Fan Delete, 1997-1998 2.8L Z3

[DuWop]

THREAD SUMMARY:
What is necessary to delete the clutch fan?
1) Remove the fan then close the hood.
2) to be continued




I've decided to delete the mechanical fan to prevent damage due to it exploding. I'm not after HP gain/performance. I'm to old for the track but I do put my foot in it occasionally.

My Bentley service manual (1996-1998 Z3 roadster) electrical wiring diagram, ELE-40 has the circuit for the auxiliary fan. Credit to Bentley Publishing. https://www.facebook.com/photo.php?f...type=1&theater

The normal speed and high speed relays are interlocked so the high speed and normal speed wires to the motor can not both be energized at the same time.

WRONG, read the following for information only: It looks like the best/easiest way to install a relay is for it to provide a ground to the high speed fan relay coil that closes the contacts (ground) at around 185 F cylinder head temperature, which will start the OEM auxiliary fan on high speed.

I'm installing a 180 F thermostat. At 83 F ambient my oil pressure was 20 psi lower than specified (60 psi) with the OEM 198F thermostat while using 5W-30 synthetic oil. BTW, with 15W-30 Mobile 1 oil, the oil pressure is 60 psi with the 198 F thermostat. Mobile 1 recommends 10W-40 for the Z3 2.8L engine for all seasons 180 F thermostat: http://www.rockauto.com/catalog/more...766&cc=1313663



The added relay providing a ground to energize the high speed relay coil to start the auxiliary fan on high speed at 185 F will not interfere with the engine cooling circuits other functions / AC etc. The auxiliary fan will start on normal speed on demand if the high speed relay coil is not energized.

The normal speed relay should never get a start signal from the 196 F OEM temperature switch because the fan will already be running high speed/cooling the engine, anyway the normal and high speed relays are electrically interlocked which would prevent the normal speed wire from being energized when the high speed relay is energized. No interference.

To operate the auxiliary fan I intend to install the TM-4 (single temperature sensor) which gives me an adjustable engine over temperature audible alarm, and an adjustable fan start relay. The sensor will be installed on the hottest predicted (loss of coolant flow) location on cylinder head(center).
http://enginewatchdog.com/tm4.html

I might install a mechanical engine over temperature switch warning light in case of fan failure. Also I have the OEM temperature gauge (that I seldom look at) for back up.

It will be a few months until I'm ready to go with this. If you know of a problem with my plan please let me know.

BTW: There are two problems I'm aware of when using a high viscosity motor oil during extremely cold weather. One is collapsing the oil filter. The other is loss of suction to the oil-pump because the oil in the oil pan is to thick to flow. It seldom gets extremely cold here. I guess it would be a good idea during extremely cold weather to let the engine idle until warmed before driving.

Well maybe three problems "The main use of ZDDP is in anti-wear additives to lubricants such as greases, gear oils, and motor oils, which often contain less than 1% of this additive. It has been reported that zinc and phosphorus emissions may damage catalytic converters and standard formulations of lubricating oils for gasoline engines now have reduced amounts of the additive, though diesel engine oils remain at higher levels.^[3] Crankcase oils with reduced ZDDP have been cited as causing damage to, or failure of, classic/collector car flat tappet camshafts and lifters which undergo very high boundary layer pressures and/or shear forces at their contact faces, and in other regions such as big-end/main bearings, and piston rings and pins. Roller camshafts are more commonly used to reduce camshaft lobe friction in modern engines. There are additives, such as STP(R) Oil Treatment, and some racing oils such as PurOl, Brad Penn and Valvoline VR-1, which are available in the retail market with the necessary amount of ZDDP for engines using increased valve spring pressures. The same ZDDP compounds serve also as corrosion inhibitors and antioxidants." http://en.wikipedia.org/wiki/Zinc_di...e#Applications

"The important element here is the phosphorus since it is the active antiwear additive. That's why we show phosphorus as well as zinc. The zinc content is in the range of 0.12 - 0.13 weight percent (1200 - 1300 ppm). (Mobil 1 Extended Performance 15W-50 [gold cap] was discontinued about May 2009.

http://www.mobiloil.com/USA-English/..._Products.aspx

[rf900rkw]

Don't bother with the cylinder head temp sensor, as it will do no good. The fan does not cool the engine, it cools the radiator. BMW already supplied a sensor on the radiator that does the job well. If you want to do something, replace the radiator switch with a lower temp one.

