Roen

iTrader: (2)

the problem is a good DTSS system is expensive......to the tune of $1200

jackhild59

iTrader: (7)

Yeah, I paid $1100 for mine.

BUT, it had a free RX7 Convertible attached.

phoenix7

I like the DTSS. Once you get used to the feeling of it you know to counter and you're back. If you're gonna go to drifting events where the SOLE PURPOSE is to make the car BREAK the rear end loose then you won't like it. If you're into gripping the roadcourse to the limit then DTSS is for you. If you suffer from snap oversteer then you should:

A) fix/replace your DTSS

B) learn to drive the 7

Roen

iTrader: (2)

Hmm.....would I trade a stock vert for a mint, brand new, DTSS hub? Sure, since I already have 2 FC's.

Asterisk

iTrader: (3)

Well, I dont know... but my plans are:

Remove DTSS & install eliminator bushings
learn to drive,
learn to drift properly
install the DTSS again
learn to use it properly.

If I dont like it, take it back off, it's that simple!

Roen

iTrader: (2)

your DTSS bushings might be too shot to even want to put back in....and that's the problem.

Not enough supply of replacement DTSS bushings.

Asterisk

iTrader: (3)

I meant new ones..

raptor22

Does anyone know why noone has made a replacement DTSS bushing yet? It can't be too expensive to make, and they could probably get away with a rediculous markup over cost with the hub costing a good $150+ from mazda.

$75-$80 a bushing would still save a good amount of money, and is probably still be many times what the bushing costs to reproduce.

--Alex

rxtuner79

iTrader: (1)

Group buy, anyone?

Roen

iTrader: (2)

You have $1200 for new DTSS stuff?

I don't know where you guys got that the hub is $150....It's $600 PER SIDE.

ajsuper7

rx7racer has it spot on, i couldnt agree more. after driving these cars for nearly 10 years ive learned to live with dtss and understand the 'dangers' of it. i love dtss in daily driving but i will never push my car 9/10ths are more on the street because its just too damn unpredictable. on a track i suppose id get used to it but on the street there are too many factors including bumps and potholes. these are amazing cars even by todays standards but please be careful.

0verb00st

I want to learn how to take full advantage of this system. What was it originally intended for? Increasing grip and handling? What is responsible for the sudden snap and can I take advantage of the snap to or should I avoid it?

TweakGames

iTrader: (3)

It was intended for a REALLY good driver to make nice "EASY" gental inputs into the car. If you are a very smooth driver, don't jerk the wheel, or have any quick actions, you CAN take the corners faster. Now while your in the corner and your going fast enough and smooth enough to take advantage of the DTSS and you hit a bump/pot hole or you realise that your going to wide and try to cut in again (or do anything to throw off the a nice smooth gforce curve) your instantly sideway, (or the car will rock back and forth) then you try to correct and the DTSS makes it very hard to impossible for you to recover smoothly. The DTSS IS a great idea ..... for a good driver, on a track environment (and that is the only place is SHOULD be used anyways!) You should not be driving fast enough to cause the g-forces on any public roads.

I got rid of my DTSS, and I will with EVERY second gen I get. You do lose the rx7 feeling though when the car is less *** out ... (is ..that good way to describe it?) haha It just feels like you are pulling a kid on a sled behind you when you have DTSS causing it to pull the rear out when in a corner. It feels like your rear is more planted and predictable without it. And I prefer that.

Hope that helps!

GTU power!

phoenix7

what you gain in driftability you lose in STABILITY at low speeds. Not only does it help toe out at higher lateral Gs (like mark said 0.5 or higher) but it helps for low speed (read STREET) driving and stomp on the brake stability.

It actually helps get around faster. When you push the car past the limit you tend to slide sideways. Good DTSS will shift the rear end out (which is where the driver should be experienced enough to counter and stablize the car with the throttle). You'll be at the apex of the turn and can accelerate out of it.

