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J37A4 (320 HP Acura TL 3.7L) swap

25252 Views 112 Replies 8 Participants Last post by  osvaldo516
EDIT- It's been quite the long and winding road, but there's a happy ending! If you don't have time to review 100+ posts, skip to page 6 and digest posts 105 through 109, where I've summarized under the following categories:

Post 105: "NO, you don't REALLY have VTEC on your Pilot!"
Post 106: Build Sheet & Budget
Post 107: Swapped motor control options and wiring
Post 108: Mechanical swap itself, lessons learned & instructions
Post 109: Tuning, end results, and possible way ahead.

Reader's Digest version: I put a 3.7L dual-VTEC Acura TL motor into my 2014 Pilot 4WD Touring. It cost about $7,500 in parts and labor, but could have been done for around $3,000 if I'd done ALL the work myself and not done some of the extra parts upgrades. She makes at least 70 HP and 13 ft-lbs more torque than stock at the crank on 93 octane, and there's probably more still to be had (though I'm not going to go chasing it). It was sometimes frustrating and sometimes fun, but mostly I'm glad it's done and running like it came this way from the factory. GOBS of torque down low, and she'll cruise up a long hill at well above the speed limit in 5th gear without batting an eye.

-------- TL: DR version follows... buckle up, buttercup!--------
Well, the wifemobile (bone stock 2014 AWD Touring) threw a timing belt at 110k, just about 5k miles after having all those components changed with brand new OEM parts. Sheesh.

I'm always looking for an opportunity to make lemons out of lemonade, so since a used 3.7L J37A4 is within a few hundred bucks of a stock 3.5L replacement, let's make simple shit hard and see if we can squeeze a few more ponies out of Princess the Pilot, shall we?

Following a similar swap over on the Ridgeline forums as a guide, it won't be easy but it won't be impossible, either. Mechanically speaking, they're practically identical. EVERYTHING will have to move over from the stock 3.5L, down to the engine mounting points. All accessories and wiring harness. The wiring harness will have to be modified as follows:
1) Injector plugs are different from the 3.7 to the 3.5 so those will have to be moved over from the donor harness.
2) 3.7 has the VTEC solenoid and oil pressure sensor down on the block by the filter as opposed to on the heads like the 3.5, so the harness will have to be extended/modified accordingly.

While we're at it, I'll add a few goodies such as intake manifold spacer & thermal gaskets, throttle body spacer & thermal gaskets, High Flow Pre Cats, equal-length J-pipe, and ported lower intake manifold runners. If Princess has to undergo open heart surgery, we might as well do some touching-up while we're in there, after all!

My biggest concern is CONTROL. Fuel trims are likely to be way off as the 3.5's PCM tries to control an engine with larger displacement and larger injectors than it's expecting. I've got two options: 1) Swap in a Ridgeline PCM, which can be tuned with kTuner, or 2) Try a piggyback ECU (I'm eyeing the AEM F/IC 6). I'm leaning towards the latter.

Anyways, the block is on the way to the installer and all the other ancillary goodies are on order. We expect to start tearing into this around the beginning of September. I'll keep the forum posted, especially considering the dearth of info out there about performance modifications for our beloved Pilots!

-Jon

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Discussion Starter · #81 · (Edited)
Honestly, I'm not planning to change anything aside from upgrading the panel to a K&N. The 09-15 has an upgraded design with a nice snorkel behind the grill pulls in gobs of cool air. Most short ram intakes, well... wouldn't. Plus the stock airbox's outlet is bigger than the TB's inlet, so even though the fresh air path is a bit convoluted, let's all bear in mind that air behaves as an incompressible fluid below Mach 0.3 or so... well above Princess's top speed :)

-Jon
 

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Discussion Starter · #82 ·
Well, the ZDX intake hose is about as good a fit as I could have hoped for. The bigger challenge was actually getting the PCV hard line to fit. Requires some bending/massaging and you definitely need to extend the coolant hoses. Of course, you could just bypass the coolant hoses (designed to warm up the vapors to keep them from condensing) and run a soft line from the IM to the inlet, but I preferred to keep it as stock as possible emissions-wise.

Even on an untuned Pilot PCM, this engine has a TON of grunt down low! I still haven’t fully put my foot to the floor, but a couple of pulls from a roll feel VERY strong in the lower gears. It starts to run out of schlitz around 5k RPM, but once I get the VTEC sorted out, that should take care of that!

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Well, the wifemobile (bone stock 2014 AWD Touring) threw a timing belt at 110k, just about 5k miles after having all those components changed with brand new OEM parts. Sheesh.

