Why the low torque?

[stonenewt]

That's a Toyota engine. The valve timing change was adjusted down to 5600 rpm which seemed to be the crossover point with that cam & a touch of forced induction. Before force induction it was better to swap at 6500 rpm & the torque curve was no where near as flat as it is there.

The really interesting bit of this system is that the setup didn't have a waste gate. The turbo was always spinning at full chat & any excess pressure was bleed off before the IC. Boost pressure was controlled by the MAP sensor. While most consider this method a bodge it introduced far better control of the boost levels & allowed for a much more linear throttle response with virtually no throttle lag once above 3000 rpm.

[Ubersuber]

That wasn't a factory turbo I assume since Toyota supercharged that engine I had thought.

The naturally aspirated version of that engine was a screamer, didn't it rev to 8,000 or somewhere near there, from the factory?

Unless the dyno graph was adjusted differently than standard to show "true" torque that Toyota engine had lower peak torque than the BRZ. If I read correctly it also produced less power at 7,000 rpm than our Subie boxer, but that would be the 10% approx smaller displacement effect I expect.

[Muaddib]

The torque dip make our car feel a lot slower than it is.

[stonenewt]

Originally Posted by Ubersuber

That wasn't a factory turbo I assume since Toyota supercharged that engine I had thought.

The naturally aspirated version of that engine was a screamer, didn't it rev to 8,000 or somewhere near there, from the factory?

Unless the dyno graph was adjusted differently than standard to show "true" torque that Toyota engine had lower peak torque than the BRZ. If I read correctly it also produced less power at 7,000 rpm than our Subie boxer, but that would be the 10% approx smaller displacement effect I expect.

Yeah, it started life as an N/A 111R. It’d pull to 8250rpm stock. That dyno always seemed to give low figures, but it was consistent. For comparison this is the stock, factory & final figures from the same rolling road
Stock/factory/turboed
128/133/146lbft @ 6900/6800/7800
176/189/240bhp @ 7700/7800/8700

[Ocala FR-S]

Originally Posted by Ds3ire

Good day guys and girls,

I was wondering about the torque figures on the Toyota86/ Scion FRS. Can somebody explain to me why they are so low at 205 Nm? I dont have an issue with the power as 147kW is sufficient for daily driving as well as fun on weekends. But the low torque figure indicates to me that this car has extrememly low pulling power.

Any thoughts on why this has been done? Initially thought that it was due to the low body weight and to resist burning out the tyres on take off.

This leads to higher revs required to spin the crankshaft to get the car moving initially. The gear ratio helps to even this out (3.58:1) but its still low torque going to the crankshaft. The other downside of this is that we have to change down a couple times when overtaking as the pulling power is just too low.

The concern is that cars with similar mass vehicles, especially diesels, the torque and pulling power is much higher. A 1.2l polo diesel has 220Nm torque.

So my question is: Why is the torque so low on these cars and what are the effects of it?

The torque is low because the engine is small to keep the car at a light weight. The effect is that the car does not accelerate quickly.

[wparsons]

Originally Posted by Ubersuber

including the valve timing constraints that produce the torque "dip" in our engines. In reality what you are seeing is two torque peaks resulting from a two stage variable valve timing system optimized for two overlapping rpm ranges.

The dip isn't because of valve timing restraints. If that were the case, it wouldn't be fixed by swapping headers and a tune. The dip is because of harmonics in the exhaust manifold (and possibly the intake as well).

It is also not an overlap from a "two stage" system. There is not two stages, this isn't like VTEC or VVTi. We run one set of cam lobes all the time. Further, the timing is constantly variable, not set into stages.

[stonenewt]

Originally Posted by Ocala FR-S

The torque is low because the engine is small to keep the car at a light weight. The effect is that the car does not accelerate quickly.

VAG & Fiat get 250Nm from a turboed 1.4l engine. Citroen/Peugeot have 330Nm out of a 1.6l petrol & If we start looking at forced induction 2l engines then you can be looking at 400Nm. All of these are comparable engine weights to the Subaru's engine.

