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Discussion Starter · #1 ·
For those of you who have gotten dyno'd:


At what RPMS do you start to lose power in each gear?

Just looking for the best shift points when I go from a stop. I think I have been hearing the fuel shutoff starts kicking in around mid 5k?
 

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Well, you only do a dyno pull in one gear, usually 4th. I don't think I can really answer that question...
 

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Discussion Starter · #3 ·
It's a sound question though, right? Someone CAN answer? :winks
 

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Your power will be pretty static as to where it drops off, regardless of the gear. If your topping out at 5900rpm in 4th (Seems to be about average... some higher... some lower) then you may as well shift out of there around that range. I find that mine has a real sweet spot between 4000 and 5800rpm. My sweet spot seems to be between 5800 and 6000.
 

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Discussion Starter · #5 ·
Thanks for the replies.
 
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tw0scoops123 said:
For those of you who have gotten dyno'd:


At what RPMS do you start to lose power in each gear?

Just looking for the best shift points when I go from a stop. I think I have been hearing the fuel shutoff starts kicking in around mid 5k?
HP and TORQUE whilst being somewhat different animals, both can be charted against engine RPM, which is totally independant of which gear it is in for the most part, usually you want to "dyno" in top gear (not overdrive) as this gives a good long pull to get data.

The rate at which you get to higher rpms (redline) under load is a function of HP/ TQ/ Gearing/ Mass/ Incline/ Internal Frictional Losses/ Drag/ Hookup/ etc...

That said, all stock 2005 V-8's (not sure of V-6's, prolly similar just shifted down), have basically the same dyno signatures. Building max HP at just about 6,000 rpm and falling off after that due to many factors mostly being in the stock tune (ie, fuel shutoff after 6125 rpm, etc), and building max TQ at about 5,000-5,500 rpm, falling off right after.

I get my best shift "fun" at 5,500 and shift as fast as I can, and am able to spin the tires in 2nd and chirp them in 3rd (max TQ). For all out acceleration, I would shift at 6,000 rpm to get the last bit of accel from the HP curve (max HP) at that rpm; running an ET or "racing" a strip of street for example. This is for my manual shifts. For an automatic, I would assume you can use the same philosophy except expect more losses in the rw hp/ tq curves. An after market tuner will help you do this customizing regarding shift points optimizing.
For those with superchargers, their HP/ TQ curves are very similar except shifted up and usually HP overtakes TQ, with the additional ability to custom tune the software to get upwards of 7,000 rpm and build more HP, bypassing the shutoff assuming they have aftermarket injectors/ MAF to allow for the extra "$ucking". :shiny:
 

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nbk13nw said:
I find that mine has a real sweet spot between 4000 and 5800rpm. My sweet spot seems to be between 5800 and 6000.
Am I misreading something here? Can you clarify where you think your sweet spot it?
 

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First, most dyno runs don't show tq ratios per gear since as stated most are run in 4th with a simple tq/hp graph.

Second, optimal shifting is a factor of tq, gearing & RPM (all other factors being equal). The goal is to not necessarily shift right after max tq but rather determine what the exit tq is leaving a lower gear vs. the entry tq is on the next gear. The goal is the have the smallest delta between these two. Therefore, it may be better to hold the gear longer even though the tq is dropping off in that gear. If you only shift @ max tq per gear you may not be taking advantage of the higher tq as compared to the next gear even though tq dropping. For example, if the tq/RPM shift point into 2nd gear is lower than say red-line tq in 1st gear (even though you passed peak tq in 1st), then holding 1st longer would be best since the tq is still higher than that of 2nd. Then when you shift to 2nd you are at a higher starting tq number than if you only shifted out of 1st @ peak tq.

That said, you can read the per gear tq/RPM charts that are published on the net and magazines to give you an idea of the best shift points, unless you can get a dyno of each gear for your car.
 
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