OBD1 vs OBD2

[junglejuice]

I remember reading a writeup about the Grand having a different intake manifold with a larger volume. THat might explain the 600 rpm torque peak difference. I think the OBDI flexplate ad CPS sensor are the same - have to double check part numbers to be sure though.

The TCU will also be OBDI or OBDII for the diagnostic wiring and will likely throw a P0700 is mismatched. On the OBDI (and probably the OBDII) the TPS signal is Tee'd off the sensor input that goes to the PCM.

The manifolds for the Grands and the Xjs is the same in the 96, same part number.....

 

[hubs97xj]

Some older posts around here and various forums say the long blocks are the same, but the accessory brackets are different, as are some sensor locations and connections. Some also claim being told the motors can be swapped either way without major issues by the dealer.

I can provide zero firsthand experience; just something I read.

 

[junglejuice]

According to the parts manual the Xj and the Zj/g engines in the 96 model are the same part number, so from that all I can deduce is that it will bolt straight in using the Xj bracketry.
We will see on Monday as that is when I plan to swap them....

 

[junglejuice]

Well I found that the Zg engine uses the exact same mountings for all the brackets as the Xj does so I was able to use all the existing OBD1 sensors (incl the temp sensor in the rear of the head) as well as all the original accessories.
I have reset the ECU and am now waiting for it to settle but the signs are promising.....

Cheers, JJ

 

[cruiser54]

Glad to hear it. Keep us updated.

 

[junglejuice]

Well it has been in for a fortnight now and all is well, doesn't idle quite as smooth as the stock engine but it isn't too rough but the performance is better especially on hills which is a start.
I am thinking of still upgrading to the OBD2 system from a 96 Xj as I have everything for that and then I can use a scanner which will work as a trip computer as well.....

 

[junglejuice]

I remember reading a writeup about the Grand having a different intake manifold with a larger volume. THat might explain the 600 rpm torque peak difference. I think the OBDI flexplate ad CPS sensor are the same - have to double check part numbers to be sure though.

The TCU will also be OBDI or OBDII for the diagnostic wiring and will likely throw a P0700 is mismatched. On the OBDI (and probably the OBDII) the TPS signal is Tee'd off the sensor input that goes to the PCM.

No the manifolds are the same, the difference must be in the ECU's mapping as all the hardware is the same.....

 

[badron]

is there a difference in the mapping used in Grand Cherokees?
==============================================
The mapping will change to meet the needs, so it don't matter.
best to check but I THINK the OB2 will want to run your gauges.
No can do on your 95 and will pull a code because it can't.

 

[junglejuice]

is there a difference in the mapping used in Grand Cherokees?
==============================================
The mapping will change to meet the needs, so it don't matter.
best to check but I THINK the OB2 will want to run your gauges.
No can do on your 95 and will pull a code because it can't.

If you read back near the start you will notice that I have the ENTIRE system from an OBD2 Xj, every sensor, the entire loom, even the entire physical dash structure....

There has to be a difference in the programming to have different power and torque curves between a 96 OBD2 Xj and a 96 OBD2 Zg when all the hardware is the same otherwise the curves would be the same.....

 

[gradon]

The difference in rpms for peak torque is due to the different cams: 87-95s use one cam and 96+s use another. Taken from our buddy Dino's site in the Tech Specs, http://www.jeep4.0performance.4mg.com/ :

Stock Cam Specs
The stock '87-'95 Jeep 4.0 camshaft is a single pattern cam with the following specs:

Advertised duration int./exh.: 270.0/270.0 deg
Duration @ 0.050" lift int./exh.: 197.0/197.0 deg
Valve lift int./exh.: 0.424"/0.424"
Lobe separation angle: 112 deg
Intake centerline angle: 120 deg
Valve overlap (advertised): 46 deg
IVO: 21.5 deg ATDC (0.050" lift)
IVC: 38.5 deg ABDC
EVO: 22.5 deg BBDC
EVC: 5.5 deg BTDC

The stock '96 and later Jeep 4.0 camshaft is a dual pattern cam that produces more torque at lower rpm and a wider torque spread. The specs are as follows:

Advertised duration int./exh.: 256.0/260.0 deg
Duration @ 0.050" lift int./exh.: 188.0/192.0 deg
Valve lift int./exh.: 0.408"/0.414"
Lobe separation angle: 107 deg
Intake centerline angle: 114 deg
Valve overlap (advertised): 43 deg
IVO: 20 deg ATDC (0.050" lift)
IVC: 28 deg ABDC
EVO: 16 deg BBDC
EVC: 4 deg BTDC

Now certain 96 0630 heads have the coolant temp sender port and sensor@ driver's side rear for the dash gauge like the <96s(my 1/96 does), some have no sensor but a removable plug, and others no port at all. The 97+ get the temp from the cts in the t-stat. Some people drill the t-stat housing to put the gauge sensor in and extend the wire from the rear of the head. I have read that the cam in the 87-90 renix 4.0l was advanced some compared to the 91-95s(more low torque, less high rpm hp), but could just be hearsay. My 94 responded to mods better than my 96 with the same mods transfered. OBD1 could've been part of it, but I think the higher lift cam also played a part. 96+ engines have nvh(noise, vibration, harness) upgrades such as thicker internal ribbing and a nice girdle for the crank's main caps. The fuel systems are different between the two: 95s have tan 21#@39psi injectors w/ return and 96s have gray 23.2#@49psi injectors w/o return. Even though the internals between the 96xj and 96zj 4.0s are more than likely equal, the programming between the two would be different do to the different trannys and different loads(the zj weighs alot more).