I'm always looking for an opportunity to make lemons out of lemonade, so since a used 3.7L J37A4 is within a few hundred bucks of a stock 3.5L replacement, let's make simple shit hard and see if we can squeeze a few more ponies out of Princess the Pilot, shall we?

Following a similar swap over on the Ridgeline forums as a guide, it won't be easy but it won't be impossible, either. Mechanically speaking, they're practically identical. EVERYTHING will have to move over from the stock 3.5L, down to the engine mounting points. All accessories and wiring harness. The wiring harness will have to be modified as follows:
1) Injector plugs are different from the 3.7 to the 3.5 so those will have to be moved over from the donor harness.
2) 3.7 has the VTEC solenoid and oil pressure sensor down on the block by the filter as opposed to on the heads like the 3.5, so the harness will have to be extended/modified accordingly.

While we're at it, I'll add a few goodies such as intake manifold spacer & thermal gaskets, throttle body spacer & thermal gaskets, High Flow Pre Cats, equal-length J-pipe, and ported lower intake manifold runners. If Princess has to undergo open heart surgery, we might as well do some touching-up while we're in there, after all!

My biggest concern is CONTROL. Fuel trims are likely to be way off as the 3.5's PCM tries to control an engine with larger displacement and larger injectors than it's expecting. I've got two options: 1) Swap in a Ridgeline PCM, which can be tuned with kTuner, or 2) Try a piggyback ECU (I'm eyeing the AEM F/IC 6). I'm leaning towards the latter.

Anyways, the block is on the way to the installer and all the other ancillary goodies are on order. We expect to start tearing into this around the beginning of September. I'll keep the forum posted, especially considering the dearth of info out there about performance modifications for our beloved Pilots!

-Jon

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This is awesome. I did a J37 swap on my 2008 TL Type S and it pulled strong.

Did you get to complete the swap? I would seriously consider a 2G if the J37 swap was as straightforward as it was on the Type S.
 

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Discussion Starter · #84 ·
This is awesome. I did a J37 swap on my 2008 TL Type S and it pulled strong.

Did you get to complete the swap? I would seriously consider a 2G if the J37 swap was as straightforward as it was on the Type S.
I did indeed complete the swap. It wasn’t really any harder than replacing one stock 3.5L engine with another. All you need is an extra hour or so to move over injectors and flywheel.

She’s running fantastic. No check engine lights, plenty of power down low... and that’s all on the Pilot computer. I still have yet to plug in the AEM F/IC and start tuning, but even with no tuning and no VTEC, I’m still happy with the low-end torque improvement.
 

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I did indeed complete the swap. It wasn’t really any harder than replacing one stock 3.5L engine with another. All you need is an extra hour or so to move over injectors and flywheel.

She’s running fantastic. No check engine lights, plenty of power down low... and that’s all on the Pilot computer. I still have yet to plug in the AEM F/IC and start tuning, but even with no tuning and no VTEC, I’m still happy with the low-end torque improvement.
That’s awesome man. Any acceleration videos? Would be sweet to see.

The J37 swap was the best mod i ever did to my Type S. It felt almost as quick as my 2015 V6 Accord. The sound and torque were spectacular.
 

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Discussion Starter · #86 ·
That’s awesome man. Any acceleration videos? Would be sweet to see.

The J37 swap was the best mod i ever did to my Type S. It felt almost as quick as my 2015 V6 Accord. The sound and torque were spectacular.
No vids yet... want to at least get the VTEC kicking in before I record any pulls. Maybe sometime in the next few months! Now that she’s back to running with no lights or problems, it’s a bit of a lower priority.
-Jon
 

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Discussion Starter · #87 ·
Update - I've had zero time to futz with the AEM F/IC but Princess continues to run flawlessly and pull very strong at the low end... she's no worse than the stock 3.5L at the top end, and that's WITHOUT VTEC. I'm not going to get around to programming the AEM F/IC anytime soon, but was able to locate a nearby tuning shop that's willing to mess around with it. They've got some availability in mid-January, so I'll drive down there for a day sometime that month for some programming, tuning, and the moment we've all been waiting for... the DYNO PULL :)

Hope everyone has a safe and happy holiday season in the meantime.

-Jon
 

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Update - I've had zero time to futz with the AEM F/IC but Princess continues to run flawlessly and pull very strong at the low end... she's no worse than the stock 3.5L at the top end, and that's WITHOUT VTEC. I'm not going to get around to programming the AEM F/IC anytime soon, but was able to locate a nearby tuning shop that's willing to mess around with it. They've got some availability in mid-January, so I'll drive down there for a day sometime that month for some programming, tuning, and the moment we've all been waiting for... the DYNO PULL :)

Hope everyone has a safe and happy holiday season in the meantime.

