WTF is Renix?

[Mitch]

I have an 89 4.0L is it a Renix? What does this mean? I know nothing.

[Pete M]

It's a combination of Renault and Bendix, the 2 companies that got together to develop the first gen fuel injection system in MJs and XJs (86-90).

[Mitch]

Is that a good thing or a bad thing... according to your post, I do have a renix. Now tell me more! :D

[Rob S]

The Renix is basically the 4.0 before it became the H.O engine in 91. The power is a bit less than the HO, however it does have a good low rpm torque rating, better than the HO. Pretty solid engine, rearmain seal is the only weak spot I know of, usually needs replaced around 100k or so.

[91mj97tj]

I also think the cooling system is a bit HOKI or whatever you want to call it. They really didn't perfect it until 2001. But that is just my opinion. I have rebuilt the head on a renix Cherokee pain in the @$$ getting it to take Radiator fluid.

[Oizarod115]

I also think the cooling system is a bit HOKI or whatever you want to call it. They really didn't perfect it until 2001. But that is just my opinion. I have rebuilt the head on a renix Cherokee pain in the @$$ getting it to take Radiator fluid.

 

i had a worse time with a bone dry HO taking fluid than i had with my renix :dunno:

 

but yeah, they can be a PITA to get coolant in them, just gotta be patient

 

the renix system is good becuase the computer doesnt save anything, it resets with new information every time you start it. and it has a knock sensor

[87manche]

OK, here's the run down.

 

Renix parts are a bit more expensive, and can be harder to source if you don't have a good parts store. Simply because there are less of them on the road than the HO variants.

The block is basically the same as an HO.

When chryco went to HO in 91 they redesigned the head and changed the camshaft profile so they could delete the EGR system.

The renix ECU does not store codes, it doesn't even have a check engine light. So if something stops working properly get out a voltmeter and go to town.

The sensors are incredibly basic, and about 90% of the parts can be tested with a voltmeter. From a reliability/fix it on the side of the road standpoint, I feel that the renix system is better. The HO system does have it's merits, but I just like the renix, as I feel it's much more fault tolerant. So long as it has a MAP/TPS/CPS input it will run.

It does however use an odd O2 sensor, so don't go wiring in a "universal" cheap one from the parts store, they're the wrong type.

 

About the EGR, it's sometimes problematic, and usually expensive to repair. If it breaks, just get some block off plates and delete it. Of course, this is assuming you don't have a visual emmisions check.

[91mj97tj]

Well I agree that it is way more fixable and maybe because most HO are not that high in mileage as the Renix but honestly my pal that I help rebuild is constantly fixing it finally he said screw it sold that and (how lucky he is) got a free 2.5L but he likes that because he is extremely cheap. But I really do not like the renix because it just makes me so mad working in a crammed engine compartment with a very flawed huge system.

[87manche]

Well I agree that it is way more fixable and maybe because most HO are not that high in mileage as the Renix but honestly my pal that I help rebuild is constantly fixing it finally he said screw it sold that and (how lucky he is) got a free 2.5L but he likes that because he is extremely cheap. But I really do not like the renix because it just makes me so mad working in a crammed engine compartment with a very flawed huge system.

it is mostly because all the renix rigs are 20 years old.

if he were to inspect every electrical connection/clean every connector I bet it would work and run just like new. That's what it took for mine. Takes a weekend.

[Eagle]

But I really do not like the renix because it just makes me so mad working in a crammed engine compartment with a very flawed huge system.

What system is flawed? There are numerous areas in which the Renix system is better than the later Chrysler system. The fact you don't like it doesn't make it "flawed."

[Mitch]

do they make vacuum line replacement kits for these renix 4.0? where can I find one cheap? I think that would help a ton as most of my lines are brittle and filled with oily crap.

[91mj97tj]

Well I did go outside my scope there with saying flawed. I did mention the fact that most HO are not long time or high mileage whatever. But I do believe working on HO is much easier. So you can say the reverse the HO has many areas in which it is better than renix.

Also I am not sure on this one but I am pretty sure you can not do a throttle body spacer on the renix another "flaw" or weakness. One of the easiest and best upgrades you can do.

[Pete M]

Not exactly a huge flaw there seeing as spacers are pretty worthless on an MPI engine anyways. :D IF there's some data out there that shows otherwise, I'd love to see it. (and no, data from the spacer's manufacturer doesn't count). But I digress...

 

The Renix engines are awesome. The 4.0L in my 88 is pushing 200k and has been through more crap than I can recall. This includes a couple different oil starvation problems and a couple overheating situations (pegging the temp as far over as it would go). The 4.0 in my 90 has 210k miles and still purrs. :D I bought a 110k mile 89 4.0L to drop in the 88 because it was such a low mileage block I couldn't pass it up and I figured the 88 would eventually die. That was a couple years ago and that new block is still just sitting on the engine stand in the garage. She just keeps going and going and going and...

