dueces

Hey guys, i dont post much, because frankly, i currently dont have a honda!

I have a question about modifying the rear diff for those that might have some knowlege on the subject.

I cant find any good info on the actual system, but all i hear is how the rear diff uses a fluid transfering system to activate the rear diff.

My question is, has anyone modified this system to put more power to the rear end quicker? If its a fluid transfer system i would assume opening up the oriface that sends the fluid rearward could possibly allow the rear end to come online sooner and stronger to aid in traction.

Anyone have any knowledge on the subject? Or even better, some tech specs or pictures of the inner workings of this system?

Thanks guys,

John

el crapitan

here is a decent article on honda's dual pump system complete with exploded views:
http://www.awdwiki.com/en/honda/

dueces

Wow, Thanks! I'll take a close look at that when I get home from work. I would like to see the rear end get fully locked pretty close to the first sign of slipage from the front diff, hopefully it's possible.

Looking at the 390whp thread, the launch doesn't look that impressive, and no one answered my question there about whether they feel the AWD system helped with launching.

John

el crapitan

apparently, once a 3% difference is felt between the front and rear wheels, lock up occurs

dueces

Really? I have a friend that tried to spin the tires in his crv on wet pavement, and he said the fronts were squealing the entire time. I guess that is to be expected, but I would imagine it would almost be like reverse ABS. Everything I have read states that it is a progressive system, and that the more the front tires spin, the more engagement(torque) is sent to the rear end.

OneBadTurboCRV

I am curious. If you don't own one why are you so interested? Since you seem to want to bash this setup so much I'll leave you with this...

There are exploded views avaible on dealership websites. It's a simplistic system and operates somewhat like an automatic transmission. This has been covered before in build threads - there are ways to increase the transfer; shimming being one of them. If you have enough power you will hear the system whine under pressure - typically this takes around 300whp+ (depending on condition of the system) to experience this from acceleration alone . Start getting towards 450-500whp and the system is at its limit - whining constantly. It's not designed for "launching" but rather acceleration traction. The help is after the launch... I think you are confused with a true AWD vehicle system. (This of course is from my personal experiences; others can feel free to comment.)

OneBadTurboCRV

Also, don't focus on the rear differential too much and maybe you will understand how the system actually works... regardless take a look at this video. The vehicle's drivetrain is made of both styles of the RT4WD system...

http://youtu.be/vxkuJmNEGq4

dueces

Who said I am bashing? I am trying to gain knowledge on the subject because I will be using this system for my own project, which will not be a honda, but honda powered.

The only reason I am not doing the civic wagovan rear is because I DO like the way this system works. I am trying to get info on how well this system will perform at the track, that's why I am asking others for their input. I have owned an Evo and currently have a A4 quattro and a Subaru Legacy, so I know a decent amount about awd vehicles, I just want to make sure this system can achieve the traction I need, if not I will be using the Wagovan rear....

John

el crapitan

yes. a difference in hydraulic pressure between the front pump and rear pump force engagement of the rear diff's clutch. the greater the difference, the more force is applied to the clutch. similar to how a torque convertor operates.

possibly there was an issue with your friends system. maybe worn clutches? maybe the rears lost traction as well? i'd find that hard to believe though being on wet pavement.
it is a fairly simple system though, much like most honda engineering.

el crapitan

IMO though, this system was designed for light duty. i'm sure there are ways of fortifying it though. hopefully someone with more knowledge, from a performance aspect, will chyme in for you

dueces

The application I am using this on will be "lighter" duty, and I know it will hold up to some decent amount of abuse, but it will be a car that I take to the track, I just don't want 2.0+ 60' times.... My Evo would pull consistant 1.6 60' and it was not very modified, the best it did was low 12's. If this system doesn't react the way I want it to, I am interested in knowing if I can modify it to make it suit better for off the line traction.

John

I also questioned my buddy about his CRV and told him he might want to check into if there is something wrong with his, since he said it just spun the front tires...

Scotty Dosent Know

Is his CR-V AWD?? lol Because not all of them are.

The Chazzer

you're a joke...the dude is just asking questions.

I am pretty disappointed by the rear-traction in the snow thus-far...which is the reason why I bought this thing. I can feel it engaging when it's REALLY needed. I might be biased because I drove an XJ all last winter...but I knew it would be vastly different.

