PDA

View Full Version : new one to chew on



jjunk
07-01-2005, 02:13 PM
It seems that hear in colorado we have a debate going on and no one is for certain on who is write.

The story is this . If I have a 93 grand that came with a 5.2 liter engine and then I blow it up and run it into the ground. I then decide to up grade to a 5.9 liter engine because some mechanic talks me into it. Well here is the question.

Some mechanics have said that to get it to run you must use the 5.9
liter computer that came with the engine. Others including the mechanic that installed the 5.9 says it doesn't matter.

WHats your oppinion.

OverkillZJ
07-01-2005, 02:16 PM
I've also heard you need the ECU from the 5.9, and would think you'd need the computer properly programmed for that engine. I've never done it though, so who knows.

Try it. Let us know if it works :rock:

Kraqa
07-01-2005, 03:03 PM
I've also heard you need the ECU from the 5.9, and would think you'd need the computer properly programmed for that engine. I've never done it though, so who knows.

Try it. Let us know if it works :rock:

x2

i'v herd both but i'v only ever seen one guy do it. in a magazine. it was a 1997. but i'm very interested.

LouisianaZJ
07-01-2005, 03:09 PM
on the other hand, one would think with a proper functioning 02 sensor the sensor wouold add enough fuel to the mix accordingly? right?

OverkillZJ
07-01-2005, 03:14 PM
I dunno, 7/10ths of a litre never seemed worth it.

dasVettemeister
07-01-2005, 04:27 PM
Technically the 5.2 liter computer should work just fine --- for the most part. You're not increasing th displacement by a large margin. The thing that would affect fuel demand the most would be a large increase in displacement or an increase in compression ratio (to some extent). The stock injectors have enough headroom in their duty cycle to handle the increased demand of the 5.9L. The only place you might run into problems is with the stock fuel mapping. Keep in mind, the O2 sensor only adjusts fueling at PARTIAL THROTTLE SETTINGS! (typically anything below 80% throttle or so) At Wide-open throttle, the fuel management relies strictly upon existing fuel curves in the computer as well as timing curves. What this means is that the computer can compensate for most lean fueling issues --- until the engine is at wide-open throttle. At this point it would more than likely run lean. You can compensate for this to some extent by fooling the computer and running a higher fuel pressure thereby increasing fueling at WOT without affecting the duty cycle of the injectors. (at least as far as what the computer knows) There are no guarantees with this, it is kind of hit-or miss. It would be easier to deal with the increased displacement and some engine mods if our Jeeps used a mass air flow type injection system --- the computer would compensate for almost any mod at that point with the simple addition of bigger injectors/higher pressure regulator. Unfortunately we are saddled with a speed density system which is not typically very tolerant of major mods.

So, to answer your question...... Yes, the 5.2L computer would work. It would not work perfectly though. To make life simple I would just swap in the 5.9L ECU and be done with it. Otherwise you have the headache of trying to make something work that really wasn't meant to be.

nathaniel
07-01-2005, 06:11 PM
Seems to me that a better idea is using the performance ecm for your year. i think but not positive that the wot isn't a defined map.

Kolak can probably answer that best. or dino or on JU :smt064

haha

dasVettemeister
07-01-2005, 08:13 PM
Seems to me that a better idea is using the performance ecm for your year. i think but not positive that the wot isn't a defined map.

Kolak can probably answer that best. or dino or on JU :smt064

haha

Now that you mentin it...... the computer may take into account IAT values at WOT for fuel trim, I can't remember for sure now. I know it doesn't look at O2 though.....

Jim311
07-01-2005, 09:22 PM
If you're going to the trouble and expense of swapping in a 5.9, why not pony up a few extra bucks and get the right ECU? You're obviously swapping for performance reasons, so why half ass it? I considered doing the 5.9 swap in my ZJ when I blew my 5.2, but I didn't think an extra .7 liters was worth the headaches I knew would probably surface.

dasVettemeister
07-01-2005, 09:42 PM
If you're going to the trouble and expense of swapping in a 5.9, why not pony up a few extra bucks and get the right ECU? You're obviously swapping for performance reasons, so why half ass it? I considered doing the 5.9 swap in my ZJ when I blew my 5.2, but I didn't think an extra .7 liters was worth the headaches I knew would probably surface.

