10 mpg 3.2 - can’t find where the fuel is going

[Discseven]

Originally Posted by REVerend

Have you tried pushing the car with your hand while it’s on a flat surface? It’s pretty easy and you would notice resistance. I push my car around a bit just maneuvering it in the garage and a single click of the emergency brake will make it noticeably difficult to push, though the engine would easily overcome if you tried to drive it like that. A simple push test would tell you if there was some gross friction going on.

REV... that was done at the very beginning of this journey. I know the typical resistance having pushed the car many times (on flat and other surfaces) since owning it from '92. Have also had other 911s to push. I did not discover the binding e-brake early on doing this but that was eventually discovered and both sides were rebuilt some time ago.

Originally Posted by scarceller

Calculating city MPG is not that easy, driving habits, length of trips and stop and go frequency is different for every driver. But even 12MPG is not so good.

Highway driving is far more predictable to compare, typically the 3.2 can see 24-28MPG depending on how well it's running.

Has anyone else ever tracked city MPG? I'm just curious.

But the OP is stating that prior to rebuild he got far better MPG in the city, as I recall around 16MPG but after rebuild it's currently at 12MPG.

Sal... prior rebuild city mpg was 18. Last city test stands at 11.55.

Originally Posted by 917_Langheck

Lots of WAGs being floated here, but most have already been addressed or are not relevant - octane doesn't affect mileage to the degree believed, but added undisclosed percentages of ethanol does.

Someone please send Discseven a known good, working DME to swap with his existing so the ECU/fuel driver circuit can be ruled out as a cause of the unusually large disparity between city and highway mileage.

917... Thank you for this suggestion.

ECU now installed is NOT the one that was in the car when it was getting 18 city mpg. The one now installed is from a dubious resource. I'll not name who as it is not proven that the ECU is at fault. How and why the dubious ECU is in the car is too complex a story to get into. The installed unit has been tested by ProGrama and "no faults" were found. I spoke with Specialized ECU repair yesterday questioning if, when they test ECUs, do they test the fuel maps for corruption (accuracy) or not. They do not. This leaves the ECU in question assuming Programa also does not test fuel maps. A call is due them with the same questions. I suspect it being to time intensive were these testing places to check fuel maps.

I'd be eternally in gratitude to the one who lends me a known working ECU. I'll pay shipping both ways. Soon as it's received, will fill tank and drive the city till there's half a tank. Difference, if it is my ECU, should be apparent. Will send your ECU back immediately and of course treat it with great care.

Originally Posted by mysocal911

Yes, I agree, but most have ignored/discounted it. New power typically requires additional energy input with tradeoffs, e.g. the low-end vs high-end.

Dave... good point on the trade off re what Julian stated. I continue to wonder about the changes (mods) made being the cause. But some don't support this being the cause---mods = 964 cams timed to 1.45, SSIs, Dansk muffler. Before the rebuild, I checked PPF commentary on these parts being used and found no one stating their city and/or highway mpg taking a nose dive after installation. Perhaps I didn't find any such mention and others have found the same as is being attended here. I would think, if anyone experienced the same as is going on here, someone would have found the thread and said so by now.

Julian's proposal about there being "no missing fuel to find" makes sense provided the parts installed have drastically increased the exhaust's freeflow. But can we accept the exhaust flow---on the low end---having nearly doubled? "Nearly doubled" is based on the fuel use being nearly twice what it used to be. Here's a normally aspirated 3.2 engine theoretically processing almost the same amount of air-fuel as a 930 3.3.




Blackstone sample kit just arrived. Checking the oil for the "missing" 10 gallons of fuel per tank full is not the purpose. Am doing this to see if anything is revealed about the engine's status relative to the city mpg via the oil. Am sending crank and fresh oil. We'll have a baseline to refer to when looking at the crank oil's profile.



