Great pics and explanations Raymond ........The photo of the Alps was bordering on art !
Thanks again for taking the time to post . Many owners do not have any opportunity to see underneath their cars , let alone in such detail .....this thread is truly educational !
D
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Better a day as a tiger than a lifetime as a sheep !
The OEM installation kit contains two wleding sleeves to connect the center and rear part of the exhaust. However, I don't like it for the following reasons.
1: The weld quality must be of the highest standard, which can only be achieved whilst both parts are off the car. 2: The surface area of the weld is not that large and must be able to withstand the mechanical tensions caused by temperature effects. 3: Disassembly or replacement of just one part requires the sleeves to be cut through.
With other words, this is one area were I compromise originality and prefer screw type clamps. These are widely available, but I'd advice against using the garden variety clamps made from mild steel that are supplied by every car-parts store. Since I have some experience with VAG products as well I know they have some high-grade steel types which perfectly fit the E28S exhaust. Take a closer look to the clamps themselves. The clamp area is much larger then the cross section of the weld with the OEM sleeves can be.
The main advantage of these clamps is that these are 'spring' types. With other words, the effective clamp area is as large as the cross section of the sleeve after the bolts have been tightened. Another advantage is that these compensate for the temperature effects in the exhaust. The welding sleeves simply cannot do that.
I'd rather have some BMW stamps on these, but as these are not available I settle for the Audi logo. These are made from a high grade metal.
The mounting bracket for the rear-muffler. If you want to fit your new exhaust straight, you better replace this bracket!
The screw-type clamps in place. As you can see these fit perfectly. Disassembly of the exhaust is so much more easier.
The rear muffler in SITU.
A picture from front to rear. The only thing that I have to do is checking the alignment of the exhaust and tightening all the bolts and nuts.
Now, who has a pair of new 45mm tips (OEM off course) ?
As sai, I only had to tighten all the nuts and bolts of the exhaust. First, tighten all the nuts and bolts from the center-box, including the brackets for the exhaust mounts.
After the rear-muffler has been placed and the clamp around the muffler itself has been tightened and checked, it is time for the alignment.
Even though many E28's have gone to the great car park in the skies, the more senior members will remember seeing many E12's and E28's with exhausts that were not fitted straight.
With the welding sleeves this just is plain difficult and (1) since I cannot weld nor do I want to and (2) I want to allign the exhaust properly without dicovering that the welding has not been precise enough, I altered the fitting procedure by using the screw-type clamps.
With the screw-type clamps it is possible to align the exhaust properly without worrying about all the other exhaust mounts and brackets. Simply align the exhaust pipes and tighten the four nuts from the clamps. If necessary, you can correct the height of the rear brackets of the center exhaust, but this was not necessary for #231's.
Perfect alignment. This would not be possible with the welding sleeves.
Since I fitted a new AFM I had to check and correct emmisions settings. Since I do not have such an analyzer I had this done by a friendly mechanic in my presence. The test required a warming-up which i combined with testing all the drivetrain work.
drivetrain
With the new hardy disk and center-mount the drivetrain is vibration free. I didn't test her that hard as I only went to 110km/h, but that is more then sufficient. The only vibrations that are left are minor and tyre related (2002 vintage Michelin PS1's). Conclusion: drivetrain is completed
New AFM
I replaced the AFM simply because I suspected the internal variable resistor that senses the position of the airflow-valve to be worn. The symptoms are easy to detect, i.e hesitating of the throttle in a certain speed-band, in my case between roughly 50km/h and 100km/h, but others may vary. It is not a cheap part (360 Euro ex VAT), but in my case well worth the investment since the engine hesitation has disappeared for more then 95%. The last 5% is caused by the intrinsic nature of individual throttle bodies and incorrect CO adjustment. Conclusion: AFM replacement is well worth the cost.
Emmisions test
Shortly after my arrival at the workshop, the E28S was connected to the calibrated Sun analyser. Initial CO value was as low as 0,5%. In itself this is OK as BMW specifies any value up or equal to 1,5%. However, 0,5% is too low for a well running M88/3, which might explain some of the hesitation left. So we adjusted the CO to ~1% and saw the following values.
- CO (%): 0,9 - 1,2 [<=1,5%]
- CO2 (%): 12-12,8 [<14%]
- hc (ppm): ~700 [<300]
- vol O2 (%): 2-3 [close to zero]
- lambda: 15,5 [14,7]
Value's in brackets are the criteria. I'll ignore the lamda value as the M88/3 does not have a catalyst.
The value for the 'CO2' is a bit to low, but not that far off. The value for 'hc' is too high and so is the value for the 'O2'. Increasing the CO even further would only result into a higher 'hc' reading. But even so, the combustion is not 100%. For a Dutch registration, the above test results will do as a car from 1985 only has to fullfill CO requirements for which 1% is low enough.
Since I knew the old AFM wasn't working as intended and the throttle bodies have been replaced in 2005, I expected that I had to adjust the bypass screws first. These are now placed in 'factory default' due to which the combustion per cylinder varies. This explains for the remaining hesitation that can be noticed at idle. A 1% CO can perfectly be used to adjust the bypass screws to the average value of the sum of all six cylinder's vacuum readings. This must improve the 'hc' and 'O2' values significantly.
Raymond, I have been following this thread with great interest and you are doing a fantastic job.
One question though, where did you get a brand new AFM for that price? I priced one from BMW last week and they wanted 878 Euro incl Vat and a 10% BMWCC discount. I even checked the price in the UK and it was £570. Is your part brand new from BMW
Last edited by Bayerische; 20th April 2008 at 19:49.
One question though, where did you get a brand new AFM for that price? I priced one from BMW last week and they wanted 878 Euro incl Vat and a 10% BMWCC discount. I even checked the price in the UK and it was £570. Is your part brand new from BMW
Yes, it is a brand new BMW part supplied by my BMW dealer. I paid the price that is listed in the BMW pricing information for my country, which equals to 360 Euro ex VAT. I got a 20% discount so my nett price is about the same.
I already knew from the E34S HC91 guys that BMW UK pricing of spare parts is inconsistant when compared to the mainland, but a difference of a factor two is plain ridiculous. If you like, I can try to get one for you from my dealer. PM me if you are interested.
Yes, it is a brand new BMW part supplied by my BMW dealer. I paid the price that is listed in the BMW pricing information for my country, which equals to 360 Euro ex VAT. I got a 20% discount so my nett price is about the same.
I already knew from the E34S HC91 guys that BMW UK pricing of spare parts is inconsistant when compared to the mainland, but a difference of a factor two is plain ridiculous. If you like, I can try to get one for you from my dealer. PM me if you are interested.
Thanks Raymond,
That is a huge difference in pricing. A Dutch colleague of mine at work lives in Amsterdam and he goes home once a week on his days off, so I could get him to pick one up for me, but I appreciate the offer. If there is that much difference in parts prices, I will get him to buy all of my BMW parts.
My car has symptoms similar to yours with a slight hesitation when the throttle is pressed. The specialist that i bought the car from had taken the AFM apart and sealed it up again with silicone even though this is a non repair sealed unit, but I won't go on, this thread is about your car, not mine.
Linear Mode
