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  1. #1
    White Knuckles Ride PeterD's Avatar
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    Wink HQ 396 Coupe - High Country Targa 2012

    Welcome back to those who are interested in the development and completion of the ‘HQ 396 Coupe’ team. This year will be a bit lean as the budget is dedicated to improving the car from last year’s event plus a few hilclimbs and track days for testing. The big event being the Targa High Country on 9 – 11 Nov 2012.



    The short list of improvements are:
    • 3.7 Gears (from 3.25) – waiting to be fitted
    • New fuel tank from Brown Davis - ready to pick up
    • Oil cooler
    • New leads – booked for next week
    • Harrop custom made two piece front discs – under design now
    • 3” exhaust as the 96db stated limit was completely ignored
    • Rear 16mm K-mac sway bar and perhaps lighter springs
    • Raise front 10 – 15 mm
    • New driveshaft with HD rear uni
    • Sump guard
    We realise that a lot of things have to go your way to do well in an endurance event such as the THC be we have what I think is a realistic goal of a top 10 place in Classic overall. It is one thing to build a car to finish and quite another to build a car, prepare and drive for a top 10 finish.

    The current racing calendar is:
    • 25 Feb - VIC Hillclimb – Broadford.
    • Winton either VSSC or HSCCV.
    • Sandown either VSSC or HSCCV.
    • Another event close to the THC as prep, maybe the Aus Hillclimb Champs at Mt Panorama depending on the dates.
    • 9 – 11 Nov – Targa High Country – Mansfield VIC.
    Logistically we will take the Cup week off and review the notes closer to the event but it will all depend on the dates for the Aus Hillclimb Champs.

    I have also been working through 'Ultimate Speed Secrets' by Ross Bentley (thanks Marty).

    We will carry a few more spares this time and fit a tool box and spares in the boot.

    The plan is to have the diff gears in, leads fitted and tank in for Broadford. TonyD will also have a drive and we can make some decisions on where we are going with the back end. If time and $ permit I may try the Hawk HP Plus pads on the front for ‘cold’ hillclimb use. The Ferodo 2500’s don’t have enough bite to balance out the bias. The Hawk HP Plus’s claim “Extremely high friction output”.

    Last years thread Holden HQ Coupe 396 Development and Competition 2011
    Last edited by PeterD; 01-01-2012 at 04:10 PM.
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  2. #2
    casual poster monaro maniac's Avatar
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    Looking forward to another year of developments and improvements Pete, you always give a great read and I love following your fantastic car.

    Cheers, Jason

  3. #3
    casual poster davad73's Avatar
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    As above, looking forward to the year ahead.

  4. #4
    White Knuckles Ride PeterD's Avatar
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    Thanks guys, always good to get encouraging comments.

    Got a bit bored today, too hot to do anything so pulled the front shocks off to make a rebound adjustment. I remember when we fitted the shocks it was a bit unstable in the front (steering box play) and we gave it a bit more rebound to settle it down over the high speed bumps.

    New steering box now fitted so I thought it would help with the weight transfer under power to back off the rebound in the front. I have taken it from 85% down to 55% on the Koni's (one turn out from 1/4). With the raised front it should help generate and hold traction. It's not a big change admittedly but I'm sure a move in the right direction.

    TonyD and I had a good look at the diff geometry recently and it's looking too hard to make wholesale alterations such as a watts linkage or moving the arms etc. We may have to settle for a sway bar and perhaps adjustable top arms or even rose jointed top arms if that would work???

    Hopefully with a few tweaks here and there plus some changes in driving style we can dial out her bad habits
    Last edited by PeterD; 02-01-2012 at 07:01 PM.
    Pedders Frankston - Simon http://www.pedders.com.au/
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  5. #5
    'beep' beeb's Avatar
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    Adjustable top arms are available from MacDonald Bros. You'll want to repaint them if you buy a set, but they firmed up the rear end on my wagon heaps. (Surprised the hell out of me to be honest, it was an implausibly large improvement...)

  6. #6
    White Knuckles Ride PeterD's Avatar
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    Thanks beeb, did you adjust/correct the pinion to gb output shaft angle and if so how is it done?

    Second question, have you heard of anyone running rose joint upper arms, would they work?

