Random Automotive Stuff

[neomagus00]

so, i'm sitting here thinking up new ways to spend money, and it occurred to me that a lighter flywheel would be dandy... but i have an automatic transmission...

do auto cars even have flywheels? if so, why can't i find any lighter ones for my car? if not, is there an equivalent bit that i can lighten in order to achieve the same benefits (i.e. increased throttle response leading to decreased turbo lag, plus better gas mileage)??

any pointers to articles, books, etc. are cool, too...

[audiobliss]

Automatic transmissions hook up to the engine via a 'viscous coupling', meaning it's all fluid. There is no physical connection between the engine and the transmission except when the torque converter kicks in at over a certain speed. So, I'm pretty sure you don't have a flywheel, and I have no idea what you could do to your transmission except for having the shift points re-programmed.

But of course, I could be wrong. Am looking forward to finding out if I'm at least somewhat right or not.

[PolkThug]

Get a lightweight driveshaft (aluminum or cf).

[neomagus00]

it's a front-wheel drive...

i read the howstuffworks.comtorque converter article, and while i don't see a way to lighten any of that short of a totally custom converter, it does mention that the assembly is bolted the the flywheel of the engine, which could possibly be lightened...?? i mean, any way to take weight off that 40+ pound assembly has to help...

on two related notes, is there any way to increase the efficiency of the converter i have now? i.e. if i replace the fluid with a heavier weight, would that give me more oomph off the line? or would it wreck the balance of the converter?

the other note: bliss mentioned having the shift points reprogrammed... is there a way i can hook up buttons to allow manual shifts?? i.e. leave it in full-automatic normally, but disable the shifting program and do it manually when i want?

[PolkThug]

If you would post what your car is, and any mods you have already done, this would be a lot easier. ;-)

[neomagus00]

ah, yes, that is true :p

2000 Saab 9-3 Turbo Convertible
Drivetrain: FF
HP/Tq: 185 HP / 184 ft-lbs (spec'd - actually a little more of both, i believe, but no dyno runs)
Weight: 1450 kg @ 62% front / 38% rear (again, spec'd - i've taken out some weight and put in some, i've not yet measured the corner weights)
Engine: 1985cc turbocharged, DOHC with 2 balancing shafts

Mods: (clearly the beginning of a long road)
Some airbox modification (working on a cold-air ram)
Brake pads and discs (Hawk pads, Brembo rotors)
17" ASA EM9 wheels with Avon Tech M550 A/S tires
Uprated Rear Anti-Roll bar
Uprated Transmission Mount
Platinum Spark Plugs

[PolkThug]

First step, get a baseline. Take your car to get dyno'd with Air/Fuel ratio and print it out. The A/F ratio throughout your powerband will tell us a lot about what you need to do.

[audiobliss]

First off, the torque converter only engages above something like 50 or 60 mph, making the ratio from engine to transmission be 1:1, thus increasing efficiency and decreasing fuel consumption. I see no performance gain to be had by messing with the torque converter.

Next, the flywheel. I guess it seems automatics do have flywheels...I don't know. But lighter flywheels aren't always a good thing. For instance, if you had a manual and got a really light flywheel, it could be difficult to keep it running at a light. With a typical 'heavier' flywheel, its inertia (contributed to by its weight) helps keep the engine running at such a low speed. If you get a light flywheel, it may not have enough inertia and you may have to constantly tap the gas to keep the engine running. There is a line there between too heavy and too light, but I don't know where it is.

About the manual shifting buttons. That's a neat idea. I know I've seen where I could buy such a device to manually shift my (automatic) Cherokee via an electronic knob whenever I chose, and let the computer do it for me the rest of the time. Howevever, that was mainly for off-roading, and I have no idea what the responsiveness of the setup would be. Though, it was only like $100 or less. Would be interesting to see if there is such a thing for your Saab.

I would say, assuming you're going to keep the stock turbo and fuel delivery system as-is, a reprogrammed ECU would be a good performance mod.

