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Discussion Starter · #1 ·
Currently researching and I'm weighing my options between a not-quite as common Honda K-series swap or the tried and true Toyota 3SGE BEAMs swap into a old ae86 chassis I have sitting around. Main reason for considering the K-series is longterm parts sourcing and spares availability.

I'm wondering if the engine harness from any ole K-series can be used or if I have to use one specific to my engine of choice? Example, can I pull a harness from Accord or Element with the K24A4 and use with a K20 or K24A2 engine? I figure I have to cut one up anyways so if I can source a cheaper one and it'll work then may as well try to find a cheaper one.

Ditto on the ECU. I expect I'll move to a standalone at some point but would like to start with a factory ECU to get her running. Is there a way to get around the immobilizer without paying for KTuner/KPro/FlashPro etc? If so, which ECU is recommended? If not, which ECU is recommended?

TIA!
 

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97 civic HX K24a
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Currently researching and I'm weighing my options between a not-quite as common Honda K-series swap or the tried and true Toyota 3SGE BEAMs swap into a old ae86 chassis I have sitting around. Main reason for considering the K-series is longterm parts sourcing and spares availability.

I'm wondering if the engine harness from any ole K-series can be used or if I have to use one specific to my engine of choice? Example, can I pull a harness from Accord or Element with the K24A4 and use with a K20 or K24A2 engine? I figure I have to cut one up anyways so if I can source a cheaper one and it'll work then may as well try to find a cheaper one.

Ditto on the ECU. I expect I'll move to a standalone at some point but would like to start with a factory ECU to get her running. Is there a way to get around the immobilizer without paying for KTuner/KPro/FlashPro etc? If so, which ECU is recommended? If not, which ECU is recommended?

TIA!
02-04 base rsx 5 speed , 02-05 civic si , or the 02-04 rsx type s are your engine harness choices for kpro. For ktuner you could use the k24a4 harness and ecu but many people prefer kpro. For a k20 swap you “can” use the stock computer with immobilizer disabled or a PRC type r ecu but for a k24 it won’t give enough fuel. Also those 2 options are $3-500 so in my opinion it’s better to just save a bit more and get a used kpro
 

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Discussion Starter · #5 ·
02-04 base rsx 5 speed , 02-05 civic si , or the 02-04 rsx type s are your engine harness choices for kpro. For ktuner you could use the k24a4 harness and ecu but many people prefer kpro. For a k20 swap you “can” use the stock computer with immobilizer disabled or a PRC type r ecu but for a k24 it won’t give enough fuel. Also those 2 options are $3-500 so in my opinion it’s better to just save a bit more and get a used kpro
Thanks for the reply! I hear you on the cost/benefit of just moving on up to the KPro, however it looks like the KPro can no longer bypass the immobilizer....?

Has anybody tried bypassing with a remote start? Looking at the wiring, it's possible if you still have the immobilizer unit, and MAY still be possible without the immobilizer.
 

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KPro or Doctronic conversion of the ECU to make it programmable. For most NA, SC or turbo, the programmable converter ed stock ECUs are all the ECU you need to make them run very very well.
Stand Alone ECUs get interesting for ITB conversions or once you need to integrate gearbox controllers for sequential boxes or similar stuff into the ECU’s workings.

With a KPro or Doctronic, you will have a drivable mapping based on the base maps within minutes to a few hours of road tuning. Go fully stand alone and you will spend ages. The combination of adjustable cam advance and switchable cam profiles make a proper mapping non-trivial on a stand alone ECU. And you need to start with one that can actually do this in first place.

If you worry about not being able to afford a KPro or Doctronic update of the stock ECU, I would not start the conversion project.

The KPro and Doctronic for the K20 can disable the immobiliser. The K20a's PRC ECU does not even have one.

Otherwise as said
 

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Discussion Starter · #7 · (Edited)
KPro or Doctronic conversion of the ECU to make it programmable. For most NA, SC or turbo, the programmable converter ed stock ECUs are all the ECU you need to make them run very very well.
Stand Alone ECUs get interesting for ITB conversions or once you need to integrate gearbox controllers for sequential boxes or similar stuff into the ECU’s workings.

