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operation boro thunder
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just found an interesting article regarding AUTOMATIC TRANSMISSION, yes A/T, not M/T. All u A/T car owners read! :smile:


Automatic Mods
By Eric Adkins

In the import tuning community the automatic transmission equipped vehicle is often frowned upon when it comes to "hopping" the vehicle up by most. The main reason for this is do to the sluggishness of the automatic transmission. Also unlike a manual transmission, an automatic transmission is stuck with the preset shift points (which can be adjusted with certain mods). Compared to an automatic, a manual is just plain fun to drive. One of the good points of having an automatic is that in bumper to bumper traffic, you don't have to keep shifting. Eating is also easier. And lets not talk about having that hot date in the car! From a racing stand point, automatics do quite well in bracket racing. It's hard to miss a shift with an automatic. I myself autocross and have found that doing a few tranny upgrades will help you sort of even the playing field with those darn fast manuals. Many ask me why did I chose to stick with the automatic. My reason is mainly due to it being a challenge. I was told by a speed shop owner about 3 years ago that I would never get a Nissan Sentra 1.6l to make any decent power and the fact that my car was an automatic made it even worse. Three years later, I'm still modifying my car. I plan to prove him wrong. Folks lets face it, if you have a automatic and a manual with the same mods, the manual is going to be faster due to the power lost through the automatic drivetrain (around 20-25%). Cracking open the tranny can help you gain back some power often lost in an auto tranny equipped vehicle. The purpose of this article is to provide options for those who wish to travel the road of modding a car with an automatic. I truly believe that if you want to make big numbers on the 1320 using a naturally aspirated automatic transmission equipped vehicle, you would be better off swapping to a manual transmission. BUT, if you want a good daily driver, consistent bracket racer, or a good autocross vehicle, this article is for you. With that said lets get started.

Lets start with the torque converter, as this is one of the most important parts of the automatic when it comes to keeping as much power transfered to the wheels. Basically a torque converter replaces the conventional clutch. It has three main functions:

It allows the engine to idle with the vehicle at a standstill, even with the transaxle in gear.
It allows the transaxle to shift from range to range smoothly, without requiring that the driver close the throttle during shift.
It multiplies engine torque to an increasing extent as vehicle speed drops and throttle opening is increased. This has the effect of making the transaxle more responsive and reduces the amount of shifting required.
I found a good source of information on torque coverters at Level 10's website. Here is a little more technical information to keep you on the right track:
A Torque Converter is fluid-filled case that contains a set of turbines - there is an input turbine that is driven by the engine, an output turbine that connected to the transmission's input shaft, and a stator turbine between them that directs and controls the flow of the fluid. At a certain input RPM, the torque converter will reach its maximum fluid flow. Below this input RPM, there is poor hydraulic "coupling" between the input turbine and the output turbine - there is a lot of "slippage". Above this input RPM there is a hydraulic "lockup" - there is almost no slippage between the input turbine and the output turbine. This certain input RPM is called the "stall speed" of the converter. This property of a torque converter allows an engine to rev-up to a speed where it begins to make significant power (commonly referred to as "torque multiplication") before being put under a heavy load. The stall speed of a torque converter needs to be carefully matched to the torque curve of the engine it will be used with. A high-performance or race engine, which makes power only at high RPM, needs a torque converter that has a very high stall speed.
-Level 10

Image courtesy of Dunrite Converters.
The torque converter is a metal case which is shaped like a sphere that has been flattened on opposite sides. It is bolted to the rear end of the engine's crankshaft. Generally, the entire metal case rotates at engine speed and serves as the engine's flywheel. By upgrading a torque converter a vehicle's stall speed can be adjusted allowing the vehicle to reach a higher rpm to launch from. To find one's stall speed, all you would have to do is power brake your car and watch your tach. The highest rpm achieved without the wheels slipping is your stall speed. I have a B13 and found that my stock stall speed was 2,000 rpms. My torque converter was ditched for an upgraded torque converter with a new stall speed of 3,000 rpms (on good days I can get the rpms up to 3,300). That's at least 1,000 rpm difference! This equates to a launch from the part of the powerband where the power starts. This is especially helpful if you have a turbo charged vehicle. Launching from 3,000 rpms will help rid your launch of turbo lag, due your vehicle being in the rpm range where the turbo starts making power. Nitrous equipped vehicles can benefit from the higher stall also. The driver can squeeze during the power band where the rpms will help make more power instead of using the juice to launch the vehicle, which normally results in massive wheel spin off the line. An upgraded torque converter is usually good for .5 to a full second off of your ?mile ET. Your 60 foot time is improved as well. When upgrading a torque converter keep in mind that it should be matched to your motor's powerband and your upgrades. This is why going higher on the stall speed is not necessarily better. For the most part, 3,000 to 3,500 rpms is as high as you want to go on our cars. Any higher will affect your driveablity and total amount of power available to the wheels. Upgrading your torque converter will improve your ET as far as daily driving is concerned. I have found my car to be much more responsive in all driving conditions. My car has no problem getting in and out of traffic. I also found that gas milage is not affected if you don't drive with a lead foot. You can expect to pay anywhere from $400 to $600 for this modification less the install costs and shipping. An important extra if you do go with this mod, is an externally mounted automatic transmission fluid cooler.


