The Silver Buick's well Silver Buick!

[TheSilverBuick]

Been thinking of running different rims, but to be swapable with the Firebird I need to convert the car back to a 5 x 4.75" wheel bolt pattern and that requires getting new brake rotors. The rears are easy as I can just get the '79 Trans Am disc's and my axles are already drilled out for the 4.75" bolt pattern so I just have to move the screw in studs. The fronts were a bit trickier since I need a 12" rotor and the smaller bolt pattern. The early 90's Camaro's with the 1LE option had 12" rotors with the smaller pattern and hopefully with just a bearing, and possible race, change to a Set 34 outer bearing they'll slide right on. I've looked at them a few times over the years and at nearly $90 a rotor I wasn't in any rush to go get them, but I found them on Amazon today for $34 each, so a pair are on their way and after shipping were still cheaper than one rotor from Autozone or NAPA I'll get the rears down the road when I'm actually ready to swap tires around.

I want to see if the OE rally rims I have for the Firebird will fit on the disc brake conversion done to the Firebird (my first Firebird had disc brakes and OE rally's), and if so I'll look at putting them on the Firebird and that way I can use the lighter rims on the Skylark for taking it to the track.

[TheSilverBuick]

Did some general maintenance to the Skylark today. I knew the fan clutch was on the way out during Drag Week last year when the coolant temp climbed to something like 210ºF in stop and go traffic when it wasn't even that hot out (compared to ~115º+F in Vegas without issues). I tried to get a warranty swap on it at two different Autozones but they seemed to have lost my warranty info on it. Which is odd because I did a warranty swap on it in 2009 or 2010 when I went to Arizona for the Car Craft Anti-Tour and that one seized up on me. Anyways going into winter I didn't worry too much about it but last week it started to squeak. It didn't have any wobble or play in it, but spinning it with my hand generated a definite chirp. I don't need to lose a radiator so I got a new one from Autozone.

Autozone seems to have changed suppliers and I have to say I like the look of the new design. Even stamped "Made in USA" for a bonus. The "broken" fan clutch had little resistance to while spinning, even when hot. I can definitely feel the air being pulled from in front of the car again with the new one.


I guess I had never noticed how small the fan on my Skylark is, five blades with relatively short blades. I've never had a cooling issue with it, such as stop and go traffic in Las Vegas at 115º+F, etc. but I do have a 7-blade fan on hand... I ended up staying with the 5-blade because there was a slight interference with the mounting tabs on the new clutch and the 7-blade fan. A quick filing on two spots would cover it, but figured if the 5-blade fan has always worked, it'll likely continue to work.




I also messed with some of the launch control and traction control settings. It sounds a bit cleaner now on the 2-step and I still need to try the traction control settings. I have the traction control settings set to a "perfect run" so it starts a timer after the clutch is lifted and the wheel speed shouldn't exceed certain amounts by certain time, because if it is it is likely due to tire slip. I've calibrated it to my best runs to date and then added a few mph to leave room for improvements.

[TheSilverBuick]

Thought I'd take some time today to install a hall sensor on the front right wheel to hopefully help me launch the car off the line. The premise is I have a vehicle speed sensor on the transmission letting the Mega Squirt know how fast the rear wheels are turning, and by adding a wheel speed sensor to one of the "un-powered" front wheels the Mega Squirt can compare the two and if the rear wheels are turning faster than the fronts by a programmed amount over a programmed period of time, then it starts pulling timing by programmed amounts. Pulling timing (to as low as 0º) effectively kills the horsepower production of the engine, but it'll pull it and give it back as fast as needed to keep the two wheels spinning at nearly the same rate. Basically it'll allow a ~5-10% slip differential so the rear wheels can be turning slightly faster than the fronts to keep acceleration going.

