Note: I originally posted this over on the 500E.com forum. It includes a report from three separate days at Firebird Raceway in Boise, ID. The link to that thread is here

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August 28th, 2004:
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I just got back from my first night at the track. Overall I'd say it went very well! I had no idea what to do and just kind of followed the crowd, and luckily figured it out fairly quick. Only bad news was a couple cars had failures that put liquid on the track, requiring lengthy cleanup times. So I only got four runs in five hours (ugh). This had a side benefit of allowing *plenty* of engine cooling time between runs. I ran the car in 100% street trim, including spare tire in the trunk, and 35psi in the tires. The reserve light came on 10 miles prior to reaching the track so I had about 4 gallons of 92 octane pump gas in there. Track elevation is somewhere around 2400-2600 feet (need to bring my GPS next time).

So, what you've all been waiting for - howdiddit do? Well.... not too shabby! First two runs were in 75-80F ambient temps and were within a hundredth of each other - 14.47 @97.11, followed by a 14.46 @ 97.75. I think I left the ASR on for the first run and turned it off after that.

I had a long wait for the third run and the engine was plenty cool - 50-60C - by the time I staged. Ambients had dropped to 65-70F and the sun had set. I had not messed with burnouts at all but this time tried a little one ahead of the water box - didn't want to mess with wet tires. (The track recommends NOT using the water box with street tires at all.) I'm not even sure if the tires spun or not. Anyway the third run was great, just the right amount of wheelspin at launch, and nailed a 14.28 @ 98.47! I was pretty stoked about that. I was THIS close to getting entry into the coveted '100 MPH Club'.

For the last run, after another loooong wait, the ambient temps were down to about 60F. I could smell the 100.00 in the cool air. I did another short/weak burnout ahead of the water box - this may have been my downfall, I'm not sure. I think the tires got too cold and with the sun gone, the track temps were probably lower too. At launch one or both tires started to light up and I think they spun for half of first gear, d'oh. The cold temps and cool engine made for one HELL of a trap speed even with the abysmal launch... 14.87 @ 97.40. That was better than my first trap speed despite being FOUR TENTHS slower! Sheesh.

For the record, the performance mods on my car at present are:

1) Silver Carbon high-volume airbox
2) 1992 'Euro' LH module (WOT enrichment, +7hp)
3) Resonator replaced with 'Y' pipe (30lb savings?)
4) Remus muffler (sounds nice, probably no power gain)
5) B/W ASR defeat and FGS kit (both enabled at the track)
6) Trunk ICE adds about 75lbs (?) weight penalty

Also, I ran with the lower engine splash/sound shield removed. IMO, this allows better "convection" when parked with the hood open, allowing cool air to enter more easily from underneath as hot air escapes out the top. I'd want this shield in place for aerodynamic reasons over ~100mph on the freeway, but at the strip I think it's probably happier with it removed.

Comments / Observations:

1) Dammit - I think I'm hooked. (Damn you, Gerry!)

2) Going back next weekend, I hope... minus the spare tire, with the lighter stock wheels/tires mounted, 20psi in the rear, no subwoofer in the trunk, no rear seats, and 94 octane (or better) race gas in the tank. Considering yanking one of the headlights to provide ram air intake.

3) Firebird Raceway gives out decals if you break 100mph (and 110, 120, etc) and I really need to get one of them. AND, they post the list of 'club' members on their website, where there is a conspicuous lack of ANY Mercedes... something I'd like to rectify.

4) I saw a lot of cars that were a whopping 0.5-1.0 seconds quicker than my 500, but had trap speeds right around 100... damn, they must be getting out of the hole HARD. (And not have much for the other end.)

5) There was a Viper SRT with NOS and a license plate that said "MY VIGRA". It was running, IIRC, low 11's at 120-something. (Update: 2 weeks later I saw it run an 11.08 @ 129.xx! Wow.)

