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First 1/4 Mile Results and Questions

11K views 54 replies 13 participants last post by  BohlDiesel 
#1 ·
Took the vehicle to a dragstrip this weekend for their last test-n-tune day of the season. Never been to a dragstrip before and didn't know what to expect. Must say it was a fascinating experience. As a complete newbie didn't do anything special to prep the vehicle: Fuel tank was 2/3 full, tires were normal air pressures, didn't remove any items (except the jumper cables) to reduce weight. Also, there was an 18mph NNW wind with gusts into the mid 20's and the track has the cars racing straight North . . . right into the wind. And man was the place packed with racers!

The best run was the first one before many people had made passes (and started dragging water into the main lanes). Was able to mostly bypass the water pit, but the pits were nearly as wide as the lanes. I had read about starting in 2nd and brake boosting to ~2k, but for my first 1/4 pass ever and I tried to start conservatively. Didn't really do any brake boosting and left the traction control on. I did start in 2nd gear. It was obvious the vehicle had too much torque for the track surface as the traction control kicked in quite a bit in 2nd gear even without brake boosting. The Michelin Pilot Super Sport's were not up to the task. Also, my reaction time sucked and the 60' was a horrible 2.24sec, but ended up with a 13.1 sec 1/4 mile at 107.2mph. That was fun.

Next pass still had the traction control on but tried to brake boost a little and had bigger traction issues. Much better reaction time on my 2nd pass, but an even worse 60' at 2.6 sec. Still ended up with a 107.1mph at the end into that headwind.

Tried once with traction control completely off and it was a fricken' clown show. Car nearly went sideways before I took my foot off the pedal. And water was becoming a problem as the big boys were heavily using the water pit (that's kinda cool to see) and dragging water everywhere. I didn't see any reason to continue trying without drag slicks.

Calculating the difference in wind drag at 107 mph vs 125 (107 + the ~18 mph headwind) shows an extra ~35hp sucked up by the headwind. Too bad it wasn't a strong tailwind :)

So, you guys with drag strip experience, what do you think proper tires that could hook up with brake boosting, and a calm day, would do for the 1/4 ml time? And any suggestions on a good drag wheel/tire setup?
 

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#45 ·
@TDI, you just gave me the advanced calculus version. I'm needing remedial algebra first. Did you just drill your OEM charge tube or did you buy another one somewhere? I'd like to be able to revert back without having to cork up the hole. I'm still in warranty and removing the meth kit sounds like too much for a dealer visit. It would seem obvious that doing the meth/water inject is way more effective at lowering the IAT as compared to the intercooler some folks have installed from Wagner. I emplore that I am not bad mouthing that product nor the efforts of some festers to get that product going in the pipelines. It would seem that using evaporative cooling which is active cooling "blows" away passive cooling which will at best get you down to T infinity of the convective cooling source (T ambient). I'll keep rereading your tech info and hopefully catch up sometime. I have a heat transfer back ground. What kind of engineer are you?
 
#46 ·
HA!

First off … I'm not someone who thinks if we modify a car under factory warranty and cause a problem that we should try to get the manufacturer to fix our self induced problem. However, I do understand that a lot of shops would not do due diligence in diagnostics if they see a mod and automatically blame the mod for the problem. So, that being stated, let's continue…

Did you just drill your OEM charge tube or did you buy another one somewhere?
Yes, drilled and tapped the oem charge pipe. Pre IAT sensor. This is so the DDE can adapt timing based on IAT (I've got some data from pulls that demonstrates the advance in injection timing if anyone is interested). I also have a backup charge pipe to install if needed. Although, I have some NPT stainless "plugs" that can be used to plug the hole if the H2O injector is removed. It's easier to just plug the hole than remove the charge pipe and install the non-molested one (which requires removing the underbelly covers and lifting the car to swap out the pipe).

It takes me about an hour to remove the mods I've got. But about 2 hrs to re-install. With all the wires/connections it's a lot of fussing around…

It would seem obvious that doing the meth/water inject is way more effective at lowering the IAT as compared to the intercooler some folks have installed from Wagner. I emplore that I am not bad mouthing that product nor the efforts of some festers to get that product going in the pipelines. It would seem that using evaporative cooling which is active cooling "blows" away passive cooling which will at best get you down to T infinity of the convective cooling source (T ambient)...I have a heat transfer back ground.
Excellent. The thermodynamic data should be of specific interest to you! It's interesting how much more effective the OEM intercooler is when on the open road vs. standing still on a dyno. The dyno shop had a huge fan the operator placed in front of the car to "help" cool the intercooler. The fan was huge and moved a lot of air, … just not over the intercooler. On the open road where you are "pushing air" the OEM intercooler works significantly better. Compare the IAT's on the open road at 90F (http://www.bimmerfest.com/forums/showpost.php?p=6940121&postcount=62) vs. on the dyno at ~65F (http://www.bimmerfest.com/forums/showpost.php?p=7614924&postcount=1). At 90F on the open road starting IAT's were ~5 F above ambient whereas on the dyno the IAT's were ~30F above ambient. However, the thermal dynamics of the H2O/methanol evaporation had radical impacts on the charged temps in both cases. Well above what a passive intercooler can accomplish.

What kind of engineer are you?
Undergrad and post grad work specialized in Quantum Physics and Analog/RF/mmW Integrated Circuits. Profession is more in the EE realm.
 
#47 ·
Question for the engineers; from someone with no knowledge of automotive alcohol water injection.

I used to be a cargo pilot and some of the old piston planes I flew had ADI (Anti-Detonation Injection) and some of the turbines had AWI (Alcohol Water Injection). Both used an alcohol water mix with a small amount of water soluble oil. We were taught that pure water was better at charge air cooling than the water/alcohol mix; but the alcohol had to be added to keep the mix from freezing at altitude.

Question: In an automobile, at least in the warmer months, why not use 100% distilled water? What is the alcohol accomplishing? Or was I taught wrong?


Thanks,

JW
 
#48 ·
Think you were largely taught correctly.

The addition of methanol can add power. But the higher the methanol/water % you add the less potential EGT reduction you can achieve. Too much EGT's and things melt...

Regarding diesels and water/methanol injection, there's tons of good info out there already. A couple links below should give you some good info to start with.

http://www.snowperformance.net/faqs_type.php?type=diesel

http://www.dieselpowermag.com/tech/1005dp_water_methanol_injection_how_much_is_too_much/viewall.html
 
#49 ·
Ah, makes sense.
The engines I'm speaking of were supercharged and non-intercooled. The blower ratios were designed more for altitude than takeoff. You couldn't use full throttle at sea level; so the easiest way to add power on that engine would be to cool the charge air so that you could use more throttle without getting detonation: hence ADI.
 
#51 ·
Sorry for the late reply, but I've not been hanging around this forum as much ...

So the car developed more power since my last posts on this thread, and was needing to shift into 5th before crossing the line. So went a size smaller to 225/45/R17's for the DOT drag radials.

Last Spring I made 2 pulls, and both pulls were 11.8's. More info here: http://www.bimmerfest.com/forums/showthread.php?t=772491
 
#52 ·
Thanks ! :)
Right on time as I picking up my car this after-noon having just had a water/meth kit installed (and a before and after dyno test)
Will be getting some drag radials next....will be definitely using your tire experience / info . And what about your front tires/wheels?
(FYI....had the exact same experience with the 4th gear peaking (?) right before the line and thinking I might need to shift earlier to 5th.)
What altitude were/are you running at? Me....5200 ft / Albuquerque, N.M
randy t.
Have a great day/week-end, unless ya have other plans :)
 
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