[Blacklane]

I just used a relay from the-fan-man.com and mounted it in the secondary air pump bay. There is already 12v in there and it's an easy wire-run to the temperature switch on the side of the radiator and to the fan.
I'm considering adding a second temperature switch to the bottom radiator hose. Several e-bay sellers have aluminum sleeves that can be spliced into the hose and are threaded for a temp switch. That would make the electric fan system completely redundant to the aux fan.

[DuWop]

Don't bother with the cylinder head temp sensor, as it will do no good. The fan does not cool the engine, it cools the radiator. BMW already supplied a sensor on the radiator that does the job well. If you want to do something, replace the radiator switch with a lower temp one.

Thanks for the info. Where can I find a temp switch with the correct temp settings. I want the fans on slightly above 180 F.

Is this the same OEM switch that currently starts the normal speed fan (196 F) then the high speed fan at a higher temp (210 F) on the Z3 2.8L.? Two switches in one sensor?

I looked at the fan delete kit but it was for the M and I thought it might not work for the Z3.

[steve f]

try p/n 61-31-8-376-440. You'll need to trim the alignment tab inside the switch connector to get it to fit.

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I think it comes on @177 degrees

[DuWop]

I just used a relay from the-fan-man.com and mounted it in the secondary air pump bay. There is already 12v in there and it's an easy wire-run to the temperature switch on the side of the radiator and to the fan.
I'm considering adding a second temperature switch to the bottom radiator hose. Several e-bay sellers have aluminum sleeves that can be spliced into the hose and are threaded for a temp switch. That would make the electric fan system completely redundant to the aux fan.

Do you supply power to the fan motor (high amperage) from the 12 V wire in the secondary air pump bay? I don't understand your wiring set up?

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try p/n 61-31-8-376-440. You'll need to trim the alignment tab inside the switch connector to get it to fit.

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I think it comes on @177 degrees

Thanks. 177F set-point is close enough.

This is it. If the threads match I can handle the rest. http://www.pelicanparts.com/cgi-bin/...FSho7Aodc1EACg

Does the switch have two sets of contacts. One set for the normal speed relay and the other for the high speed relay?

[Blacklane]

There is a big +12v power lug under the battery terminal in the Secondary Air Pump bay. I connected the main power there, through an in-line fuse holder with a 30A fuse, to the relay mounted inside the bay on the engine side, then out of the bay along the inner fender to the fan on the radiator. The temperature switch is on that side of the radiator as well, and I ran the low-current wire to the relay the same way. I kept the wires away from the engine, since this is the exhaust side of the engine. There is an existing wire harness along the fender that you can tie to.

[DuWop]

There is a big +12v power lug under the battery terminal in the Secondary Air Pump bay. I connected the main power there, through an in-line fuse holder with a 30A fuse, to the relay mounted inside the bay on the engine side, then out of the bay along the inner fender to the fan on the radiator. The temperature switch is on that side of the radiator as well, and I ran the low-current wire to the relay the same way. I kept the wires away from the engine, since this is the exhaust side of the engine. There is an existing wire harness along the fender that you can tie to.

Thanks

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It just occurred to me that a temperature switch with normal and high speed fan contacts isn't necessary although it would have it's advantages, mostly leas wear on the fan motor when running on normal speed.

If using a temperature switch with only one set of contacts, I could disconnect the normal speed relay coil ground wire from the temperature switch, and connect the switch to the high speed relay's coil ground wire. The fan would still operate at normal speed for the A/C condenser, then when the switch sees 177 F it would energize the high speed relay, which disconnects power to the low speed relay's contacts, denergizing the normal speed feed to the fan. The fan would be running at high speed.

It appears that instead of a resistor for operating the Z3 2.8L aux fan on normal speed, there must be two sets of motor windings. One for normal speed and the other for high speed, and the BMW engineers' design prevents both windings from being energized simultaneously. I guess that maybe energizing both windings simultaneously would damage the motor.

Although the 177 F temperature switch will satisfy my needs I'm going to install the TM4 because I want to monitor cylinder head temperature which is the hottest part of the engine. I may as well install a relay controlled by the TM4 in parallel with the 177 F temperature switch's contacts (on the radiator) because during a loss of coolant accident the radiator temperature might be much less than the engine's temperature. Given the air flow from the fan will not help much during a loss of coolant accident, but a little air flow is better than no air flow. Also as long as there is steam in the coolant system the water pump acts as a steam pump, circulating the steam into the radiator where it condenses then flows back to the engine. Perhaps this would prevent a total melt down resulting in an engine best used as a boat anchor. Yes I over analyzed this. I'm sure I would have shut down the engine long before this mess developed. The steam coming from under the hood would be a good clue to shut the engine down.

