Variance between Speedo and DIC after cal with GPS?

[krunchss]

I guess basically my question is does the DIC and the actual speedometer needle get their data from the same place?

I calibrated my DIC tonight with a GPS. I never really looked at the speedo needle at all until I was finished. I figured I would cal my speed to the average speed displayed in the DIC as it was digital and had a decimal point thinking this would give me the best accuracy.

Well, I got it to a point where I would get up to speed on the highway, hit cruise control, reset the speed data on teh GPS and DIC, and after about 2 minutes the average speed on the GPS and the DIC settle in, they stayed identical for about another 10 minutes of cruise control driving. PERFECT!

Well once i had that done, I was just playing and set cruise @ 111 km/hr (according to gps / DIC) and the speedo needle was reading about 108 km/hr to me.

Now that's less than a 3% error between them, but is there anything wrong with either my DIC or Speedo you figure?

Krunch

[krunchss]

31 views and no comments wow.

Krunch

[JerryH]

Yes and no.

Though they get the info from the same area (PCM), the mechanical differences between the speedo needle springs and what not are never going to be as precise as the DIC or HUD readout (within it's + or - 1 MPH capabilities).

Use the GPS to match the HUD and let the speedo fall where it may and just take note of where it falls in relation to the HUD. It will be quite close anyways, but that difference may also vary a little at different MPH.

Not meaning to disappoint anyone here, but I think people already know that life has pretty much swamped me with WAY more than I can (almost) handle. This leaves me with no time to devote to my hobbies... so with that, if I am absent here, it is not because I am being rude, it is simply that I no longer have the time available to participate here as much as I would wish.

Have a nice one folks... I will pop in if and whenever I can.

[krunchss]

Thanx Jerry for taking the time to post a reply to this. I too have been very busy with work and summer household projects and I only figured out my wiring issue causing failed writes for almost two years, this week! Well, I figured out a way around it...but I digress.

I suspected the response to my question would be what you stated Jerry, was just looking for confirmation before moving on. I have waited so long to start tuning, I didn't want to move on only to backtrack later, especially this late in the season.

Basically I am experiencing exactly what you say Jerry. "Needle" is a tiny bit out at SOME speeds. I will leave it.

Hopefully on to DIC calibration via IFR this weekend!

Thanx,
Krunch

[bilemke]

Confirm that.. I can get the HUD spot on.. The needle is always a bit high. Works good though.. If I am concerned enough to be looking down at the needle (vs HUD) because I think I might be speeding, it always scares me in to slowing down just a bit. This usually happens when I see a cop car ahead.

[krunchss]

See I have the opposite problem. my needle is a bit LOW. I always push the limits of the speed limit, and seem to have found a sweet spot where if need be, I can get somewhere a little faster WITHOUT getting a ticket. For many years I have experienced driving 109 km/hr in a 100 km/hr zone I have never been bothered by police. I've heard / experienced that tickets kick in here in Canada, on average, of 11 km/hr over the limit. In reality, I was likely driving 105 km/hr to 107 km/hr and thinking I was actually going 109 km/hr. Now when my DIC (HUD) reads 110 km/hr, my needle shows about 107 km/hr to 108 km/hr, hence, if I set my cruise via the needle, I'll be going about 111 km/hr to maybe 114 km/hr...WHOOPS!

Like Jerry said, I'm gonna live with it and figure out my new needle speed based on the DIC (HUD). It's a little anal on the tuning side, but I am a perfectionist in almost everything I do.

Krunch

Confirm that.. I can get the HUD spot on.. The needle is always a bit high. Works good though.. If I am concerned enough to be looking down at the needle (vs HUD) because I think I might be speeding, it always scares me in to slowing down just a bit. This usually happens when I see a cop car ahead.

[JerryH]

Not so oddly enough, tire tread wear will also be a factor. A fresh tire with full height thread will read differently from a tire on it's last thousand miles. As the tire wears, it goes off slowly more and more.

Different cars will have different results. Don't let it get to you too much... knowledge is being able to compensate for your needs.