I’m getting really bad about documenting what i’m doing and even updating the blog. But here’s a brief recap of what went on over the winter:
- Oiling System
- Power Steering System
- New reservoir and hoses. Used a custom hose for the reservoir to cooling trumpet to eliminate the weak factory crimp connection
- New shocks/struts/springs
- TCKline DA shocks/struts with 450/500# springs
- I got these used for a pretty good deal and had them rebuilt
- Front subframe reinforcements installed
- Cooling System
- New thermostat and housing
- New S54 Z3M radiator
- Spal electric fan
- Custom ducting
- New belt tensioner (converted to hydraulic) and belt
- Deleted all A/C components, washer, other misc bits
- Thinned wiring harness to remove unneeded wiring
Here is a summary of the connections I made to the factory E36 sensors.
The RPM signal is a clean 12V pulse train who’s frequency is proportional to the engine speed. If you setup a rising edge interrupt and a timer, it is easy to measure the signal’s period. Be sure to scale the 12V appropriately for your devices I/O levels. It gives one pulse per cylinder fire and there are three pulses per rotation so the equation boils down to:
So RPM = MeasuredPeriod(micros) / 20000000(micros)
The RPM signal can be found at three fairly convenient locations that I know of. The wire is always solid black:
- Pin 1 on the round diagnostic connector under the hood on the passenger side
- Pin 20 on connector X16 to the back of the gauge cluster
- Pin 8 on connector X22 to the cruise control module behind the glove box
The Speed signal is also a clean 12V pulse train who’s frequency is proportional to the vehicle’s speed. Be sure to scale the 12V appropriately for your devices I/O levels. The sensor is in the rear differential and outputs 9 pulses per revolution.
Speed = 6313.13 * TireCircumference / MeasuredPeriod(micros)
The Speed signal is black with a white stripe and can be found on:
- Pin 2? on connector X16 to the back of the gauge cluster
- Pin 10 on connector X22 on the cruise control module behind the glove box
- Pin 10 on radio connector
The TPS signal comes form a potentiometer mounted on the throttle body. It’s middle pin/wire outputs 0-5V proportional to the throttle position. Note that there is about a half a volt of deadband on both ends resulting in an effective range of about 0.5V to 4.5V. I ran this into an ADC and scaled to provide a percentage.
It’s not super pretty, but it works!
Over the past few months I installed the following sensors:
- Water Temp (AEM 30-2012) installed where the throttle body heater coolant bung used to be in the head. It threads right in with an adapter i got from TRM.
- Oil Temp (AEM 30-2012) installed into Bimmerworld oil distribution block mounted to oil filter housing
- Oil Pressure (AEM 30-2131) also installed into the Bimmerworld ODB.
- Throttle Position I get by tapping into the factory sensor at the throttle body. It is a 0-5V signal.
I loomed up the wiring and ran it through the firewall behind the glove box nice and neat. Everything still looks neat and clean in the engine bay. Once through the firewall, I crimped Molex MicroFit contacts on the wires and inserted them into the connector which mates to the “Main Unit”.
The Main Unit is installed in the glove box. For the moment its just the raw PCBs mounted on stand offs screwed to the bottom of the glove box. I need to work on an enclosure for this, but for now at least its secure and neat. (I’ll add a pic of this soon).
I then made another harness with the MiniFit connector and ran it behind the dashboard to connect between the Display and the Main Unit. the Display is secured via its bottom stand-offs with velcro. Again, not pretty, but its secure enough for the time being.
Functionally, everything is working great. I’m happy with the legibility of the display. The shift light is awesome. All sensors are behaving. It’s logging data well. It’s really pretty cool!
My intention is that over the next few weeks, I’ll write posts detailing each subsystem of the device including the sensor, circuit, and software, etc. Here’s the first one:
Digital Dashboard Dissection: Temperature Sensors
Last fall I was prepping for the install of a bolt-in 4-point roll bar when i noticed a crack under my back seats…
That couldn’t be good so I had an excellent local race shop, Vintage Sports & Restoration, take a look. And they found a cracked subframe.
This is a fairly uncommon failure on an E36. Typically it is the stubframe *mounts*, which are a part of the unibody of the car, that crack. My mounts were fine, but it was this ear of the subframe itself that cracked.
The shop also noticed that the previous owner had installed solid aluminum differential mounts, but kept the original rubber subframe mounts in place. With no isolation between the diff and the subframe, all that driveline energy was being applied to the rubber bushings. They quickly died and eventually fatigued the subframe and it cracked. At the point, the driveline energy was being coupled to the unibody asymmetrically through three instead of the four mounting points and that probably caused the stress crack under the seats. So the moral of the story is to understand how bushings/mounts work and make sure they’re being used as a system.
So VSR installed a new freshly painted subframe with 75D mounts. Being the foundation of the rear suspension, we wanted a firm interface here. We opted against going full aluminum because we do want to reduce some of the high frequency energy that can be rough on a street driven car both in sound and metal fatigue.
We then used 95A poly diff mounts so that there is some give to the driveline, but it it still much stiffer than stock to sharpen the response a bit.