Back in the good old days they built engines without water pumps. They depended on natural circulation to keep them cool. Of course many of these engines weighed several thousand pounds and produces around 1 hp. To start them they heated a nail red hot then stuck it in a hole in the cylinder head, then they gave the massive flywheel a spin and it started chugging.

[Blacklane]

The aux fan in front of the radiator has a big resistor attached to it. The normal-speed circuit goes through the resistor, the high-speed circuit simply by-passes it. I don't see any reason to disable this function. I did swap-out the temperature switch with the lower-temperature switch mentioned by steve f above. It's still a dual-temperature switch and the circuit works the same, only at lower temperatures. (The stock temperature switch is 91c/99c or 196F/210F).
No amount of airflow will help save an engine with no coolant. You might have some success with iron, but not with an aluminum block and head. I don't think that should be your design goal. Creating a redundant system has merit, however.
Also note that there is an engine over-temperature light that comes on at 125c (257F) as measured by the block coolant temperature sensor monitored by the DME.

[steve f]

I'm running my 98 M with fan delete and the lower temp two speed switch. Even in low speed stop and go traffic, I don't notice any heat related issues with this install. I deleted the plastic fan as an emergency fix because I was hearing a rattle from the fan clutch on cold start-up.

This winter, I plan on doing a complete refresh of the cooling system though. This project will most likely include the Zionsville Euro radiator and oil cooler, Stewart pump and the lower temp thermostat.

Just sharing my experience in the hope it will provide you with a margin of comfort.

[rf900rkw]

Yes. I run a supercharged S52 with a fan delete. Everything else is stock, save the aluminum radiator. Literally removed the fan and closed the hood.

[DuWop]

The aux fan in front of the radiator has a big resistor attached to it. The normal-speed circuit goes through the resistor, the high-speed circuit simply by-passes it. I don't see any reason to disable this function. I did swap-out the temperature switch with the lower-temperature switch mentioned by steve f above. It's still a dual-temperature switch and the circuit works the same, only at lower temperatures. (The stock temperature switch is 91c/99c or 196F/210F).
No amount of airflow will help save an engine with no coolant. You might have some success with iron, but not with an aluminum block and head. I don't think that should be your design goal. Creating a redundant system has merit, however.
Also note that there is an engine over-temperature light that comes on at 125c (257F) as measured by the block coolant temperature sensor monitored by the DME.

"Also note that there is an engine over-temperature light that comes on at 125c (257F) as measured by the block coolant temperature sensor monitored by the DME."
Thanks, that's good to know.

My design goal is to get rid of the clutch fan before it explodes and make the car a reliable as possible.

I found the switch set-points for Pelican part no. 61-31-8-376-440 :

Category:		Radiator
Description:		Double temperature switch
Quantity Required:		1
Notes:		(from March 1997) For vehicles with air conditioning or automatic air conditioning 80/88 Celcius, 176 F / 190F http://www.pelicanparts.com/cgi-bin/...FSho7Aodc1EACg Does anyone know if the threads are the same as the OEM temperature switch on my 1998 Z3 2.8L? As soon as I know I'm placing my order. I MEASURED THE THREAD AFTER THE SWITCH ARRIVED. IT'S A M14 X 1.5 . The threads match the bung on my radiator.

[Blacklane]

That's the right part and should fit the radiator. I have that in my 2.8. You will have to trim off a small tab inside the plug for your plug to fit the new switch, though.

[DuWop]

That's the right part and should fit the radiator. I have that in my 2.8. You will have to trim off a small tab inside the plug for your plug to fit the new switch, though.

Thanks for the info. I'm placing my order now.

Thanks everyone.

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Because we were discussing relays being in stalled I thought I should post this warning for those that may not know. When the coil of a relay is de-energized a high voltage spike is induced in the coil power supply wires which can damage computers. The picture shows a diode in the circuit which protects the chip from the voltage spike. When you install a relay you need to take this into consideration. The striped end of a diode connects to the +.

https://www.facebook.com/photo.php?f...type=1&theater


Diodes http://Forums.bimmerforums.com/forum...-(E36-7-E36-8)

[Blacklane]

Many relays intended for DC applications (such as automotive) have diodes installed internally.

[DuWop]

"Also note that there is an engine over-temperature light that comes on at 125c (257F) as measured by the block coolant temperature sensor monitored by the DME."
Thanks, that's good to know.

