evercloud

I understand that many people get "noticeable" power gain by tuning the ignition timing on the Jeep 2.5L TBI four-cylinder engine. Some relocate the IAT in a cold place (cheap but small power gain) and others drilled a new position for the CPS to get 3-4 degrees variation. CPS relocation mod made me realize that timing can be tweaked by editing the signal going from cps to ignition module. I'm not into drilling the engine, so I called the italian AEB to get a controller (to be installed on the CPS line going to the ignition module) to adjust timing and they answered that is definitely doable, but they need a oscilloscope report of the CPS signal to give me a module that fits. I'll let you know if I get any further in this direction. In the meantime, do you know of any kit/ecu/module/processor designed for this purpose? Googling "adjust timing on yj" mostly returns a useless "you can't adjust timing by turning the distributor". Happy New Year! Claudio

Hi Moses! Engine upgrades slowed down because of Christmas and New Year holidays (best wishes, BTW!), but that gave me time to do some research. Talking about intake manifold, I believe TBI and MPFI headers to be the same as I read people swapped engines between tbi and mpi (and vice versa) easily by leaving manifolds (together with harness, tb, ecc) from the recipient car. I also found websites selling the same intake/exhaust gasket for all 2.5 engines. As for my choice, I found specific Borla headers on the bay, but I'm starting to think it could not be worth the money (more than 500€ for a few hp from what I read). Thank you for the warning about water, I'll consider that although I'm not brave enough (and my car is not ready) to cross streams or rivers at the moment! Have a nice day and a happy new year! Claudio

Thanks for your help, Moses! It's inspiring to see somebody so generous with his time and willful to provide so many informations. Before anything else, I have to say that you were right. I found sources referencing to the Iron Duke, there is some confusion about european jeep engines. Then I found the answer: horsepower was measured until 1990 with DIN system in Europe and "SAE net" in US. That's why my jeep documents (and most of 2.5 tbi wranglers in europe) say it's a 76kw engine. This ultimately confirms that I have the same US engine (117hp SAE net), making the MPI conversion less and less appealing. Here's the reference: http://www.automobile-catalog.com/make/jeep/wrangler_yj/wrangler_yj_hard/1990.html says displacement: 2471 cm3 / 150.8 cui, advertised power: 76 kW / 102 hp ( DIN ), torque: 180 Nm As for my upgrades: My car has no cat (I can legally do that), no "horn" before the air filter, a sport muffler and some other small improvements. As turbocharging here is illegal, I guess I will follow your suggestions and try a cold air intake and a sport exhaust manifold. Thank you again, I hope you will find my information useful too

Thank you Moses, that's very interesting information. I'm afraid I have no major incentive other than power gain, please consider that I cannot legally change displacement (so no 4.0l swap) here in Italy, hence real driving impressions from CasualMechanic would be very valuable to me. Even if the gain was small, the conversion makes other modifications possible (4.0l throttle body, injectors upgrade, ecc), so I'm still uncertain on the way to go. Moses, I hope you excuse me for an off-topic question: around here TBI is 76KW on documents and MPI is 89KW: do you know of any 76kw engine?

Hi Moses and CasualMechanic...Excuse me for "reviving" this old topic, I'm thinking of doing this conversion myself and this forum proved itself one of the most reliable sources of information. My first question is: was the conversion worth it? I understand the distributor has to be swapped in the process, but does changing the flywheel require to change ignition control module and coil too (maybe also crankshaft position sensor)? I didn't find anywhere a good explanation of the amount of components and work required for the entire conversion job, it would be really awesome if you could share your experience about it. Thank you for your time, guys!