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YOUR RESEARCHFuil comsumtion is killing me 996 Y2003
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Install engine, ran it
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We installed the engine, ran it for 1900 miles to break it in and then drove it to Rennsport Reunion at Laguna Seca last September.
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It's been a few months since this discussion on oxygen sensors, so I'm curious how many people replaced their sensors and what the results were
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Suggestion
Again, abrupt or large throttle openings change ignition timing and fuel mixture to favor power over efficiency.
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Suggestion
It seems that most people will change plugs and coils as a first start to MPG concerns even when no missfires are recorded...Even though plugs and coils also age as time and mileage passes,( plugs will wear and collect carbon deposits and coils will develope small cracks) but if they don't missfire they don't effect MPG...If someone were trying to be "thrifty" and were merely concerned with MPG, the money would be better spent on upstream 02 Sensors..
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Suggestion
Although I do like the idea of changing plugs coils and filters.
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Suggestion
It seems that most people will change plugs and coils as a first start to MPG concerns even when no missfires are recorded...Even though plugs and coils also age as time and mileage passes,( plugs will wear and collect carbon deposits and coils will develope small cracks) but if they don't missfire they don't effect MPG...If someone were trying to be "thrifty" and were merely concerned with MPG, the money would be better spent on upstream 02 Sensors..
Set fault.....this is measured/times every 16 periods
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Suggestion
Our 02 Sensors are the LSF Planar type that are heated and have very fast switching times....The response times from 300mv to 600mv is 60ms ...very fast ..The switching periods on a new Sensor should be every 1 second, if it gets lazy enough to slow to once every 3 seconds it will set a fault.....This is measured/times every 16 periods ...
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Rennlist: 1 discussions
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Johan, my fuel mileage was averaging 13 mpg around town and 16 mpg on highway. Did a major refresh of parts 2 years ago including fuel injectors, spark plugs, ignition coils and MAF and I am now averaging 16 around town and 19-20 on the highway. Probably can get more but i enjoy using the powerband.
I get about 17MPG combined city and highway, but if I drive only on the highway at 65, I�ll easily get 25mpg. If I drive 85-90, it drops down to 19 or 20.
Make sure your tires have the correct pressure, and coast to long distance red light stops, and you should be good.
If your car is getting 13mpg, and it�s not sprited driving, something�s wrong.
I think I averaged 7-8mpg on the track because WOT is a good way to drain your tank and having fun at the same time.
Don't know how a GT3 throttle body with an IPD competition plenum influences mpg on a M96. But the bigger throttle body probably doesn't help improve gas mileage.
I know gasoline is expensive these days but I ignore the fuel usage in both of my "toy" cars. It's smiles per mile that I keep track of...Like GC996 said the powerband is where the fun is and that comes with a cost.
What mileage are you seeing in your 996
@johan.eklund
? Do you have any modifications on your car? Gas prices are worse in Europe than we are used to in the US (I'm guessing about $7 a gallon in Sweden?).
The 996 is definitely thirstier than it seems like it should be for such a small aerodynamic lightweight car. I don't run the engine steady state under 3k RPM (I feel it's better for the engine) -- which means that I'm sometimes in 5th gear instead of 6th on the highway depending on speed. I'm sure I could get better mileage if I shifted up a gear, but I refuse lug the engine on the 996. I've never measured MPG because the 996 is for fun driving and I really don't keep track. The main downside of the not very good MPG for me is that I fill up more often than I'd like.
The EPA estimates for 2000 996 are 15 city/23 highway for a Carrera 2 and 15 / 22 for a Carrera 4. Interestingly, the EPA mileage is the same for 6-speed and Tip, but differs slightly on awd vs rwd.
https://www.fueleconomy.gov/feg/Find...15636&id=15638
I've got a 3.8L with the IPD plenum and 82mm throttle body. I just drove across the country. Typical cruising speeds between 80 and 85mph. Overall trip was 25mpg. My normal use is mixed city/hwy and I get 15-20 depending on what I'm listening to.
