Ok then, so here's the ultimate question on turbo vs. non-turbo:
09-21-1999, 09:09 PM
#1
Guest
Posts: n/a
Ok then, so here's the ultimate question on turbo vs. non-turbo:
I thought this was a no-brainer, but with all the response I've receive below, and how much I've learned about fans in the last 10 hours, I have to ask:
If there were two *identically performing* cars in terms of numbers, power, 0-60, 1/4 mi, top end, etc, and one was turbo with moderate lag, and the other was un-forced, with (obviously) no lag, which one would you prefer?
And no, you can't put your own turbo on my hypothetically unforced car... And yes, the turbo is "already chipped".
As I said, I assumed *everyone* would take the non-turbo. But maybe I'm about to learn something else new...
If there were two *identically performing* cars in terms of numbers, power, 0-60, 1/4 mi, top end, etc, and one was turbo with moderate lag, and the other was un-forced, with (obviously) no lag, which one would you prefer?
And no, you can't put your own turbo on my hypothetically unforced car... And yes, the turbo is "already chipped".
As I said, I assumed *everyone* would take the non-turbo. But maybe I'm about to learn something else new...
09-21-1999, 10:32 PM
#3
Guest
Posts: n/a
Turbo vs. Non-turbo (LONG)
Avram:
First of all, what is "moderate" lag? I have driven many turbo-charged cars and all have some amount of lag. It is my opinion that Audi has gone to great expense and effort by using twin turbos to eliminate lag to the greatest extent possible. Try driving a car with just one larger turbo sometime. You will appreciate the S4 after that, I guarantee it.
Normally, you would definitely want the "naturally aspirated" engine, because a turbo puts more stress on an engine and DOES shorten it's life between rebuilds somewhat vs. a non-turbo engine, due to the greater stress and heat. Internal components have to be upgraded to handle the additional stresses, also. Not ALL things would be equal, though. A turbo-charged engine can be smaller and still produce equivalent amounts of power compared to a larger engine, thus resulting in weight and fuel-savings. Ever driven a Buick GSX Grand National? It's turbo-charged V-6 regularly puts naturally aspirated MUCH larger cubic inch V-8's to shame at the drag strip.
I would have a turbo-charged engine (and I DO have an S-4 Tiptronic on order) for two reasons:
1. I enjoy the "rush" that you feel when a turbo-charged engine "goes positive" and really starts making boost. There is no feeling that compares to it in a non-turbo-charged car, although some hotter cammed cars come close when they "come up on the cam". I DO wish the S4 came with a boost gauge, though, as I also enjoy watching the gauge "go positive" at the same time the rush kicks in. Although it's not necessary with today's computer controls, I think it should at least be an option.
2. I live "at altitude", i.e. 7,400 ft., 1/2 mile ABOVE Denver. I regularly go into the mountains, where you can go up to 11,000 ft. when going through Eisenhower Tunnel. At Denver, a naturally aspirated car is down on power approximately 25% from sea level and it gets worse from there. At 11,000 ft., you are down on power 50% vs. sea level due to the much thinner air.
A turbo-charged car helps make up for that power loss, especially if you have a car with a barometric-pressure controlled waste-gate, as Audis have since they learned its' need during the Pikes Peak races years ago. To make a long story short, if you live several thousand feet (or more) above sea level or have to go there (skiing anyone?), a turbo-charged car can make the drive MUCH more pleasurable by making the engine think it's at a lower altitude. It will actually run more efficiently and will not be struggling up hills.
Therefore, all other things being equal, ALWAYS go for a naturally aspirated engine when possible. However, it is NOT always the answer.
As for turbo-lag, the S4 is NOTHING compared to the lag my 180 HP '65 Turbo Corvair had. I fail to see how twin turbos that come into power at just under 2,000 rpm can be considered "moderate lag", though. My Corvair didn't come into boost until around 3,500 rpm, partly because it only had one large turbocharger. Talk about lag!
