MB-telecom

Everyone clains that the TL-S has a 22% - 25% drivetrain loss. I've heard people say it is an inefficient tranny. Most experts agree that one should se no more then 18% drivetrain loss for auto trannys (for FWD cars) and no more than 15% drivetrain loss for manuals. Whoever started the 22% - 25% drivetrain loss 'theory? Has anyone ever had ann engine dynoed on a stand, at the crank? Also how could the new Accord put down on 195 WHP and have only experience a 19% drivetrain loss while we settle for a 22% - 25% drivetrain loss.

The guys at Maxima.org are suing Nissan. The Altima puts out identical numbers for WHP as the Maxima (with the same auto tranny and same engine) and they rate the Altima 240 HP vs. the Maxima's 255 HP.

Something is just not right here with our TL-S's experiencing that kind of a loss. The trannys of the TL-S cannot be that inefficient. It is 2003 after all.

What are eveyone's thjought of the possibility of Acura having overrated the HP of the TL-S? Has (or can) anyone dynoed a TL-S on the stand? I am 99.9% certain that we are not making 260 HP. Hell, my 91 Stealth RT/TT weighs 3385 lbs. It makes 300 HP stock and runs the 1/4 mile in about 13.8 to 14.1. You cannot tell me than an extra 40 HP (I don't care if if my Stealth is AWD - that's worth maybe another 1/10 or 2/10) is worth another 7/10 to 1.1 seconds in the 1/4 mile. The Stealth is also a few hundred lbs. heavier too.

I think our TL-Ss are really about 245 - 250 HP...

Let's hear it!

Pure Adrenaline

iTrader: (2)

The Federal Government tests every vehicle sold in the U.S.

Hyundai rated their V6 at 181-hp. Feds found out that it only makes 170-hp. So Hyundai brought down the rating and offered a free extended warranty for the owner of every model affected by this "false advertisement".

I don't think any car company overrates their cars/engines on purpose. Except for one case -- in the U.S., if the horsepower rating came out to 257 hp, then it's legal for them to advertise it as 260 hp. European cars don't do this. That's why you see odd numbers such as 333-hp rating on the new M3. Or 302-hp in the Mercedes' V8.

If it is indeed overrated, then Acura is going get hit SEVERELY.




As for the 1/4-mile times, it's not just about weight/power ratio. It also depends on the powerband, like when the horsepower/torque really kick in at what RPM. In most imports, you don't get much power until you hit high RPM's. A prime example is the S2000. 240-hp, but only 147 or so lb/ft of peak torque at redline. Whereas my dad's Tahoe is rated at 255 hp and 335 lb/ft of peak torque at 3300 RPM. However, at 2100 RPM, it already produces over 250 lb/ft of torque.

What I'm trying to point out is that if you race two cars with similar weights and similar power, but one produces that power at a much higher RPM, then as you are nearing the finish line and are NOT hitting that power point, then you won't get the same times. Am I making any sense? I'm such a bad storyteller/explanator (is that even a word? )

But, anyway... 260 or 250, it's pretty peppy. That's basically what I'm trying to say.

fortunate

Interesting find. Where did you hear about the 22%-25% loss?

MB-telecom

I have seen people's posts over the last 10 months of what different 02 TL-Ss have dynoed. Not a single stock TL-S has dynoed at or above 205 WHP. Even at 205 WHP that would still be a 21% drivetrain loss. 21% is pretty far out of the margin of error (+= 1%) on an 18% drivetrain loss on a FWD car.

