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

[proporsche]

karl....since those things arm and a leg to get ..how about if i lend you mine mechanical adjustable .You are crafty dude you could probably duplicate it.i had it on my 911 back in 1996 when i got it.Took it off about year later.....i use it as a tool now --but very very seldom;-)

[Flat Six]

Originally Posted by 76FJ55

Not specifically between banks. the intent of the damper is to damp the pulses in the fuel rails. with a batch fire system all the injectors open simultaneously, and the fuel flow from the pump can't change volume fast enough to eliminate the dip in fuel pressure. the spring loaded diaphragm of both the fuel pressure regulator and fuel pressure dampers are riven forward towards the rail and displace the stored volume of fuel to help feed the system during injector open time. then when the injectors close the regulator had closed due to the drop in rail pressure and the pump feed will repressurize the damper and regulator to build the stored fuel back up until the defined pressure is reached an then the regulator will again begin to bleed excess pressure back to the tank.

Correct; meant rails, said banks. My bad.

[scarceller]

The driver's side is the Fuel Pressure Regulator, is this what has fuel coming out of the vacuum port? If so it MUST be replaced.

Then you mention the damper on the passenger side, is it also leaking from the nipple?

Trying to understand what nipple has the leaking fuel?

Neither of those devices should ever have fuel coming out of the vacuum port, if they do it means the device must be replaced.

Never use an after market regulator! Only a Bosch unit should be purchased.

[Fab64]

Ok, I hope this isn't a stupid question, but if the 964 cams are the reason for the poor mileage, why wouldn't an actual 964 have just as poor fuel mileage? Flame away - LOL!

[Showdown]

Engines are designed as a complete package: all the components spec’d to work together. When mixing and matching parts you can get strange results.


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[scarceller]

The 964 cam if dialed in and timed to spec will have peak/max intake valve lift at exactly 111 deg ATDC. Checking lift at TDC is a waste of time, according to the cam spec the intake is set at 111 LCA that means peak lift should occur at 111ATDC. If you want to know if the cam was correctly timed using TDC lift please do secondary check to see if peak lift occurs at 111 deg.

Many pro engine builders time cams using LCA peak lift method because using this method is spot on and does not care what the valve lash is set at, peak lift always occurs at same spot regardless of lash. Timing cams at TDC is very problematic for 2 reasons. One it depends on having lash correctly set and two, at TDC you are still in the cams opening ramp area.

I'm not sure what's causing your MPG issue but it's likely not the cam. I have plenty of customers with 964 cams with no MPG issues. I suspect something else is wrong. Possibly faulty injectors that are over fueling or not shutting off at low pulse rates?

I believe you have a WBO2 gauge installed? If so have you attempted a cyl balance test at idle? Also have those injectors been sent out to have flow and spray patterns checked?

Also test Fuel Pressure, at idle 30-32PSI with vacuum connected. 36-38PSI with vacuum line removed.

Then be sure you do not have a brake dragging, after a city drive take temp readings on all 4 rotors.

[Discseven]

Originally Posted by GH85Carrera

Karl, my cams are 100% stock 964 Cams. No regrind at all.

Thanks Glen. I thought when getting the 964 cams I have that there were only one kind of 964 cams. Have since learned there are different 964 cams based on their "grind." In my case I have 40i, 40e grind. "i" for intake and "e" for exhaust. What those numbers mean I do not know.

Originally Posted by proporsche

karl....since those things arm and a leg to get ..how about if i lend you mine mechanical adjustable .You are crafty dude you could probably duplicate it.i had it on my 911 back in 1996 when i got it.Took it off about year later.....i use it as a tool now --but very very seldom;-)

Ivan... Those parts are indeed absurdly priced. Idea of making it is appealing. I assume that if adjustable, you are referring to the pressure reg. Would take your kind offer on however, with my pressure reg and dampener hoses testing bone dry, the read on those parts is they're good. Am getting on with the hunt. In any case, thanks for the offer Ivan! You are inventive.

