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Discussion Starter #541
2019 Resto 1.7: Tensioner Pulley

While replacing the thermostat, my mechanic found out the tensioner pulley did not spin smoothly. By luck, one of the mysteries was solved. This is the root cause of the increased engine vibration I have been experiencing since December.

Symptoms

- Idle vibration with a distinctively repetitive pattern.
- Noisy engine.
- A little lag in engine response when blipping throttle.

The idle vibration is now as smooth as when the engine mounts were replaced. The engine also revs more easily since obviously there is less friction.

I changed the rear passenger hub as well, and together with the new tensioner pulley the car glides noticeable longer when off-throttle in D. The rear end also feels more stable, so I assume the rear hub did need changing.

The car certainly runs better, I felt like it gained 10hp. But not all is well. I *STILL* hear bearing noise, so there might still be something. But I am happy to be back on the right track, fixing real issues and keeping the car in good shape.

One thing is for sure, the restoration/repair is certainly not done yet. There is another episode brewing about the whistle noise from the brake booster area……

EDIT: Actually the wheel noise seems louder after the Timken rear hub replacement lol
I will just enjoy the new-found smoothness for now.
 

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Discussion Starter #542
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Discussion Starter #543
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Discussion Starter #544
2019 Resto 1.8: New Brake Booster + Check Valve Workaround



Symptoms


  • Intermittent whistle noise from brake booster at idle after pressing the brake pedal about 80%+ deep.
  • Noise goes away, or change its tune, with any throttle or brake pedal input.
  • Booster does not keep vaccum overnight.
  • Rpm drops by about 50-100rpm when pressing the brake pedal all the way in at idle.
  • Brake sometimes feels spongy and less powerful in the 80-100% brake pedal travel.

The issue was pretty obvious in the booster-check valve. The old check valve passed the simple blow test, but because oem booster is pricey my mechanic tried replacing the check valve first. The oem vaccum tube/check valve assembly was on backorder with no ETA, so he used his 300ZX check valve to connect as a replacement. The inlet/outlet diameter happened to match TSX's vaccum tube.



Brake felt better after the new check valve and the whistle noise was harder to re-produce, but the noise still occurred a few times. So a new booster was installed.

The brake feels much more progressive after the new booster - the pedal travel required to achieve the same brake power seems to increase by 2x. I am not sure I like it, but at least I no longer need to worry about the brake not working when I need it most.
 

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Discussion Starter #545
What’s wrong with Acura logistics lately?

TSX brake booster hose on backorder, fine, since the part does not fail often.

Current-gen MDX windshield on backorder with no ETA? Unbelievable...
 

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Discussion Starter #546
2019 Resto 1.9: Front-Left Shock Absorber Went Bad

Symptoms

- Weak low speed damping. The driver-side rocks, as if the car only rides on spring.
- Noticeable difference in damping response when pushing the car down by hand.
- Area below the top cap/seal is a little wet.

Most likely something went wrong with the MSV (micro-speed valve), because otherwise the shock still responds well to damping force adjustment, and the damping feels OK for larger/sharper bumps.

You might ask why not buy a new set of coilovers? I thought about switching to ST, but the kit is not readily available, and need to be shipped from Europe. The kit also needs top mounts, and I don’t know wether to go Type-S bushing or not. All considered, rebuilding CST makes sense to me - it costs less, takes about the same time, and with a known outcome.

My CST shocks were re-valved in 2015, so seem earlier to go bad. But then I drove the car very hard in 1st half of 2018, and put crazy load on the front left corner. So actually this episode is not a surprise to me. Besides, the constant small vibrations may also wear out the shock one way or another.
 

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Discussion Starter #548
Around $150 I think. Rebuild is just $120.
 

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Discussion Starter #549
RDX A-Spec SH-AWD

This one has to be a longer read....

With CST front shocks sent back to Tein for inspection/overhaul, the oem front coilovers were called into duty after many years of sleeping. I was curious how the wheel noise would respond to the change, and unfortunately the noise and vibration got significantly worse with the soft oem suspension. I am now inclined to believe the issue is either in the bushings or axle. Not able to identify the root cause quickly, I feel like the car is destroying itself if I continue running it as a daily.

I have to find out the source of the problem, but in a less time-pressured way. That means taking TSX out of daily duty.

The car is too close to my heart to say goodbye now, so the question I asked was, which car compliments TSX the best?

