Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > Z Series > E36/7 Z3 (1996-2002)

E36/7 Z3 (1996-2002)
E36/7 Z3 Roadster, Z3 coupe, Z3 M Roadster and Z3 M Coupe talk with our gurus here.

Reply
 
Thread Tools Display Modes
  #26  
Old 07-25-2012, 10:27 PM
rwg rwg is offline
Officially Welcomed to the 'Fest
Location: Acton CA
 
Join Date: May 2002
Posts: 1,711
Mein Auto: '08 Z4
Fwiw - for engines that are designed to take advantage of higher octane, the gas mileage increase with higher octane seems to offset the price pf premium fuel. Top teir gas matters. When we had to replace a cat on our 100000 mile minivan (*sigh* to having a minivan), the first quesiton the dealer asked was what type of fuel are you using. Over time, I have seen my CPO 2008 Z4 increase from 29 mpg to 32 highway after better gas had a chance to clean things out. I have become a firm believer in using name brand gas without ethanol if possible to improve the life of the engine and exhaust systems. It may or may not cost a few more dollars per tank. It will avoid an early $800 - $1200 cat repair bill.
Reply With Quote
  #27  
Old 07-25-2012, 10:51 PM
rwg rwg is offline
Officially Welcomed to the 'Fest
Location: Acton CA
 
Join Date: May 2002
Posts: 1,711
Mein Auto: '08 Z4
Fwiw - for engines that are designed to take advantage of higher octane, the gas mileage increase with higher octane seems to offset the price pf premium fuel. Top teir gas matters. When we had to replace a cat on our 100000 mile minivan (*sigh* to having a minivan), the first quesiton the dealer asked was what type of fuel are you using. Over time, I have seen my CPO 2008 Z4 increase from 29 mpg to 32 highway after better gas had a chance to clean things out. I have become a firm believer in using name brand gas without ethanol if possible to improve the life of the engine and exhaust systems. It may or may not cost a few more dollars per tank. It will avoid an early $800 - $1200 cat repair bill.
Reply With Quote
  #28  
Old 04-30-2013, 09:08 AM
AB1945 AB1945 is offline
Officially Welcomed to the 'Fest
Location: The Villages FL
 
Join Date: Aug 2012
Posts: 104
Mein Auto: '01 Z3 & '02 325i Wagon
I have a 2001 Z3 2.5 automatic which I bought a couple of months ago. I was driving easy and the computer was showing an average of 16 mpg. I checked the actual mileage against the fuel I was putting in the tank and found I was getting about 20 around town and 26 on the highway. So I recalibrated the fuel computer to the real world. Another thing I have checked is the speedometer - it is about 6% fast - does this mean the odometer is also showing 6% more miles? Is there a way to calibrate the speedometer I wonder. To calibrate your fuel consumption check this thread: http://www.bimmerfest.com/forums/sho...+fuel+computer
Reply With Quote
  #29  
Old 04-30-2013, 11:02 AM
Blacklane Blacklane is offline
Officially Welcomed to the 'Fest
Location: Springfield, Ohio, USA
 
Join Date: Jun 2011
Posts: 1,061
Mein Auto: 1998 Z3 Roadster
You can correct your speedometer with one of these:
http://www.bimmerfest.com/forums/sho...d.php?t=551995
But that has no effect on the odometer. That reading comes from the on-board computer. My experience is that the odometer is accurate to within about one percent, and it's a little low, probably due to tire wear. You can easily check it with a GPS unit.
Reply With Quote
  #30  
Old 05-01-2013, 06:57 AM
gmushial gmushial is offline
Registered User
Location: Redding, Calif
 
Join Date: Jun 2011
Posts: 97
Mein Auto: 1999 Z3 2.5L
AB1945 - we have a '99 2.5, but 5sp - before the vanos rebuild was getting 25-26 on the highway; after doing the rebuild, have had a couple three tanks that were just over 30 (30.1, 30.2 type numbers) - though 28-ish is more normal. [all mileages are computed from miles on odometer and gallons on pump, not OBC.] W/re speedo: yes, 6-7% optimistic is what we're seeing - which is "ok" now that we understand such.