I'm probably gonna get the diff fluid flushed soon and see if that helps any.

dueces

Ha Ha Ha, I asked him the same thing! It is AWD, and it makes sense why you would hear it, because you have to spin the fronts before the rear will be engaged, I just want it to come on sooner and harder...

OneBadTurboCRV

I am a joke? Interesting theory - I have read all your posts and I see you haven't added anything to this forum thus far. Half of his posts talk down upon the system... As stated before the system can be tailored to ones needs. In stock form it's not the best due to the nature it's engaged - that's why it's called Real Time 4WD and not something like Full Time. If you even half-way understand how an automatic transmission works you know what to do to upgrade the systems to suit your needs. Keep in mind it is no variable transfer... Check out "fast2camciv"s build thread. He somewhat shows what and how he did stuff. I wish I would have done a write-up when I did the modifications to my '98 long ago. Then again I kind of like keeping things to myself because of kids like you.

dueces

I really hope your not refering to me as a 'kid', and please show me where i am talking down this system. i have stated that i want it to come online quicker, for my application. you only mentioned there being ways to modify it. thanks for the name to search, i will. but just because i dont know automatic transmissions doesnt mean i am a damn kid, i am here to gain info, not be bashed because you interpret my questions as personal attacts towards this system, which once again i AM NOT doing. everytime people fill a post with off subject crap it makes it more difficult for people like me to do actual searches and find difinitive answers for the questions i need answered.

John

The Chazzer

x2
since he quoted me I'm pretty sure he got butthurt and had to insult me.

I'd also like you to show me where I "talk down" the setup. Anything I have said in other threads is to bring people's heads out of the clouds and back to reality about what these CARS are for.
If being realistic about the capability of what I drive makes me down on it.........

Thanks for the help in my thread...but there's no reason to bash this guy for his questions. Being so defensive about something so stupid really is funny. And you're calling ME a kid. LMAO. Far from it brother.

OneBadTurboCRV

You guys should read a little more in depth of what is typed to see who was being referred to and when. The last two posts filled this thread with more garbage than anything that came before... Anyways back on topic - I honestly think with out knowing what exactly your build plans are there won't be much in the direction of true help. The viscous coupler can't exactly be modified anywhere near as much as the pump system. I am not sure if you actually looked into that car's setup of the video posted. If not, here is the website...

http://www.epictuning.com/4wdcivic.html

(All I am getting at is it does help to search... All this information is readily available.)

dueces

I dont just want AWD, I want the car to cruise and drive like a front wheel drive car around town and on the highway, so I can keep awesome gas mileage. I want the AWD for the winter and for the track. Epics car, which I already know about, uses the Wagovan rear so it is awd all the time. If I am forced to go that way I will, but I am hoping I can get the RT4WD to work that is in the CRV, so I don't have to mix and match all sorts of stuff, it will make a swap that much easier as I will have all the components in one donor vehicle.

My build is planned to be around 300-350WHP, and either b18 or b20, whatever I can get ahold of for a reasonable price, and it will be turboed, My assumption is that I will be using Hondata, but I am familiar with MegaSquirt so I might go that route as well.

I have been looking for more definitive answers on how to modify the hydraulic system, but my search skills must not be up to the standards I guess.

OneBadTurboCRV

What you just described is exactly how the CR-V RT4WD system works... The stock driveline will handle this flawlessly. It's been holding up for years in my daily driven 450whp CR-V...

dueces

Have you launched the car at the track? Granted the setup's will be different(mine will be a car with a total weight of around 2200lbs), but if you had any 60' times that would help.

I am leaning towards the info my buddy gave me as his crv having issues, maybe worn out clutches, etc.

If it will net me good 60'times that would be awesome!

I looked at "fast2camciv"s thread on where he modified the spacing in the clutches, and he said he thinks the system is coming on faster with that modification, that might be the way I have to go if the stock setup isn't what I want.

Also, You cant say I don't own one anymore, just got the wife a '10 ! ha ha

John

OneBadTurboCRV

Hah... No, sorry I haven't had it to the track. This is just my daily driver - I have it because it gets around 30mpg, has the power when I need it, traction if I need it, cruise, power steering, A/C, ect (I think you get the idea). Although, enough people keep pestering me to take it to the track, I just haven't had any interest. I can tell you it "smokes" a Trail Blazer SS in all areas, then again they only run low 14's / high 13's stock. Still nothing to brag about, but I tend not to full out launch from a stop anyways. Too afraid the 2-step building boost could shatter something. So I guess I should rephrase the above - its held up well to light spirited driving.