Good DTSS fishtails when you step on the brake when you should be on the gas.

rx7racerca

iTrader: (1)

The short answer is, DTSS is Mazda's marketing name for the passive rear steering system on FC RX-7s, and there's little to do to take advantage of it, beyond making sure you have a good alignment (4 wheel) and the bushings aren't shot, it's just there. It will work nicely for you, as long as you don't try to drive the car to the limit, which on the streets you certainly should not do (see my retard comment earlier . The handling limits of the FC, and a lot of modern cars, are high enough that probing them on the streets is stupid, period. Acquiring my FC many years ago is what got me into autocross and track competition, since I finally had a car whose limits were well beyond what was stupid to do on the streets. Keep it somewhat sane on the streets, and all you have to do is enjoy the agility and responsiveness of your FC.

Long answer (sorry, and I do mean long): DTSS is a system intended by Mazda to overcome the problems inherent in semi-trailing arm independent rear suspension (without actually going to a better design, like unequal-length double-A arms or other multi-link setups, such as on the FD, which have their own compromises in terms of packaging and expense). Those problems are camber change under compression/extension and increasing toe-out under compression, both of which ultimately lead to snap oversteer. In a large part, the system succeeds in dealing with that under all but the most extreme conditions. It is also, like many passive (the FC RX-7 and Porsche 928) and active 4-wheel steering systems of the 80's (optionally on Mazda's own MX6, Honda Prelude, Nissan 240SX and 300ZX), intended to enhance the driver's sense of responsiveness, and basically be smarter than the driver, in terms of avoiding driver stupidity leading to spins or other loss of control. Now most manufacturers have turned to better suspension geometry (on serious sports cars) and/or traction control nannies to enhance safety and grip.

DTSS does this in two ways (I'm summarizing Jack Yamaguchi's technical analysis from the November '85 Road & Track, as well as some of my own suspension knowledge and experience). Mazda added what is called the camber-control link (the inner arm of the "y" formed by the trailing arm), the geometry of which is designed to virtually eliminate camber change under compression. Straight forward enough there, as extreme camber gain, leading to loss of contact patch, is part of why semi-trailing arm suspensions are known for snap oversteer.

The second element, which is both tricky in the sense of clever engineering, and in the sense of tricking skilled drivers attempting to drive at the limit, involves toe control, though what's called the "floating hub". This is where the DTSS bushings come in. The hub has three connection points to the trailing arm, the 2 rear-most of which form an axis which allows the hub to rotate the wheel/tire thu a small range of toe-in (rear wheels track slightly towards the centreline of the car) to toe out, through controlled deformation of the forward-most link, the DTSS bushing at the lower front of the hub. Under braking or acceleration, the geometry and deflection are such that the hub will rotate to slight toe in, which is a good thing, as it promotes stability and keeping the rear end behind the front. Again, keep in mind that traditional semi-trailing arms tend to behave oppositely under acceleration and braking(both in toe in and toe out, and camber gain/loss). So this is a big improvement, maintaining the more stable toe-in configuration under both conditions, rather than suddenly changing from one to the other as one does when going from acceleration to braking, and vice-versa (which happens a lot racing ).

The floating hub and DTSS bushing also allow changing toe control under cornering, changing from slight toe out below ~.5g, thru neutral at ~.5g (assuming your rear alignment is correct), and increasing to progessively more toe-in at higher cornering loads, which is inherently more stable. At below .5g (most cornering and lane changes in street driving), the slight toe-out enhances the sensation of responsiveness. Note, this is more of a sensation, as what happens is the rear tires describe a slightly larger arc than what they would otherwise, but begin building slip angle sooner rather than lagging very slightly behind the fronts which initiate the turn.This communicates to the driver as enhanced agility or responsiveness, but would be inherently unsafe at higher cornering loads, because the rear tires are trying to describe a larger arc than what they should - which is the beginning of a a spin if not corrected. Transitioning to toe in at higher loads means mild but safe, predictable understeer at higher cornering speeds, while at lower speeds/loads. the driver gets to feel a sensation of near instant responsiveness to steering inputs.

