purpose of torque dip
 

The more I drive this car the more I realize how much thought was put into the engineering. Lately I find myself on empty twisty canyon roads skiing around. I realized that, at times, the torque dip might be useful. It seems to provide extra fidelity in the throttle which is nice at the limits of ashesion. If I am in the upper power band coming up on a turn and let off gas and begin turn. As the weight shifts and I hear the car say yes you may wag my tail I agree. And I find that in the "dip" is a perfect range of power to add more overseer or back off.


But because of the dip in torque it seems like that range of power is ideal for an extremely light car at the limits of adhesion. It doesn't need much at the limit and I believe this car is so well engineered that may have been thought out. rather than just some terrible thing someone overlooked.


Or maybe I'm in love with a girl with glasses

The prupose is MPG. I find driving in the dip is harder myself. No response from the go peddle when you need it.

You may be in love with a girl with glasses...a hot, skanky one...

The dip in torque between 3500~4500 rpm wasn't something they engineered in because they thought it was a good idea or would add to the fun. It's (likely) there in order for the car to meet emissions and possibly fuel economy requirements. I like girls with glasses. But I don't find this one particularly likeable.

There had to be a reason they tuned it that way aside from efficiency. I mean the SAE articles and testing from Subaru show DI/Port injection maps with the TQ dip there. They knew it was there and left it.

I have heard so many reasons why and how, but still am not convinced.

My guess would be for emission reasons.

Nice theory OP.

In reality the purpose is to piss me off!

To mimic VTEC, but at 5,000 RPM instead of 7,000 RPM?

Implying the torque dip was engineered to be there is silly. I'm sure they knew it was there but I believe that getting rid of it would cause some other compromise the team would dislike even more

SWP, I originally suspected that may be the reason too. In MotoGP, the crossplane crankshaft was designed to give the engine short breaks in power in order to retain more grip when power sliding. However, this is isn't the same sort of thing and the car doesn't have much power to begin with. They'd be better off giving it more grippy tires to compensate for a little more power if that were the case. I'm pretty sure the dip was just a compromise. I just hope they get rid of it for next year.

Come on, guys. I don't really get everyone complaining about the torque dip all the time. The problem is easily resolved by downshifting. Sure, the dip is there. But no 2.0 liter 4cyl I am aware of makes any significant torque at lower rpms without FI. The VTECs mentioned above aren't any different. My Prelude VTEC didn't have any significant low end torque, either. Whether or not it had a dip in a nearly non-existent amount of torque wasn't really relevant to me. I just rev'ed it out from 5,000 to 7100 in each gear... and it moved along nicely. In fact, the numbers showed it was a quick from 60-120 as a Mustang GT.

Seems to me that everyone basically has 5 options:

1: Use the power and torque where it exists - which is 5000+;
2: Get a tune (which broadens the spread significantly);
3: Get FI;
4: Get a larger motor and/or a Camaro/Mustang;
5: Get a header (with a tune).

If you didn't want to shift a lot, then you probably shoulda had a V8. ;)

But that's not exactly correct. I think this engine is very torquey down low. Especially for a normally aspirated 2.0 liter. Around 2500 RPM it's actually pretty strong and surprisingly punchy. In fact, I don't think I've ever driven a car with a non F.I. engine this small, with so much bottom end torque on tap. The problem is that the torque falls off significantly around 3500 rpm. And that's why it's so noticeable.

Couldn't agree more... it's a classic engineering compromise.

I agree with robwbright. Drive the car in the higher RPM's if you don't like the feel of the torque dip, or just downshift. Seems easy enough to me.

Absolutely! It wasn't "engineered in", it was something they were unable to "engineer out".

Uh, no. The more linear the power delivery is, the easier it is to control the car. I owned (and loved!) an MR2 turbo for many years, but even a small increase in throttle would suddenly spool the turbo up to full boost. At 15 psi, that's almost likely doubling the engines output...not a good thing unless your pointed straight ahead.

Try driving anything from 20-25 years ago. Then you'll learn to love your powerful FR-Z engine.

That was never going to happen for a car designed to be the drift successor to the AE86. Plus the mileage and fun from the low rolling resistance tires is hella fun if you don't look at a stopwatch.


That said, I gobbled up and then buried an S2000 in my rearview mirror yesterday on Ortega Hwy so the torque dip and shitty tires aren't bothering me too much. I'd take a far better cup holder and proper cargo net first tbh. Anyone know what a 44oz drink launched 80mph into the center console of an FRS looks like? I do....

Agreed. But it's still nothing like a V8 or even a 6.

Which brings us to the other issue. Would you rather it have less torque down low so you wouldn't notice the dip as much?

I have no idea why the motor produces torque the way it does, but maybe they did people a solid by making sure it had a decent amount of torque down low and they just couldn't figure out a way to continue that torque curve thru the low-mid range without other tradeoffs such as expense or reliability or whatever...

There's still significantly more power and torque up high, so it doesn't really make sense to be trying to accelerate at 3500 rpm anyway.

I'd prefer the car have a reasonable amount more torque and HP everywhere, so I bought an Open Flash Tablet and have a Phantom Electric Supercharger on order (to be fair, I always wanted to mod the Prelude VTEC, but I never had any extra money back then). But I'm not complaining about the stock HP/torque curves, either. It just doesn't bother me because if I want to drive fast on a curvy road, I stay above 4500 rpm. If I'm behind someone at 50mph and I want to pass them quickly, I drop into 4th or even 3rd, rev match and blow by them.