I am curious. Maybe those members who had their TL-Ss dynoed back when they 100% stock could repost some dyno figures in this thread. That would probably help. Still looking for some Mods and 'big guns' of this site to reply. Maybe I am off base, but I think there's something wrong here with HP figures/claims by Acura.

power3dfx

you are right about the loss to wheel, it shouldn't be this high. the only way to see if acura is telling the truth is to test the engine at crank period. that will reveal exactly what is the culprit. keep in mind that alot of cars these days have crappy drivetrain loss %. for example, a gs4 dynoes around 240 hp at the wheel(not sure on this, maybe rominl can verify) which is also 20% loss.
Move over to the new g35 coupe, dr rick at clublexus dynoed his and got 225 whp also 20% loss (though he hasnt hit his sweet years yet).
Just goes to show you that auto's suck these days imo.
ever since the hp war started, manufacturers build inefficient trans and drivetrain systems and substitute with modified engines.
its all for marketing. no maker will say "it produces 260 hp, up 10% from last year, and its drivetrain has a 5% decrease in efficiency." Instead, they state the big and foremost important number which is HP.
heres a good comparison:
dell can offer 3 Pentium 4 2.4 ghz computers with equal numeric specs, yet at different prices. they cut cost using ddr or sdram in place of rdram which was intended for use with the P4. Now to the average consumer that may not be aware of the differences, may think they are getting the system for cheaper, yeah right!
the point is, tricks are always played, there is no stopping it..........

TopGum

I got this on a yahoo search. Food for thought:

Converting chassis dyno results to flywheel horsepower

Typical horsepower ratings you hear are gross (total HP) or net (gross less HP needed to drive engine accessories) engine HP at the flywheel. A chassis dyno, measuring power output at the wheels, generates smaller HP numbers since they are net of power lost in the drivetrain. How do you convert the chassis dyno number to the more widely-used flywheel rating for determining your motor's HP output?
The short answer is, you don't. The power lost in the drivetrain is generally reckoned to be anywhere between 15% and 25%, depending on the transmission and other components, even the viscosity of the gear oil. However, there no easy way to be able to make strong assumptions about engine HP based on what drivetrain you have. This, in any case, is the word from Dynojet, a leading manufacturer of chassis dynamometers. According to Sean O'Leary of Dynojet ,

There is no direct number for drive train loss to correlate to flywheel horsepower. There are too many variables for this number to be realistic.
The Dynojet Automotive chassis dyno will read within 1% between dynos anywhere in the world, and you don't need to remove the engine, so the most accurate way to compare two vehicles is to look at rear wheel horsepower.

Obviously, that last sentence sums up pretty well Dynojet's take on the matter: since they make chassis dynos, not engine dynos, it's not surprising they insist HP at the wheels is all that matters. Personally, this makes a lot of sense to me. What's the point of measuring engine power when, at the end of the day, the engine has to drive something to be of any use?
Dynojet's marketing notwithstanding, I have heard that with an automatic transmission you are looking at around 18% to 20% power loss from the drivetrain.

juniorbean

iTrader: (5)

It shouldn't be that high... you're right... but the think is that Honda/Acura's trannys lose the more power then the average. It's sad but true.... it's the price you pay for an LEV or ULEV vehicle and it part of the reason you can get over 30mpg highway in a 260hp sedan.

I'm almost positive that someone on the CL board had access to a crank dyno and they dynoed the car at like 261hp or something like that. I'll have to check the archives... but this exact thing came up before when Mazda and Nissan overstated their HP and someone did that crank dyno. It was a while ago... so I'll have to see if I can find the topic.....

As for what changed on the new Accord... well, it's a new Tranny design as far as we know (since the old design was so problematic since 2000).... so that could have something to do with it....

Ray_Khan

I think I have seen enough 190-200 whp dynos of stock TLS's to believe this is pretty accurate. Like mentioned before, there are so many varibels in measurring wheel hp. Using a percentile to estimate crank hp is just an estimate. When you add power, the driveline doesn't necessarily rob the same % power...it's more of a function than a percent.

Ruski

Hey I remember someone here saying that Acura's trannies were SO efficient, that they broke from all the hard work they do.

Ruski

I think there are two letters L in the word varibell

MB-telecom

How does an ineffiecient tranny relate to improved/increased gas mileage? Is there in an inverse relationship between tranny efficiency and gas mileage? I would think that it should be a direct relationship.