Last edited by gmushial; 05-02-2013 at 03:50 PM.
Reply With Quote
  #31  
Old 05-02-2013, 02:58 PM
diva_3181377 diva_3181377 is offline
Registered User
Location: Dallas
 
Join Date: Apr 2013
Posts: 34
Mein Auto: 2000 Z3 2.5L Auto
Hi Greg..how much you are getting on the city? I am getting about 20-21 (Auto). Never tried on 100% highway. VANOS was rebuild few months back (Besian systems). To be honest, found no difference in MPG or pickup. Also changed the DISA valve which was dead and it made some difference.
Reply With Quote
  #32  
Old 05-02-2013, 03:50 PM
gmushial gmushial is offline
Registered User
Location: Redding, Calif
 
Join Date: Jun 2011
Posts: 97
Mein Auto: 1999 Z3 2.5L
Quote:
Originally Posted by diva_3181377 View Post
Hi Greg..how much you are getting on the city? I am getting about 20-21 (Auto). Never tried on 100% highway. VANOS was rebuild few months back (Besian systems). To be honest, found no difference in MPG or pickup. Also changed the DISA valve which was dead and it made some difference.
A city mileage number is hard to quote in that it depends so much on the nature of the driving... I was speaking at a conference in SF last August [what was Mark Twain's quote: the coldest winter I've ever spent was a summer in SF?.. so true - that fog will freeze you to death ;-( ]... and I only managed under 100 miles back and forth from the hotel to the conference center and out to dinner and back etc... and that was a whole tank of gas, ie, something like 10mpg. Around Redding I may manage 200ish miles on a tank. But my real test pieces are like driving down to LA (season tickets to LA Phil), or to a customer site in Phoenix - then the results are pretty stable: on E0 89 gas - just at 30mpg; on E10 I lose almost 2mpg; on E15 2+, almost 3 mpg. W/re the VANOS rebuild - it was worth 30, 30+ miles per tank. Out on the road doing the miles: I look for gas around 280 miles, start getting nervous past 290, 295 miles (that's with E0 gas). California gas I start looking around 260, 270.

W/re not seeing an improvement with the VANOS rebuild: for ours it was significant - got the bottom end torque back, and a solid 3+ mpg. If you didn't see such, possibly your seals weren't totally toast? I know on ours, I could drop the VANOS pistons entirely through the bores and have them slam into the bottoms.. actually they rattled in the bores the seals were so far gone. But the fact the you have the Beisan seals now - in theory you'll never have to do them again :-)

-------

Just a quick follow up: it seems that the '01/'02 3.0 5sp automatic Z's get about the best mileage of any of the I-6's - with the 2.9x differential and the deep overdrive 5th, they're running down the freeway doing 500-600 rpm less than I am; and with all that bottom end torque, they don't have to get deep into the gas to move on down the road. ... I've actually been looking at/for one for the long trips... generally consider myself a manual transmission type person, but for doing the 600-900 mile days, where the only shifting is into and out of a gas station... I don't think I'd be offended... also might help keep some of the miles off the "hellrot II toy".

Last edited by gmushial; 05-02-2013 at 04:30 PM.
Reply With Quote
  #33  
Old 05-03-2013, 07:26 AM
diva_3181377 diva_3181377 is offline
Registered User
Location: Dallas
 
Join Date: Apr 2013
Posts: 34
Mein Auto: 2000 Z3 2.5L Auto
When i changed the VANOS seals, it was not rattling, also it was not like i can drop it. It was tight and newer one's made it little bit more tight. Checked the cam positions with INPA and seems no delay in reaching the new position with rpm changes now. I should had tried it before changing the seals. Also the CPS sensor looks good and no issues.

Most of the time, my driving is from home to work. ~15 miles on 35-45 mph zones with lights at almost every mile. It never went down 20 mpg (tried premium and regular gas). Premium gives more power, but mpg remains same. Here all gas stations have 10% ethanol.

One more good thing to learn. If i have to replace the differential, get a 2.9x one. Better mpg on highway
Reply With Quote
  #34  
Old 05-03-2013, 01:37 PM
gmushial gmushial is offline
Registered User
Location: Redding, Calif
 
Join Date: Jun 2011
Posts: 97
Mein Auto: 1999 Z3 2.5L
Quote:
Originally Posted by diva_3181377 View Post
When i changed the VANOS seals, it was not rattling, also it was not like i can drop it. It was tight and newer one's made it little bit more tight. Checked the cam positions with INPA and seems no delay in reaching the new position with rpm changes now. I should had tried it before changing the seals. Also the CPS sensor looks good and no issues.