It seems most want this small 4cyl to get around someone at 50mph by just stomping on the accelerator in 6th gear. Not going to happen without FI (and I'm not sure you could do it in 6th unless you went REALLY crazy with boost). So shift. It doesn't take anymore effort to shift from 6th to 3rd than it does to shift from 6th to 5th (except for rev matching to make it smooth). My wife's Accord 4cyl MT is a larger 2.4 liter and you've got to downshift it one or two gears to go anywhere, too. It is what it is. I knew that going in. Apparently a lot of others didn't.

I've mentioned this in other posts, but I have a lot of experience riding small bore (85cc and 125cc) 2 stroke dirt bikes. It's common to shift from 5th to 2nd every other turn on those bikes - and there is literally no torque to speak of until about 8000 rpm. I think riding/driving that way is more involving and fun than just leaving it in 4th. But I can understand why those who haven't ridden 2 strokes and who have primarily had 6cyl and 8cyl cars are much more bothered by the tq dip than I am. I just wonder why they didn't buy a different car instead. LOL.

93 Prelude Vtec is just over 20 years now...

Well, no certainly not. When I say it has a lot of torque down low, it has to be taken into context that I'm comparing it with other engines of similar displacement.

And FWIW, I have an OFT as well and an OFH on order. I actually like na engines and I like having the meat of it's power in the high end of the power band. I think this engine with a stage II tune and exhuast/header is just about perfect. I just find the "dip" in stock form a bit annoying.

I think the fact that the OFT alone, at stage I, already goes a long way to eliminating the dip, is a good indication that the reason it's there in the first place must be related to emissions or fuel economy.

Completely agree. I have a hill that in my old 03 Civic Si I would have to take in 3rd gear, and I can get up it easily in 5th gear in the FR-S. But when it comes to accelerating from a dead stop, the FR-S doesn't seem faster because when the torque dip comes it's like a flat spot, whereas the Civic pulled nicely all the way to redline.

D4-S is complicated. My initial understanding is that the dip occurs during the change from port injection to direct injection. Might be a weird inefficiency in the fluid dynamics of the intake, tuning it out might have sacrificed power elsewhere.

http://www.ft86club.com/forums/showthread.php?t=1803

Like others have said, it was a choice, a compromise. If they could have gotten a flat torque curve without sacrifices (be it reliability, emissions, economy, overall power etc.) they would have.

VTEC kicks in yo!...at 5800rpm in the RSX-S. Similar rpms with the Civics.

5: replace the one part that's causing the dip, 0 additional changes needed. Just get a proper header.

Good point. Of course you'll want a tune with that. :)

You can if you want to. However, it's not necessary to remove the TQ dip (I can testify to that, as can a few other lucky FT86SF catted header owners ;))

I agree... But what I meant was, if they felt like they needed to cut power in order to keep it safe, then they might has well of just added slightly gripper tires instead - that way you'd still be able to get the tail out with the added power but yet have more grip for safety.

I theorize that the torque dip was design-compromised in. The low end torques makes it easy to motor around especially in traffic for normal driving and the high end torque well that's just for.... fun.

I suspect the dip is not so much purposeful as it is an unavoidable consequence of a series of compromises required to meet their goals.

You may wish to examine the dyno curves of the Porsche flat-six in the Boxster/Cayman models. Those curves look very similar to our Subaru engine's curves.

Maybe the torque dip is to hold the sweet spot when drifting :lol: no sudden kick/acceleration when sliding.

Honestly, I don't mind that this car has more spunk at the upper RPM range rather than running out of juice at the end

Do you guys drive a different car than me? What is all this "low end torque" you keep talking about?

Oh, well, ...... I just do 90% of my driving below or in the "torque dip", so I just got used to it ....:)

So, the other 10% of the time, when I crank er up past 5,000 RPM's, it's like the 2nd two barrels of the carburetor kicked it .... or VTEC or turbo or a supercharger kicked it (sort of.....http://www.runemasterstudios.com/gra...mages/wink.gif) ..... which makes me a happy FR-S driver ..... :happyanim:


humfrz

It would be better if it was not there, but is it really that hard to learn to drive around it? See what happens when people don't learn to drive/ride on two fifty two strokes? It never it even crossed my mind as being a problem after about a week with the car. Those with MT's have even less room to complain.

what he said, but maybe not a skanky one.............:burnrubber:

It is this very torque dip that leads me to believe that I may end up getting t-boned in traffic, if I'm not careful. I'd prefer not to have it. As a biker, my mindset is, on is on and off is off (the throttle). There's no middle ground! Scary, I tell you, scary!

^^^ this. The way the engine is sandwiched and routing of the exhaust.

:thumbup::thanks:

LOL I don't want to be a grammar nazi either, but this is kind of funny.

So just for the record, and for future reference:


THIS is a BRAKE PEDAL:

http://1.bp.blogspot.com/-88Yt2SaHjy...edal041312.jpg

However, THIS is a "break" http://www.isaiahhankel.com/wp-conte...11/Pencil.jpeg

And this is to "peddle": http://oururbantimes.com/sites/defau.../MariaCart.jpg

For one, the dip is no longer an issue for me because I installed my FT86SF Catted UEL header last week.

The problem I had with the dip was during everyday normal driving I didn't want to have to drop the car down 2 gears and Rev it up to 5k just to pass someone or merge into fast moving traffic.