big dave

My car dynoed 296 rwhp stock and ran 13.28@105 in good air. The car has run 12.2s@ 115mph in good air with the listed boltons with a best of 12.02@116.5 in very good air. I know there is no way my car is making 390 rwhp with bolt-ons. How can the mph be explained?

Raceweight hasn't changed and the mileage is now 146k. I know the ls1s get stronger with miles but ...

I thought every mph is worth 10 hp.

sciff5

iTrader: (1)

Thats ricer math

Most quarter mile calculators say that my car at 3000lb race weight which is what it is I should need 400+ whp to run the quarter mile times I did with a stock ls1 with exhaust and ported TB. Putting out good numbers but still a reasonable 335 whp

30th t/a

iTrader: (51)

what was the DA when you trapped 116? Were you running at Cecil? I always hear that track is known for trapping high mph.

big dave

Yup, cecil. I've trapped 115 at other tracks though. The DA was -1500 which explains the high mph.

WeathermanShawn

iTrader: (1)

Yea, I am not always sure that 10HP equals 1 mph 'rule' is always valid. You have aerodynamic drag, rolling resistance, DA, driver skill, etc.

I would not put 100% faith in those estimated HP calculators. A lot of assumptions. For fun, you can always hook a a G-Tech device (or similar) and just go with the concept of 'net horsepower'. The numbers will humble you, but it is in actuality a pretty valid way of calculating 'to the road' HP.

Hope that helps.

..WeathermanShawn..

MikeG

iTrader: (33)

The 10hp = 1mph thing is just a rough guideline. Don't put too much stock in it. If it were true then a stock SS with 300rwhp that runs 105 mph would automatically trap 145 with 700rwhp. And we all know that's not necessarily the case.

My car also made 296 when stock. It trapped 104 mph. I only have bolt ons now as well and my last dyno was 354rwhp. Now I trap 115+ in similar air. My car weighs about 150-175 lbs less now than stock.

I think your car is 'overachieving' because it has better gearing, more power under the curve, and you're probably better at driving the car now than when you first got it.

aTeam

ls1s get stronger with miles?

big dave

Thanks for the replies. I was just curious to find out what a more accurate equation would be to guesstimate hp/mph/weight. I know the numbers don't add up but what are all the online calculators using in their formulas to come up with their answers?

WeathermanShawn

iTrader: (1)

Not my equation. It is a common equation to estimate HP. The equations can get complicated, and their accuracy is not 100%.

..Google search..

Solving for engine horsepower using the trap speed method.


Remember, getting good air is an huge advantage. Our track (Bandimere) is at 5800', with DA's running 7000+, depending on temperature. I trap at 110.5 mph with my setup. The calculators always seem to overestimate my HP also.

Perhaps someone can share if they have a different formula, or a better way to estimate HP by Trap Speed.

..WeathermanShawn..

silverz28camaro

iTrader: (20)

Don't forget that your gears alone help with mph and et. Just a gear change in my car made me go from 12.9 @ 109 to a 12.6 @ 110, no hp difference, just a mechanical advantage.

Also thhink about your headers, even though they may only get you 20hp, they also save weight.

Don;t always look at hp peak numbers. Lets say you have a car that makes 370hp @ 6,000 rpm. Now take that same car and put a bigger cam in it...now 400hp At 6,400 rpm. even though you only gained 30 hp from peak numbers, the differenve at 6400 now vs 6400 then may be 50hp since the other cam started falling off and not pulling harder for longer. this is what happened after my cam swap.

I thought I gained only 30 hp, but the car somehow went from 11.5 @ 117 to a 10.9 @ 123. looking at the dyno sheet befroe and after, the difference was 60hp at 6,400 rpm, giving my the 6 mph and .6 in the 1/4.

your car may only have gained 40rwhp, but now that you have gears, and the difference at 6,000 may be greater then 40hp.

Get the car dynoed again and look at the old sheet or overlap them if you can.

Brads LS1 02Z

iTrader: (16)

the 4.10s probably added as much as the bolt ons