Head swap for KB1 2005 RL
 

Hello acurazine!

I recently bought a 2005 acura RL because I wanted a car that had awd because let's be honest, winters are pretty fucking terrible in non awd or 4x4 vehicles. Beside the point, I understand that this car isnt gonna be super fast or anything and many of the mods have been discontinued. Also there isnt really anyway to tune these cars either...

BUT. After looking around for possible mods and finding incomplete answers I was wondering a few things.

I saw that in theory the j37a2/j37a4 dual sohc vtec heads "should " fit our j35a8 engines. The coolant passages line up and the vtec is still controlled by a single solenoid. Is this correct? I would assume use the matching gasket with the head?

Also, one of the most common upgrades seem to be j37 intake/tb swap. Does this matter which j37x? Or is this specific?

And finally. How good is our ecu at adjusting with said mods above? I know there are a bunch of guys at vp6 who have had good results with stock ecu adjusting with mods and was wondering if the RL is the same? Obviously different engines and ecus.

hoping to get MAYBE 20more hp as its quick but I'm feeling if it had a little hit more umph. It's a great looking car but a poor performance platform lol. I still love it though.

From what I have read, the stock ECU doesn't handle too much go fast mods. Maybe an exhaust + intake. But once you start swapping the heads + intake manifold/TB, might be a bit much for the stock ECU.

I hope not lol but chances are I may attempt anyways because now these heads are relatively "cheap" vs a couple of years ago. There isnt a lot of info on things like the cam profile and flow but I saw yungone had suggested that this is the best flowing head over the j37 a1 and j35a8 head. Might be the Guinea pig for this just hoping for some more info advice.

definitely doing intake/exhaust though.

The car is a beast on snow, and.... not fast??

hmmmm.... Damn car's a rocket... It depends on your expectations i suppose. You thinking Indy500?

nope. Love the sarcasm though. I just wished it pulled a little harder. I know the 5AT isnt as good as the KB2 6AT or the j35a8 as good as the j37a2. Just looking for a good median between cost and power. Most people are saying the same things.

I got this car cheap, paid in cash vs my first one that I had a loan on. So I'm not really afraid to blow it up especially with summer rolling around. I'll be driving my civic most days then.

if it blows up. It blows up. Then I'll probably just buy junkyard j35a8 and keep it stock. But I'm just looking for as much info as possible. Doesnt make sense to do something someone has done and didnt find success. With no tuning options not a lot of people have dont I/H/E mods. I think I've seen 2 people on here with j37 intake/tb and a few with exhaust.

one guy was saying he swapped the internals of the j35a8 with j37 rods/crank but no proof. No dyno. And to me sounds like a nightmare with no tuning.

when I say fast I mean "fast" in the summer or dry surfaces lol. This tank is a mid 15 car on a good day. I'd hope to maybe lose 1 second.

it also wont be tracked though. Just speaking in terms of "speed".

i swapped J37 MDX heads on my 3.2l base TL and LOST power...without tuning; there's too much air flow.

oh man. This totally makes me sad. Where do we get more power?! Pooowwwaah

trade in your RL and buy a GT-R for AWD or CTS-V for RWD.

Considering that 300hp is now almost a norm for a good nice sedan, in 2005-2008 this engine power was definitely above average, lux category, etc... definitely changed over the years bud...
If you want the power and to have AWD, look at Q50 Red Sport... or BMW X3 M40i if you want more space and crossover like vehicle... yeah these are all in 50k range (X3 is 55k and up I believe) - but that is where Acura was...

With both Red Sport and M401 X3 you get 4.5-4.6sec to 60mph and awd - which is very fast... both of these are not 2-door cars, so you get that family needs aspect as well...
X3 M40i is definitely too expensive for my budget, while Q50 I am not sure of their reliability - 2016 version had issues with drive/serpentine belt slipping off causing issues and some damage...

Couple of other vehicles I forgot is BMW 340i xdrive or Audi S4 ... these also have great performance specs - but of course, cost much much more than our RLs :)

the cost is more is right lol. You do pay what you get. I was just looking for maybe a bit more power so it could be a bit more sporty. I bought this car for 2k to be my "winter beater" and bad weather condition car. Plus it helps that I have already worked on this car and am familiar with its quirks. Theres just something though about that SHAWD. I've driven some other AWD cars and it's not quite the same, especially how the RL handles. My fiance drives our MDX and you can definitely tell how the car is tuned to drive. The MDX seems to swing wide and pull you around last second. It feels very FWD dominant in corners while with the RL feels very RWD like because the back always swings around. It's a funky sensation feeling the back AND front pull you around a corner. In fact the SHAWD has almost caused me to die many times because i had to learn that I didnt need as much counter steer because it goes where you steer.

Not looking for too much power but really hoping to get in that 4th gen TL SHAWD range. If I recall correctly they are mid 14 second cars? While almost as heavy as our 2nd gen RLs they have 305/275 vs our 286/256.

