LT1 spec VS time slips... ?

[LastOfTheV8's]

Considering that the 1993 LT1 is rated as producing 300HP at the flywheel, and 340 ft lbs torque... why is it that when the car's (stock) quarter mile times and weight are put into a horsepower calculator (online) it gives much LOWER figures/less power ?
This is assuming stock C4's run the quarter mile at between 96 to 100 mph, and 13.6 to 14 secs flat. Apologies if i have the figures wrong here.. As for my own, she runs a consistent 0 - 100mph in 13.9 secs.
Maybe the horsepower calculator is at fault here ??
It concludes that my engine produces 260HP at the flywheel and 240 at the rear wheels.... wtf ??

Does anyone have a stock C4 vette that runs better numbers ? I have read somewhere that the horsepower of individual cars of that era can vary by as much as 30 to 50 bhp HIGHER ... God knows why!

 

[2VettesMike]

You may need to allow for drivetrain losses in the 15% range to get RWHP
You speed/times are online with what I have made in several passes as well.

Thanks
Mike

 

[rascal_rascal_99]

Just a thought, but whatever calculator/formula you're using to work up those numbers, are you adjusting correctly for the right gear ratio and also for having an independant rear end as opposed to a solid axle car?

 

[Stuart]

Just a thought, but whatever calculator/formula you're using to work up those numbers, are you adjusting correctly for the right gear ratio ...?

You definitely have to consider the axle ratio when looking at acceleration numbers. My 1993 6 speed has a 3.45 rear axle ratio (8.5 in. ring gear). This was installed by GM to improve MPG, not for low ET. It makes the car relatively slow off the line. There was a performance axle ratio available in 1993 but I’m not sure of the numbers. I’m sure there is someone else out there with that info.

 

[jamison]

Another factor to consider is elevation. I live 5,352 feet (1,631 m) above sea level. i have a 90 l98, it is suppose to do [FONT=&quot]14.3 @ 97.1mph at close to sea level. I only get mine to do 14.75 @ 90.7mph,
[/FONT]

 

[LastOfTheV8's]

Thanks guys. Thats interesting.. I hadnt thought of the axle ratio, I see that there were several available at the time.. how can I figure out which is fitted in my 1993 auto ??? Apologies if this is a stupid question! Concerning height above sea-level, that is also interesting how it affects the cars performance, I am at more or less right at sea level (living by the coast) so I am lucky in that regard. Thanks again.

 

[roger longman]

Yes but you know the Irish Sea is higher than other seas. Roger.

 

[surfer93]

You are assuming you car has 300HP, it might have more or more probably it has less. Wear and tear take there toll and how well it is tuned, all make a difference.
300HP is the average, I know of someone on another forum who has 289hp at the wheels and mine dyno'd when stock at just under 260, course the car had 130k + miles at the time.
What I am trying to say, is that all vettes are different and you can't go by what other peoples vettes do.

 

[LastOfTheV8's]

You are assuming you car has 300HP, it might have more or more probably it has less. Wear and tear take there toll and how well it is tuned, all make a difference.
300HP is the average, I know of someone on another forum who has 289hp at the wheels and mine dyno'd when stock at just under 260, course the car had 130k + miles at the time.
What I am trying to say, is that all vettes are different and you can't go by what other peoples vettes do.

On that note, can all dynos be assumed to record with the same accuracy? I am very curious to know what figures other c4 owners have received from dyno testing or quarter mile runs. Thats why I posted my 0-100 time, I am sure there are other stock C4's that perform better, due to all the reasons you stated. My question was why the online 'horsepower calculators' on various websites underestimate the vettes performance? I will be putting mine on a dyno (or two) in the new year and will post the results for comparison's sake. Thanks for the input. 260 at the rear wheels seems very good btw

 

[LastOfTheV8's]

Yes but you know the Irish Sea is higher than other seas. Roger.

Or is the land lower ? Hmmmm:confused

 

[roger longman]

Or is the land lower ? Hmmmm:confused

No, it's definitely the sea. The last time I was over,1966 for my honeymoon (I'm from London) I measured it when I got off the ferry. Oh maybe it's changed since then. Roger.

 

[LastOfTheV8's]

Another factor to consider is elevation. I live 5,352 feet (1,631 m) above sea level. i have a 90 l98, it is suppose to do [FONT=&quot]14.3 @ 97.1mph at close to sea level. I only get mine to do 14.75 @ 90.7mph,
[/FONT]

Thats some serious elevation! What octane fuel do you use? If you ever get to drive her closer to sea level do you notice much difference?

