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      05-25-2012, 07:48 AM   #1
pits200
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Why do some cars seem to run so much stronger?

Went to the track yesterday, I'm fbo + meth(running 50/50) 50% e85 and xi and an auto.

I understand that my et will suffer because of awd and weight but I got 4 runs in yesterday and every single one of my 60s were 1.62-1.70 and my 1/8 times were all 7.8-8.0 but my best run was a 12.4 at 112 so its obvious my final 1/8 is not strong.

I see a lot of other xi guys do those times with less mods.

So my question is, what exactly is it that makes similar cars with similar mods so much faster or slower whether comparing xi to xi or i to i. I'm looking for technical answers, I am assuming equal drivers(not that it matters much for me since I'm automatic). I understand there can be a lot of variables such as plugs, carbon, etc. but any input is appreciated.

Also, there was a 20mph headwind, how much would that effect times(estimate).

Thanks
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      05-25-2012, 07:52 AM   #2
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how many miles on your car? maybe get walnut blasted ?
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      05-25-2012, 07:59 AM   #3
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Quote:
Originally Posted by 335(EX)(EYE) View Post
how many miles on your car? maybe get walnut blasted ?
49k..

I tore off the manifold about a month ago and my valves were pretty clean, I was actually shocked.

Maybe I just suck at driving an automatic, if that's so, it kind of depresses me.

I dont' have the logs on this computer but when I look at my runs, my throttle doesn't stay at 99%, I have a lot of dips where it'll drop down to 60% like 10 or 12 times during the run even though I'm mashing the pedal.
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      05-25-2012, 08:32 AM   #4
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Quote:
Originally Posted by pits200 View Post
So my question is, what exactly is it that makes similar cars with similar mods so much faster or slower whether comparing xi to xi or i to i. I'm looking for technical answers, I am assuming equal drivers(not that it matters much for me since I'm automatic). I understand there can be a lot of variables such as plugs, carbon, etc. but any input is appreciated.
Could be any combination of the things (or maybe just one specific thing):

Maintenance
  • Spark Plugs - Replace, try NGKs
  • Ignition Coils - Replace
  • Oil Change - Change fluids/filter
  • Fuel Injectors - Replace/upgrade
  • Intake Filters - Dirty/Low Quality filter
  • HPFP - Starting to die (you'd know if its dead = limp mode)
  • Transmission - With an AT, possible your gears aren't catching as well from launching the car
  • Carbon Build Up - Dirty intake valves
  • Boost Leak - If you're not data logging, you might not be aware that you have a boost leak. Could be your OEM DVs aren't holding boost, or you have a leak somewhere between your CP, DVs + FMIC

Performance
  • Different Tune/Boost settings - COBB Stg. 1 doesn't equal Vishnu Stg. 1 or BMS Stg. 1
  • Gas - Pump gas vs. Race is obvious, but even quality of 93 octane changes from gas station to station. I only use Top Tier Fuel (approved by BMW)
  • Meth Ratio - More aggressive mixture, 60:40 or 70:30
  • Upgraded Trans/Clutch
  • Car on a Diet - Lots of CF, Backseats were Removed, Lightweight Alloys, Higher Quality Tires
  • Driver Error - Even in an AT, you can be shifting at the wrong time (too early or too late). I know with my COBB tune, my power band starts to die around 6,000 RPMs. You'll need to data log to see find out your optimal shift point, see at what RPM does power start to fall off.
  • DTC - Make sure it's off
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      05-25-2012, 08:44 AM   #5
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Two of the biggest factors at the track is DA, temps, headwind, tire pressures and weight....

But fwiw, comparing times at different tracks is tough.. Best way to see where ur car stands is by taken away the DA/temp/track prep is to see what other cars are running on the same day as you..

If your looking for some serious times, you have to prep well.. Log car to see if its on target.. Research for close to or negative DA, good cool temps, find a "fast track" which is know for being fast.. Take all unnecessary weight out the car.. Helps..
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      05-25-2012, 08:48 AM   #6
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Are we talking about cars on the same track or comparing cars from different tracks? Not all the tracks are the same (elevation, gradient, etc.)