Blackstone sends plastic jugs. The little info they want with the oil can be completed in a form online then printed to return with the oil to be tested. They include a postage paid USPS envelope. Testing = $40 cost per sample. Getting oil out to them today.
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[Discseven]

Frictional hunt at each corner

Was done according to the checklist below. Process revealed 1 item at the front corners. Nothing in the rear. Front: there’s contact between the a-arm and shield that protects the rotor. Is the same on both sides of the car. It’s chafing. There’s no evidence of contact between the shields and rotors. Absent drag, this is something to attend but not a piece that fits the mpg puzzle.



Left front corner with this corner of the car in the air. (There's no load on this corner's suspension.) Chaf wraps around the radius of a-arm's rounded end on the rear side---so there's contact while steerage changes direction.




Left front clearance check of shield-to-rotor with suspension now fully loaded. A-arm is resting on blocks.

Both the chafing & clearance match on both sides of the car. Exactly what’s out of place here is undetermined. If there was contact with the rotors, I'd be into this immediately. As it is, I’ll be returning to this downstream to sort it out.




Above, left front (LF) checklist. Each corner was inspected with same form. Comparing brake pad and rotor dimensions reveals nothing out of order. Brake system appears well corner-balanced. Fits as there’s no pull of the car to either side under braking. Not included in the list is checking caliper piston clocking. All were checked and are in proper position. Calipers are all relatively new. About 8 years.




I did not check for corrosion on piston walls. Reason: did not want to disturb the rubber collars. Did remove the pads and pushed out the calipers by pumping the brake pedal 3 times. Before pumping, wood slats are stuck in between the rotor and pistons. Purpose: keep piston from coming too far out... and potentially hitting/damaging the rotor. Wood slats are later used to lever piston back into caliper. One caliper is done at a time. Push-out distance of pistons is checked. All pushed out to an equal distance. Wood slats do not interfer with this push-out. Given the age of these calipers, good condition of the rubber collars, equal push out of the pistons, smooth return of the pistons, nothing odd about both brake pad and rotor thickness measures… there’s no evidence of the pistons binding. Brake fluid has been changed a number of times since these calipers & rotors were installed (approx 8 years ago.)

Test that Sal suggested is to check the soft lines that serve the brakes. Premise being there could be an internal blister/blockage that allows the brakes to work but does not allow a proper retraction of the fluid and so a caliper’s pads dragging on the rotor for some period of time after the brake pedal is released. Clearly a scenario that fits city driving and not highway. Plan is to check this and put a timing light to the pulley later today.



Planning ahead... given the possibility that the “Julian-theory” is what remains standing, idea I have is to restrict the exhaust air flow… unless someone has a better approach. If the ECU is working properly, I gather it should appreciate there being less air flow and so reduce fuel flow. Wideband logs should immediately reveal what’s taking place. I suspect if the logs read rich and continue to do so, ECU is not doing what it should be doing.
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[inaminit]

Karl-I can lend you an ECU for testing. I would ship it USPS with extra insurance if you are ok with that. PM me if you want to proceed

[Showdown]

Oh god, don’t ship it usps… FedEx or ups.


Sent from my iPhone using Tapatalk

[Discseven]

Originally Posted by inaminit

Karl-I can lend you an ECU for testing. I would ship it USPS with extra insurance if you are ok with that. PM me if you want to proceed

INaminit... absolutely stellar of you! Thank you. PM sent.
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[proporsche]

Karl..why is your brake disc touching the A arm ..not normal at all in any position .Do you have bend struts? Can you look and take picture of this area ..any line there will show you it is bend....

[Discseven]

Originally Posted by proporsche

Karl..why is your brake disc touching the A arm ..not normal at all in any position .Do you have bend struts? Can you look and take picture of this area ..any line there will show you it is bend....

Ivan... is not the brake disk / rotor touching the a-arm. It's the metal protective shield that the a-arm touches. There is clearance to the disk / rotor. I checked the side of the disk / rotor that faces the shield and a-arm and there's no wear or markings on the rotors. I agree, that contact should not be. If a strut is bent, the other side is bent to the same degree as this contact is the same on both sides.