Most of the time, my driving is from home to work. ~15 miles on 35-45 mph zones with lights at almost every mile. It never went down 20 mpg (tried premium and regular gas). Premium gives more power, but mpg remains same. Here all gas stations have 10% ethanol.

One more good thing to learn. If i have to replace the differential, get a 2.9x one. Better mpg on highway
It sounds like then that your rebuilding of the VANOS was not to the necessary stage, but was appropriate, in that you'll now never suffer the gutless bottom end and the cold idle stumbles. It's a given that one will have to rebuild the VANOS on all the M52 and M54 motors (bad seals by spec by bimmer engineers), it's just a question of how long one has to put up with a un-bimmer feeling motor - for me it was starting to feel more like a Yugo and a Z, and that's painful and sad.

W/re mileage w/re premium gas: I suspect if you were to drive it at the same performance level as using regular gas, in fact you would see a couple miles per gallon improvement... just a) it's hard not to make use of the extra performance, and b) as creature of habit it's hard to change the automatic driving responses one has learned over the years. I know on some of the other cars here, ones with OBC/mileage readings, I can make a 20% difference easily by changing how far I get into the gas pedal... just hard to drive "gently."

The question of the 2.9x differential is a little more complex. Basically I suspect the cost of swapping diffs would result in a many year payback period. The calculus of fuel mileage isn't entirely straightforward. ... An engine is at it's maximum volumetric efficiency at max torque - for the 2.5 and 3.0, 3500rpm. Anywhere on either side of that it is less efficient (volumentrically), but not necessarily fuel mileage-wise. At lower revs per mile, there is less energy dissipated as friction/heat. So, if an engine can produce enough torque - that which really moves a car down the road - at a lower rpm, but not too far below max torque, then it'll get better fuel mileage. An important question has do with how much torque the engine will produce at the required rpm, at partial throttle is an important factor. The 3.0 is a long stroke torquer. BMW didn't build it to be a top end motor like the S52 or S54, it was built as a highway cruiser, and given the cam profile and the aggressive VANOS programming: it can produce all the torque one needs to roll on down the freeway at a very partial throttle setting. The 2.5 is not that motor. It is more of a mid-range to top-end engine (not nearly like the S54); but it is not the 3.0 freeway torquer. So... if you just swap the diff, you may or may not, get better mileage (*). If the goal is to maximize the mileage given the existing configuration: I'd make sure the tires are on the hard side - that'll cut down on the rolling resistance; I would make sure the air cleaner is fresh, or even maybe find a lower restriction cleaner (possibly at the expense of engine wear); and I would possibly go to a freer flowing exhaust. The next step beyond those would be to buy a reprogrammed ECU chip - most people when the do that are looking or more power and topend; but one can equally buy new chips which are more stingy on fuel, possibly at the expense of power. ... or, one can just not worry about it, and worry about the smiles-per-gallon number and not the miles per gallon ;-) ... The CD for the car with the top up is something like .42, but with the top down is .34(??), ie, if one wants to save on fuel, one should never have the top down... but the, why own a convertible??

climbing down off his soapbox ;-) ;-(
greg

(*) a classic example of this is: a lot of the go-fast types over on bf.com have swapped out their 3.15 or 3.23 diffs, for 3.73's - which buys them an extra 20% torque at the wheels. And again, since it is torque that moves the car (basically to overcome rolling resistance and aero drag) - at a fixed velocity, a fixed amount of torques is required... so, even though their engines are now running 20% faster, and producing more friction losses, the fact that they are less deep into the gas pedal to produce the less torque required from the engine, some are saying they see zero change in fuel mileage, some maybe 1 mpg - so, this is a case of higher speed on the engine, moving away from max torque on the engine, yet not seeing a fuel mileage decrease, a la using less gas pedal.
Reply With Quote
  #35  
Old 05-03-2013, 02:11 PM
diva_3181377 diva_3181377 is offline
Registered User
Location: Dallas
 
Join Date: Apr 2013
Posts: 34
Mein Auto: 2000 Z3 2.5L Auto
VANOS rebuild was the one of the initial things i did to the car (since i got it). Saw about that in almost all the forums and with the help of my friend, did it (also the VCG, Spark plugs).