6) There was a Mustang Cobra with a supercharger (stock!) with minor mods - race tires, etc - that was running insanely fast high 11's. Wow.

7) Firebird requires helmets at 13.99 and faster, and roll cages at 11.99 & faster - changing to 11.49 & faster for next year, I'm told. So Gerry's car would be safe to run here on the bottle. (My car is slow enough that they even allow passengers. :p )

8) I ran my AP-22 computer for all 4 runs, and the G-Tech for the last three (forgot to start it for the first one). I'm still digesting that data and will post it in the 'G-Tech' thread elsewhere on the forum. Short version - the G-Tech was consistently 2-3mph optimistic while being very close on the ET's. The AP-22 was at first pessimistic but after I started messing with the adjustments it was getting really, REALLY close - I need another half-dozen runs to dial it in fully. Check the other thread for more details if you're interested in more (ETA- tomorrow or Monday.)

9) I will upload an Excel spreadsheet with my complete timing data, track conditions, notes, etc as well. Oh yeah, 60' times were in the 2.2-2.4 range.

10) I'm thinking my 'low power' issue may not be as bad as I originally thought, although I still find it very odd that on the street the car won't spin the tires. I am getting an intermittent idle miss that is VERY annoying which I can't trace down (separate thread).

11) This was basically just timed runs, no actual bracket racing. You could get in line near someone and tell the starter you wanted to race him or her ('grudge match'), but that's it. Which was just fine with me.

12) They ran three 'classes' - 14.0 and slower, 13.99 and faster, and streetbikes. So by default I was one of the faster cars of my group. There were a handful of people in the 16-18sec range with mostly stock cars.

13) There was ONE other Mercedes. An older gentleman with a leased 2001 E320, running it bone stock other than yanking the air filters. He bracket races and was only there to work on his reaction times. He got one red light at -0.003 which he was happy about, means he's right close to where he wants to be. His car was running 16.2 at 80-something. I kinda hung around him since he was willing to share his knowledge on how things work at the track. Really nice guy! (His W210 was silver too, btw.)

14) My first 'race' was against a Chevelle 396 SS, who beat me out of the hole, but around half track I started slowly walking by (just like Gerry said). He ran a 14.61 @ 93.15. Second race was a ricer, something or other SE Type R, I think? He probably thought he'd school grandpa's sedan as he came up afterwards with "Hey, great race, what did you do to that thing?" His time was 14.68 @ 93.28. BOTH of those cars beat my 60' time by a full two tenths. Third time was forgettable, he ran 15.69 @ 87.84, and was slower than me at launch - maybe he spun the tires or bogged. Last race was screwed up - we both staged, then the other guy redlighted without launching, then only my half of the tree started (which confused me), and I went down the strip solo after an embarassing RT of 0.727 and a crappy launch. Oh well.

15) The car seems strong with the engine cool (60C) but I still think it loses a lot when at normal operating temp (85-90C). I wonder if that's how they all are, or if I have a sensor out of spec or something? Or if it's somehow related to my hot idle misfire problem. (Fuel octane & spark retardation does NOT seem to be the issue, btw.)

16) Firebird has a huge area at the end, no need to brake quickly. Seems like another 1/4 mile to the return road. Plenty of time to coast down.

17) The burnout area is REALLY short/small at Firebird! I should take a photo (or see if they have one at their website). If I try to stay out of the waterbox I'm practically staged, sheesh... guess I just need to learn how to deal with that.

18) Snow chain switch: RENNtech said to use it on their 600E to improve the launch. I want to experiment on wet pavement sometime and see exactly what it does. I believe it disables the ASR at first, but then re-enables it when the tires reach about 20-25mph. (??) Theortically, it should allow a great launch, and may prevent the 'smoke the tire halfway down the strip' problem from the lack of LSD, in case one tire breaks loose and 'runs away'. (???)

19) Static or adhesive numbers are a must - using the 'shoe polish' white marking liquid is a PITA!