So far, this all sounds good, so why do I and most FC racers, and a good number of other people get rid of the DTSS bushings, even if they're not shot? First, if they are shot, it is some $1,200 to get a pair of replacement hubs from Mazda, which is the only way to get replacement DTSS bushings - just too much for most to spend on cars at or approaching 20 years old. If they're shot, your car will handle unpredictably at ALL speeds. So for many it's just a practical consideration - too much money for too little gain, especially since it doesn't really affect objective handling numbers, more just perceived agility - which is nevertheless a great part of the RX-7 experience.

However, for driving right at the limit, be it an autocross course or track event, the toe control changes are unpredictable - which translates to sudden, unexpected, and uncorrectable oversteer - a snap spin. Which is why if the class they are in allows it, competition drivers ditch the DTSS bushings. Ditching mine and moving to a higher class came before I even got the coilovers and race springs (although not much), after years of competition in stock classes. Without the DTSS bushing (and mine are in fine shape), the car immediately became easier to drive hard.

Automotive magazines of the time are full of comparisons to the Porsche 944, which Mazda publicly cited as their target, a car which in the regular tests - acceleration, skidpad g's, slalom, braking - the RX-7 equaled or exceeded the Porsche's numbers. But put the cars on the track together, and the RX-7 would lag a couple or more seconds behind per lap - a lot, and a big reason why the FC never became the force it's numbers said it should be in SCCA SS (showroom stock) or stock-class autocrossing at the time. The reviews are full of phrases like "too much drama", "too unpredictable", "doesn't work well at the limit". My experience parallels that. The problem is, when driving at the limit of adhesion, no matter how smooth the driver is (and I, for one, am noted as an exceptionally smooth driver), there is no such thing as a truly "steady state" turn. There are always minor adjustments of steering and throttle, as well as the fact any track surface has small bumps, irregularities, cracks, sand and tire marbles, etc. DTSS is constantly making small toe changes as grip changes, as well as cornering loads induced by steering and thottle.

At the limit of adhesion, the outside rear tire (in this case) is really alternating between a high slip angle (slip angle doesn't mean drifting, this is the technical term for the tire's behavior, any tire cornering at any speed), and actually sliding, where traction is lost. Normally, a good driver in a good, communicative chassis senses these changes and balances the car with steering and throttle inputs. With DTSS, the rear suspension itself is trying to "fix" things with it's own toe changes, partially masking from the driver what is going on at the contact patch, and which side of the high slip-angle/slide equation the tire is on.

Moreover, the suspension can get it's fixes wrong. At the limit, as the tire transitions from adhesion/high slip angle, to outright sliding (which is a loss of grip, and therefore load, it also changes the load on the bushing - causing the outside rear to give up toe-in just when it really needs it to prevent an incipient slide turning to a spin. Combine this with the fact the driver's response is (and has to be) to counter steer to correct the spin, further decreasing load, and the rear suspension can transition to toe out - the very worst thing for controlling a slide. This can happen so fast, both the car and the driver are just along for the ride, hoping there's no marshals, curbs, berms, etc coming at them in the rear view. In autocrossing, where the speeds are lower but the same principles apply, I usually turned the spins into a full 360 by grabbing 1st and powering the rest of the way around - a smoky, entertaining conclusion to a blown run, but not the winning way around. As an aside, active 4-wheel steering systems didn't have this particular problem, because they relied on lateral acceleration sensors, not tire load on the bushings. They did tend to mask driver feedback from the car however, hence why, combined with their complexity and expense, they haven't caught on.

Now, here's the thing. I notice NO loss of agility (or the perception thereof) without DTSS with my street alignment. I don't have my log book handy, but I run as much negative camber and castor as possible at the front. Only about -.5*negative camber, even with the coilovers and race springs, as I don't have camber plates (another reason the RX-7 never really shone in stock classes - really limited camber adjustment stock). Aim for that if your not completing in a stock class that requires no enlarging of the strut mounting holes, etc. The current setup works surprisingly well street and track. For the street, I run 1/16" total toe-out at the front, which probably accounts for the perceived agility. If you live in an area with badly truck-rutted roads, zero front toe may be better to avoid "tramlining" in the ruts. Normal street alignments usually feature slight toe in at the front, which also enhances stability, but breeds understeer and lethargic steering response. For competition, I increase the front to 1/8" to 3/16" total toe-out, depending on the course and anticipated speeds (more for slower, tighter courses). The rear I just check periodically to make sure it hasn't changed - so I'm not as sure off the top of my head, but I believe it is 1/16" or 1/8" total toe in. This equates to a slightly loose setup, which is just how I happen to like the car,(probably comes from all those years spinning the car!), so slightly more may increase stabilty, at the expense of agility. Much more than 3/16 toe-in might mean increased wear on the inside edge of the rears, so I hesitate to suggest that, and haven't tried it besides.