Many folks have been having luck running the sensor in the brake backing plate or on a bracket and reading the backside of the wheel studs, but it looked like to me the wheel studs on my car don't stick out far enough to get a reliable signal (I didn't actually try..). But I did notice there was a casted lug between each stud, and I checked another rotor I have on the shelf and it had the same casting, so hopefully it's a reliable feature to use if I change rotors down the road. What I needed to do though is bend the backing plate a bit to angle for the lug. That was simple enough just used a cut off wheel to make a tabbed section, bent it, then put a couple spot welds at the joint to stiffen it back up. Drilled a hole in the tab and welded one of the sensor nuts to the tab so the sensor threads in and the second nut becomes a jam nut.


A while ago I started getting away from using the corrugated wire covering, but figured this is a good place to use it to protect the wires. I trimmed out a small plate to hole the wiring in place and used the extra threads from one of the bolts on the ball joint to secure it.



Here is a short video of me testing the sensor before finishing the wiring up.

[TheSilverBuick]

Seems to be consistent with the transmission sensor. It drops out when I hit bumps in the road or slow down abruptly, so need to figure out if it's my wiring (always suspect!), the bracket is wobbly, the sensor clearance, or a filtering setting. I have the traction control currently turned off and did a test of spinning up the rear wheels on the dirt road coming into work just to watch the difference. The smaller number is the front wheel.

[TheSilverBuick]

It drops out when I hit bumps in the road or slow down abruptly, so need to figure out if it's my wiring (always suspect!), the bracket is wobbly, the sensor clearance, or a filtering setting.

I think I found the issue. I had one wire pull out of a connector, and another one that didn't take much to make it the same. Tomorrow I find out if I did a better job this time.

[TheSilverBuick]

Finally turned the traction control on for some testing. No significant speed testing but tried five or six burnouts and datalogged two of them. It's a weird feeling, it's not missing like a rev limiter cutting spark but you can certainly feel the power being pulled down, softly. I datalogged the most extreme case which is sitting on the 2-step limiter and just dumping the clutch, which usually sends the tires up in smoke and the rpm's to the moon. One caveat to this though, I didn't try laying the pedal to the floor due to where I was driving, but in a normal circumstance, that throttle position should of produced a much much longer burnout.

I annotated the datalog a bit. I have a minimum threshold of 5mph set so it won't do anything until the car is over 5mph, and once there traction has to be over 5% different (check), and it took 0.21 seconds after the first reading above 5mph for the timing to be pulled down to 11.5º. I have just some guesstimate numbers plugged in, so I'll probably pull the timing down faster and lower. I have some noise in the rear wheel speed sensor when I'm on the 2-step, so until I cure that I can't really lower the 5mph minimum threshold. Overall, I'm glad that it's doing SOMETHING and can work from that baseline. It was just under 0.4 seconds between the rear tires spinning and the front tire registering speed, then another 0.21 seconds before the traction control kicked in, and ignition timing was reduced for 1.45 seconds.

[TheSilverBuick]

Went out and did another couple tests, this time a bit more aggressive on the throttle to highlight what its doing. I let it pull a lot more timing, but I didn't change the reaction time aggressiveness of it. What it shows a lot more clearly this time is me pushing the throttle down more, but the rpm's are falling anyways as the traction control as pulled timing down around 5º to kill off the horsepower. Then when the wheel speed is in the acceptable 5% difference range it gives the timing back, which accelerated the car and I lifted for a second, then put the throttle back down, causing it to break traction again and re-activate the traction control measures.

By the numbers, 0.38 seconds between the rear wheels spinning and the first movement of the front wheels, 0.207 seconds of front wheel movement before timing get's pulled down, timing is reduced for 1.257 seconds before front and rear wheel speeds are within 5% of each other.

More fine tuning to be done, but it looks like if I don't just dump the clutch off the 2-step (which I haven't been at the track) and can get the car rolling just a bit before putting the pedal down, it should do what it's supposed to and let the car accelerate while still allowing an acceptable amount of slip off the line (currently set at 5%).

[Russell]

So that's 1.844 total, any clue how far you went? Think it was 60'?