Data files (Excel spreadsheet with complete timing light data, and text file with full AP-22 data) are at this link:
http://www.meimann.com/docs/dragstrip/

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

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September 3rd, 2004
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Preparation: I went back in search of the elusive 100mph trap speed. In preparation, I removed as much weight as reasonably feasible:

Spare tire, lid, carpet, and tool kit (58.0 lbs.)
Owner's manual packet (2.0 lbs.)
Rear seat bottom cushions (21.0 lbs.)
Factory rubber (all weather) floor mats (16.0 lbs!!)
Subwoofer and fabric cover (19.5 lbs.)
Swapped fat 18" wheels for stock wheels & tires (26.0 lbs total)
Splash/sound shield below engine (5.0 lbs)

All totaled, that added up to 142.5 pounds less weight - wow. But, I added 4 gallons of fuel (32 lbs) when I had probably only used two last time, so that may have added ~16lbs, so my estimated net weight change compared to my previous dragstrip runs was 126.5 lbs. Still an impressive weight loss. The smaller/lighter wheels & tires have the additional benefit of less gyroscopic forces - they take less power to get into motion. I pulled the front turn signals out, since there is a hole that runs straight into the airbox behind, to create sort of a ram-air effect... grasping at straws, I know, but hey it can't hurt. I increased the front tire pressure up to 40psi; and dropped the rear tire pressure to ~21psi.


Track Conditions: Sunny and COOL! About 70-75F to start with, ending in the mid/upper 60's - great weather. Well, except for that damned wind - a steady 5-10mph with gusts of 15+, absolutely straight on against the cars going down the track. Ugh. I am convinced that cost me my coveted 100MPH Club decals. BTW - my GPS says the track is at 2700 feet above sea level.

Time Trial Report: I got three practice runs over an hour apart. For each, I shut off ASR and did a short burnout just in front of the water box. Then I turned the ASR back on (yes, ON) and engaged the snow chain switch. The first three runs went well - good launch, no excess wheelspin, decent reaction times (compared to my first night anyway). It was cool and windy so the engine cooled off VERY well between runs - 50-60C on the dash gauge when I got to the end of the staging lane.


Race Report: This was actual bracket racing. I was to estimate my time from the practice runs, and give that as a "dial in" time. I dialed in at 0.03 quicker than my best so far and hoped I wouldn't break out. Lined up, did a short (one wheel, grrrr...) burnout, and hoped for the best. The launch was mediocre - wheelspin started, but the ASR kicked in at around 20-25mph to keep it from 'getting away' like it would with the ASR disabled. My 60' times show that wasn't bad at all - almost the same as my first run with no wheelspin! The PROBLEM appeared at the 1-2 upshift. I'm not sure what happened. It felt like the tranny forgot to shift, hesitated an instant, then BANGED the upshift complete with tire chirp. Of course all it takes is a couple tenths and I was toast. I was 0.260 slower than my dial in and lost - meaning I had to go home. Of course, the guy I was running against (in a slower car) happened to be a Gold Cup champ and was using my class for extra practice. He ran 0.007 slower than his dial, AND cut a 0.062 reaction time - a complete pro! D'oh. Had I been against another amateur, I might have won and gotten another run, as the sun was just setting and ambient temps were about to dip into the 50's in another hour.

The Times:
Run 1: 14.212 99.54
Run 2: 14.191 99.32
Run 3: 14.089 99.31
Run 4: 14.314 99.21

Note the first/slowest run had the best trap speed. The last run was the one where the tranny screwed up, AND spun at launch, yet still managed an impressive trap speed. Full run data from the time slip is in the screen shot below, along with the AP-22 data in the second screen shot. The AP-22 was DEAD NUTS ACCURATE, whoo, I'm impressed with that thing.


Next Time:
** RENNtech chip to be installed
** Ice the airbox!
** Pray for a 10mph TAIL wind
** Change trans fluid and install Mobil-1 synthetic ATF (been meaning to do this anyway)

Must... get... into... 100MPH Club!!