My design goal is to get rid of the clutch fan before it explodes and make the car a reliable as possible.

I found the Double temperature switch switch set-points for Pelican part no. 61-31-8-376-440 :

Category:		Radiator
Description:		Double temperature switch
Notes:		(from March 1997) For vehicles with air conditioning or automatic air conditioning 80/88 Celcius, 176 F / 190F http://www.pelicanparts.com/cgi-bin/...FSho7Aodc1EACg

My new double temperature switch ( 176 F / 190F ) arrived today!!!!

This morning I thought of a problem. My thermostat opens at 180 F. and the normal speed switch will start the fan at 177 F. I will be cruising down the HW at 70 mph with my fan running on normal speed. If anything the fan motor will be acing as an electric brake for the fan blades because the fan would likely spin faster in the oncoming 70 mph wind than the little motor can spin the blade. This is not going to impress the women.

In stop and go city traffic I would like for the fan to start at 177 F. I'll have to work this out.

For basic knowledge of the VANOS (variable cam timing) operation, for those that don't know:
I thought I could use power to the VANOS solenoid to provide some speed interlocks but unfortunately at low speed the VANOS solenoid is de-energized, then energized at mid-range speeds (intake cam timing advanced 12.5 degrees), then de-energized at higher speeds. (likely for fuel economy I guess). See Bentley manual, 100-2, and 117-13) so that's out the window for a speed interlock for the aux fan. I hope ny next spring to have all the interlocks I want and monitor various temperature and pressure parameters using this little inexpensive gizmo: http://www.youtube.com/watch?v=_fNto4JOu4E

================================================== ====================

Copied and pasted here. I should have posted this here on this 2.8L Fan Delete thread.
Coolant system thermostat operation 101

My new 180 F thermostat arrived today and I almost had a panic attack because I thought they sent the wrong one. After I understood how they work (I think) I believe it is OK to install the new one. If you will look at the pic you will see that the OEM thermostat (198 F) on the right is longer than the new one.

Apparently the small end has a valve disc on it that retracts allowing re-circulation flow through the engine (keeping an even engine temperature) when the temperature is < 180 F, and the large valve on the large end of the thermostat is closed, blocking the flow from the bottom radiator hose to the water pump suction.

After the engine heats up >180 F the large valve opens and the disc on the small end of the thermostat moves toward the block, covering the <180 F condition engine's re-circulation flow hole (valve closes). I hope I am right about this and I don't have change it again later.

https://www.facebook.com/photo.php?f...type=1&theater

The difference I see in the two is the new 180 F thermostat will allow more <180 F re-circulation flow than the OEM thermostat. I don't think that's a problem

If you look at this picture you will see the OEM thermostat (on right) disc has a larger diameter than the new thermostat, and the OEM thermostat disc has slots in it. There is a re-circulation flow control valve disc behind the slots that is retracted allowing flow when the engine is < 198 F. When > 198 F the disc behind the slots moves toward the block, blocking re-circ flow. The slots meter re-circ flow.

The new thermostat (on left) doesn't have this re-circ flow metering feature. When the recirc valve disc is retracted a large amount of re-circ flow exist. Other than requiring a little more energy to spin the water pump due to greater flow I don't think it makes much difference.

If I'm wrong about this please let me know so I can exchange the thermostat before my radiator gets here. Predicted delivery Sept 13.

https://www.facebook.com/photo.php?f...type=1&theater

Last edited by DuWop; Yesterday at 09:52 PM.

[rf900rkw]

I explained this fully in one of your threads. Quit thinking of the cooling system as a static entity determined ONLY by engine outlet temperature.

[DuWop]

I explained this fully in one of your threads. Quit thinking of the cooling system as a static entity determined ONLY by engine outlet temperature.

The other thread wasn't my thread. This one regarding the 2.8L engine (mine) is the thread I started so I moved the 2.8L specific info here, although it likely applies to other engines.

The cooling system works by blending hot coolant (recirculated) with cold coolant (snarfed from radiator). Under normal conditions, which is very light load, most of the colant is recirculated with only small amounts of fresh cold coolant drawn from the radiator. The precieved notion is that the thermostat is closed until operating temp, then it opens wide and blocks off the bypass port. In reality, the thermostat is mostly operating in the middle to closed part of it's travel doing this blending. It only gets in the open ranges when the engine temp rises a little bit due to more load.

