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I have a 4age turbo conversion into my old Toyota. I am planning to run my original cable driven speedo in the dash. I am going to run a MaxxEcu and I was wondering if there would be any added advantages of having a GPS speed sensor installed to give speed data to my ecu? I have been looking at the haltech speed sensors. But I’m not sure as this is all new to me if there are settings and actions that would benefit from having speed input.
Thanks in advance
You can add digital pickups that mount on the cable drive at the box end, I use these a lot on 4EFTE Starlet/Glanza's, it's either that or I take the digital signal the dash puts out into the ECU but this can be noisy.
GPS is great if you have a high-speed setup but most are too slow to give any real-time speed, especially from stationary. I have used the Haltech GPS speed sensor on road cars in a pinch where they've converted their driveline but it's not a preferred choice.
A few common uses are:
Speed can be useful for many things such as knowing whether you're moving or not for idle, launch, flat shift related items.
How fast you're moving can be correlated with engine speed to determine which gear you are in, and then you can use gear based compensations to further refine your tune.
Depending on what you'd like to do with the speed data, GPS may or may not be sufficient for your needs. Admittedly I'm also not aware of how good the GPS coverage is in your area, so that may be worth a quick check.
I find that GPS has too much of a lag to be really useful for speed based calculations/activation's, especially compared to a wired sensor. GPS when you are stationary has a habit of "floating" (unless it is heavily filtered) around 0, so if your launch control system requires that the vehicles speed is below a certain value, or to be stable, then you can have situations where the Launch or other function will not activate as the speed is not in the correct window. When you start moving, there is also a delay in the GPS responding to this, so if you have the Launch Engine Speed Limit increasing based off of the Vehicle Speed, then you could have the limit being reduced more than is wanted as the GPS is lagging behind the vehicle.
GPS should also not be used for trip/Odo readings, when the GPS is first starting and is reading more satellites, as it is narrowing its accuracy window, you can have quite high speeds being recorded, this will potentially add multiple km's to your meters. I have a Dash on my desk that has a faulty GPS attached to it, so it is constantly restarting and reacquiring signals, it currently has an odo reading in the 9 billion km range due to this.