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September 11th, 2004
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I went back again last night and the results were disappointing. I had almost the same setup as before (no spare tire, etc) except this time I had a RENNtech EPROM chip installed. I lowered the tire pressure a tad more and tried icing the airbox for the first few runs (seemed to be little to no help). Last time I was eight hundreths away from the 13's, and 0.5mph away from 100mph, so I figured I should be in like Flynn with a few extra ponies from RENNtech. Right? Wrong. Read on:


The Good: Well, there wasn't much good really, other than the runs were all consistent. And, if you examine the data closely (both the strip times and the AP-22 data), it seems I was launching harder and getting out of the hole better - higher G-forces registered on the AP-22, and a couple of my 60' times were really good. The car seemed at least equal to last time, for the first 1/8 mile, anyway. I adjusted my tire pressure to 21L and 19R, which seemed to help a bit - I had good hookups at launch and I don't think (?) the ASR ever engaged (I used the snow chain switch for all runs).

First race was against an old Jaguar with DOT drag radials. That thing was FAST! He beat me soundly with a 13.557 @ 101.47. Funny part was at the end of the strip, he either misjudged braking distances, or his brakes faded, 'cause he went straight into the weeds...! Oooops. He drove out of the dirt and seemed OK other than maybe a little embarrased, heh-heh. His 60' time was excellent (1.975) and at 330' he had a 0.4 second advantage which slowly widened. Next three races were forgettable (three wins). The last race was great. I was first in line when they called my group and I happened to be next to a late model Firebird. I got a great launch (0.140 RT to his 0.306) but he was about one length behind me the WHOLE way down the strip! I had him at 1/8 mile, but he was quicker to 1000', and nipped me at the lights - his 14.129 @ 103.04, to my 14.266 @ 98.68. Fun part was, at the lights he was just pulling past me, and neither one of us let off the gas! We both kept it pinned probably to 110mph, several hundred feet past the lights. Damn that was fun. And it was the first car I've raced that was pulling on ME at the lights! (I think the Jag would have run out of steam shortly - not sure though.) Usually the 500 might get beat out of the box (like the Jag did) but I catch up at the other end. This thing was HAULING! Even better, although my time was slower, I got the tehcnical "win" because his RT was slow enough to erase the ET advantage, so I got the flashing "win" strobe by a 0.029 margin. Sweet! Oh yeah - on the third or fourth run, apparently the staff remembered my previous good runs last week, and announcer was talking up my car! 'Watch this silver Mercedes, folks, he's fast! He's only one MPH away from the 100MPH club... will he make it in tonight?" Too bad I didn't, d'oh. I couldn't hear him, but my friend watching from the fence heard it and told me later.

On a side note, I brought my 1987 300D turbo diesel and had the aforementioned friend race that for me. It ran very consistent 17.5's at around 80mph. In general I was happy with that for it being a stock setup, plus a hundred or so pounds of ICE and other bling slowing it down (along with 2/3 tank of fuel!). Now I have a baseline for when I start tweaking the diesel over the winter. :jaja:



The Bad: Bad news was, the car was noticeably slower on all 5 runs. Looking closely at the data, it seems equal or stronger (depending on the run) through about the 1/8 mile point, then it was weaker. I didn't even hit 99.0mph once. I'm not sure exactly what the cause was. I suspect several things. First, ambient temps were higher - that doesn't help. Second, with higher ambient temps and no cool breeze, the engine just would NOT cool down between rounds. Perhaps the slight power drop improved the lanuch - less wheelspin? Who knows. Third, the RENNtech chip claims a 15hp gain, which depsite the temp difference, should have kept me in the 99+ trap speed range. Needless to say I was really disappointed with that. Next time I think I'll run the stock chip. RENNtech has two different chips... one for early cars (through engine #8760), one for late cars (#8761+). I wonder if I have the "late" chip and it doesn't work well in an "early" LH module? Hmmm.


