E89 Z4 Track-ready Sleeper Build

[Asbjorn]

The videos you post are incredible. You are flying through the course. Your Accusump certainly kicks in often, you weren't joking.

I am in awe of how much data you collect and how you are constantly improving. I am gracious you share this journey with us.

Really appreciate it @derekgates

Just for the record, the siren you hear at some parts of the track is just a warning that the oil pressure has dropped below 50psi or so. I still dont have an actual accusump. I just dont mash the pedal too hard when I hear the siren. It would also warn me if I had an oil line bursting causing oil pressure to drop. But the system is only turned on when on track, because otherwise the siren would sound all the time when idling, like at a stop light.

 

[derekgates]

Really appreciate it @derekgates

Just for the record, the siren you hear at some parts of the track is just a warning that the oil pressure has dropped below 50psi or so. I still dont have an actual accusump. I just dont mash the pedal too hard when I hear the siren. It would also warn me if I had an oil line bursting causing oil pressure to drop. But the system is only turned on when on track, because otherwise the siren would sound all the time when idling, like at a stop light.

Ah crap, sorry... got my signals mixed. That's a fantastic idea.

Everyone has me fearing EVER taking my car to the track, the logs don't lie that we have a serious problem with left turn Gs.


If I am remembering correctly, you experimenting with baffling, different pickup and everything BUT Accusump?

 

[fmorelli]

I like the heat maps and the x-y plots. I'm not sure they are super informative, per se, but an insightfully different way of looking at the data, and I like them. Often looking at something in a different way surfaces new information. Your ride height sounds good - the Z4 is sort of squatty in the rear to begin with. Scary part is that you are running 275 semi-slicks and low-mid level FBO power (given fuel quality and such) ... and still you wouldn't mind more rear grip. This is a platform that tends to overly focus on WHP and straightline performance ... which is not what these cars were built for ... and you are demonstrating :-D.

Filippo

 

[Asbjorn]

Ah crap, sorry... got my signals mixed. That's a fantastic idea.

Everyone has me fearing EVER taking my car to the track, the logs don't lie that we have a serious problem with left turn Gs.


If I am remembering correctly, you experimenting with baffling, different pickup and everything BUT Accusump?

Yes I tried different shapes of baffling as well as having a pump move the oil from the front of the pan to the rear under braking. All to try and avoid running an accusump. Also installed a dipstick to make sure I could read the oil level more accurately.

One question for you guys. I calibrated my dip stick to around 7qts of oil. At that level, the oil will be just above the tip of the oil temperature sensor. Judging by below pictures, that is about the same height as the floor of the front of the baffle. And definitely below the AN outlet for the oil pump.

@AzNdevil suggested that I can easily add more oil without having it getting in contact with the crank. What do you guys think? The fact that I was able to run such a tall baffle wall previously, suggests to me that there is at least half an inch of room.

I might be worth trying to overfill the pan, and see if it helps at all.

 

[Asbjorn]

I like the heat maps and the x-y plots. I'm not sure they are super informative, per se, but an insightfully different way of looking at the data, and I like them. Often looking at something in a different way surfaces new information. Your ride height sounds good - the Z4 is sort of squatty in the rear to begin with. Scary part is that you are running 275 semi-slicks and low-mid level FBO power (given fuel quality and such) ... and still you wouldn't mind more rear grip. This is a platform that tends to overly focus on WHP and straightline performance ... which is not what these cars were built for ... and you are demonstrating :-D.

Filippo

Well I guess the weight does not help either. And speaking of data, I finally had the car corner weighted last week.

Key conclusions:
Weight with 90% fuel and 10kg of luggage rear: 1655kg 3648lbs 50.3/49.7% f/r
Weight with me in the car and open roof: 1734kg 3823lbs 49.6/50.4 % f/r
Amount of weight that moves from front to rear when opening the roof: 10kg

Some factors to consider:
- Stock seats
- Stock interior w/iDrive, 11 speakers, 6 disc CD shuffler etc
- DCT
- A total of 4 extra coolers compared to stock (1x dct cooler + pump, 1x oil sump cooler + pump, 2x small aux radiators)
- Larger FMIC and engine oil cooler
- Larger sway bars
- Water injection system (w pump)
- External water spray system (w pump)

I already had lighter seats previously, and ended up going back to stock because I missed the adjustability and seat heating. But I guess sport seats is the fastest way to get rid of 60-70 lbs. Any other suggestions would be more than welcome.

