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Discussion Starter · #1 ·
Ok guys and girls. I recently just tuned my FoST and shifting at 5.7k like I did when it was stock just doesn't seem the same. Looking at the dyno graph my curve starts to drop around the 4.5kish spot. Any help?? Am i to shift to stay in the power curve right? Some one please explain it to me like I'm 5. Thanks LoL
 

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Ok guys and girls. I recently just tuned my FoST and shifting at 5.7k like I did when it was stock just doesn't seem the same. Looking at the dyno graph my curve starts to drop around the 4.5kish spot. Any help?? Am i to shift to stay in the power curve right? Some one please explain it to me like I'm 5. Thanks LoL
Our turbos are tiny so they are great for quick response and low to mid range power, but the fall on their face higher up the rpms.

When stock, Ford really tries to keep the torque curve flatter so it stays strong for a longer duration. When we tune the cars, we easily get more power, but the power becomes peaky. So we get a huge slug at 3,000rpm and then it starts to fall off right when you said.

So if you are drag racing, or just trying to stay in the power, shift around 5,000rpm or just before. Our power curve for the stock turbo lies 2,700-4,500rpm roughly. Keep the revs in there and the car pulls like a beast.
 

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Discussion Starter · #4 ·
I have been shifting like I have before one thing I have notice is my boost is not like it was. Before I stayed in boost of 21. On the reader now when shifting at the 5.7k range boost reaches about 20 then starts to fall again as too shifting just before 4.7k it puts the boost back at 23ish which feels like a stronger pull.
 

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Discussion Starter · #5 ·
21 was at most what I got before the tune. Now I hit 23 all day. The cobb ap records when I shift at normal 5.7k the boost will be in the 20ish range and only fall from there to 19-18. After a few practice runs shifting at 4.5ish I stay in the boost range of 23 the whole time in the next gear til i reach 4.7k again then drops. If shifting shouldn't I want to be in that 23 boost range instead of 20?? Why should I shift normal if I'll be at a lower boost after the shift? Thanks for the inputs so far
 

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I'd say from the graph you posted, you should shift before 5000, probably at 4500. Your torque falls dramatically over that and HP peaks there. You may still have boost, but you are losing power.
 

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The best way to calc when to shift is based on axle torque and gear ratios. Plot effective axle torque vs vehicle speed for all gears and you'll quickly see when you would want to shift, to get max torque at the wheels.

I plugged in your dyno graph and it told me this:

1-2: 6500
2-3: 6000
3-4: 5500
4-5: 5300
5-6: 5200

This of course assumes that the engine makes the same tq/power in every gear (it may make less in lower gears due to less load, in which case, slightly earlier shifts in the earlier gears may be better). But this is a great starting point at least.

here's my excel sheet in zip format
 

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