The Ugly: As if it wasn't depressing enough being stuck in the 14.2-14.3 range all night with sub-99 trap speeds (after running 14.08 last time with all four runs at 99+!), I ran into a weak battery problem! With the engine not cooling off well, I left the heater on 'max' for 30+ minutes after the first couple of runs. Even then, the engine temp was barely getting to the ~65C range, and by the time I'd get staged it would be back in the 70-80C area again. Well, it seems the stock alternator doesn't put enough of a charge out in the short time the engine is running, and by my third (or was it fourth?) run, the engine hesitated before cranking, then cranked a little slower than normal. UH-OH. So I quit running the heater while parked. Even so, on one of my last 2 runs, just as I was motioned to pre-stage, when I went to start the car it cranked *very* weakly. Eeeeeek. Luckily it started, and once running I could crank up the heater, but sheesh that was scary.

When I got home I measure the current draw. With just the key on (no heater pump, fan on low) the car pulls 18-20 amps! With the heater on max, it pulls over THIRTY amps! Egads, that's high. And it explains why the battery wasn't happy. Mental note - next time, have the diesel (which has a 150A alt installed) idle with booster cables attached to the 500, supplying juice to blast the heater all I want between rounds. Last week, it was cool enough that I didn't need to run the heater more than 15-20 minutes at most, and as the temps dropped I quit running the heater at all - no need to. One last "ugly"... my local track does NOT offer racing every week. Next week I can't race (unless I join a club in the next couple of days - it's a Club Only day.) Two weeks from now there are bracket racing finals where I can get 2 or 3 practice runs, and one race (which I'll probably lose and have to go home - see last week's report for details.) Oh, and that day starts at 9am, so I have to hope for cool *daytime* weather - not real likely. After that, I think there is ONE day in October I might be able to run (need to call and ask)- and that's it for the 2004 season. Grrrr, I was hoping to nail that 13.99 and 100.00 before 2005.



The Times:
14.245 @ 98.71
14.210 @ 98.98
14.363 @ 98.79
14.328 @ 98.32
14.266 @ 98.68



Full data is at this link:
http://www.meimann.com/docs/dragstrip/

Sorry for the grainy photos - not enough light. Note the two bags of ice on the airbox.

On a side note, check this out:
http://www.drag-city.com/track.htm

Altitude Correction Factor: 2,100 ft
To convert your Quarter Mile Elapsed Time (ET) and MPH to sea level times, multiply the applicable factor by your ET or MPH. ET = .9757 MPH= 1.0255


Theoretically, that would put my 'average' times at 13.95 @ 101.0mph (with 'spare tire delete', etc), and my best time at 13.73 @ 101.8mph...!? Yipes. And Firebird is up higher than that correction factor above, my GPS said 2700'. Hmmm! In street trim, with back seat, spare tire, etc my times would correct (using the same 2100' formula above) to roughly 14.10 @ 99.9... I wonder how accurate the correction formulas are though.

Thanks for the report. I would say those are VERY respectable times for that car. I would love to do some racing again, but the nearest strip is over an hour away and they really pack them in. Would like to try all three of the cars. With my G- Timer, the SL has done a 5.7, 0 to 60, and the 400 is in the mid 6's.

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

I just dug out an old timeslip from 3/19/00. 37 degrees out, rel. humidity 29%. Dense air supreme. Turned 13.846 @ 102.12MPH (vs an E55, of all things, that was not running correctly: 15.122 @98.01MPH). My later runs were a bit slower, I think 14.0ish, but still respectable.

I've never run under 14.0 since...but I've not ever been able to run in 37 degree weather!

__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

Damn, Michael - that's awesome. What elevation is the track you ran on? Also, what power-gaining mods do you have - airbox, chip, Y-pipe, etc? Was that in street trim with the spare tire on board, with stock wheels & tires? I'm just curious to compare...