All the stock sound dampening is still in place, but besides the hood, I am not sure if they account for much weight anywhere. People also say the N54 sounds pretty terrible from the engine bay side haha. Obviously the doors and trunk are pretty heavy as well, but I do not have the imagination to make those lighter. Even completely removing the roof sounds easier buuuut...

For inspiration, my friends Z4 35i 6MT with aftermarket sport seats and lighter wheels came out at around 1530kg 3373lbs. No cooling mods and obviously no DCT.

 

[derekgates]

I like the heat maps and the x-y plots. I'm not sure they are super informative, per se, but an insightfully different way of looking at the data, and I like them. Often looking at something in a different way surfaces new information. Your ride height sounds good - the Z4 is sort of squatty in the rear to begin with. Scary part is that you are running 275 semi-slicks and low-mid level FBO power (given fuel quality and such) ... and still you wouldn't mind more rear grip. This is a platform that tends to overly focus on WHP and straightline performance ... which is not what these cars were built for ... and you are demonstrating :-D.

Filippo

Great points here.

I've been working towards a more responsive power output instead of raw power with my car. It seems like the community is infatuated with high HP! Right now I am mainly SCCA SOLO for my 'track days' and throttle response is far more important than power....


Further, I worked towards FINALLY going with a square wheel setup; 255 all around. I worry that isn't enough rubber for the actual track but lighter wheels and being able to rotate them was a win in my book.

(Made in China of course! Fitting for this thread, lol)

Yes I tried different shapes of baffling as well as having a pump move the oil from the front of the pan to the rear under braking. All to try and avoid running an accusump. Also installed a dipstick to make sure I could read the oil level more accurately.

One question for you guys. I calibrated my dip stick to around 7qts of oil. At that level, the oil will be just above the tip of the oil temperature sensor. Judging by below pictures, that is about the same height as the floor of the front of the baffle. And definitely below the AN outlet for the oil pump.

@AzNdevil suggested that I can easily add more oil without having it getting in contact with the crank. What do you guys think? The fact that I was able to run such a tall baffle wall previously, suggests to me that there is at least half an inch of room.

I might be worth trying to overfill the pan, and see if it helps at all.

View attachment 45548

View attachment 45549

Woah, you went further than I remember. That really sucks with ALL OF THIS you are still getting the siren songs.

My gosh, you ALSO have a pump moving oil to the pickup... wow.

Track days are going to destroy my bearings. DOOMED.

(Sorry, I have absolutely no advice on oil level )

Well I guess the weight does not help either. And speaking of data, I finally had the car corner weighted last week.

Key conclusions:
Weight with 90% fuel and 10kg of luggage rear: 1655kg 3648lbs 50.3/49.7% f/r
Weight with me in the car and open roof: 1734kg 3823lbs 49.6/50.4 % f/r
Amount of weight that moves from front to rear when opening the roof: 10kg

Some factors to consider:
- Stock seats
- Stock interior w/iDrive, 11 speakers, 6 disc CD shuffler etc
- DCT
- A total of 4 extra coolers compared to stock (1x dct cooler + pump, 1x oil sump cooler + pump, 2x small aux radiators)
- Larger FMIC and engine oil cooler
- Larger sway bars
- Water injection system (w pump)
- External water spray system (w pump)

I already had lighter seats previously, and ended up going back to stock because I missed the adjustability and seat heating. But I guess sport seats is the fastest way to get rid of 60-70 lbs. Any other suggestions would be more than welcome.

All the stock sound dampening is still in place, but besides the hood, I am not sure if they account for much weight anywhere. People also say the N54 sounds pretty terrible from the engine bay side haha. Obviously the doors and trunk are pretty heavy as well, but I do not have the imagination to make those lighter. Even completely removing the roof sounds easier buuuut...

For inspiration, my friends Z4 35i 6MT with aftermarket sport seats and lighter wheels came out at around 1530kg 3373lbs. No cooling mods and obviously no DCT.

!!!

That's a significant increase in weight. @suspenceful went through quite a bit of weight reduction with his 1 series. The sunroof, shockingly, was around 40lbs if I remember. He started some of that around https://www.spoolstreet.com/threads...d-thread-5-years-of-ownership.2011/post-78212

Your car is wildly different with the roof mechanism and quite a bit more 'posh items'


I've considered finding an M3 headliner and deleting my sun-roof, inserting a panel instead. I like my creature comforts too much to remove the rest of the interior... but obviously I don't track my car (yet).