For the record, an automatic usually helps cover turbo "lag" because it can always shift faster and better than you can with a six-speed manual. Even a slight delay (i.e.,during a normal manual shift) will cause the turbos to spool down slightly, from which they will have to re-accelerate, thus causing lag. I think a properly set-up Tiptronic (i.e., with a Garrett transmission chip) would actually be faster than a six speed if they both had the same final drive ratio. Downshifting with a Tiptronic should be faster and incur less lag, too.
Hope this answer helps and is not redundant to early postings I have not had time to read.
Reed
First of all, what is "moderate" lag? I have driven many turbo-charged cars and all have some amount of lag. It is my opinion that Audi has gone to great expense and effort by using twin turbos to eliminate lag to the greatest extent possible. Try driving a car with just one larger turbo sometime. You will appreciate the S4 after that, I guarantee it.
Normally, you would definitely want the "naturally aspirated" engine, because a turbo puts more stress on an engine and DOES shorten it's life between rebuilds somewhat vs. a non-turbo engine, due to the greater stress and heat. Internal components have to be upgraded to handle the additional stresses, also. Not ALL things would be equal, though. A turbo-charged engine can be smaller and still produce equivalent amounts of power compared to a larger engine, thus resulting in weight and fuel-savings. Ever driven a Buick GSX Grand National? It's turbo-charged V-6 regularly puts naturally aspirated MUCH larger cubic inch V-8's to shame at the drag strip.
I would have a turbo-charged engine (and I DO have an S-4 Tiptronic on order) for two reasons:
1. I enjoy the "rush" that you feel when a turbo-charged engine "goes positive" and really starts making boost. There is no feeling that compares to it in a non-turbo-charged car, although some hotter cammed cars come close when they "come up on the cam". I DO wish the S4 came with a boost gauge, though, as I also enjoy watching the gauge "go positive" at the same time the rush kicks in. Although it's not necessary with today's computer controls, I think it should at least be an option.
2. I live "at altitude", i.e. 7,400 ft., 1/2 mile ABOVE Denver. I regularly go into the mountains, where you can go up to 11,000 ft. when going through Eisenhower Tunnel. At Denver, a naturally aspirated car is down on power approximately 25% from sea level and it gets worse from there. At 11,000 ft., you are down on power 50% vs. sea level due to the much thinner air.
A turbo-charged car helps make up for that power loss, especially if you have a car with a barometric-pressure controlled waste-gate, as Audis have since they learned its' need during the Pikes Peak races years ago. To make a long story short, if you live several thousand feet (or more) above sea level or have to go there (skiing anyone?), a turbo-charged car can make the drive MUCH more pleasurable by making the engine think it's at a lower altitude. It will actually run more efficiently and will not be struggling up hills.
Therefore, all other things being equal, ALWAYS go for a naturally aspirated engine when possible. However, it is NOT always the answer.
As for turbo-lag, the S4 is NOTHING compared to the lag my 180 HP '65 Turbo Corvair had. I fail to see how twin turbos that come into power at just under 2,000 rpm can be considered "moderate lag", though. My Corvair didn't come into boost until around 3,500 rpm, partly because it only had one large turbocharger. Talk about lag!
For the record, an automatic usually helps cover turbo "lag" because it can always shift faster and better than you can with a six-speed manual. Even a slight delay (i.e.,during a normal manual shift) will cause the turbos to spool down slightly, from which they will have to re-accelerate, thus causing lag. I think a properly set-up Tiptronic (i.e., with a Garrett transmission chip) would actually be faster than a six speed if they both had the same final drive ratio. Downshifting with a Tiptronic should be faster and incur less lag, too.
Hope this answer helps and is not redundant to early postings I have not had time to read.
Reed
09-21-1999, 11:49 PM
#4
Guest
Posts: n/a
TURBO! It's more than just chipping. You...
...can change the turbos, intercooler, etc. still, even after chipping. Most modern turbocharged cars have very little lag, so moderate isn't really a word I'd throw around much anymore. It's a rush when the turbo comes on line, and I love the sound turbos make. Now, if our normally aspirated competitor is an awesome BMW inline 6, I would have a more difficult time choosing. Hmmmmmm!!! :-)
Charles
Charles
09-22-1999, 02:44 AM
#6
Guest
Posts: n/a
A writer with both M3 and S4 experience had an interesting analysis...
