Hey man, if pushrods and leafsprings are your bag, then more power to you. I'll pay for quality any day. At least the Z06 has torque down low - unlike the RDX.

 

I had looked at the new 335...WICKED NICE.

Also WICKED EXPENSIVE up here in Canada.....

But a damn nice ride nontheless.

And if you are a boost junkie....heaven.

 

The 2.5 liter na v6 idea would have been a big mistake. That would have made for a terribly underpowered and nose-heavy vehicle, especially when you consider that a 2.5 would likely be even heavier than a 3.0 - assuming it would still be a J series.

 

Fuel econonmy is not the main benefit they were going for with the I-4. They were focused on performance and handling, so weight is the big issue. In the end the turbo I-4 has better torque than a 3.0 v6 and way better torque than a 2.5 would have and allows for much better weight balance and handling. If you don't like turbos... you don't like turbos...I'm not a huge fan myself really, but for this application I think they made the right choice.

 

I understand the reasons, I'm simply saying that the main downside to the RDX is the horrible gas mileage (considering it's a 4). Not smart in a time of rising gas prices. People look at those big numbers and go 'ugh.'

 

In the end a single torque figure is not that meaningful, especially when it is at a high RPM - it says nothing of the torque down low and represents a "peaky" torque curve. The torque peak of the RDX is at 4500 RPM which seems fairly high to me, but most of the Acura models have a fairly high RPM for their torque peak and the RDX is reasonably low in comparison. By comparison the torque peak of a BMW 335i is 1400 RPM and the torque peak of an Audi 2.0T is 1800 RPM. An engine with a wide torque band will often have a low RPM torque peak and a high RPM HP peak and the distance between them gives a vague picture of how broad the band is.

The turbo on the RDX probably gives the RDX more low end torque than the N/A Acura models, but its fairly high peak doesn't paint a good picture and the torque curve tells the full story. I went looking for a graph of the RDX torque but came up empty handed - has anyone seen a graph?

 

Yes, and on top of that, the torque figure stated by the manufacturer can often be skewed in a way that they feel is beneficial to marketing the engine as having a wide torque band. For example, the 335i you mentioned actually has a peak torque higher than 1400rpm stated, but bmw will state the torque that the engine makes at that engine speed to make it sound like it has a super low torque band. In actuality, the 335i should have been stated at something more like 360lb-ft@2200rpm - its underrated by that much.

bmw 335i dyno plot

Most Honda engines offer at least 90-95% of peak torque from about 2000 rpm up. Here's an interesting quote from Shawn Church (Church Automotive Testing) were he's talking about the power delivery in the project RDX with an early Hondata tune,
"What is interesting is that compared to the average TL auto (pre-type-S) on our dyno we're not really making much more peak power (15-20). But, our average power is much, much better. We break 200 hub hp by 3600 rpm and stay there all the way to the limiter. By contrast, the TL doesn't break 200 hp until almost 1500 rpm later (at which point the K23 is making 240 hub hp). But this motor can never be used properly in a FWD car. The bottom end torque is just too strong for any real traction."
This means that the turbo 4 is making more torque down low than the 3.2 v6 in the TL, which itself has a nice flat torque band if youve ever seen a dyno plot.

 

Also, theres no scale on that 335i dyno for the torque numbers, but you can easily see were it peaks at...

 

To be fair, they didn't mis-state the peak torque - they didn't bother to list the peak torque at all because they wanted to emphasize the minimum torque available across a wide range of RPM. By listing it as "300/1400-5000 lb-ft" they made it clear they were talking about torque over a range and not the peak.

I assumed that the peak would be higher, but when they list this range I'm happy with the number and don't really care exactly where it peaks. That engine will be very drivable and that spec is exactly what I need to know that. I don't find the spec they listed as "underrating it" at all. In fact I find a single torque peak figure as suspect in that it hides the broadness of the power band, especially when the RPM for the peak figure is fairly high. In the case of the 335i if they really can list the peak at a reasonably low 2200 RPM then that would seem to indicate a pretty nice flat curve and may have been "good enough", but letting me know that it has 300@1400 (and on up) gives me an even better picture.

If that is true then I would love to see a torque range figure touting that (or a torque graph). The single figures they do list with the fairly high RPM values that go with them make me think that the engines might be "peaky" (in terms of marketing value). That kind of torque response curve may be "fun" for someone who likes to flog the revs on their car, but it doesn't make a great driving experience for someone interested in refined power delivery.

I'd be more interested in peak torque if I was in the market for an S2000, but less so for an RL.