Don't forget a car with a full gas tank will always be slower than a car with a nearly empty gas tank.

Cars with lighter/smaller wheels and tires will be quicker than those with heavy/larger ones (think unsprung weight)

Weather: A cool, dry crisp night run will be faster than a mid-day, warm/humid run.

Don't drag with your A/C on
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      05-25-2012, 08:59 AM   #7
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Quote:
Originally Posted by pits200 View Post
Went to the track yesterday, I'm fbo + meth(running 50/50) 50% e85 and xi and an auto.

I understand that my et will suffer because of awd and weight but I got 4 runs in yesterday and every single one of my 60s were 1.62-1.70 and my 1/8 times were all 7.8-8.0 but my best run was a 12.4 at 112 so its obvious my final 1/8 is not strong.

I see a lot of other xi guys do those times with less mods.

So my question is, what exactly is it that makes similar cars with similar mods so much faster or slower whether comparing xi to xi or i to i. I'm looking for technical answers, I am assuming equal drivers(not that it matters much for me since I'm automatic). I understand there can be a lot of variables such as plugs, carbon, etc. but any input is appreciated.

Also, there was a 20mph headwind, how much would that effect times(estimate).

Thanks
What boost are you running? Those are great 60' times, if you're running anything over 16psi I would have expected 7.7 in the 1/8th and the headwind won't affect that first half very much.

Humidity + Temp can change things somewhat, but you can usually get in one good run before temps start to really bring the traps down.
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      05-25-2012, 09:28 AM   #8
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Quote:
Originally Posted by pits200 View Post
Went to the track yesterday, I'm fbo + meth(running 50/50) 50% e85 and xi and an auto.

I understand that my et will suffer because of awd and weight but I got 4 runs in yesterday and every single one of my 60s were 1.62-1.70 and my 1/8 times were all 7.8-8.0 but my best run was a 12.4 at 112 so its obvious my final 1/8 is not strong.

I see a lot of other xi guys do those times with less mods.

So my question is, what exactly is it that makes similar cars with similar mods so much faster or slower whether comparing xi to xi or i to i. I'm looking for technical answers, I am assuming equal drivers(not that it matters much for me since I'm automatic). I understand there can be a lot of variables such as plugs, carbon, etc. but any input is appreciated.

Also, there was a 20mph headwind, how much would that effect times(estimate).

Thanks
at what rpm are you launching ?.... your 60f is good
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      05-25-2012, 09:32 AM   #9
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+1 on this

Quote:
Originally Posted by 5soko335i View Post
Two of the biggest factors at the track is DA, temps, headwind, tire pressures and weight....

But fwiw, comparing times at different tracks is tough.. Best way to see where ur car stands is by taken away the DA/temp/track prep is to see what other cars are running on the same day as you..

If your looking for some serious times, you have to prep well.. Log car to see if its on target.. Research for close to or negative DA, good cool temps, find a "fast track" which is know for being fast.. Take all unnecessary weight out the car.. Helps..
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      05-25-2012, 09:35 AM   #10
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Tell us about your technique:

Are you launching in 1st or 2nd?

How high are you brake boosting?

Are you manually shifting or letting DS do the shifting?
(If manually shifting, what RPM are you shifting?)

Do you have the kick-down mod, or are you avoiding the kick-down?

Even with an Auto, you cannot simply mash the gas and expect to break records, there are things that you will have to do right.
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      05-25-2012, 09:39 AM   #11
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Quote:
Originally Posted by Velocity26 View Post
Tell us about your technique:

Are you launching in 1st or 2nd?

How high are you brake boosting?

Are you manually shifting or letting DS do the shifting?
(If manually shifting, what RPM are you shifting?)

Do you have the kick-down mod, or are you avoiding the kick-down?