Johan, Something is telling the computer to add fuel. Can you get a scanner and look at the fuel trims. If you don't have any codes or CEL, maybe the O2 sensors are somehow indicating it's lean, thereby asking for more fuel. Injectors could be clogged or not spraying correctly. This will also end up as bad signals to the computer. Get some readings first. Although I do like the idea of changing plugs coils and filters. Especially if you don't know when it was done last. Good luck!!
Appreciate it Paul. Yeah, all codes are good. New everything on the car. I am just heavy footed and can't resist taking it thru its paces. Never listen to the radio, but I do enjoy the sucking sound of the intake and exhaust.
Sorry Glen. My comments were information for Johan. I pulled your quote to reference the GT3. If there's one car here that I know is running well, it's yours. I think you hold the gold standard for how these cars can last when taken care of properly.
A good friend of mine and a Rennlister here told me his 4.0 FSI got 34 MPG on a cross country trip recently...That's pretty impressive...
I have specialized in engine management even before fuel injection and emission controls were mainstream, and I can tell you that with modern cars 95% of the time when fuel mileage is a real concern ( and no fault codes) the 02 Sensors are responsible for the wasted fuel...Their main job is to monitor and help control fuel mixtures. They used to be mandated to last 80k miles, with the reduction of ZDDP they were hoping for 120K miles , but they often get lazy way before this...
Owned mine for 17 months and have really only used it for very high revving canyon drives once a week or every two weeks. About 80 miles round trip. I dare say I've never calculated the MPG. And probably shouldn't
But I do have to get gas pretty much before each drive up
I don't know what specific mpg numbers OP is getting, but when it's approaching single digits there's clearly an issue going on with the car. This shouldn't be ignored.
Good thread to read on the topic of which Skip explains the what and how's of oxy sensors. Good read.
https://rennlist.com/forums/996-foru...s-mileage.html
Might be worth it for the OP (and others with poor mileage) to try Redline SI-1 Fuel System cleaner -- the references to it in the DI40 thread makes it sound like it walks on water and is better than Techron and others (based upon what's it contains). The posts discussing it start here (
https://rennlist.com/forums/996-foru...l#post19181932
) -- there are only a few posts on the fuel cleaner, since it's an oil thread), but it sounds quite good. I've used Techron and Sea Foam in the past, but am going to give Redline SI-1 a try based upon the comments.
My guy that cleans fuel injectors (hurst injector service) swears by the SL-1 cleaner, says none of the others are worth anything.
I doubt the injector cleaner will help, it's much more likely to be a MAF or an O2 sensor problem.
thanks Glenn, I can't add any more to the subject than I did in that thread, unfortuantly many will read it and not believe it, or it will go over their head. I'll just recap by saying that the 02 Sensors are the judge/jury/and executioner of fuel mixtures when at "closed loop cruising" for MPG...
It seems that most people will change plugs and coils as a first start to MPG concerns even when no missfires are recorded...Even though plugs and coils also age as time and mileage passes,( plugs will wear and collect carbon deposits and coils will develope small cracks) but if they don't missfire they don't effect MPG...If someone were trying to be "thrifty" and were merely concerned with MPG, the money would be better spent on upstream 02 Sensors..
Thanks for the info. It looks like there are a total of four O2 sensors -- pre-cat and post-cat on each side. Do all four need to be replaced, and is OEM better than the Bosch equivalent?
I am the Renn lister with he 996.2 that Skip referred to in post 12. My car has a 4.0 FSI Stage II+ engine. It is the m9Experience engine that I worked with Jake Raby to build. My wife and I actually went to Jake�s Skunkworks facility last July and assembled the engine with Jake coaching us. We installed the engine, ran it for 1900 miles to break it in and then drove it to Rennsport Reunion at Laguna Seca last September. After Rennsport, we drove up the coast to Seattle and then back across the northern US. We drove approx 9200 miles total and averaged 30 mpg for the trip. We drove. 400 mile + stretch across Wyoming and South Dakota at 85 mph and got 34 mpg. Photo of trip computer attached. It is a very nice engine!