Long story short, after Model 3 was vetoed, M340 feels too excessive/purposeful, and 330 feels good but not great, I stayed in the Acura family and got myself a RDX A-Spec.

For those of you in the market for RDX, my deal was 4.8k off MSRP, including the $1k loyalty credit. Maybe there is more room, because apparently A-Spec models with red seats do not sell well in Bay Area. All A-Spec on the lot were made in 11/2018, and mostly blue color. In comparison, RDX average day-to-sell is 40-50.

My car has high mileage for a new one, but somehow, the powertrain feels smoother than the almost-new RDX I tried before. Maybe just the nature of break-in. The power flows with NA engine response, the AT mostly works behind the scene. Now I understand why the powertrain, especially the engine, is praised.

A few standout items that nudged me towards RDX instead of 330:
- Audio system is killer, punches way way above its class. BMW's "Hi-Fi" system might as well be branded Lo-Fi.
- Excellent storage.
- The car has traditional Honda/Acura virtues, but now feels like BMW- instead of just Honda+.
- Feels like I get more car for similar or slightly less money.

Things I like about RDX so far:
- Audio, yes I know have praised it, but on RDX this really is studio-level sound stage and precision.
- It seems like my FlashPro can be re-used on RDX!
- Ventilated seats!
- Pano roof! But apparently it does not have safety film…
- K20C seems to be as powerful as J35, when the 10AT is in the right gear and when in turbo.
- The car feels balanced, and good enough for everything. Other than brakes, I do not feel like I need to have Type-S for commuting and shuttling kids.
- The tail is responsive, and follows the front surprising well. The front grip feels not great, though I haven’t pushed the car hard enough yet to see if it is suspension tuning or just tires.
- I like the TrueTouch interface more than I thought I would, and the infotainment manages to hide it’s slower speed well with smooth UI transition.
- This is a happy car, but I do not know how to explain it other than say it is easygoing.

Things I do not like:
- Tire noise with the 20” A-Spec tire is loud for a new generation car…
- The LCD screen in the instrument panel is not good. Small texts are pixelated, and the info is placed too low. Acura decided the upper area is reserved for ACC, LKAS, and boost/g meters, and I do not understand why.
- The computer for Infotainment already feels under-powered. Infotainment also has a few bugs.
- Voice recognition is clearly based on Alexa, but is quite slow, like the connection is on 56kbps, and with mixed result. Address is fine, but saying place names rarely work, even though I can find those places using search on the infotainment.
- The A-spec seats are not as comfortable as they should be.
- Even though steering and handling feel good, the chassis feedback feel more synthetic and computerized than 3G MDX.
- Brake is useable, but a bit vague and non-linear. This is probably where Type-S is going to see a significant improvement by using fixed calipers. In fact, I believe the reason A-aspec uses 20” 255 tires is because those will be used by Type-S. So I am hopeful that Type-S caliper/rotor can be dropped into A-spec.
- Other than audio and interior, the car is still not at tier-1 level. For example, chassis stiffness feels less than 330, ride quality is missing the well-damped feeling in the initial response, and in-car tech is at least one generation behind BMW. But then I am getting BMW- for the price of Honda+, so not much to complain really.
 

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Discussion Starter #551
Congrats on your new RDX!
There is no perfect car... That is why we build them ourselves 😉

Thanks. That is so true isn’t it.
 

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Discussion Starter #552
3G RDX vs 1G TSX

Having been rotating between the two cars, I feel they are an interesting combo to have. They are like two flavors of the same everyday meal.

Powertrain

No doubt the RDX is a lot more powerful low-mid range when boosted. The short gearing further spices up the power level. However, there are a few issues.

First is consistency. Mixing in the turbo and 10AT, I am never sure how much power I will get at WOT. When everything works together, there is more than enough torque for daily driving. But other times, power either is not as strong as expected, or comes with a varying level of delay.

Some of it comes from turbo lag, and ironically, some from the short gearing. I find I need to downshift at least two gears to get enough power when cruising at highway speed. There are really too many gears to handle manually, and I wish Acura copy BMW in that the AT will automatically downshift enough gears with one pull of the paddle shifter.

One thing obvious to me is Honda tried to smooth out power delivery of this powertrain, and I feel part of the delayed response is a result of that.