Even with an Auto, you cannot simply mash the gas and expect to break records, there are things that you will have to do right.
Based on his 60', everything he is doing on launch is about as good as it can be.

Shifting at 6200 rpm vs redline yields better times, but at the most we're talking .2 to .3 less on the ET and the trap speed isn't really affected by this.

Really need to know the boost he's running and the DA at the track when he ran IMO.
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      05-25-2012, 09:56 AM   #12
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If he can get .3 off by shifting early, and improve his launch technique to get a 1.5 60', he is already into the 11's.

I just believe that we have to know what he is doing, if we are to identify what he is doing wrong (if he is doing anything wrong).

Maybe he is having issues with his tune, have you posted any logs?
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      05-25-2012, 10:08 AM   #13
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The fact that his throttle is not 100% throughout the run is what puzzles me. Definitely makes no sense running 12.4 esp. an N54 with those mods.

I'm assuming the OP was launching in 1st because of XI.
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      05-25-2012, 10:45 AM   #14
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Are you making sure to turn the Traction control and stability control are both completely off? This is done by holding the button down for 5 seconds, until you get the dash warning.



Quote:
Originally Posted by sA x sKy View Post
The fact that his throttle is not 100% throughout the run is what puzzles me. Definitely makes no sense running 12.4 esp. an N54 with those mods.

I'm assuming the OP was launching in 1st because of XI.
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      05-25-2012, 10:57 AM   #15
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Need logs. Constant throttle closures can't be helping.
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      05-25-2012, 11:40 AM   #16
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      05-25-2012, 12:25 PM   #17
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Thanks for all the answers guys. My logs are on my netbook at home, when I get home after work, I'll post up some logs, its a little baffling to me about the throttle. First few runs, I was running 17.5 psi max boost with 10% timing correction since I'm running both e85 and meth.

But my meth flow hasn't been constant and I didn't want to risk things and I think my settings were somewhat conservative unless meth stopped flowing.

As for launching, I'm an XI and this track does a fantastic job of prep, I get no wheelspin on a 2.5k launch. I just used the DA calculator on dragtimes and here is what I got.

Density Altitude: 2985 feet
Relative Density: 91.55 %

Not sure if that helps and ya, I had about 3/4 a tank of gas and thats about what,,, 12 gallons of gas X 8lbs per gallon, so about 100lbs extra from the gas.
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      05-25-2012, 12:26 PM   #18
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If you are trapping 112mph, you aren't making the power.

I'd look at your logs and Dyno time is even better. Your 60' times are incredible!
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      05-25-2012, 12:30 PM   #19
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Quote:
Originally Posted by The Ghost View Post
If you are trapping 112mph, you aren't making the power.

I'd look at your logs and Dyno time is even better. Your 60' times are incredible!
Ya, unfortunately, awd dynos are a little hard to find in Pittsburgh, there is actually only 1.

And ya, 112 is low even for an xi. I was hoping to trap at least 115mph despite my weight and drivetrain loss.

Thanks for the 60times comment, I have to admit it feels awesome on launch, yet that feeling quickly subsides when I see how below par my second 1/8th is.
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      05-25-2012, 01:33 PM   #20
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      05-25-2012, 04:59 PM   #21
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He has a great 60 foot. Tires are not the issue
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      05-25-2012, 05:20 PM   #22
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Quote:
Originally Posted by pits200
Quote:
Originally Posted by The Ghost View Post
If you are trapping 112mph, you aren't making the power.

I'd look at your logs and Dyno time is even better. Your 60' times are incredible!
Ya, unfortunately, awd dynos are a little hard to find in Pittsburgh, there is actually only 1.

And ya, 112 is low even for an xi. I was hoping to trap at least 115mph despite my weight and drivetrain loss.

Thanks for the 60times comment, I have to admit it feels awesome on launch, yet that feeling quickly subsides when I see how below par my second 1/8th is.
lemme next time you head to the strip...I'd love to go.
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