SC400 Performance

[miwise]

Hi, I'm new to this forum and have a question. Does anyone with an SC400 know about how good the performance of this car should be? I'm trying to compare the performance of my car with 210000 miles on it with others that have low or the same milage on them. Heres the question. . .should my car have enough power to make the rear tires bark (without power braking of course)? I have new timing belt, distributor cap and rotors, and iridium spark plugs installed. The car seems fast enough, but I just wanted to know if it should be better or not (regardless of milage). It is not my objective to do burn outs, I just want to know if it should be able to with fully stock setup (including tires and rims). Thanks!

 

[Lextreme II]

A performance torque converter will help alot. PI makes a very nice one for about $750 plus about $300-400 installation.

 

[miwise]

Will it affect the drivability or the fuel economy of the car? Does what I listed sound pretty close to what it should be? I have a 2002 Pontiac Grand Prix GT that seems about as fast, but I'm not timing it or anything. Never did any 1/4 mile trials or anything as I don't really like doing that kind of thing on public roads and the nearest track is in south louisiana. I probably need my transmission looked at anyways b/c it shifts hard when 3rd gear engages. All other gears are fine. I took it to a transmission shop and they said the transmission was fine, but sometimes from 30 to 40 mph, I can hear something below the gear shifter that sounds like clicking (almost like unlubricated gears). I changed the transmission filter and added a bottle of lucas transmission fix to it. It doesn't seem to have much power until the rpms get way up there. . .its average at low rpms.

 

[UZZ30-Québec]

your GP is not supercharged?

the lexus should be faster on highway. if it's supercharged, it should be equal, if not a little faster for the GP.

The SC400 is really NOT a fast car stock. and no, if you have good tires on it, traction control removed, you will have a hard time to make it spin.

if the engine received all services it needed for all those 210 000 miles, it should pull as good as brand new. Those engine are very strong against wear.

if not, take a compression test to be sure (or a leak down test)

 

[UZZ30-Québec]

It doesn't seem to have much power until the rpms get way up there. . .its average at low rpms.

that's because it,s only a 4.0 liter engine, and because the torque converter's stall speed is too low. You must not forgive that this powertrain was built to be the smoothest possible (smoothess? smoothness? sorry my english is not perfect)

 

[Toysrme]

Torque converters don't normally drop the mpg aslong as they're still lock-up. As with many mods, people are prone to driving abit harder for awhile just to get the thrill of their money.
I agree with David. Short of n2o, nothing will cut a 0-60, or 1/4 mile time faster than a descent torque converter. It's most of the difference between an automatic that launches poorly, and any manual that can have an aggressive launch. That & a valve body upgrade are the quick time dropping goodies.
There are alot of places that make torque converters. Level10, IPT, PI's Dragon's. They all run roughly $500-1000 for a custom rebuild, to a replacement. lex youve made our TC's for $200, whats the deal with the v8's?




I advise cleaning the throttlebody, upper intake & running something like water injection, or seafoam to clean the carbon out of the cumbustion chambers. You'd be amazed at how much better it can be VS what it is.

 

[jibbby]

The SC400's are simply slugs at stock and down right embarrasing from takeoffs and or from a launch...An upgraded torque converter would be the first chioce in mods if I were to do it all over again.....Then Exhaust mods, ECU piggy back, Intake, turbo, nos, jet engine swap, etc......

Just kidding with the jet engine swap....:happysad:

 

[miwise]

These are some great recommendations! I will start looking for a new torque converter. I did know that lexus is known for their smooth powertrain and burning rubber or winning races isn't really my thing. I just want it to run right. I will be redoing the tranny pretty soon most likely so I'm going to look around for a torque converter. I really don't want mine rebuilt. I'd prefer a brand new one. The main problem is that the third gear engages very harshly at moderate acceleration, but smoother (but still not like the other gears) at hard acceleration and very light acceleration. I think the valve body will have to be removed. . .something I'll let someone else tackle b/c I'm afraid of messing something up. Thanks again for all the help. Very insightful! This board is a diamond in the rough; I'm glad I found it!

BTW, Anyone know where I can find a good price on a new torque converter as mentioned above? lextreme mentioned PI, but I don't know what that is. I'll probably be looking for one in about another month b/c I just got finished having the car repainted (diamond pearl white is very expensive). Thanks!

 

[Lextreme II]

The best price on a brand new PI torque converter would be http://www.luxurymods.com However for the best bang for the bucks would be http://www.lextreme.com/tc.html

 

[miwise]

So, this rebuilt converter is at least as strong as a new one and will handle stock power well? I'm always hesitant to buy used or rebuilt items, but the price is a lot better than a new converter. Besides the reset stall speed, how does the rebuilt one compare to a brand new lexus converter? are they reliable?

 

[Lextreme II]

I think the a brand new Lexus OEM torque converter will cost over $1,000+. Here is an honest post about our TC

 

[miwise]

Great post. I'll most likely be getting back with your company at the middle to end of october for the converter. Sounds good. Do you know if borla makes a catback system for this car?

 

[jibbby]

The - Precisions Industries "Dragon Torque Converter" is what I have been running on my SC4 for 3 years now...I think it is just made perfect for our SC400's...The stall rate is excellent...No problems to report and it has been handling 300whp for 3 year duration with no ill effects....Nos too, which is more jolting to the drivetrain then any other form of forced air induction...(like turbo's and superchargers)

$900 is what I paid for with the Dragon Torque converter new...It will wake up your SC.....

 

[miwise]

Thanks for the replies! I can't wait until I get me a new torque converter. Sounds like it should help a lot.

 

[miwise]

I have one other question. I have this vibration that seems to just about go away after the car warms up. What could cause this? Someone has suggested motor mounts, but wouldn't it vibrate the same all the time if it were the mounts?

 

[jibbby]

motor mounts and transmission mounts wear out on these older high mileage lexus....Check the mounts...

 

[UZZ30-Québec]

I have one other question. I have this vibration that seems to just about go away after the car warms up. What could cause this? Someone has suggested motor mounts, but wouldn't it vibrate the same all the time if it were the mounts?

I have exactly the same problem.

 

[miwise]

does yours happen in park as well as when in gear? Mine does. It occurs from about 1000rpm to 2000 rpm or more. Its almost like a harmonic vibration. It would seem to me that it would do it all the time if it were the motor mounts, or am I wrong? Are the motor mounts warming up with the car causing the engine to be cushioned better when warm? Also, it seems to vibrate the worst in the early morning right after first starting the car. Does it for a while (about 10 miles). Never goes away, but gets less intense as the car warms.

Also, can motor mounts make noise while I'm traveling down the road? My car rattles a bit below the cup holder when letting off the gas or coasting (but not when I totally let off the gas). Also, b/w 25 and 35 there is a clicking noise almost like gears meshing together as they turn. Could this be part of it? Does the torque converter turn while the car is in park?

 

[UZZ30-Québec]

yes, the vibrations are exactly the same as yours, when the engine is cold.

I also have a little engine vibration when i release the gas on highway cruises.

The torque converter always turns when the engine turns since it's bolted to the flywheel wich is bolted directly on the engine crankshaft.

 

[miwise]

how does your transmission fluid look like? You can see what mine looked like. It needs changing, but I haven't had time to do it yet. I took this sample a little more than a week ago. Is yours like this or blood red? I've been told its my motor mounts and will probably have them changed next month (just had a dent repaired that cost 1500 dollars and can't afford right now). Other than that, I was thinking it could be the torque converter maybe since my fluid was so brown looking.