feliz

The main reason why the 300M is slow is that the engine is mounted lenghtways, the power has to make a right angle pivot to a transverse direction. If you recall from school I think you loose 20 or 25% of your power doing this. This would apply to all LH cars of course. This was the conclusion arrived at after much discussion on another forum anyway.

------------------
Feliz

98 Acura CL, primrose
2002 TL-S, silver

Ed K

There seems to be a general misunderstanding about the inefficiency of gears in transmissions. Most standard transmissions are in the high 90's percent efficiency. Suppose you lost 25% of the power in the right angle gearing as you assume. This energy is lost mostly as heat. Lets assume your engine is developing 250 HP, then 62.5 HP would be lost in the gear. One HP is 746 watts so 46,625 watts would be produced at the gear. This would melt the gear and probably destroy the car in flames. Try touching a standard transmission after driving hard. It is not that hot and if the car is rear wheel drive there are no right angle gears. Touch the differential of a rear wheel drive car and it is not very hot either and it does have right angle gears.

So the question is: "Where does the 25% HP loss go as measured on a dynamometer at the wheels?". The answer is lots of places. A lot is lost in heat at the engine, more is lost driving the water pump, alternator, flexing the various belts, friction in the external bearings,gear losses, moving oil in the transmission, air induction system, exhaust system, hysterysis losses in flexing the tires, brake drag, air conditioning (even when not running) and a lot more.

The automatic transmission is only slightly less efficient that a standard and about equal when the torque converter locks up.

As for the 300M the difference is probably in the car weight, aerodynamic efficiency, torque characteristics of the engine, and traction at the front wheels. Remember, torque is more important than HP and the TL has a very broad torque curve due to the V-Tec technology. Also more gears help keep the engine at the optimum torque range when accelerating.

feliz

Ed; I can't argue with your numbers. The conclusion was derived at after a 300M was dyno tested and the losses were greater than would be considered normal for a front wheel drive car. Someone at the site also had on-board equipment to measure acceleration and from the calculations they came too it appeared it was producing quite a bit less power than the specs indicated. They assumed it was due to the loss in the right angle gearing. The 300M is slow for the advertised horespower in any case.

I've felt many transmissions and differentials after use and always found them very hot!!

------------------
Feliz

98 Acura CL, primrose
2002 TL-S, silver

<FONT COLOR="#800080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by feliz on May 09, 2001 @ ]</font>

Ed K

All rear wheel cars have right angle gearing in their differentials. If you can touch it it isn't very hot. If I remember correctly the 300M is only slighly slower than the TL. I seriously considered buying one in 1999. Was the observation of power loss made on only one car? Was it run on an accurate dynamometer? The hand held units are known to be inaccurate and are most useful in making comparative readings as you make changes to a car. I still think that the primary difference is the torque curve match to the transmission and the number of gears. Unless you have the engine dyno measurements on the particular engine to compare to drive wheel dyno readings on the same engine the loss estimate is not worth much. Also the state of tune must be identical.

PeterUbers

iTrader: (1)

I was also under the impression that the manual tranny is more efficient b/c of the lack of a torque converter, and the direct driveline connection via the clutch -- hence the manual has no viscous oil flow during a launch and can optimize the engine's power. However, torque converters don't "lock-up" usually until a certain rpm, usually in the middle of the powerband -- this allows (in part) for the smooth launch characteristics of an automatic, vs. the more aggresive driving characteristics of the manual tranny. Correct me if I'm wrong, this is just my understanding. Furthermore, a manual transmission weighs less than an automatic, and lacks the clutch-packs, and oil-pumps that also lead to loss of power. The engine is a generator for anything electrical in the vehicle -- instrument panel .. down to the headlights.. to the radio.. to the ecu .. to the navigation -- all these "appliances" draw current .. i.e. P = I * t (Power = Current * time .. in Watts) .. wattage, i.e. horsepower (hp is a measure of wattage) from the engine. It's no wonder the Integra Type R came bare bones -- a true track vehicle -- no A/C and minimal electrical devices on board if I'm not mistaken. The 300M has a 4-spd auto w/ lock-up torque converter -- a less expensive alternative to 5-spd (duh). Also, I agree w/ the torque observation -- the 300M has 250 hp at 6,400 rpm (redline around 6,600) w/ an impressive 250 lb-ft torque in the middle of the powerband, at 3,900. Unlike our TL-S's that peak in hp and torque in the high end of the powerband, this 300M will be naturally torquey off the line and lose steam high-up, and after shifts. And I agree, that's where the VTEC shines -- it's always better to have your peak at the upper-end of the powerband.

