purpose of torque dip

[billwot]

Originally Posted by fatoni

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

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

It seems to provide extra fidelity in the throttle which is nice at the limits of ashesion...

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.

[FRiSson]

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

[Boxer486]

Originally Posted by Bristecom

They'd be better off giving it more grippy tires to compensate for a little more power if that were the case.

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....

[robwbright]

Originally Posted by jjaisli

Especially for a normally aspirated 2.0 liter..

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.

[Andrew025]

Originally Posted by FRiSson

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

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

[jjaisli]

Originally Posted by robwbright

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'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...

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.

[Shagaliscious]

Originally Posted by jjaisli

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.

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.

[strat61caster]

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.

[fistpoint]

Originally Posted by Eurasianman

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

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

[tbertran]

Originally Posted by robwbright

Seems to me that everyone basically has 4 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: replace the one part that's causing the dip, 0 additional changes needed. Just get a proper header.

[robwbright]

Originally Posted by tbertran

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.

[tbertran]

Originally Posted by robwbright

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 )

[Bristecom]

Originally Posted by Boxer486

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.

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.

[Hot Lava]

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.