 

[Eracer76]

Thanks for this thread, it is all very informative, and now I just need to find the time to read the whole thing someday!!
Because my next round of mods is going to be more suspension mods, and engine cooling.

I definitely went a little overboard and my car is already stripped down big time!
It all started when my top quit working over a year ago, and I ended up just removing the complete hard top/system and everything associated with it... and from there it just snowballed! LOL

Here's a quick list of my confirmed weight reduction, someday I want to total up all the parts, and weigh the car after its all done...

The complete hard top and system
All 4 power windows/tracks/motors
Door handles, fuel door/gas cap/hoses, antenna, all the emblems and window slots are professionally shaved smooth
Stock fuel tank in favor of a 10 gallon fuel cell
Stock power seats/air bags in favor of lightweight racing seats
Stock retractable seat belts in favor of lighter racing harnesses
All the air bags and module
Plastic pieces underside of the dash
Complete idrive stereo system, harness and every module associated with it, including all 3 antennas
Electronic suspension system and module in favor of adjustable coilovers
Complete electronic parking brake system, harness and module
BMW Performance big brakes, the calipers are lighter, but rotors are a little heavier, probable a wash...
Rotary forged wheels
Complete air conditioning system, condenser, compressor, lines etc...
Washer fluid tank, pump, lines and wipers
The whole adaptive HID headlight assemblies in favor of lighter after market LED headlights
Carbon fiber hood
Speedtech single turbo system and complete custom 3.5" exhaust system was actually a little lighter then the stock twins and all the associated parts/inlets/outlets/hoses, catted downpipes and the heavy stock exhaust system etc...

Right now its still at the body shop getting painted San Marino Blue Metallic

 

[Asbjorn]

Thanks for this thread, it is all very informative, and now I just need to find the time to read the whole thing someday!!
Because my next round of mods is going to be more suspension mods, and engine cooling.

I definitely went a little overboard and my car is already stripped down big time!
It all started when my top quit working over a year ago, and I ended up just removing the complete hard top/system and everything associated with it... and from there it just snowballed! LOL

Here's a quick list of my confirmed weight reduction, someday I want to total up all the parts, and weigh the car after its all done...

The complete hard top and system
All 4 power windows/tracks/motors
Door handles, fuel door/gas cap/hoses, antenna, all the emblems and window slots are professionally shaved smooth
Stock fuel tank in favor of a 10 gallon fuel cell
Stock power seats/air bags in favor of lightweight racing seats
Stock retractable seat belts in favor of lighter racing harnesses
All the air bags and module
Plastic pieces underside of the dash
Complete idrive stereo system, harness and every module associated with it, including all 3 antennas
Electronic suspension system and module in favor of adjustable coilovers
Complete electronic parking brake system, harness and module
BMW Performance big brakes, the calipers are lighter, but rotors are a little heavier, probable a wash...
Rotary forged wheels
Complete air conditioning system, condenser, compressor, lines etc...
Washer fluid tank, pump, lines and wipers
The whole adaptive HID headlight assemblies in favor of lighter after market LED headlights
Carbon fiber hood
Speedtech single turbo system and complete custom 3.5" exhaust system was actually a little lighter then the stock twins and all the associated parts/inlets/outlets/hoses, catted downpipes and the heavy stock exhaust system etc...

Right now its still at the body shop getting painted San Marino Blue Metallic

Holy motherboard. Please share some pictures when you have time.

 

[Asbjorn]

I got a PM about oil pressure and dip stick installation, and I thought I would post a summary of my response here as well for others to see:

State of the N54 oil pressure issue
So we have two major problems on the N54 platform: Oil pressure dropping during braking and oil pressure dropping during left hand turns. And by drop I mean it falls to below a level that is equal to idle oil pressure at 70-80C oil temp. I have tried two methods which turned out not to work:

1. Different revisions of oil baffles - seems to help a little during hard braking, but it does not solve the problem. Also it does not help with cornering, where I speculate the main issue is the oil "rains" from the crankshaft at the wrong side of the pick up. The engine is mounted at an angle, and this would also explain why right-hand turns are never a problem.
2. Using an electric oil pump to move the oil from the front of the oil pan to the rear - this does not seem to help at all, most likely because the electric oil pump, while adequate for oil cooling, simply does not flow anywhere near enough oil to keep up with the engine oil pump.

