Weird MPG Question

[Ωhm]

1 hour ago, HOrnbrod said:

 

That's a thought. Hmmmm, how can you monitor ignition advance in the cab? A knock monitor? Can the Renix REM do that on a Renix engine?

Don't know if all the available addresses are available on the REM. Even if the address for ADV Timing was, it would be difficult to read during engine transit conditions. The MIN/MAX function might help (DRB has this) but the display would just flash and blink values. Steady state values would read just fine, but not what you're looking for. A strip chart recorder would show you everything you need. Kind of like a DVOM vs a Simpson meter.

[HOrnbrod]

31 minutes ago, Ωhm said:

Don't know if all the available addresses are available on the REM. Even if the address for ADV Timing was, it would be difficult to read during engine transit conditions. The MIN/MAX function might help (DRB has this) but the display would just flash and blink values. Steady state values would read just fine, but not what you're looking for. A strip chart recorder would show you everything you need. Kind of like a DVOM vs a Simpson meter.

 

I had a piggyback Unichip hardwired in on the stroker for about five years after the install and one of the things it could do was timing control: " Unichip can vary the amount of timing for every rpm, say 3 degrees more from 1500-3500 rpm, 2 degrees from 3700-5500rpm, and 1.5 degree from 5600 up to redline". You could also vary signals from the IAT, CPS, MAP, and TPS. But the programming was proprietary, Hesco did the tuning. Once they got it right it was great. It quit working about six years later and I pulled it out and never replaced it. That or something similar is always an option, but I doubt it'll ever happen again.

[Eagle]

5 hours ago, HOrnbrod said:

Very true Dirty. But a ~10 MPG difference? My other Jeeps are about maybe a 4-5 MPH difference. But they don't have AW4's either. Guess I'll just live with it then. Was hoping someone might have a silver bullet solution.

 

Add a toggle switch to manually control torque converter lock.

[Eagle]

3 hours ago, HOrnbrod said:

 

With the 31s the 4.10 ratios are very close to an MJ with stock size tires and 3.55 gears.

 

Only "sort of " close. 31x10.50-15s through 3.73 gears are almost exactly equal to 225/75-15s through 3.55 gears.

[HOrnbrod]

12 minutes ago, Eagle said:

Add a toggle switch to manually control torque converter lock.

 

Been thinking about wiring in a manual shifter for around town like the below on the console.

 

19 minutes ago, Eagle said:

 

Only "sort of " close. 31x10.50-15s through 3.73 gears are almost exactly equal to 225/75-15s through 3.55 gears.

 

Picky-picky. Close enough. 

[DirtyComanche]

35 minutes ago, Eagle said:

 

Add a toggle switch to manually control torque converter lock.

 

Yes.

 

5 minutes ago, HOrnbrod said:

 

Been thinking about wiring in a manual shifter for around town like the below on the console.

 

Might be able to come up with something nicer between RADesigns or modding up one of the available aftermarket shifters...  Or even using a GC shifter that has the manual up/down buttons on it?

[HOrnbrod]

^^  That is a RADesigns shifter and yes, it is ugly. Been looking for something I can build into my console that won't look like a wart. I still have my column shifter and there's plenty of room in the console to build it in. Maybe a simple rotary switch or something. 

[Eagle]

58 minutes ago, HOrnbrod said:

^^  That is a RADesigns shifter and yes, it is ugly. Been looking for something I can build into my console that won't look like a wart. I still have my column shifter and there's plenty of room in the console to build it in. Maybe a simple rotary switch or something. 

 

Back in pre-NAXJA days, on the old XJ forum, Frank Swigert posted details of how he wired an AW4 with a rotary switch in an AMC Hornet. Someone on the strokers forum may know how to contact Frank -- I believe he's still around.

[Eagle]

I have a question that I've often wondered about, but never pursued since I mostly drive standard transmissions: Exactly how does an automatic tranny shift? If you add a toggle switch to control torque converter lockup on the AW4, can the tranny shift from fourth to third or second with the converter locked (as long as you're moving at an appropriate speed)?

[Tex06]

I have a question that I've often wondered about, but never pursued since I mostly drive standard transmissions: Exactly how does an automatic tranny shift? If you add a toggle switch to control torque converter lockup on the AW4, can the tranny shift from fourth to third or second with the converter locked (as long as you're moving at an appropriate speed)?

Yeah, it can but you can't stop or you'll stall the engine.

Sent from my SM-G930T using Tapatalk

[HOrnbrod]

10 minutes ago, Eagle said:

I have a question that I've often wondered about, but never pursued since I mostly drive standard transmissions: Exactly how does an automatic tranny shift? If you add a toggle switch to control torque converter lockup on the AW4, can the tranny shift from fourth to third or second with the converter locked (as long as you're moving at an appropriate speed)?