As far as the blending ratios you will get that new 'stat, I can't say.


And to tie this back to earlier in the thread. In low load no air flow conditions, ie sitting in traffic, the thermostat is regulating the recirculation, adding in a small amount of cold coolant from the radiator. As the cold supply is used it is replaced with hot coolant, obviously, and with no airflow, the hot coolant is not cooled. Thus the temp across the radiator will start rising as the cold is used up. When the hot gets to the cold side of the radiator, the fan switch will trip in and the fan will supply airflow to cool the radiator contents back down. During this whole process, the thermostat is constantly regulating, and engine temp is being maintained. Thus my constant chant of the fans cool the radiator, not the engine.

/,randy, thanks for an excellent explanation of the operation of the coolant system.

It appears the re-circulation will be greater with the new thermostat and require more of the engine's HP to operate the water pump. I guess this is something the guys racing would be concerned about.

All the after market thermostats for the 2.8L I could find a picture of were made like the one I bought. BMW may have a 180 F for the 2.8L.

Today I was wondering if there is a reason that I should have stayed with the 198 F thermostat. I think maybe I could have maintained OEM specified oil pressure with 10W 40 motor oil with the engine at 198 F. It would be close.

It's said that a hotter engine temperature is more efficient, but also more likely to knock. I can only get 87 octane no ethanol fuel in this area. I've red-lined the engine a few times on 87 octane and the knock sensors didn't back down the ignition timing.

Do the BMW's throw code if the knock sensors detect knock. My eclipse didn't. It just backed down the timing.

My Jeep Grand Cherokee's normal operating engine temperature is 210 F. It gets 25 mpg on the HW at 70 mph. Pretty good for a 4WD heavy vehicle. The 180 F thermostat may cost me a little at the pump but the engine will be less likely to knock on 87 octane. I think the engine will be happy with the 180 F operating temperature and 10W 40 oil.

The girl that owned the car before me used 5W 30 and apparently it didn't damage the engine with the oil pressure running 20 psi below factory spec. but I doubt she ran it hard, but who knows?

[rf900rkw]

Okay, I've been reading and posting for most of the last week from a phone on borrowed wifi in various medical establishments, so I've been a bit terse (former) and grumpy (later), and missed /mixed up some threads.

The fan switch is in the cold side of the radiator. It is monitoring the cool coolant being sent back to the engine. When this coolant reaches xxx degrees (say 180), that means the radiator is not doing it's job, likely due to a lack of air flow, and so the fan is turned on. If you have 180 degree coolant on the cold side of the radiator when driving down the road, there is something seriously wrong that a bit of fan will not help.


BMW knock sensing is more sophistcated than that. It's a very dynamic realtime system. You won't feel a sudden drop in timing. There just won't be quite as much power as there should have been. I would run the correct fuel grade, even if it means ethanol.

Since the thermostat controls the suction side of the waterpump, it's not really going to change the pressure/load. The bypass ratio is going to change the temp curve and the reaction time of the thermostat. The worst case is you'll end up with the temp yo-yo-ing as the thermostat has to over react to the temp changes. It never reachs a balancing point, and is slow to cover for load changes. With the M/S52, it's likely not a problem, but I'm not sure I would want to be messing with the later systems.

[steve f]

Okay... so I've been a bit terse (former) and grumpy (later),

After sorting through it all, I've found your information to quite valuable. I've subscribed to this thread so I will have it as good reference. Thank you.

BMW knock sensing is more sophistcated than that. It's a very dynamic realtime system. You won't feel a sudden drop in timing. There just won't be quite as much power as there should have been. I would run the correct fuel grade, even if it means ethanol.

Interesting, I find my DASC (92 octane recommended) runs better on 91 octane E0 than 93 octane E10

[DuWop]

Interesting, I find my DASC (92 octane recommended) runs better on 91 octane E0 than 93 octane E10

E10 has 2% less energy content than E0. E has 20% less energy than 100% petrol.

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The fan switch is in the cold side of the radiator. It is monitoring the cool coolant being sent back to the engine. When this coolant reaches xxx degrees (say 180), that means the radiator is not doing it's job, likely due to a lack of air flow, and so the fan is turned on. If you have 180 degree coolant on the cold side of the radiator when driving down the road, there is something seriously wrong that a bit of fan will not help.
.

Thanks for the info. As I understand what you said, the thermostat has modulated open before the temperature switch is sensing 177F. Cool. I have nothing about the 177 F fan start temperature setting to be concerned about. Thanks again.

