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Old 05-25-2010, 09:43 PM   #1
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Default MAP sensor rise time (response time), and noise on MAP signal

Could you guys datalog this test:

While idling, jab the throttle very quickly and briefly around 3x, about a second apart.

Then from the datalogs, examine the rise time - the time it takes between - when the log shows the throttle hitting about 15-25%, to the time that the MAP sensor reads about 85-90 kPa.

I have an AEM, and in my case with just one restrictor, it's about 80-100 mS. My problem is that my MAP signal is noisy. If I make the restrictor smaller, the rise time goes to > 150 ms, and it causes a tip-in hesitation.

I'm interested especially with data with the MAP sensor connected to the FPR. I have a 2000 so I don't have an FPR.
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Old 06-01-2010, 09:03 AM   #2
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Well that's interesting.

Do you think a large fuel filter damping the noise on the MAP would also cause a delay in the rise time?

I'm wondering if the fuel filter approach would dampen things without slowing the response as much as a restrictor.
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Old 06-01-2010, 01:19 PM   #3
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Yes and possibly yes. Thus my post.
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Old 06-01-2010, 03:03 PM   #4
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I don't have the specific data you're looking for, but here and here is some data I collected on the MAP noise issue. I think it can probably be solved by sampling the MAP sensor in a different way (either at a different crank angle or by oversampling and filtering) but I haven't had a chance to experiment.
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Old 06-02-2010, 04:26 PM   #5
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Thanks. I don't expect there to be a difference between the snubbers you linked (porous disc), and a simple restrictor (I used a 5 mm long piece of 3/16" brass rod stock with a .035 hole drilled through).

Has anyone experimented with different pickup points on the VICS manifold?
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Old 06-02-2010, 04:35 PM   #6
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Jason, what map sensor are you using on your AEM?

I have a GM 3 bar and i am experiencing some strange issues that im sure i could get tuned out with something like this.

(main problem is free revving holding say 10% throttle (delta tps=0) the RPM will swing as much as 1000rpm)
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Old 06-03-2010, 04:01 PM   #7
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MAP sensor. I was using a GM 2 bar, but now I switched to a Motorola 2.5 bar.
I'm uncertain if I had the same problem with the 2 bar, but I expect I did, but it's just that I am tuning my fuel map now much more finely and thus only noticed the problem now, in prep for running moar boost.
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Old 06-18-2010, 03:08 AM   #8
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Old 07-06-2010, 07:23 PM   #9
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Interesting. When I have time I am going to try implementing a discrete time equivalent in the MS2. An exponential smoothing algorithm would be easy to implement and present low CPU overhead.
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Old 07-06-2010, 10:48 PM   #10
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kday if you do it digitally you may want to combine a 2 pole bessel (my filter) with a little bit of hysteresis and median filtering.
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