    What I'm actually looking for is more supple movement of the upper arms without introducing unintended charistics. My theory is that the diff is binding and not allowing that last bit of movement in full cornering. Result is tail out 'style' and sideways diff hopping right at the limit.
    Last edited by PeterD; 03-01-2012 at 02:39 PM.
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  7. #7
    White Knuckles Ride PeterD's Avatar
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    Red face MSD Leads

    As you can see Stephen from Gas Lead Technology custom fitted my leads yesterday. The leads are now the correct lengths and are routed away from heat and other parts. Being the correct lengths they now don't wobble around nor are they too tight. The resistance of the MSD 8.5mm leads is a small fraction of what my old 'off the shelf' Autobarn leads. I'm surprised that I persisted with these old leads for so long. Stephen used some very nice positive lock plug connectors and high quality caps etc.

    If you want a set of leads I can recommend Gas Lead Technology (in Melbourne) - 0414 367 304 Stephen.

    Pedders Frankston - Simon http://www.pedders.com.au/
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  8. #8
    'beep' beeb's Avatar
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    Quote Originally Posted by PeterD View Post
    Thanks beeb, did you adjust/correct the pinion to gb output shaft angle and if so how is it done?

    Second question, have you heard of anyone running rose joint upper arms, would they work?

    What I'm actually looking for is more supple movement of the upper arms without introducing unintended charistics. My theory is that the diff is binding and not allowing that last bit of movement in full cornering. Result is tail out 'style' and sideways diff hopping right at the limit.
    Srry mate, they adjusted them on installation (well, claimed they did, and it certainly handled and stayed stable better), I wasn't DIY at the time, so no idea of any specs I'm afraid. I had replaced the bushes in the standard arms before I put the adjustables in, and it was still a big improvement. I think that's why it surprised me so much.

    And no, I haven't heard of anyone running rose-joint or metal-bushed uppers. I suspect they would be far to unforgiving and quite probably punch arms through the floor if you hit a pothole or big bump in the road. Other than that, the driveline vibrations you would suddenly cop through the floor would be immense, which could also lead to cracking over the long-term life of the vehicle.

  9. #9
    casual poster 355l34's Avatar
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    Thanks beeb, did you adjust/correct the pinion to gb output shaft angle and if so how is it done?

    hi pete, all the best for the new year, im looking forward to following this.

    for the pinion angle buy yourself a protractor{around $45 from hardware store}. with the car level and the suspension loaded take a measurement of the tailshaft then disconnect it and place something like a tube socket accross/between the cups of the diff yoke in the vertical position and take a reading off that, subtract 90 degrees and the difference is your pinion angle. for urethane bushes aim for around -2.5-3 degree as a starting point.
    if you cant follow that then just google it, there are a billion people that can explain **** better than me.

  10. #10
    White Knuckles Ride PeterD's Avatar
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    Thanks guys I was thinking more of a dynamic measurement rather than the static.



    I always seem to have a vibration around 200k no matter how well I have it balanced. I thought I may have one of the lower two conditions but it would require measuring the actual pinion angle in comparison to the gearbox output shaft. Not so easy I think ... may be best to give it to a professional because I can only test it at over 180k which means a track day.
    Last edited by PeterD; 07-01-2012 at 01:58 PM.
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  11. #11
    White Knuckles Ride PeterD's Avatar
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    Question Rear Roll Centre Calculation

    For an HQ style rear end.



    Corrected, for those paying attention.
    Last edited by PeterD; 14-01-2012 at 05:58 PM.
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  12. #12
    White Knuckles Ride PeterD's Avatar
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    Thumbs up Roll Centre Calculations

    After reading through ‘How to make your car handle’ (thanks Smitty) TonyD and I spent most of the day yesterday measuring up the car. A quick measure up of the front confirmed that the front geometry and steering is spot on!

    We followed the above diagram and measuring method and after a few errors and using the wrong formula … we got an answer. BTW the lower trailing arms on an HQ narrow to the front of the car and are NOT parallel. This means a different calculation method must be used. I don’t think anyone would be surprised to know that the rear roll centre is 18”. I’m told that the optimal roll centre is about 8” as the HQ has a heavy roof and upper car. So the options are:

    1. Raise the rear to about std HQ height.
    2. Top arms – Raise the front or lower the rear or both.
    3. Bottom arms – Lower the front or raise the rear or both or all four.
    4. Do something else to mitigate the high roll centre, CG and resulting weight transfer.

