NASCAR push rod engine vs. our AUDI DOHC engines
12-30-2002, 06:04 AM
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NASCAR push rod engine vs. our AUDI DOHC engines
NASCAR push rod is old fashioned tech. One of the reasons is to hold the engine cost down. I geuss the dark side secret is that NASCAR is for Americans only. I believe no other racing forces to use old fashioned push rod engines.
Among the domestic companies, GM somehow still makes push rod engine with turbo and w/o turbo. Buick's 3.8 L V6 engine is this engine, which has been around from early 1980s. The v6 was a measure to have a smaller engine by simply chapping of 2 cylinders from its popular V8 (305) engine, which is 5.0L engine. (Guess why domestic muscle cars are 5.0L -- mustang (not GM), Firebird, Camero, Corvette, etc. It was popular SMALL(!) V8 engine size).
The original form was not really refined at all. It produced about 110 HP out of 3.8L. However, GM has continuously updted this engine to about 200HP without turbo. One of the most amazing parts of this engine is very fuel efficient. It is surprising. It allows for a big GM full size car to achieve 30 HWY MPG.
For me, the 3.8L as well as the Corvette's Push Rod engine is the highly optimized old push rod engine. The GM's position is the traditional customers like to have the old style torque characteristics of push rod engines, which is high on low rpm. However, even the latest 3.8L is known to be anemic at the high RPM. The high RPM is not really high. It means around 5000RPM. I guess the traditioanl customers do not race their engines. Thus, this should be ok to them.
Yes, the Corvette engine and the NASCAR engine are good at high RPM not like the 3.8L push rod. They use exotic metals to overcome the limitations of push rod, which does not breathe well at a high RPM. It has a higher inertia of push rod compared to modern OHC, which introduces an issue of connecting the crank shaft and the cam shaft over the head, which is pretty long distance. Thus, gears have not been used, but chains and belts have been adopted.
If you ask me, I personally do not like push rod engine anyway although Push Rod engine tends to have a good low RPM torque. My rational is that if GM spend the same amount money on a new OHC engine, GM could have much better engine.
How about AUDI engines?
1.8T has five valves per cylinder with Double Overhead Cam shafts per block. (I-4 has one block anyway :-) 2.7T has two banks. Thus, it has total four Cam Shafts. Both have turbo charger(s).
What's the characteristics of these engines?
1. Even with the five values and the turbo charger(s), the low end torque is not so great as the domestic latest push rod engines. You might say that comparing 3.8L to 2.7L/1.8L is not fair. Yes, the torque is almost linearly propotional to the size of the engine w/o turbos. It is also well known that a multi-valve engine (2 valve of the old push rod engine) is low on torque at a low RPM.
Partly because of the above reason, variable valve timing is introduced. Thus, the first application of the variable valve timing is intake vales to overcome this weakness. Even so, IMHO, DOHC with multi-valves do not match the low end torque of that of old fashioned push rod engines. Audi's cleverness is adding a small quick spooling turbo charger to compensate this weakness.
Beyond the above advantage, the push rod engines are easily defeated by modern OHC multi-valve engines. These modern engines are happy to rev (thus, higher HP), and produces a good gas milage. (There is alwasy an exception -- GM 3.8L Push Rod, which is extremly gas efficient.)
Among the domestic companies, GM somehow still makes push rod engine with turbo and w/o turbo. Buick's 3.8 L V6 engine is this engine, which has been around from early 1980s. The v6 was a measure to have a smaller engine by simply chapping of 2 cylinders from its popular V8 (305) engine, which is 5.0L engine. (Guess why domestic muscle cars are 5.0L -- mustang (not GM), Firebird, Camero, Corvette, etc. It was popular SMALL(!) V8 engine size).
The original form was not really refined at all. It produced about 110 HP out of 3.8L. However, GM has continuously updted this engine to about 200HP without turbo. One of the most amazing parts of this engine is very fuel efficient. It is surprising. It allows for a big GM full size car to achieve 30 HWY MPG.