 

Electrically by the ON/OFF position combinations of the three AW4 internal solenoids from signals generated by the TCU. You can shift manually through the gears with the shift selector except for O/D. You can wire in a simple manual shifter using four toggle switches, plenty of wiring diagrams on the interweb.

[HOrnbrod]

36 minutes ago, Eagle said:

 

Back in pre-NAXJA days, on the old XJ forum, Frank Swigert posted details of how he wired an AW4 with a rotary switch in an AMC Hornet. Someone on the strokers forum may know how to contact Frank -- I believe he's still around.

 

Frank Swygert. Haven't seen anything from him lately.

[Eagle]

1 hour ago, HOrnbrod said:

 

 You can wire in a simple manual shifter using four toggle switches, plenty of wiring diagrams on the interweb.

 

When you shift manually, you lose first gear. Frank did it with a rotary switch. That made it progressive --  just move one position for each gear you want. I believe he said he used a six position switch. The way I think that would play out would be:

 

1. First
2. Second
3. Third
4. Third - locked
5. Fourth
6. Fourth - locked

[HOrnbrod]

26 minutes ago, Eagle said:

When you shift manually, you lose first gear. Frank did it with a rotary switch. That made it progressive --  just move one position for each gear you want. I believe he said he used a six position switch. The way I think that would play out would be:

 

1. First
2. Second
3. Third
4. Third - locked
5. Fourth
6. Fourth - locked

 

" When you shift manually, you lose first gear." True. You can't just wire in a progressive stepping rotary switch w/o protect diodes with our TCUs. With toggles it's no problem since they are iso. I'll be looking at it tomorrow..

[Eagle]

9 hours ago, HOrnbrod said:

 

" When you shift manually, you lose first gear." True. You can't just wire in a progressive stepping rotary switch w/o protect diodes with our TCUs. With toggles it's no problem since they are iso. I'll be looking at it tomorrow..

 

I don't know how Frank did it, but he did it. It was his daily driver, I believe. And I'm quite certain he was using a rotary switch. I remember because at the time I thought it was a terrific solution. Since I'm not an electrical engineer, don't know protected diodes from unprotected (first time I ever heard of protected diodes), and don't know what "iso" is, I'm afraid I can't offer anything useful other than the concept (which isn't mine).

[omega_rugal]

"stop and go" is where gasoline goes down the drain, kicks the ECU out of closed loop in order to give you a quick start, even if it switches back as soon as you release the pedal, and with a stroker and bigger inyectors is to be expected...

[omega_rugal]

14 hours ago, Tex06 said:

Yeah, it can but you can't stop or you'll stall the engine.

Sent from my SM-G930T using Tapatalk
 

 

and if you have bad luck, @#$% up the lock-up clutch, is small and it was designed to work only at highway speeds where engine torque is minimal, it can`t withstand the engine`s full torque

 

 

14 hours ago, Eagle said:

I have a question that I've often wondered about, but never pursued since I mostly drive standard transmissions

 

you are kidding right?

 

15 hours ago, Eagle said:

Exactly how does an automatic tranny shift?

 

the TCU senses how fast the output shaft turns and uses 2 solenoids to route hydraulic pressure inside the transmission to apply or release clutches and band that control the gear reduction, see? very simple!

 

15 hours ago, Eagle said:

If you add a toggle switch to control torque converter lockup on the AW4, can the tranny shift from fourth to third or second with the converter locked (as long as you're moving at an appropriate speed)? 

 

of course you can but you must flipp it at the very right speed or else the transmission will hicup (like when you suddenly let go off the clutch after shifting a manual) ... keep doing it and you`ll eventally kill the clutches and the tranny itself...

[Eagle]

30 minutes ago, omega_rugal said:

 

and if you have bad luck, @#$% up the lock-up clutch, is small and it was designed to work only at highway speeds where engine torque is minimal, it can`t withstand the engine`s full torque

 

Highway cruise is 2000 to 2500 RPM, which is right on the torque peak. And in 4th gear, there's less mechanical advantage so the torque converter has to work harder than in lower gears, especially if towing

 

you are kidding right?

 

Why would I be kidding? You don't have manual transmissions in Mexico? They still have a lot of them in Chile.

 

the TCU senses how fast the output shaft turns and uses 2 solenoids to route hydraulic pressure inside the transmission to apply or release clutches and band that control the gear reduction, see? very simple!

 

No, I don't see. Not only that, I don't really care. The point is that the solenoids can be controlled by external switching if you want to control when the transmission shifts.

 

of course you can but you must flipp it at the very right speed or else the transmission will hicup (like when you suddenly let go off the clutch after shifting a manual) ... keep doing it and you`ll eventally kill the clutches and the tranny itself...

 

That makes no sense whatsoever. The transmission shifts at a wide range of speeds, depending on how much load is on it and how hard you're accelerating.

