[DeTomaso] Speedometer Calibration Problem GT5-S Amerisport 1987

[thomas]

14 jul 2012 kl. 18:25 skrev Julian Kift <julian_kift at hotmail.com>:

> 
> I believe there are actually a number of permutations that could be at fault here.
> 
> 1. There are the two brands of angle adapter (Borletti and VDO), but each brand is available in two ratios, 1:1 and 1.1:1 IIRC. Later cars are typically using a VDO angle drive.

Actually I believe VDO was used on early cars, and Borletti on the later cars.

Notice also that the different brand angle drives require different speedo cables. 

> 2. Two speedometer revolutions are also available 1600 revs per mile and 1200 revs per mile (or something close to that for each)

I believe it is 1210 vs 1610 revs per mile. 


> 3. To compound those computations further speedo face plates are often changed, so if (like my GT5) this car was originally a Euro car with km/hr speedo someone may have innocently just changed faceplate to mph (this is was what happened to my GT5) assuming all would be good and it's not.
> 
> Establishing what you have for speedo and angle drive is a good starting point as I imagine you have a mismatch somewhere being so far out on indicated vs. actual speed. Modern vs. original spec tire diameters are typically going to give within a 10% error.

I assume you have a MPH speedo, then the problem is consistent with having an angle drive for a KPH speedo. 

My cousin had the opposite problem with his KPH speedo and US spec angle drive. It showed way over, and the problem was solved when he got a proper angle drive. 

Cheers,
Thomas

> 
> Good luck,
> Julian
> 
>> From: MikeLDrew at aol.com
>> Date: Sat, 14 Jul 2012 11:59:19 -0400
>> To: montana at montanas.com; detomaso at realbig.com
>> Subject: Re: [DeTomaso] Speedometer Calibration Problem GT5-S Amerisport 1987
>> 
>> 
>> In a message dated 7/14/12 8:12:50 AM, montana at montanas.com writes:
>> 
>> 
>>> I am restoring a 1987 GT5-S and have had the speedometer calibrated 3 
>>> times
>>> and it still remains approximately 135 % under reading versus actual 
>>> speed.
>>> ( Gauge-55, GPS-75, Error 20, Ration-136.4%)  This error factor remains
>>> constant through the 30-70 gauge test.
>>> The mileage and the odometer test results in 8.0 miles reading versus 
>>> actual
>>> 10 miles traveled.  The 52 ft., 9 & 1/2 in. cable rotation test is 12.63
>>> turns within the test distance.
>>> Advice would be most appreciated.  Ken Montana, Biloxi, MS, USA,
>>> 228-832-1313, montana at montanas.com
>>> 
>> 
>> Ken--the Pantera originally came with tires that were 27-ish inches tall 
>> and the speedos were calibrated thusly.   Cars like yours fitted with original 
>> wheels and 24-inch tires will therefore normally register much higher at a 
>> given actual speed because the rear wheels are turning faster to travel at 
>> the same groundspeed.
>> 
>> It sounds like somebody has attempted to correct for this by fitting a 
>> different angle drive to the speedometer, OR installing some sort of correction 
>> box in the middle of the system somewhere (likely behind the dash).   But 
>> clearly it's not working--or rather, it's working TOO well.
>> 
>> Notice the two different styles of speedo adapter, seen here:
>> 
>> http://www.panterasbywilkinson.com/webpages/catalog/ill10c.html
>> 
>> There are also two different VDO adapters with different characteristics.   
>> I have to admit that I can't remember ever actually seeing a VDO-style 
>> adapter; every car I've paid attention to has had the Borletti style.
>> 
>> What do you have?
>> 
>> As an aside, I wish I had known you were there in Biloxi--Lori and I were 
>> just there for a week, two weeks ago, visiting her son who is a special ops 
>> boat guy (like in the movie "Act of Valor") and stationed at the Stennis 
>> Space Center.   We'll have to try to get together next time we come out there 
>> for a visit....
>> 
>> Mike
>> _______________________________________________
>> 
>> Detomaso Forum Managed by POCA
>> 
>> Archive Search Engine Now Available at http://www.realbig.com/detomaso/
>> 
>> DeTomaso mailing list
>> DeTomaso at list.realbig.com
>> http://list.realbig.com/mailman/listinfo/detomaso
>                         
> _______________________________________________
> 
> Detomaso Forum Managed by POCA
> 
> Archive Search Engine Now Available at http://www.realbig.com/detomaso/
> 
> DeTomaso mailing list
> DeTomaso at list.realbig.com
> http://list.realbig.com/mailman/listinfo/detomaso
> 
> !DSPAM:50019db18029021468!
>