E89 Z4 Track-ready Sleeper Build

[F87Source]

Actually in my experience that doesn't sound like fuel starvation. Fuel starvation should produce a code that says something about injector cut out. And it is quite violent. There will also be a check engine light, and you'll have to turn the engine off and on again before continuing if I remember correctly.

If you do a normal 3rd WOT log, what does the hpfp curve look like? Does it drop way below say 2000psi?

Just saw the code, yeah it kind of looks like you HPFP is crashing.

Fuel starvation results in the engine completely shutting off if it is bad enough and you have to let the car sit for 10+ mins for the fuel to naturally flow back to the right side of the tank. If it is really bad you will need to add more fuel, and crank the car alot to purge all the air bubbles out of the lines.

 

[sancho78rus]

Here is the log of the problem session

datazap.me | sancho78rus | Igora2

datazap.me

 

[Asbjorn]

The new custom rear sway bar finally finished production and went in yesterday.

The back story here is that I had my front HR swaybar modified to be adjustable. This means it got a new stiffer setting and a new softer setting as well. I liked the new stiff setting alot. It felt great to drive on the street. However none of the settings would influence the balance of the car much. Even running the OEM sway bar front in combination with HR rear wouldn't dramatially change the balance of the car on track. And I always felt the rear was a bit soft with the HR rear sway bar, even in combination with the up rated Eibach springs (progressive 65N/mm - 131N/mm).

So in conclusion I wanted a stiffer rear sway bar. The HR was a solid 21mm piece, and the new bar is made from 24mm solid tubing instead. We also modified the angles a bit to get better clearance everywhere. The HR bar always looked a bit like an after-thought on the Z4.

According to below chart the stiffness should have gone up by 60%. Doesn't feel much different on the street though. Im sure the actual stiffness at the wheel is also different due to where it mounts on the suspension arm. Have to wait for the next track event this weekend to see how it actually performs.

 

[F87Source]

The new custom rear sway bar finally finished production and went in yesterday.

The back story here is that I had my front HR swaybar modified to be adjustable. This means it got a new stiffer setting and a new softer setting as well. I liked the new stiff setting alot. It felt great to drive on the street. However none of the settings would influence the balance of the car much. Even running the OEM sway bar front in combination with HR rear wouldn't dramatially change the balance of the car on track. And I always felt the rear was a bit soft with the HR rear sway bar, even in combination with the up rated Eibach springs (progressive 65N/mm - 131N/mm).

So in conclusion I wanted a stiffer rear sway bar. The HR was a solid 21mm piece, and the new bar is made from 24mm solid tubing instead. We also modified the angles a bit to get better clearance everywhere. The HR bar always looked a bit like an after-thought on the Z4.

View attachment 42238

View attachment 42239

According to below chart the stiffness should have gone up by 60%. Doesn't feel much different on the street though. Im sure the actual stiffness at the wheel is also different due to where it mounts on the suspension arm. Have to wait for the next track event this weekend to see how it actually performs.

View attachment 42237

Nice as always!
was labor expensive to get all this custom work done? Because I know here in Canada I would get absolutely destroyed with labor costs to do something like this.

 

[Asbjorn]

Nice as always!
was labor expensive to get all this custom work done? Because I know here in Canada I would get absolutely destroyed with labor costs to do something like this.

I sent my old HR sway bar to a factory in my city that produces this stuff. They charged me RMB 1400 for the one-off job. Incl shipping and installation we landed at around USD 280. It took some time to carefully take some material off the powerflex bushings due to the larger diameter.

 

[F87Source]

I sent my old HR sway bar to a factory in my city that produces this stuff. They charged me RMB 1400 for the one-off job. Incl shipping and installation we landed at around USD 280. It took some time to carefully take some material off the powerflex bushings due to the larger diameter.

WOW that is DIRT cheap, especially for a custom part.

Any chance you can hook me up with the name of these companies? I have a few things I would love to get done.

 

[Lurcher]

Impressed as always. Availability of inexpensive manufacturing and labor allows for so many things to be tried/tested. I'll go back to that statement about you starting a website as a manufacturer I mean, you just had a custom unit built and installed for the price of just the H&R swaybar (actually a little less) here in the US. Just think what Filippo would be doing....

 

[Asbjorn]

WOW that is DIRT cheap, especially for a custom part.

Any chance you can hook me up with the name of these companies? I have a few things I would love to get done.

Here's the bar factory.

https://rpaqcyp.m.tmall.com/

The guys who made the camber/caster plates are another company based in Tianjin. I don't think they have any website, or speak any English. Let me know what you need done.

 

[Asbjorn]

Impressed as always. Availability of inexpensive manufacturing and labor allows for so many things to be tried/tested. I'll go back to that statement about you starting a website as a manufacturer I mean, you just had a custom unit built and installed for the price of just the H&R swaybar (actually a little less) here in the US. Just think what Filippo would be doing....

Yeah at this point I guess I could do an entire Z4 suspension kit (custom adjustable dampers, custom adjustable sway bars, camber plates and even custom forged wheels) for less than what you guys pay for an oil change.

 

[NoQuarter]

I wsnt to do a front upper strut brace that works with my intake.

