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Old 12-30-2009, 03:29 AM   #1
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Launching @ 4Krpm problem .... need tips

I wish to solve the problem of launching at high rpm. I own a Vitz\Echo hatchback 2001 model and when I launch @ 4krpm from a dead stop its like the left wheel hops and hammers all body of the car (especially the dash). This problem was already there when I was all stock. First I thought I need some good tires so I said until replacement I prevent hard launches.

Now the engine was upgraded to turbo, the gearbox upgraded with LSD and tires upgraded to Toyo 888 series and the problem seems to be on the 2 wheels now!!

I have all things related to suspension still stock... so from where to begin?? Please I am in a budget so don't throw words if you are unsure.

I don't know if it's a problem with my car or the model itself... I am sure that Toyota Starlets haven't that problem.
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Old 12-30-2009, 05:05 AM   #2
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wheel hop is at least partly a function of engine movement.

1. Are you using stock engine mounts and trans mount (dogbone)? An upgrade there will help you a lot, especially with the increased power you are making.

2. What shocks and springs in the front?
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Old 12-30-2009, 10:09 AM   #3
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Rear engine mounting is upgraded to nylon hard mount while side mounts are stock.
As in regards trans mounting it's probably custom due to some position issues.

Shocks and springs are still RS standard version
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Old 12-30-2009, 11:13 AM   #4
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Sounds like it's time to harden up more of the engine mounts. That is really the only way to help with wheel hop.
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Old 12-30-2009, 01:40 PM   #5
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either get better suspension upgrades, or go to home depot, get some big thick washers, and make some solid motor mounts from those. You won't wheel hop anymore!!!!

Cheap, effective, and so cash
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Old 12-30-2009, 02:02 PM   #6
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When I upgraded the rear engine mount the car vibrates like hell... I can imagine how it could be with all mounts hardened!!

I was more suspecting shocks or harder springs instead...

The thing is that also when I was with a stock 1.3L engine the wheel hop was there aswell!
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Old 12-30-2009, 02:16 PM   #7
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definitely shocks.

also the trans mount and the rear engine mount are the same thing. Let's see some pics of that mount.

I have TRD engine mounts and a BeatRush trans mount. My car is a little louder inside, but not too bad, and my shifts and launches are rock solid.
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Old 12-30-2009, 02:26 PM   #8
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Better shocks should help. Specifically, more rebound damping in front and more compression damping in the rear to resist the rapid transfer of weight to the rear on launch. Stiffer rear springs would probably help, as well, for the same reason.

Grippier tires will actually make wheel hop worse unless they don't spin at all. Less-grippy tires will just spin and not grab and hop. Add grip and the tire tries to hang on, but can't quite do it. Every time they grab, you get a jolt of rearward weight transfer (rear goes down, front goes up -- hence the suggestion for rear compression damping and front rebound damping) and when they spin, you get a little less of a jolt in the opposite direction.

In the extreme, you dump the clutch, you have enough grip to start a launch, but all the weight immediately transfers HARD to the rear, leaving the front tires light... the front tires spin, the acceleration ceases, the weight transfers back to the front, the tires hook up again... and the same thing happens again several times.

Keeping the suspension movement more controlled (not STIFF, just controlled) will help minimize hop.

There is much you can do to try to address the problem, but probably the biggest thing is to just launch smoother. Slip the clutch a little, maybe launch at 3500 instead of 4000? Try to keep the front tires hooked up so that they don't hop.

Toyota Starlet... you can't compare. It's RWD. When you launch a RWD car, the weight transfer to the rear HELPS the car to hook up.

Simplest/cheapest thing you can do is fit a set of adjustable shocks. For hard launches, set the front shocks somewhere in the middle and the rear shocks full stiff. Then adjust your technique to fit the car. Not every car is going to launch well at 4000 rpm!
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Old 12-30-2009, 02:28 PM   #9
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Quote:
Originally Posted by cali yaris View Post
definitely shocks.

also the trans mount and the rear engine mount are the same thing. Let's see some pics of that mount.

I have TRD engine mounts and a BeatRush trans mount. My car is a little louder inside, but not too bad, and my shifts and launches are rock solid.
Yes but the trans has also a custom plate to hold it aswell.... will post pics when I have time for sure... RE: TRD engine mounts, here they say they aren't worth considered the price. Custom mounts are way harder and cheaper.

Its probably shocks but I don't know for sure ... and that's why I posted here though
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Old 12-30-2009, 02:47 PM   #10
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Thanks Loren for the deep info on topic...

So what Brand and type of shock do you recommend for my Vitz 2001 NCP10?

Quote:
Originally Posted by Loren View Post
There is much you can do to try to address the problem, but probably the biggest thing is to just launch smoother. Slip the clutch a little, maybe launch at 3500 instead of 4000? .
I am building a car to drag race... this must launch above 5K for a good start. Of course I have to be able at 4K before


Quote:
Toyota Starlet... you can't compare. It's RWD. When you launch a RWD car, the weight transfer to the rear HELPS the car to hook up.
I was comparing to the 1990+ Starlets which any of them aren't RWD.
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Old 12-30-2009, 06:16 PM   #11
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Parmas, what tires are you using? Got drag slicks yet?
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Old 12-30-2009, 07:12 PM   #12
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Quote:
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I was comparing to the 1990+ Starlets which any of them aren't RWD.
Ah, okay. The Starlet was only sold in the US in the early 80's... as RWD.

Any adjustable performance shock is going to be better than your stock shocks. None of them are designed for drag racing, though. They're generally going to be valved for road course use or for "agressive street" driving. But, you can use their adjustability to your advantage. As I said, probably something like full-stiff in the rear and a little (maybe even a lot) softer in the front.

The ideal setup would be custom valved shocks/struts with matched springs all set up by a suspension engineer who knows FWD and has drag racing setup experience. But that's gonna cost big bucks. Probably well over $2000.
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Old 12-30-2009, 08:11 PM   #13
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suspension upgrades like springs, coil-overs and shocks won't solve the problem.

Motor mounts help. Best thing to do is to upgrade the A-arm bushings to urethane or spherical bearings. Wheelhop is causeed by rotational movement of the A-arms.
The other thing you can do is to make traction bars, this will eliminate wheelhop all together.

this is what a traction bar set-up looks like for a fwd car, it links the front control arms to the lower core support.....

http://www.full-race.com/catalog/pop...7756e08be3c159


you may even be able to make a Honda set-up work with some fabrication
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