How difficult is this conversion and is it worth the money to flash an obd1 ecu or just getting a piggy back for my obd2. I have a Prelude 98' sh obd2 and I want to convert it to mess with ignition timing and cam timing.

Any help would be appreciated

 

It's worth it. There's plenty of features available for the OBD1 ECU that are very useful in getting the best power and drivability. Using some piggy back more than likely won't allow for the same.

 

to convert from OBD2 to OBD1 is it as simple as taking the old ecu and replacing it with the obd1 or do I need a wiring harness and other add ons to change? I would change to a 4th gen lude ecu.

 

It depends on what you want to do with the car.

If you are looking to have a "tunable" ecu. Then an OBD1 Civic or Integra ECU is what you would want to get.

If you have the stock intake manifold with the IABs you will need an ecu to control them. The P72 (Integra GSR) has this feature stock so that would be an option.

You could also run a chipped P28 ecu which is modded to control the IABs, this is by far the cheapest route and honestly the most cost effective.

Other than the ecu all you would need is a OBD2 to OBD1 conversion harness. Then you just unplug your stock ecu and plug in the conversion harness and new ecu.

 

How would the P28 ECU work with the Prelude SH ATTS system is there a way I can replace that with a basic LSD diff or am I stuck with it?

 

It won't work with the ATTS, from what I understand.

 

You loose the ATTS function which can only handle about 225-250ft/lbs of torque anyway.

 

With the function gone how will my Diff work. will it act as an open diff and not tranfer torque correctly if one tire is under more load than the other. My ATTS unit is already acting up. There is nothing available for the fifth gen lude to get rid of the ATTS?