Ray_Khan

ooooops....where is the spell check!

juniorbean

iTrader: (5)

Well, honestly... I really don't know much about this kind of stuff.. but I would think that more moving parts equals more possible power loss... yet all of those parts are usually involved to produce better gas mileage by adjusting settings on the fly....

Take the torque converter for example.... the constant locking and unlocking of it by the car will cause you to lose some power while improving gas mileage.

But, as Ray said... there are a lot more variables involved with power loss from the crank to the wheels then just the tranny... to take a percent and subtract it from 260hp isn't really accurate.

BTW, I haven't been able to find the link I mentioned above yet... but since I've been in meetings all morning I haven't looked hard... so I will keep checking....

T Ho

Except that it's spelled variable.
HP ratings for US vehicles have been net since 1972, gross before that.
You have to factor in pumping losses, inertial losses, and converter slippage when looking at auto losses. Does the Accord use the same exact trans as the TL-S? Show me some back to back numbers (flywheel, then wheel) for some auto cars that consistent show losses in the 16-18% range. I haven't seen any. And, don't forget- when comparing different cars, you have to consider the inertial loads of the CV shafts, discs, wheels and tires. Bigger is generally worse, in most cases, and this will lower rated WHP.

Has anyone considered the possibility that Honda is underrating the Accord, for marketing purposes, so as not to "overtake" the TL-S? The govt allows that. Look at the 02 LS1 Camaro/Firebirds- these are rated at 320 flywheel HP from the factory, and yet everyone with the M6 is putting down 300-320 wheel HP 100% stock. Tests have shown that the M6 (manual six speed) shows a consistent loss of 45-55 HP, putting 320RWHP at 365-375 flywheel.

The less efficient a tranny is, the worse the mileage would be, generally speaking. However, high inertial loads, with low pumping losses, can show good efficiency at steady state speeds, but higher losses during spin up. Torque converter lock/unlock can't really be looked at as a loss, since leaving it unlocked all the time is really the only alternative (which is a full-time loss, due to slippage). Just about no transmission that I know of stays in converter lock at full throttle- it would quickly break things.

Having driven many older cars with auto transmissions, I can guarantee that they are not worse than they used to be.

Todd

juniorbean

iTrader: (5)

Exactly what I was trying to say. You type what I think

Seriously though.... good point on the Accord... it could definitely be a marketing thing....

MB-telecom

Everyone has their reasoning at this point, but until we get an enigne dynoed on the stand everything is pure conjecture about why the tranny might cause such great HP losses. I think the TL-S HP rating is overstated by 10 - 20 HP. Much of the gas milaege rating (especially highway) is due to the gear ratio in 5th gear and what RPMs the engine is turning. The torque convertor has nothing to do with steady highway cruising and the mileage you will get. Also I never said auto tranny cars were in the range of 16% - 18%. I never even gave a range for auto trannys. I said autos never really see more 18%. drivetrain loss. This 'overall average' was proven in court when Ford lost the case on the 99 Cobra debacle.

I wonder what Acura would say about the huge loss through the drivetrain that is way, way over 18%? The factor is above average by a 20% - 28% margin for drivetrain loss. That doesn't seem odd to anyone other than me? The Acura tranny is roughly 30% less effecient than that of other FWD auto trannys? Some may buy it, but I won't until I see data. I could convince the wife to pull the enigine just to have it dynoed otherwise I would.

fortunate

Any links to that 99 Cobra case? I can't seem to find it on google.

Edward'TLS

No wonder our transmissions won't last long. The lost horsepowers are consumed as friction, wear, and heat, and all these gradually destroy the transmissions.

MB-telecom

Somewhere buried in this thread http://forums.maxima.org/showthread....hreadid=166163 over at maxima.org is the link for the Cobra case. This Nissan thread about their lawsuit is pretty intense.

T Ho

Sure it does. At steady cruising, it's locked up. That's a big contributor to closing the economy gap between manuals and autos.

Obviously, the deep OD 5th is a big factor, but the torque converter is not to be dismissed. Not to mention, without it, the trans would be operating below converter stall continuously in 5th below 70mph, which would lead to burned up transmissions (even moreso than now).