For me, the 3.8L as well as the Corvette's Push Rod engine is the highly optimized old push rod engine. The GM's position is the traditional customers like to have the old style torque characteristics of push rod engines, which is high on low rpm. However, even the latest 3.8L is known to be anemic at the high RPM. The high RPM is not really high. It means around 5000RPM. I guess the traditioanl customers do not race their engines. Thus, this should be ok to them.
Yes, the Corvette engine and the NASCAR engine are good at high RPM not like the 3.8L push rod. They use exotic metals to overcome the limitations of push rod, which does not breathe well at a high RPM. It has a higher inertia of push rod compared to modern OHC, which introduces an issue of connecting the crank shaft and the cam shaft over the head, which is pretty long distance. Thus, gears have not been used, but chains and belts have been adopted.
If you ask me, I personally do not like push rod engine anyway although Push Rod engine tends to have a good low RPM torque. My rational is that if GM spend the same amount money on a new OHC engine, GM could have much better engine.
How about AUDI engines?
1.8T has five valves per cylinder with Double Overhead Cam shafts per block. (I-4 has one block anyway :-) 2.7T has two banks. Thus, it has total four Cam Shafts. Both have turbo charger(s).
What's the characteristics of these engines?
1. Even with the five values and the turbo charger(s), the low end torque is not so great as the domestic latest push rod engines. You might say that comparing 3.8L to 2.7L/1.8L is not fair. Yes, the torque is almost linearly propotional to the size of the engine w/o turbos. It is also well known that a multi-valve engine (2 valve of the old push rod engine) is low on torque at a low RPM.
Partly because of the above reason, variable valve timing is introduced. Thus, the first application of the variable valve timing is intake vales to overcome this weakness. Even so, IMHO, DOHC with multi-valves do not match the low end torque of that of old fashioned push rod engines. Audi's cleverness is adding a small quick spooling turbo charger to compensate this weakness.
Beyond the above advantage, the push rod engines are easily defeated by modern OHC multi-valve engines. These modern engines are happy to rev (thus, higher HP), and produces a good gas milage. (There is alwasy an exception -- GM 3.8L Push Rod, which is extremly gas efficient.)
12-30-2002, 06:11 AM
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I think the big engines get good HIGWAY mileage because
of their super tall gearing. Most of those cars are at about 1500 RPM at normal highway speeds.
12-30-2002, 06:18 AM
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Holy rambling essays Batman...
On target though. Racing technology is the only thing that really interests me. Getting 700 horsepower out of an 8 liter engine isn't that exciting.
I happen to agree with Enzo, "Racing improves the breed." The end result of a successful motorsports program is to develop technology that will eventually find its way into your production cars.
Contrast the traditional racing formats to NASCAR: NASCAR rules mandate that every car must perform the same within very narrow tolerances. This is done in the name of competition, preventing one manufacturer from gaining a decided advantage over the others, making the races closer and more competitive. But it does nothing for the automotive state of the art. Ferrari dominates Formula-1 because their cars are better than everyone elses (and they have incredible drivers but one could argue that the best drivers are drawn to the teams with the best chance of winning a championship).
The term "stock car" in NASCAR is also misleading. Last time I checked I couldn't get a 500 horsepower Chevy anything at the dealer. European stock car challenges use what are essentially factory cars with roll cages, not tube-framed bodies, fiberglass panels, etc.
NASCAR is the Pro Wrestling of the motorsports world.
I happen to agree with Enzo, "Racing improves the breed." The end result of a successful motorsports program is to develop technology that will eventually find its way into your production cars.
Contrast the traditional racing formats to NASCAR: NASCAR rules mandate that every car must perform the same within very narrow tolerances. This is done in the name of competition, preventing one manufacturer from gaining a decided advantage over the others, making the races closer and more competitive. But it does nothing for the automotive state of the art. Ferrari dominates Formula-1 because their cars are better than everyone elses (and they have incredible drivers but one could argue that the best drivers are drawn to the teams with the best chance of winning a championship).
The term "stock car" in NASCAR is also misleading. Last time I checked I couldn't get a 500 horsepower Chevy anything at the dealer. European stock car challenges use what are essentially factory cars with roll cages, not tube-framed bodies, fiberglass panels, etc.
NASCAR is the Pro Wrestling of the motorsports world.
12-30-2002, 06:31 AM
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Other disadvantages of DOHC motors are size and weight ...