He said that unless you were driving around above 4000 RPM all the time the M3 was a pooch compared to the S4. The small turbo lag is nothing in comparison to trying to get the RPMs up on a high-strung engine.
The other option, of course, is more cubic inches. You then get more instantantaneous power, at the expense of weight, economy, etc. A small turbocharged engine is light and efficient. You don't pay the price for the power unless you use the power. My S4 is telling me that I'm getting 30MPG while cruising at 70 on level ground.
The other option, of course, is more cubic inches. You then get more instantantaneous power, at the expense of weight, economy, etc. A small turbocharged engine is light and efficient. You don't pay the price for the power unless you use the power. My S4 is telling me that I'm getting 30MPG while cruising at 70 on level ground.
Trending Topics
09-22-1999, 05:00 AM
#8
Guest
Posts: n/a
Re: Ok then, so here's the ultimate question on turbo vs. non-turbo:
After driving both turbo and non turbo sports cars for quite a while.
If the dyno chart was exactly the same, I would most definitely choose the non turbo. As long as they were the same weight. Unfortunately this will not be the case.
Hypothetical situations rarely happen in real life, but... Here is what I belive. The rush everyone talks about could be there in a normally aspirated big engined car, but you pay a price. To get to those power levels, while remaining streetable, you need to increase the weight of the engine dramatically (big block v6) unfortunately the engine peices would be extreamly heavy. Which would limit your RPM along with not having terribly good flow. So they switch to a V8, at the expense of a bunch more complexity, and lowering the RPM, though not as much as with a v6 with huge parts inside. (5l v6 vs 5l v8)
You can overcome part of this by stuff like VTEC. Lets you spin the motor real fast, and still make power just like down low. Works great on a small engined car, but when you get to something like a big v8, it takes much more drastic differences to matter, and the complexity. Major cost and maintainence differences. Plus we are talking about MAJOR increases in the forces at work, making design that much more difficult.
A turbo lets you add a small weight item to an otherwise unremarkable engine, and get those high power levels that you want, without sacrificing drivability. Now when you say "it shortens engine life" that is not 100% accurate. The turbo DOES NOT shorten the engines life. It increases the power output of the engine, THAT decreases its life. If you could pump out 280hp from the same 2.7 thats in the s4 without a turbo, you would have approx the same engine life.
I currently drive an rx7. Third gen. It has absolutely no turbo lag. Unless you drive an automatic. The reason for this is the car dosent make any power until you are at 2800-3000rpm. And it has a 7500rpm redline. The rotors (no pistons in it) move in such a way that they emulate a 2stroke engine, constant, strong power pulses. This gets those turbos spinning VERY quickly, at 1800rpm there is about a 10 second lag, because the engine makes NO power there. So you drive it at a higher rpm, where the power is. When you have the motor going at 3000 rpm and hit the throttle, the turbo is alreadly spun up. So by understanding the motor, and how it works, you are able to stay away from the lag. On the track you stay above 5krpm because at that point the second turbo as kicked in and you have access to all of the engines hp.
The s4 is not a true sports car, and is tuned for lower end HP/Torque. At 1800rpm the car flows MUCH less air then the rx7. Therefor the turbos cant be hit with an extreamly hard blast of air, even though thats where the engine makes its power. When the boost does come up, the power of course comes up exponentially. And quickly due to the turbo size. But it still does take a brief amount of time. The only way around it is to get the rpms up, so there is more airflow, and the turbos can keep spinning. But since this isnt a true sports car, its not that likely that you will be driving it like one. I will be keeping the RPMS up when I need power ;>
You could also remove the catalytic converters, this would allow the air to flow easier, letting the turbos spin with that much less restriction. This would, unlike a NA car, probably increase the low end torque slightly. Depending on how much backpressure was removed of course.