Originally Posted by Fab64

Ok, I hope this isn't a stupid question, but if the 964 cams are the reason for the poor mileage, why wouldn't an actual 964 have just as poor fuel mileage? Flame away - LOL!

Originally Posted by Showdown

Engines are designed as a complete package: all the components spec’d to work together. When mixing and matching parts you can get strange results.

Julian... Yeah, deviating from stock is a risky play ground. I know this and went there anyway. Answer to this is out there... waiting.

Originally Posted by scarceller

The 964 cam if dialed in and timed to spec will have peak/max intake valve lift at exactly 111 deg ATDC. Checking lift at TDC is a waste of time, according to the cam spec the intake is set at 111 LCA that means peak lift should occur at 111ATDC. If you want to know if the cam was correctly timed using TDC lift please do secondary check to see if peak lift occurs at 111 deg.

Many pro engine builders time cams using LCA peak lift method because using this method is spot on and does not care what the valve lash is set at, peak lift always occurs at same spot regardless of lash. Timing cams at TDC is very problematic for 2 reasons. One it depends on having lash correctly set and two, at TDC you are still in the cams opening ramp area.

I'm not sure what's causing your MPG issue but it's likely not the cam. I have plenty of customers with 964 cams with no MPG issues. I suspect something else is wrong. Possibly faulty injectors that are over fueling or not shutting off at low pulse rates?

I believe you have a WBO2 gauge installed? If so have you attempted a cyl balance test at idle? Also have those injectors been sent out to have flow and spray patterns checked?

Also test Fuel Pressure, at idle 30-32PSI with vacuum connected. 36-38PSI with vacuum line removed.

Then be sure you do not have a brake dragging, after a city drive take temp readings on all 4 rotors.

Sal... Timing was done to Webcam's procedure. They use some starting lift value that is supposed to be standard in the industry. I followed that to a T. Made good sense at the time but forgot the details of it. If I mentioned TDC, I'll correct that. Has been a year or more since that was all done so my recall is challenged. Here's Webcam's timing card for the 964 40/40 cam installed.



Fuel injectors have been tested by Bill in Idaho. You were parcel to the Lucas and Bosch wideband injector comparisons. Injectors now installed are all Bosch 158.

All the tests you suggested (in the past) were done but for the coil. I bought a used black Bosch off eBay and it was no good. Was not inclined to buy another. So Blaster remains installed. Should you insist a coil could result in 10 city, 27 highway, I'll continue down this coil path. I have the specs on the Blaster coil if you'd like to see them. I did compare the Blaster to the original Bosch specs and everything was a match as I saw it.

Cylinder balance (disconnecting one injector at a time and watching wideband for reaction) was done. Fuel pressures and flow have been tested. List of tests done is lengthy. My first post offers a menu of what's been checked. I have to add the "cylinder balance" to that menu.

With more energy/force/fuel being "efficiently" (according to O2 readings) expended to move the same vehicle, this points to an increased load of significance... but ONLY where city driving is concerned. Yet, nothing has been added to the car's weight. And my driving style has not changed.

If there is an increased load on the engine---city only being an oddity and surely a clue...

Engine/crank turns over easily and smoothly by hand so think engine friction can be ruled out. You may recall heads were restored by Xtreme. Were it engine friction, I think highway mpg would be in the gutter too. It's not. Car tracks straight with no hands on the steering wheel. So one corner drag-friction is ruled out. This suggests it having to be a symmetrical friction if friction is indeed causing increased load. Clearly whatever the cause, it is connected to getting the car moving, and not keeping it moving.

Can an AFM air intake temp sensor failure be a culprit?
.

[rokemester]

Hey Karl I’m following this thread with great interest even though I’m understanding about 20% of what you guys are talking about! I used 964 cams when I had a top end done on my 87 Targa. I’m going to have a closer look at my fuel consumption. I noticed you have a “custom fuel feed with spin on filter” listed in your 85 3.2 911 profile. What is that?