With a KPro or Doctronic, you will have a drivable mapping based on the base maps within minutes to a few hours of road tuning. Go fully stand alone and you will spend ages. The combination of adjustable cam advance and switchable cam profiles make a proper mapping non-trivial on a stand alone ECU. And you need to start with one that can actually do this in first place.

If you worry about not being able to afford a KPro or Doctronic update of the stock ECU, I would not start the conversion project.

The KPro and Doctronic for the K20 can disable the immobiliser. The K20a's PRC ECU does not even have one.

Otherwise as said
Thanks for the reply! Cost of upgrading is not the biggest issue, it's getting it running as soon as possible on stock-ish maps without fiddling with tuning. Helps eliminate the ECU/tuning/maps from the equation if there's any initial problems.

I've found a 2005 RSX-S ECU/harness. PRB-A04 ECU which looks like it's on Hondata's list of Kpro-able ECUs. Any reason why this one won't work? Immobilizer different? Honestly, I've been reading up as much as I can on old threads....it gets REALLY confusing if you're not a long term Honda person.

Again, I'm hoping to use the stock ECU to eliminate it as a source of error during initial startup but I'm also trying to keep this initial cost low since I'm fairly sure I'll be moving to a standalone as soon as I can confirm the mechanicals. 02-04 RSX-S harness and ECUs are un-findable or are commanding a significant premium, enough to consider just going with a complete standalone and deal with possible issues later.

Also have my hands on a 2006 TSX K24A2 with harness and ECU. Is there really no way past this Immobilizer issue? How are people doing all these crazy K-series swaps with this stupid immobilizer issue, lol.
 

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Discussion Starter · #8 ·
OK, so it looks like a 02-04 base RSX MT engine harness and ECU can be substituted since I don't care about the 6th gear lockout. Crank sensor may be different.

The 05-06 RSX-S engine harness can be used with a PRB-A0X ECU (typically out of 02-04 RSX-S) but requires some relocation of pins.

This is IF I want to KPro which appears to be a must unless I want to integrate the immobilizer into the system.

To integrate the immobilizer, I'd need the ECU, Immobilizer and key all from the same car.

Correct?

As an aside, this is a major PITA being limited to basically two years of engine harness/ECU. Not sure why Hondata is so popular.
 

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Because the RSX-S/EP3 k20a2 and DC5 K20a from the various Type R cars are plentyfull across the globe, very easy to work with and are good base to upgrade them to a K24 or whatever else. They also come with a very good 6-speed gearbox and you get OE and aftermarket LSDs for them and many options for close ratio sets or stronger gear sets for those 500HP+ buils. You also get sequential gearboxes for the K20/K24 engines.
The Hondata or Doctronic offer programmability and a good set of base maps for NA, SC or turbo application all with the cold start and running manners of the OEM ECU. For a standard engine, the base maps, including the OE map, are good enough to drive around and live with it. You get wideband controller support for narrow band ECUs (PRA in Europe) and factory wideband support for the PRB (USDM) ECUs.
K20, K24, SC, FI, Cams, turbo. All there to start with. Virtually of these maps will start and idle the engine on first crank once you adjusted for the injector size you use, if you installed bigger ones.

They also offer the fuel support of VTC and VTEC. Not many aftermarket standalone ECUs can actually do that. The OEM ECU has 6 ignition and fuel maps for the low cam it interpolates from for the cam angles and then an other 6 maps for the high cam. Same for knock tresholds and other transition parameters. What you get is perfect running matters and enough flexibility to map engines that run on a plenum to perfection. Only once you go ITBs and other extreme things, you run out of options. You cannot adapt the wall wetting model in the Hondata, so for some exotic configurations you might not the get the transition AFRs perfect, mainly for emissions reasons.

If you are into a Motec, EFI, Link, Life of Syvecs ECU, enjoy. Endless possibilities, but you will need countless hours to get it to a point you would start with using a Hondata or Doctronic ECU.
The combination of VTEC and VTC is rather challenging to configure and map to OE levels of perfection.

Some shops offer custom looms for their stand alone ECUs. HPE engineering in UK does one for their Elise conversions using an EFI ECU.
 
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