Mark
This. I've used this product numerous times and not only did it help produce some very low fuel contamination numbers in my UOA but also cleaned out a lot of the carbon build up from the tops of the pistons. Nothing else produced the same results. I've posted photos from a borescope in one of the threads. I accredit it to helping me find some piston damage that led to an engine rebuild. With a piston coated in black carbon I wouldn't have found it.
@wyovino
Yes, here some info Porsche Technical Class P21 / Advanced Engine Management ...
Our 02 Sensors are the LSF Planar type that are heated and have very fast switching times....The response times from 300mv to 600mv is 60ms ...very fast ..The switching periods on a new Sensor should be every 1 second, if it gets lazy enough to slow to once every 3 seconds it will set a fault.....This is measured/times every 16 periods ...
Havent replaced mine yet which are about 7 years old. AF ratio readings were good this spring, but i have to pull out the durametric this fall and see what it reads. MaF, coils and spark plugs were just done 2 years ago. But I still have to do the Blow By test just for the heck of it. Doubt I have any problems after running 12 qts of oil on the track with a deep sump and UAOS T. Didn't experience any hiccups.
Discovered 2 large vacuum leaks which I have since repaired, but this did not affect my fuel economy or engine performance, surprisingly. I just swapped out both upstream oxygen sensors as well as the MAF a few days ago. I'll follow up on the results once I put a few more miles on it.
I have owned over a dozen 996s of all types/years. The cars seem happy to get 30mpg and above on the highway and not drop below ~17mpg in city with smoother throttle inputs. Assuming no misfire or other relevant trouble codes -I've never owned an auto but I'd go north of 26mpg easily even in modified turbos on the highway. The .2 Carrera and the GT3 are capable of 34+mpg, even above 75mph.
Again, abrupt or large throttle openings change ignition timing and fuel mixture to favor power over efficiency. Look ahead and coast earlier instead of braking, get on throttle earlier and with less wide angles when traffic starts to move etc. and you will see a pretty big improvement. An attentive driver can easily get better gas mileage than even cruise control. Some people make lots of throttle adjustments, if you minimize this, you will see a difference. This concept applies to practically all electronic ignition/fuel controlled fuel injected control system engines. I personally have not seen a fuel mileage increase from O2 sensors unless one was faulty.
So, what you are telling me is, if I drive on flat roads, avoid accelerations, and drive with the AC off, I can get better fuel economy?
I, for one, am shocked. But I will give it a try the next time I am out in my Prius.
In the mean time, I plan to keep the loud button all the way down in my 996.
To be clear, I am talking about adjusting throttle input between (arbitrarily picking some numbers) 20-25% during cruise instead of 0-45%. This is not referring to how to drive the car in a fun way. I tend to have fun on approach to and leaving the apex to be fun, and will be "sporty" with the controls for those parts. But not for adjustments I might make between 70 and 85mph. Of course, drive in a way that makes you happy. I do tons of track events and endurance races and (fuel stop/pit strategy notwithstanding) efficiency is not of concern there. Anyway, I'm just rambling now so I shall stop!
The way I read
@Marv
's comment is that I've got to get a GT3 if I want to save money on gas
. At least that's what I'm going to tell my wife. We'll see how it goes -- wish me luck.
While that is some impressive fuel mileage, I am wondering if you took the time to manually figure it out (gallons at fill up vs miles traveled, blah, blah, blah). Would be interested in the difference between what the pen and paper says vs what your dash says. Again, 34 mpg in a 911 is quite impressive, but virtually unheard of. I sometimes drive like a little old lady, trying to hyper mile my car, and can't seem to get over 23/24 mpg.
Not quite pen to paper but I used to calculate at every fill up. Leftover habit from putting larger injectors when turbocharging a car (usually some BMW) and not being able to trust the "range" displayed on the trip computer. There was even a way to massage the values the on board computer saw to it would then display accurate range #s.
The “buy a GT3 for the fuel savings” discussion with my wife didn’t go all that well, if I’m honest. Women are so fickle!
That said, after MUCH discussion, she’s “all in” for me picking up a new set of GT3 brake ducts
.
The lesson here, gentlemen, is always, always, always negotiate.
#LivinLarge / #LivinMyBestLife
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