TSP Stage 3 vs. BTR Stage 4 Cam

[acammer]

Originally Posted by Taylortoons

If I could change one single thing in my car, it would be this. It's difficult to keep the engine in boost during the 3-4 shift.

You'd probably love the mm6 (1LE) gear ratios in your car. First and second would be longer and plant better, thirds just a little longer, but what drop you much nicer into fourth. Guys pull em out for auto swaps all the time, just keep your eyes open.

[suprchrgd]

My BTR starts dropping power around 6500, so I don't see any point in going much further past this? What rpm are you guys shifting at with your cammed setups and gearing?

acammer:
you think the rod mod is really worth the "bang for the buck"? I have looked into this a few times, just haven't made the commitment yet. I have read good things, but sometimes its hard to take what people say on these boards as everyone seems to have a different experience/advice with the same setups...

on a side note, i did pick up 200 ftlbs of tq on the 150 shot of nitrous, so I think the stg 4 btr cam does okay on the juice.. definitely helps this car get moving!!

[acammer]

Originally Posted by suprchrgd

My BTR starts dropping power around 6500, so I don't see any point in going much further past this? What rpm are you guys shifting at with your cammed setups and gearing?

If you make peak power at 6500, you should definitely be rev'ing past that point. The common misconception on shift points is that you want to shift at peak HP. That's bogus. You want to shift (assuming your car can tolerate the RPM) at whatever RPM puts you're next gear's rpm at a point where you generate the highest average HP throughout the gear.

Let's take a look at a dyno chart of my car as an example. If I shift from 3rd to 4th at 6500 where I make peak power that would drop me back down to 4500 rpm in 4th (yellow lines). Compare that to riding 2nd out to 7200rpm which drops you back to 5000rpm (green lines) and look at how much average power you gain. When you shift at peak power you fall back to an RPM with less power - 350hp vs. 405hp in this example. You do roll past peak power and HP begins to decline, but it's nowhere near the difference you get with the earlier shift - the average power is up significantly with the later shift.

If you sample the two curves at the lowest, highest, and 3 midway points, the yellow curve averages 426rwhp, and the green curve averages 450rwhp. So, to shift at peak, vs. past, you're giving up an average (very loosely calculated in this example) of 25rwhp.

With a car that really lays over after it peaks there comes a point where you're just revving but power has dropped off so much you're no longer effective. With even the stock cam in an LS3, they pull well past their peak and still deliver strong power right to the factory rev limiter at 6600. This dyno graph doesn't show it, but we've pulled this cam all the way out to 7400rpm and it was barely rolling over - I extended it out some for the purposes of this example. For me, I'm comfortable taking the valve-train to 7200 regularly, so that's where we put the limiter, and I target shifts in the 7100rpm range.

[acammer]

Originally Posted by suprchrgd

acammer:
you think the rod mod is really worth the "bang for the buck"? I have looked into this a few times, just haven't made the commitment yet. I have read good things, but sometimes its hard to take what people say on these boards as everyone seems to have a different experience/advice with the same setups...

on a side note, i did pick up 200 ftlbs of tq on the 150 shot of nitrous, so I think the stg 4 btr cam does okay on the juice.. definitely helps this car get moving!!

I do think the rod-mod is worth it - especially since it's so reasonably priced. GPI has done a fair amount of testing on this and you can find those results on their website here. It's not just the peak numbers you want to pay attention to, although they do pick up like 10-15 peak rwhp, but the gains under the peak in torque from 3000 on up are significant.

It's $400 for rod-mod and porting - that's a cheap price for a real 10+ hp pick-up, and more importantly a fatter curve throughout - a car like yours or mine with a BIG cam can really take full advantage of that.

A cam like the BTR4 is gonna love spray - all that exhaust duration helps evacuate the cylinder and get another good charge in there. I bet it feels awesome too!

[suprchrgd]

I totally understand what your saying with the shift points. I just wasn't sure how the rpms correlated to the best rpm shift point to stay in the more "peak" power range after the shift. I too have my limiter set to 7200, so I can easily shift at 7000k.

Would be nice to see a chart with the hp/tq curve compared to rpms with shift points on it...

[acammer]

Originally Posted by suprchrgd

I totally understand what your saying with the shift points. I just wasn't sure how the rpms correlated to the best rpm shift point to stay in the more "peak" power range after the shift. I too have my limiter set to 7200, so I can easily shift at 7000k.

Would be nice to see a chart with the hp/tq curve compared to rpms with shift points on it...

It's safe to say, that with the type of power these cars make on the top end, you want to send it as far as you trust your valve-train.

