4.0 vs 4.0 HO
02-09-2011, 12:42 PM
#1
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Year: 92
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Engine: 4.0 H.O
4.0 vs 4.0 HO
What is the difference between the standard 4.0 and the 4.0 HO? probably going to buy one and rebuild it, but looking to see which one i should be looking for. and what the big difference is.
02-09-2011, 12:58 PM
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Year: 1998
Model: Cherokee
Engine: 4.0L
High Output is a version of the I6 post 1991 with a newer cam, larger throttle body, and improve intake and exhaust manifolds. The torque and horsepower rating were increased.
HO TQ:230
HO HP:190
vs
TQ:224
HP:177
HO TQ:230
HO HP:190
vs
TQ:224
HP:177
02-10-2011, 03:41 AM
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Year: 1997
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Engine: Straight 6 4.0L
what are the years of OBDI and OBDII and what do they mean, are they the type of engine?...what are the engines between 90-91 if 84-89 are renixs?
02-10-2011, 04:54 PM
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Year: 1987
Engine: Check
Some vehicles moved to OBD-I sooner than others, most OBD-I vehicles were not standardized, meaning they will all be slightly different.
90-91 motors should be OBD-I motors.
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02-10-2011, 07:24 PM
#8
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Year: 1989
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Engine: Renix 4.0L
OBD-I and OBD-II are just vehicle operation/diagnostic systems. If you have a vehicle thats 95/96 or newer, its ODB-II.
Some vehicles moved to OBD-I sooner than others, most OBD-I vehicles were not standardized, meaning they will all be slightly different.
90-91 motors should be OBD-I motors.
Some vehicles moved to OBD-I sooner than others, most OBD-I vehicles were not standardized, meaning they will all be slightly different.
90-91 motors should be OBD-I motors.
02-10-2011, 09:01 PM
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Year: 1988
Model: Cherokee
Engine: AMC242
Renix (1984-1990 w/AMC engine, particularly the 1987-1990 6-242 MPFI engine) is considered "pre-OBD" - meaning it's exempt from OBD requirements, and does not "store" or "throw" DTCs (Diagnostic Trouble Codes.) Most troubleshooting on the RENIX system can be done with a decent DMM, there are only a couple of tests that require an analogue meter. There are data readers that can "speak RENIX" - the Snap-On MT2500 comes to mind.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
02-10-2011, 11:10 PM
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Year: 1989
Model: Cherokee
Engine: Renix 4.0L
Originally Posted by 5-90
Renix (1984-1990 w/AMC engine, particularly the 1987-1990 6-242 MPFI engine) is considered "pre-OBD" - meaning it's exempt from OBD requirements, and does not "store" or "throw" DTCs (Diagnostic Trouble Codes.) Most troubleshooting on the RENIX system can be done with a decent DMM, there are only a couple of tests that require an analogue meter. There are data readers that can "speak RENIX" - the Snap-On MT2500 comes to mind.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
02-10-2011, 11:44 PM
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Originally Posted by 5-90
Renix (1984-1990 w/AMC engine, particularly the 1987-1990 6-242 MPFI engine) is considered "pre-OBD" - meaning it's exempt from OBD requirements, and does not "store" or "throw" DTCs (Diagnostic Trouble Codes.) Most troubleshooting on the RENIX system can be done with a decent DMM, there are only a couple of tests that require an analogue meter. There are data readers that can "speak RENIX" - the Snap-On MT2500 comes to mind.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
However, note where you see the "OBD Exempt" notation on the VECI - because most smog 'techs' aren't aware of the fact, and will try to downcheck you for "CEL/MIL not working" (there is a window for it - it's leftover from the GM V6-173. It was purchased with its OBD-I compliant control system.) You are still subject to periodic emissions inspections.
1991-1995 was the OBD-I/HO years, the control electronics were made by Chrysler (instead of Bendix to AMC/Renault specifications,) and some changes were made to the cylinder head to improve breathing. From what I've been able to determine, the changes to the camshaft ran from "slight" to "nonexistant," and the installation timing was changed slightly to encourage exhaust gas reversion at the port (which allowed for the elimination of that asinine EGR valve for the 1991 model year.) The intake ports were also "raised" (WRT head deckline) slightly, which allowed for better airflow through the intake port. The valve sizes, locations, and such did not change. (NB: All heads from the 1975-up AMC 232/242/258ci I6 engines will swap, but you may have to watch out for the screw sizes. Earlier heads used 7/16"-14 head screws, and later heads used 1/2"-13 thread. Similarly, all critical crank dimensions - except stroke - and critical camshaft bearing dimensions are the same, and these parts will swap freely.)
1996-2006 was the OBD-II years, with an overlapped break around 1999/2000 for the conversion to COP/DIS ignition. The earlier 0331 heads (for COP/DIS) are the ones you often hear of cracking on top, between the #3 and #4 cylinders, and that head should be avoided from 1999 through about 2001. The "good" 0331 heads have "TUPY" cast into the top surface - it's a Brazilian foundry mark, and indicates a revised casting that will hold up. The later 0331 heads (through 2006) will drop on as a direct replacement for the earlier 0331 heads.
OBD-I is characterised by the presence of a working CEL/MIL, and a Chrysler-specific diagnostic plug (there wasn't any real standardisation between manufacturers for OBD-I, as it was mandated by CARB.)
OBD-II similarly has the functional CEL/MIL, but also has a standardised diagnostic interface plug (since OBD-II specs were taken over by SAE, which means that all vendors use a common interface and code set. Each vendor does have a vendor-specific supernumary code set, but the "basic" diagnostic codes are the same across platforms.)
The primary reason for the performance differences between RENIX and HO power levels are:
- Improved cylinder head airflow, particularly in the intake ports
- Improved fuel delivery and ignition timing curves
- Improved camshaft dynamics (in later years)
- Improved intake manifold airflow (particularly in the 1999-up "Ram's Horn" intake)
- Improved exhaust manifold and system airflow.
As you can see, it's not any one specific factor that accounts for the increase in power output - it's a combination of small things that heterodyne each other to make for a much greater effect.
Wow. You sir are a vast depth of knowledge on our dear Cherokees. Hats off to you!
02-11-2011, 11:26 AM
#12
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Okay so now i have a question. I have my 89 renix. and i've noticed that on the tag on the hood it says OBD exept. So i know this is without on board diagnostics, but does this also make me exept from emissions laws? might be a dumb question, but i was just wondering..
So, with that said, no, you are not emission exempt. You must still follow federal and state regulations for the year of your truck.
02-11-2011, 01:03 PM
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Originally Posted by Gee oh Dee
I dunno if your question was answered, the previous post was way too long for me to read at the moment.
So, with that said, no, you are not emission exempt. You must still follow federal and state regulations for the year of your truck.
02-11-2011, 01:04 PM
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Originally Posted by Gee oh Dee
I dunno if your question was answered, the previous post was way too long for me to read at the moment.
So, with that said, no, you are not emission exempt. You must still follow federal and state regulations for the year of your truck.
