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size does matter

This is gonna fly in the face of weedburners post; but then again, by his own admission, he may be high. .
From the looks of that video (even though it shows zero of the launch equation) I’m willing to say that taller slicks with more sidewall would very likely help your situation. Also, I can see the car bouncing in the burnout box. Would seem to me to be a sure fire sign the the shocks are not controlling the suspension adaquately. Better shocks (or stiffer settings), and taller tires are the direction I’d go if it were me.
And there’s always the cold hard fact that launching a clutch car will never be as simple nor repeatable as an automatic car.

Thanks for the vid..... it’s good for a heart-warming smile in the middle of winter.
 
To get the most out of that setup, I would stick with 10x26. You are quite a ways off on your et potential, the most cost effective place to look for that 0.75 will be dialing in the hit of the clutch. That will also allow you to raise launch rpm (pack more energy into your launch), while at the same time reducing your risk of broken parts.

Lets say you have an overkill clutch that can hold 1000ft/lbs behind an engine that only makes 600. If you launch the car and allow that clutch to hit with it's full 1000ftlb capacity, it's going to instantly pull an additional 400ftlbs of inertia out of the rotating assy, which causes the engine to lose rpm. Extra clutch capacity, beyond what it takes to hold the engine's torque, that's what controls how fast the clutch pulls the engine down. Too much extra clutch torque capacity, the clutch either pulls the engine down too fast (bog), knocks the tires loose, or breaks drivetrain parts. But if you dialed the initial hit of that 1000ftlb clutch all the way back to around 700ftlbs, it still holds all of the engine's 600ftlbs of torque, except now it only pulls engine rpm down at a much slower 100ftlb rate. Because the car is gaining speed while the clutch is pulling the engine down, the engine doesn't get pulled down as far.
Here's a graph based on the average acceleration rate for a 1.40 60'...

View attachment 702648

Let's say for this example that line "A" represents the 1000ftlb clutch in the example above, hitting with it's full 1000ftlbs of holding power. 1000ftlbs of holding power is going to pull that 600ftlb engine down at a 400ftlb rate. The result is the engine gets pulled down very quickly (0.325sec) to about 1800rpm. Even if the engine were still making 600ftlbs, that's only 205hp at 1800rpm. That's going to produce a huge bog, and et/60' is going to suffer a lot because of it. But if you were to use something like the ClutchTamer to cut the initial hit of that 1000ftlb clutch back to 900ftlbs, it's not going to pull the engine down as fast, which gives the car more time to accelerate before engine rpm sync's up with vehicle speed (that sync point is where the clutch actually stops slipping). The result would look more like line "B", where the car is able to accelerate to about 20mph. That raises bog rpm to about 2800 where the engine is obviously going to make a lot more power than it did at 1800. Backing the hit of that 1000ftlb clutch off to 800 would result in something like line "C", where the engine stays above 3700. Now the bog point is up to around 420hp. Back the hit off to around 700ftlbs and it would look more like line "D", as the clutch is now only pulling 100ftlbs of inertia out of the rotating assy. That extra slip time allows the engine to stay closer to it's sweet spot for HP production, now it's up to about 550hp thru the low point of the bog.

Grant

Thank you for your explanation, i have definitely to do some home work on my clutch
operation. It's also hard to dial in the suspension here in Europe, the track condition is always changing during a day in case of a lot of oil downs ( public races ).

Marco
 
This is gonna fly in the face of weedburners post; but then again, by his own admission, he may be high. .
From the looks of that video (even though it shows zero of the launch equation) I’m willing to say that taller slicks with more sidewall would very likely help your situation. Also, I can see the car bouncing in the burnout box. Would seem to me to be a sure fire sign the the shocks are not controlling the suspension adaquately. Better shocks (or stiffer settings), and taller tires are the direction I’d go if it were me.
And there’s always the cold hard fact that launching a clutch car will never be as simple nor repeatable as an automatic car.

Thanks for the vid..... it’s good for a heart-warming smile in the middle of winter.
You're right, the car is definitely bouncing, also during the launch (sometimes). I have 3 more clicks on my shocks.

Marco
 
A softer clutch hit won't need as much shock control.

You've got plenty of tire, QA1's, 318 bars, but the clutch is hitting so hard that the car doesn't have time to transfer any weight before it blows the tires off. Back off the clutch hit, the suspension might be fine as it is. Back it off enough, you will be able to launch a lot higher while dead hooking 22psi in your slicks. The hit will actually be softer than an automatic, but the car won't bog and will be much quicker than it is. You won't find a better way to get a manual shift car down a marginal track, and you won't be giving anything up on a good track either.

Grant
 
The conclusion is:

-Keep the tire 10x15x26 ( 28" and a 4.10/4.30 would be better)
-softer clutch engaging
-taking sideview videos for analysis of the rear suspension
-more rebound of the rear shocks if necessary
 
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