A supercharger is different though. While people think a supercharger has more torque then a turbo, its absolutely positively not true. It saps power from the engine, and makes a small amount of boost. It is linear, so you eliminate the big rush of a turbo. With the turbo, as long as I can get it spinning, I will have more power available, both low and high, then a supercharger both because of its non parasitic operation, and due to its ability to produce more boost then a supercharger. You pay for that with lag.
A supercharged m3 can make around 300rwhp. Damn amazing car at that power too. Its light, and goes VERY fast. A turbo M3 makes about 350rwhp.
Figure about 6000 dollars for either of those mods. All a chip does is make it so the car is not passing federal emmissions laws, but still pass state. Improves drivability. (the supercharger and turbo also require chips, and they do much more, but I was talking about the car in NA mode)
An S4 (euro spec) can make 340 (I have no in my face proof of this yet) all wheel hp. With a single chip. (well not really, its actually a few chips ;> But hell you get the idea)
Put the same 6000 dollars in the s4, and you could easily have 400hp, which would still lead you to have a less expensive, and more usable car then the m3. Much more like the m5 IMO, but with neater stuff inside.
If the dyno chart was exactly the same, I would most definitely choose the non turbo. As long as they were the same weight. Unfortunately this will not be the case.
Hypothetical situations rarely happen in real life, but... Here is what I belive. The rush everyone talks about could be there in a normally aspirated big engined car, but you pay a price. To get to those power levels, while remaining streetable, you need to increase the weight of the engine dramatically (big block v6) unfortunately the engine peices would be extreamly heavy. Which would limit your RPM along with not having terribly good flow. So they switch to a V8, at the expense of a bunch more complexity, and lowering the RPM, though not as much as with a v6 with huge parts inside. (5l v6 vs 5l v8)
You can overcome part of this by stuff like VTEC. Lets you spin the motor real fast, and still make power just like down low. Works great on a small engined car, but when you get to something like a big v8, it takes much more drastic differences to matter, and the complexity. Major cost and maintainence differences. Plus we are talking about MAJOR increases in the forces at work, making design that much more difficult.
A turbo lets you add a small weight item to an otherwise unremarkable engine, and get those high power levels that you want, without sacrificing drivability. Now when you say "it shortens engine life" that is not 100% accurate. The turbo DOES NOT shorten the engines life. It increases the power output of the engine, THAT decreases its life. If you could pump out 280hp from the same 2.7 thats in the s4 without a turbo, you would have approx the same engine life.
I currently drive an rx7. Third gen. It has absolutely no turbo lag. Unless you drive an automatic. The reason for this is the car dosent make any power until you are at 2800-3000rpm. And it has a 7500rpm redline. The rotors (no pistons in it) move in such a way that they emulate a 2stroke engine, constant, strong power pulses. This gets those turbos spinning VERY quickly, at 1800rpm there is about a 10 second lag, because the engine makes NO power there. So you drive it at a higher rpm, where the power is. When you have the motor going at 3000 rpm and hit the throttle, the turbo is alreadly spun up. So by understanding the motor, and how it works, you are able to stay away from the lag. On the track you stay above 5krpm because at that point the second turbo as kicked in and you have access to all of the engines hp.
The s4 is not a true sports car, and is tuned for lower end HP/Torque. At 1800rpm the car flows MUCH less air then the rx7. Therefor the turbos cant be hit with an extreamly hard blast of air, even though thats where the engine makes its power. When the boost does come up, the power of course comes up exponentially. And quickly due to the turbo size. But it still does take a brief amount of time. The only way around it is to get the rpms up, so there is more airflow, and the turbos can keep spinning. But since this isnt a true sports car, its not that likely that you will be driving it like one. I will be keeping the RPMS up when I need power ;>
You could also remove the catalytic converters, this would allow the air to flow easier, letting the turbos spin with that much less restriction. This would, unlike a NA car, probably increase the low end torque slightly. Depending on how much backpressure was removed of course.
A supercharger is different though. While people think a supercharger has more torque then a turbo, its absolutely positively not true. It saps power from the engine, and makes a small amount of boost. It is linear, so you eliminate the big rush of a turbo. With the turbo, as long as I can get it spinning, I will have more power available, both low and high, then a supercharger both because of its non parasitic operation, and due to its ability to produce more boost then a supercharger. You pay for that with lag.
