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Why do some cars with similar mods and make similar hp numbers have large differences in torque? I tried to search but can't figure it out. like one car will make 700/650 and another will make 700/725?
Do both cars have ported blowers and the same pulley setup?
A non ported blower with a more aggressive pulley setup will usually make more torque than an x port blower with a less aggressive pulley setup. The ported blower shifts power to the right which and hits softer. The benefit of the ported blower with a less aggressive pulley is that it doesn't heat up as much and power doesn't fall off. And if you want to spin it harder you will make considerably more power vs a non ported blower.
Last edited by Internets_Ninja; Jan 15, 2024 at 09:27 AM.
Why do some cars with similar mods and make similar hp numbers have large differences in torque? I tried to search but can't figure it out. like one car will make 700/650 and another will make 700/725?
Why do some cars with similar mods and make similar hp numbers have large differences in torque? I tried to search but can't figure it out. like one car will make 700/650 and another will make 700/725?
because dynos are no different than any measuring device
They're only as accurate as the calibration and they can be intentionally calibrated either high or low, or like most probably never calibrated
they're really only useful as a baseline comparison on the same car before and after mods
take your car to 5 different dynos and you'll probably have a 20% range between 5 different readings
I'd go with never calibrated, the calibration necessary to get all dynos within a set small standard deviation is ridiculously expensive and unnecessary for your typical dyno operator/tuner. These numbers won't be going to SAE for approval and published as official statistical data reported by manufacturers so the need doesn't exist. The dyno is a tool for most operators as a tuning tool, you use it to ensure your build is on point for it's tune and it won't matter if its 20% lower than the dyno next door in that regard. If you want to know a closer number for your rwhp, take it to the track and see how your trap speed lines up. You need x amount of power to accelerate a weight down a 1/4 mile to y amount of speed. Weigh your car with you in it and about the amount of fuel you will run, then plug in the other number and your hp output will be accurate for those weather conditions.
It was just a general question wondering what engine component was making the difference. Whether it be a cam, ported blower, pulley size, diameter of header tube, fuel or what ever. I always try and learn as much as I can.
Even on the same dyno, small manufacturing differences can add up to a lot between cars. Because the majority of parts are mass produced within a tolerance range, so too will the final output numbers be a combination within the tolerances.
You could be on the short end of the stick where the heads had too much extra material within the passages lowering flow rate, manifolds with extra weld material, a differential on the tighter end of the tolerance adding extra drag, more viscous fluids in the oils adding more drag, the driveshaft/halfshafts or individual parts all on the heavier side of tolerance etc
Little number differences anywhere along the line can add up to more losses along the line until the dyno measures the power output so car a could hit 600whp while car b is a dog at 550whp.
It was just a general question wondering what engine component was making the difference. Whether it be a cam, ported blower, pulley size, diameter of header tube, fuel or what ever. I always try and learn as much as I can.
I see where you are coming from & learning / sharing is the basis for our furum. Ninja had a close explanation in line with your direction. You actually answered your own question with the examples of components you listed.
For example:
- Old school NA builds would live by bthe notion that larger tubes on headers would reduce some TQ & give more up top HP.
- a cam can be custom grind to fine tune where you want the power curve to be. To create more TQ with our PD blower, a cam with zero or small amount of overlap on inake & exhaust valve function will keep the boost in the combustion chamber & not blow out the exhaust.
- As Internets Ninja mentioned: a ported blower moves the power curve up to a higher RPM thus reducung the TQ down low.
All of the components of a build that you mentioned can effect the power curve. I'm not schooled enough into all the ways of moving the power curve but I'm sure other folks can chime in.
Horsepower is calculated using Torque -> Horsepower = (Torque X RPM)/5252.
An engine puts out Torque or twisting force and that is what is measured on a dyno. Horsepower is calculated from that and the number represents a point on the torque curve.
The shape of the Torque curve can vary greatly based on cam, airflow, supercharging, etc.
Below is a chart showing the Torque and Horsepower curves for three Corvette Engines, LT2 is in the C8 Stingray, LT6 is in the C8 Z06 and the LT4 is in the C7 Z06.
I added the Torque curve (bright red) and Horsepower (white) for the LT4 (my drawing with a mouse may be off a little).
The LT4 and LT6 have similar peak Horsepower but hugely different Torque curves. The C7 Z06 is extremely powerful at lower rpm's and carries much of that power to redline. The C8 Z06 has to be revved up to get into its power band - it is faster on the track because it can stay in a lower gear longer, not because it makes significantly more power.
In my opinion, the LT4 is much more responsive and fun to drive for non-track driving compared to the LT6, and is very close to the LT6 on the track. I am surprised by how weak the LT6 is below 3,000 rpm.
Last edited by Dave McDufford; Jan 15, 2024 at 11:53 AM.
So a more efficient flowing setup will make more hp and less torque? I know the torque curve on my car is pretty flat and makes great power for the little mods done to it.
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Question about torque numbers