The only "solution" that is known to work is the accusump, which I have not tried myself. Of course the S55 / N55 M solution should work as well, but not for N54, as you need that strong engine driven auxiliary oil pump to move the oil from the front of the pan to the rear. Without that pump, I do not recommend installing any type of baffle.

If you regard the dip stick as a potential solution, it must be because you would use it to accurately overfill the sump. It is not something I have experimented with myself. I simply use it to make 100% sure that the oil is at the top "stock" level before any track session. If stock is 6.5L I might be just below 7L, but I have never experimented with something like, say, 8L.

For now, my solution has been to avoid left hand (counter-clock-wise) tracks and I mostly sign up for time attack competitions and/or classes where they only allow semi-slicks. This so that I do not have to compete against cars that use full slicks. That being said, I am going to try full slicks this weekend just for fun. Lets see if I end up regretting that haha.

Oil dip stick installation
The N55 solution involves removing the sensor which I wouldn't recommend for N54. I am attaching pictures of how we did it on mine. It involves cutting and welding. Also care must be taken when adjusting the length of the stick, because it might hit the sensor inside if too long. Other than that it is pretty straight forward, and there is plenty of space above the pan for the stick tube itself.

 

[Asbjorn]

Just wanted to share some recent track day and time attack pictures. Was very happy to set a new personal record on semi-slicks at Guangdong International Circuit (1.26) a few weeks back. I have now moved on to full slicks to see how far I can get at the last time attack round end of December.

Recently @carabuser has been incredibly helpful in retuning my a map for the GC lites and the track use. Here are a few of the highlights that I am incredibly happy with from a drivers perspective:

1. Better throttle response.
2. Smoother boost control, making the car more predictable out of corners
3. Much smoother DCT shifts
4. Less timing corrections (less power at some RPMs)
5. More more stft flatlining post shift (seems cured by having STFTs close to zero)
6. Burbles totally disabled in DSC=off / normal mode (which I like on the track). Burbles still there in sport (which I only ever use on street)
7. Exhaust flaps only closes in 7th and only when the roof is up.
8. Adjustments to coolant and oil limits - much lower than stock for extra safety, but not so low that I cant finish an entire hot lap.
9. More DME safety enabled (throttle closure on over-boost is back) and more correct torque reporting overall.

Otherwise the car has been incredibly reliable this year, and I am mainly going through minor adjustments on the handling side to find those extra seconds/tens on track (such as sway bar adjustments, bump-stop adjustments, damper and spring adjustments etc).

 

[fmorelli]

Congrats on the reliability observation for the past year - likely the biggest accomplishment! No easy feat.

Curious what was your best time prior (compared to the above 1.26)? And what were the general car changes between that time and this last one?

Again, congrats!

Filippo

 

[aus335iguy]

Congratulations on the PB.

 

[Asbjorn]

Congratulations on the PB.

Congrats on the reliability observation for the past year - likely the biggest accomplishment! No easy feat.

Curious what was your best time prior (compared to the above 1.26)? And what were the general car changes between that time and this last one?

Again, congrats!

Filippo

Thanks alot!

I went from 1.28 in July to 1.27 in August and finally hit 1.26 in November using the same tires. When I look at the data, the improvements are mainly driver related. Another small part is related to the weather getting cooler and power going up slightly. Also stiffening up the rear and softening the front means less tendency to under-steer overall, and I moved the brake bias forward by swapping pads. Moving the brake bias did not change the braking distance, but it did change the stability of the car, making it easier to get weight transfer right before entering a corner. Before the ABS was really only working the rear tires. However it also increases the chance of understeer when trail-braking, and now the ABS is only really working the front tires, so I need to dial it a bit back again, more on that below.

Here's the setup before

Here's the setup now

Summary of changes

1. Increased rear spring rate (HR vs Eibach), not sure by how much because both springs are progressive
2. Increased rear ride height and overall rake. When I write +13mm above, it is compared to stock M sport.
3. 1 step softer front sway bar setting
4. Less toe out front, around zero now
5. The equipment says the camber got reduced up front, but in reality the setting is the same, probably a measurement error, or caused by the previous toe out somehow.
6. Changed front brake pads from EBC orange (0.5-0.6mu) to Hawk DTC70 (0.7mu). However I believe most of the change in brake balance came from replacing the front rotors together with the pads. They were pretty worn before and I dont think the EBCs ever bedded in properly. My brake bias is a bit too front heavy as of now, so I want to replace the rears with DTC70 as well.