[Discseven]

Hit list brought forward with updates...

Hit list:

• DONE - Vacuum line connected to pressure regulator & dampener - check for fuel in line. Both lines dry.
• DONE - Learn Motronic in order to intelligently adjust AFM - book ordered. Received & read. No added intel regarding 10 city/27 highway mpg.
• Culpable = ECU - although tested and "no faults" found, this unit was not installed when engine was delivering 18 city. May send to different place to retest.
• Coil - Blaster is installed. Although specs as promoted match original Bosch coil specs, Blaster was not with engine when it did 18 city. Did get black Bosch original off eBay but was no good. Whether incorrect or bad coil can result in 10 city / 27 highway mpg is unknown. Still looking for good, original black Bosch coil.
• IN PROGRESS - Adjust AFM wheel position/tension and log wideband results for each move. This is "research." Not doing this thinking it is answer to 10 mpg.
• DONE - AFM - Email Bavarian Restoration for AFM resto - email sent. 5.9.25 response = $365 return shipped domestic. 45 day turnaround ("lead time"). Greg is founder/owner. No retail shop. He does this part time at home.
• DONE - AFM - Email FIC - 5.15 response. $275 + shipping for rebuild. 1 week turnaround. 18 month warranty. Exactly what warranty is needs to be looked into. Robert is President. Asked if he replaced sweep circuit board or just adjusted arm position. He did not answer these points of interest.
• Jack up rear end and put car on stands so both wheels in air. Check rear hubs in neutral and in gear for rotation & rock. Looking for "frictional load" and/or bad bearings. Listen for CV crunching.
• Check gearbox oil for any oddity.

Regarding ignition coils...



Above is a snip from: https://www.porschechantilly.com/blogs/3738/8-signs-of-a-faulty-ignition-coil/

There are other symptoms listed. None of them exist in my case. Begs the question if most if not all the symptoms need to be present or just one or a few can exist?
.

[917_Langheck]

It may be time to put this car on a real gas analyzer test bed, not just a wideband AFR.

There is a throttle position:rpm:load relationship that isn't captured by the wideband between the two run conditions. Somewhere along the line fuel is escaping, so let's see how the HCs COs, and O2s track. Test the difference between variable throttle positions ("city driving") vs steady state (“highway") at various rpm ranges. Something has got to show up to point to where the fuel is going.

[scarceller]

I still recommend getting a stock coil installed but I doubt it's the coil.
Have you tested temps at the rotors? I suggest you do.

Also during city driving I assume you see decent AFR numbers in the 14s? That's a key indicator that you are not running rich.

The 40i/40e cam is almost the same spec as a 964 factory cam. The 40i/40e is slightly less aggressive. I doubt it's a cam issue.

Something else is going on here but I'm not sure what?

[Discseven]

Originally Posted by 917_Langheck

It may be time to put this car on a real gas analyzer test bed, not just a wideband AFR.

There is a throttle position:rpm:load relationship that isn't captured by the wideband between the two run conditions. Somewhere along the line fuel is escaping, so let's see how the HCs COs, and O2s track. Test the difference between variable throttle positions ("city driving") vs steady state (“highway") at various rpm ranges. Something has got to show up to point to where the fuel is going.

917... Am looking into getting an analyzer for a day next week.

Originally Posted by scarceller

I still recommend getting a stock coil installed but I doubt it's the coil.
Have you tested temps at the rotors? I suggest you do.

Also during city driving I assume you see decent AFR numbers in the 14s? That's a key indicator that you are not running rich.

The 40i/40e cam is almost the same spec as a 964 factory cam. The 40i/40e is slightly less aggressive. I doubt it's a cam issue.

Something else is going on here but I'm not sure what?

Sal... Coil is on my hunt menu. Would like to stay off eBay as the first one I got was a waste of money.

City wideband trace lines are, for the most part, above 1.0 lambda.

Shooting rotor temps today.
.

