Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #1
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729

    Auto vs. manual throttle response/rev speed...

    OK, I've asked about the "sluggishness" of my ZHP throttle in another thread. To recap, what I'm referring to is sitting in the car at idle, stabbing the throttle throttle, and the response is slow to non-existant... I stab the throttle, and I can hear air in the throttle body, it sounds and feels like the ECU is tilling the engine to rev, and there's fuel and air, and the RPM's go up some - just not much. The best metaphor I can think of is that the engine is connected to a big, heavy flywheel... It's like mass/inertia is keeping the engine from revving.

    In that old thread, pretty much everybody unanimously agreed it was the crappy fly-by-wire throttle map/response, and that a Shark Injector, SprintBooster, or other tune with throttle remapping would correct the issue. I stored it away in my data bank and wrote it off for after I have my wheels and tires redone this spring. Important stuff first, then on to the really fun stuff.

    Fast forward to a couple of nights ago. I had to restart my wife's E83 X3 in the garage and shut it down, so I revved it up a little for fun. Wow! Not only is it night and day, but the X3 revs like a frickin' F1 car compared to my ZHP! I mean, the difference is incredible. Now, the X3 is an '07 LCI with the N52B30, so a totally different engine, and no doubt BMW improved the throttle response between '04 and '07. Still, should they be THAT different?

    So, I started thinking... The X3 is an automatic, so then I started wondering about flywheels. Because that's what it seems like... Like my ZHP has a 100-pound flywheel and the X3 has like a 50-pound flywheel. I know there's a big difference between stock and performance flywheels, and that one of the main benefits of a light-weight flywheel is throttle response and faster acceleration. I looked it up, and our stock dual-miss flywheel is 25 pounds, while a lightweight aluminum flywheel is only 10 pounds.

    So... Then I started wondering... Is there a big difference between flywheels on autos and sticks on our cars? Does anybody have significant seat time in both auto and 6MT ZHP to know if the throttle response is different between the two?

    Cheers,
    SC
    Last edited by ecrabb; 12-10-2015 at 03:07 PM.
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

  2. #2
    Join Date
    Mar 2011
    Location
    Philadelphia
    Posts
    1,079
    I noticed the same thing when driving my mom's E46 330xi compared to my ZHP back in the day. What I can tell you is that the auotmatics and manuals have the same software, so they use the same throttle curves (granted there may be some maps that are only used in auto mode and vice versa).

    Your instinct about the flywheel is correct. Since automatics have a torque converter, they don't have a flywheel in the traditional sense. They just have a flex plate that doesn't weigh much (< 10 lbs). Most manuals have flywheels around 25-30lbs. You can install a lighter weight flywheel and get some of that off-idle throttle response back, but then your clutch will engage much less smoothly. Also, remember that this really only applies when you're in neutral. When the cars are in motion, the drag that results from the torque converter and driveline will make the automatic more sluggish overall.

    With regards to the N52 specifically, even in manual guise, that thing will probably have more responsive throttle than the M54. Valvetronic allows for the valve lift to be controlled directly -- so there are even less pumping losses than an ITB-equipped car.

  3. #3
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729
    Thanks! Glad I wasn't totally out to lunch.

    Definitely want to do Shark Injector, and if I decide to keep this car long-term, I think an LSD and lighter flywheel would both be on the to-do list.

    Cheers,
    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

  4. #4
    Join Date
    Nov 2014
    Location
    Portland, OR
    Posts
    10,243
    I don't know much about lightweight flywheels, but I have heard that you may experience more clutch/gear chatter at idle. Just something to consider.

    Some info from UUC: http://www.uucmotorwerks.com/flywheel/gear_rattle.htm

  5. #5
    Join Date
    Jan 1970
    Location
    Branford, CT
    Posts
    16,055
    Quote Originally Posted by BMWCurves View Post
    I don't know much about lightweight flywheels, but I have heard that you may experience more clutch/gear chatter at idle. Just something to consider.

    Some info from UUC: http://www.uucmotorwerks.com/flywheel/gear_rattle.htm
    Yes. The chatter is usually very noticeable and is audible when the clutch pedal is not pressed and the transmission in neutral. Otherwise, you don't hear it when the pedal is pressed or if the car is moving in gear. I used to get people asking me "what's wrong with your car?" at stoplights, which was amusing at times.

    I absolutely loved the performance of my E30 with the lightweight flywheel. It revved VERY quickly, and made rev-matches a lot faster. It accelerated faster due to its eagerness to rev. If you don't mind the chatter, then this is an excellent performance upgrade.

    sent from my Droid Turbo
    BP
    2005 330i ZHP / 6MT
    Imolarot / Naturbraun
    2003 330iT / 6MT
    Orientblau / Naturbraun




    It's not the car you drive, it's how you drive it.

  6. #6
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729
    Yeah, I knew they chattered, but then my OE clutch chatters a little. How much worse on a 1-10 scale is it?

    Mine is certainly noticeable sitting in my driveway, though it probably wouldn't be sitting in traffic.

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

  7. #7
    Join Date
    Jan 1970
    Location
    Branford, CT
    Posts
    16,055
    Quote Originally Posted by ecrabb View Post
    Yeah, I knew they chattered, but then my OE clutch chatters a little. How much worse on a 1-10 scale is it?

    Mine is certainly noticeable sitting in my driveway, though it probably wouldn't be sitting in traffic.

    SC
    Where my ZHP chatters at a level of 1 (can't be heard from the outside but only from the inside - barely), my E30 chattered probably at about 5-7, depending on whether it was loud or quiet that day.

    sent from my Droid Turbo
    BP
    2005 330i ZHP / 6MT
    Imolarot / Naturbraun
    2003 330iT / 6MT
    Orientblau / Naturbraun




    It's not the car you drive, it's how you drive it.

  8. #8
    Join Date
    Feb 2014
    Location
    Indy
    Posts
    547
    Drive a 99 323i or 328i with cable-action throttle. Feels like freaking lightning in comparison to ZHP drive by wire thunder.

    BMW CCA # 510252

  9. #9
    Join Date
    Apr 2012
    Location
    Hereford, AZ
    Posts
    1,081
    Sharking my ZHP improved the throttle response A TON. It now feels like an old school non-drive-by-wire car. Sharking the M5 had an even more dramatic effect, as it employs euro fuel mapping, which is apparently a mess on the US-spec M5. Result is it's a ton easier to drive smoothly.

    I wholeheartedly recommend Sharking a ZHP.. not for alleged power gains, but for greatly improved drivability and responsiveness.

    '21 M2 Competition
    '08 Z4 M Coupé
    '19 Golf R

  10. #10
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729
    As always, great feedback, guys! Clearly, I just need to shut up and get the throttle remapped. Thanks!!!

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

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