20 more ponies. Any idea if upgrading injectors will mess with our ecu? All those guys at vp6 and their accords have Frankensteined everything swapping out intakes, injectors, headers, ecus, etc. For what it's worth I'm probably just gonna have to be a Guinea pig. I gave myself 5k to spend on this car and I found one cheap, so logic says that I have 3k set aside for mods lmao.

and yeah, I know I know, if I want fast I should have bought another car, but most of us RL owners bought the car because we love the car :)

didnt even look at the 09+. Not the best looking imo lol

i never posted my dyno cuz i was too embarrassed that I lost power. lol
went from 241wheel horsepower to 214 wheel horse power.

it's only worthwhile if you can tune...

after I got the 3.7l heads on, I rushed, resulting in user error and bricking the block.
I opted to replace the whole engine with a stock 3.2l engine and since then have gotten tuned.

I want to try again with the 3.7l MDX heads...because this time, I can tune it

do you think there is a possibility you lost power because the head chamber is bigger than the stock j32 head? 27WHP is a ton of power to lose. That might not be it though because i think all the j3x heads have the same chamber size and dont have clearance problems. But it's only 1mm. Lots of people have done that without that power loss.

I dont know if having a bigger engine, 3.5 vs 3.2 will make a difference either.

Perhaps user error installing the heads. I suck lol

lol. You live and you learn. I saw that the coolant passages line up pretty well with this 2nd gen j35s. I dont think anyone has done it so I'm the Guinea pig here. This will be my first j engine I've worked on so pray for me haha

it looks good on paper but we all know how that turns out. Just waiting till thisbdamn winter ends! I need sunny days in my life then junkyard time

justonjack has spoken.

lol. Yep. U'll get sarcasm from me alright.

I have a kb2. vtech on intake added in this MMC, gave it a boost to 300 HP and 3.7 liter engine. All this is stock. My tranny is 5 speed. Only as of second half of 2011 did they become 6speed.

It is rare for a car to compete with me on the road. A 4.5 liter engine pickup truck humiliated me, but hey, he's probably half my weight. we're at 2 tons with the RL.

I dunno how much you planning to spend, but this may interest you: https://acurazine.com/forums/second-...%2A%2A-751361/

And if you know how to do the work yourself, you may find a used kit for under a grand.

I'm pretty good with my hands and I understand how a supercharger works but I've never worked with them so I'm pretty much a noob. I'm at work right now and just skimming through real fast it looks like all he did was add the comptech supercharger.

I'm not sure how though he managed to only "apply" 2.5 lbs of boost though because he said there was no tuning done snd that the stock ECU itself compensates. I'm sure though I'm gonna need to buy a pretty legit battery though because these RLs eat batteries like no tomorrow and everytime I would change it out it would reset the ECU lmao. That would just be my luck.

but this is exactly what I've been looking for. Just a modest increase in power to make everyday driving a little better.

what other parts other than the super charger is in this "kit"? Do you think I'll have to source parts independently or will I find one in a kit?

my budget is probably around 3k. I'll want to do the labor myself. I'm definitely doing things like light weight pulley, lighter rims, exhaust.

No clue there. Zero experience.

I don't know if this info is useful for that, but I can tell you that everytime I've disconnected the batter to replace something electrical, or when i changed the battery, I had to put in the GPS code again, and the radio code, and all the settings like the screen color, audio notifications (or not - not in my case), GPS settings, radio presets, etc etc.. all become reset like factory. And, then, a few park and re-starts like drop by a shop, then a supermarket, etc. it all somehow comes back every single time, every setting come back on it's own just like it was. even MID settings.

Again no clue. A little online search will probably give you an idea. But, if i recall someone saying 2 yrs back on here that Honda & Acura mods were the hardest to find.. and indeed, check this out: https://www.jegs.com/c/Fuel-Carbs-In...10327/10002/-1 they got for many even toyota, (it changes by year), but nothing honda. You gotta do some research.

I think that's about how much the guy in Cali said Comptech charged him. But i read online they changed ownership. Follow the trail. you may be able to buy the kit or some components from them.

I'm surprised he's even helping in the RL section.

even though there are a lot of questions you dont have answers to thanks for the info! I saw that the OP from the s/c thread said it was originally a comptech S/C kit for the 3rd gen TL. So I'll just have to look and see what original components came with that kit and find it myself. Most likely I'll have to piece it together myself but that's pretty much all you do with a turbo kit. Find deals on pieces and then put it together. I'm thinking if the supercharger is anything like a turbo system there must be some sort or relief valve like a blow off valve or waste gate. These are usually rated at a certain PSI and I'm thinking I just got to do some digging.

never thought I'd see the day where I'd turn to the dark side and look at superchargers

You know you never mentioned what mileage is on the car and it's general condition, etc. - coz you did mention you got it at a low price.

the car is in great condition and is mechanically sound. But. It has a million miles on it. Actual number is 192k.

My other RL that I totalled 2 months ago had 150k on the odometer but did not feel as good as this car. Throttle response and pull feel MUCH stronger in this car. Why? No idea. The other car was maintained well and they're the same year.

I know it's a lot of miles and it's not recommended for boost with HIGH high mileage but it's not my summer DD. If I blow it up I'll figure something out. Either replace the motor and keep it stock or keep on playing who knows 😉

I'm actually right now looking for what kind of supercharger was used in those TL kits. Seems like the idea is to run a smaller than normal S/C with an overdriven or underdrive pulley. Still in the process of figuring it out lol.

