AEM vs Stock ECU - Honda J35

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wesinls

wesinls

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I scored a brand new AEM for a deal I couldn't pass up...I don't even have the car running yet, and am debating using the AEM or using a stock modified ECU that i purchased from @Kraut_n_Rice.

Motor is stock for now.

Negatives of the AEM that I can see - cost, no ODB 2 port on the AEM. needs to be dyno'd.
Negatives of the stock - untaped power due to being unable to tune? not sure what else.

One positive I've learned with looking at the AEM software - i can configure multiple outputs and turn on my two-radiators fans and two different temps.

What are other pro's and con's with the AEM vs stock?

Anyone have a Honda J35A4 tune for a stock engine they'd share?
 
I am not sure how much more power you will be able to get by switching to the AEM and having it tuned. Maybe 20-30HP, guessing at this point, but would the cost of the ECU and Dyno be worth it? Plus not sure how much more you will make with stock injectors. I remember speaking with Brandon and he said that the OEM ECU does great job in stock form. I think the AEM is only needed when going boosted. With the stock ECU, having an OBD2 port is a nice to have when needed.
 
As Nick said, I doubt you'll see noticeable gains with the AEM over OE in stock form. If your intentions are to stay NA for a while, I'd just run the OE one. Hold on to the AEM for WHEN boost will be added.
 
as dumb as it may sound, just the fact that i can use the AEM to turn on both radiator fans at different temperatures is reason enough to spend the extra money. Cleans up the wiring, cool that i can play with the software, etc. Is that worth the price of a tune, eh, idk.
 
Cleaning up the wiring is enough reason for me to like it.
 
yeah AEM doesnt have OBD and thats an ADVANTAGE as you have FULL ACCESS to everything via laptop, not just some code from OBD.

never mind you can now configure fans, pumps, all sorts of things to do what you want. Never mind you arent locked into OEM sensors or injectors or coils. Never mind you are dealing with a hacked factory harness. Never mind if you want to do upgrades later, an aftermarket ECU will be much easier to deal with.

with all that said. stock is the way to go. :unsure:

the ONLY downside to AEM is they are obsolete. you got lucky and found one. if you spend a bunch of $$ sorting out a new harness, dyno session etc etc and the ecu fails.......you MAY be able to get a replacment but then again maybe not. I dont even know if they will do repairs on them anymore.
 
daveH said:
yeah AEM doesnt have OBD and thats an ADVANTAGE as you have FULL ACCESS to everything via laptop, not just some code from OBD.

never mind you can now configure fans, pumps, all sorts of things to do what you want. Never mind you arent locked into OEM sensors or injectors or coils. Never mind you are dealing with a hacked factory harness. Never mind if you want to do upgrades later, an aftermarket ECU will be much easier to deal with.

with all that said. stock is the way to go. :unsure:

the ONLY downside to AEM is they are obsolete. you got lucky and found one. if you spend a bunch of $$ sorting out a new harness, dyno session etc etc and the ecu fails.......you MAY be able to get a replacment but then again maybe not. I dont even know if they will do repairs on them anymore.
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He's running a bone stock engine. Unless he spends the cash on a custom harness, the mod'd factory one he has is fine with the AEM.
 
Kraut_n_Rice said:
The wiring would ultimatley get more complex with what he is discribing. The harness he has is the bare minimum.
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How so? In reading the AEM documentation- I would just pick an available low side (there's several available)- and use it to trigger a ground to a relay once the coolant temperature is at a certain temp - and rpm's above a certain range - it accomplishes two things I really want - which is, having the ability to turn on my two fans at different temps, and ONLY when engine is running.
 
wesinls said:
How so? In reading the AEM documentation- I would just pick an available low side (there's several available)- and use it to trigger a ground to a relay once the coolant temperature is at a certain temp - and rpm's above a certain range - it accomplishes two things I really want - which is, having the ability to turn on my two fans at different temps, and ONLY when engine is running.
Click to expand...