 

[surfer93]

Not all dyno's are the same, the formula for figuring HP and TQ are slightly different or some machines are not calibrated the same or maybe both.
I have seen a shop w/2 of the same dyno's have as much as 20hp difference, I do not know enough about them to tell you why, I have heard that Mustang dyno's are usually record HP and TQ nbrs on the high side.
If you want to know more, contact your local speed shop.

 

[LastOfTheV8's]

I would contact my local speed shop if they weren't fantasists waiting to tell me how poorly my 'old badly built american car' performs!! Is yours an auto? And if so have you ever had work done on your transmission? My 93 has 67,000miles and I have no idea what work should be carried out or when/how often regarding the transmission... I am concerned because it may be difficult for me to source those particular parts should the need arise. Thanks.


I just found a ''Quarter mile and trap speed calculator'' on 'Dragsource.com' that shows the numbers I would expect from a LT1 vette (in good condition!)
Taking vehicle curb weight (3239lbs -Wikipedia) plus my bodyweight (190lbs) to be 3429lbs, and the horsepower at the wheels to be 260; it predicts a quarter mile time of 13.76s @ 99.04mph
This is close to the time my own auto coupe consistently hits, 0-100 in 13.9s (over what distance I am not sure though..)
Question remains; is 260bhp a fair estimate for the 'average' LT1 vette at the rear wheels ?
Or have we established at this point that trying to use an average or base power figure to be subject to too much variation to be reliable ??
I think the only way I will find out is to take my 93 to the drag strip and leave about 3 litres of fuel in the tank:eyerole

 

[air1jpg]

I would contact my local speed shop if they weren't fantasists waiting to tell me how poorly my 'old badly built american car' performs!! Is yours an auto? And if so have you ever had work done on your transmission? My 93 has 67,000miles and I have no idea what work should be carried out or when/how often regarding the transmission... I am concerned because it may be difficult for me to source those particular parts should the need arise. Thanks.

At this point & mileage, the only thing you should have to worry about is getting the fluid & filter changed..

 

[roger longman]

Hi, My transmission gave out after 120,000 miles but I contrbuted to that by using it to rock the car out off mud. With proper use it should last indefinitely, as air1ipq says make sure you do the maintenance. As for petrol, the refining over here is nowhere nearly as good as the UK. Top octane is 91 and "dirty". Roger.

 

[LastOfTheV8's]

Hi, My transmission gave out after 120,000 miles but I contrbuted to that by using it to rock the car out off mud. With proper use it should last indefinitely, as air1ipq says make sure you do the maintenance. As for petrol, the refining over here is nowhere nearly as good as the UK. Top octane is 91 and "dirty". Roger.

Wow,, in all my talk of performance and spec I forgot to consider the fuel used, I live and work mainly in the south of Ireland, meaning the best fuel I can get is 95 octane, when I occasionally drive north (into the UK) I fill the tank with 98 octane which costs £1.18 GBP per litre, or $7 per US gallon if I have converted it correctly..
How does this compare with the average price of unleaded petrol in the US? And do you think we are mad to pay it ?? Thanks

What does it cost other vette owners to fill their tanks?
To fill mine with super unleaded 98 octane here in the UK (Northern Ireland) it would seem to cost the equivalent of $140 if the tank's capacity is 20 US gallons... Worth every cent if you ask me!

 

[roger longman]

Hi, we're paying around $3. a US gln in California, it was $1. 10 years ago and I paid 70cents in Iowa around that time. The Vette was made to run on 87 octane. There's no advantage to using higher grade, unless it's been "worked on". Roger.

 

[Towu4free]

as far as your gear ratio goes. look in your console lid where your RPO code sheet is it has a bunch of numbers and letters look for the G codes such as G80 (limited slip) you will have that one for sure look for G92 (performance axle ratio otherwise known as 3:07)if you see G92 then you will also see G44. it just means you have 3:07. if you do not see either one of these then you have the higher ratio which means slower acceleration. maybe a GU2 code.

 

[T.M.808]

You definitely have to consider the axle ratio when looking at acceleration numbers. My 1993 6 speed has a 3.45 rear axle ratio (8.5 in. ring gear). This was installed by GM to improve MPG, not for low ET. It makes the car relatively slow off the line. There was a performance axle ratio available in 1993 but I’m not sure of the numbers. I’m sure there is someone else out there with that info.

Well,the performance axle,is a 3:07 dana 33 for autos,the stock is 2:59 or 2:73. Yor car should be quiker with the 3:45's,in the much stronger dana 44.. all the stock 6 speed cars at our track,were always quiker than the autos just because they have the better ratio.. Of coarse this is assuming the 6 speed driver knows how to launch and shift the car for drag racing.