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+--- Thread: Which power adder: (/showthread.php?tid=245)
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- .RJ - 03-18-2004
Evan Wrote:What car would you use to drive to hawaii? Never mind that its impossible, just answer the question!!!!!
The cubans do it better
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- Kaan - 03-18-2004
supercharger... well cause it i want boost-able power in my car for the track... a turbo would create too much heat for my little engine bay. but really i like the all motor side of motor tuning... its more race legal...
- .RJ - 03-18-2004
Kaan Wrote:a turbo would create too much heat for my little engine bay.
You dont want to know what intake charge temps Don was seeing at summit 2 weeks ago (supercharged GSR hatch).
- ScottyB - 03-19-2004
.RJ Wrote:Kaan Wrote:a turbo would create too much heat for my little engine bay.
You dont want to know what intake charge temps Don was seeing at summit 2 weeks ago (supercharged GSR hatch).
and that's in what, 40 degree weather? eek.
- Dave - 03-19-2004
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).
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...
- ScottyB - 03-19-2004
Dave Wrote: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).
thats pretty much the same setup and rationale as the older bi-turbo S4. it uses rather tiny KKK K04 turbos, one per each bank of it's V6. they spool up almost fully by about 2000 rpm. Most audi customers expect a smooth powerband, which is why audi chose such a small turbo for the quick spool-up.
- KPWSerpiente - 03-19-2004
Quote: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.
I'm sorry, but a true sequential setup features one smaller turbo and one larger one. That is really the only true benefit to a twin setup...it provides good low rpm response with a high top end. As you say a twin set up with the same size turbos is a compromise and won't provide both.
http://auto.howstuffworks.com/turbo6.htm
If you can't believe me, trust howstuffworks.com.
Quote: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)
I'm not an expert on sequential setups but I sincerely doubt this is a difficult thing to work around. If the wastegate on the first turbo dumped into the turbine of the second, this would solve your problem. Or if that isn't going to produce enough exhaust gas, how about an external gate on each runner dumping into the second turbo? I think the reason you don't see true sequential set ups is because they are expensive and require a lot of room in the engine bay, and because most people will either get by with a well selected single turbo. They're simply not practical.
What I was saying about engine size is that to power two decent size turbos, you need a larger engine. 2.0 liters is not going to cut it.
I'm pretty sure every car you mentioned is 3.0 liters or larger but I don't know about those Jags, I'm just guessing.
Interestingly enough, I got to thinking and the GTR is an exception to the rule.
-T
- Dave - 03-19-2004
KPWSerpiente Wrote:I'm sorry, but a true sequential setup features one smaller turbo and one larger one. That is really the only true benefit to a twin setup...it provides good low rpm response with a high top end.
Could you please give me an example of a true sequential twin turbo? A twin setup does have some major advantages over a single, BTW. If it didn't, why would companies have blown as much money as they did going to TT setups? Because it gives less lag time and still gives the car a strong top end, albeit limited in comparison to a single larger turbo. I have never seen one of these "true sequential twin turbo systems" in real life and would love to do some more research on it. Alas, I'm too lazy to sift through all of the shit out on the internet. Know of any off the top of your head?
- Dave - 03-19-2004
yes, I know about Howstuffworks.com and have visited on many occaisions. However, I have never seen proof of an engine that had two differently sized turbos, and certainly not from the factory. Like I said, it is a common belief, but for the most part it is wrong. It IS possible that an internet source can be wrong too (you'll learn this too as you do more research projects), so until I see some valid proof, I'll stand by my previous statement.
The key to have having a strong top end as well as limited spool time IS having a well selected turbo. You give up on one to get the other, plain and simple. Each person veiws this compromise differently. The practicality of a twin turbo system is thus determined by the driver and his aspirations. For many, a single will accomplish more than a twin for them, but I will remain twin when I convert my IV into its rightful place, and if I kept my III, it would also remained a twin turbo.
As I said before, I'm not all knowing, but I do think I have a fair amount of knowledge dealing with twin turbo setups and I know that the vast majority are inline, as opposed to sequential, and what few sequentials that I know of are both of the same size.
- Mike - 03-19-2004
All this turbo talk... What you guys really need is VTEC.
- KPWSerpiente - 03-19-2004
Havn't seen much evidence for one yet Dave. Maybe I will have to build the first true sequential because the idea is sound.
As for Vtec...I heard something along the lines of "waiting for bad sex?"
-T
- .RJ - 03-19-2004
KPWSerpiente Wrote:As for Vtec...
Flat torque curve?
- Maengelito - 03-20-2004
MichaelJComputer Wrote:All this turbo talk... What you guys really need is VTEC.
or more cowbell
- .RJ - 03-20-2004
lol
- Kaan - 03-22-2004
my vtak is going to be 3 faster 3 furiester... when i'm done with it hahahahaha
- Mike - 03-22-2004
Kaan Wrote:my vtak is going to be 3 faster 3 furiester... when i'm done with it hahahahaha
Been hearing that for years...
- Kaan - 03-22-2004
only for a couple ;-) when you only have a bottom end it makes life harder
- Maengelito - 03-22-2004
Kaan Wrote:only for a couple ;-) when you only have a bottom end [of evan's mom] it makes [my piece] harder
- Kaan - 03-22-2004
God i love MM humor!