Your fans are currently controlled by a simple on/off thermo switch that is not wired into the ECU. Fan control is totally external of the ECU. You can control the fans only coming on with the ingition on by wiring the relay coil to ignition power. The thermo switch grounds it in the OE application. If the engine is cold or under the switch temp, they won't run with the ignition on.

You would have to wire differnt outputs to the ECU connectors in the locations designated for individual relays, this equals more wires..
 
Just a thought, since I dont use the OEM water outlet but I did add an aftermarket fan switch, what about using two separate ports with two different temp switches (One for each fan) and use a MSD SSR and use the different inputs. You can also wire the SSR to power on only when the engine is running. Just a thought.
 
ChasingSand said:
Just a thought, since I dont use the OEM water outlet but I did add an aftermarket fan switch, what about using two separate ports with two different temp switches (One for each fan) and use a MSD SSR and use the different inputs. You can also wire the SSR to power on only when the engine is running. Just a thought.
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How are you achieving this? From the instructions, the high current circuits are activated by either a 12vdc+ or - input. There isn't anything typical in the OE set up to do that.

You could wire a normally open pressure switch into the pressurized oil system to close with oil pressure (engine running), and go to ground. Supplying the "G" terminal of the relay. Still have to wire in multiiple temp switches (weld in bungs). Again, more complicated wiring.

At the end of the day, Wyatt can do whatever he wants. If it were me, I would get a new set up to be as simple as possible to get running. Having a JY engine is always a gamble on first crank. Using an engine management system that you know came out of a running car versus an unknown ECU, possibly custom harness... Yeah, give me the one that is more of a given. Work up from there.
 
Kraut_n_Rice said:
How are you achieving this? From the instructions, the high current circuits are activated by either a 12vdc+ or - input. There isn't anything typical in the OE set up to do that.

You could wire a normally open pressure switch into the pressurized oil system to close with oil pressure (engine running), and go to ground. Supplying the "G" terminal of the relay. Still have to wire in multiiple temp switches (weld in bungs). Again, more complicated wiring.

At the end of the day, Wyatt can do whatever he wants. If it were me, I would get a new set up to be as simple as possible to get running. Having a JY engine is always a gamble on first crank. Using an engine management system that you know came out of a running car versus an unknown ECU, possibly custom harness... Yeah, give me the one that is more of a given. Work up from there.
Click to expand...
That was my error, as my SSR is given power once ignition is on, not just the ending running.
 
ChasingSand said:
Just a thought, since I dont use the OEM water outlet but I did add an aftermarket fan switch, what about using two separate ports with two different temp switches (One for each fan) and use a MSD SSR and use the different inputs. You can also wire the SSR to power on only when the engine is running. Just a thought.
Click to expand...
I'm using the P2R water neck and as a result i need to find / make ports for the engine water temp sensor - and the thermal temp switche(s)...the two on the outer are manufactured to give me enough room to drill and tap - one for engine temp and another for a temp switch...So i dont really have room for two seperate temp switches. That's somewhat part of why I'm obsessing about it...i don't like the idea of having both of these taped with wires on both sides and this area is exposed on the car / I want it to look clean as f...most cars all of this is hidden, but for me it's right there in your face.

IF i use the AEM i'd only need to tap one item, the engine temp sensor....yes it's more wires on the AEM as kraut explained, but it's hidden - yes i can put the temp switches in other places other than those two water neck ports, but the inline hose type look like shit, i don't want to have a bung on my radiator., etc

In short - I'm OK with spending the money on the AEM to make it look clean - and also have it installed so when / IF i do engine upgrades, it's already there...i'm just trying to get input from others on if I'm asking for more headaches, less reliable, etc. if going with the AEM. I also like the coolness factor of playing with the tuning software (after someone tunes the engine)...it makes the toy that much more fun for me.

