JBrady

Been promising my GF that I would take her to the track. So, despite a strong headwind and a mediocre barometer... we went. True to form she made us late and barely had time to make a pass before brackets started. First pass off the highway was a new best of 14.78 followed by a 14.73 on my first, winning, bracket pass. This was plenty to put away a modified, strong running Lincoln Mark VIII.

I adjusted my dial in and promptly nudged it with a 14.691 @ 95.50mph. This was plenty fast to dispatch a 70 Nova running a 5.7 liter (350cid for us old timers) with headers and a Holley 4 barrel carb

The next pass I encountered SEVERE wheelspin. Up to this point wheelspin had not been happening. I had to change lanes and I think the tires are getting hard. Tried again and same problem only worse. Oh well, just damn happy to have a 14.6. BTW, the only change was I pulled out the spare and extra junk from the trunk. Best mph of the night was also a new best of 95.82.

LOTC

Nice time Jbrady, time to change your sig again I believe

BTW has is the exhausts project coming along? Keep us posted on any updates.

retrodrive

Wow...getting really good at this man. Do you run stock wheels? My milage went up by 75 miles per gas tank by swapping out my stock wheels for my 19's. That is how heavy stock wheels are! Gotta get some centerline wheels which weight nothing.

JBrady

Thanks Dogg and Retro.

Regarding the wheels... yes they are the stock 5 spoke, yes they are heavy, yes it would help to run a lighter wheel/tire package, no I am not planning to change them anytime soon... sorry to all who HATE stock stuff

SilverFlare asked my in a PM about limited slip differentials (LSDs)and launch technique. I thought they were good questions and answering here should help others with similar interests.

LSD provides engine torque to both rear tires instead of just one as the factory differential does. In all but a standing start this is a non-issue. If you have a hard time getting traction then a LSD will help. Powering out of turns with an LSD requires a different technique than with an open diff. There is also the concern about compatibility with the VSC/traction control on vehicles so equiped. See the last of this post for my personal experience.

As for launch technique and 0-60 times... I stage the car then powerbrake to aproximately 2200-2300rpm, let off the brake and floor the throttle on green. I say approximately because I am watching the tree and not the tach. I try to "feel" the car struggling just below tire spin. This is giving me consistent 2.25 second 60 foot times. Not great but better than the 2.35 it was doing. From there I just leave it in "D" and let the transmission shift itself. I have tried manual shifting and if I nail it I can get a very slight improvement but it requires shifting a good 500rpm prior to the intended point. For me that "goal" is 6200rpm so I move the shifter at 5600rpm, that is how long it takes to respond at full throttle in 1st gear. 1 to 2 shift happens around 43mph, 2 to 3 is around 63mph (just over 100kph) and I go through the lights at 6100rpm in 3rd gear at an indicated 101mph. For those unfamiliar, dragstrip MPH is an average speed over the last 66 feet of the track so it is an average of that speed, actual MPH at the finish line is higher than displayed on the time slip.

Previously I was able to just powerbrake and go with almost no wheelspin. Last night I was getting more spin that resulted in wheel hop on launch. The last 2 attempts I made resulted in uncontrolled spin. This is the result of several things: slightly higher launch rpm, worn and hard rear tires, less weight in trunk after removing spare and jack, better air making more power. Spinning the tires KILLS elapsed time and resulted in a 15.4 and a 15.8 respectively. A LSD would definitely help traction but is a LOT of money for minimal needs. I just need a stickier tire. A new one is probably fine. The LS400 from 1995 through current has a 3.26 to 1 axle ratio. This is a good compromise between performance and economy for our cars and as seen in the speed in gears above is about perfect for both 0-60 and 1/4 mile in our cars. Now, if you change out the torque converter a LSD may become much MORE interesting

JBrady

Here is my time slip. Conditions were OK with a strong headwind costing some performance both on ET and MPH. The barometer was slightly low at 29.70 inches. Air temp was apx 77 degrees.

My car is #185 in the right lane. The "victim" was the Nova

SilverFlare

jbrady

Thanks for all the explantions on those issues, all of sudden, I feel I got so many things need to learn.

Another thing is the techinque of powerbrake, like u said, just shift to D in stead of doing manual shift? I thought manual shift it's always the fast cuz I always shift from 2nd .. hwer I will try it later.


retrodrive
gas mileges went up to 75 miles .. what a great news... now I felt regret that I got the SC wheels, as my LS is already about 350 miles full tank.. btw ur car just look elegant .. congratulation to the new 19" ....

retrodrive

Thx, I might change the front bumper sometime soon though...maybe make it a little more agressive

JBrady

Well, I posted my times in the GS section as the engine, tranny and gearing is shared on cars that are within 200lbs of each other. Some good posts were generated by GS owners until someone decided to MOVE my post from the LS forum

Anyway, here is the post with some good stuff including a 175hp port injected nitrous setup on a GS.

https://www.clublexus.com/forums/sho...threadid=59113

LOTC

How much can a LSD and TC cut down on the 1/4 time? maybe 0.5 sec. or is that too much?

I will move this thread back into the GS section.

JBrady

E... thanks.

Regarding LSD and 1/4 mile times... an LSD will give a car 2 tires instead of one in which to transfer power to the road surface. The difference in time is very much driver dependent but a skilled driver could easily shave .2 off the 60 foot time and that should be about .3 in the 1/4. Now, that is with the SAME gearing. With more aggressive gearing the car will be placing MORE torque to the ground in each gear with each gear running out quicker. On my LS400 that would mean a shift from 3-4 gear before the 1/4. It now goes through the lights at 6000rpm in 3rd. Still, it would be quicker in each gear but whether or not the 1/4 would be improved would require real world testing or a sophisticated software program and accurate data imput.

Now, as I develope more power the car would be shifting anyway so the gears would definitely lower my ETs. Another HUGE consideration is suspension reaction at the line. I was experiencing wheel hop (tires start to spin, grab, release, grab) at the limit of traction. This indicates the suspension does NOT like max power launches. Other things come into play including drag radials (tires that work MUCH better for drag racing but can still be used daily). LSD + drag radials could easily put a Lexus in the 1.9 second 60 foot range. That is about 3-4 tenths quicker than otherwise and translates into 5-7 tenths quicker ETs. Add in another 2 tenths or so for the gears and you are looking at up to a second quicker with stock power