Typical $25.00 Automatic Transmission Fluid Cooler
Heat is the cause of a lot of damaged automatics. An upgraded torque converter will add more heat due to the higher stall speed. Even if you don't have an upgraded torque converter, an externally mounted tranny cooler will help dissapate some of the heat and extending the life of your tranny. Good insurance if you ask me.Many of the SML and SBB members that have an automatic have installed tranny coolers. The coolers are universal and can be found in many national auto parts chain stores. The prices range from $25 to $100. I happen to have a $25 cooler and have yet to have any problems. I'm sure that the higher price you go, the better the cooling. Most of our automatic transmissions are equipped with a locking torque coverter, which makes the protection of the system even more important. I found some more technical information from Level 10 that will help emphasize my point.

Some torque converters have an internal, hydraulically operated "lockup clutch" in them. At some preset point, the transmission will cause this converter lockup clutch to engage in order to mechanically lock the input turbine and the output turbine together. This improves the vehicles efficiency a bit because the slight slippage between the input turbine and the output turbine is eliminated. As a side benefit, some "engine braking" is also available when you take your foot off the accelerator.

As with the rest of the transmission, excessive heat and contamination is what will kill a torque converter. Since the fluid in the torque converter is ATF supplied by the transmission, wear particles and/or bits and pieces of a blown-up transmission will end up in the converter, thereby destroying it. Changing the ATF at regular intervals and installing an external transmission cooler will lead to maximum torque converter life. If an in-radiator transmission cooler fails, ATF contamination with engine coolant will destroy a lockup torque converter.
-Level 10

The choice is yours, anything is better than the stock setup. The cooler the transmission fluid the smoother the shift. Lastly the cooler is an easy install. Next I will discuss another upgrade to the auto tranny.

A valve body kit a.k.a. "shift kit" can be added in place of a stock valve body. The kit is not a power adder but it will lessen the time between shifts (quicker shifts), which will lower ET's by laying more ponies on the track during the run. The valve body kit will allow throttle oriented shifts, which will tune to the driver. You can expect to pay anywhere from $400 to $700 for this mod. I currently do not have this upgrade but I do plan on swapping to this mod soon.

As far as maintainence is concerned, the Factory Service Manual (FSM) recommends the tranny fluid and filter (on some models) be checked every 3,000 miles and changed every 30,000 miles under normal driving conditions. If you have an upgraded torque converter, manual shift your vehicle often, powerbrake, or don't drive consistent with "normal driving conditions," I would start looking to change the fluid at around every 15,000 to 20,000 miles. As far as which brand tranny oil to use, I hear that Redline and Amzoil are good. I use Mobil 1 and have so for a while with no problems. I can't really say which oil to use. It's just important to keep an eye on your tranny fluid.

I only know of two companies that offer torque converters; Dunrite Converters is out of Southern California and Level 10 is out of New Jersey. My torque converter was done by Dunrite. Level 10 did an entire tranny upgrade on an NX2000 equipped with an SR20DET that was featured in a recent edition of SCC. Both companies are listed in the Vendors Listing on Sentra.Net. When calling either it is important to know your tranny code, which can be found on a information panel located inside the driver's side door. Also know your approximate stall speed. You will need a tach to get your stall speed. If your car is a daily driver, you may want to pay a visit to a local junkyard for another torque converter to send in as your core. This will prevent down time from having to send in your torque converter. A call to either company will aid you in which way to go. If you are a do-it-yourselfer and don't know your way around an automatic transmission, I suggest letting a good local tranny shop do the work. This will save you a lot of headaches! It's not brain surgery but you need to know what your doing. So that's it! There is light at the end of the tunnel (no it's not a train), for those of us with automatics. It does cost a bit but compared to an auto to manual swap, it may save you some money (unless you have a line on manual parts). So go give your car a hug because now you know that there is hope!
 

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Noob again!
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Hey Aaron, hows it going. Auto, standard, same thing. You'll kick some ass at the race circuit as long as you can drive properly. Haha, actually a person who doesn't know how to downshift properly (actually I'm still working at it) will screw themselves over in corners especially with rear wheel drive cars. Oops, I spun around again :grin:

Cool article.. just too long to read. Haha I'm lazy I know!

Bring your car to Shannonville next season. I want to see you guys burn some rubber. I'll be doing the same with my AE86.

