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  #16  
Old 02-06-2005, 10:57 PM
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i have hit 115 in mine. level ground and no tail wind

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  #17  
Old 02-07-2005, 12:37 AM
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Quote:
Originally Posted by Doktor Bert
Additionally, since the engine spends much of its time in the lower rpm ranges, 3.42:1 seemed a better choice than the factory's 3.23:1 the car came with...Bert
Bert,

No disagreement there. If you want to setup a vehicle for the maximum possible speed, without regard to low speed driveability, then it must just be able to hit the horsepower peak in top gear.

Many vehicles produced in the United States are geared lower than this for the exact reason you mentioned. They feel better in normal everyday driving.
This can result in exactly the situation that you have. The engine can push the vehicle down the back side of the horsepower curve, slightly. However, the falloff in torque is so dramatic in this area, that the vehicle quickly reaches equilibrium with the frictional forces of the wind.

My thought on the 617 is that it probably is setup very close to optimum for maximum speed with the 3.07 gears that most vehicles had up to 1985.

It would be very interesting to see if a 1985 300 SD has a lower top speed with the 2.88 gears. This would confirm that the 2.88 is too tall for the 617 in the SD body for achieving maximum possible speed.

If however, the SD with the 2.88 gears proves to be fastest, then, it would be conceivable that the SD with the 3.07 gears could achieve 4600 rpm on the back side of the horsepower curve. However, I have my doubts.
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  #18  
Old 02-07-2005, 02:16 AM
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Brian, I put it down about 2 months ago on my SD and it was right at about 4600 when I had to let off and exit. It was still climbing, but probably slower than I wish
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  #19  
Old 02-07-2005, 09:52 AM
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my car will hit 115 on level ground, then drop back to 107-110ish on an uphill climb....if anything, the 85's are faster than previous year models because of the gearing, not slower...i dont think a claim of 110mph top speed is bogus at all...i can hold mine there for hours at a time
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  #20  
Old 02-07-2005, 10:07 AM
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Quote:
Originally Posted by Pete Burton
Brian, I put it down about 2 months ago on my SD and it was right at about 4600 when I had to let off and exit. It was still climbing, but probably slower than I wish

Quote:
Originally Posted by 85drtysthbenz
my car will hit 115 on level ground, then drop back to 107-110ish on an uphill climb....if anything, the 85's are faster than previous year models because of the gearing, not slower...i dont think a claim of 110mph top speed is bogus at all...i can hold mine there for hours at a time

If the aforementioned statements are based upon actual values of speed, and the speedometer is not the instrument relied upon for measure, then, it appears that the vehicle with the 3.07 gears is geared to short and it is possible to slide down the back end of the horsepower curve with it. This would reflect on the fact that the 2.88 geared vehicle is apparently faster (115 mph). I am presuming that the horsepower peak is truly at 4400 rpm.

Although I find it practically amazing that these vehicles can do this with less than 125 hp, I cannot argue with the data (unless it's flawed) and, therefore, I stand corrected.
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  #21  
Old 02-07-2005, 10:36 AM
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Quote:
Originally Posted by Brian Carlton
Although I find it practically amazing that these vehicles can do this with less than 125 hp, I cannot argue with the data (unless it's flawed) and, therefore, I stand corrected.
I have to argue with you that you don't stand corrected! How's that? I'm only saying that my tach read 4600 but I don't know if it's right. Your analysis of the steep drop in speed capability based on available power is fine. I do not know how fast I was going, I do not know how much slippage I had in the torque converter, etc. The only thing I would venture to correct is that the aerodymamic portion of road load power increases as a function of the CUBE of car speed. Mechanical portions, such as rolling resistance are roughly linear. The sum of the 2 should represent the traction requirement you are correctly referring to. With the power needed rising exponentially and the power available, where they meet is where the top speed is. Once that point is reached, that's absolutely it, there is no more speed increase, unless you drive over a cliff!
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  #22  
Old 02-07-2005, 10:53 AM
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My original argument, Pete, is based on a horsepower peak of 4400 rpm. Above this number, horsepower is falling.

The horsepower requirement for a vehicle increases with the cube of the speed.

So, if I am travelling at 105 mph and I want to go 110 mph, then I need 15% more horsepower.

This means that, at the horsepower peak, there must be at least 20% more horsepower available than is required to push the vehicle (15% to go up to 110 mph and an estimated 5% drop in horsepower between 4400 and 4600 rpm). This would imply that the vehicle only requires 104 hp to travel at 110 mph. It would then have the required 125 hp to travel 115 mph. Each and every mph costs a bunch of power.

This is the fundamental reason why I feel it is "highly unlikely".

But, if the data is correct (and you have good reason to question it), then so be it.
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  #23  
Old 02-08-2005, 11:23 PM
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Total Loss Check:


ALERT! Severe damage events were reported by a DMV for this 1984 MERCEDES-BENZ 300SD (WDBCB20B1EA069784). This vehicle does NOT qualify for the CARFAX Buyback Guarantee.

