RDX10

Hello All,

I just joined a little while ago and am currently in the search for an RDX with tech. I have done some research on SH-AWD and first off WOW this system is so cool:gheywave:

Upon researching (THANK YOU Wikipedia) I have learned that unfortunately the RDX has a 90/10 front/rear power bias under normal conditions but the MDX has a 30/70 front/rear bias under normal conditions. I don't think the MDX has any extra drive-line differences like the RL so shouldn't it be as simple as a program swtich to get the RDX SH-AWD to work like the MDX' system?

Am I missing anything?

Thank you and I look forward to becoming a permanent member on the forum.

justnspace

iTrader: (1)

short answer: no.

TheWrench116

iTrader: (1)

the RL TL and MDX are very similar. The RDX is a completely different animal. it isn't possible to reprogram it because the RDX rear differential is over driven which is how they get the rear outside tire (in a corner) to accelerate and induce power over steer. the system is activated based on driver input and sensor readings by locking a center differential.

KenB350z

Yeah, I think that is all SH-AWD system. That is what makes it differ from all other car manufactures AWD systems.

RDX10

The TL and RDX actually work the same in terms of SH-AWD, while the MDX and RL are direct opposites in terms of the way the power is spread.

All of the SH-AWD systems have the rear wheels over-driven. The only difference is that the RL has a "special device" that makes it overdrive by 5.7% and the others 1.7%.

The way the rear torque vectoring is done, is via 2 multi-plate clutches attached to the rear half shafts attached to the differential, and there is no center differential, it is a viscous coupling or another multi-plate clutch.



Seeing as how the MDX, TL, and RDX don't differ in terms of hardware. It should only be software differences. My question is, if it is not hardware, then it should in effect be very possible to switch them over and if it is not possible, then there must be hardware differences.

Just to clarify, I am not saying that it would be possible for us to do, but is possible for Acura to have done from the factory.

RSXSLVR

Dude where did you get 90/10 power split? It's 70/30 or 30/70 in all sh-awd models including the RDX.

mrgold35

I've notice my 08 RDX is about 50/50 in normal driving and it can get up to 90/10 on hard acceleration. I usually see about 70/30 during moderate acceleration in the RDX. I know the RDX can do 30/70; but, I've never driven in the conditions to make that happen. I've only got about 40%-50% TQ max to the rears to both or one wheel. I don't see a big jump in sh-awd indicator when I hit the corners pretty hard, maybe 1-2 bar more than the opposite tire on the RDX. I haven't notice zero TQ to the opposite rear tire when on a curve compared to the MDX system.

My MDX is super aggressive with the sh-awd. You can really feel the 30/70 when driving up hills. Usually at lower speeds like under 30 mph on very steep hills, normal TQ split at hwy speeds on hills. Most of the time it is closer to the 70/30 to 50/50 range in normal driving. I've seen +80% to one rear tire and 0% to the other rear on very hard turns on the MDX. Even from a low speed right hand turn at a stop sign the MDX sh-awd is 2-3 bars higher than the opposite rear tire compared to the RDX programming.

It would be nice if the RDX could have the same programming or rear bias as the MDX sh-awd (assuming all the hardware is the same).

protoRDX

Wrong.

1) There are 2 different implementations with different torque splits.
2) RDX has 90/10 and up to 30/70 split:

SH-AWD - Wikipedia, the free encyclopedia

RDX10

Thank you!

This is exactly what I am talking about when I mention switching the RDX to MDX specs because they do not work the same way unfortunately.

RDX10

Finally someone else who understands what I am talking about and actually answered my question indirectly with proof!

Very interesting! Thank you for sharing!. I am actually also considering a 2007-2008 MDX but I don't need a vehicle that size, but I really like the looks (call me crazy, I actually really like the front end of the MDX A LOT) and the engine as well as the few extra little goodies. I also like the more aggressive AWD system of the MDX.

I wonder if Acura purposely "detuned" the system for better fuel economy after not achieving what they expected with the 2.3 turbo. I am sure they dumped a heck of a lot of money into designing the 2.3 turbo and were not going to drop it at that point. I am curious if the 2007 RDX is more aggressive in its' SH-AWD specs and Acura decided to reduce its' economy drag in the 2008 year. However I must admit that because I live in the great white north, the 50-50 torque split is more beneficial to me.

