st165 to st185 ecu change help

grouch

New member
ok guys i need some help. this is for my uncles st165 alltrac US.
He has swaped the engine out for a second gen 3sgte that he ordered from japan (no egr)
He has been running it on the stock st165 ecu whole time. well we just bought a st185 ecu and plan on hooking it up we need the st165 to st185 harness adapter if anyone know where we can buy it? but i wanted to know what kind of gains we were looking at getting from running the st185 ecu instead of the st165US ecu on the second gen engine. because what i have been reading on threads are people running on first gen 3sgte engine with a st185 ecu setup.
 

Gary ST165

New member
Gains will be very minimal swapping stock ST165 ecu to ST185 ecu on a gen 2 engine. you might be able to run 2 or 3 psi more boost before factory fuel cut

imho, Never worth the hassle. If you want to do an ecu swap > it has to be fully reprogrammable to get any significant gains
 

grouch

New member
Gary ST165":10o67m9b said:
Gains will be very minimal swapping stock ST165 ecu to ST185 ecu on a gen 2 engine. you might be able to run 2 or 3 psi more boost before factory fuel cut

imho, Never worth the hassle. If you want to do an ecu swap > it has to be fully reprogrammable to get any significant gains


thanks gary! to add somemore to my topic that had me questioning and confused is, that the 165 US alltrac is rated around 175HP? and the US st185 is rated at almost 200hp? well since running the stock 165 US ecu on a jdm 2nd gen rated at 225HP. also the new ecu i got according to the part number is the jdm one which some people say has more aggressive timing. so i was thinking that a 225hp engine being managed by a ecu for a 175hp engine might limit the new engines potential.
 

Dracov

Member
I did this myself last year. It felt better but power gains weren't earth-shattering. Nobody really premakes adapter harnesses, though I think DrTweak might as a service. But, for $30 and an afternoon's work you can build your own ECU adapter. There is enough documentation on here to get the part numbers for the plugs and receptacles you need, as well as pinouts.
 

grouch

New member
i just got the st185 connectors in the mail im still looking for the st165 female connector on the ecu so hard to find. i heard first gen dsms and early supra turbos have the same connector as the st165 i might have to check a couple junk yards
 

klue

New member
I can make the adapter harness for you if you want. The gains are measurable, not so much from a performance aspect but more so for driveablility. If your using a gen 2 engine it only makes sense that using the PROPER ecu would make it run/drive better. Definately worth the time or 100-200 bucks for the patch harness. If you use a jdm ecu you will net a few more hp and few more psi of boost. If you can use the gen 2 AFM, map sensor, and TPS
 
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