[91mj97tj]

The first 4.0 engines in 1987 had RENIX (Renault/Bendix) engine control systems, which were quite advanced for their time, but are now handicapped because there are very few scan tools which can be "plugged in" to a RENIX system for diagnosis. The Renix also used a very advanced engine knocking sensor, which allowed the computer to know if detonation was occurring, thus allowing the computer to make the appropriate changes to prevent this.

 

The 1987 RENIX 4.0 made 173 hp (129 kW) and 220 lb-ft (298 N·m) of torque. In 1988 the 4.0 received higher flowing fuel injectors, taking output to 177 hp (132 kW) and 224 lb-ft (304 N·m) respectively.

 

In 1991 Chrysler Corporation, then the owners of the Jeep brand, redesigned the RENIX engine control computer and raised the intake ports approximately 1/8″ for a better entry radius. Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for more efficiency, and the fuel injectors were once again replaced with higher flowing units. The camshaft profile was also changed. The net result of all these changes was an engine that made 190 hp (142 kW) and 225 lb-ft (305 N·m) of torque. Badging on Jeeps equipped with this engine read "4.0 Litre HIGH OUTPUT". The new cam profile combined with altered computer programming eliminated the need for an EGR valve and knock sensor, but make the engine more sensitive to alterations, especially where emissions are concerned.

 

Small changes were made to the cylinder head for the 1995 model year. In 1996, the engine block was redesigned, and a new strengthened unit was then used. The new block made use of more webbing cast into the block, and a stud girdle for added rigidity of the crankshaft main bearings. The cylinder head was also again changed around 1998 to a lower flowing, but more emissions friendly, design. Engines installed in 1999 Grand Cherokees carried the Power Tech name, which was subsequently passed on to 4.0s in all Jeep models.

 

 

Sorry kind of long also just what I think about throttle body spacer they do offer a good power increase that can be noticed and I really don't need to go into it because you can just search online from all the blogs and forum postings. Because there are not that many power performance mods you can do for the 4.0 but it is a combination of a lot of things. Best one that I have seen and pretty common on the trails here in Utah:

http://www.jeepersandcreepers.com/clien ... atPath=102

I do love wrenching on things but one of them is not that engine every weekend. Junk it and go to a rolled newer 4.0 vehicle or I really like v-8 mods which I am doing a 350. Because of the cheaper aftermarket parts and the performance mods are limitless. JMO

[comancheman]

i just don't see how a throttle body spacer can do anything on any MPI system. w/ TBI i understand how it allows more time for the fuel and air to mix but will someone please tell me antidisestablishmentarianism it does for MPI

[JeepcoMJ]

renix also DOES get better fuel mileage than the HO because the timing isn't so advanced (literally, advanced, not technologically)

 

i prefere the renix 4.0. if you ever decide you want more power from a 4.0, bore the renix before switching to the HO. it'll turn out better.

[DirtyComanche]

Not exactly a huge flaw there seeing as spacers are pretty worthless on an MPI engine anyways. :D IF there's some data out there that shows otherwise, I'd love to see it. (and no, data from the spacer's manufacturer doesn't count). But I digress...

 

 

 

 

I got in a really good pissing match with somebody over this once. He resorted to calling me names; so I think I won.

 

 

Anyways, the short and simple answer on them is they cause the engine's powerband to be shifted slightly upwards in the RPM range slightly. Which is an effect caused by them mimicking a longer intake runner. This means you get a higher peak HP (by like 2-3!) and a lower peak torque (by like 2-3!). They are more effective on an engine that is built to rev high. Ones with spirals don't help anything. And yes, they are avaliable for the renix. Better yet - make your own. At least you'll have learned something doing that.

 

 

And there's lots you can do for the perfomance of a 4-oh. I'm not one to bother, but if a guy is willing to spend some time (not money) you can make some pretty respectable power out of them.

 

 

Anyways, about the renix and the HO. Well. I hate both of them. But I hate the HO more (personally). For some reason they eliminated the knock sensor in the HO which, while not a huge deal on a truck engine, ment they went to a static timing curve. The result was a less efficent engine with poorer fuel economy; and less power output if equipped with the same head.

 

Besides, I hate a check engine light. I'd probably just take the bulb out the first time it came on.

 

 

 

Every issue I've had with the renix is my own neglect and my unrelenting urge to modify things that should be left well enough alone.