[PeteKz]

I've been watching this thread, but since I focus on CIS these days, I haven't commented much on Motronic stuff, although I have owned a few Motronic cars too. Your reports are puzzling.

If you are really getting only 10MPG in normal driving, you should be puffing dark smoke out the exhaust, fouling plugs, soot in the exhaust pipe, and running poorly. So let me ask the simple question. Are you sure you are only getting 10MPG? Have you tried to do a steady state mileage run on the highway for, say, 100 miles, to see if your highway mileage is similarly bad?

Langheck recommended putting the car on an exhaust gas analyzer, but if your lambda is in the range of 1.0, as the dyno graphs indicate, you should be burning pretty clean anyway, and no soot in the exhaust pipe correlates to that. It might be worth trying an exhaust gas analyzer to see if that corresponds to your AFR.

TLDR--Do you still have the cat installed?

[proporsche]

Originally Posted by PeteKz

I've been watching this thread, but since I focus on CIS these days, I haven't commented much on Motronic stuff, although I have owned a few Motronic cars too. Your reports are puzzling.

If you are really getting only 10MPG in normal driving, you should be puffing dark smoke out the exhaust, fouling plugs, soot in the exhaust pipe, and running poorly. So let me ask the simple question. Are you sure you are only getting 10MPG? Have you tried to do a steady state mileage run on the highway for, say, 100 miles, to see if your highway mileage is similarly bad?

Langheck recommended putting the car on an exhaust gas analyzer, but if your lambda is in the range of 1.0, as the dyno graphs indicate, you should be burning pretty clean anyway, and no soot in the exhaust pipe correlates to that. It might be worth trying an exhaust gas analyzer to see if that corresponds to your AFR.

TLDR--Do you still have the cat installed?

I have asked Karl in another treads exactly that--check the CO mix with gas analyzer...
I have a feeling his problem is some kind of an easy fix

Ivan

[Discseven]

Originally Posted by PeteKz

I've been watching this thread, but since I focus on CIS these days, I haven't commented much on Motronic stuff, although I have owned a few Motronic cars too. Your reports are puzzling.

If you are really getting only 10MPG in normal driving, you should be puffing dark smoke out the exhaust, fouling plugs, soot in the exhaust pipe, and running poorly. So let me ask the simple question. Are you sure you are only getting 10MPG? Have you tried to do a steady state mileage run on the highway for, say, 100 miles, to see if your highway mileage is similarly bad?

Langheck recommended putting the car on an exhaust gas analyzer, but if your lambda is in the range of 1.0, as the dyno graphs indicate, you should be burning pretty clean anyway, and no soot in the exhaust pipe correlates to that. It might be worth trying an exhaust gas analyzer to see if that corresponds to your AFR.

TLDR--Do you still have the cat installed?

Pete... Incorrect mpg calculation is among the first things questioned. City runs have been done repeatedly. The math is too simple to f up repeatedly. 10 is accurate. After the parking brake rebuild, city mpg went to 12 mpg. 180 city miles used 14.9 gallons so there appears what drag was there was corrected by the rebuild. Are they still dragging? I checked and there's no binding. Am not now saying "12" as it may confuse the matter. 10 or 12 mpg is the same out of whack fuel consumption.

You can be certain I've wanted my math, gas pump, or odo to be wrong. To that end, I've been over and over the city mpg. Have been filling at the same station, same pump, same nozzle position when loading the gas, and allowing the pump to cut off each time. Changed stations to test the gas. No mpg change. Odo matches state mile markers and looking at fuel gauge, it supports the math. Tank city-run to half level and odo is around 100 miles. Should be near 180 for my city driving. Run nearly empty and odo's just above 200 miles. Should be near 400.

Highway milage is 27. Have tested this a number of times too. Bad city and good highway milage...?

No cat. Have SSI heat exchangers installed. SSI hot air ducts are open at both ends---I never use heat in Miami. Have been thinking about cutting the exchangers off but with other things to do, that's on back burner.

