03-19-2004, 01:02 AM
I personally like the turbo. Superchargers are cool because they are there through the entire power band. Nawwwz is definitely not my thing. Its kinda cool to hit a button and get power whenever you want it, but at thes ame time, I'd rather have something that gives me power all the time (when I want it), and doesn't require as much maintenance. Besides, nitrous isn't as easy to upgrade from what I understand. The turbo, on the other hand, is the sweetest shit in the world. The idea of making something go faster by using a byproduct of its speed (exhaust gas) is an absolutely ingenious idea if you ask me. Not only that, its so incredibly easy to upgrade and can be very reliable. The worst part of turbocharging, besides the lag (which can be remedied with a smaller or faster spooling turbo) is the fucking b00st rot that comes with it. THAT is the worst part (wallet constantly emptying, neverending desire to hear turbo spooling, etc).
A twin turbo setup is typically chosen for its reduced spool time, although this typically limits your top end. It is basically a compromise of top end (read: high HP) for spool time. The big HP supras all sport a ginormous single turbo, takes fuckin forever to spool up, but has a sickening pull once it does and absolutely flies.
Furthermore, fitting an TT engine with two different sized turbos is a common belief, but does not happen. All stock mkIV TT comes with a pair of CT12B turbos, both exactly the same, but the engine management system is what is responsible for putting it into a sequential mode. Thus, the 2nd turbo does not actually "come on" until after the 1st has been running, but it has already spooled up, so it feels like the car is pulling even harder. A very common modification is to put the car into "true twin" configuration; eliminating the sequential setup and allowing them both to spool at the same time. The same applies to the 2.5L 1JZ-GTE sporting a pair of CT12As and all turbo upgrades that keep twin turbos have them both staying the same size.
The reason for this is because in the example you give, one turbo is driven off the exhaust gases and boosting, while the second comes "on line" and spools up. It is assumed that the 1st is approaching its maximum boost as the 2nd comes on. This is a terrific thought, except that the exhaust gases are still passing through the 1st turbo when the 2nd is going through its power band. There is a hell of a lot more gas coming out of the car than before (big 2nd turbo sucks in lots more air than small 1st turbo), and thus the 1st turbo will end up getting cooked from overboosting.
The VR-4 has two extremely small turbos, but they spool so amazingly quick that it is almost as if the car is NA (ie: virtually no lag at all). Unfortunately, they reach maximum boost very quickly due to thier small size and end up leaving you hollow inside and only wanting more boost...
Quote:A twin turbo set up where both turbos are of equal size is usually only going to be found on a V engine displacing more than 3 liters. It isn't practical on a smaller inline or horizontally opposed 4 cylinder engine because there won't be enough exhaust gas to spool both turbos.Not quite, but you're thinking at least. I'll say up front, that I have extremely limited knowledge of V motors with twins. This includes the VR-4 and 300Z of the early 90s. Other than that, I know of very few other TT engines besides the Lotus esprit, Jaguar XJ220R (HOTNESS from Summit), RX-7, and the Supras. So, I'm going to have my input based solely on what experience I DO have. The TT supra engines are either 2, 2.5, or 3 liter engines, in all cases. There is a TT setup (aftermarket) for the 3L 7M-GTE from the mkIII era, and of course the fabled mkIV with its 3L. In japan, mkIII supras were also offered with a 2.0L (1G-GTE) and a 2.5L (1JZ-GTE, see my gallery). I have not driven a 7M-GTTE, and these are pretty much impossible to find. However, I have driven the others. Both have limited spooling times and incredible amounts of power available to them (1G sucks balls simply because it is a 2L engine hauling around a 3800 lb car).
They will not make as much power as a single large turbo, but they also wont' lag as much and that is very important in cars sold to the general publics.
A sequential turbu set up has two different sized turbos. One smaller one that spools up quick, and one larger one that creats more power and will literally take over when needed.
-T
A twin turbo setup is typically chosen for its reduced spool time, although this typically limits your top end. It is basically a compromise of top end (read: high HP) for spool time. The big HP supras all sport a ginormous single turbo, takes fuckin forever to spool up, but has a sickening pull once it does and absolutely flies.
Furthermore, fitting an TT engine with two different sized turbos is a common belief, but does not happen. All stock mkIV TT comes with a pair of CT12B turbos, both exactly the same, but the engine management system is what is responsible for putting it into a sequential mode. Thus, the 2nd turbo does not actually "come on" until after the 1st has been running, but it has already spooled up, so it feels like the car is pulling even harder. A very common modification is to put the car into "true twin" configuration; eliminating the sequential setup and allowing them both to spool at the same time. The same applies to the 2.5L 1JZ-GTE sporting a pair of CT12As and all turbo upgrades that keep twin turbos have them both staying the same size.
The reason for this is because in the example you give, one turbo is driven off the exhaust gases and boosting, while the second comes "on line" and spools up. It is assumed that the 1st is approaching its maximum boost as the 2nd comes on. This is a terrific thought, except that the exhaust gases are still passing through the 1st turbo when the 2nd is going through its power band. There is a hell of a lot more gas coming out of the car than before (big 2nd turbo sucks in lots more air than small 1st turbo), and thus the 1st turbo will end up getting cooked from overboosting.
The VR-4 has two extremely small turbos, but they spool so amazingly quick that it is almost as if the car is NA (ie: virtually no lag at all). Unfortunately, they reach maximum boost very quickly due to thier small size and end up leaving you hollow inside and only wanting more boost...