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      09-07-2007, 03:42 AM   #23
Maximus Decimus
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Quote:
Originally Posted by Harold View Post
Guys, please treat your fellow members in a respectful manner. The question damian is asking is on the face of it completely innocuous and a legitimate question.
Thk u.
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      09-07-2007, 08:28 AM   #24
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Quote:
Originally Posted by Harold View Post
Although I do have to say that the torque curve for the n54 engine is very impressive.
Yes, that graph looks VERY impressive. However, it is not really accurate in most any real-world situations. It is created on a dyno where the resistance of the rollers is carefully controlled.

On a real road, it will not look like that in first gear (car will not stay in low revs long enough to build boost to create a torque curve like that). That torque curve would be VERY hard to replicate. Would probably need to be going up a steep hill in a high gear (only way to put the engine under enough load where it stays at low revs long enough to build maximum boost)...

Of course driving up a steep hill at low speed in 5th gear, for example, will produce terrible acceleration, but it will make the torque curve start very early.

It's just a way to manipulate the specs to make them seem more impressive than they really are.

Porsche produces similar graphs for its 911 Turbo. Looks great on paper - not very accurate when driving it (power doesn't come on until revs are much higher than what Porsche claims for the begining of the torque plateau)...
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      09-07-2007, 10:17 AM   #25
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Quote:
Originally Posted by grant View Post
Yes, that graph looks VERY impressive. However, it is not really accurate in most any real-world situations. It is created on a dyno where the resistance of the rollers is carefully controlled.

On a real road, it will not look like that in first gear (car will not stay in low revs long enough to build boost to create a torque curve like that). That torque curve would be VERY hard to replicate. Would probably need to be going up a steep hill in a high gear (only way to put the engine under enough load where it stays at low revs long enough to build maximum boost)...

Of course driving up a steep hill at low speed in 5th gear, for example, will produce terrible acceleration, but it will make the torque curve start very early.

It's just a way to manipulate the specs to make them seem more impressive than they really are.

Porsche produces similar graphs for its 911 Turbo. Looks great on paper - not very accurate when driving it (power doesn't come on until revs are much higher than what Porsche claims for the begining of the torque plateau)...
I know exactly what you are talking about because it is the exact same thing with my MINI. I think BMW claim that the engine produces peak torque of 177 lb.ft. at 1700 rpm (actually, 192 lb.ft. on overboost at the same rpm range). Like you said, if you expect to roast the tires at the lights every time you set off because of all that torque so low down, rest assured that is certainly not the case (although, it certainly can happen if you get a lead foot on the throttle). With a little more than 1600 miles under my belt with the MINI, I can say that under normal driving, the engine doesnt get to peak torque til about 2800 rpm. I would imagine the 135i to be similar. As grant said, you just dont generate any boost in normal conditions by revving the car in neutral and then dropping the clutch. That is the main reason why no matter how hard manufacturers try to eliminate turbo lag, it will still exist in these situations because the turbos need that load to generate their power.
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      09-07-2007, 10:20 AM   #26
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Get the automatic if you're that concerned with it, it rev matches perfectly for you.
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      09-07-2007, 10:53 AM   #27
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Quote:
Originally Posted by Nixon View Post
I heel/toe the gas and brake at the same time while slipping the clutch right before launch. It works like this: I level the gas to get the RPM to around 3500 RPM with the clutch all the way to the floor and the brake firmly applied. Then I start letting out the clutch until the RPM's start to drop to around 2800 RPM while easing on a bit more gas. When I hit about 2800 RPM, I swivel off the brake and floor the gas while letting the clutch all the way out at the same time.