If that wasn’t enough, the shop said my diff was making a lot of noise and the left side output shaft bearing was shot. That snow balled into a brand new 3.46 2-clutch, 40%, 45/45 LSD from Dan at diffsonline.com. Dan’s work is top notch and his diffs are very common among the club racers. I rebuilt the LSD in my old E30, but I decided to let the pros handle this one. Since the car is still driven to and from tracks as far a way as 6-9 hrs, I chose the 3.46. The more racey 3.64 is perfect for a trailered race car but it revs too high for comfortable highway driving.
So as of yesterday the car is home again. Here’s a final rundown of what’s new:
- 4-pt bolt-in roll bar with custom harness bar height (I’m tall)
- Repaired crack under rear seats
- Refurbished subframe w/ AKG 75D bushings
- Rebuilt 3.46 LSD from diffsonline.com. 95A bushings
Next up is:
- Install seats (Cobra Suzukas w/ VAC hardware)
- Install harnesses (Schroth ProFi 6-pts)
- Install new valve cover gasket (I have quite a leak now) and spark plugs
- Install oil temp, water temp, oil pressure sensors (for digital dashboard)
- Break in new diff!
For awhile I’ve thought that it’d be cool to make my own digital dash and data logger for my track cars. You can certainly buy these, but they aren’t cheap. I think i can build one for way less, learn a thing or two, and have fun doing it.
So far i have a breadboarded prototype up and running. It’s based on the EA LPC4088 on the mbed.org platform. I’m using a mini dev board for break out and a standard breadboard to host my peripherals.
For now I’m using a basic 20×4 LCD for display. This processor can power a TFT so eventually i may move to that. When in use, i plan to focus more on the shift lights (shown on the right of the breadboard) and warning lights for real time feedback.
Basic Block Diagram
As of now it has:
- LPC4088 quickstart board with EA Basic Dev Board
- LCD with i2c backpack
- Shiftlight strips (from adafruit) on i2c backpack
- AD7490 ADC on SPI bus
- AEM pressure and temp sensors feeding into ADC
- SD memory card reader on Dev Board
It’s currently capable of receiving sensor inputs via 5V ADC and pulse train (engine and vehicle speed). It crunches the sensor data and displays it on screen. The shift light also functions appropriates and flashes red when max RPM is exceeded. It samples and also writes the data out to the SD memory card at 10hz.
The next step really is to solidify the hardware. I’m working on a schematic that I’ll layout and make into a PCB. It’s mostly done, but i’m hung up on how i want to divide up the components. Should I have a brain in the glove box and a remote display? Should the shift light be separate from the display? etc. I also have an accelerometer that I need to integrate. Eventually I’ll also want GPS so I should probably make provisions for that before I get too far along. Then again, these things tend to actually develop when you move on what you have now and iterate later. Holding for future updates leads to nothing getting done.
Click on the “Digital Dashboard” category to the right for all the latest posts.
I’m doing a lousy job of keeping this updated, but here’s an update on the M3.
So far I’ve done:
- Installed Cobra Suzuka racing seats for head room and control
- VAC Motorsport adapters, mounts, and hardware
- Removed headliner and sunroof, installed fiberglass delete panel for headroom and future rollbar height
- Replaced the H&R Race springs with Sport, better ride height and geometry
- Front wheel bearings
- Front control arms and Bimmerworld TrackCAB delrin bushings
- Bimmerworld Group N rep motor mounts
- Rogue Engineering transmission mounts
- Secondary Air Pump delete
Right now the car is solid and I’m just having fun driving it. So far I’ve done four track days and two autocrosses with it and its been a blast. I have the last track day at NHMS coming up this weekend.
The next item on the list is to install a 4pt roll bar and get the harnesses I have sitting on a shelf installed. I hope to document this project a little more thoroughly!
Well a lot has happened in the six months since i last posted anything about cars. Last fall I sold the GTI. It was a good car and consistently exceeded my expectations both on and off track. Despite VW’s somewhat tarnished reputation for reliability, it never so much as hiccup’ed, even running an extra 100ftlbs of torque and 75 additional horsepower on track.
However the track bug was coming back with a vengeance and I knew i should get something older, cheaper, with more track/race support going forward. I decided on an E36 M3. Since I’ve owned one before, I know them well. They have tremendous aftermarket race tech/support and a great community. I was even running BMWCCA track events in the GTI!
Previously, i had a sedan, but this time i wanted a coupe. There isn’t a performance difference, but the larger coupe doors make getting in and out easier with race seats easier for a tall guy like me. Alpine White is the only color a BMW should be in my opinion and a black interior would be ideal.
It took me over six months to find the right car, but I finally did. And lucky enough, it was a local car and BMWCCA-Boston club member.
1997 BMW M3
It’s a southern car brought up here by the previous owner as a weekend/track car. It’s lived a comfy life and is really clean. It came with a great maintenance/mod history. The previous owner definitely loved this car.
In my next post, I’ll go over where the car stands, what I’ve done recently, and what my goals for the car are.