Given wideband O2 logs not showing the engine running rich, had to question whether wideband system is accurate. Bosch sensors have been swapped side-to-side. Tests rerun. Controllers swapped side-to-side. Tests rerun. Bosch sensors replaced with new, then calibrated again to Innovate's procedure. Tests rerun. LogWorks reloaded. Rerun. No matter what's been done, readings remain consistent. Am forced to believe wideband is accurate.

No soot in the exhaust now. Was at the very beginning after the rebuild. No smoke ever. Engine runs well and pulls hard through all rpm to redline. Last spark plug visual check and they looked reasonable. Checks done to date are listed in fist post.

Am looking into borrowing a gas analyzer next week.

Ivan thinks there's an easy fix hiding here somewhere. Simple would be nice to run into.
.

[Discseven]

[Showdown]

How does the advance/timing on the stock chip compare with the suggested advance/timing for the 964 cams?


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[rwest]

Following the mystery and just throwing out things that pop into my head that could be an issue: Today’s thought/guess/musing, could you have a slipping clutch?

You would be using the clutch a lot in city driving, but hardly at all once you got going on the highway.

[proporsche]

i would test the consumption without filling the the whole tank-and go from there.
I suppose there no problem with your smelling, you would smell fuel right?
The reason i am asking is from my experience.Once i drove from south France to Bohemia --cc1300 km one way..So filled my tank in Saint Tropez where i lived close-by..
After filling the tank i took off and in couple of seconds i smelled fuel..it was from left side of the front fender.Where i prior remove the fuel tank breather canister-mistake.I drove gently for the rest of the trip ..never filled to the top again.
So do you have the canister there or not?In city taking off and braking the fuel moves in the tank much more then driving smoothly on the highway..
just an idea

Ivan

[Discseven]

Originally Posted by rwest

Following the mystery and just throwing out things that pop into my head that could be an issue: Today’s thought/guess/musing, could you have a slipping clutch?

You would be using the clutch a lot in city driving, but hardly at all once you got going on the highway.

Rutager... appreciate the pop-into-head-thinking. Clutch and pressure plate are new with rebuild. Doesn't mean they're good. Just adding that as detail. More to the point, pull when releasing clutch is instant and distinct. I know the sound created by a slipping clutch. It's not here. Will add this point to first-post list.

Originally Posted by proporsche

i would test the consumption without filling the the whole tank-and go from there. I suppose there no problem with your smelling, you would smell fuel right? The reason i am asking is from my experience.Once i drove from south France to Bohemia --cc1300 km one way..So filled my tank in Saint Tropez where i lived close-by...

After filling the tank i took off and in couple of seconds i smelled fuel..it was from left side of the front fender.Where i prior remove the fuel tank breather canister-mistake.I drove gently for the rest of the trip ..never filled to the top again.
So do you have the canister there or not?In city taking off and braking the fuel moves in the tank much more then driving smoothly on the highway..
just an idea

Ivan

Ivan... absolutely no smell of fuel and I have checked all around for fuel leaks thinking the fuel must be getting out somewhere. Particularly given the wideband logs. Usually I run no more than half a tank in order to not carry that fluid weight. For the sake of testing mpg, I've accepted the full tank load allowing the pump to shut off the dispensing. That approach is repeating in order to have consistent starting tank reference. From the fuel gauge, I can approximate mpg. Running from a full tank to half gets roughly 100 miles. Running from half tank to empty (before reserve) gets the roughly the same. So fuel gauge is working nicely!

Canister... if this is the canister just below the fuse panel, it's still there. Again, no leaks on any of the connections.


AFM adjustment

Have turned the wheel 3 notches clockwise. Even this little adjustment to the barn door's reactive tension has changed the engine's performance. Not for the better. Attempted to do logs in my usual place today but too many cars. Runs need to be done at sunrise. Tomorrow. As it stands, I'd turn the wheel back to where it was without hesitation. Before doing so, want to see what effect that move has on O2.
.