INCREASING REV LIMIT
OK: here is what I have found...
In a Bosch 0 280 001 134 3.0 box, you can change the value of a resistor to increase rev limit. Decreasing resistance increases rev limit.
Resistor is #R704 located on the underside of the NON connector board.
1. Remove ECU
2. Remove two case bottom screws
2.5. Remove guts
3. Carefully remove two spring clips
4. Carefully remove THREE retaining screws. This is the board you want to work on.
5. open plastic wire cover(it just pops open)
6. GENTLY flip board over
In top left quadrant, you will see three elevated resistors. SEE PICS. The BIG FAT resistor is the NEW one. It is ~4700 ohms by color bands ( better to use at least 1/2 watt , and this is Gold quality..not that that matters too much..it's probably the best resistor on the board)
http://www.radioshack.com/product/index ... age=family
Anyway, OLD resistor is ~6200 ohms using color bands.
As a double check, NEW resistor is 4600ohms measured resistance (on board) ...
I checked both boards closely and this was the only change I could find. And , this makes sense as only one resistor should be needed to effect peak rev waveform....this allows "overvoltage or over-rev" to occur and does not shut off injectors. I have no other electrical mods to Bosch stuff and can rev to at least 7500rpm...
WARNIG: mod done on 3.0L ECU, although similar, I am not familiar w/2.5's. Also, overrevs can kill your engine..do this at your own risk!!
In a Bosch 0 280 001 134 3.0 box, you can change the value of a resistor to increase rev limit. Decreasing resistance increases rev limit.
Resistor is #R704 located on the underside of the NON connector board.
1. Remove ECU
2. Remove two case bottom screws
2.5. Remove guts
3. Carefully remove two spring clips
4. Carefully remove THREE retaining screws. This is the board you want to work on.
5. open plastic wire cover(it just pops open)
6. GENTLY flip board over
In top left quadrant, you will see three elevated resistors. SEE PICS. The BIG FAT resistor is the NEW one. It is ~4700 ohms by color bands ( better to use at least 1/2 watt , and this is Gold quality..not that that matters too much..it's probably the best resistor on the board)
http://www.radioshack.com/product/index ... age=family
Anyway, OLD resistor is ~6200 ohms using color bands.
As a double check, NEW resistor is 4600ohms measured resistance (on board) ...
I checked both boards closely and this was the only change I could find. And , this makes sense as only one resistor should be needed to effect peak rev waveform....this allows "overvoltage or over-rev" to occur and does not shut off injectors. I have no other electrical mods to Bosch stuff and can rev to at least 7500rpm...
WARNIG: mod done on 3.0L ECU, although similar, I am not familiar w/2.5's. Also, overrevs can kill your engine..do this at your own risk!!
- Attachments
-
- BIG FAT one is NEW resistor ~ 46-4700 ohms (Center of pic)
- NEW RESISTOR.JPG (39.09 KiB) Viewed 6790 times
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- OLD resitor
- OLD RESISTOR.JPG (42.84 KiB) Viewed 6788 times
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- Gold
- Posts: 166
- Joined: Tue Nov 30, 2004 2:55 pm
- Location: Keystone Hgts, Floureyeduh
x-rad,
Are these fotos of 2 different ECU boards? I see other components that are different, albeit similar.
I think my Verde 3.0ltr came with a ZAT modded ECU. I may open it up and see if they changed like you did. I'll try to post a foto of this as well.
Are these fotos of 2 different ECU boards? I see other components that are different, albeit similar.
I think my Verde 3.0ltr came with a ZAT modded ECU. I may open it up and see if they changed like you did. I'll try to post a foto of this as well.
Regards,
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi
TWO different 3.0 boards..one has slightly older components but they are the same thing in a different package..both run my car very well with O2 at stoich and everything else being the same except for rev limit
Yes . the board was modified when I got it. Done by a guy back East near Philadelphia whose name I have written down somewhere but can't find....he also modified the 2.5 wiring harness to work with 3.0. stuff
Yes . the board was modified when I got it. Done by a guy back East near Philadelphia whose name I have written down somewhere but can't find....he also modified the 2.5 wiring harness to work with 3.0. stuff
Last edited by x-rad on Mon Aug 13, 2007 3:37 pm, edited 4 times in total.
-
- Gold
- Posts: 166
- Joined: Tue Nov 30, 2004 2:55 pm
- Location: Keystone Hgts, Floureyeduh
Here's the best pics of my 3.0 ltr ECU & Spark Box. There is a piece of tape with markings of "modified version #1" in both. I guess this is a 'Pandora's Box' as they say. My ECU has the fat resistor.
- Attachments
-
- Alfa 3.0ltr Mod ECU 1.jpg (128.34 KiB) Viewed 6690 times
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- Alfa 3.0ltr Mod ECU 2.jpg (132.56 KiB) Viewed 6692 times
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- Alfa 3.0ltr Mod Spark Box 1.jpg (95.11 KiB) Viewed 6690 times
Regards,
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi
-
- Gold
- Posts: 166
- Joined: Tue Nov 30, 2004 2:55 pm
- Location: Keystone Hgts, Floureyeduh
xrad,
These are re-programmable. I cannot remember how they used to do this. This was back in the early 80's that I'm familiar with the L-Jets on BMWs.
I haven't checked anything on this one. This set up came with my Verde motor. I think it's the modified "pandora's box". I do not have the specifics other than the rev limit was raised. I'm not too concerned as I will go stand alone and elimenate this antiquated system and get my GTV6 into the 21st Century. I'm leaning towards Gotech right now.
These are re-programmable. I cannot remember how they used to do this. This was back in the early 80's that I'm familiar with the L-Jets on BMWs.
I haven't checked anything on this one. This set up came with my Verde motor. I think it's the modified "pandora's box". I do not have the specifics other than the rev limit was raised. I'm not too concerned as I will go stand alone and elimenate this antiquated system and get my GTV6 into the 21st Century. I'm leaning towards Gotech right now.
Regards,
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi
N. G. Brooks Robinson
'84 GTV6
'84 M635CSi