-Jon
This is most excellent. I'm excited to see it. Now talk them into figuring out how to swap a manual in too and I'll bring ours down for the swap!
 

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Discussion Starter · #89 · (Edited)
Today is DYNO DAY, folks! I'm here at Turbo Mike Tuning in Charlton, MA. He's got a great reputation, and is one of the only people within a country mile willing to touch an F/IC piggyback. Keep your fingers crossed for Princess today! And yes... that's a dyno in a paint booth (long story short, he leases the space from a body shop and they wouldn't let him remove the booth).

 

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I'm so excited to hear sweet VTEC noises.
 

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Discussion Starter · #91 ·
It’s been a LONG day. Much to write on tomorrow, and some videos to post as well! Long story short, 240 AWHP and 199 FT-LB of torque on a notoriously-conservative Mustang dyno. Assuming 25% drivetrain loss, that’s 320 HP and 266 FT-LB of torque, or 70 more HP and 13 more ft-lb. I’m honestly more pleased with the torque than the HP, because there is just SO much more down low. To truly take this swap to its full potential, we’d have to custom tune the stock PCM to raise the redline and possibly alter the shift points, as the TL motor is rated to 6,700 RPM and shows no signs of gassing out when the Pilot’s PCM makes it shift at 6,300.

Dyno videos, 0-60 videos (runs about a 7.6, BTW), and lessons learned (there were plenty) will be posted tomorrow.

-Jon

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Discussion Starter · #92 · (Edited)

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It's pulling real hard, I bet it really makes the Pilot feel more sporty. The 250hp is sufficient but not much more, my 280 hp Traverse with GDI and a TON more torque spank the Pilot off the line and feels so much stronger.

I also like the subtle 3.7 badge, I'd be the guy who knows behind you wondering whether you knew what you were doing with that badge or not haha.

Are you going to have them do the full fuel trim/timing tables and really eke every bit out of it or are you pretty much done at this point?
 

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After work, I'll post a description of how yesterday went, to include all the lessons learned. For now, though, here's the end results you were all waiting to see!

Baseline Dyno Run (after swap but before tuning... so, no VTEC):

Final Dyno Run (after tuning)

0-60 #1 (uphill grade throughout, A/C off, ~3/4 tank of fuel)

0-60 #2 (flat grade but a short 1-2 shift, still A/C off and 3/4 tank of fuel)
Velly intresting! Sorry I haven't been following along from the beginning but the graph caught my attention. Is that sudden increase in both torque and hp at around 3900 rpm the high rpm VTEC valve timing switchover or something else? Sorry if that's a dumb as hell question. I'm on my way now, backtracking to msg 1 to catch up.

[EDIT] Just read msg #25. So that's what the motor on the end of the intake manifold is for ...... the plot is thickening ... I'm getting dizzy as I get vtech ripped away, maybe get it back, maybe not ... oh v-phooey. Heck with the suspense, I'm going to start reading backards!
 

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Discussion Starter · #95 ·
I also like the subtle 3.7 badge, I'd be the guy who knows behind you wondering whether you knew what you were doing with that badge or not haha.

Are you going to have them do the full fuel trim/timing tables and really eke every bit out of it or are you pretty much done at this point?
LOL, yes, the 3.7L badge was my only concession to the full "sleeper" approach. After some deliberation, I ended up putting the RV6 license plate frames in the trash ;)

I'll put more about this in my "lessons learned about F/IC piggyback tuning" post this evening, but we did make full fuel trim adjustment tables for both in and out of VTEC mode. Didn't need to retard timing, as this isn't a forced-induction application. I don't know that there's much more to be squeezed out of it without doing one or more of three things:
1) Increasing the rev limit. Wouldn't be surprised to see peak wheel HP go up by 10 or so if we could wring her out to the 6700 redline for the 3.7L. This would require tuning the Pilot's PCM.
2) Adjusting the VTEC onset. We played with it a little but had already burned up much of the day dealing with configuration issues w/ the AEM, so I don't know that we TRULY optimized its' engagement. We've got it switching on at 4400 rpm and 80% throttle, which is a little lower than the motor's stock engagement of 4750, but that seems to take advantage of the manifold and TB spacers. Much later was leaving power on the table, and much sooner was starting to conflict with the intake manifold flap opening. This can easily be done with the AEM F/IC, but I think we've got it at a good sweet spot for now.
3) Adjusting the intake manifold flap opening. Currently, the Pilot opens the flaps at 4200 RPM. I think that bringing this earlier would be beneficial, but have no way to do it, as it's controlled by the Pilot's PCM and would require custom tuning. The tuners I've talked to thus far haven't mapped that functionality yet.

