Mister Two

You think they designed a different chassis just for the Roadster?

How about the PR for the LFA's world premiere hosted on the Lexus UK site then?
http://www.lexus.co.uk/about/news-an...lexus-lfa.aspx
By the way, a front-mid engine design only requires the engine's center of mass to be placed behind the front axle, not very bit of the engine. Hope this clears up your confusion.
http://en.wikipedia.org/wiki/Front_m...l_drive_layout

Joe Z

iTrader: (10)

Do you mean Front Engines??

Front-Mid Engine is very easy to categorize. The Engine and/or it's center of mass sits behind the Front Axles..

I don't think that happens on the LFA..



It does happen on lets say a MB SLR McLaren, as the Valve Covers are easily seen behind the Front wheels..



Joe Z

Joe Z

iTrader: (10)

No, my point was that you were linking a LFA concept roadster...

I do agree with your points now based on all the press mess.

Will just leave it that Lexus doesn't know what exactly call it.... Since they now covered ALL 3 Terms in their data..





Joe Z

Mister Two

The SLR with its super long nose is an extreme case. Other famous front-mid-engined designs include Nissan's FM platform, which actually also doesn't have every bit of the engine placed entirely behind the front axle, and yet we don't see people questioning if it's truly front-midship. The reason, again, is that only the engine's center of mass matters. See my previous post for details.

Joe Z

iTrader: (10)

^^ I see what your saying now... see my post above yours

Joe Z

05RollaXRS

That would imply Lexus is not telling the truth. Obviously, if the LFA engine did not fit the definition of a front mid-mounted engine, they would not call it front mid-engined car in the first place. It says clearly the engine has been placed behind the front axle.

Like I mentioned before, LFA's engine sits entirely behind the front axle as apparent from this picture.

Joe Z

iTrader: (10)

OK.. I do concur with your Assessment now..

I located the engine mounts and do bolt down behind the Front Axles..

It's just wonderful that they list all three terms in their data sheets..

They also have it labeled as a "Front-midship Configuration"

But the engine mounts EXPLAIN it all..






Joe Z

05RollaXRS

Still amazes me whenever I look at that picture how tiny the engine is. The M5 V10 (which also happens to have 10 individual throttle bodies as well) with similar displacement is HUGE by comparison. It is difficult to believe it is a V10.

gengar

But it depends what you mean by "performance". Do you mean vehicle specs, spec times, vehicle dynamics, what? It seems pretty clear you're referring to spec times, but even then, I think that's debatable.

In a straight line or even on a track, dual-clutch transmissions offer better acceleration and lap times than driver-operated clutch manuals on road-going cars; magazine tests on cars like the Cayman and M3 have shown that. I certainly don't dispute that. The problem is, we're not talking about a comparison to driver-operated manuals. We're talking about comparing dual-clutch to clutchless racecar sequentials and semi-automatic sequentials, which are much faster at shifting than driver-operated clutch-pedal manuals - especially for those of us not named Keiichi Tsuchiya or not pro-level drivers.

When you're talking about a 1000-1100kg racecar that is already shifting at 50-80ms (i.e., the engine retardation time in a clutchless sequential like the RSR/Cup), assuming a benefit around a track from increasing weight by more than 10% for a small (if any) difference in shift time is a bit silly, IMO. Keep in mind Nissan actually quotes a higher time (200ms) than that engine retardation figure for shifts with their GT-R dual-clutch, btw.

This is aside from the other issues, such as what is actually meant by "performance". The biggest flaw of the current horsepower wars and spec time wars, which even previously prestigious automakers like Ferrari have succumbed to, is the introduction of bigger and bigger engines as well as technologies like dual-clutch transmissions that have rapidly increased vehicle weight.



Why, just because you say so? C'mon, you don't need to be argumentative just to be argumentative.