 

[omega_rugal]

1 hour ago, Eagle said:

Highway cruise is 2000 to 2500 RPM, which is right on the torque peak. And in 4th gear, there's less mechanical advantage so the torque converter has to work harder than in lower gears, especially if towing

 

at cruise, you move at a steady speed, the engine delivers almost full torque WITH VERY LITTLE RESISTENCE,

 

lock the converter while standing still and with high revs and watch it it gooooo!

 

1 hour ago, Eagle said:

That makes no sense whatsoever. The transmission shifts at a wide range of speeds, depending on how much load is on it and how hard you're accelerating.

 

a properly working TCU will never apply the lock up unless the right conditions are met, you said doing it manually...

[Eagle]

15 minutes ago, omega_rugal said:

a properly working TCU will never apply the lock up unless the right conditions are met, you said doing it manually...

 

Using the rotary switch takes care of that. It only locks it in third or fourth, and the shift from third up goes to UNLOCKED fourth. Then it's another switch position to lock it in fourth.

[johnj92131]

Don,

Something is wrong around town. My 91 with auto gets about 15 mpg under round town confitions.  Maybe 14+. Certainly not 10 or 11.  Gas leak?

[HOrnbrod]

Naw - it averages 12-13 around town. But that sucks. No leaks - wish it were that easy.

[gogmorgo]

I think I usually got 14-15mpg around the city too. Although my "city" driving usually meant hitting the 90km/h ring road as often as possible. That said I never got near 23mpg on the highway. I'm pretty sure I've only averaged 20 a couple times, and that was almost always following the Trans Canada from Alberta to 'Toba, which is a steady but very slight downhill with nothing to slow down for, and generally comes with a tailwind.

 

The ZJ on the other hand, 4.0/ax15/3.55's, if the gauge is to be taken as accurate and linear (doubtful) currently seems to be averaging about 21mpg around town... It's been 280 miles so far and the gauge just dropped below half. It's pretty nice to have a 23 gallon tank in my daily again. I mean the $100 fills hurt but there's always gas in it. Seemed like every time I turned around the Saint needed gas into its 16 gallon. The Lada's 11-gallon tank was worse. I'm almost tempted to go fill the ZJ just to confirm that mileage. 

 

I'm sorta curious what rpm you're turning on the highway, @HOrnbrod, also what you're shifting at. I've been trying to keep the ZJ between 1500 and 2000 rpm around town. Shift light comes on around 1800 rpm but then I shift and I'm doing 1200 or less and I'm not convinced that's the best idea. IIRC the MJ shifted around 2500 or so on power. The first little while I was using comfort (and possibly then getting better mpg) but then I got used to power and thought comfort shifted kinda weird. Not sure how much difference it would make though. 

I remember a friend of mine telling me how he used to do 70km/h on his late-night through the city commute (in 50 zones; 45/30 mph) cause that's when he noticed his torque converter locking up, and he kept doing it because he also started noticing better mpg. I wouldn't necessarily condone that, but it is a thing. As far as how the computer controls the lockup? It really doesn't take much throttle at all and it unlocks. It didn't take much of a hill on cruise control at 60mph to unlock it. Older torque converters aren't hugely efficient either, and probably the vanes will erode somewhat with use, further reducing efficiency. Modern torque converters on the other hand keep surprising me with how readily they jump forward when you take you're foot off the brake at idle. I imagine that plays a bit of a role in the better mpg newer vehicles are getting.

 

Sorry for the long winded and rambling response. It's a bit of a hypothetical question so that's a theoretical answer. 

[HOrnbrod]

On the highway I keep it right around 70 MPH, which averages 2300-2400 RPM. I have been close to 24 MPG quite a few times on a fill-up while just droning along w/o interruptions. I think the 99+ intake and 62mm throttle body combination is better suited for cruising economy than stop-and go. Unfortunately at least 95% on my driving is around town. Although I'm pleased with the good highway mileage, I'd be more pleased if the MPG delta between city and highway driving were closer. Maybe I'll slap on a stock throttle body that necks down to 56mm and try that. I can also play around with the fuel pressure settings since I have an adjustable regulator and an A/F meter. Ideally I'd like to bring up the in-town MPG w/o affecting the highway MPG. I think I'll start by lowering the fuel pressure a few psi and monitor the A/F. Right now I run at 49/39 psi using the 97 injectors.

[ejndssn]

Have you looked into injectors that have a better fuel spray atomization  I was looking into 12 hole injector just to see if there was any difference in overall performance. But that will have wait since my AP stroker is still in the garage. The injectors that are currently in are from GC wasn't sure if was from the 4.7 or 5.7 none the less it woke up the stroker nicely when starting it up, as for the mpg around town 15-17 with ax15, 3.07 gears and 235/15 AT tires and on the HW it was much better low 20's . Have you consider switching to ax15 or the nv3550 just a thought