Kevin
 

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Turbo-Yota power
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That almost gives me hope for my auto Camry ,only problem is sending in you trnny to level-ten to get it upgraded.I was able to find a tranny for 450$ but it had something like 20 000 miles on it,this might be a good idea if i want to keep my car and drive hard like i do.Thanx for posting this it might help me be motivated :smile:
 

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while on the topic of auto vs manual...

my and my friend were arguing whether or not an auto can keep up with a standard trans in accelerarion....

ex. if 2 integras (just for example sake...) drag-raced...1 auto, 1 standard...
if the auto integra started with his drive select in D1 (lowest gear) and held it till almost redlined, then pop it up to D2, until red line, and so on for D3 and D (regular drive gear) couldnt the auto integra keep up with the standard that is doing a similar thing (gear 1 till redline, gear 2 till redline, etc)

i understand that lotsa engine power is lost in runnin the auto trans...but would the auto lose by a lot? (I never tried...)
 

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the gear ratios between an auto/manual car are completely different... plus most auto trannies are missing a gear, so the ratios are further apart... meaning you have to comprimise more with the gearing.

the real advantage of having more gears is that you can place them closer so that you can stay in your optimal rev range for longer...

furthermore, force-shifting an auto is pretty pointless for acceleration anyway since the shifts will take a second or two... if you waited till the revs hit redline before moving the shifter you would probably bounce off the rev limiter. just keep it in drive and floor it and most auto cars will shift at redline in that case anyway...

now, downshifting in order to exit a corner - now THERE's where force shifting the tranny will actually help...
 

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so I guess manual would beat the auto by a substancial bit...

yah...I sometimes go into D2 on my Cam to help "downshift" on turns...

I dont think its so healthy for the car...
 

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well, if you think about it, when you're in overdrive and you really get on the gas, what does the car do? it downshifts... now, jumping down two gears is not as healthy, but it's not exactly going to leave your tranny lying in the middle of the road... at least i hope not... it's a japanese tranny, right? i've seen nissan auto trannies take tons of abuse like that... (not neutral drops though, those are stupid) and i don't believe that toyota ones would be any worse
 

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There is no substitute.
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By all means watch your speedo when you shift to D2, and try to brake to slow the car down before pulling the gear to 2nd.

But I think there's a protection from the computer that prevents you shift to D2 if the speed is too high anyway.
 

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yeah, don't rely on downshifting to slow you down, you have brakes for a reason... use them.

think about the stress that would be put on the tranny if you were at a speed which would put you on the top of 2nd while in 4th and did that... the revs would shoot to near redline from the bottom of the rev range within a short period (there's plenty of stress right there). if you look at professional drivers you see that they will never use downshifting as a way to slow down.

now, in an emergency situation (like a panic stop), i can understand, but definately not for recreational use.

don't downshift if you're not going slow enough already.
 

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The racers in SCCA solo II class always downshift. I go to alot of the races and often downshift when I want to bleed off a little speed. What I'm really after is a braking force without altering the traction limits on my front wheels. If I'm going into a corner and I tap the brakes, I get understeer...downshift and I get just a tad of oversteer.

Now I don't aggressively dirve any auto's...so I don't know about them. But downshifting is used in all forms of racing (just listen to the F1, CART, and WRC cars going into corners)
 

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yes, of course they downshift... you're slowing down, you don't want to be sitting right above stalling in a high gear! you need to match your current gear with your current speed and situation... however, they are still mainly relying on the brakes... by the time they're shifting down they're already going slow enough for that gear... i.e. no or little engine braking is happening... the main point of shifting down while braking is still to select the current gear, not to slow you down...

if you own an MT car and downshift for braking all the time, i can say 100% that your synchros will be shot sooner or later and you will start grinding into gears...
 

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for example, look at one of the most common techniques used for racing... the hell-and-toe.

what happens then?

first, you brake... then, you disengage the clutch and rev up the engine TO MATCH YOUR CURRENT SPEED, then you shift down and engage the clutch. all the slowing down is being done by the brakes, not the engine. minimal stress is put on the engine and tranny...

the most probable reason i can think of for your situation is because your brakes are applied more gradually than engine braking, which comes on with a bam, this shifting the weight of your car to the front and causing a hint of oversteer... if you "tap" the brakes, the weight distribution of the car is still mostly neutral and your car will do its natural tendancy, which is understeer...
 

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Obviously you shouldnt rely on the engine to slow you down (that much).
but the way I use my auto is like this:

say you are in the passing lane on local city road...you come behind a slow car in the passing lane.
now I sometimes downshift to D2 and the RPM does go up a bit, but no REDLINE...and I add some gas to maintain my speed (tailing this slow car), and as soon as there is enough space to pass this car in the right lane, I can do so with "more" power.

If I had approached this slow car in the passing lane, and then braked (slightly) to tail the car, and then slammed the gas when there is an opening in the right lane, it usually takes a second for the engine to downshift to give me a boost to cut in the right lane.

(no, Im not cutting anyone off...Im trying to get out of their way =P)
 
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