[91mj97tj]

This is quite an interesting subject. I have never heard of anyone defending a Renix system. Almost like defending the pugeot tranny. In your guys knowledge of the things. But my friend rebuilt the whole thing still was in the garage on the weekends while we were out on the trail. He had to get it running by Monday. I respect them for the time they were in Jeeps. I just respectfully :bowdown: I guess. MPG is really debateable though and I will never concede that.

 

What kind of MPG are you looking at in a manche? Cherokee or Wrangler? Depends on gearing what kind of tranny what mods you have done. It is just not money because TIME is money mr trump. I love bolt on bought parts. Do it right once=pay for it up front.

 

And to think all I thought I said was that the 4.0 achieved engineering perfection in 2001 even more so in the LJ. I really like the 4.0 I have in my 97 as well. But it was designed better in 2001.

[offroader461]

i honestly have not had that many problems other than the usual idle thing with my renix...and the same with my poogeut...i run synthetic fluid in my trans and havent had any problems yet....well see tho...lol

[Oizarod115]

so i guess mine has the worst of everything :D no knock sensor, but renix ignition, and no egr because its a 97. closed cooling system, and probly alot of effed sensors :roll:

[DirtyComanche]

The closed cooling system is actually superior to the open one - you just have to keep it together. Almost all modern vehicles run them for a reason.

 

 

99% of the time it's the stupid plastic resivoir or cap that goes.

[Pete M]

Yup, a closed/pressurized system allows the coolant to maintain a higher temperature and the engine burns more efficiently at higher temperatures.

[Eagle]

i just don't see how a throttle body spacer can do anything on any MPI system. w/ TBI i understand how it allows more time for the fuel and air to mix but will someone please tell me antidisestablishmentarianism it does for MPI

+1 ... And I think we can count Pete's post as +2.

 

Since an MPFI system injects the fuel directly into the cylinders at the head, it's difficult to imagine any way in which a throttle body spacer could make much of a difference. It pretty much CAN'T affect the fuel atomization, and it pretty much CAN'T affect the velocity of the air charge as it enters the cylinder because that's a function of the pistol speed and valve opening ... what's left?

 

Yeah, I know the people who make and sell throttle body spacers claim massive increases in horsepower, torque, and economy -- all of which are mutually exclusive. I'm still waiting to see independent corroboration.

[91mj97tj]

Yeah, I know the people who make and sell throttle body spacers claim massive increases in horsepower, torque, and economy -- all of which are mutually exclusive. I'm still waiting to see independent corroboration.

 

This is just a guy and you can just search in many forums and a lot of people will tell you there is a difference in how your vehicle runs. http://www.jeepin.com/features/throttlebody/

I compare it to this: Waited way too long to change the spark plugs/tune up in my 2.5 L MJ probably had been the same ones before the rebuild of it because my dad was cheap (who I bought my MJ off of). So I did and it ran like a different vehicle. My brother said you wouldn't be able to tell period well I drove that sucker everyday and let me tell you a difference was felt in response, idle, mpg, etc.

Now for throttle body spacer that Jeepers Creepers thing is great put it on the 97 it is a little more responsive, 1-2 increase in MPG, idle is a lot smooter, this is on a 87xxx mile engine, and stock air filter. Next mod is air filter haven't made up my mind on what kind probably Brute force. The only thing you have to remember about perfomance mods is that Dyno is conducted at sea level, and whether it is HP at the wheels or not.

[87manche]

This is quite an interesting subject. I have never heard of anyone defending a Renix system. Almost like defending the pugeot tranny. In your guys knowledge of the things. But my friend rebuilt the whole thing still was in the garage on the weekends while we were out on the trail. He had to get it running by Monday. I respect them for the time they were in Jeeps. I just respectfully :bowdown: I guess. MPG is really debateable though and I will never concede that.

 

What kind of MPG are you looking at in a manche? Cherokee or Wrangler? Depends on gearing what kind of tranny what mods you have done. It is just not money because TIME is money mr trump. I love bolt on bought parts. Do it right once=pay for it up front.

 

And to think all I thought I said was that the 4.0 achieved engineering perfection in 2001 even more so in the LJ. I really like the 4.0 I have in my 97 as well. But it was designed better in 2001.

In order to work on it you have to learn it.

honestly I can diagnose just about any issue anywhere/anytime with a DMM, but I've also practically memorized the renix MPI FSM.

 

As to mileage, I made an 700 mile trip with 1K lbs of camping/tires/bumper in the bed and still managed 22 MPG on the highway.

not bad for a 20 year old truck with a "flawed" fuel injection system.

 

Point is, the Renix system is much more adaptable, runs the motor using realtime information from it's sensors, and is pretty much bulletproof.

It just takes a little love to make it reliable, but I honestly haven't worked on the engine management in a year. I've spent more time repairing hard drivetrain parts than anything in the electronics.