With the RDX it sits in between - some may buy it as a smaller version of the refined MDX that handles like a sports sedan and want to hear that the engine has a wide power band - others may buy it as a more practical mini-rocket alternative to an RSX and want to hear that it revs easily and strongly.

And, driving the RDX, I think it's torque range is OK, but I've driven engines that feel like they have much flatter torque curves (as compared on the butt dyno) so I'm curious to see if it does have 90% on tap for most of its range.

 

Well you were apparently misled by the way they chose to rate the engine before I brought about the actual dyno. If you base your statements off of your impressions rather than knowledge via research, you may appear to have a predisposition or bias. It seems that you have formed your opinion based at least partially by the manner in which the numbers are stated, versus the actual torque band. I'm just saying that the rated numbers, whether stated as a peak or a value over an rpm range; don't mean much either way - but some are more misleading than others.

Also, I highly disagree that a high rpm torque peak doesn't paint a good picture - that only happens if you make assumptions based on that figure. In reality, the bmw's peak number could have just as easily been stated at 3800rpm because it does appear to peak out just a bit there. On top of that, the boost level probably tapers off in the top half of the rev range, otherwise the peak would probably be even higher.

Honda engines and BMW engines are both among the best for full power bands, however, if you look at the dynos hondas tend to have flatter curves over wider rev ranges. I'll post a dyno of a stock K20A from an RSX type S.

 

Doesn't get any flatter over such a wide rev range...


http://i21.photobucket.com/albums/b2...AStockDyno.jpg

 

By the way, a high rpm torque peak can also mean that the head design is very good and free flowing - keeping the torque maxed across the powerband is mostly the job of cam timing and lift variability and good fuel/spark mapping. Both honda and bmw have good variable valve timing/lift systems.

 

If you're not satisfied that Hondas have flat torque curves by the I-4 RSX-S plot above, here's an Accord V6 plot, notice that 95% of peak torque is available from 2,000 rpm (earlier than the 335i) and all the way to over 6,000rpm (much longer than the 335i) True they are not alike in that one is turbo and the other NA, but if you compare the NA inline six from bmw instead you will still be surprised by the honda engine's power delivery.

Stock Accord V6 dyno

 

Hi Jirzlee,

You highlighted a comment I made about the torque peak of the 335i (and same comment was made about the 2.0T). Sorry, I wrote that wrong, but I wasn't misled - I was just trying to say that it makes good torque (worthy enough to be quoted in marketing materials) as low as 1400...

A torque range can tell more than a peak torque figure easily. All the peak torque figure tells you is that it has one spot in the RPM band where it can pull strong.

Combine a torque peak and an HP peak and you can get a picture of how strong it pulls at 2 points and most engines probably have a reasonably linear response between the two (or not likely to be much of a dip between them).

But a torque range gives you a much broader picture. Sure it's not perfect, but the criticism was that the peak was at 360 and I don't find that as compelling as the figure that was given as a minimum from 1400-5000. Actually, looking at the graph that was shown, the torque peak is not 360 - they're misreading the graph. The graph shows that the torque dances just above the 300 line from about 2200 to about 4000 (given that it was an independent test they didn't quite get BMW's claim of the torque all the way out to 1400 and 2200, but that's par for the marketing course). The only way to get 360 out of the graph is to misread the HP figure against the torque axis...?

The torque also hits about the same peak at 2200 - they would be better served by quoting the 2200 figure. But, given how flat it is, their choice to go with a range gave an even better impression.

Cool...

 

Impressive graphs indeed - I'd still like to see one of the turbo application in the RDX (I think it's based on the K20, right?). The turbo needle seems to pop up pretty well even at low RPMs so I'm guessing it will be pretty flat as well...

 

My boost needle is always popping all over the place, but to bring it back to the original post (not that BMW's are not interesting) Do we as RDX owners prefer/love/enjoy the Turbo~VTEC 4 banger or would some prefer.. oh lets say a 3.5 V6 like the FX35????. My vote goes to the turbo inline 4 (it was the main reason for the purchase of my RDX) I think this goes all the way back to my roots you see my first car was a 95 Mitsu Eclipse Turbo (FWD). I just fell in love of being "on boost" its ;like a drug maaaaannnnn : . I know it wastes more gas but i can't stop using it! We must all admit Turbo vehicles are just different beasts (Torque producing beasts) you either love em' or hate em'

 

Although I do like my RDX, I did an experiment this weekend with respect to my complaints about throttle and turbo lag. I took my wife's '03 4cyl Accord out for a spin. We ran a bunch of errands, and I drove. The net is that my wife complained the whole way about how jerky I was with the gas pedal. In reality, I was so used to the lag in my RDX that I was continually pressing the gas pedal early coming out of turns, moving up towards lights, etc. Mind you, this was simply a 4cyl version of the Accord, and it's power, ANY POWER, was much more instant than with my RDX.