Most of my driving, even reaching t 3K is rare. It will be less than 2K most of the time. Even my wife laughs at my driving .You are right, what ever habit we learned from years of driving, cant change it easily.

Understood. No advantage for the 2.9x differential with the 2.5L engine.

About MPG, i just want to make sure that nothing is broken inside and because of that i am loosing any power / mpg. Also the O2 sensors are new. MAF sensor seems working fine with INPA. CTS and AIT sensor also shows proper values (except the DIS and INPA shows -48 for one coolant sensor on radiator outlet which seems not in this car). Other than vacuum leak checking, did all the work. All fluids are new, belts are new. I guess the 10% ethanol is taking 2mpg (just like your car).
Reply With Quote
  #36  
Old 05-03-2013, 02:16 PM
gmushial gmushial is offline
Registered User
Location: Redding, Calif
 
Join Date: Jun 2011
Posts: 97
Mein Auto: 1999 Z3 2.5L
Quote:
Originally Posted by diva_3181377 View Post
VANOS rebuild was the one of the initial things i did to the car (since i got it). Saw about that in almost all the forums and with the help of my friend, did it (also the VCG, Spark plugs).

Most of my driving, even reaching t 3K is rare. It will be less than 2K most of the time. Even my wife laughs at my driving .You are right, what ever habit we learned from years of driving, cant change it easily.

Understood. No advantage for the 2.9x differential with the 2.5L engine.

About MPG, i just want to make sure that nothing is broken inside and because of that i am loosing any power / mpg. Also the O2 sensors are new. MAF sensor seems working fine with INPA. CTS and AIT sensor also shows proper values (except the DIS and INPA shows -48 for one coolant sensor on radiator outlet which seems not in this car). Other than vacuum leak checking, did all the work. All fluids are new, belts are new. I guess the 10% ethanol is taking 2mpg (just like your car).
Ethanol is neither the friend of gas-mileage, nor the environment... but BigAg loves it :-(... it sounds like you've done about all that can be done under the hood... I run the tires at 36psi (to get even wear) - you might look there for some mileage; and if you want, maybe a freer-flowing exhaust.
Reply With Quote
  #37  
Old 05-03-2013, 03:21 PM
gmushial gmushial is offline
Registered User
Location: Redding, Calif
 
Join Date: Jun 2011
Posts: 97
Mein Auto: 1999 Z3 2.5L
Just a follow up thought: one can drive an engine too slowly and actually do it more harm than good. At low rpms one is in danger of "lugging" the engine - which is rough on the bearings (*). The other point being carbon buildup. I don't know how many miles you've put on the engine while you've owned it, but occasionally an engine needs to be run up to/toward redline to keep the valve seats clean. Though there is a danger there, ie, over time the cylinder walls form what's called a ridge - which is that area just above where the top ring rides/reaches. This location is further up the wall if the engine is routinely used at higher rpms. The danger is: if one has been running the engine at low rpms for a long time (20, 30k miles), ie, the ridge has formed down low, and then when one blasts to redline: the top compression ring plows into the ridge which it normally doesn't reach, and crack. Basically engines wear to represent their usage pattern... so, even though buying a go fast car from an old lady that has never pushed it, seems like a good idea - there is a very real danger that the first time one runs it up to redline that one will destroy the top rings on all the cylinders :-( x1000 ... my suggestion, again assuming you haven't put too many miles on yours at low rpms, is to occasionally run it up in revs. My impression is that our 2.5's are happiest in the 2500-4000 rpm range, with occasional runs to 6k to clean it up (and rejuvenate the spirit).

(*) at low rpms, the bearings "see" each individual cylinder firing, as a hammer blow - at higher rpms, the secession of ignitions gets smoothed out... also, there is higher oil pressure above 3000, and it is the oil that keeps the bearings from colliding metal on metal (read: $'s).
Reply With Quote
Reply

Bookmarks


Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > Z Series > E36/7 Z3 (1996-2002)
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



Forum Jump


All times are GMT -7. The time now is 09:13 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms