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I have tried haltech iC-7 and AIM MXS strada and I noticed that there is lag in RPM reading on both on them . The Dashes are connected to the ecu by CAN. Also a one of my friend have Motec LCD dash and he says the same.
The question is how to reduce this display lag ? And which LCD dash on the market has minimum display lag based on your experience ?
Describe exactly how the RPM is being received over CAN? Is it from a direct broadcast? At what rate?
If it's using OBD2 queries and the ECU only responds at 2Hz that would not be surprising and very laggy. OBD2 is often only intended for diagnostic equipment, and not "gauge quality" display -- particularly in older vehicles.
To find the fast "broadcast" CAN messages with Engine Speed you might want to look at the following HPA resources:
or this course on CANbus Communications Decoding:
As David said, what is the broadcast method into the Displays being used? What ECU is being used to transmit the signal?
It may be that the ECU is only transmitting the Engine Speed at a low update rate, leading to the apparent "lag" in the response of the display.
I cannot speak for the Haltech and AIM displays, but looking at overlaid Engine Speed data from a MoTeC Mx00 or M1 ECU compared to the logged over CAN Engine Speed data from a MoTeC Dash in i2, the graphs line up timewise, and this is also the data that is used to drive the engine speed displayed on the screen. The Engine Speed channel is transmitted out of the M1 at 100hz over the CAN Bus, this is fast enough that there should be no user perceptible lag in the displayed data.
I don’t see any noticeable lag even at 20hz broadcast which is normally all I use if is only for display.
You can only notice the lag when free revving the engine (transmission in neutral), the first case it was haltech 2500 iC-7 dash the communication is via haltech CAN system. The second case was Hondata Kpro V4 with AIM MXS dash communication via Hondata CAN protocol (500kbps)
It is also good to note that when I tried racepak dash IQ-3 with haltech ecu there was no lag, so I think that the problem is the LCD dash not the communication.
What is the point of your post?
First off, your comparing 'lag' to what exactly? What is your reference or control? You are giving random examples of different combinations.
You have had valid and helpful answers from 2 members employed by ecu and dash manufacturers and someone who makes a living as a data engineer and providing support and setting up aftermarket products for people.
You have physical limitations, which is the refresh rate and input latency of the LCD panel itself. Between options on the market, these will be similar between options available as there are only so many suitable options on the market. You have no control over this - these are hardware limitations. Most units will be a 25hz panel.
The next 2 influences are data receive speed and any channel filtering. If you use OBD as your data stream, as covered its not fast enough for any meaningful use. On CAN, provided your receiving data at 20hz or faster, your not leaving anything on the table.
The next is any filtering. Some dashes give you the ability to adjust the channel filtering for its display output, some have defaults. This is because people will complain more often about a tacho that bounces around because it has no filtering, than one that some filtering applied. In this case check the settings in side the dash management software to see what you can adjust.
OE's in some cases adopted LCD as mechanical gauges could not keep up with the rate of engine speed acceleration (Lexus LFA)
For a further reference, here's a video from haltech directly comparing a factory cluster to their IC7 reviewing the same can data. The difference between the two - the signal filtering applied:
Ive got a hunch he's maybe talking about the refresh rate of numbers displayed? That's the only thing that would make sense? Having numbers that refresh 60 times a second is incredibly distracting, a good refresh rate for speed and rpm is more like 1hz IF you're talking about a numerical display