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Location:
Adelaide
Registered:
May 2003
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Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:34
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Alright, just thought i would see what experience others have had with driving extremely cammy cars. The 86 doesnt actually make much power under 4000rpm and is less inspiring than a 4ac on diesel down that low. Hitting 4000rpm it gets a whole whackload of power and pootles (technical term) off quite nicely. However, getting it there off a hard launch is proving difficult.
I guess the 3.7kg flywheel isnt helping matters a great deal, nor would the 3.9:1 ratio diff which is in there. Basically i can launch at 3000ish rpm and get some wheel spin off but then it bogs down into uninspiring tractor rubbish until it lets fly again at 4000rpm. If i launch at higher rpm i just lose traction for longer, and lower rpm it threatens to stall due to the light flywheel. Im loathed to balance the clutch as its not designed to take this amount of abuse.
Anyone got some ideas for me to get off the line?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:40
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how big are the cams?
how well is it tuned?
my poor little car only has 275/284 cams, with 65 deg overlap, but it will hold in idle of 600rpm now with EFI.. and this is without decent ignition tuning (or any!).
if you can booth off at 3000rpm, and it then bogs down, it sounds like a tuning problem perhaps. it should be uninspiring, but shouldn't bog a such...
maybe slip at 4000 
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:45
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Fix the tuning and give it at least a 4.3 diff
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Location:
Brisbane
Registered:
February 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:48
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maybe you need a filter/restrictor in the line feeding the map sensor? it might be seeing way to many low-vacuum events (at low rpm) oreven getting confused by excessive pulsing to get a decent map reading?
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Location:
Adelaide
Registered:
May 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:51
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The tuning is spot on, we just finished it on Monday. Needs a bit of a road tweak but other than that its good.
There is no MAP sensor, it is all TPS sensed.
Currently im thinking its as im going WOT at too low RPM to let it catch up. Ill have a fiddle when im driving it around for rego stuff tomorrow.
stewart: 308* cams quad throttles. Holds a 1100rpm idle quite easily (1100rpm as the coolant never warms up otherwise).
I guess "bog down" was a bit of a bad word. It comes off cam rather majorly, and is quite uninspiring.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:53
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on that, i was getting massive variation in MAP signal, ie 85-110kpa at WOT, just near where cam comes on. i put in a ryco carby fuel filter (Z15KS), 6mm in/outlets, and now my MAP is rock stable.. might vary by 1kpa, but no more...
highly recommended if you are using quads too (even tho mine is just a plenum with single TB)
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:55
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heh heh, alpha-N is not designed to be used at low rpm.. only in the power band of the motor.
since you effectively have 2D tuning between TPS and rpm, it kinda sucks...
did you try to tune on MAP? it can be done.. even if you only have 75-80kpa at idle.. (when mine drops off cam and idles at 600rpm, i have 90-95kpa, ie 5-10kpa vacuum)
308 are kinds big cams 
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Location:
Adelaide
Registered:
May 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 12:55
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Aye, i woudl take your advice, if i had a MAP sensor. It is still in its blister packaging from when i ordered it.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 13:18
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| takai wrote on Mon, 24 January 2005 23:55 |
Aye, i woudl take your advice, if i had a MAP sensor. It is still in its blister packaging from when i ordered it.
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heh heh.... what if you use less that WOT at low rpm and then floor it after 4Krpm?
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Location:
Adelaide
Registered:
May 2003
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Re: Advice on driving a VERY cammy car.
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Mon, 24 January 2005 21:06
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Ill find that out today, i was pretty heavy footed at the khana yesterday.
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Location:
Melbourne
Registered:
May 2002
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Re: Advice on driving a VERY cammy car.
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Tue, 25 January 2005 03:21
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GET A FOUR POINT THREE, or better a 4.8
even a 4AC sprinter starts to feel a bit quick with a 4.3
dodgydan
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Location:
Castle Hill, Sydney
Registered:
February 2004
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Re: Advice on driving a VERY cammy car.
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Tue, 25 January 2005 10:44
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just practice, my car is a bitch to launch with 288 deg cams, twin carbies and a 3.9
i only just perfected the launch on it, i hold it at about 35000rpm and drop the clutch as fast as i can without letting the wheels spin, so they are just screeching a little.
once the clutch is right out and the cars at about 4000rpm...MASH
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Location:
Melbourne
Registered:
November 2003
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Re: Advice on driving a VERY cammy car.
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Tue, 25 January 2005 10:53
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You running a smallport or bigport? I've heard of similar things from TVIS with wild cams. If you have TVIS, disable it so it's always open, or take out the butterflies.
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Location:
Adelaide
Registered:
May 2003
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Re: Advice on driving a VERY cammy car.
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Tue, 25 January 2005 13:04
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Been playing with it a bit today, and i think i have figured out a half decent way to get it to launch properly. Involves a LOT of feathering of the throttle until it gets to 4000rpm and then WOT from there. Pretty annoying to do with the lightened flywheel, but i think thats jsut because i need practice.
Its a 20v quad throttled, TPS sensed, smallport 16v 4AG with 308* cams and a 3.7kg flywheel mated to a quaife 1st and 2nd gears with a 3.9 T series diff.
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On Probation
Location:
nsw
Registered:
March 2004
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Re: Advice on driving a VERY cammy car.
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Wed, 26 January 2005 01:58
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If your dragging put in auto with a highstall and launch control?
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Location:
Toronto, Downtown
Registered:
September 2004
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Re: Advice on driving a VERY cammy car.
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Wed, 26 January 2005 02:12
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| badboybubby wrote on Wed, 26 January 2005 12:58 |
If your dragging put in auto with a highstall and launch control?
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and loose 20kw from the driveterrain
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