A supercharged m3 can make around 300rwhp. Damn amazing car at that power too. Its light, and goes VERY fast. A turbo M3 makes about 350rwhp.
Figure about 6000 dollars for either of those mods. All a chip does is make it so the car is not passing federal emmissions laws, but still pass state. Improves drivability. (the supercharger and turbo also require chips, and they do much more, but I was talking about the car in NA mode)
An S4 (euro spec) can make 340 (I have no in my face proof of this yet) all wheel hp. With a single chip. (well not really, its actually a few chips ;> But hell you get the idea)
Put the same 6000 dollars in the s4, and you could easily have 400hp, which would still lead you to have a less expensive, and more usable car then the m3. Much more like the m5 IMO, but with neater stuff inside.
09-22-1999, 05:37 AM
#9
Guest
Posts: n/a
M3 vs. S6 vs. S4?
First off, I don't care about Audi vs. BMW. They're both great manufacturers. Whichever makes the better model in the category in which I'm buying is the better for me at that time.
Here's my experience:
My '95 S6 had good acceleration when the turbo was spooled and at full boost. If not, the S6 was otherwise disappointing while cruising at relatively low-rpm and then trying to punch it without down-shifting to get into the powerband. Steering was way over-boosted and brakes were merely adequate. The car was just too large and heavy to be considered quick or agile for spirited driving, although it was a great highway vehicle.
Sold the S6 after a year and bought a '97 M3 with the 3.2l engine, which is a very different animal compared with the 3.0l engine in the '95 M3. S6 didn't even compare! The M3 was twice the car, performance-wise. Much more low-end torque at any engine or vehicle speed. No need to shift. Just press down on the pedal and you're soon flying. And of course, the M3's handling, steering, and braking are legendary and well deserved.
Time for a new car. Have ordered an S4 and am awaiting delivery within the next month or so. Compared to the S6, the S4 has a lower curb weight, more power, and twin turbos, so that should address my concerns about throttle response and agility.
After reading the magazine reviews, I get the sense that the new S4 will essentially give me a more refined car with a higher level of fit, finish, and materials, and more standard features over the M3. But, it will not be quite up to the current M3 in terms of overall performance. Am I spoiled and am I going to miss the M3's instantaneous torque and rush?
Any comments or thoughts?
Here's my experience:
My '95 S6 had good acceleration when the turbo was spooled and at full boost. If not, the S6 was otherwise disappointing while cruising at relatively low-rpm and then trying to punch it without down-shifting to get into the powerband. Steering was way over-boosted and brakes were merely adequate. The car was just too large and heavy to be considered quick or agile for spirited driving, although it was a great highway vehicle.
Sold the S6 after a year and bought a '97 M3 with the 3.2l engine, which is a very different animal compared with the 3.0l engine in the '95 M3. S6 didn't even compare! The M3 was twice the car, performance-wise. Much more low-end torque at any engine or vehicle speed. No need to shift. Just press down on the pedal and you're soon flying. And of course, the M3's handling, steering, and braking are legendary and well deserved.
Time for a new car. Have ordered an S4 and am awaiting delivery within the next month or so. Compared to the S6, the S4 has a lower curb weight, more power, and twin turbos, so that should address my concerns about throttle response and agility.
After reading the magazine reviews, I get the sense that the new S4 will essentially give me a more refined car with a higher level of fit, finish, and materials, and more standard features over the M3. But, it will not be quite up to the current M3 in terms of overall performance. Am I spoiled and am I going to miss the M3's instantaneous torque and rush?
Any comments or thoughts?
09-22-1999, 05:48 AM
#10
Guest
Posts: n/a
Ditto on the Tip - Lag facts
Thats why I have a Tip car ordered. Loss of initial acceleration from a dead stop but once underway.... Also, clutch would take too much abuse, are you going to be able to keep from doing those hole shots? Not me! So Tip for me to preserve the drivetrain and you get more hi tech equip to chip. Anxious to see the rolling start/passing/30-50 & 50-70 mph comparison figures.