[GunMetalGrey]

Originally Posted by BMWM.D.

Did you see the screen shots from Ted Jannetty’s testing that I posted above? Exact same nose over up top on the manifold pull. Thats the reason there can be something like 40 whp gained. It’s not magic or rocket science. The headers simply extend the powerband. The manifolds drop like crazy, and create a delta.

In the chart you posted, it’s making about 510 whp at 6400-6500 with the manifolds. It’s making about 550 with the headers. It’s pretty easy to see. Running the manifold car an extra 100 rpm wouldn’t have changed anything. It actually may have made the delta bigger.

And Ted’s testing was a much better real world example. He did what pretty much everyone would. Intake first, then tune. Then headers and optimize the tune again. He got 27 whp at peak, but again, there are bigger gains higher up as the manifolds fall on their face. That’s the RPM range my A10 stays in say on a quarter mile pull. It’s probably how I ran a 10.79 with really just those headers and Rotofab as power mods.

I’ve been obsessed with engine power and dyno curves for the last 20 years, so excuse my detailed response. I get into this shit, lol.

Thanks that’s very informative, But isn’t the difference a lot more than 40whp at the shift point? Looks more like 50whp no?

[BMWM.D.]

Originally Posted by GunMetalGrey

Thanks that’s very informative, But isn’t the difference a lot more than 40whp at the shift point? Looks more like 50whp no?

I was just guesstimating based on the chart plot points. Not very scientific, I know. My real point was that the gains really are more than the basic numbers portray. Power under the curve is really what matters.

And you’re right about the 1-2 shift, and probably the 2-3 shift, as far as having more rpm drop. 1-2 sometimes short shifts as well. But still, it hits that area of the curve (6000+) in every gear. You’ll be spending some time in that range for sure on a WOT pull to high speed. If this big delta was at 2500 rpm or something, I’d say who cares.

Now I have to look at some of my PDR videos from the track.

[GunMetalGrey]

Originally Posted by BMWM.D.

I was just guesstimating based on the chart plot points. Not very scientific, I know. My real point was that the gains really are more than the basic numbers portray. Power under the curve is really what matters.

And you’re right about the 1-2 shift, and probably the 2-3 shift, as far as having more rpm drop. 1-2 sometimes short shifts as well. But still, it hits that area of the curve (6000+) in every gear. You’ll be spending some time in that range for sure on a WOT pull to high speed. If this big delta was at 2500 rpm or something, I’d say who cares.

Now I have to look at some of my PDR videos from the track.

haha that's what I figured, I've just been missing so many basic observations I wanted to double check those whp numbers and make sure I wasn't missing something else obvious. And yes totally agree with you, still very important and useful power despite those earlier gear shift points.

I just still can't believe that the stock LT4 in our cars actually drops in power over the last 500 rpms before shifting, I'm shocked that it doesn't shift at peak power, is this normal for high performance cars?

[Joshinator99]

Originally Posted by GunMetalGrey

I just still can't believe that the stock LT4 in our cars actually drops in power over the last 500 rpms before shifting, I'm shocked that it doesn't shift at peak power, is this normal for high performance cars?

Yes, because you have to think about the RPM that you end up at *after* your shift. Shifting at exactly peak power means you’d spend very little time there at peak power, plus you’d probably end up dropping the RPM too far back after the shift. So by carrying it a bit further, the car likely stays in a better powerband vs shifting at exactly peak power.

[17CamaroZL1]

Originally Posted by Joshinator99

Yes, because you have to think about the RPM that you end up at *after* your shift. Shifting at exactly peak power means you’d spend very little time there at peak power, plus you’d probably end up dropping the RPM too far back after the shift. So by carrying it a bit further, the car likely stays in a better powerband vs shifting at exactly peak power.

Exactly this ^^

And you're also using the mechanical advantage of the lower gear a bit longer.

[GunMetalGrey]

Originally Posted by Joshinator99

Yes, because you have to think about the RPM that you end up at *after* your shift. Shifting at exactly peak power means you’d spend very little time there at peak power, plus you’d probably end up dropping the RPM too far back after the shift. So by carrying it a bit further, the car likely stays in a better powerband vs shifting at exactly peak power.

Just remembered Ted is shifting a manual, so I assume this would be different for an auto like the A10 since it would shift exactly at 6500rpm and would shift faster.
If so, I assume the power gains over and above the peak to peak 27whp would be less with an auto because it would never get to that higher rpm

[Joshinator99]

Originally Posted by GunMetalGrey

Just remembered Ted is shifting a manual, so I assume this would be different for an auto like the A10 since it would shift exactly at 6500rpm and would shift faster.
If so, I assume the power gains over and above the peak to peak 27whp would be less with an auto because it would never get to that higher rpm

You would just retune the TCM in the A8/A10 so that the shift points of your particular car work well with your engine’s improved operating powerband. Tuning the TCM is a big part of getting your car’s improved power to the ground... Also keep in mind that the auto gearboxes have a better spread to their gear sets vs an M6. We have less RPM fall off to begin with, and will stay in the engine’s optimum powerband more readily too...

[GunMetalGrey]

Originally Posted by Joshinator99

You would just retune the TCM in the A8/A10 so that the shift points of your particular car work well with your engine’s improved operating powerband. Tuning the TCM is a big part of getting your car’s improved power to the ground... Also keep in mind that the auto gearboxes have a better spread to their gear sets vs an M6. We have less RPM fall off to begin with, and will stay in the engine’s optimum powerband more readily too...

Ah ok, Good to know, I was wondering if the TCM tune changed the shift point, thanks!
Any idea what the shift point can be changed to in terms of max rpm with only simple bolt on mods like CAI and Headers (no cam or valve train changes)?

[GunMetalGrey]

Originally Posted by GunMetalGrey

I just still can't believe that the stock LT4 in our cars actually drops in power over the last 500 rpms before shifting, I'm shocked that it doesn't shift at peak power, is this normal for high performance cars?

Just realized that was only after Ted tuned the car on 100 octane... so in stock form on the stock tune the car does not drop in power over the last few hundred rpm before the shift point.