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scarceller scarceller is offline
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Join Date: Oct 2006
Location: Southern MA
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I spent 6 years plus reverse engineering the 84-89 Bosch Motronic program and I now have a full understanding of the entire program code and I can say that 1000s of hours went into designing the code by Bosch. I'm amazed at all the items they thought about that many aftermarket EFIs can't do or don't do well or the tuners don't address.

For example:
- 40% of the code is idle control!
- Extensive compensation for ignition based on IAT, you can't tune in the Winter and assume it will be just fine in the Summer. Most common mistake by inexperienced tuners!
- Extensive thought to the design of cold start, the Motronic system adds boat loads of ignition for cold start below 40F. This area alone can be very hard to tune and get correct.
- The list goes on

Not to mention you need a Load dyno to tune part throttle correctly if you don't already have the stock part throttle ign maps you can spend 4 hours or more dyno time just tuning this area! And you better have a tuner that knows the importance of tuning this correctly as throttle response depends on it. This is the one area of improvement over CIS that the EFI gives you, electronic ignition control over all load conditions for the motor. An old school distributor is fine for WOT ignition and a compromise for Part Throttle ignition via the vacuum advance.

Installing the EFI and the cost for the system is only the first step. As someone already pointed out earlier in this thread you can spend a few $1000 installing the system and then go through $10,000 trying to tune it with pro tuners and still not get it correct.

Not saying aftermarket EFI is bad, it certainly is not but you need to know what to expect and it certainly is not cheap to do the entire job CORRECTLY.

I'm very glad I decided to stick with the factory Motronic system and invested the time in learning howto tune what I have. The factory did all the hard work and I did not have to redo this and I learned tons by looking at the factory example first. Since I have first hand knowledge of what went into the factory tune I can now apply what I learned to any aftermarket EFI but I've found that some of these EFI systems can't accommodate some of the factory techniques.
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1984 911 Carrera Cab M491 (Factory Wide Body)
1975 911S Targa (SOLD)
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Last edited by scarceller; 11-18-2014 at 07:33 AM..
Old 11-18-2014, 07:04 AM
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