2 x cps = +6* timing

[slappomatt]

I know very little about the jeep FI. Would this work on my 95 4.0? I would like to get a little more power out of the stock system until I can get around to going standalone ecu.

 

[cruiser54]

Yep. It would work. It's noticeable but not hugely.

I use the "vise and bolt" method to move the plastic piece of the CPS on it's bracket.

 

[CobraMarty]

Hey Talyn,
Great mod. Can you advance the stock timing with the AEM?

 

[streetxj]

Nice free mod. :yelclap:

 

[Talyn]

No, you can only retard it with the FIC. No piggy back can advance timing. If they could they would either have to see in to the future or do it in an incorrect way.

 

[O-Gauge Steamer]

No, you can only retard it with the FIC. No piggy back can advance timing. If they could they would either have to see in to the future or do it in an incorrect way.

Absolutely correct.

The logic in the controller takes in all of the data inputs, looks up, in the tables, what it is supposed to do with that data and then sends the signals, appropriately modified, onto the PCM. It is physically impossible for the electronics to send the signal out prior to getting the trigger.

Unless, of course, you have the optional Flux Capacitor installed...

 

[CobraMarty]

OK so in a supercharger application, Would you do the 6 degree mod for when out of boost N/A for better perf and mileage and then with the AEM can pull back the timing the 6 degrees plus 1-2 degrees per pound of boost?

Do you know how much timing advance the Superchips Flashpaq puts in? How do they do it, the timing advance thru the OBD port?

 

[Talyn]

I see no problem with advancing it then pulling it out under boost.

You can advance the timing through the PCM as trigger wheel is basically advanced to signal the CPS. I also had an additional 6* added when I had my PCM retuned.

 

[CobraMarty]

Interestingly, today I called Superchips and they said that with their programmer they can change the timing and fuel tables thru the OBD port. He said that they can add up top 10-20 degrees advance and usually lean it a bit at different points throughout. Not like add 6-8 degrees everywhere. Because you can't tell where they add what I don't see how to use their flashpaq in a boosted application.

 

[O-Gauge Steamer]

And there, is the difference between a hardware modification and a software modification. If it weren't so bloody expensive to get the software so I could overwrite my PCM, I would go that way. But no... Being retired sucks, don't do it!

Hardware mods, as in the 6 degree mod here, are always by their very nature limited in scope. That being said, I have this mod on my Heed (Thanks to Talyn for finding it...) and have retuned my F/IC8. Made a noticeable difference when under partial pressure, i.e. not positive (boost) pressure. A snappier pickup until I go into boost. Thing is, I go to boost pretty quickly. There are hills here I happily run up at 40mph in OD (AW4) under 2 pounds of boost. Under partial throttle... Pre-boost days, the trans would shift out of OD and require more throttle to take the very same hills.

Some call it Vacuum, those of us that are dealing with not only the AEM F/IC, but have a Physics background know better. I sit at 12.5psia (I'm at a 6500' elevation, close enough) with the engine off. Those at sea level sit at 14.7psia. Assuming a "normal 1 bar" barometric pressure day, of course.

The a is for Absolute Pressure. If you are reading a run of the mill pressure gauge, you are reading psig or gauge pressure which is a relative to atmosphere pressure. And yes, that means that 10 pounds right now may not be 10 pounds in an hour. Depends...

So, best case, I get 2.2 pounds less boost here than at seal level. Less when I head on up to over 10,000'. On the other hand, given that the performance of vehicles here are compromised due to the altitude, I can still blow the little Ricer's with their Fart Can Exhausts off the road.

Here is something for you guys to think about. The Speed of Light is a Constant. Right? Wrong... The actual spped of light depends entirely upon the current barometric pressure, the air temperature and the humidity. Weird eh?

See what happens when an Retired Senior Engineer has too much time? Physics Lectures...

 

[CobraMarty]

I bought a couple of $10 CPS to take apart. I want to try slide it along. Can I drill out the backside to release it? Pry it apart and break the glue? I am sure I will ruin them but I will figure out how to reliably more/slide the sensor along the bracket.
Any insights or ideas?