    Option one is out as the rake would be too high in relation to the front of the car to have enough effect. It would also have other undesirable effects.

    Option three is not such a good idea for two reasons. Firstly that lower arms have a very slight ‘down to the front’ attitude but are basically parallel to the ground. That’s about where you want the lower arms and although adjustments here would be much easier the problem can better be fixed in the top arms. Secondly the lower arms are twice as long as the upper arms so any effective adjustment would need to be twice as much as the top arms.

    We will consider option four after option two has been exhausted possibly as too difficult. There are a number of problems in working with the top arms … Lowering the diff end has minimal effect as a 9” leaves about 8 – 10 mm room for lowering at most. Also the body end would need to be raised further than is room in the recess therefore requiring a modification to the floor and sub frame where the rear seat goes. I don’t believe that the arms could be shortened as this would negatively impact the upper radius of the diff as the suspension compresses.

    If we did go for the upper arm option it would require removal of the diff, exhaust etc and cutting the floor and sub frame cross member to allow the arm to be raised = a lot of work!

    The adjustments needed to lower the roll centre to its optimum position are in the cm’s range not mm’s
    Last edited by PeterD; 15-01-2012 at 01:43 PM.
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  13. #13
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    Hi Peter,

    Its interesting to see the way the roll centre is calculated for the un-parallel 4 link in the HQ. Another option for changing the height of the roll centre might be to fit a panhard bar.On a parallel 4link with panhard, the roll centre height is the centre of the panhard, and i would believe this to be true if fitted to the unparallel 4link.
    What is it you are trying to achieve? I would think that by lowering your roll centre on the rear you will introduce a tighter condition and if taken too far might become under steer, which seems to be the opposite of what the explanation in the sketch is indicating. The way i under stand it the center of gravity rolls around the roll centre, so the higher the Cof G is in relation to the roll centre the more the car plants the outside tyre thus the tyre produces more grip on that end?

    Cheers, Al.

  14. #14
    White Knuckles Ride PeterD's Avatar
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    Thanks Al, the roll centre needs to drop from 18" to about 8". This can be done by adjusting the top arms, raise front and lower rear. Strangely the book says that increased weight transfer equals reduced grip. And the HQ suffers from a high Roll centre (when lowered) raised rear top arms when a 9" is fitted, compounding the problem. Has a high CG and guess what ... the 9" adds to the unsprung weight. These are the three factors influencing weight transfer and thus max cornering speed.

    I fitted brand new tyres for the Targa and at the finish the outside of both rears were heavily worn. Indicating too much weight transfer due to the three factors. There is not much I can do about the unsprung weight, or even the CG but I can drop the roll centre. Our rough calculations put a std HQ at about 10" so we are well above that due to the top arm angle.

    The ultimate goal is higher cornering speed. As it is I can steer it through a turn with the throttle so a tendency for understeer would be nice.
    Pedders Frankston - Simon http://www.pedders.com.au/
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  15. #15
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    It seems strange that the book sais increasing weight transfer reduces grip, as friction is a function of weight and area-more weight is more friction.
    If you have to much weight transfer now, lowering your roll centre will increase that, but that will increase your lateral grip in the rear, which is what you are looking for.

    The rear roll center of a car with Mustang's non-parallel four-link rear suspension can be found as follows:



    Find point A by drawing lines through the non-parallel upper links.
    Find point B by drawing lines through the non-parallel lower links.
    The roll center is the point where line A-B crosses a vertical plane through the axle centerline.


    If you were to add a panhard bar to the above rear suspension, point A would be at the point the panhard bar crosses the the centerline of the car when viewed from above. If you were to add a watts link, point A would be the pivot of the bellcrank. By adjusting their mounting points, either of these devices can be used to raise or lower the car's rear roll center height (RCH).

    In the info here, adding a panhard to the existing geometry will lower your point "A" in your above diagram to the centre of your diff housing if you set it up to cross there. this would also give a better lateral location for your diff and provide you with the lower roll centre you are looking for. This may also be easier to fit than mooving your control arms.

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