For all you turbo alfisti (and not only) out there which like me (not anymore though
) have to stay in the car idling to cool down their turbos after a track day or just driving hard, I present the intelligent turbo timer which takes the guesswork out of the problem.
Before we begin let's set the things straight: what you are about to read and hopefully make is the result of me getting shafted by Jaycar Australia. Long story short I purchased from them an intelligent turbo timer kit (http://www.jaycar.com.au/productView...Max=&SUBCATID=
). I received it just to find out that it was dumb as a brick since the PIC microcontroller was misprogrammed or not programmed at all although it had the copy protection bits set so I can't be sure which one. After e-mails to Jaycar support (informing them of the problem and requesting to either send me the hex code so I can program my chip or at least if they were worried about copyright issues just send me another preprogrammed chip) which all went unanswered which denotes a totally lack of respect for their clients (which made me swear I'll never buy from them anything again and also advise everyone against buying from them) I bit the bullet and using my microcontroller programming knowledge (little as it is) I recreated the software from scratch according to the specifications and using instead a 16F628A, which is better than the 16F84 they used and also pin for pin compatible so no issues here. This means that I can publish my own work for free and since the schematic is nothing more than a few extra parts (none of them intelligent) there's no copyright on it and even if it was it's only fair that I publish it due to the forementioned circumstances. I'm sure Jaycar won't mind, though I won't loose any sleep if they do. Jerks!
This module uses input from an airflow, oxygen, MAP sensor, throttle position sensor (or any voltage that varies with engine load within a 0-12V range can be used) to determine how hard the car has been driven. It then uses this information to calculate how long the car needs to idle, reducing unnecessary idle time. The sensitivity and maximum idle time are both adjustable, so you can be sure your turbo will cool properly.
It also has a reset button so that you can kill it off in the unlikely event that you consider it has calculated too long a time and you get bored
and in emergency situations when you need to shut down your engine.
How it works
It constantly monitors the engine load by attaching the sensor wire to a signal source (see description).
As a side note I used the turbo pressure sensor which I only thought adequate as a direct source of the turbo status information - for alfa 166 I can help you with location and procedure, for other cars you'll have to figure it out by yourselves.
A multi-turn trimpot (VR1) adjusts the sensitivity level. To set it you need to watch LED2 while the car is being driven; VR1 is then adjusted so that LED2 lights only when the car is being driven hard (normally this would be when the car is on boost). The engine load at which LED2 lights is called the "threshold". The software monitors how long the engine load exceeds this threshold over a 7 minute period. This information is constantly updated so that when the engine is switched off the software has a record of how hard the car was being driven for the last 7 minutes. The idle timing period will be at its maximum if the engine sensor voltage was over the threshold at least 25% of the 7 minutes. If the over-threshold period is less than 25% of the 7 minutes the idle period will be reduced accordingly. However the actual idle-down period reflects not only what proportion of time over the last 7 minutes the threshold was exceeded, but also when in that 7 minutes the hard driving occured. If the threshold was exceeded just before switch-off the idle period will be longer than if the over-threshold occured earlier i.e. 5 or 6 minutes before switch-off. Specifically the bias is such that if an over-threshold occured in the last 1.75 minutes of the 7 minute period the idle time will be the max idle time as for the over-threshold occuring in the first 5.25 minutes the idle time will be calculated percentually corresponding to each 1.75 minutes slice (which is better than what they did which was basically for the last 1.75 minutes double the idle time of the 5.25 minutes period).
Only four wiring connections are needed to get the timer up and running. These are chassis ground, engine load sensor input, battery side of the ignition switch and ignition side of the ignition switch.
For the engine load sensor input you need to find a wire that has a voltage that rises with engine load. If you have a voltage falling with increasing load no problem, just install the jumper LK1. Normally just blipping the throttle is sufficient to vary the engine load enough to make identifying this wire easy. This wire doesn't need to be cut just T into it.
The system works with an alarm and you should have no trouble, however if you run into problems there is a connection for an optional external relay which you can use to bypass the alarm's engine immobiliser for the time the turbo timer is running. Finally if the alarm requires an ignition signal use the "alarm ignition input" connection on the timer.
The first step is to set the switch S1 to the max idle-down time that you think will ever be needed (I have mine set at 5 minutes, but you can set it to maximum 15 minutes if your heart so desires).
S1 position - max idle period
0 - 15s
1 - 30s
2 - 1m
3 - 1.5m
4 - 2m
5 - 2.5m
6 - 3m
7 - 3.5m
8 - 4m
9 - 5m
A - 6m
B - 7m
C - 9m
D - 11m
E - 13m
F - 15m
The next step is to drive the car while an assistant (usually girlfriend, wife
) monitors the status of LED2. Trimpot VR1 should be adjusted until the LED2 lights only when the car is being driven hard.
I have this system running on my car for over 6 months now and has never failed me (which speaks lots of the quality of my code, anybody hiring ?
). I never have to stay with my eyes on the ICS clock anymore to see when I can shut down the engine which is a great relief, trust me, of course for turbo conscious people like me
not to mention that if my wife borrows the car (although she's never gonna drive it hard
) I can rest assured that if the turbo needs to cool down it will and that in itself is another big relief.
archive containing diagram, code and instructions
If you have questions about the system feel free to ask and I'll try my best to help, but you'll have to take into account that I have a pretty limited time for this, so only serious and to the point questions, please. As I said before you have to figure out some things by yourself about how to install it in a vehicle and I can't help you there. After all it's not a commercial product and any questions like "how do I install this in an Audi?" will be ignored, no offense.