 

[junglejuice]

The difference in rpms for peak torque is due to the different cams: 87-95s use one cam and 96+s use another. Taken from our buddy Dino's site in the Tech Specs,

I realise that the cams are different for the 95's and the 96's, I am guessing the difference between the 96 xj engine peak (3000rpm) and the 96 Zg peak (2400rpm) can only be down to the ecu's programming as the cams are the same.

http://www.jeep4.0performance.4mg.com/ :

Stock Cam Specs
The stock '87-'95 Jeep 4.0 camshaft is a single pattern cam with the following specs:

Advertised duration int./exh.: 270.0/270.0 deg
Duration @ 0.050" lift int./exh.: 197.0/197.0 deg
Valve lift int./exh.: 0.424"/0.424"
Lobe separation angle: 112 deg
Intake centerline angle: 120 deg
Valve overlap (advertised): 46 deg
IVO: 21.5 deg ATDC (0.050" lift)
IVC: 38.5 deg ABDC
EVO: 22.5 deg BBDC
EVC: 5.5 deg BTDC

The stock '96 and later Jeep 4.0 camshaft is a dual pattern cam that produces more torque at lower rpm and a wider torque spread. The specs are as follows:

Advertised duration int./exh.: 256.0/260.0 deg
Duration @ 0.050" lift int./exh.: 188.0/192.0 deg
Valve lift int./exh.: 0.408"/0.414"
Lobe separation angle: 107 deg
Intake centerline angle: 114 deg
Valve overlap (advertised): 43 deg
IVO: 20 deg ATDC (0.050" lift)
IVC: 28 deg ABDC
EVO: 16 deg BBDC
EVC: 4 deg BTDC

Now certain 96 0630 heads have the coolant temp sender port and sensor@ driver's side rear for the dash gauge like the <96s(my 1/96 does), some have no sensor but a removable plug, and others no port at all. The 97+ get the temp from the cts in the t-stat. Some people drill the t-stat housing to put the gauge sensor in and extend the wire from the rear of the head. I have read that the cam in the 87-90 renix 4.0l was advanced some compared to the 91-95s(more low torque, less high rpm hp), but could just be hearsay. My 94 responded to mods better than my 96 with the same mods transfered. OBD1 could've been part of it, but I think the higher lift cam also played a part. 96+ engines have nvh(noise, vibration, harness) upgrades such as thicker internal ribbing and a nice girdle for the crank's main caps. The fuel systems are different between the two: 95s have tan 21#@39psi injectors w/ return and 96s have gray 23.2#@49psi injectors w/o return. Even though the internals between the 96xj and 96zj 4.0s are more than likely equal, the programming between the two would be different do to the different trannys and different loads(the zj weighs alot more).

Luckily for me as I am currently using all the OBD1 components the Zg engine had a bung in the hole that my temperature sensor normally goes in so it just screwed straight in....
I don't know if there will be any benefit in performance/economy in swapping to the OBD2 system from the spare Xj?????

 

[cruiser54]

I wouldn't bother swapping anything. Lots of work for no real gain in performance. There are other things that could be done with your time and money to improve the performance, with alot less effort.

 

[junglejuice]

I wouldn't bother swapping anything. Lots of work for no real gain in performance. There are other things that could be done with your time and money to improve the performance, with alot less effort.

It won't really cost me anything as I already have it all.....

 

[cruiser54]

Then go for it...........

 

[gradon]

I'm with cruiser54, leave it obd1--people have swapped newer engines in older jeeps for years w/o problems. The only good thing about obd2 is that it helps point to the culprit/system that sets the cel via a port that is easy to scan, instead of counting flashes. Now many of the sensor connectors were changed in mid-96, so you might have to use your original sensors. I want to see specs that show the zj 4.0(not 5.2 v8)having its peak torque at 2400, cause that is a good 600-800rpms lower than the xjs and the cam would have to be seriously advanced to bring the peak down that far. That is mechanical not electrical, so the programming is not responsible for that.

 

[junglejuice]

I'm with cruiser54, leave it obd1--people have swapped newer engines in older jeeps for years w/o problems. The only good thing about obd2 is that it helps point to the culprit/system that sets the cel via a port that is easy to scan, instead of counting flashes. Now many of the sensor connectors were changed in mid-96, so you might have to use your original sensors. I want to see specs that show the zj 4.0(not 5.2 v8)having its peak torque at 2400, cause that is a good 600-800rpms lower than the xjs and the cam would have to be seriously advanced to bring the peak down that far. That is mechanical not electrical, so the programming is not responsible for that.

All the info that I have seen shows that the 96 Zg 4.0 litre has the torque peak at 2400rpm whereas the 96 Xj was at 3000rpm but the Zg had 5ftlb less, it was also 5hp less but at the same rpm and the cam is the same.

The 96 OBD2 Xj that I stripped used the same sensors as my OBD1 95 Xj except obviously it had an extra O2 sensor.....

 

[ehall]

transmission gearing maybe