Second issue is the top-end is quite a bit weaker than the mid-range. To me, the strongest power band is between 2.5-5k. Beyond 5k, I would say RDX does not feel as powerful as my TSX. This is understandable, as the torque of RDX drops after 4k, while TSX holds its torque from 4k all the way to 7k.

The RDX powertrain does not shy away from using the whole rev range when being asked, so not having the same urgency up top is a pity.

Lastly, the throttle response. It is a bit sticky in comfort mode, better in Sport mode, and close to my TSX in Sports+. For whatever reason, the throttle response is crispier with the CMBS (auto-brake) system disabled. If I had known about this, I might hesitate buying RDX, because I really like the response without CMBS, but disabling a safety feature to get that is like going backwards.

Handling

Maybe I am asking too much, but RDX by default has too little turn-in grip in the front. Any kind of quick turn-in, and front end just does not keep up. The tires give up just when the fun is about to begin, and produce huge understeer. Switching dynamic mode to Sport+ helps mitigate the understeer significantly (I believe through brake-torquing the front), but the handling is still far from natural.

However, once in a turn, the tires then provide a lot of lateral grip. So I would say the tires are to be blamed, as they need babying to gradually build up grip. But I do see a lot of room for a more aggressive suspension setup, maybe more camber up front and stiffer rear springs/swaybar, to improve turn-in and speed up rotation. Maybe Type-S will bring those and more.

In comparison, my TSX feels lightening quick in turn-in response. It would be Sport 2.5+ on the RDX. The best thing of all is, the response is linear and predictable all the way through a corner.

SH-AWD

Compared to the 2nd-gen SH-AWD in MDX, I find the response time of torque vectoring much improved on the 4th-gen unit. There is significantly less lag between throttle input and dynamic change. The increased rear torque bias is also obvious, as RDX drives more RWD-ish.

SH-AWD really helps RDX match, if not excel, my TSX in terms of powering through a corner. However, my biggest issue with SH-AWD is still the same - I find it hard to navigate the grip limit of a car with SH-AWD.

Unless pushing to the absolute edge of grip limit on both ends, SH-AWD is always able to balance the car. So the limit seems to be changing all the time. I sometimes feel like I am a passenger of SH-AWD....

In comparison, TSX is straightforward and welcoming. It invites me to explore the limit, and guides me with consistent feedback. So once I get there, I know where the limit and thus I learn to control how much grip to use.

The interactions are what makes TSX special, and why driving it is rewarding.

Brakes

I complained about the brakes, and later learned about a TSB available for my RDX that re-programs the electric brake booster to improve brake feel. But over time, I feel the brake is decent, and actually has good stopping power. Maybe due to the wide 255 tires, I find the ABS does not kick in easily, which is a good thing.

My RDX does tend to have brake squeals when the brake is cold. This seems to be a known issue, but does not bother me considering how much squealing the RB kit did on my TSX...

Fuel Economy

This is where RDX falls below its promise. My TSX was about 19-21 MPG. RDX so far is about 18-20 MPG, and that is with lean driving unless otherwise necessary. For reference, the EPA estimation is 21 MPG city.

Funnily, the MPG I get improves with clearer throttle response. That means my MPG is better in Sport mode, and better with CMBS disabled.

Sport+ keeps rev above 2k to spool up turbo, and maybe uses other anti-lag tricks, and does impact MPG slightly.

Build quality

The build quality of my RDX could be better.

From the factory, the difference was probably <2mm, but once I noticed it I could not un-see it. The right-rear door also is not flush with the top portion of the rear quarter panel. These are not as obvious as some Tesla panel mis-alignments, but still noticeable.


My TSX has zero mis-alignments, and the panel gap is consistent throughout, except for the trunk lid which seems to be raised slightly towards the rear.


Overall


I like the simplicity and directness of my TSX, everything just works in harmony.


RDX is a good car, but I do not love it because I feel I need to constantly adjust the car's settings (dynamic mode/idle auto stop/CMBS) to suit different scenarios. I wish RDX has a customized mode, where I can have the VSA always in Sport+, steering in Sport+, throttle mid-way between Sport and Sport+, transmission to Sport, and an option to disable idle stop by default. Adding in some rough edges in the infotainment, sometimes I feel like RDX is a little bit un-finished.


But I have seen the driving dynamic of MDX changing drastically with a SW update of the various control modules. So hopefully, Acura can do the magic again and have a better calibration in the future...
 
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