[neomagus00]

the article i linked to said that the torque converter was situated as the only link between engine and transmission; therefore, if one does something to increase the power transmission across said converter - such as increase the viscosity of the fluid inside - that should, theoretically, increase the efficiency of the converter... the question is, what's the downside?

and yeah, that's a good point about the flywheel - if i found such a thing, i'd be sure to research it enough to know where that breakpoint is between better throttle response and not stalling at idle :p

as far as the shift buttons go, i'd expect that i'd have to do it on my own... it sounds simple enough... set a switch that can interrupt - or better, deny - the 'shift' signals from the ecu, and instead have a pair of shift buttons that send the appropriate signal... there could be the issue of the ecu thinking i'm in fourth when really i'm in second, but i'm not sure it takes gearing into account... another research topic... do you have a link or something to that shift unit? it may be a good place to start looking...

and yes, a stage-2 upgrade is on the to-buy list, with a cat-back, uprated fuel pump, and reprogrammed ecu, but it's a cool $1000, so that's not happening any time soon...

PT - how much should i expect to pay for a good quality dyno? i'm sure i can find a shop, but i'd rather know a ballpark figure before i walk in and they rip me off...

[audiobliss]

Here's the link to the guy who's selling the manual shifting kit for the Cherokee.

http://www.awshifting.com/4-0.htm

[PoweredByDodge]

... this may sound harsh, but if you didn't even know that automatics don't have flywheels, then you shouldn't be working on your car or attempting to modify it.

automatics have the crank bolt up to the torque converter, or, in the case of some odd chryslers and amc's, there is a flex plate that bolts to the TC and then to the crank...d

[neomagus00]

... this may sound harsh, but if you didn't even know that automatics don't have flywheels, then you shouldn't be working on your car or attempting to modify it.

i totally agree... in order to modify, one must have knowledge, and the only way to get that is ask...

[PoweredByDodge]

First off, the torque converter only engages above something like 50 or 60 mph, making the ratio from engine to transmission be 1:1, thus increasing efficiency and decreasing fuel consumption. I see no performance gain to be had by messing with the torque converter.

You're on the right track, but you're a little off... torque converters with lockup have the lockup feature engage only at highway speeds (usually). however, the actual torque converter itself is in use constantly. it is the viscious couple (as neo put it) between the motor and tranny... to move the vehicle at all, the torque converter must be functioning as designed.

most people swap out torque converters after a camshaft upgrade.

often, a hopped up cam requires the idle to be raised from say 700 rpm to 1,000 rpm or even a little more sometimes.

in order to keep the vehicle from wanting to take off like a bat out of hell at idle, a higher stall torque converter is installed. these higher stall converters come in various stall ratings, and will sometimes even making the transitions between gears a bit more 'stiff' feeling as an added side effect.

Next, the flywheel. I guess it seems automatics do have flywheels...I don't know. But lighter flywheels aren't always a good thing. For instance, if you had a manual and got a really light flywheel, it could be difficult to keep it running at a light. With a typical 'heavier' flywheel, its inertia (contributed to by its weight) helps keep the engine running at such a low speed. If you get a light flywheel, it may not have enough inertia and you may have to constantly tap the gas to keep the engine running. There is a line there between too heavy and too light, but I don't know where it is.

I'm kind of fuzzy on my opinion on that... see, if you take the same motor (any motor) and put it on an automatic after it was originally on a stick, you'll notice that it will stall as soon as you put it into drive. the idle has to be raised to compensate for the parasitic draw of the automatic tranny as well as the constant load of the torque converter.

you can run an engine bare - meaning that it is on a dyno stand with nothing hooked up at the crank... just bare ass motor... it's not something i'd necessarily advise, but you can do it...

so i don't think it would stall due to not having the weight of the flywheel (for example if you had a super ultra light weight flywheel). the mass of the pistons, rods, and crank 'lobes' (counterweights on the crank) is HUGE compared to that of the average flywheel... it dwarfs it.

to my understanding, the only purpose of the flywheel is to allow the starter gear teeth to engage and start up the engine.

i may be wrong, but i believe i heard some drag racers don't use starters, instead they simply push start the vehicle, eliminating the need for a flywheel and knocking off 25 pounds for a starter and whatever weight the flywheel is.

