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Author Topic: Power Braking - Brakes Won't Hold Car  (Read 7074 times)
AudiMan85
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« on: September 30, 2014, 07:54:56 PM »

Ok, so I'm using a cooked up tune based off NVR's file. Now after reading about left foot braking I made the changes. Problem is not matter how hard I hold the brake pedal as it builds some power (idk when) it starts to lurch forward.

Does it help yes in taking off, off the line yes. The car will not die before taking off. But since I wanna take the car to the track and see what it runs and just to have fun before I do my stage 3 setup over the end of winter. My question is there some way, some how in the file I could set it to hold the car back more still allow me to mash the throttle. If I jump the light I'm gonna get a RED light (don't know term) or I'm gonna a crappy time cause it's gonna lurk and start the timer. I've been trying and trying to find the perfect rpm to shoot for but it's hard I might have to video tape the instrument cluster.

The other question was kick down for the automatic transmission on the dyno, I have a hard time getting to 2500rpms and WOT for logging and its hit or miss on kick down. Any ideas and or suggestions for either question?

Settings in my file I could change? Daz has already modded my TCU I don't know what he did exactly but maybe he could do something else to it.

Thanks,
Kendel
« Last Edit: October 01, 2014, 07:52:31 PM by AudiMan85 » Logged

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ddillenger
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« Reply #1 on: September 30, 2014, 08:17:26 PM »

If you're on the brakes HARD, not moving, what RPM can you hit? How high do the RPM's rise?
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AudiMan85
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« Reply #2 on: September 30, 2014, 08:44:47 PM »

I'll log it tomorrow afternoon when I take wife to work. It's not high, only see maybe 1psi of boost before car moves. I have a little more success with holding e-brake with button pushed in to quick release. Today it was raining and I was slow to release e-brake and the front spun some.

Daz, I found videos from a few months back in Walmart parking lot. These will give you some idea. I know logs will be better. But these are of the gauge cluster and boost gauge. The car does move at which point I'm let off the brakes. It seems to be 2200-2500 and I can't say that boost gauge was accurate cause I know it wasn't and has been replaced. Compiling the video now, will post up when it finishes uploading.

Post log tomorrow.
« Last Edit: September 30, 2014, 09:00:13 PM by AudiMan85 » Logged

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AudiMan85
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« Reply #3 on: September 30, 2014, 09:52:57 PM »

Here was the video I talked about. The car makes more HP since this footage and does break loose on wet ground.

http://youtu.be/nvIHFQHSUFc
« Last Edit: September 30, 2014, 09:55:50 PM by AudiMan85 » Logged

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AudiMan85
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« Reply #4 on: October 01, 2014, 07:51:51 PM »

Here are some video's I took today with Torque App. The data isn't great. But attached is datalog from this evening. I see I was able to build about 10psi on my boost gauge before the car started to move forward but started to surge alittle. The torque app's refresh rate is.... well you already know.

Video from this a.m.
http://youtu.be/EWBzFOcZ2s4

The log below has 2 power braking attempts. The second one me and my wife admit was decently strong. This took all my force on the brake pedal and slowly build up power and then floor it, the car started to shudder a bit so I decided to let off and go right as it lurked.
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seishuku
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« Reply #5 on: October 02, 2014, 04:08:54 PM »

Does it really surprise you that an AWD car with a good amount of power can overrun the brakes?
Doesn't surprise me. lol

If you have a high bias center diff, then you might be able to do this.
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AudiMan85
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« Reply #6 on: October 02, 2014, 05:45:19 PM »

I know the brakes won't hold. I may not be a pro at anything but been around a lot of different cars. In high school I lived spoiled rich kids and a lot of my friends had nice cars. Many different types, lots of money. Money to spend on parts and what not. What I'm getting at is not everyone had automatics.

Few did, one friend has a 400whp 1997 GSX Eclipse Auto with a IPT built trans, I ordered it for him with what his goals where (600whp). IPT suggested a few changes to our request and switched us to a 3200rpm high stall torque converter and they reworked the valve body, did the upgraded springs (shift kit) etc. This car held fine all the way to 3200rpms and built 10psi and made a decent launch.

Now, from what I see from logs and dyno pulls the 2.7T makes some crazy low torque at low rpms, the main reason the car feels so strong. Now as part of my brainstorming is that since we have access to the tcu editing and ecu controls if there was a way to set a stationary rev limiter on the auto/tip cars by ways of somehow IDK but from my logs with my mods and tune about 2200-2500 is about when the brakes will give, this at that track could be tricky to get good times unless you aren't looking to take off so fast or faster.

So that really is my question in a sense. Does the ecu know if the brake pedal is applied? I'd guess so since it has CC and also maybe a mph switch could be involved in some control this is more for the people that understand it better then I do. This thread was more than just a my cars brakes won't hold out and was ment to give light to new ideas.

Also, the question of disabling kick-down in 3rd so logging would be easier on the street and dyno was another point I brought up.
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seishuku
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« Reply #7 on: October 04, 2014, 09:31:33 AM »

What kind of center diff did the eclipse have though?
If it had an open center diff, or even a viscous center, that's probably why... The engine/braking power is enough to force the power to the rear wheels and you can break free.
But Audi's helical diff will keep 50/50 power split to both axles as long as they both have traction, so it'll just power through the brakes.

That's how I see it anyway...
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AudiMan85
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« Reply #8 on: October 04, 2014, 10:03:17 AM »

I don't know much about the automatic gsx/awd transmission as I have never taken one apart. I did however tear down my 5 speed and I did have a big drum VC attached to the center diff shaft so I'm sure the automatic did also. It was mounted after the end plate along with 5th gear then the transmission final cover went on. I know from the HP I made with that car that it was 60/40 I believe, I often on launches spun the front passenger tire and in rain/wet ground the rear would kick like a RWD with the front wheels kind of pulling the car forward and controlling it.

Now the Audi for sure is tricky to control when breaking loose in the rear or coming of car wash and it's harder to control as I am not use to how the AWD system works in the Audi. Have to get more practice but the 4 lane highway leaving car wash is hardly ever empty and that's the only time I try to kick it out. The walmart parking lot tests where to just see if I could spin the fronts for fun. Someone bet me I couldn't in a automatic.

Thanks for the lesson/info tho about the AWD on these cars.
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"Ride like I got a horse stable under my hood" ~ The Game - Too Much
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