Did the chart I posted not show up for you? It should be showing exactly what you asked for, hp/tq over rpm with two different shift points/ranges outlined.

[KB85]

Originally Posted by acammer

It's safe to say, that with the type of power these cars make on the top end, you want to send it as far as you trust your valve-train.

Did the chart I posted not show up for you? It should be showing exactly what you asked for, hp/tq over rpm with two different shift points/ranges outlined.

chart shows up and makes perfect sense. You are a better man than me creating that and typing it all out.

[acammer]

Originally Posted by KB85

chart shows up and makes perfect sense. You are a better man than me creating that and typing it all out.

It's pretty interesting to see the difference. I hear/see people make drag passes short shifting a little, and then they come back complaining about a weak trap speed. You need to take everything you can when it comes to RPM - send it as far as you trust it. If you've got some good BTR hardware keeping the valves under control, send her all the way! I'm gonna bump my limiter to 7400 this fall.

[suprchrgd]

with what your saying here, i could raise my n2o set points from a shut off at 6300 to shut off at 6800 and shift at 7000

[acammer]

Originally Posted by suprchrgd

with what your saying here, i could raise my n2o set points from a shut off at 6300 to shut off at 6800 and shift at 7000

That sounds like an excellent idea!

What controller do you use? I've been flirting with N20 in the future - I think I'd like to do something that has a gear lockout and a progressive ramp, so I can leave w/o spray in 1st, spray 2nd with like a 75 shot, then lay a 150 to 3rd and 4th.

[suprchrgd]

Originally Posted by acammer

That sounds like an excellent idea!

What controller do you use? I've been flirting with N20 in the future - I think I'd like to do something that has a gear lockout and a progressive ramp, so I can leave w/o spray in 1st, spray 2nd with like a 75 shot, then lay a 150 to 3rd and 4th.

not running a progressive yet. when i do, will will most likely being using the promax from nitrous outlet.

so, right now, all the nitrous at once. i have it coming in at 3300.
i would also thinking about getting this wideband too. has extra safety with being able to shut the system down within set afr parameters and bottle pressure.

https://www.innovatemotorsports.com/products/psn1.php

[Taylortoons]

Originally Posted by acammer

You'd probably love the mm6 (1LE) gear ratios in your car. First and second would be longer and plant better, thirds just a little longer, but what drop you much nicer into fourth. Guys pull em out for auto swaps all the time, just keep your eyes open.

I compared the specs on the 1LE vs the SS and see what you're saying related to the 3-4 gear ratio. I also noticed the 4-5 shift is quite different as well, but this time, in favor of the SS, 1.00 to .84 vs 1.00 to .74.

I would be interested in 4th moving to around 1.25, then 5th at 1.00. The final gear could drop to .50 and be just fine.

Currently, I don't use 6th gear at all.

I did try your example of kicking up the rpms on my way to work this am. I shifted 3-4 at about 6500 rpm and 4th gear pulled pretty hard.

[acammer]

Originally Posted by Taylortoons

I compared the specs on the 1LE vs the SS and see what you're saying related to the 3-4 gear ratio. I also noticed the 4-5 shift is quite different as well, but this time, in favor of the SS, 1.00 to .84 vs 1.00 to .74.

I would be interested in 4th moving to around 1.25, then 5th at 1.00. The final gear could drop to .50 and be just fine.

Currently, I don't use 6th gear at all.

I did try your example of kicking up the rpms on my way to work this am. I shifted 3-4 at about 6500 rpm and 4th gear pulled pretty hard.

Sounds like you think like I do - I think a 1:1 in 5th, not 4th could be fun. The MT82 in later Mustang's has that setup - they are 3.66, 2.43, 1.69, 1.32, 1.00, 0.65. It's not a real strong trans though. The LS has a broad enough power curve where the extra shift in the quarter mile is probably not worth it anyways. But it would be fun with a 3.73 out back!

Check out the MG9 (ZL1 trans) ratios - same as a 1LE in 1-4, but 5th is a 0.84 and 6th is a 0.63. Just nice spacing throughout the whole box. Definitely more cruising RPM in 6th, which with a cammed car isn't such a bad thing anyways!

[KB85]

Originally Posted by acammer

It's pretty interesting to see the difference. I hear/see people make drag passes short shifting a little, and then they come back complaining about a weak trap speed. You need to take everything you can when it comes to RPM - send it as far as you trust it. If you've got some good BTR hardware keeping the valves under control, send her all the way! I'm gonna bump my limiter to 7400 this fall.

Im peaking at 7k...shift at 7200 until I can get a few things worked out then 7400 by October