Might just go and ask the TL part of this forum because the answers seem to be far and in between and there isnt like anywhere you could just buy this from. Though, superchargers "seem" rather affordable on first glance.

my biggest issue is how to control that boost which seems right now without engine management is restricting the size of the blower and making sure the pulley ratios line up to where I wont make a lot of boost.

I imagine it like running a super small turbo that cant make big numbers. The problem though still would be heat.

This is what the CT, which I'm assuming is comptech website provided. The OP in the RL s/c thread along with the shop said they didnt use the ACM and kept it stock ecu. Skimming through the TL supercharger threads here some people are claiming the AMC is garbage. But still got lots of research to do.

Kit fits both Automatic and 6-Speed 04-08 Acura TL.

Uses an Eaton MP62 gen5 like older kit but has a shorter drive snout than earlier TL/CL/Accord kits.


Boost is 4-5 psi. Gains for Auto are approximately 60hp; 6-Speed is approximately 65hp @ the wheels.


Blower does have signature whine when in boost above 4,000RPM.

Kit includes everything to bolt on, except the new battery. Customer needs to buy Interstate MT 51R or equivalent battery. This battery is physically smaller but has better spec’s than the stock battery.


Kit will come with CT Engineering's new ACM (Advanced Control Module) to add fuel in boost, lower VTEC (RPM to 4000 from 4800), and clamp MAP sensor voltage (@3.0 volts). ACM will come with jumper harness for the majority of its connections, but you will have to cut and solder 4 wires.

CARB approved through 2008.

Belt follows stock belt path, and kit comes with a longer belt to reach the blower. It uses the stock automatic adjusting belt tensioner. To change the belt you will have disconnect the P/S feed hose.

Does not require a fuel pump change.

Customer will need to trim radiator fan shroud, as well as engine bay plastic. Instructions include trim templates to perform this operation. Does not require customer to send in fan shroud like earlier model kits.

Kit comes with longer battery cables for new battery location.

Kit comes with Intake Kit (tube, filter and brackets). It does not have an Air-Box like the older Kits. It mounts the filter in the side of the engine bay allows engine to breath colder air from outside the engine bay.

Kit may fit on 03-07 V6 Accords with modifications. No tech support or warranty is included when fitting to the Accord.

Do you have the car's history?

All these mods will get you 20-35 maybe even 60HP. I'd not know. .... BUT

You were talking about increasing the car's umph... have you check when was the last time it's sensors were changed? maybe try a good engine flush, make sure plugs are still good, coz in these cars, you may still have the stock ones. Check and see if the cat converter is doing well or is it clogging a bit? does it need cleaning? anything in the suspension almost gone and weighing down on the car.. etc.

I recently only changed a miserable O2 sensor, and a whole lotta umph came back.

Coz this 3.5 liter of urs, with the vtech and nervous 5 speed, should be having quite the umph for a regular - untracked - DD.

You may benefit more, either way, restoring and making sure it's running to specs, before trying and boosting it's adrenaline.

The car that was slower was my old RL that I hit a deer with.

I do not have the cars history but the guy I bought it from we hit it off right away. I usually dont trust guys who mod cars, because most guys dont do it right, but this guy seemed super on my wave length.

Hes a Honda guy and this was his DD. He said he was selling it becaus wanted a pick up truck and he wasnt greedy on the price. I actually got to see his garage as he didnt expect me to buy it right away. He had a huge garage with more tools than even I have. Big air compressor and a HUGE tool box that was probably worth more than his house lmfao. It's funny because we pulled up and I was like, oh, a an RSX type S and hes like, that's my girlfriends lol.

what I do know is that he said he changed out the O2 sensors and I can verify this because it looks brand new. Still super shiny and the wires are clean. I checked the spark plugs and all the fluids and everything checked out. I would have done a compression test but didnt feel the need to because after I bought this car me and the fiance had a race on the highway.

08 MDX vs 05 RL from 60-100 or so and I was able to pull her by almost a car length. I honestly thought I would lose because I was like 190k. Probably lost some power along the way but I was pleasantly surprised.

compared to my old RL the transmission seems to be much better. My old RL had what we called a "quirk" where if you smashed the gas sometimes it would completely miss gear and then catch gear on it's way down. It would jerk your head and make a bad sound lmfao. But this car seems to have a super responsive throttle. Touch the gas and it pulls you forward. So far so good.

I like the umph I just want maybe a little bit more. Plus it would be pretty cool to be unique. If I could get the 20-30whp from N/A mods I would probably do that over a S/C but theres about the same amount of info for both. Like none lol. I honestly think one person a piece.

part of me feels like if the RL can adjust for S/C then it should 100% be able to adjust with j37a1 or even the j37a2/4 heads which if it was successful should put up decent numbers. Some guy I read here got like 13-18whp I think he said from Intake/exhaust mods? But the dunk was all screwy because of the shawd. I got some money to spend but I dont want throwing it into a pit. It's not a racecar, just a spirited driving DD lol.

Decisions decisions decisions.