Friday was the "Club Challenge" day, where the local clubs race for points. It was the final club race of the season, with the winner being decided in various groups. So I had to find a club that would let me race with them. Most are willing to do that, since if I win any races, I earn them valuable points. The guy with the newer E320 was in a club that had a member not show up so they let me join them. Anyway, that said, here's the lodown:



Pre-Strip Vehicle Prep:
My previous week's runs were all poor, IMO, and I had suspected the RENNtech chip. So I swapped to the stock 1992 chip. Then, while going over the car before the race, I noticed the intake air temp (IAT) sensor was disconnected. I just about fainted. It's possible that I did ALL my runs the previous weekend with the IAT off! I do not know for sure... it's also possible I pulled the wire while re-installing the marker light at the end of last week's runs. I just can't remember. (Yeah, this will trigger the CEL, but I didn't know how to clear that before, so the CEL had been on the whole time - d'oh. Now I know better.) I figured I better run the RT chip with the IAT connected, just to make sure that wasn't the problem. So, I then re-installed the RT chip. I also wanted to make sure that I wasn't losing power due to oxygenated fuel, or lower octane than the car wanted. So I ran 76-brand "Competition 100" blue race fuel, non-oxygenated, 100 octane. I put in 2.5 gallons, and probably had 0.5-1.0 gallons of 94 octane in the tank from last time. I also removed the rear seat back (34lbs), rear seat console & pockets (6lbs for all 3), and the stock sound pad (3.5lbs) for an additional 44-pound weight savings. All was going swimmingly until I started up the car and the ASR light came on. I started a separate thread about that problem - here's the link:
http://500ecstasy.com/forums/showthread.php?t=1075

On a side note: While leaving my house, with the engine temp at around 50C, I turned off the ASR and nailed the gas from a stop. The car easily lit up both tires and laid a good 50 foot twin black stripe. Wow, that was cool. 5 minutes later with the engine at 80C, I tried again, and this time got barely a chirp. So I'm pretty sure my power "problem" is still present, unless all 500's lose power at normal operating temps of 85-90C?? It ain't spark retardation, though, with race gas in the tank for this test!



Time Trials (Practice Runs):
My first two runs were also unimpressive. They were slightly better than last week, but it was also a little cooler out. For the first run there was no wind, either. I decided to swap EPROM chips at the track, and re-install the stock 1992 chip. The car INSTANTLY picked up almost TWO FULL TENTHS! (More details on that are here. ) The next three runs were 14.02-14.04. Damn- that's amazing. My third run of the day was also my last trial run, and was the day's best at 14.022 @ 99.45. I had to hope for the best with a 14.00 dial-in... if I dialed 13.99 or quicker, they'd make me wear a helmet, which I forgot to bring - ooops. It was windy again - that damned 10-15mph direct headwind was back. It did have the magical cooling effect on the engine though. I was able to keep engine temps down without running the heater off the battery while parked, other than 5 minutes or so between each run.



