...We discussed the sawzall mod after CM07 but I still have not done it - the squished tip is like a badge of honor for me

 

[Hulk]

Sawed my exhaust tip off after Henley goaded me into it. My MPG subsequently increased by 0.00185%.

 

[treerootCO]

I put my new MAF sensor in last weekend and didn't notice the rough idle that some have reported. The engine was cold but I had the ECU unplugged for a few hours so that may have helped. It made me feel good that a mod was bringing my '95 up to date with a newer technology and that alone was worth it to me. Unlike the snake oil remedies for better economy and performance, this was an actual update. First impression is that the engine appears to be smoother at higher RPMs. The usual tune up items like plugs, wires, etc. are all original to the truck and have been under the bonnet for 178,000 miles. Those will be next...