Velly intresting! Sorry I haven't been following along from the beginning but the graph caught my attention. Is that sudden increase in both torque and hp at around 3900 rpm the high rpm VTEC valve timing switchover or something else? Sorry if that's a dumb as hell question. I'm on my way now, backtracking to msg 1 to catch up.
Not a dumb as hell question... you've got a lot to catch up on :) The increase around 4000 RPM is due to a few things. First, it's the way the tuner was driving on the dyno in order to avoid a downshift. He didn't really go WOT until reaching those upper RPMs, that's why you don't see a "true" power/torque curve like you'd expect. Second, the intake manifold flaps open at around 4200 RPM. Third, the VTEC engages around 4400 RPM.

-Jon
 

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Discussion Starter · #97 ·
This is awesome!
Can the transmission handle all this additional power?
Gosh, I hope so! My wife is the one who drives it about 90% of the time. Another 8% of the time, I'm the one driving but with her in the car as well. That leaves about 2% of the overall operating window when the vehicle might actually be pushed to its limits. I suppose there will be no way to know for sure unless it starts slipping/failing, which I'll be sure to report here.
 

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Discussion Starter · #98 ·
[EDIT] Just read msg #25. So that's what the motor on the end of the intake manifold is for ...... the plot is thickening ... I'm getting dizzy as I get vtech ripped away, maybe get it back, maybe not ... oh v-phooey. Heck with the suspense, I'm going to start reading backards!
Hahahah! Yeah, it's been quite the roller coaster ride :)
 

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Discussion Starter · #99 · (Edited)
Ok, in case I get struck by a meteor before I have a chance to write all this up, HERE is all you need to program into a properly-wired AEM F/IC6 to have the same tune we just developed.

SETUP:
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The "normal" map (it's actually map "B"... as it turns out, the VTEC oil pressure switch is NC, not NO)
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The "VTEC" map (when the VTEC oil pressure switch opens, the FIC switches to this calibration table instantly)
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Yes, it might seem like there is a lot of resolution "wasted" on the VTEC map, especially, but as the tuner pointed out... if the system is behaving in a relatively linear fashion (more common on N/A motors with mostly-OEM components), you don't need a lot of cells to accurately apply corrections.

Speaking of "properly wiring"... we ended up getting a LOT of the Pilot's sensors that didn't care for being passed through the F/IC, even if no changes were being made to them. If I had to guess, this may have to do with the signal ground I selected (I think I ended up choosing one that was being used by the output shaft speed sensor and the MAP or something). It could have also been that some of these sensors are resistance-based or current-based rather than voltage based as originally suspected. We didn't bother troubleshooting, because in the end, we didn't need ANY of the inputs that were going wonky, so we simply cut and bypassed them. Wish I'd had this info going in, because it would have meant about nine fewer connections that you've got to make for the F/IC (and about five fewer hours at the tuner).

Ultimately, the F/IC is a very powerful tool, reading and controlling analog inputs, logging wideband O2, tweaking MAF values, and so on... but for a "mild" swap like this, NONE of that was needed. Just some massaging to the fuel tables and, of course, the VTEC control. It felt crummy undoing all that work and "un-tapping" the F/IC's potential, but I can't argue with the end result. Here are the revised diagrams. You will no longer make ANY connections to the stock MAF, MAP (the FIC has its own), O2 sensors, or Coolant Temperature Sensor (so much for spoofing the VCM functionality with the FIC). I also admitted to myself that I'd never actually get around to wiring up an oil pressure gauge, so you can drop those wires, too (which further simplifies the piggyback wiring as you are now only dealing with wires in the "B" PCM harness).

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One final lesson learned about the wiring... you need to put a spade connector or a disconnecting switch in line with pin 13 of the 22-pin connector... that's what triggers the AEM F/IC to switch maps when VTEC is, uh, VTECing. The problem is, when the car is off, that switch remains closed/grounded (if you follow my instructions from the install post), so the AEM F/IC software is always set to make changes to map "B". In order to program your VTEC map (map "A") you'll need to disconnect that lead (by way of the switch or by unplugging that spade connector). Once the programming is complete, you reconnect the lead before starting up the car.
 

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This information is so great, I think it would be beneficial for any shared platform to see this (Ridgeline, Odyssey, etc.). Some of them have a different base engine (Ridgeline has VTEC not VCM) but this is a significant upgrade for any of them in the 250 rated hp range. I would suggest posting it on those forums because you've done so much of the technical homework to share your wealth of knowledge.
 
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