Another update on the 535is.
Recently I have been working on the reliability of the 535is and still haven't figured out the cold start issue. It stalls after starting up when temperatures are below 50F. Touching the throttle makes it stall. But when warm it works great. Still working on that.
In the mean time, I did some research and found that the springs I bought would give me a similar bias as the Dinan setup. So I went about replacing the rears and using the height adjustable sleeves to get the height I wanted. This means I have standard Eibach Pro springs up front (~220#'s) with Bilsteins and the fixed camber plates. Then in the rear, I have 2.5" race springs (fixed rate instead of progressive) at 280#'s.
Front camber is about -2.2 degrees on both sides and I have almost 0 toe.
I wanted to dial out the understeer, so going to fixed rate and increasing the rear rate from what I had was to help me. Keeping the height at the rear also means that I have limited camber in the rear to hopefully limit the rear grip and promote front grip and the front turning in better. My rear shocks are Bilstein's that are supposedly Dinan valved. I have used them for basically 10 years and they help the rear of the e28 from feeling soft like typical Bilsteins. I liked that this spring rate should be pretty well matched to the shocks for Dinan rear 280# springs.
I also turned my front sway bar (25mm) to full soft for the same reasoning as it seemed like the E28 defaults to total understeer in tighter turns.
My rear bar (18mm) is set to soft as well, but I contemplated setting it to hard if I still want more rear end action.
Height is the same as this past summer, I measured and set the bilstein to second from the top circlip.
Here's my recent MAT/BARO settings.
Ignition advance. I backed off some advance for smoothness near low load/low rpm. That got rid of most of the jerkiness.
I run through a couple round-abouts on a regular basis where I can easily assess how the car handles. The spring change certainly helped the rear want to slide earlier, so the next step was the sway bar change. That again helped and make the car feel easier to change directions.
I just purchased a boost controller after thinking about the output of my megasquirt unit. I confirmed it was wired up with grounding signal on the IAC2 circuit. I did some research and decided upon a 4 port solenoid valve that I can run as 3 port or 4 port MAC 46A-AA1-JDBA-1BA.
The main advantage of the 4 port is that you can send boost to the top of the wastegate with no signal to the bottom to literally hold it shut. This allows high boost control up to 4x the wastegate spring but I decided to use it like a 3 port because I didn't want to have the touchy duty cycle where 1% duty could change boost by 2-3%. May play with those setting later since now I have the option.
The controller simply starts with an initial value table like idle valve and then sends a signal when active. The signal is a pulse that is a % of the window of time, so 100% duty is open fully for the full unit of time. 50% is half. Then, the frequency settings change how long/short the unit of time is. So in test mode you can audibly hear the change in speed of opening/closing when going from 19Hz to 15Hz-- it gets faster.
Here are some datalogs once I got it hooked up and was testing it's function. I found that 20-30% duty gave me about 5-10psi boost-- I was using my tunerstudio dash to view it.
This was my fist log of 155kpa after I knew the solenoid was working at 135kpa. It is easy to see that the 80% duty cycle was exceeded while boost was ramping up, trying as aggressive as possible to reach max boost.
Fuel mixture was a little rich and I was approaching 85% duty cycle (the limit) of my injectors. Timing was smooth after I applied a smoothing factor on my ignition table, which is visible in the log. Notice how boost jumps above to 169kpa and slowly levels back down to the target of 155kpa. This was too aggressive PID settings and I found some detail on tuning the PID:
1- Playing with the P term will influence the moment when the boost duty will start to increase when the boost is increasing. Big P number make the boost duty coming up sooner when the MAP is increasing and vice-versa.
2- Increasing P will reduce initial overshoot and vice-versa.
3- Increasing I will slightly increase initial overshoot. If the target isn't reached initially, a bigger I term will make the boost climbing to the target faster. Too much a I term will make the boost oscillating after the initial overshoot.
4- The D term will reduce the oscillating effect of a large I number. Too much D term lead to huge oscillations in the boost duty. It takes some large D number to reduce the initial overshoot.
5- I've varied the Control Interval from 30ms to 10ms without seeing any changes in boost control performance. Smaller Control Interval will lead to higher oscillation of the boost duty.
6- You can limit the maximal boost duty by setting the Open Duty at a number lower than 100%. It is useful if you do not reach the target initially because the boost is climbing faster. But this is not a good solution because it prevent the PID code to do his job if a smaller boost target is wanted later.
7- You want some sort of initial overshoot to have a good control. If the target isn't reached initially, the I term will try to get the boost to the target, but it will take some time.
8- Initial overshoot will be bigger in higher gear (4th, 5th) for a given PID setting compared to a 3rd gear run because the boost is climbing much more slowly and the P term is supposed to react to (current_error - last_error). When boost is climbing slowly, (current_error - last_error) isn't a big number so the P term do not have the same impact as in 3rd gear. The inverse is also true : you will get less overshoot when boost is climbing faster (like in 2nd gear).
I backed off the I and D settings and saw this result, boost too conservative in ramping up, but solenoid duty a nice level setting. Boost reached 10 and was slowly rising to 154kpa, but never eaching the target in 3+ seconds. Notice the gearshift and general good control of the fuel mixture. I simply need to dial back the fuel a little bit and be at 12:1 after, not 11.7:1
Here is a single pull merging onto the highway about 45-85mph. This section of the map was slightle too lean at 12.4:1
I am still dialing it in, but yesterday with boost reaching 8psi(145kpa) and slowly opening to the target of 10, I got this virtual dyno plot. My engine's blowby means I think I am losing some power, but overall I will retry this plot once I get boost settings dialed.
In the mean time, I just installed brake pads and did a fluid flush (ATE TYP 200)-- EBC redstuff street/track pads. They are ceramic and low dust which means they should be a nice fit for my dual duty (but street focused) use. Don't forget I have the E32/E34 upgraded brakes which allows use of E36 M3 pads.
Next up, aiming for a track day with the current setup. I am contemplating changing the radiator or running as is since temps should be below 60F.
I also have an oil catch can coming to try to collect any blowby instead of oiling my intercooler as it has been.
More updates and some photos/video to come!