The only differences in hardware between all SH-AWD systems as far as I can tell is the "acceleration device" attached to the rear diff of the RL. I don't physically see why it cannot be accomplished if the hardware is the same. It makes me wonder if changing the ECM of the MDX into an RDX would be possible and affect the torque spread.

Off topic: Do you find that the MDX can handle as well or better than the RDX? I want an MDX but it seems that the consensus is that the RDX handles better.

Thank you

mrgold35

I like the sh-awd set-up of the MDX better than the RDX; but, the RDX is my weapon of choice when I want to have some real fun when driving. I have Eibach lowering springs, Hondata+heatshield gasket, Conti DWS tires, lighter rims, and ETS inter-cooler and it makes my RDX a better driver's car with straight line speed, turns, braking and steering compared to my MDX. My MDX Adv is better suited for long hauls with heavy loads with a extra level of smoothness and luxury. Sometimes my MDX is just too large to use as a grocery getter/errands around town (very wide/long vehicle and 360 degree visibility not as good compared to the RDX). The MDX power comes on gradually and later in the RPM band compared to my RDX's turbo that kicks you in the butt with full TQ almost instantly when you floor it; which, I really really like the turbo.

The big girl can still shake her a$$ way better than any other SUV around the same size. It helps the MDX (and RDX) is an unibody car like designs compare to truck body on frame like some SUVs with 7 passenger seating. The 10-13 Advance package (or 07-09 Sport models) have larger front/rear stabilizer bars, magnetic IDS adjustable shocks that aid in braking also, and I added 20" Continental DWS ultra high performance tires with lighter weight rims. Its just physics with the +4600lb top heavy weight and trying to change directions with the MDX. That could be the reason why the sh-awd has to work so hard to stabilize her.

My MDX will not handle as well as my RDX; but, the MDX does a lot of other thing very well to make is a very enjoyable vehicle and better all around vehicle than my RDX.

RDX10

I agree, I like how the SH-AWD is calibrated in the MDX a lot more. Thank you for pointing out the size, the MDX feels huge to me and I was hoping that the SH-AWD would have helped mask that size but it would appear that it does close to nothing about the size. The elite package MDX's here in Canada all have the magnetic ride control stuff which would ideally be my choice if I can find one in the price range.

Excellent point on the fact that the MDX is so much bigger than any other vehicle with SH-AWD, hence it would be calibrated much more aggresively than any other vehicle. Infact, the MDX actually has the best application or best calibration of the system compared to any other vehicle with SH-AWD.

I agree that the MDX is no doubt a better all around vehicle but as you have said, I think the RDX can outhandle the MDX easily, now imagine the RDX was calibrated with the same specs as the MDX! I would assume it would be somewaht possible to do because all the haldex based vehciles have a simple controller that can be replaced, I am certain Acura will have something. I will look into this further once I get my own RDX.

I have no need for an MDX, hell to the no marrying around here and damn to the hell no no kids around here! So I will keep my search strictly to the RDX and Tiguan.

mrgold35

The only other SUVs that might handle very well in the same price range of the MDX is a 07-09 Porsche Cayenne or BMW X5. The Cayenne/X5 are physically slightly larger than the RDX; but, it can have the curb weight of 4700 lbs - 5300 lbs. I've never driven either vehicle and not sure what type of maint problems they might be down the road. Usually, those types of vehicles cost more new and have A LOT of depreciation % wise compared to Acura SUVs of the same year; which, moves them in the same price range in the used market. Unfortunately, if anything breaks, it could cost you a ton of cash to maintain compared to the Acura. A 2007 BMW 4.8L V-8 is about the same price as 2012 RDX sh-awd tech (around $25,000 depending on mileage).

RDX10

You are completely right! The repair costs on the German competition is atrocious. As is the constant need for repairs. German vehicles are top notch in terms of quality, but they are only made to last as long as the 3 year lease that people who can afford them, get.

I guess my only gripe with the RDX is that I want something with a little luxury, my last 2 touaregs and X5 have spoiled me in that regard. The MDX, is a really good compromise I think. It is very reliable and drives pretty well and is luxurious enough. I don't think that the MDX handles NEARLY as well as say an X5M or Porsche cayenne simply due to the virtue of being placed on a RWD vs FWD platform however those 2 couldn't touch the reliability record of the MDX.

I am at the point in my life where I need a reliable car and don't have time to worry about repairs and such. I should go and give an MDX a thorough drive and then decide if I can live with the extra size.