 

[cruiser54]

Marty, I've been doing this since 1987.

The sensor portion of the CPS needs to slide up the perforated bar towards the top of the engine.

Mark the perforated bar's top end with paint or marker.

Place the CPS in a vice, just not quite clamping the bar, the sensor resting on the vice jaws, with the Top part protruding.

Place a bolt that fits tightly into the hole at the Top part of the bar.

With a hammer, tap the Top part of the bar and it will slide through the sensor portion of the CPS. Stop when the sensor portion is about 3/8" from the edge of the bolt hole.

 

[kastein]

Interestingly, today I called Superchips and they said that with their programmer they can change the timing and fuel tables thru the OBD port. He said that they can add up top 10-20 degrees advance and usually lean it a bit at different points throughout. Not like add 6-8 degrees everywhere. Because you can't tell where they add what I don't see how to use their flashpaq in a boosted application.

And there, is the difference between a hardware modification and a software modification.

Agreed. with software you can add a bit of code that simply watches the set of cps trigger notches before the normal ones, then adds say 60 degreees of timing from there, which gets you right back to factory. Then take out some of that 60 degrees when you want to advance the timing... this isn't possible with hardware unless you build something smart enough to interpret the cps signal, figure out how fast the engine is moving and where it is continuously, and use that to constantly update a generated cps signal stream that it sends to the ecu with whatever advance you want added to it. And even then without being very careful you would probably trigger the misfire detection in the later, smarter ECUs.

 

[CobraMarty]

The idea is to advance the timing with the 6*CPS mod which seems to help overall N/A performance throughout the power band, and then use the AEM F/IC to 'retard' the timing where necessary.

I will break out the hammer and vice later. Thanks. Maybe super glue it in it's new position.

 

[cruiser54]

The idea is to advance the timing with the 6*CPS mod which seems to help overall N/A performance throughout the power band, and then use the AEM F/IC to 'retard' the timing where necessary.

I will break out the hammer and vice later. Thanks. Maybe super glue it in it's new position.

You can but I've never found it necessary.

I had a SC Miata and did what you guys are doing, although a little differently. Advance the timing for better throttle response before boost and then used a J&S timing retarder to pull timing with a knock sensor input. It would pull up to 20* as needed. Never saw it pull more than 10* even in Arizona in the summer.

 

[CobraMarty]

So I found out that you can't just 'put it in a vise and hit it' and slide the metal thru. The metal has a recess stamped in it to which the sensor is molded to it. When I tried to more it the sensor plastic broke and I can see how it is made and there is no way for it to slide/move, it is locked in place.

 

[cruiser54]

That's weird. Perhaps an aftermarket unit that I've never seen. The factory units have little holes the length of the bracket with no recess to hold the sensor.

 

[Talyn]

I tried to put it in a vise and hit initially to move it. It just bent the bracket. You can cut it apart, move it and then epoxy it in place if you want.

 

[O-Gauge Steamer]

Well. It makes a ton of sense, to me, that the factory sensor would have a positive locator stop and an aftermarket (read cheap repro) would not. The factory has to warranty the sensor to last and guarantee to the Feds that the timing will not change thus affecting the emissions. What this means is that the timing, using an aftermarket Sensor, could be anywhere.

Always better to go to Jeep for a Sensor... Worth the extra bucks to get a good part.

 

[cruiser54]

Well. It makes a ton of sense, to me, that the factory sensor would have a positive locator stop and an aftermarket (read cheap repro) would not. The factory has to warranty the sensor to last and guarantee to the Feds that the timing will not change thus affecting the emissions. What this means is that the timing, using an aftermarket Sensor, could be anywhere.

Always better to go to Jeep for a Sensor... Worth the extra bucks to get a good part.

The point is that the factory ones DID NOT have a factory stop or indentation. We started doing the mod with the vise back in 1987 when I got the 2nd of my 13 4.0 equipped Comanche demos at the dealership.