bajajunkie Posted February 9, 2011 Share Posted February 9, 2011 So I was looking around to try and understand why the 4.0 got its power gain in the early 90's (190hp vs 177hp)..... I remember reading that something with the wiring harness changed because chrysler started making them thereselves? Any clarity on this subject? Also what other design changes did they make? to the head? Bigger valves? Different timing or possibly more efficient fuel injectors? Link to comment Share on other sites More sharing options...
shelbyluvv Posted February 9, 2011 Share Posted February 9, 2011 http://en.wikipedia.org/wiki/AMC_Straight-6_engine Link to comment Share on other sites More sharing options...
bajajunkie Posted February 9, 2011 Author Share Posted February 9, 2011 The main idea behind this was to see if you could take an 88 4.0 and easily convert it to an HO. After readig this is it possible to just grab the head, throttle body, injectors, exhaust manifold and ecu unit out of an 4.0 HO if its essentially the same lower half? Probably have to include the harness huh? I'm sure someone has already thought about this.... Link to comment Share on other sites More sharing options...
Red 1989 MJ Posted February 9, 2011 Share Posted February 9, 2011 Make a search in the tech section, I think 3-4 guys have made the swap. Good luck Link to comment Share on other sites More sharing options...
Pete M Posted February 9, 2011 Share Posted February 9, 2011 I would never contemplate this swap with the goal of more get-up-and-go. Lower gearing is a far better way to get that. I would, however, contemplate the HO swap in order to get a lower mileage drivetrain or to fix a severely mistreated renix era MJ. Any boost in HP is offset by a loss of low end torque and that's a whole lot of effort for only a few extra ponies. The HO is not a panacea of power, but they did fix some of the issues that renix era 4.0s can have. :thumbsup: Link to comment Share on other sites More sharing options...
bajajunkie Posted February 9, 2011 Author Share Posted February 9, 2011 That is a very good point! Haha well thanks alot you guys pretty much nailed my question right on he head. Ill be expecting my 4.0 to last another few years then. Link to comment Share on other sites More sharing options...
ratrapp Posted February 10, 2011 Share Posted February 10, 2011 if i had another vehicle to drive i would definitly swap to a ho.i've got a 88 renix with ho head and 99-up intake and atp ho style header and 2 1/2 exhaust and k&n filter.it's got 180k miles on it.my gf's 95 grand cherokee has 4.0 ho and has 200k miles on it.her vehicle has way more power and gets 5 more mpg on the interstate(15 versus 20).we have the same size tires and i know the zj definitly ways more than the mj.my truck has 3.55 gears versus 3.73 in hers but i can't see .18 in gear ratio making that much difference in power and mpg.the chrysler pcm programming is definitly superior to the renix stuff.i worked at a jeep dealership for 5 years and after all the xj,zj,mj and wj's i've drove the renix ones were definitly on the lower end of the pole on mpg and power. Link to comment Share on other sites More sharing options...
Pete M Posted February 10, 2011 Share Posted February 10, 2011 a seemingly small bump in gear ratio can make a huge difference in perceived power. :thumbsup: Link to comment Share on other sites More sharing options...
kyleag89 Posted February 10, 2011 Share Posted February 10, 2011 I have also noticed a HUGE MPG difference between the renix and H.O. Both my 93 and 94 XJs get better gas mileage than either 89 MJs I have driven/owned. My XJs get a good 80miles more out of a tank. EDIT: Both mj and xj had 3.55 gearing auto Link to comment Share on other sites More sharing options...
Pete M Posted February 10, 2011 Share Posted February 10, 2011 XJs have a larger fuel tank. 20.2 vs 18 in a swb MJ. Link to comment Share on other sites More sharing options...
kyleag89 Posted February 10, 2011 Share Posted February 10, 2011 Yes, but that is a huge difference for 2 gallons extra. Link to comment Share on other sites More sharing options...
bajajunkie Posted February 10, 2011 Author Share Posted February 10, 2011 yes while considering the whole go green movement maybe the HO would be a good choice but the idea came to mind because i have only gone wheeling with guys that had HO not the renix. from what i have gained from this the renix will provide more torque at lower rpm and is fully capable of keeping up with any HO with proper gearing and some sense behind the wheel. haha Link to comment Share on other sites More sharing options...
Pete M Posted February 10, 2011 Share Posted February 10, 2011 Yes, but that is a huge difference for 2 gallons extra. but not as big as 80. :thumbsup: Link to comment Share on other sites More sharing options...
Oizarod115 Posted February 10, 2011 Share Posted February 10, 2011 this is definitely the FIRST EVER thread i've heard someone say renix gets LESS mpg than HO... generally speaking the renix rigs tend to do better on fuel :smart: something to consider though, a renix rig is NOT going to inform you that your o2 sensor is bad, your knock sensor is bad, your coolant sensor is bad, your IAT sensor or map sensor is bad, your TPS is out of adjustment. you've got to stay on top of things and make sure that your renix is getting all the information it needs or IT WILL GUZZLE! i noticed a 2-3mpg drop that corresponded with my o2 sensor going bad. Link to comment Share on other sites More sharing options...
bajajunkie Posted February 10, 2011 Author Share Posted February 10, 2011 :smart: something to consider though, a renix rig is NOT going to inform you that your o2 sensor is bad, your knock sensor is bad, your coolant sensor is bad, your IAT sensor or map sensor is bad, your TPS is out of adjustment. you've got to stay on top of things and make sure that your renix is getting all the information it needs or IT WILL GUZZLE! i noticed a 2-3mpg drop that corresponded with my o2 sensor going bad. i think i remember reading somewhere that the renix does not have an on-board diagnostic control system or no storage memory to store fault codes... is this why it won't tell you what is previously stated? if so besides noticing poor engine performance how would you test each sensor to tell if its at fault? would you use a multimeter to test resistance or voltage of each sensor? Link to comment Share on other sites More sharing options...
acfortier Posted February 10, 2011 Share Posted February 10, 2011 http://www.lunghd.com/Tech_Articles/Eng ... ostics.htm This should answer your question. :D Link to comment Share on other sites More sharing options...
bajajunkie Posted February 11, 2011 Author Share Posted February 11, 2011 wow that is some good info definately going in the favorite book marks Link to comment Share on other sites More sharing options...
ratrapp Posted February 11, 2011 Share Posted February 11, 2011 my renix has a fresh tune up(plugs,cap,rotor,wires are mopar units only a few years old)and it has new 02 sensor and tps sensor.also upgraded to the new 4 hole injectors,k&n filter,redline synthetics in the differentials and t-case and it still doesn't get the mpg that my gf's zj does.my grandmother has a 96 zj with 3.55 gears in it nad it gets even better gas mileage than my gf's zj.on the interstate my mj gets maybe 15-16,gf;s zj gets around 20,grandmothers zj gets 21-22.when i figure mpg,i fill it completely up drive a distance,refill and divide.you cannot go by gas gauges as we all know mj gas gauges aren't the greatest.also somepeople don't take into consideration that different size tires and axle ratios aslo mess with the mileage recorded.i had to change my speedo gear in my truck to compensate for going from 215/75s to 235/75s.i had a buddy whos a state trooper clock me to see how close it was.i was less than 2 mph off afterwards.this truck barely got more mpg than this when it was new.my grandmother booght it with only 8k miles on it and it was only a year old.it now has 180k and still going fine. Link to comment Share on other sites More sharing options...
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