Recently Im feeling excited about a few upcoming mods:
1) Custom dampers
I currently run Koni FSD dampers in combination with stock springs front and Eibach pro-kit springs rear. Let me first list the advantages of this setup
- Comfortable. FSD basically means the dampers are soft over pumps (high frequencies) while harder than stock in turns (low frequencies)
- Balances the car away from understeer, due to the up-rated rear springs.
- Reduces squat as caused by the torque which is x1.5 over stock, again due to the up-rated rear springs
- Not too low, but much care is still needed when entering basement parking lots etc.
- Great reliability - no problems during the three years I have had them.
Disadvantages of current setup
- The front is really too low, both in and by itself, and compared to the rear. The main reason for this is that I run around negative 3 degrees of camber up front. Even with stock front springs, the ride height is impractical in China, and it also looks a bit silly. With stock camber, the is no problem, but I'm not going back to that. I love how the car feels with lots of camber, both on street and track, and eventually it will also allow me to run wider wheels.
- The dampers are not adjustable. And you can only adjust so much, even with modified adjustable sway bars. Sometimes I get a bit of under-steer on corner exit, which is a front rebound issue, and especially at high speeds, I get a lot of weight transfer on track. And in general I would like to be able to adjust the balance even further, as well as overall to accommodate anything from rain/street tires to full slicks.
So what were the options?
- New stock dampers. An often overlooked option. Dampers wear over time, and new OEM dampers should outperform used ones by a good margin. They probably wont be cheap, but the quality is there. This is something you would want to consider on cars that were designed from factory to do what you want to use the car for. My car did not come with adaptive suspension, and even if it did, it would be running comfort suspenion in DSC=off, which is not ideal.
- Bilstein B16 - way too low
- KW V3 - still on the low side, and probably also a bit on the comfortable side for use with slicks and high hp. Clubsport seems to be a better choice, but then that is an even lower coilover package, and not available for the Z4 off the shelf
- Ohlins - only really 3DMs kit would make sense, and I couldn't convince the dealers local to me to do any of that. I also have M4 friends who had ohlins and went to clubsport later. Also, as mentioned, I actually want to raise the front of my car.
- Koni yellows - probably great, but rear dampers are not adjustable with the Z4 kit. Also the lead-time was long.
- High-end custom coilovers. I don't know. Dampers are a wear item, and what they do at the end of the day is really simple. Paying exorbitant amounts of money for high-end 4-way dampers just because they are labelled "motorsport" seems super unreasonable to the engineer in me. Yes more adjustability is always great, but not at any cost.
- Normally-priced custom dampers. Alright then...
So I ordered locally produced custom dampers, according to the following requirements
- Adjustable in 10 steps both front and rear
- Front: 15mm longer damper base to raise front ride height. Shock travel matched to stock spring.
- Rear: Shock travel matched to Eibach lowering springs. Valved for harder base-dampening.
- Black color - because sleeper.
Can't wait to see the result in April.
2) Exhaust flap valves
After reading
this post on zpost, I realized the vacuum valve controlling the two exhaust valves on my car is probably broken. Currently I just run the valves open all the time, as the system hasn't been working for months. This is great on track, but not so great for highway cruising. For longer trips I even prefer to have the mid-cats installed to reduce the noise.
I ordered a $30 kit consisting of a new vacuum valve and a remote control box with remotes to open and close the valve. My idea then is to have the new valve work as stock, but with the option to have it open 100% of the time with the remote. Lets see if that logic can be wired up. I would not want the flaps closed at all times, because I run two exhaust flaps, and with both of them closed, there is way too much back pressure for any kind of boost as
seen in this log.
3) Separate water-methanol fluid tank for injection use
Currently I have two snow performance systems on my car. One is used for charge pipe injection (375cc) and one is used for spraying in front of the radiator and DCT cooler. They both take water from the wind screen washer fluid tank, which has been expanded with an additional tank for extra capacity. Problem is, I cannot add methanol to this tank, because the fluid is still used for wind screen washing. Another problem is that the fluid gets warm being inside the engine compartment, right next to the GC lites cast manifolds.
The situation now is that I do not use the outside water spray on the street. On track I have access to plenty of ice cubes, so that is not a concern, and I still use it there occasionally. I also do not use the water injection on street, because I don't really push the car much in day-to-day use, and my car is tuned for pump gas anyway. I feel like it doesn't make sense to inject hot water either, as there is no octane in water, and if it doesnt cool iat and egts, whats the use?
So a bit wrong how I installed these then...
After some thought, I have decided to add a new fluid tank in the trunk. This fluid tank will then be used for permanent water-meth injection, and only that. Since the fluid wont get nearly as hot, it even makes sense to just use pure water when access to methanol is limited.
The enlarged water tank in the engine compartment can then continue to serve its dual purpose using pure water.
Alright, that was way too much text that no-one will ever read. My next post should contain pictures with the actual results. Im still planning to change the rod-bearings and enlarge the oil sump somehow, but fortunately my oil filter was 100% clean when we checked it again recently.