[TheSilverBuick]

I ballpark about 30 feet based on average speed and time from the datalog (too forgetful to do true calculus), a car length and a half. Taking the whole log into account, it was right around 2.3 second 60ft (right at the rpm peak). Again, this wasn't at WOT, and this is street tires on the street. I typically run in the 1.90-2.0 range on the track. I think easing the clutch out to get the car rolling then putting the pedal to the floor is going to be the way to go.

[Russell]

Wonder if you could use the input from the front wheel. Put a formula in the MS and let it calulate the distance. The big question is what is the tire roll out and does it stay the same?

[TheSilverBuick]

The tire roll out is programmed into MS to calculate the speed, and I'm sure it changes as last year at Drag Week I definitely saw differences of my reported speed versus time slip, yet on the highway it matched the GPS. I'm sure I could dump the time and VSS data into Excel and run a derivative formula on it to get true distance (to the accuracy of the sensor recordings). Now that I think about it, the MS does have the option to record distance, I should probably turn it on and see if it works. I know it works fine with the laptop plugged in, not sure about recording to the on board SD card, which these logs are taken from.

[hauen]

I remember reading in one of the hot rodding mags years ago that 15% was the optimum amount of slippage for acceleration (in a straight line). I don't know if it's still true or if that was with all tires or not. I'm sure with a little more research and your attention to detail you could science it out rather handily in short order. I almost expect to see you build an MSGPIO and build your own TC/ABS/RSC at some point, which would be awesome, quite frankly.

[TheSilverBuick]

Newer tire compounds and such, I think as little as possible is best, but 15% is probably the max you really want to see. From what I gather, bias ply tires work best with a little slip off the line, but drag radials want to simply hook and go. I'm sure there is a wide grey area with both types. I also don't make "that much" horsepower compared to 99% of the folks that really utilize these features. I'm just trying to crutch my manual transmission launch technique and be more aggressive with it.

[TheSilverBuick]

I did a short test run out on an empty road outside of town on the way to work. Instead of dumping the clutch of the 2-step limiter I started with getting the car rolling a bit before putting the gas pedal down and it seemed to work pretty well. Ran it up to 5800rpm in first at 85% throttle and progressively less in each gear afterwards. You can see a few places in 1st gear where traction started slipping again but it doesn't pull as much timing because the slip percentage isn't as drastic as it is off the line, and again going into 2nd gear. I think I'll raise the acceptable slip percentage up to 10%.

I have the "Flat-shift" option turned on, where I shouldn't have to lift the throttle to shift and it'll automatically cut fuel/spark with the clutch pedal, but I haven't been brave enough to try it out yet with the engine wound up to 5,800rpm, it gives me shivers to think if it doesn't kick on what the rpm's would climb too. I should probably set it for a much lower rpm to really test it out.

[TheSilverBuick]

Not a whole lot going on other than driving it regularly. What do you do when the wife has the truck and need to make a run to the dump? Hook up the Drag Week trailer and take care of business!



I don't have a car project thread for my '72 Centurion, mostly because it just languishes and slowly gets worse, but it's still a great car to go cruising around town in during the summer. This week I finally decided to dust it off and pull it out. It's just a reliable peach of a car though too. Put the battery charger on it over night, even though the lights still came on when the doors were opened I figured the battery was likely low after being parked for 9-10 months, then the checked the fluids and all were still topped off and looked clean, so put just a splash of gas on the top side of the Q-jet and it fired right up. Settled into an easy high idle which I let run for 3 minutes or so and gave the throttle a quick tap and the idle dropped easily to ~700rpm and it just runs like a Swiss watch.


Decided to take a cruise across this small town and go out to dinner.


The wife says riding around in it makes her feel like a Hollywood celebrity And true to form, despite what it actually looks like, in the five minute drive had one guy compliment the car while sitting at a stop light. After dinner, and sunset, it was still about 70ºF out so we made a loop around town just enjoying the experience. Some day I'll sand it down and do the body work it needs, as well as repair the rear window guides and a half a dozen other things it really could use. Bought it for $2500 with a blown up engine, rebuilt an engine for it, and installed a new top on it, and that is really all I've done to it in the last 15 years. Drove it daily through most of college and a few years after.