The net is that I can live with the turbo lag because it's expected. I think it's the throttle lag that bothers me the most. You expect to be able to step on the gas and have the car immediately deliver at least some power. Instead, you press the gas pedal on the RDX, instinctively/subconciously slightly adjusting your body weight forward in anticipation of some acceleration, and nothing happens - and your body actually lurches forward slightly as you lose all power for a split second. Painfully, it actually reminds me of an old 70s Chevy I had with a carb problem.

So the net is that I think the engine is ok and I probably wouldn't care if it was a 4 turbo or a 6 as long as I got SOME power instantly when I stepped on the gas pedal.

Mike

 

The dyno makes power measurements at the wheels, so you have to make an adjustment considering drivetrain losses to get a value at the crankshaft - which is how all OEMs quote horsepower and torque. If you were to estimate an approx. drivetrain loss of 17%, you have 360 at the crank.

Anyways, I let the test drive tell the real story - whether the figures are given as a range or a peak value doesn't really matter in the end, but I prefer to know the peak figure if I had the choice. Modern engines from the top players tend to have very smooth power delivery, so if engine x makes 200lbft at 6000rpm chances are it will make at least 85% of that starting from 2500rpm or lower. In other words, tell me what the peak torque is and, after I drive it, I'll let you know how good the power delivery is..

 

You need to be in manual mode and keep the engine full to have immediate power. If you leave the car in D, it will upshift early and lose boost all the time.

S does a better job at keeping the revs high but still will upshift if you take your foot off the gas. The only way to have "immediate power" is to do your own shifting...

The only situation in which I notice some "bad lag" is off the line, as in a standing start. Turning off the VSA helps a little, but the car takes some time to reach optimal boost levels.

 

That graph is from May of 2004 ? Was it an AWD dyno? Kinda hard if it was'nt....

See the part that is missing on the graph? Below 2250?
A lot of us who drive in highly urbanized cities, need much more torque in that area, and I think that is what a lot of us are saying.

 

I finally found an RDX torque plot:

RDX Dynojet Research plot (from TOV)

Not very flat at all. It only gets close to its peak torque from about 3400 to about 4600 RPM and drops off steeply on both sides crossing below the 80% mark in the vicinity of about 3000 and 5500 RPM.

I was just noticing today that when I'm driving along at a steady state in the city (30MPHish) it spends most of its time below 2000 (sometimes trundling along near 1000) - even with the S mode engaged. On the highway at 65MPH I seem to recall that it is well below 3000 as well.

 

No, thats not an RDX dyno, its from an RSX-S. If you want a lot of torque below 2250 buy a diesel.

 

The RDX measurements don't start until more than 1000 rpm later than the 335i, but both take about 1200rpm to reach peak torque from where they are first pegged down - the differences are negligible in this area.

As far as the RDX not having a wide torque band goes - don't let the gradations fool you. The 335i graph is stretched wider and torque numbers along the right side go down to Negative 50, while the gradation on the RDX graph is more compact in the "x" coordinate and the torque numbers along the right side go down to Positive 75 - this gives the visual impression of a flat toque band favoring the BMW. In reality, this is not so...

Since you mentioned the 80% value, I'll use that for my example

335i peak torque is 300 * 80% = 240ft-lbs (available until 5800rpm)

RDX peak torque is 227 * 80% = 181ft-lbs (available until 5900rpm)

Doesn't taper off so quickly after all does it??

 

I'm more concerned with the lower end where the RDX spends the vast majority of its time. The story is different there...

 

Some of us consider the "don't start until 1000 rpm later" issue to be a very noticeable issue - far from "negligible". The car tries to do a lot of its driving down in that area that is off the graph and only kicks up into the meat of the powerband when you kick it a bit. That reduces its "driveability" factor somewhat - both for the fact that you have to kick it in the first place and for the delayed response from the kick to the delivery...

 

This is because of the way the dyno was conducted. If they hadn't pegged down the throttle until 1000rpm later in the BMW the graph would look much the same.

The only reason any car would spend much time down at 2000rpm is if you are cruising at partial throttle or just putting along, and in this case there's no car in existence that makes peak torque under this circumstance - and you wouldn't want it to because this is where fuel economy comes into play. The BMW suffers the same wait-for-boost-to-build-delay that the RDX does so I don't know what your point is. Both cars are turboed - you can't get away from tubo lag entirely with these engines. With any turbo gasoline engine, you're never going to be down at 2000rpm during spirited driving or passing for that matter. You'd press the gas and it would downshift - no matter BMW or RDX.

