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  #1  
Old 08-11-2012, 02:34 PM
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Default Tips for Slow Acceleration

SO i finished my build last summmer, then went to college and didn't really get a chance to use it until this summer. It is a Vw 86 GTI, 120v using optima yellow tops and an 8" motor, clutchless. It works fine, but my biggest issue is acceleration. I pretty much drive flooring the pedal the whole time. I think my potbox is a PB-5, i can double check.

Is it normal to drive usually flooring it? can i change the pot for better preformance, or am i stuck?

Also any fixes for slow accel, its hard to time crossing an intersection when it takes so long to get going.

oh and also , i usually drive in second gear. I suppose changeing gears when i stop and go would help a bit

Thanks
Jake
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Old 08-11-2012, 02:56 PM
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Default Re: Tips for Slow Acceleration

Quote:
Originally Posted by omonoid View Post
SO i finished my build last summmer, then went to college and didn't really get a chance to use it until this summer. It is a Vw 86 GTI, 120v using optima yellow tops and an 8" motor, clutchless. It works fine, but my biggest issue is acceleration. I pretty much drive flooring the pedal the whole time. I think my potbox is a PB-5, i can double check.

Is it normal to drive usually flooring it? can i change the pot for better preformance, or am i stuck?

Also any fixes for slow accel, its hard to time crossing an intersection when it takes so long to get going.

oh and also , i usually drive in second gear. I suppose changeing gears when i stop and go would help a bit

Thanks
Jake
Well as long as your three main components are checked and are okay (Motor, controller, batteries)

Check if your potbox at WOT is giving you 100% of your 500A from your controller. Maybe something got messed up and WOT is only 50%, then you are talking about only half of your torque, 42ftlbs of torque.

I would also start out in first gear and see what happens since you may need more torque multiplication, 500A in a 8"ADC (im assuming you have a 203-06) is only 85ftlbs and 58hp.
http://www.evparts.com/cms/picts/pro...otoroutput.PDF
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Old 08-11-2012, 03:06 PM
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Default Re: Tips for Slow Acceleration

What does WOT stand for? Full accel i assume? What would be the best way to check that there is 500A? Just a ammeter on both terminals of the pot?

I havnt done much to actually check the controllor, batteries and motor, i just assumed they were working fine since the car runs. What's the standard method of confirming these are all ok?



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Old 08-11-2012, 04:19 PM
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Default Re: Tips for Slow Acceleration

I drove floored all the time my first year. In 2nd I top out at 45 anyway so with a typical speed limit of 40 I'd just keep it floored, traffic allowing.

You should be able to tell if you're using your full potential by the amount of current you're pulling. Does your ammeter peak near the full capacity of your controller? What controller do you have?
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Old 08-11-2012, 05:55 PM
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Default Re: Tips for Slow Acceleration

WOT = wide open throttle, yes, full acceleration, pedal to the floor.

I would invest in a ammeter like Ziggy says, so you can monitor the peak Amps you are getting from your controller and into your motor.

Full acceleration with 85ftlbs in 1st gear should not be slow...

I used to have a 1997 civic (~2600lbs) with ~89ftlbs from the ICE and it wasn't so slow I was worried about getting through an intersection quick enough. And it didnt even have the full torque from 0rpm!

Per his Evalbum he has the P&S DIY 144V 500A controller...
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Old 08-11-2012, 06:27 PM
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Default Re: Tips for Slow Acceleration

Yeah i have the P&S DIY 144V 500A controller, which i assembled myself, but i think it is working the way it should. So your saying at WOT my in dash ammeter should read 500A? it rarely passes 250 when flooring it up a hill, ive never seen it as high as 500. Plus my breaker is rated for 300A i think, so that would flip at 500A anyway. Maybe my controller is having issues?

Any advice?
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Old 08-11-2012, 08:03 PM
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Lightbulb Re: Tips for Slow Acceleration

Most 300A circuit breakers will hold 500A for a few seconds, so that should not be a problem. You might want to check all your connections and wiring to see if you are dropping too much voltage there, and monitor the battery voltage for sag. You can check the voltage (or resistance) on the accelerator pot box to see if it it is pushing the controller to maximum.
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Old 08-11-2012, 08:30 PM
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Default Re: Tips for Slow Acceleration

With a 500A controller you should be hitting at least 450A unless the pot isn't giving a full signal or the controller is throttled back. Disconnect the pot leads from the controller and check what values you get when *someone else* presses pedal to full and at 0.

Just how sluggish are you? If you're at a stop, how fast are you by the time you get across the intersection? My bug's never been sluggy on the low end (unless I'm in 3rd or 4th gear) even if I limit it to 200A.
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Old 08-12-2012, 02:02 AM
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Default Re: Tips for Slow Acceleration

You might need to adjust your controller parameters for snappier acceleration and proper throttle range. Have you connected your controller to a computer? Download a program called RTD explorer.

ps. I have VW 89 Golf/rabbit with P&S controller too. Works just fine.
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Old 08-12-2012, 02:36 PM
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Smile Re: Tips for Slow Acceleration

PStechPaul:
Quote:
You might want to check all your connections and wiring to see if you are dropping too much voltage there, and monitor the battery voltage for sag
How would I test for voltage sag? All I’ve done so far is confirm that the voltage across the pack is the same voltage across the controller when the car is on.

Quote:
You can check the voltage (or resistance) on the accelerator pot box to see if it is pushing the controller to maximum
.

I tested the resistance of the potbox with my ohm meter and at 0 acceleration, it read 0 ohms and a full, it was 1. That seemed odd to me. Shouldn't it be the opposite? 0 resistance at full throttle.

Ziggythewiz:
Quote:
Disconnect the pot leads from the controller and check what values you get when *someone else* presses pedal to full and at 0.
How would I go about doing this? If I disconnected the motor the controller would have no load right? But if I left the motor connected, and did that, the car would move, making it very hard to measure anything
And by values I assume you mean amperage to see how close to 500A it gets.

I have my ammeter/shunt wired on the negative side between the pack and the controller (and a fuse). Would that work for measuring the amps the controller outputs, or would I need to measure the amps between the controller and motor?

Quote:
Just how sluggish are you?
If I’m stopped on a slight uphill before an intersection it probably takes me 10 sec or so to finally get across and up to speed. That's a rough estimate, but I’m defiantly starting to think something is wrong based on everyone's responses.

mora:
Quote:
You might need to adjust your controller parameter
I was aware I could do that, but haven't. Do you think it is necessary? I remember back when I was building the controller I didn’t have the adapter to hook the controller to my pc. Did you get some usb adapter or something?

Also it is kind of a hassle to take my controller out and disassemble it enough to hook to my pc since I glued plexy glass to the sides. I can still take it out, but only if you really think it is necessary.
I’ll probably try all the other suggestions first.

Thanks to all for helping me resolve this
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Last edited by omonoid; 08-12-2012 at 02:40 PM.
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