I'll take pics as you suggest.
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[Discseven]

Brake pedal release test

All corners released immediately. Given checks made to the brakes, other tests + this, am concluding the brakes at all corners work correctly.

Notes -

Done with engine at op temp, 210 on gauge and running to have booster in play. Op temp is to have rear soft brake line sections heated as they’d normally be when car is driven. One person holds brake pedal down, second person applies rotational pressure to the tested corner’s wheel, pedal person then releases brake pedal quickly signaling release to second person at wheel. Wheel person gauges whether the wheel drags in the least when brake is released or if it immediately spins freely. Purpose is to confirm or deny the soft lines allowing brake fluid to immediately retract and so the brake pads to retract away from the rotors. Should any brake drag, suggests possibility of soft hose having an internal blockage. Credit to Sal for this test.



Timing light

Engine's at op temp...



Idle




1000 rpm




2000 rpm




3000 rpm
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[Discseven]

Tie rod fault

Other day when doing the “brake release,” I happened to turn the front passenger-side wheel in & out and looked at the steering wheel… steering wheel didn’t move. This was with the passenger-side of car in the air and driver-side on the ground. Did same set up with driver’s side and there’s no play on that side. Driver's side, moment that wheel is turned in or out, steering wheel moves with it. Checked this again last night to be sure of what’s going on. Same results.





RF wheel’s in-out steering play = 3.75 mm.

Same procedure was repeated a few times. Same results. Driver’s side was checked again. No play. Installed are Turbo tie rods that went in in 2012. Car is lowered. Not sure if car’s slammed height affects tie rods. Ride is very stiff—I like it. Car parts surely suffer to some degree from this tight suspension. For non sports car passengers… always a sensory awakening.




Steering joint in smugglers. Nothing odd here as I see it. Makes sense given steering wheel turning immediately when driver’s side front tire is turned in or out. I’ve had car since ‘92. Steering rack has never been rebuilt under my ownership. Durability of old Porsche parts… impressive to say the least. I suspect that were there an issue with the rack, driver-side wheel and steering wheel would not act in unison as they do. Am not a steering parts expert so this is an assumption. Steering rack is on the rebuild list.

Toe

With settled suspension:

Front toe in = 2.58 mm
Rear toe in = 1.5mm

Use c-bar to check toe. Caliper measures distance between end of C bar to rim forward then aft. Flat & level surface is needed for accuracy. Subtract aft measure from front measure = toe. (Is a positive number provided there is toe in.)





With play, what toe does when car’s driven is questionable. I tried to set the wheel’s in & out apogees with the car on the ground. Didn’t work. Tire’s too gummy-glued to the ground to turn it in or out slightly and have it stay there. Checked toe without settling the suspension and it was of course off the chain. Settling the suspension moves the tire to its “default,” static, grounded position. If play were severe enough, surly car would wander when driven. Doesn’t. I do suspect the wheel moves to its turned out apogee when driven. During rebuild, nothing with the suspension or steering was touched. Is very likely this play existed to some degree when the car was doing 18 city mpg. So while this is clearly out of whack, I don’t see it being the cause of the mpg nosedive.

Any disagreement with this play being a worn tie rod?

Rear end notes

Bushings for the trailing arms and in the torsion bar control arms were replaced a few years prior to the rebuild. Rear shocks were replaced soon afterwards. Wheel bearings have now been checked a number of times with the same result: zero play.

What’s left…

ECU is soon to be mpg tested against the unit Dean, aka Inaminit, is kindly lending to help solve this puzzle. Thank you Dean.

Julian’s “more air = more fuel” theory gains traction. However, and once again, a 3.2 nearly reaching the city mpg of a 930? Is the exhaust now so much more free-flow than the stock config? Why is no one else with 964 cams, SSIs, Dansk muffler doing the 10-11.5 mpg dance I’m doing? —-ECU?