.
as you can see from these two Ford motors. Iron block pushrod motors often weigh less than a smaller aluminum block DOHC, so you better be getting additional performance for all the extra complexity and cost.
<img src="http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg">
as you can see from these two Ford motors. Iron block pushrod motors often weigh less than a smaller aluminum block DOHC, so you better be getting additional performance for all the extra complexity and cost.
<img src="http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg">
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12-30-2002, 06:42 AM
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Good point! I like the picture comparisons.
Yes, the Overhead CAM Shaft makes the head bigger and complex.
One idea has just strucked me:
The bigger DOHC gives a visual impression when we open a hood. Especially, a DOHC head is bigger than even a SOHC as well as a Push Rod Heads. What we see is the engine head not the cylinder block when we open the hood of our cars. Thus, we as well as our neighbors can be easily impressed by DOHC engines.
Theoretically, the cylinder block of push rod should be bigger than a DOHC cylinder block because the push rod usually go through the wall of the cylinder block wall. The DOHC does not have this piping. Again, this aspect is not easily visible when the hood is open.
Interestingly enough, the above aspect is not detacable from the pictures. Anyway, it is a very minor detail. Thanks again for your picture that surely explains many things to our A4 forum readers. One picture is worth of thousand words.
One idea has just strucked me:
The bigger DOHC gives a visual impression when we open a hood. Especially, a DOHC head is bigger than even a SOHC as well as a Push Rod Heads. What we see is the engine head not the cylinder block when we open the hood of our cars. Thus, we as well as our neighbors can be easily impressed by DOHC engines.
Theoretically, the cylinder block of push rod should be bigger than a DOHC cylinder block because the push rod usually go through the wall of the cylinder block wall. The DOHC does not have this piping. Again, this aspect is not easily visible when the hood is open.
Interestingly enough, the above aspect is not detacable from the pictures. Anyway, it is a very minor detail. Thanks again for your picture that surely explains many things to our A4 forum readers. One picture is worth of thousand words.
12-30-2002, 06:52 AM
#9
Ahhh...The Buick 3.8 is based on the Buick V-8 and not the Chevy. Geez do some research.
And no they didn't just take off two cylinders. Pushrod engines are tailored to American tastes. If you remember it was GM who came out with the first massed produced dual overhead cam 16v four (1976). No one bought it. GM came out with the first all aluminium V8 (1962) GM had the first turbo charged engine (1961) Dodge had the first electronic fuel injection. (1958?) I could go on but you get my point.
What you fail to understand is Americans have been there, done that. It's simple marketing and most Americans don't want it. The ones that do, go European or Japanese.
What you fail to understand is Americans have been there, done that. It's simple marketing and most Americans don't want it. The ones that do, go European or Japanese.
12-30-2002, 07:01 AM
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Re: Can we influence NASCAR?
I am with you. One of the reasons of auto racings is to explore new technologies, and eventually some of them find home under your and my hood.
I cannot deny NASCAR is the most profitable racing in US. I believe it raises the 2nd or 3rd most revenues. (The first is [American] football obviously.) In the engine tech point of view, NASCAR give little values to us -- ordinary customers except the fun and enjoyment while watching the NASCAR games.
Have you thought about how many spectators at the NASCAR games really know about the issue on the push rod engines? If they don't care about (or don't know) the issue, there is no reason to improve for the NASCAR racing official point of view.
What's the relevance to our AUDI people? I want to see stiffer competitions from domestic auto manufacturers. Who will be the eventual winner? That's us who will have even beter engines than now.
I cannot deny NASCAR is the most profitable racing in US. I believe it raises the 2nd or 3rd most revenues. (The first is [American] football obviously.) In the engine tech point of view, NASCAR give little values to us -- ordinary customers except the fun and enjoyment while watching the NASCAR games.
Have you thought about how many spectators at the NASCAR games really know about the issue on the push rod engines? If they don't care about (or don't know) the issue, there is no reason to improve for the NASCAR racing official point of view.
What's the relevance to our AUDI people? I want to see stiffer competitions from domestic auto manufacturers. Who will be the eventual winner? That's us who will have even beter engines than now.