This is all done in one quick motion over about 1-2 seconds. I don't hold the clutch at 2800 RPM for any time at all, I just go straight to launch the moment the engine starts really pushing hard against the brakes.
This is similar to what I ended up concluding was the best way to take off in the STi. It's not so much as "struggling to learn," as someone above put it, as it is being a perfectionist and trying to find the ideal dynamic. I know no one has driven one yet, but i figured I'd prompt some speculation/discussion, which I'm happy to see finally happened.
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      09-07-2007, 11:18 AM   #28
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Quote:
Originally Posted by Madjack View Post
Why do people want to drag race cars that are not designed for this purpose. Buy a Cobra or the new Comaro if you want to drag race. The 135i is more of a track/drivers car.
Well, I intend to use the 135i for Solo2 racing. Even though that is more about handling than acceleration, launch technique is important.
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      09-07-2007, 11:26 AM   #29
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That's what I figured was going on - you gotta launch well in Solo 2 since the distance between the flagman and the trap is so short.
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      09-07-2007, 11:49 AM   #30
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Quote:
Originally Posted by damian View Post
This is similar to what I ended up concluding was the best way to take off in the STi. It's not so much as "struggling to learn," as someone above put it, as it is being a perfectionist and trying to find the ideal dynamic.
Yep, I'm the same way. There is a big difference between just getting the car going by letting out the clutch, and really nailing a good launch. In a way it is like using a hammer. Some folks would say, "hey, it's a hammer, how dumb are you that you have to ask how to use a hammer?"

Then they go to a construction site and see some old framer sinking big framing nails all the way in with two strikes of the hammer, and ask "how does he do that?" It's still a stupid hammer, but the results can be very different depending upon how it is used.
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      09-07-2007, 12:06 PM   #31
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...except that people have been using hammers for hundreds of years and nobody has ever driven a 135i coupe.
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      09-07-2007, 03:38 PM   #32
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Quote:
Originally Posted by bradford View Post
...except that people have been using hammers for hundreds of years and nobody has ever driven a 135i coupe.

What about Chucky? He's driven it, maybe he will log onto the board and share his launch secrets. It could happen...

On second thought, this board might have burned their bridges with this guy with all the Chucky stuff, so that's not too likely?

.<photoshop credit back to bryan@mworks>.
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      09-07-2007, 06:01 PM   #33
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All you need to build boost from a start is a stutter box. My friend has one installed on his Talon. Check out the video about 5 seconds in. The RPM bounces like crazy building the boost. He usually launches around 21PSI or so. http://www.jhracing.net/files/9.5_150_InCar_crop.mov
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      09-07-2007, 06:11 PM   #34
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Murdoc - is that an 8 second car?
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      09-07-2007, 06:21 PM   #35
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Quote:
Originally Posted by atr_hugo View Post
Murdoc - is that an 8 second car?
Not quite, 9.5 @150MPH. It's for sale if you're interested. http://www.jhracing.net/
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      09-07-2007, 06:25 PM   #36
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Ah so that explains the title of the vid! Isn't 150 mph the line where a 'chute's required?

It is a nice car but if I get a drag car it'll be one of these:
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      09-08-2007, 12:24 AM   #37
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^ +eleventy billion ..or chevelle ss
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      09-08-2007, 01:18 AM   #38
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In my procede 335i AT my best ET's were 12.63 and 12.66 Procede V1.4. My sixty foot times were 1.9's. IN the AT all you do is Push the DTC button Once (yes, this has already proven to be the best method for all 335i's) and brake torque to about 2k rpm. While I'm brake torquing I releast the brake as the RPM's are climbing so that it's completely released at the tach hits 2k.

With the MT's, because there's 250wtq at 2500 rpm's stock, just feather the clutch at about 2500 rpm and modulate the throttle until you can completely floor it. Only very good MT drivers have broke 2.0 60ft times so far.
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      09-08-2007, 06:17 PM   #39
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Quote:
Originally Posted by atr_hugo View Post
Ah so that explains the title of the vid! Isn't 150 mph the line where a 'chute's required?

