Tech info : Supercharged fuel injected 4.0 . 1994 , stock ignition ,
I am having a pinging problem at full throtle . Lets get this out of the way right off the bat . I am not going to buy an after market ignition ! This is not an option at this time .
1: I need to retard base timming 3 to 6 degrees
2: Or retard the timming at full throttle .

3: I have herd about a plug on the 4.0 that can be disconected to change the timming . It has to do with the electronic advance ??
A: any one farmilar with this
B: where is it
c: what does it do .


4: I know the crank sensor tells the computer timming . I also know a turbo place sells a sensor that advances the timming 3 degrees. theyacomplish this by slotting the mounting holes .
a: I'm wondering would you slot the holes to the left or the right to retard . The position of the sensor confuses me because it faces the crank from the back side .
b: Has any one done this modification advance or retard ?


5: Does any one here have any other ideas about getting the base timming retarded ???

6: I have never fooled with the didtributer on my 4.0 . I have been told that you cannot turn it unless you modify it . Is this true ?

7: Electronic Advanse and weighted advance .If memory serves me correct a timming advance mechanism rilly doesent advance the timming. The advance mechanism actualy retards the advance . More rpms = less advance . correct ??? The name of the system is missleading . this was true in the old mechanical weight distributer systems .If its still the same this would not help to mess with it ..

Now with that said anyone have any good technical info for me .

Thanks for your time

The Bear

turbo city, (rockit.com)
can supply you with the CPS adjsuter.
the distributor can be adjusted, but you need to grind off the indexing key on the collar of the distributor. This will effectively "lie" to the computer, as it relies on the relation between the camshaft sensor in the dist. and the CPS to set the timing. Some have used this trick to adjust for badly placed CPS brakets on 4.0L swaps, I imagin it will work for you, too.
Late model 4.0L's (After 1990) do not have a knock sensor, that is why some prefer to use the older systems for forced induction.

turbo city, (rockit.com)
CPS adjsuter Adavances the timming . I need to retard it .. Thats why I wanted to elonggate the holes on a OEM .

Bear

Info I have recieved fri=om a friend .. Any one herd of ths ???

--------------------------------------------------------------------------------first look at the wire loom that runs to the distributor, you
should see a plug with two wires that go to nothing, it runs directly into a plug that has two tabs on the
outside that you need to spread very little and the end has an indentation in it as if they had in mind that
you would use your thumb and index finger to pull it out, it should be grey in color, it may not be right
around the distributor it may be in the loom right next to the fuse box mounted above the fender-well.
Once you locate the plug simply unplug it, hook up your timing light pickup to cylinder #1 and positive
and negative side post of your battery, start the engine and see what the timing is using the marker on the
front of the timing cover, you might have to clean the balancer with some emery cloth so that you can see
the marks. When you have established the baseline you can make your adjustment accordingly.

----------------------------------------------------------------------------------
Ok lets put our thinking hats on because I have one charecter flaw when it comes to this jeep/charger thing . I will not give up and I will not pay for somthing I can do . the people I talked to when I wanted to supercharged the YJ .
No Brian you cant trick the computer into not knowing the charger . No Brian you cant trick the computer into thinking you need more fuel . If I listened to all the naysayers I would still have The Eaton charger on the bench . I even talked to the guy who helped design the computer . And he was incorrect . I will not give up . Can you give me any info on the high altitude crank position sensor??
what is its purpose ??? what does it do differently than the normal CPS ??.How about I trick the computer into thinking top dead center is actualy 4 degrees before top dead center . Changing the Cps and the cam sensor . The Turbo city CPS advances the timming by repositioning the mountiog holes Efectivly slotting them so its adjustable . I was told the high altitude CPS is the same way and moves the sensor up to 8 degrees (not sure which way on the high altitude CPS)
If this is the case I can go 8 degrees either way???


Bear

Go to the tech index of my page, and you shall find EXACTLY what you need.

had to do same with my 4.5L stroker with over 10:1 compression

http://members.tripod.com/BillyXJ/Billstechindex.html

Thanks BillaVista. I think I need to do some retarding to my Jeeps CPU too. It doesnt quite run perfect after doing the 4.0L head swap on a 4.2L block with an MPI injection kit... Half 4.0L and half 4.2L :D It still has tons of power but I talked to hesco and they said the timing needs to be advanced in order for this combo to really work ideally... Also I like your SOA conversion on the front of the chero. My friend and I did this to his Cherokee about a year ago. works awesome!! I was unaware there were other people doing this conversion. :smokin:

The bear, your friend is correct about timing, but it is for a Ford eecIV. That is called a spout connector, or spark out. Mopar dosn't use one. Timing is completly controlled by the pcm.