Exactly. I'm with you 100% on that one.

jjunk
07-03-2005, 02:15 PM
The reason being that they didn't swap out computers is the fact the mechanic talked him into the engine and then told him it din't need to be replaced or that the forst owner didn't know you have to replace the computer as well. If you read the start I mentioned that this first buyer had this done and now we are ending up with this problem.

dasVettemeister
07-03-2005, 06:25 PM
The reason being that they didn't swap out computers is the fact the mechanic talked him into the engine and then told him it din't need to be replaced or that the forst owner didn't know you have to replace the computer as well. If you read the start I mentioned that this first buyer had this done and now we are ending up with this problem.

Whatever. :butthead:

gearhead313
07-03-2005, 06:45 PM
why don't you just run the 5.9 short block with the 5.2 heads, intake and the rest of the 5.2l stuff. Worst case it runs leaner due to a little better volumetric efficiency...which would be better anyway.


I've researched this as well and do believe there is a thread somewhere with more information. What I was told was you have to use a 5.9l from a grand which is more difficult to find than a dakota or a ram. I was looking for a ram motor and was told that there was a big timing issue with the engines were there was no way to make it work. I still have yet to know if it works or not. ...damn mopar shit

Jim311
07-03-2005, 07:11 PM
why don't you just run the 5.9 short block with the 5.2 heads, intake and the rest of the 5.2l stuff. Worst case it runs leaner due to a little better volumetric efficiency...which would be better anyway.


I've researched this as well and do believe there is a thread somewhere with more information. What I was told was you have to use a 5.9l from a grand which is more difficult to find than a dakota or a ram. I was looking for a ram motor and was told that there was a big timing issue with the engines were there was no way to make it work. I still have yet to know if it works or not. ...damn mopar shit


When I bought my 5.2L the guy told me that while it was possible to swap in a 5.2 from a van or truck, he didn't recommend it and told me it would cause me a bunch of headaches. He didn't say exactly what, but he said it wasn't worth the time/money to convert when I could get a motor that I knew would fit. That's why I didn't convert to a 5.9... I didn't want to deal with all the headaches and conversion for an extra .7 liters and a marginal horsepower increase for a rig that isn't ever taken to the track and performs great on the trail. There hasn't ever been a situation on a trail where I wanted more power than I had.

jjunk
07-04-2005, 09:01 AM
See here is some debate wether it works or doesn't. IN our case the 4.9 out of a truck does work but not to its full potential. Now our mechanic friend that did all this work is now saying that he installed the right computer from the truck he used. Wich is another lie besed on the block says its a 94 and the computer matches the make of the grand wich is a 93. This guy now claimes that he would ddiagnose it for us and drive it for free but swares that his work was done all rite. So I told my friend to go back to him and let him do that but beware that he will say that the other kid replaced his work and that he didn't use the wrong parts.
Who to believe The more we bother this mechanic the more he is telling us about the vehicle. He told us the other day that he got this motor out of a wrecked dodge truck from a salvage yard. The owner told us that it came out of a 2000 durango RT. My friend today is going to look at the torq converter to see if its the rite one and that it might be causeing his vibration at 3000 rpms as well.

jjunk
08-24-2005, 06:01 PM
Well to update this conversation. My friend and I removed the flex plate and torq converter We found out the the mechanic put in the 5.2 liter plate and converter in and they do not match to the engine and cause a vibration. Then we contacted Kolak and got a high performance computer and now the engine and jeep is running very well at this time. when doing an engine swap use the rite converter and computer for it. THe stock 5.2 liter computer doesn't work at its best.

nathaniel
08-25-2005, 12:43 AM
Well to update this conversation. My friend and I removed the flex plate and torq converter We found out the the mechanic put in the 5.2 liter plate and converter in and they do not match to the engine and cause a vibration. Then we contacted Kolak and got a high performance computer and now the engine and jeep is running very well at this time. when doing an engine swap use the rite converter and computer for it. THe stock 5.2 liter computer doesn't work at its best.

Was the hi po unit from lokal the same year as the jeep or the motor. My guess is the vehicle year.

bigrubbers4x4
08-26-2005, 02:23 AM
all though i have not done a 5.9L swap into one that had a 5.2L, i can tell you this.

when i blew up the tranny in my 98 5.9L, i wanted to use the tranny i had in my 94 grand that my wife totaled to save money, BUT my buddy which owns a tranny shop informed me that the 5.2L tranny is completely different on the inside than the 5.9's. so allthough it will bolt up you will not get the proper performance out of it and it will not last you very long behind the 5.9L. something about not enough clutches and the gearing is all wrong for the 5.9.

it cost me about 3 grand to get the proper tranny i needed for my 5.9 since i spent the one that was in it at paragon so bad it could not be repaired and i made it to #2 on his wall of shame.

so before you do the swap this may be something you want to look further into.