Bracket Racing!
A wicked looking storm was moving in and we thought things might get cancelled due to rain. Luckily it stayed dry, but it was very windy, and not all that cold... 70-75F ambients. I was expecting to lose my first race, like last time, and go home. I got lucky and my first race was won out of the box as the other guy red-lighted with a -0.005 RT (wow). He also broke out of his dial-in, so I would have won anyway, woo-hoo! Next race was a solid win, a good close race, the margin of victory (MOV) was 0.0697. Their RT was better but they were too far off their dial in. A LOT of people were breaking out of their dial-in times, even with the headwind. Might have been cooler/denser air or something - I dunno. Third race was against a Viper! He red-lighted, got mad, and putt-putted down the track - another win for me. BUT, on that run, the E500 did NOT feel right. Almost like a hesitation down the track, which I thought was wind gusts. But on the return road I felt it again. My time was crappy, I slowed down 2 tenths for no reason. In the pits, I revved to 2500rpm at idle and there was a big burp/misfire every 5 seconds or so, enough to see the tach needle drop 1/8 inch! Great - now what? I started freaking out about being too low on fuel and running out of gas or something. I had barely gotten settled down when my bracket was called again. (As eliminations proceed, you have less & less time between runs, as the number of people keeps getting cut in half.) It was less than 20 minutes since my last run, d'oh. I had no time to cool the engine and just ran the heater on max as much as I could, but by the time I staged it was up to ~75C already, oh well. On this race, my RT went to hell (after six incredible - for me anyway - RT's in a row!). And that cost me the race. Even if I had run my dial, my RT was too poor. Had my RT been even close to my next-worst (0.115), I would have won. And had I won that race, I would have scored a trophy as runner-up, and moved on to the semi-finals (or was it finals? I forget.) D'OH! But, as they say, "that's racin!". The car seemed OK on the last run but was still a tenth slower than the 3 good runs in a row. Very odd. I had NO tration problems all night, I don't think the tires spun at all at launch. I wonder if they treated the surface or something. I had sub-6-second 330' times for all the 'fast' runs. Oh, and I got a number of comments and raised eyebrows when people saw my dial-in time on the window... heh-heh.



The Times:
Less than three hundredths away from the 13's, but sadly I'm still no closer to the 100mph mark than I was before:

14.214 98.61 (RENNtech chip)
14.211 98.50 (RENNtech chip)
14.022 99.45 (Stock chip for last 5 runs)
14.041 99.20
14.026 99.45
14.215 98.64 (Engine hiccuped this run)
14.113 99.28


Next day will be Saturday the 25th, for more bracket racing... time trials start at about 10am so I have to hope for cool weather in the morning.

Excel spreadsheet with all data is here:
http://www.meimann.com/docs/dragstrip/E500_Dragstrip.xls

At the time I think the only mods on my car were K&Ns and a PAD chip.

Keep at it!

__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

I'm heading to the track in a few weeks. Any suggestions about the tire pressures? I run 35psi.....what should I lower it to?

I've been running about 20psi. Since the right tire seems to spin more easily, I have been using 21psi left, and 19psi right. I drive to the track with 30-35psi, then let air out when I get there. I drive home on 20psi because I'm only 10 miles away... if you are farther, bring an air tank, or compressor, so you can go back to 30psi for the drive home! If you try 35psi at the track, you may have issues with wheelspin. If you have ASR defeat, do a short burnout in front of the waterbox (I prefer to stay out of the water), then turn ASR back on, and engage the snow chain switch for your launch.

For more tips & tricks, click the link at the very top of the first post, and read Gerry's excellent write-up for the drag strip newbie! I learned a LOT from that and was less nervous my first time.

Great info, thanks!

Problem is, with ASR off you stand a good chance of having one tire light up big-time-FWIW.

I agree to the 20lb recommendation-assuredly no lower than 15.

__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

Exactly. Turn off ASR for your pre-stage burnout, then turn ASR back on. Then engage the snow-chain switch ONLY. This allows wheelspin up to a max of 25mph... and a *little* wheelspin won't hurt the launch any, actually in some cases in can help by getting the engine closer to the powerband sooner. And it will prevent one tire from "getting away" and smoking halfway down the bloody dragstrip, which can happen with ASR off (see my first post, last run of the night, top of this page.) RENNtech told Car & Driver to engage the snow chain switch for best results when they were testing their wild ($180k!) 600E back in 1992 for this exact reason. (I don't think that car had an ASR defeat switch, btw.)

Also - I wouldn't go below 15psi either. You really want the pressure as high as possible (to reduce rolling resistance), while still retaining enough traction to hook up at launch. Around 20psi on STREET tires seems to work well. You can start off with higher pressure and lower it as needed to help reduce wheelspin. No need for a long smoky burnout unless there's some really cute girls watching that you'd like to impress.