If Dean’s ECU proves my ECU being good, next move will be to choke the exhaust off in increments.





Never have I taken so long or done so much to solve a 911 puzzle. That’s not to brag, or, to beat myself up. Is what it is. With things having been found & fixed along the way… there’s something to be said for relentless hunting. In this hunting vein, came upon one of Greasy Fingers / Johannes' vids just now that makes this fuel journey seem quite tame—time wise—compared to his 2-year puzzle...





Bent struts?

Have not forgotten a closer look at these Ivan.
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[76FJ55]

Originally Posted by Discseven

Tie rod fault



With settled suspension:

Front toe in = 2.58 mm
Rear toe in = 1.5mm

Use c-bar to check toe. Caliper measures distance between end of C bar to rim forward then aft. Flat & level surface is needed for accuracy. Subtract front measure from aft measure = toe.

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I'll assume you are just posting absolute values in the results published for front an rear above, but just to confirm, following your description of subtracting the front measurement from the rear measurement, positive values would be toe out and negative resultants would be toe in.

[Discseven]

Originally Posted by 76FJ55

I'll assume you are just posting absolute values in the results published for front an rear above, but just to confirm, following your description of subtracting the front measurement from the rear measurement, positive values would be toe out and negative resultants would be toe in.

76... You are correct. I flipped the what-to-subtract from-what. Should be "subtract the rear rim from the front rim = toe in." That's a positive number provided there is toe in. I'll go back and correct that. Thank you.
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[Discseven]

Jwolfes 911. Front suspension looks familiar. But, his contact is against the castle nut. Mine is against the end of the a-arm. What he’s dealing with…



J considers this the result of Elephant Racing’s “raised spindle service.” Assuming that’s correct, J says ER's failing to accept responsibility. J’s thread: https://forums.pelicanparts.com/porsche-911-technical-forum/1178971-another-bad-experience-elephant-racing.html#post12481015




Visuals and spin tests on my wheels confirm they're absent of friction. Why the chafing between my a-arms and rotor shields? This is sideline stuff, not provenly related to the mpg puzzle. Am posting it as someone may know what's causing the chafing. I have yet to take a close look at the struts as Ivan suggests.
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[Discseven]

ECU Comparison test

Dean / “Inaminit” lent his ECU to work this fuel puzzle. Bold of you Dean. Thank you. “917”, thanks to you for starting this ECU thing rolling. According to Dean, his ECU is an ‘87 box that works fine with his ‘86 engine. Unit’s been checked by Ingo Schmitz who upgraded it to a 28 pin. Map may not be a match to map in my ECU. After installing his in place of mine yesterday, 114 city miles were driven between then and this morning. Miles driven are typical of what I usually drive so this is an apples-to-apples driven mpg comparison. Filled tank at Westar, same pump, same fill procedure. Odo has already proven to be on target.





17.64 city mpg.

My ECU was tested during this fuel puzzle journey a while back by ProGrama. “No faults” were found. Suspicion lingered. Thinking to have it checked again by a different place, I spoke with Specialized ECU Repair in Ft. Lauderdale. Asked them if they checked the integrity of fuel maps when they “tested” ECUs. Had they said, “Yes, we do.” ECU would have gone to them. They said “No.” Begs the question of exactly what parameters are checked when any shop “tests” an ECU. Gears are already turning to replace this f’d up ECU (that was “snuck” into my car at the end of the rebuild) with a unit that delivers typical 3.2 mpg. Had I know this ECU went into my car and more importantly, where it was from, it would never have touched my car. When a proper replacement is in hand, I'll get to where this ECU is from.


Wideband logs were run while Dean’s ECU was installed. After removing his unit and reinstalling mine, new logs were run with my ECU so all these logs are from yesterday and this morning.


Warm idle:



W/Dean's ECU.




W/Mine.

