88whitemanche Posted July 9, 2014 Share Posted July 9, 2014 Napa/Echlin High Altitude CPS PN: ECH CSS637 For the 4cyl.... If it helps anyone.... Link to comment Share on other sites More sharing options...
AMCJeepMJ Posted July 9, 2014 Share Posted July 9, 2014 cruiser54, Please tell me more about the high altitude CPS. Does it fit the High Output 4.0? Am I correct that it advances the timing a few degrees to compensate for lower density air at high altitude? Has anyone used this on the 4.0? Thanks for any information. You are correct in what it does. It was for the Renix models only. For the HOs, the ECU handles that function. I don't think it adds any power or torque, unless you run mid-grade or hightest gas. The Renix engines have a knock sensor to retard the spark when they sense detonation. And that usually happens under load. What the high altitude CPS really does is allow more advance under light load, which boosts the fuel economy. Napa/Echlin High Altitude CPS PN: ECH CSS637 For the 4cyl.... If it helps anyone.... That's about a $50 part at napaonline. Did these come stock from the factory for models sold at higher elevation dealerships, such as in mountainous areas [Denver, SLC, Casper, etc.], or is this an aftermarket-only add-on? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 9, 2014 Share Posted July 9, 2014 Install a high altitude CPS. Are those still available? I thought I bought the last one in captivity about four years ago. I did from the dealer. But as it turned out the PC307 from RockAuto was a Siemens, made in France. I think they're still available. cruiser54, Please tell me more about the high altitude CPS. Does it fit the High Output 4.0? Am I correct that it advances the timing a few degrees to compensate for lower density air at high altitude? Has anyone used this on the 4.0? Thanks for any information. No, it does not. A stock one can be modified though. Link to comment Share on other sites More sharing options...
johnj92131 Posted July 10, 2014 Share Posted July 10, 2014 Kind of figured it would not work with the H.O. engine. Next question is how to imitate the old vacuum advance distributor function in the High Output engines. I "assume" the OBD 1 ecu performs that function to the extent possible, within emission constraints. But I would also guess the vacuum advance function can be improved under low load conditions of highway driving. And that leads to retuning the stock ecu by who? Link to comment Share on other sites More sharing options...
Eagle Posted July 10, 2014 Share Posted July 10, 2014 Kind of figured it would not work with the H.O. engine. Next question is how to imitate the old vacuum advance distributor function in the High Output engines. I "assume" the OBD 1 ecu performs that function to the extent possible, within emission constraints. But I would also guess the vacuum advance function can be improved under low load conditions of highway driving. And that leads to retuning the stock ecu by who? I believe you can buy "power chips" to fit the OBD-1 HO engines. I know they are available for the 4.0L engine in the ZJ grand Cherokees. However, every review I've seen (disclaimer: I haven't looked at this for several years) reported that it was necessary to run premium gas with the power chip installed. So you get more power, but you pay for it. With gas hovering around $4/gallon for regular, personally I would not be in a rush to install a mod that requires me to spend an extra 30 or 40 cents per gallon. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 10, 2014 Share Posted July 10, 2014 For the OBD1 HOs you can slot the CPS mounting holes and slide the sensor closer to the passenger side to advance the timing 2-3 degrees. Also a piggyback performance chip such as the Unichip or Jet2 can be programmed to advance the timing by altering the CPS signal (along with the IAT, TPS and MAP) to the ECU. I've done it with my Unichip (before it smoked) and verified the timing advance with a timing light. It was a slight performance improvement if you used higher octane fuel and wasn't worth the extra $$ for me. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 10, 2014 Share Posted July 10, 2014 For the OBD1 HOs you can slot the CPS mounting holes and slide the sensor closer to the passenger side to advance the timing 2-3 degrees. Also a piggyback performance chip such as the Unichip or Jet2 can be programmed to advance the timing by altering the CPS signal (along with the IAT, TPS and MAP) to the ECU. I've done it with my Unichip (before it smoked) and verified the timing advance with a timing light. It was a slight performance improvement if you used higher octane fuel and wasn't worth the extra $$ for me. Too bad those new-fangled HOs don't have knock sensors.............. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 10, 2014 Share Posted July 10, 2014 For the OBD1 HOs you can slot the CPS mounting holes and slide the sensor closer to the passenger side to advance the timing 2-3 degrees. Also a piggyback performance chip such as the Unichip or Jet2 can be programmed to advance the timing by altering the CPS signal (along with the IAT, TPS and MAP) to the ECU. I've done it with my Unichip (before it smoked) and verified the timing advance with a timing light. It was a slight performance improvement if you used higher octane fuel and wasn't worth the extra $$ for me. Too bad those new-fangled HOs don't have knock sensors.............. Yes, that was a good Renix feature. When they worked. Link to comment Share on other sites More sharing options...
CobraMarty Posted August 4, 2014 Share Posted August 4, 2014 Supercharger like this- here Link to comment Share on other sites More sharing options...
Jeepman Posted August 4, 2014 Share Posted August 4, 2014 If you can Fab then I would say build your own supercharger mount and get the Eaton M90 off a Mustang or Thunderbird Supercoupe from eBay or your Local Junk yard... That's what I am doing but for a 4.7L stroker... And it will cost you far less then $2500.00 Link to comment Share on other sites More sharing options...
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