Maybe "fast2camciv" can tell you as he has been to some tracks (not sure if drag is included). Also, I think his goal is to build it to beat the **** out of it with around my horsepower. He may be a better person to talk to - then again you aren't "building" a CR-V.

fast2camciv

^^ I would like to see you beat up on your crv just to see what kind of issues you run into (just dont hit me up for a paypal donation when something breaks haha )

In my build thread there is a link to an album on my photobucket...there are numerous pictures of a TCD unit all tore down so you can sort of get an idea how it all works. i've also posted the hydraulic schematic so you can see how it controls the different "modes". but i'll break it down semi-simple for conversations sake. (not NEARLY enough info online about Honda's rt4wd system....and almost NOTHING online about how to modify it for performance oriented folks)

engine turns differential in transmission.
differential has 2 ring gears. 1 ring gear drives the front wheels, 2nd ring gear powers the propeller shaft.
propeller shaft attaches to "TCD" unit. (tcd unit is comprised of a set of clutches, and 2 hydraulic pumps)
front prop shaft drives 1 pump, rear pinion drives the other pump.
when 1 pump spins faster than the other, it builds pressure, and pushes/pulls on a plate inside the tcd, which in turn pushes a set of clutch discs together. it engages or disengages the clutches depending on which pump is spinning faster.
normal driving means both pumps are pumping close to equal pressure
condition where front tires spin, makes the front pump engage the clutches until the rear pump equalizes the pressure (rear tires catch up to front tire speed)
once the rear tires catch up, the clutches disengage (because back pump pressure vs front pump pressure are equal)


there is a LOT more to it, because Honda engineered it to work differently under different conditions. But its 100% mechanical in its engagement. YES there is the possibility to modify this system to transfer more tq to the rear, and possibly the speed in which it reacts. the bad news is, nobody has figured it out yet...and there is a very small handfull of people actually messing around with the system. (most people swap out the TCD unit for a wagon Viscous Coupler and wagon rear end...beware there is gear ratio differences when doing this, and they need to be solved with running different tire diameters front to back.) I have messed around with shims (really didnt do much, if anything at all) and i've heavily pondered tapping into the case, and oil galleys, in order to route the fluid out of the case, through some type of controller (manual or electronic), and then back into the case to control the plate that engages the clutches. Unfortunately I just havent had the time in the last couple months to do much R&D on that. myself, 88ed8, soxle, rallysol, and purplecivicturbo have all messed around with the system, and between us, can answer just about any rt4wd related questions. I think 88ed8 and myself and more recently purplecivicturbo, are the only ones interested in making the crv's tcd unit better. like I said before, most people just opt to use the wagons driveline/rear end instead.

I have a rt4wd 5spd crv with a built 2.0 liter ls/vtec thats soon to be boosted, and the goal is about 450whp. I also have a 93 civic coupe that i'm converting to rt4wd, and will eventually try to emulate epic tuning's 10 second beast (im realistically, another year or so away from completing that car, as the crv is my focus at teh moment)

Hope that answers some of your questions....if not, ask away

dueces

Hey, thanks for that good quick right up/explanation! i did check out your thread and a lot of your pictures, and it all makes sense to me, and i am sure i will be one of the few that does try to modify it as well. personally though, my build is probaby 6mo to a year out, as i have one other project car to finish up, as well as an entire kitchen....

when i get more time to look at this stuff more carefully i am sure i will be sending pm's your way, ha ha. thanks again,

john

fast2camciv

^^ I hear ya...I too have too many projects and not enough time haha.

the major issue with the crv rear end is that it will never truly "lock up" and give an equal 50/50 split. For my CRV I really dont NEED a 50/50 split...a 60/40 or 70/30 will probably be enough traction to do what I want. (I want to have the worlds quickest/fastest CRV) But for my "race car" (civic) I want a 50/50 split, and I want it to engage fast. for that car, I'm going with the crv rear end (to avoid gear ratio problems) and doing 88ed8's "big axle conversion" (covered in his build thread) and then welding up the TCD unit and removing the clutches....so to control the tq going to the rear, i will be fabricating a custom driveline and using a viscous coupler from the wagon. the VC reacts fast, and achieves a full 50/50 lock up. If i cant get the TCD unit to behave in a reasonable manner...I will put a VC in the crv as well. Hopefully I dont have to.