[DuWop]

BMW knock sensing is more sophisticated than that. It's a very dynamic realtime system. You won't feel a sudden drop in timing. There just won't be quite as much power as there should have been. I would run the correct fuel grade, even if it means ethanol.

I hate ethanol. It has cost me a lot of money and work. I have 6 vehicles and only drive around 5K miles per year. My tank would be full of water. I'm sticking with E0, 87 octane. If I want to run the engine hard I'll pour in a bottle of octane booster. I don't think the 87 octane will cause me a problem considering most of the time I drive like an elderly lady.

In a month or so I will have my AFR gauge installed and be in control of AFR, then I think I can handle any problem the 87 octane might cause, if there is one.

Are the head gaskets solid metal? If so the block would be an additional heat sink for the cylinder head. It's said that aluminum heads allow more boost than cast iron heads so with our aluminum heads and 2.8L aluminum block sinking heat (assuming the gasket is all metal), Granny shouldn't have much worry about knock when burning 87 octane.

I wish there is a way for me to know if the knock sensors detect knock. Is there other than the loss of power?

BTW my Street Supercharging book says one should run 8:1 compression if using considerable boost. 9:1 for mild boost. I was wondering what compression ratio you have with boost and what your AFR is at WOT?

[Randy Forbes]

S-52 stock CR is 10.5:1 (S-54 is a lofty 11.5:1). I've run a similar setup to RandyW with a Dinan/Vortech centrifugal compressor peaking at about 7-1/2 to 8 psi. NickG supplied the tuning, and though I don't remember what the numbers were exactly, I do remember they were acceptable when I logged them with my Innovate LM1 meter.

I recently put a twinscrew supercharger on that same car, and the AFRs under almost every condition is a steady 14.4:1 (unfortunately, I am bound by my word to not disclose the tuning origins). I haven't put a boost gauge on it yet to see what it's pushing, but I'm sure it's more than the 8 psi that the Vortech produced! The cylinder head has had a very minor .003-.004" cut from it when I first went to a multi-layer steel headgasket (different surface finish requirement than the OE composite gskt) and I'm using a stock__.070"__MLS gskt thickness, though they're available in steps up to .120".

I've prewired it for auxilary gauges (water temp @ cyl head__mostly because I needed to plug a port to the throttle body that was deleted, and the temp sensor filled the bill__and oil pressure) before the twinscrew was installed, because you sure can't get at anything now! But I have been watching my oil temperature, and even *little bursts* on the highway it barely sees 220*F. The car has a complete S-54 oil cooling system installed about eight (8) years ago. Eventually, I'll add the water temp, oil pressure, boost pressure and a permanent AFR gauge in the interior, but I'm not in any hurry to cut those holes yet...

[rf900rkw]

An AFR gauge will tell you nothing of octane or knock. For knock, use a fast scanner with graphing capabilities to monitor the dynamic knock sensor and timing data. Of course, you'll need examples of what is good before you can tell what is bad.

I just love books with very specific specifications pulled out of the air, applied to every possible application evenly. The M/S52 series LOVES boost. I'm running stock 10.5:1 compression ratio, 10 PSI boost at readline. AFR is 11.9 at peak BMEP, tapering up to 12.5 at redline, except the test was run spraying pure water; I normally spray a 30% methanol/water mix.


Randy -- that's way too lean for WOT, and too rich for normal cruise. 14.7 cruise or you will destroy the cats; WOT into the 12s.

[Vintage42]

... It's said that a hotter engine temperature is more efficient, but also more likely to knock... I've red-lined the engine a few times on 87 octane and the knock sensors didn't back down the ignition timing. Do the BMW's throw code if the knock sensors detect knock... My Jeep Grand Cherokee's normal operating engine temperature is 210 F ...

Hot engines would knock in the days with no engine management. Nowadays low octane does not cause knocking unless the octane is so low that the knock sensors and engine management cannot cope with it.

How can you see your timing? I can see mine with the ScanGauge. Constantly changing every second, boring and meaningless.

If you are not using 87, the knock sensors are likely making the ECU reduce timing advance every time you use heavy throttle or high rpm. This dynamic control of timing does not generate codes. If a knock sensor fails, causing the ECU to not slow ignition advance and so allow prolong knocking, that might generate a code.

My 1.9L Z3 does not have a belt-driven fan, and its normal operating temperature is 175F when loafing along. My Forester and Scion xB are 190F. All three will go to 205F idling in a traffic jam, at which point their electric fans come on.