 

[Illsic_Design]

Congrats on the new PB, car seems to be going well.

So what's the consensus on an oil pan baffle? Should we install one or not at all? Going to be doing my rod bearings in a few weeks and wondering if I should or shouldn't put in a baffle?

 

[Asbjorn]

Congrats on the new PB, car seems to be going well.

So what's the consensus on an oil pan baffle? Should we install one or not at all? Going to be doing my rod bearings in a few weeks and wondering if I should or shouldn't put in a baffle?

So far, the data I have been exposed to tells me that:
Baffles don't solve the problem, but might help a tiny bit during braking. But again, it is not a solution.
Adding more oil doesn't solve the problem (tested on N55)
Returning oil from the front of the pan to the rear with an electric oil pump is not a solution either.

Recommendations sorted by cost
S55 engine swap
M-version of N55 engine swap
Accusump
Use AD08r or similar TW200+ tires that can handle track-abuse without offering too much grip
Avoid tracks with left-hand turns and long heavy braking zones

 

[aus335iguy]

Or the most economical fix.... dry sump conversion lol

 

[Lurcher]

How far can this go on this chassis?

 

[Asbjorn]

How far can this go on this chassis?

How far can what go exactly?

 

[Lurcher]

How far can what go exactly?

At what point do you say enough and get an M3/1M/etc. ??

 

[Asbjorn]

At what point do you say enough and get an M3/1M/etc. ??

Well I myself would not, because it would not make sense for me.
But it is an interesting question, let me divide it up into different topics:

If ultimate laptimes are important
If you want to set the fastest laptime, the limit will always be power+tire-to-weight ratio. If the car weighs less, it is like having bigger tires and more power. So yes a 1M would eventually end up being faster than any Z4, because it is lighter and fits larger tires. Then on the other hand it is no match for a tuned cayman or M2C/M4. The below table explains why.

Rank and type	Weight	Power	Tires	Power-to-weight ratio, tire to weight ratio	lap-times
1st 718 Cayman / boxster 2.0T PDK	1,360kg 3,000lbs	380hp with a tune	265/285	reference	reference
2nd M2C/M4 DCT	1,630kg 3,600lbs +20%	500hp with a tune	285/305 +7%	+10% power to weight -10% tire to weight	+0s depending on track layout
3rd 1M Coupe	1,520kg 3,351lbs +12%	400hp with a tune	275/295 +3%	-7% power to weight -7% tire to weight	+1-2s
my Z4 DCT	1,650kg 3,637lbs +21%	400hp with a tune	275/275 +0%	-14% power to weight -14% tire to weight	+2-3s

The reason I put the cayman up there is to show that although yes, you could tune for more power, it is not necessarily the most important laptime factor. Sometimes I dream about doing a full GT3 kit with fixed roof etc. But it would still be a relatively heavy car, and the weight distribution would never be quite as good as the cayman anyhow.


If developing as a driver is important
Except during the winter, you really only get one lap with my car, or any N54-based track cars for that matter. Water temps will go up, and you will loose power from the second lap. Does that matter if you are an excellent driver who can set a perfect lap in one go? No! Does it matter if you are a new driver trying to learn? Absolutely. The S55 or porsche platforms are much better for that. Also lets not forget about the oil pressure issues...

Personally I just use karting instead...


If doing something unbelievable is important
Well here's the thing. Drive fast in a 911 GT3 RS, and everyone talks about the car and how you have too much money. Drive fast in a stock-looking Z4 that took over two years to dial in... well it is just a very different experience!

Here's the current leader-board at the circuit (GIC). It gets reset annually, and not all of the strongest drivers have shown up yet, but still. It shows the fastest car from each class and sorts by laptime:

In the end, what matters to me is that I like the Z4. I like how it feels to drive, and I like how it looks. I do not really want to drive a Boxter. It just doesn't speak to me. And while I admire the M4, I think it would be a waste to get one with a convertible roof. It is already heavy enough as is. Do I want more power and less weight? Sure, but only if I can get it from my Z4 and without ruining the car.