Yep it is required at that speed, and he has them installed on the back hatch. You should see the looks he gets from people on the road as he is driving it to the drag strip. :eyebulge: It's completely street legal. It has working lights, wipers, horn, etc.
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      09-09-2007, 01:17 PM   #40
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Quote:
Originally Posted by murdoc158 View Post
All you need to build boost from a start is a stutter box. My friend has one installed on his Talon. Check out the video about 5 seconds in. The RPM bounces like crazy building the boost. He usually launches around 21PSI or so. http://www.jhracing.net/files/9.5_150_InCar_crop.mov
I guess that's my point about the 135i. The stutterbox is great for a turbo AWD. But I don't think a stutterbox will help us lauch a turbo 135i.

It sounds like putting a stutterbox in a 135i would get the load up to spool up the turbos, but then what would we do in a 135i? Dump the clutch like in an AWD car? Feather the clutch out while the engine is bouncing wildly between 4-6 thousand rpm?

I don't see a real lauch technique for getting load up and allowing for a smooth clutch release without just burning off one rear tire. I'm still looking for that theoretical launch technique that will get the turbo boost up, but still allow a smooth power transfer to the back tire with traction.

Gotta be ready for those demo days...
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      09-09-2007, 01:36 PM   #41
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Quote:
Originally Posted by 335ito135i View Post
In my procede 335i AT my best ET's were 12.63 and 12.66 Procede V1.4. My sixty foot times were 1.9's. IN the AT all you do is Push the DTC button Once (yes, this has already proven to be the best method for all 335i's) and brake torque to about 2k rpm. While I'm brake torquing I releast the brake as the RPM's are climbing so that it's completely released at the tach hits 2k.

With the MT's, because there's 250wtq at 2500 rpm's stock, just feather the clutch at about 2500 rpm and modulate the throttle until you can completely floor it. Only very good MT drivers have broke 2.0 60ft times so far.
Yea, I have to say it sounds like all the MT 335i drivers are still trying to launch it like it is a NA engine instead of a turbo engine. I mentioned that same launch technique for an NA 535i 6-cyl MT in an earlier post. There is no way to get the boost pressure up using that technique. I wonder if this is the reason why 335i MT's are launching so much slower than the AT's? I mentioned earlier that the 335i MT guys don't seem to be the best source of information on getting a really solid launch since they are having such a hard time. Your numbers show that.

From what I've read, the Procede MT's don't see any improvement over stock in sixty-foot times despite the increased theoretical higher turbo boost. It makes me wonder if the problem is that the turbo is never able to attain full boost using the traditional NA engine launch technique. The engine is the same between both the AT and the MT, so I suspect the launch technique for the MT's isn't getting the turbos spooled up, which would put the MT's down on power compared to the AT's right from the start.

I think they need a way to get the boost up prior to launch, while still not burning off the rear tire or the clutch. I'm guessing we will see the same issue for the 135i's.
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      09-10-2007, 08:35 AM   #42
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Quote:
Originally Posted by Klinn View Post
Well, I intend to use the 135i for Solo2 racing. Even though that is more about handling than acceleration, launch technique is important.
But, if you are doing clutch dumps, you are losing time because of wheel spin. You need to learn how to feather out the clutch as you accelerate. No one knows how to do this yet because we do not have the car.

Also, to those that responded you want to do spirited driving. Well, I drove my STi spiritedly at times and did not need to launch it. There is no reason th launch the car on the street.
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      09-10-2007, 08:40 AM   #43
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Quote:
Originally Posted by Madjack View Post
No one knows how to do this yet because we do not have the car.
Such could be said about 99% of the threads on this forum. Who cares, though? Some people like to speculate, about the radio, handling, tires, pricing, colors, etc.

Quote:
Also, to those that responded you want to do spirited driving. Well, I drove my STi spiritedly at times and did not need to launch it. There is no reason th launch the car on the street.
There is also no "need" or "reason" for spirited driving. Whatever floats your boat. Some people like taking off fast sometimes, others like driving aggressively on twisty roads. Guess which one is safer.
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      09-10-2007, 08:49 AM   #44
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Such could be said Guess which one is safer.

None!!! Too bad I like them both!!
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