The RDX performs very well vs its competition too. In the CarAndDriver comparison with the 2007 BMW X3, the RDX bested the BMW in all three rolling start acceleration tests.
____________X3____RDX____LR3
_5-60mph____7.5____7.0____9.7
30-50mph____3.7____3.5____4.4
50-70mph____4.9____4.1____6.7

If the RDX torque band was in any way unavailable it would not be possible to beat the X3 in these types of tests. The X3 has the advantage of higher HP and the immediate throttle response of a normally aspirated engine, but the RDX has a wide torque band and a quick-spooling turbo. The Land Rover wasn't even competion for the BMW and Acura.

 

Damn jirzlee, way to prove everyone wrong! nice stats and back up info.

 

My impression was that any number reported on a dyno graph represented an actual measurement of the most torque they could wring out of the car at that particular RPM. Are you saying that at the bottom of the graph there is a "spin up" portion where they are just letting the car gain wheel velocity before they apply resistance to get a decent torque measurement?

or coming off the brakes going into a corner and wanting some torque in automatic mode. If you really care you have the option to go into S manual mode, but it would be nice if the car made decent torque down low so that the downshifts weren't so important there.

But that is exactly what my car does in city traffic (even in S mode) and on the highway. The only time it doesn't do this is when I have it in S mode and I'm cruising a winding road at 50 or so - then it stays in the meat of its powerband, but that is only one (relatively rare) set of conditions under which I drive.

I'm not asking for peak torque - just good torque. This isn't about "using that part of the torque band to put in the best 0-60 time", this is about "the car ends up down there so often and can't respond very quickly to requests for a moderate amount of power".

Fuel economy is an important one of two reasons why I do want it to do this (the other being the driveability factor). Fuel economy would be improved by having lots of torque "on tap" down there. Note that "on tap" doesn't mean the car will actually exert that torque when you are at that RPM. The max torque for a given RPM is only being exerted if you have it floored at that RPM.

At these low RPMs if the car has a lot of torque then you can just barely touch the pedal to keep the car moving and it will use little gas to do so. You could also then accelerate reasonably briskly with only a nudge of the throttle and would use a reasonable amount of gas to do so.

On the other hand, if the car has little torque at those RPMs then you have to run the throttle a little wider to hold speed and you have to mash the throttle pretty far down or downshift into higher RPMs (more explosions per second means more gas per second) to get any kind of reasonable passing power.

My last vehicle weighed within 5% of the RDX, had very similar hp/torque numbers to the RDX, had turbo(s), had way less turbo lag (twin turbos do help a lot with that), had way more power down low and was incredibly driveable both in a performance and on a city street/highway environment all while turning in much better fuel economy. The RDX can chase it reasonably well, and can haul ass when you kick it, but you have to really prod it to do so in comparison.

And, again, I'm not talking (as much) about spirited driving, I'm talking about driving along every day and thinking I want to pass now.

OK, how about now?

Now?

Now, please? (whoosh)

For comparison, I would pass cars in 6th gear going up the grapevine with just a mild brush of the throttle in the low 2K RPMs in my previous vehicle. No downshifting necessary, very little mashing of the throttle, just torque when you asked with only a very slight (fraction of a second) delay.

You can produce good final numbers even with disappointing low end torque and a bit of turbo lag, but there is a lot more drama in doing that than should be necessary to just get around a car on a city street or even on a highway.

 

What was your previous car flar...?

 

Or a DISI Even a FSI 2.0T from VW/Audi. But the DISI doesn't make full torque until 2500RPM, but thats Damn close, Very good torque band, Especially for a 4 cyl. FSI is one of the Flattest.

 

Well, what was the point of posting it then?
I dont want a lot of torque, at this point I'd like some. You can keep trying to disprove what some of us feel with graphs, it's fun to watch

 

The point of the RSX-S and Accord V-6 graphs was to prove my point that Honda engines tend to have very flat torque curves, and this was because "Flar" asked for it, "If that is true then I would love to see a torque range figure touting that (or a torque graph)."

What you feel is turbo lag, and very little of it in comparison to 90% of them out there. All turbos have some no matter what the magazines say. If the graphs don't mean anything, what about the actual perfomance when tested against its direct competition that I also posted - since when does this mean nothing? These are rolling starts, just like you'd do on the street, for passing and merging... If what you guys are looking for is near top performance without needing to press the gas pedal, you won't find it. Depress the throttle - its the only way