I hope that, at the expense of being wordy, this offers sufficient accuracy and detail compared to some previous posts. If not, the thread should probably die and be forgotten, because there's been plenty of misinformation here.

staticguitar313

iTrader: (2)

^ best info evar!

what i want to know is how much of that wonderful feeling you lose during daily spirited driving? i dont want my fc to become boring.

0verb00st

Thanks for the info!

RockLobster

iTrader: (7)

IMNSHO FC owners that have not taken their car to the track on a regular basis will never experience the ill effects of the DTSS and should general leave their system alone.

It does provide a certain cornering stability for "spirited driving".

But the last 3 paragraphs of the long post above hit it on the head, and if you track your car with R-comp tires and have become good enough to consistantly have the car at the limit of tire grip, you just know how the DTSS gives a vauge and inconsistant feedback. I would characterize it as inconsistant except for one consitant component, a "tight" or "understeer" feeling when the car isnt necessarily tight. The thing is the feeling changes as you corner.

The people that tout the benifits of the DTSS are not wrong, they just dont drive thier cars in a racing level environment on a closed course and if they do, they arent driving near the limit of the car's capabilites on r-comp tires.

The statment about it causing snap oversteer is not wrong, sort of. The drawback of the DTSS does not lie in CAUSING oversteer, it actually does the oposite. What it does do is greatly exhasorbate the effect of oversteer WHEN high adhesion tires DO break loose. That is why it gets characterized as "causing" snap oversteer.

You cannot have consistantly fast lap times when the car becomes a horrible mess to recover durring a "step out".

The biggest way to experience the difference i have found is simulating a mid turn check up while closely following another race car on the track. (I say simulate because it is so scarry i wouldnt try it with the DTSS not dissabled for fear of causing a wreck EVER AGAIN, believe me once was enough). Drive and FC mid session (tires and brakes at optimum temp) through a corner at max cornering speed and quickly take your foot of the gas and just EVER so slightly tap the brake. The car feals like you broke something in the rear suspension and wants to SNAP oversteer. Do the same exersize once the system is eliminated and it is far less of a dramatic shift in control.

RockLobster

iTrader: (7)

This is far and above THE BEST description of THE NO.1 WORST characteristic of the DTSS system for track drivers. It is EXACTLY what made me get rid of mine and EXACTLY how i would describe this specific characteristic.

I would add that an FC with eliminated DTSS (all else being equal) will certainly be a much "looser" car and want to oversteer much more than with it, after you get more experience with the car WITHOUT the DTSS you learn how to set the car up to compensate and the cars handling actually improves over what was ever possible with the DTSS. Thus for most guys it is one inital step back to take two or three steps forward in the long run.

RockLobster

iTrader: (7)

I dont know why people say it feals this way. And i have heard this before. But what you are describing is exactly the oposite of what is ACTUALLY happening with and without DTSS.

The basic snap oversteer feeling people get from it is BECAUSE the car feels tight under high cornering loads right up until the rear tires break lose, then it becomse the loosest car in history. I would guess this is why it is a must for drifters to defeat the system because it is working against what you are trying to acomplish right up until you DO acomplish it, then it goes the other way and makes the drift totally uncontrollable.

TweakGames

iTrader: (3)

bottom line dtss sucks haha jk jk I hate it but thats just me.

djmtsu

iTrader: (3)

I love it.

DTSS FTMFW!!!!

It is handy at the Tail of the Dragon.