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RPM slow response to app

Posted: Mon Dec 03, 2018 7:58 pm
by PS14
Watching some in car footage i noticed the RPM guage seems to show the same readings alot. like "5445". its not smooth or updateing fast enuff? any thoughts on what would cause this.

Here's a link to a 30 sec video where you can see what i mean.

MK2/Rpi on latest app and firmware.
USB cable from MK2 to Rpi dash
Rpm channel set to medium and 25htz (same as all other channels) pulled in from a CoilX attached to kettering type ignition (GM Hei)

Thanks, Dave

Posted: Tue Feb 05, 2019 11:03 pm
by brentp
Hi, is this your car's video, or something you found online?

Best would be to do a controlled test to carefully observe the RPM response. There's too little information in the video you shared for us to comment. Overall, RaceCapture calculates RPM on every ignition pulse, which will make it very high resolution.

Posted: Tue Feb 05, 2019 11:25 pm
by PS14
its my gopro footage. at first i thought maybe it was a video issue. it just seems odd that i see the same rpm readings repeating. it will do the same thing sitting in the shop and reving the engine, as tho the display cant update fast enuff.

Posted: Tue Feb 05, 2019 11:26 pm
by brentp
Yes, a test in your shop in a controlled environment would be helpful.

Try varying RPM at different speeds and see if the RPM updates smoothly on the display.

Posted: Tue Mar 05, 2019 10:38 am
by mdknutsen
Any update on this? Ive been having s similar issue.

Posted: Fri Mar 08, 2019 12:00 am
by brentp
Hi mdknutsen,

How are you reading your RPM? Direct wire, CAN bus mapping or OBDII? If OBDII, what year is the ECU?

Re: RPM slow response to app

Posted: Tue Apr 02, 2024 8:19 pm
by RinerAuto
Instead of starting a duplicate new topic, figured reply to this one.

I'm seeing RPM signal is delayed on tablet which is connnected via bluetooth to RaceCapture/Pro Mk4. RPM is coming over legacy OBDII (2003 Ford ecu).

Is RPM expected to be delayed over OBDII? Is tablet connection over bluetooth or wifi preferred?

Re: RPM slow response to app

Posted: Sat May 04, 2024 1:23 am
by brentp

What you're experiencing is possibly a combination of things:

1. The ECU's protocol for older (pre 2008 ) is quite slow compared to the CAN protocol of newer cars. This will limit how fast individual channels will update.
2. The OBDII protocol is request-reply protocol where each requested channel takes turns being requested. We have a very smart querying engine where channels configured for faster update rates are queried at a higher interval, to help optimize the design. See our OBDII guide here for the rest of the story and on how to set up your system: ... erformance

Overall, our OBDII system - especially with our legacy adapter, is designed to display data as fast as your ECU will allow. See the notes here on the Legacy adapter: ... f_your_ECU

One other way to get faster RPM performance is to directly sense the RPM signal using RaceCapture/Pro. ... PM_Sensors

We hope this helps!