Your first step should be hooking it up to a scanner. A Snap-no or Chryslers DRB will both work fine. Sometimes programmed into the pcm is a function that will allow you to retard total timing up to 6 degrees, 2 degrees at a time. If your computer dosn't have this function, then you should modify your cps position.

If you modify your cps position, you should also modify your cam angle sensor (pick up in the dist.) These 2 sensors should always be in "sync". Usually Mopar has a function in the pcm which will allow you to sync your dist. (3.9l V-6's and all Magnum V-8's) This is done by going to the sync page, and turning your dist. until sync is achieved. The 4.0's usually don't have a sync page in them because the dist. is keyed so it can't be turned. If you modify your cps position, you should pull your dist. and grind off the tabs so you can turn it. You can watch the count of sync signals on a scanner, so guessing how much to move it is easy.

If you modify the position of your cps, you will want to move it with the rotation direction of the flywheel, this will retard timing. If you move it into the rotation, you will advance timing.

The "high altitude" cps is off-set 8 crankshaft degrees, which is 4 dist. degrees. You want to go the other way, retard it about that much. BillaVista's method should work fine, but he should try tweaking the position of dist. to help keep everything in sync. If a Mopar injection system is out of sync. you will give hard starting, rough idle, and poor on demand power, especially up hills.

I remember reading about all the people that shimmed their cps up with the Mopar kit, and saying it didn't help with detination. They went the wrong way. You want to shim the mount down, with the rotation direction of the engine.

Something you should think about with a blower on your 4.0 is the camshaft. The camshaft profile on most engines use a lot of valve overlap. They do this to help prevent denition. Using a lot of valve overlap will allow a small exhaust charge to be sucked in the engine on the piston down stroke. This is the egr. You can advance timing, get higher cylinder pressure at a lower temp. and actually gain horsepower! If you use a blower or turbo, it will just push the intake charge out the exhaust. Changing your camshaft to one that has 0 degrees of overlap will probably give you another 20% horsepower!

I should have mentioned indexing the distributor for the new CPS position - I guess I'll add it to the article. The book way to do it, stock, is to set #1 to TDC, then use a cut away dist cap to check that the gap between the leading edge of the rotor tip and the #1 terminal is .020".

I just "tuned it by ear" (i.e. ground off lock tab, reinserted dist, and twiddled it back and forth for best performance by sound) for the new CPS position.

That is a nice article BillaVista. Did know that the large Ford cap adapt will fit on a 4.0's dist? I had that set-up on mine with a Jacobs coil and computer. It made it ping real bad, so I disconnected it.

I live at 7,000'

when you move the CPS like that to retard timing, you also change injector timing. Does this not inject fuel at a later time in the stroke and cause driveability weirdness or does the intake valve close before all the fuel gets in? Also, do the aforementioned scan tools such as the DRB and the Snap-On talk to the old Renix systems? Can you adjust timing with one of these on a Renix?

The crank sensor only adjusts ignition timing. The cam angle sensor is responsible for injector timing and identifying where cylinder #1 is. You can unplug the older Renix dist. sensor when the engine is running and it will continue to run, but in a sychronious mode, and not sequintial. Most of the problems associated with sync. is called "circuit gap". The ignition is firing when the rotor is not lined up with the cap. I believe that on the Mopar system, they fire the injector 3 cylinders ahead of the one firing. They use the "puddeling effect". This is the principle of port fuel injection. The fuel is not squirted directly behind an open valve, but just before the valve opens. They use the heat of the hot intake valve to atomize the fuel. It will sit in a vapor puddle until the valve opens. This is why fuel injector cleaners work so well. It isn't due to the higher volume from the injector as much as it is cleaning off the oliphins behind the intake valve. This allows better heat robbing properties of the fuel from the valve.

The older systems can be scanned. The pcm has no function for retarding timing, and the don't even have the ability to store codes. About the only thing you can read are some sensor values and block learn values. They are also nice when changing tps's, you can set it the value using %. I believe it calls for something like 13% at idle.

All info has been saved . Timming retard will be accomplished this winter ..

Thanks Bear

when you move the CPS like that to retard timing, you also change injector timing

No you don't.

do the aforementioned scan tools such as the DRB and the Snap-On talk to the old Renix systems?

They listen, but don't talk!

Can you adjust timing with one of these on a Renix?

Nope.