Oh, and consequently, it weighs about the same as the TL-S --> 3,591 lbs.

<FONT COLOR="#800080" SIZE="1" FACE="Verdana, Arial">[This message has been edited by PeterUbers on May 09, 2001 @ ]</font>

Ed K

I don't argue with the fact that automatic transmissions are less efficient than manuals. They also run much hotter than manuals and when run under heavy torque conditions for longer periods of time, such as towing, require extra cooling. At lock-up they are not much less efficient than a manual because the torque converter turns as a unit so no oil pumping losses. The pumping in the transmission itself remains as well as the the other inefficiencies you mentioned such as weight. My only argument is that I find it hard to believe that the major loss in performance in the example 300M is due to a single gear mesh. As an engineer and scientist I am very aware of the importance in understanding all the parameters in an experiment. There is not enough information in this case to point the finger at any one cause.

Just to correct the power equation. Power is energy per time such as watts (current * volts, for example). I * t = energy (sort of) and is used to measure battery energy potential, expressed as ampere hours etc. There is an implied voltage associated with this. A 6 volt 10 AH battery does not have the same energy as a 12 volt 10 AH battery. I hope the clears up this point.

The beauty of the VTEC and particularly the TL-S version is the flat torque curve. Torque at the wheels is what counts in acceleration. When you shift gears you want to remain at as high a torque point on the curve as possible otherwise the acceleration will drop until you again enter the peak torque region. Very high performance engines usually have very sharp torque curves and require many close spaced gears to keep at the optimum torque range. This also makes the car difficult to drive in normal street conditions. A steam engine has constant torque and requires only one gear.

I'm still puzzled about the 300M performance and I'm glad I did not get one. Perhaps the manufacturer overstated the engine or others are understating theirs. I know that this was common in the muscle car era of the '60s and '70s.

Road Rage

I think the answer is simpler: Chrysler overstates its HP for marketing purposes, since there is no "controlling legal authority" (a la Al Gore) to call them out on it since measurement setups have a fairly large error factor.

------------------
Rage On!
2002 TL-S w. Comptech header/exhaust
SSR Integral A2's
17x7 45mm offset
Pirelli P7000 (Summer) 215-50/17

feliz

Ed; I can't be any more specific, I followed several 300M forums a couple years back prior to a car purchase and this was the conclusion owners themselves came to on one forum, I can't defend it. It did sound logical to me but who am I to argue with a Phd.

As someone who works with heavy equipment I know I've been burnt many times by leaning or resting agains a transmission or right angle drive. It seemed hot to me but in the big picture I'm sure your right, it probably isn't very hot.


------------------
Feliz

98 Acura CL, primrose
2002 TL-S, silver

Ed K

Feliz: I'm sorry I don't have a real answer to the question as to why the 300M is slower than expected. I know it didn't seem that fast when I test drove it in 1999. I think that it is probably a combination of factors that were mentioned in the replies to your posting. I own a 1998 Chrysler Town and Country and the transmission does not seem to shift as crisply as the Acura and probably looses more energy during the shift. Maybe that's part of it. Thanks for the stimulating posting. I will continue to puzzle over it. At least we can all agree that Acura makes great cars.

Ed