They have gone away - on Ferraris, anyway. I agree though that they're not going anywhere on Porsche models. I mean, heck, Porsche offers manual-only models (talk about being able to demonstrate the difference between Porsche and Ferrari philosophies in one sentence). I also always respected BMW for offering manual transmissions despite low take rates (although that's about all the respect that's left, especially now that they've sold out going to FI).

Racecars typically use a sequential manual transmission, often referred to as "jaw-type" or "dogbox", such as the one on the GT3 RSR or Cup car. It's identical to a typical clutch-pedal manual, but the gear construction allows for clutchless shifting (I'm not sure these even have synchros). If you look up racing videos on youtube of the RSR or Cup, you can hear the gears mashing together violently especially on downshifts.

The only similarity to a semi-automatic sequential transmission (i.e., that found on the LFA, pre-dual-clutch M cars and Ferrari models, etc.) is that it is sequential. The semi-automatic sequentials use an automated clutch, so it's functionally much different compared to the racecar sequentials.

Mister Two

The manufacturers actually refer to the transmissions of the LFA and pre-dual-clutch M cars as SMT as well, but I guess they could be implemented differently from the race car versions. Can you tell me exactly how they're different and why the road cars can't use the race cars' implementation of SMT then? Thanks.

07grIS350

05, from what I've read is that the 10 individual throttle bodies gave LFA engineers quite a bit of challenge. They wanted it for max responsiveness, but had issue with clean emissisions. The other issue they have is trying to keep everything simple so it would fit in the LFA's tight body. I wonder if this have anything to do with not using DI?

gengar

There are a couple companies that actually do swaps of jaw-type sequentials into road cars, and they all claim the sequentials are perfectly fine for road use and even daily driving. I've never driven a jaw-type even on the track, but I tend to believe them even though clearly they have their own services to promote and sell. (I actually spoke to one of the companies because I was thinking about buying a GT3 RS and swapping the RSR transmission into it.)

IMO, the biggest issue is probably the long-term reliability. As you might imagine, these do require rebuilds every so often - I've long heard grumblings from RSR/Cup owners/operators that Porsche makes quite good money charging for transmission rebuilds, since they brand their own RSR/Cup transmissions. A secondary issue as far as road cars would be the violence and noise from the shifting, both of which are pretty extreme.

rominl

iTrader: (4)

lol i guess by now you know when i was asking whether it's front or front-mid. i always thought it's front mid, but joe z was saying otherwise until corrected later on

05RollaXRS

Yes, I could imagine how difficult it must have been to achieve that tiny packaging with the 10 individual throttle bodies sticking out. It is definitely a huge accomplishment.

Like I stated before, I strongly believe Lexus decided not to use direct injection due to issues that high-revving cars have direct injection resulting in carbon build-up that leads to a lot of issues. I think their goal was met of achieving around 115 HP/Liter while retaining reliability and more importantly the flattest torque curve imaginable. I am sure they still can easily squeeze out another 20 - 35 HP, if they wanted to. 'Ring edition already makes 570 HP.

I cannot believe how many people who believe whatever they read have said, "458 with only 4.5 Liter V8 makes 398 ft-lbs of torque while LFA with 4.8 Liter V10 makes 355 ft-lbs of torque". Ofcourse, they do not understand LFA cylinder size is much smaller than the 458 Italia and focused on filling them up very fast to achieve the highest revs possible and reaching them quickly, which is why the "peak" is lower and is completely unimportant compared to the shape of the entire torque curve across the rev range.

Upon close inspection, I had posted a comparison where 458 Italia only has a spike in the midrange between 3500 - 4000 rpm where it produces 398 ft-lbs of torque while LFA produces has a significantly superior torque curve between 6000 - 9500 rpm where 458 Italia makes around 10 - 15 wheel torque less. The 458 also hits the limiter at 9000 rpm.

Joe Z

iTrader: (10)

If those engine mounts were on top of the axles all bets would be off..

But you see why my initial confusion was... (below line 1 in each page)

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