The stock GTI spindles are cast iron which means heavy, rusty, and even prone to cracking under heavy track use. Fortunately, there are a couple of OEM forged aluminum options that remedy all of the above. The Audi S3/VW Passat spindle is geometrically identical to the GTI spindle except for having a slightly shorter steering arm. The Audi TT spindle offers a lower lower ball joint mounting point to improve roll center which is great, but it it also has a much longer steering arm. The length of the steering arm directly effects how far the wheel is angled per amount of tie rod travel. The longer the arm, the less wheel angle you get for a given amount of tie rod travel.
The stock VW GTI arm has a 10cm steering arm. The forged aluminum Audi S3/VW Passat spindle has a shorter 9.6cm steering arm. Finally, the Audi TT has a much longer arm at 13.3cm. The plot below compares the resulting ratios.
As you can see, the GTI and S3/Passat spindles are similar with the S3/Passat being a bit quicker. It also shows how much slower the TT spindle makes the steering ratio. The TT suspension was designed as a total system. This shows mismatching components in a system can have cons you need to be aware of.
So like I said in the intro, I bought a new Volkswagen GTI in 2010. It’s the perfect car for my needs. First of all, its a nice, comfortable car. I’m 6’4 and the GTI is the ONLY car (on my interest radar) with factory seats that I’ve sat in that i can clear a helmet in. I can drive it on long road trips without feeling cramped. It has a solid on-center feel that makes long drives on the highway effortless. It has a solid stereo with good features, good utility and cargo space, and good gas mileage. So it fits the daily driver bill.
And most importantly, its fun to drive. Stock, it has decent power and a solid suspension. I did two autoxes on bone stock suspension and was surprised with the results. The car rotated very well and body roll was reasonably controlled. It was fun to drive. So it fits the ‘fun to drive’ bill as well.
Since this is the background post of a project that’s now three years old, I’ll go ahead and get to the good stuff. Here are the mods to date:
- APR Stage II flash. More boost, more power! I’m making around 275hp and 310ftlbs at the crank.
- Ultimate Racing 3″ downpipewith ceramic cat and no resonator. Quicker spool, more top end power.
- Audi S3 Intercooler. Cooler and more consistent intake air temps.
- Carbonio Intake. Some noise and who knows what else.
- VW Tiguan pipe. Deletes the factory noise pipe which funnels sound into the cockpit. Quicker spool.
- Neuspeed Turbo-Outlet-Pipe. Replaces the restrictive factory pipe and provies a more secure clamp interface.
- Bilstein B8 Sport shocks/struts. (MK6 model #s)
- VW Drivers Gear springs. Linear rate, a little stiffer than stock.
- Hotchkis 27mm hollow sway bars front and rear.
- 034 Motorsport strut mounts. Much stiffer rubber keeps the strut planted.
- Audi S3 spindles. Forged aluminum, stronger, lighter, and shorter steering arms quicken steering.
- Whiteline Anti-Lift Kit. Adds castor, reduces front end lift, and stiffens the rear LCA mount.
- Autotech transmission mount insert
- Stoptech 328mm ST40 brake kit
- Stoptech Street Performance pads for daily and autox
- Hawk DTC-60 pads for track
- VW Goal wheels (17×7.5″) with Dunlop D1 Star Specs for summer, autox, and track
- Stock Detroit wheels (18×7.5″) with stock all seasons for winter/off season
- Audi S3 smooth underbody tray
- Audi S3 rear trailing arm underbody covers
Wow, that list really got long after a few years. The boring part is that I think the car is just about done. The springs, shocks, mounts, and spindles is my most recent mod and they really completed the package. The car rides great in daily use and really feels good on track.
Here’s a few of my track and autox videos.
I’m gearing up for an autocross and a track day in the same week, so I figure its a great time to talk car stuff. I started wrenching on cars with my Dad as a kid and have been into it ever since. I caught the motorsport bug with my first autocross when I was in college and that really fueled the fire.
When I think about it, I’m not into fancy cars or super cars. I’m not into old cars or show cars. What I’m into is figuring how the cars i have work and how to make them better. The test bed for these improvements is then autocross, track days, time trials, and hopefully someday club racing.
In the past I’ve had a few projects, an ’04 VW R32, ’97 BMW M3, ’98 BMW 540i/6…
2004 VW R32
1997 BMW M3
Probably my favorite was the 1987 BMW 325is that i built to SpecE30 specs as a dedicated track car. Simple and easy to work on, great community, and a blast to drive. Oddly, I can’t find any good pics of this car… guess I was too busy driving.
1987 BMW 325is
Things changed a little a few years ago when I moved to Boston in 2009. I live in the city and have to be pretty grateful for even the driveway i have. No garage, no space for projects. 🙁
I needed a car that could wear a lot of hats. My commute is up to 2 hours a day and I take lots of road trips so I wanted something comfy, nice, good stereo, etc. Since I didn’t have easy access to a garage or tools it needed to be pretty reliable, preferably with a warranty. AND it had to be fairly sporty, fun to drive, and capable of the occasional autocross and track. I decided to buy a new 2010 Volkswagen GTI and its been making me very happy ever since.
On to the Project GTI!