"Warm" is engine at 210 according to dash temp gauge.



City drive



W/Deans ECU.




W/Mine.

Logs are from different stretches of road.



3000 rpm held steady in 4th gear:



W/Dean's ECU.




W/Mine.
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[Mr. Merk]

Wow. A resolution at last. What a ride!

[mysocal911]

Originally Posted by Discseven

Julian... cams were not the "only thing." ECU and coil are not the same as when engine got 18 city. ECU has been tested but I remain dubious. Blaster coil I have not gotten a suitable Bosch black replacement to test that. If anyone knows if a coil would make this difference, sing out.

I'm prepared to dive back into the engine if it comes to nothing left but cams. Would like to rule everything "simple" out before doing a return trip. Imagine... replacing the cams only to find out... it's not the cams!





Merk... Yes on stock chip. I've not considered a new chip. Given the relatively decent wideband logs, do you think there is a chip config that would trim fuel while also not leaning the engine out?






917... AFM is original to engine, adjusted but put back to where it was. ECU is indeed not the same as was previously in car. Lucas injectors were in engine prior to and after rebuild. These were tested against Bosch 158 originals. Both sets were tested by Mr. Injector, Bill and passed. For comparrison, Lucas were run in one side of the engine and Bosch in the other...



There is now all Bosch injectors running.

I too wonder about the overlap + cams. As you note, the wideband would "see" excess fuel delivery but it's not there. I reiterate the wideband system being gone through systematically so the data seen must be accurate.

A note for anyone heading to mod their engine. I installed these 964 cams, SSIs, and Dansk muffler on the recommendation of a "Porsche expert." There was no comment on his part about the fuel consumption cost and no questioning on my part to him or others in that regard. Was my mistake not empirically researching what affect these adjustments would have. Lesson learned and passed on.


Webcam input

Called Webcam. Spoke with Faith. Asked her what the difference is between stock 3.2 cams and 964 40/40 gind cams. She said the 964 has 20 thousandths more lift and slightly less duration. Was as I interpret this. I added I overlapped cams 2.45 rather than 2.25... and there are SSI and Dansk 2-in-1-out muffer with these cams. Config according to her would definitely not result in 10 mpg... "It's something else." She's emailing me stock and 964 40/40 technical specs. Will be interesting to see the numbers. Post them later.
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Where's the image of the "stock chip"?

[Discseven]

Originally Posted by Mr. Merk

Wow. A resolution at last. What a ride!

Merk... Ride indeed. Still have to sort out getting a correctly functioning ECU from where this apparently dysfunctional one came from. I sense from what Dave's asking, this may be a good ECU but perhaps not suited to a 3.2.

Originally Posted by mysocal911

Where's the image of the "stock chip"?

Dave... ECU's inside images below were posted in the earlier thread...







Images are from post #46 at: https://forums.pelicanparts.com/porsche-911-technical-forum/1161024-way-turn-3-2-air-flow-disk-3.html

Does that chip ID sticker have a genuine look to it?
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[mysocal911]

Originally Posted by Discseven

Merk... Ride indeed. Still have to sort out getting a correctly functioning ECU from where this apparently dysfunctional one came from. I sense from what Dave's asking, this may be a good ECU but perhaps not suited to a 3.2.




Dave... ECU's inside images below were posted in the earlier thread...







Images are from post #46 at: https://forums.pelicanparts.com/porsche-911-technical-forum/1161024-way-turn-3-2-air-flow-disk-3.html

Does that chip ID sticker have a genuine look to it?
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It's a stock Porsche Euro chip.

[proporsche]

yup that is stock chip-short version-1984-86
Ivan

[Showdown]

Ok so that still begs the question- what was the ECU doing- changing timing and fueling that weren't appropriate to the 964 cams?

Remember there was no fuel being wasted- it was all being burned, just too much of it.

[Discseven]

Is it possible for these chips to get corrupted or are they bullet proof?