It lacks torque because the decision was made for it to be light & N/A. All turboed petrol engines lack really crisp throttle control & engine response. This was the failing of my Elise, as fast as it was it never really measured up to the current Elise S CR because the turbo simply dulled the car.

[Ubersuber]

Originally Posted by wparsons

The dip isn't because of valve timing restraints. If that were the case, it wouldn't be fixed by swapping headers and a tune. The dip is because of harmonics in the exhaust manifold (and possibly the intake as well).

It is also not an overlap from a "two stage" system. There is not two stages, this isn't like VTEC or VVTi. We run one set of cam lobes all the time. Further, the timing is constantly variable, not set into stages.

I cannot resist this time. In your inimitable fashion you've managed to agree with me while trying to contradict me. This is just too funny for words.

Helpful hint: "The dip is because of harmonics in the exhaust manifold (and possibly the intake as well)."

Well, no kidding eh, Einstein?

PS I wonder why Subaru calls their system Dual Active Valve Control System....?

[stonenewt]

My impression was the valve timing changed somewhere in the 5000-5500rpm range. Up there the engine feels like should be going off-cam but doesn't until a little south of 7000 rpm. In all honesty that dip doesn't feel like the engine going off-cam, the initial band is too small. It feels much more like the dip you get from a badly tuned or cat exhaust manifold. As though there's a bigger dip than you actually feel but it's minimised with the engines natural torque peek.

[Dipstik-sportech]

Originally Posted by Ubersuber

I cannot resist this time. In your inimitable fashion you've managed to agree with me while trying to contradict me. This is just too funny for words.

Helpful hint: "The dip is because of harmonics in the exhaust manifold (and possibly the intake as well)."

Well, no kidding eh, Einstein?

PS I wonder why Subaru calls their system Dual Active Valve Control System....?

My rav4 with vvti doesn't dip, nor does my my buddies 7mgte. My other friends boxster s on the other hand does exhibit a dip........explain smartass.
These cams in no way control lift, only duration.

[wparsons]

Originally Posted by Ubersuber

I cannot resist this time. In your inimitable fashion you've managed to agree with me while trying to contradict me. This is just too funny for words.

Helpful hint: "The dip is because of harmonics in the exhaust manifold (and possibly the intake as well)."

Well, no kidding eh, Einstein?

What's actually funny is that you find that agrees with anything you said. You claimed the dip was because of limitations in variable valve control system, which couldn't be further from the truth. What is funny is your ability to consistently be wrong about everything automotive. You also claimed there were two overlapping profiles, which isn't true. Spend any time at all looking at logs of the VVT angles, and you'll see that they're constantly moving depending on load, RPM, TP, etc. It's not two predefined profiles at all. The tables that control VVT angle (separate for intake and exhaust) are dependent on many variables.

Originally Posted by Ubersuber

PS I wonder why Subaru calls their system Dual Active Valve Control System....?

Hint: it's because it works on both the intake and exhaust cams. Just like BMW's double VANOS. Some earlier variable valve timing systems only worked on one cam (or set of cams if it was a boxer/V), when those companies added variable timing to the second cam (or second set of cams on a boxer/V) they added the word double or dual to differentiate their systems.

Originally Posted by Dipstik-sportech

These cams in no way control lift, only duration.

Technically duration is fixed too, just timing is adjustable. As far as I know, the system can't shift timing fast enough to artificially adjust duration.

[Dipstik-sportech]

Oh my bad I thought it was quick enough, I haven't looked close enough at my logs.

[blackhawkdown]

all i have gotten out of this thread is that there is no replacement for displacement, except FI but then you are going into another thread.

[Quentin]

Toyota's 1GR with dual VVT has the double hump. I haven't looked at the 2GR torque curve lately. The GM 3.6 has the double hump in several iterations.


Sent from Tandy 400

Edit: found the 2GR-FSE; posted in the next post.