1782347668991.png
 
Kraut_n_Rice said:
The wiring would ultimatley get more complex with what he is discribing. The harness he has is the bare minimum.
Click to expand...
Wiring that gets rid of the relays and fuses would not be more complicated. I assumed that setup would have solid state outputs and/or a PDM.
 
wesinls said:
I'm using the P2R water neck and as a result i need to find / make ports for the engine water temp sensor - and the thermal temp switche(s)...the two on the outer are manufactured to give me enough room to drill and tap - one for engine temp and another for a temp switch...So i dont really have room for two seperate temp switches. That's somewhat part of why I'm obsessing about it...i don't like the idea of having both of these taped with wires on both sides and this area is exposed on the car / I want it to look clean as f...most cars all of this is hidden, but for me it's right there in your face.

IF i use the AEM i'd only need to tap one item, the engine temp sensor....yes it's more wires on the AEM as kraut explained, but it's hidden - yes i can put the temp switches in other places other than those two water neck ports, but the inline hose type look like shit, i don't want to have a bung on my radiator., etc

In short - I'm OK with spending the money on the AEM to make it look clean - and also have it installed so when / IF i do engine upgrades, it's already there...i'm just trying to get input from others on if I'm asking for more headaches, less reliable, etc. if going with the AEM. I also like the coolness factor of playing with the tuning software (after someone tunes the engine)...it makes the toy that much more fun for me.

View attachment 189224
Click to expand...
you might have a stock engine, but i wouldnt hesitate to put an aftermarket ECU on it. Why? becasue it opens up a world of possibilties.

first, you are locked into stock whatever. want to get rid of headaches with sand in your throttle cable? fine, go drive by wire. want to add a turbo later on, fine change injectors and map sensor and you are in business. fan control issues? not with an open system where you can have staged fans controlled via relays or even better speed controlled fans by an aftermarket ECU.

second, you now have full access to all engine parameters. want to throw e85 in it with a flex fuel sensor? easy peasy. want to change rev limiter or have built in wide band to see what going on? slam dunk. want logging? done. have an issue? break out the laptop and plug in for total access and testing.

third, i would build my own harness and not throw some 20 year old thing in there that who knows what sort of gremlins it may or may not have.

fourth, want to add a dash display and get rid of all the gauges, extra sending units and wiring and so forth? yep....an aftermarket ECU gives you that.
 
daveH said:
you might have a stock engine, but i wouldnt hesitate to put an aftermarket ECU on it. Why? becasue it opens up a world of possibilties.

first, you are locked into stock whatever. want to get rid of headaches with sand in your throttle cable? fine, go drive by wire. want to add a turbo later on, fine change injectors and map sensor and you are in business. fan control issues? not with an open system where you can have staged fans controlled via relays or even better speed controlled fans by an aftermarket ECU.

second, you now have full access to all engine parameters. want to throw e85 in it with a flex fuel sensor? easy peasy. want to change rev limiter or have built in wide band to see what going on? slam dunk. want logging? done. have an issue? break out the laptop and plug in for total access and testing.

third, i would build my own harness and not throw some 20 year old thing in there that who knows what sort of gremlins it may or may not have.

fourth, want to add a dash display and get rid of all the gauges, extra sending units and wiring and so forth? yep....an aftermarket ECU gives you that.
Click to expand...
All of that stuff is cool, but keep in mind a couple of things:

The AEM will plug into the same harness as the stock computer, so swapping between the 2 is trivial.

Changing rev limit, E85, tune, etc on a stock J35 isn’t gaining anything. There really isn’t any need to log anything, monitor wide bands, etc, with a stock J with a stock ECU. It was designed for soccer moms to just start and go. I doubt you’ll get the stock engine’s 11 gajillion throttle maps, etc that make it run so well.

You can add an AEM CD-5 dash to almost any OBD2 ECU with CANBUS output.


This isn’t a custom LS with a super chop cam and turbo. This is a stock J35 with some bolt on mods. Save the custom ECM tuning for when it’s needed, because while you might squeeze another couple hp out of it, you’ll give up a little of that “I push start, it starts” aspect.

And if someone thinks they’re getting OE-level maps from a $500 tune session… No. You’re not.
 
At least this thread has shown that's it's not a surprise I'm debating which direction to go - reliable OEM, or future proof AEM...seems 50/50.
 
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