 

[F87Source]

Here's the bar factory.

https://rpaqcyp.m.tmall.com/

The guys who made the camber/caster plates are another company based in Tianjin. I don't think they have any website, or speak any English. Let me know what you need done.

Thanks! I am think about making some braces for the car, I have some Chinese friends I can utilize to help me write the email. Do they speak mandarin or Cantonese?

 

[F87Source]

for less than what you guys pay for an oil change.

This bites lol.

I also wanted to know how good is QC? I have purchased some stuff from alibaba before and it is really hit or miss. Sometimes it is really good, and sometimes you get the crappiest welds and the worst quality I have ever seen.

 

[Asbjorn]

This bites lol.

I also wanted to know how good is QC? I have purchased some stuff from alibaba before and it is really hit or miss. Sometimes it is really good, and sometimes you get the crappiest welds and the worst quality I have ever seen.

That workshop knows how to weld, so what you need to worry about is the design. If you have local friends, the GMs wechat is w13929498600 and he can speak mandarin. The only negative word I have on them is a roll cage they did where one of the bars where too close to the helmet of the driver. But in general I would recommend leaving a sample or car with them for any custom work they have to do. Forget about trying to make a fancy drawing.

 

[Lurcher]

Forget about trying to make a fancy drawing.

Can you get a quote for me on this?

 

[sancho78rus]

Are you running -3 camber front and -2 rear? Did you tried more?
What caster?
Do you use wheel spacers?

 

[fmorelli]

Can you get a quote for me on this?

Smart ass.

Filippo

 

[Asbjorn]

Are you running -3 camber front and -2 rear? Did you tried more?
What caster?
Do you use wheel spacers?

I lowered the front a little again last week, so perhaps I have a bit more than -3 up front now, but rear should be -2. I actually didn't check the alignment yet. I did add some caster, but again, no idea what angle it sits at right now. Will check later this month.

After installing the stiffer rear sway bar the car still tends a bit towards understeer when I run the Hankook square setup (Z214, 275/35R18). But interestingly, the car oversteers, even trail-braking into the corners, if I run my current street/rain tires on the same dry track (PS4, 225/40 front + 255/35 rear). I don't understand why this is happening. If anything, the rear PS4 tires are in a better condition than the front PS4 tires. Either the PS4 respond differently to the same suspension setup compared to the Z214 semi-slicks, or something else is at play.

Anyhow, to answer your question, I do recommend -3 or more camber up front on the track, as for the rear, Im a bit puzzled.

When I run the square 9.5J ET35 wheels, yes I do have a 3mm spacer up front to clear the damper. When I run the staggered 8.5J ET35, 9.5J ET40, I also run a spacer up front which is 12mm, but that is just for looks. With stock camber you don't need that 12mm spacer up front.

Square setup

Square setup

Square setup:

Staggered/street setup with 12mm spacer front

Staggered/street setup with 12mm spacer front

Here's my latest hot lap with the square Z214 hankook setup

I have found that under hard braking, especially at the end of the hot lap, the rear ABS works much harder than the front. The car is not quite stable. So I want to move the brake bias more towards the front. It is already more front biased than stock, but I guess with the semi-slicks, it needs even more front bias.

Here's the braking data from the first braking zone, ABS seems to be working both front and rear.

Here's the braking data from the last braking zone. It looks like both rear wheels loose brake pressure, whereas there's no ABS intervention up front. Also you can see how the front right looses brake pressure as I turn in (right hand turn) and weight shifts to the front left.

 

[sancho78rus]

I'm running without abs. So I can change braking balance from driver's seat depending on track condition.

I think you can run more aggressive camber. Did you measure the inner\outer temperatures of the tire?
Regarding antiroll bars it seams that H&R have adjustable one: https://media.carparts-cat.com/webdata1/imagedata/artbild/188061/1468/ANTIROLLBARS.JPG

 

[Asbjorn]

I'm running without abs. So I can change braking balance from driver's seat depending on track condition.
View attachment 42876

I think you can run more aggressive camber. Did you measure the inner\outer temperatures of the tire?
Regarding antiroll bars it seams that H&R have adjustable one: https://media.carparts-cat.com/webdata1/imagedata/artbild/188061/1468/ANTIROLLBARS.JPG

Yeah I modified my H&R front bar to make it adjustable as it only had one setting. The rear 21mm H&R bar was indeed adjustable, but I had a stiffer one (24mm) custom made that is also adjustable.

How did you realize the brake bias adjustment? Any DIY guide?

 

[F87Source]

Yeah I modified my H&R front bar to make it adjustable as it only had one setting. The rear 21mm H&R bar was indeed adjustable, but I had a stiffer one (24mm) custom made that is also adjustable.

How did you realize the brake bias adjustment? Any DIY guide?

You have to delete the entire factory braking setup except for the pedal and lines (pedal and brake lines) and replace everything with aftermarket parts. So instead of having one master cylinder you would have two, one for the front and one for the rear and there are valves to proportion fluid to the front and the rear based on pedal imput.

Here is a kit but it is not cheap nor do you want to cheap out on something like this: https://www.boefab.com/products/brake-bias-cage


Me personally I think ABS is one of the best inventions on the modern day car so I would never delete it. Plus I think the factory brake bias setup by bmw is pretty good so no real need or desire on my end to change it in any way.