Salvage Title Reported
No Loss Due To Fire Title Reported
No Junk Title Reported
Flood Damage Title Reported
No Rebuilt/Reconstructed Title Reported
No Hail Damage Title Reported
No Dismantled Title Reported
No Canadian Total Loss Record Reported

AZ, FL, GA, IL, MN, NJ, NM, NY, OK and OR issue Salvage Titles to identify severely damaged and/or stolen vehicles. Not all stolen vehicles are total losses; many can be recovered with minor or no damage. CARFAX recommends you have the vehicle inspected by your dealer or professional mechanic to assess the damage.

Other Accident Indicators:


This 1984 MERCEDES-BENZ 300SD (WDBCB20B1EA069784) had accident indicators reported to CARFAX from its sources. This section checks for accidents and/or related damage reported from many public and private sources. Not all accidents are reported to CARFAX. A vehicle inspection completed by your dealer or professional mechanic is recommended.

No Salvage Auction Record Reported No Crash Test Vehicle Record Reported
No Fire Damage Record Reported No Airbag Deployment Record Reported
Police Accident Record Reported No Damage Disclosure Record Reported


Accident Report Date: Source: Detail:
09/20/1993 New York Police Report Accident Reported
Vehicle involved in crash
in Richmond County
with another motor vehicle


New York Police Reports:
Do not include an assessment of damage severity
Are processed if the estimated damage exceeds $1000
Are released to CARFAX approximately 3 months after the accident date

According to the National Safety Council, Injury Facts, 2003 edition, 12% of the 243 million registered vehicles in the U.S. were involved in an accident in 2002. Over 90% of these were considered minor or moderate.
CARFAX depends on public and private sources for its accident data. Each one of these sources has different processing times. CARFAX can only report what is in our database on 08.Feb.2005 21:16:48. New data will result in a change to this report.
Not all accidents are reported to the Police. Tell us if you know of other fender benders, accidents or damage.

CARFAX Help Center
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  #24  
Old 02-09-2005, 08:16 PM
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  #25  
Old 02-09-2005, 10:37 PM
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I wouldn't trust a 20 year old speedo. I would like to see a digital pic of a GPS screen in one of these 300SD's doing 115. My SDL has 25 more hp and it might go a tick over 115 on a good day.
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  #26  
Old 02-09-2005, 11:35 PM
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KPM not MPH?
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  #27  
Old 02-10-2005, 12:09 AM
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Quote:
Originally Posted by Hatterasguy
I wouldn't trust a 20 year old speedo. I would like to see a digital pic of a GPS screen in one of these 300SD's doing 115. My SDL has 25 more hp and it might go a tick over 115 on a good day.
let me borrow your GPS for a few days and ill hook you up with some photos
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  #28  
Old 02-10-2005, 12:19 AM
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Quote:
Originally Posted by Brian Carlton
My original argument, Pete, is based on a horsepower peak of 4400 rpm. Above this number, horsepower is falling.

The horsepower requirement for a vehicle increases with the cube of the speed.

So, if I am travelling at 105 mph and I want to go 110 mph, then I need 15% more horsepower.

This means that, at the horsepower peak, there must be at least 20% more horsepower available than is required to push the vehicle (15% to go up to 110 mph and an estimated 5% drop in horsepower between 4400 and 4600 rpm). This would imply that the vehicle only requires 104 hp to travel at 110 mph. It would then have the required 125 hp to travel 115 mph. Each and every mph costs a bunch of power.

This is the fundamental reason why I feel it is "highly unlikely".

But, if the data is correct (and you have good reason to question it), then so be it.

As I recall, many years ago, there was a study done by Chrysler on the Dodge Daytona and they estimated that at 100 mph, it required roughtly 4 hp to go every 10 mph faster, based on that particular drag coefficient.

You are a virtual well of knowledge Brian...Bravo!!!....Bert
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  #29  
Old 02-10-2005, 12:35 AM
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Quote:
Originally Posted by Doktor Bert
As I recall, many years ago, there was a study done by Chrysler on the Dodge Daytona and they estimated that at 100 mph, it required roughtly 4 hp to go every 10 mph faster, based on that particular drag coefficient.

You are a virtual well of knowledge Brian...Bravo!!!....Bert
Well, Bert, I've got to tell you that the Chrysler study is dead wrong.

The force required to overcome the wind varies with the square of the speed.

Therefore the horsepower required to overcome the wind varies with the cube of the speed.

If you want to increase the vehicle speed from 100 mph to 110 mph, you need 33% more horsepower to do it. I suppose the study could be correct for a scale model that requires 12hp to go 100 mph, but, for any vehicle that is of a normal size, the number is more like 30hp for each 10 mph of additional speed (consideration given to an aerodynamic current design body).

In reality, the study must be mistaken, because I would only need an additional 40 hp to increase the speed from 100 mph to 150 mph. This is clearly ludicrous.

Your TransAm would be able to do about 400 mph using Chrysler's figures.
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  #30  
Old 02-10-2005, 05:22 PM
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I would need to look at the article again to be sure of the figures, but your version makes much more sense.

It's one of those puzzling things...like skid speed estimation when I went to CHP Accident Investigation School.

According to the calculations we learned during that course, vehicle weight had no bearing on skid distance. A 80,000 pound tractor/trailer and a 2700 pound VW Bug will skid the same distance, based solely on frictional coefficient of tire/roadway and velocity.

Interesting...Bert

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