EDIT --> In many non-performance cases, the flywheel is also used as the frictionplate for the clutch. So while you could dump the flywheel, you'd have to replace it with a friction plate (obviously smaller, lighter, but just as strong).

[neomagus00]

yeah, so i just read that the Dana Corporation has filed for bankruptcy... would these be the same people that make the infamous Dana transmissions?

[PoweredByDodge]

it can't be.

Dana doesn't make transmissions :P

However, they do make Axles, and last that I knew, I could have sworn they were GM affiliated, and thus a bankruptcy doesn't surprise me.

Least Chrysler still makes it's own rear end, or they'd be in deep ****... Dana rear ends and front ends make up over 70% of the axles used by chrysler every year in trucks and suv's and even the charger/magnum and other rear wheel drive cars. maybe the old Corporate 9000 will be coming back after all.

[audiobliss]

PBD - Thanks for straightening me out on this. I've since read about torque converters (just a little) and have learned they are the connection between the engine and the transmission, and so they're always in use. (So does this mean that there for sure is no flywheel in an automatic transmission? If not, then how is the torque converter turned by the engine? There has to be some type of connection there...)

As for the lighter flywheel making it harder to idle at a stop light, I know for sure I read that in some automotive magazine, but I have no idea which one. I must admit that if the weight of the reciprocating assembly is much greater than the weight of the flywheel, then it doesn't make sense that the flywheel would have such a drastic effect on idling.

About drag cars - I've also heard that they don't use flywheels. Instead, they just have a 'multi-step' (for lack of a better term) clutch. It engages such that the first 'step' allows there to be a lot of slippage so the tires don't just melt (as I assume that's more likely than the engine stalling due to a 1:1 ratio), and then the connection gets progressively more efficient (what's a word you would use to mean 'closer and closer to a 1:1 ratio'?) as the car builds up speed. Very interesting, to say the least.

Dana going out of business?! That's a crying shame. They make (made?) wonderfully sturdy axles. They're soo big in the off-roading industry (and even on factory vehicles) that I can't even fathom their going out of business. And I can't say as I've ever heard they're affiliated with GM...but that doesn't mean anything.

[neomagus00]

Dana doesn't make transmissions :P However, they do make Axles...

yeah, axles, that's what i said... :D

far as the flywheel goes, i'm going in for a 90k service in like 10 days, so i'll make the tech point out all these pieces, and we'll see how my car, at least, is put together...

[audiobliss]

Perhaps the transmission manufaturer you're thinking about is Allison. They make great heavy-duty transmissions for big trucks, and Chevy puts 'em in their heavy-duty pick-ups and Hummers. Allison and Tremec are really the only two transmission manufacturers the average Joe who doesn't care about cars really recognizes, I would think. I do care about cars, and right now I can't think of any more! :p Well, besides the old Muncies...

[exalted512]

i thought ford was the biggest users of dana axles...GM, as far as i know, makes the big ass 14 bolt rear ends and the smaller 10bolt rear end for their trucks. The front is IFS. Im pretty sure dana does not make their axles. Could be wrong though.
-Cody

[PoweredByDodge]

70's / 80's chevy trucks use mostly dana 44's up front and 60's out back. the heavier you got up in the truck line, the more likely you were to see 60's up front (offset obviously) as well.

far as what they're using now -- i honestly dont know - but the question would be, "if it's independant, then who makes the center section?" i have no idea.

chrysler was notorious for 44's up front and either 60's out back or corporate 9000's.

ford F-350's have dana 60's up front, but use maily Dana 44 or even 50 center sections up front on 150 and 250 models with independant front suspension.

not sure what ford has been using out back - i thought they were using their own stuff.

so - at the current time - yer right cody - looks like ford's the #1 user of Dana gear (considering the volume of vehicles they sell).