N/A vs. Forced Induction
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
N/A vs. Forced Induction
Say both cars being equal ... same year, make, tire size, gears, tranny...etc.
If both cars have the same hp (400 rwhp) , but one car is a head/cam naturally aspirated car whereas the other car is a forced induction supercharged car.... how would these cars differ at the track (driver not being an issue)?
If both cars have the same hp (400 rwhp) , but one car is a head/cam naturally aspirated car whereas the other car is a forced induction supercharged car.... how would these cars differ at the track (driver not being an issue)?
Le Mans Master
Joined: Aug 2004
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From: Metairie Louisiana
Team Owner
Joined: Oct 2004
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
I think the answer to the question is TORQUE. Sure, HP keeps you moving, but torque gets you moving.
I would think that FI has a flatter, higher torque curve, hence the advantage.
But there's a lot of factors. Is the cam matched to the intake, matched to the heads?
A HP number out of context is meaningless.
I would think that FI has a flatter, higher torque curve, hence the advantage.
But there's a lot of factors. Is the cam matched to the intake, matched to the heads?
A HP number out of context is meaningless.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by black_89_vette
Say both cars being equal ... same year, make, tire size, gears, tranny...etc.
If both cars have the same hp (400 rwhp) , but one car is a head/cam naturally aspirated car whereas the other car is a forced induction supercharged car.... how would these cars differ at the track (driver not being an issue)?
If both cars have the same hp (400 rwhp) , but one car is a head/cam naturally aspirated car whereas the other car is a forced induction supercharged car.... how would these cars differ at the track (driver not being an issue)?
RACE ON!!!
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
Typically, a 400 RWHP NA car will turn a faster time than a 400 RWHP supercharged car; if both are equipped with a manual transmission. There are exceptions, but normally that's the case. I would also say that typically a 400 RWHP turbo car won't produce the killer ET's that an NA car will, but it will most likely produce the highest MPH of the bunch; again, with a manual transmission.
ET is almost all about launching the car. The NA, stick shift car will launch better for a few reasons:
There is no lag. The power is literally instantaneous.
The car will be lighter. The supercharger set up will add at least 60 lbs. to the front of the car. That's the last place you want weight when trying to effectively launch the car.
With an automatic, I think I'd give the nod to the turbo car in both ET and MPH.
Pro
Joined: Jan 2004
Posts: 707
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From: Syracuse Utah
I agree with jsup and the other guys--torque curve and hp curve will be different. All other things being equal, the NA engine will have a flatter curve. Power adders usually impede airflow until rpm reaches a certain speed, then power builds rapidly so it has a sharper peak.
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Drifting
Joined: Aug 2006
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From: Los Angeles California
All the extra crap you have to put in the engine bay to turbo the car isn't weightless. If the setup results in both cars having equal torque curves in all conditions, the big weight advantage will give NA a significant performance edge.
Burning Brakes
Joined: Oct 2006
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I agree with the above. I depends entierly on the curves. That being said "typicaly" a NA motor will have flat curve and have a higher average hp and trq the supercharged/ tubo car will have a more exagerated increase later in the rpm band. But that being said et's would beteen the two cars will depend more on driver and driveline configuration (gear ratios) than anything. It will be six one way half a dozen the other. If you are asking to decide wich route to go my 0.02 is rebuild the engine with a 355 forged low cr around 9 try to get a solid cam/ head setup for around 400 crank and then you will still have the option of forced air. When I did my 383 build I went with cast crank and hyper pistons with an estimated 10.9 cr I like the car but I still want more thats the problem with this disease (upgrading hp) you will never be satisfied.
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
If the rest of the car is optimized, Im saying the NA car is more likely to be the fastest. The reason is, he only said both have the same RWHP.
What I am getting at, you can easly make that kind of power with a blower and a stock motor. But the power band is going to be in the lower rpm range so you will not be able to use gears as well to multiply the power to the rear wheels as well as you could with a higher reving motor.
That is the reason you can throw a set of 3.73 gears and a stall converter in a stock LT1 and it will run 12's. You cant do that with a L98. The L98 will peak (stock) around 4500 rpms and a LT1 will peak around 5700. Therefore you can use gears to make the car faster.
With this in mind, the 400hp blower motor may redline around 4500 or 5700 depending on which motor you had, but the 400hp na motor most likely will rev to at least 6500 and possibably more.
Also, this is assuming we are comparing c-4 vettes
What I am getting at, you can easly make that kind of power with a blower and a stock motor. But the power band is going to be in the lower rpm range so you will not be able to use gears as well to multiply the power to the rear wheels as well as you could with a higher reving motor.
That is the reason you can throw a set of 3.73 gears and a stall converter in a stock LT1 and it will run 12's. You cant do that with a L98. The L98 will peak (stock) around 4500 rpms and a LT1 will peak around 5700. Therefore you can use gears to make the car faster.
With this in mind, the 400hp blower motor may redline around 4500 or 5700 depending on which motor you had, but the 400hp na motor most likely will rev to at least 6500 and possibably more.
Also, this is assuming we are comparing c-4 vettes
Melting Slicks
Joined: Mar 2001
Posts: 2,148
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From: Timra, Sweden
At the same power level the turbo engine would be WAY more reliable if the same engine parts are used.
The major differance is engine RPM.
I have used my corvette a lot this summer and I have driven it hard.
This weekend I ran 6 times at a temporary race track 110 miles away.
My best ET were 11.14 sec and I ran that twice. 11.24 sec once. The other three runs were 11.42, 11.43 and 11.45 seconds.
My best trap speed was 131 mph and my 1984 Corvette is not lighter than stock.
You do the math but my rwhp must be quite high.
http://www.race-cars.net/calculators/et_calculator.html
My tranmission is a 4L80E and that takes some hp to turn.
I shift at 5300 RPM, below the stock redline.
I still have the stock engine block, stock crank, stock rods and stock pistons.
I would like to see a N/A engine stay together at that power level using the stock bottom end that were put in the engine by GM 25 years ago.
The major differance is engine RPM.
I have used my corvette a lot this summer and I have driven it hard.
This weekend I ran 6 times at a temporary race track 110 miles away.
My best ET were 11.14 sec and I ran that twice. 11.24 sec once. The other three runs were 11.42, 11.43 and 11.45 seconds.
My best trap speed was 131 mph and my 1984 Corvette is not lighter than stock.
You do the math but my rwhp must be quite high.
http://www.race-cars.net/calculators/et_calculator.html
My tranmission is a 4L80E and that takes some hp to turn.
I shift at 5300 RPM, below the stock redline.
I still have the stock engine block, stock crank, stock rods and stock pistons.
I would like to see a N/A engine stay together at that power level using the stock bottom end that were put in the engine by GM 25 years ago.