Best Shift point ?

[Deer Killer]

Another of the good old plug n' chug eh?

 

Again, someone show me the equation for turning crank HP into acceleration and force. DO IT. We will simply be able to cancel out an extra RPM/RPM and you will reduce the equation to torque and primary forward force. You do have the book in front of you. Most likely this will assume perfect transmission, which we don't have. If you had the perfect transmission then yes, you would want the point of max power, but no one has this. Real engine, real transmission, vs being educated into a hole you can't get out of. It's all theory in there.

[Brady]

Right, this isn't a perfect transmission, but torque is lost through drive line inefficiencies, so the theoretical application of torque is as good as the theoretical application of power.

 

To do an easy shift point analysis, you just need an accurate power curve and then the rpm the car is running in each gear. You can make a graph and where one speed/rpm in a gear intersects with another, you shift. In the cases of 1st and 2nd gear, the curves will never intersect with 2nd and maybe 3rd gear, so you just shift at red line.

[700watts]

Ahhh ha, that sounds good

Side note……when I was reading it occurred to me that Nissan developed a CVT trans….I wander if that gives max power at all times.

[Brady]

Theoretically, a CVT would rock your socks in the name of maximum acceleration. I've never personally seen one that works very well for performance, but usually do very well for fuel efficiency.

 

I know Toyota and Audi have CVTs in their arsenal as well.

 

Audi had an A4 available with it, but they offered a mode with shift points because consumers in testing couldn't get used to having a car that didn't "rev" when they accelerated.

[BOY]

Subaru had a CVT.. heck we were the first manufacturer to offer an ECVT... but we won't talk about that.

 

Now you need to get past HS algebra and look at the calculus involved to get the correct answer. You need to look at the area under the hp curve and the appropriate slopes at the RPM ranges of interest. If the car is geared correctly you should shift at the point that keeps it in its optimized powerband.

 

Low torque high rev motors need to shift later than higher torque lower rev motors... duh. You need to analyze the real world data to determine what shift point puts you in the fattest part of the powerband the longest. Shift to soon and miss the power up top while "working" to get back into the powerband; shift too late and lose power up top and get into the curve too late will make for slow times at the track. Each shiftpoint may differ slightly depending on gearing

[700watts]

Subaru had a CVT.. heck we were the first manufacturer to offer an ECVT... but we won't talk about that.

 

Now you need to get past HS algebra and look at the calculus involved to get the correct answer. You need to look at the area under the hp curve and the appropriate slopes at the RPM ranges of interest. If the car is geared correctly you should shift at the point that keeps it in its optimized powerband.

 

Low torque high rev motors need to shift later than higher torque lower rev motors... duh. You need to analyze the real world data to determine what shift point puts you in the fattest part of the powerband the longest. Shift to soon and miss the power up top while "working" to get back into the powerband; shift too late and lose power up top and get into the curve too late will make for slow times at the track. Each shiftpoint may differ slightly depending on gearing

So your saying maxemize the erea under the curve ?

[BOY]

So your saying maxemize the erea under the curve ?

 

too long winded

 

sorry, too much bickering about the same thing said different ways and I got long winded

[Brady]

too long winded

 

sorry, too much bickering about the same thing said different ways and I got long winded

At least you get it.

 

The reason I like to leave torque out of the equation is because it confuses most people, so they look at where the engine makes peak torque and they think that they will be fastest if they keep the car in the main "torque band" of the engine - which isn't true. If you forget about torque, and just focus on keeping your car in the meaty section of the power band, you'll be faster.

 

It's easier to remember and easier to figure out while driving.

[700watts]

too long winded

 

sorry, too much bickering about the same thing said different ways and I got long winded

 

it's alll good I've been known to do the same thing....

[SpeedNeeder]

wheel torque is what counts!

[Deer Killer]

At least you get it.

 

The reason I like to leave torque out of the equation is because it confuses most people, so they look at where the engine makes peak torque and they think that they will be fastest if they keep the car in the main "torque band" of the engine - which isn't true. If you forget about torque, and just focus on keeping your car in the meaty section of the power band, you'll be faster.

 

It's easier to remember and easier to figure out while driving.

http://lachlan.bluehaze.com.au/usa2001/vermont2001/05jul2001a/mvc-014f.jpg

 

You can't feel power, the only way to know the power band is to look at a graph, and then of course the graph isn't correct because it doesn't account for real world conditions like boost and turbo lag. This should be astoundly obvious to anyone who drives a GT, especially a stage 2 GT. Hit the throttle at 3k, and hit the throttle at 6k. Bleh.

[Brady]

 

You can't feel power, the only way to know the power band is to look at a graph, and then of course the graph isn't correct because it doesn't account for real world conditions like boost and turbo lag. This should be astoundly obvious to anyone who drives a GT, especially a stage 2 GT. Hit the throttle at 3k, and hit the throttle at 6k. Bleh.

That's a great concept if you only have ONE gear to choose from, but my real world Legacy has 5 gears. And to extract the most acceleration out of the car, I get the car to the Power band as quick as I can, then I try to keep it there. Once I shoot past the one solid rush of acceleration in 1st gear at around 3000-3500 rpm, I never go back near it. Why? Because I'm not making nearly as much power if I shift into second early. Sure, I'm making much more torque at the flywheel, but the reduction isn't great enough to keep the acceleration as high.

 

Let's say we put in a gear before first gear. You'd hit 3500 rpm and you'd rip all 4 tires free, and once you hit 6000 rpm, you'd still try to avoid getting down in the lower torque if you could. Because Power = acceleration. As long as you have more gears to choose from, you will always want to keep the car in the meatiest section of the powerband to maximize acceleration.

 

You just don't go from 2nd gear to third gear and start making more torque and think "Wow! Feel that torque!"

[Brady]

Here's another way to look at it:

 

Take two engines.

 

Both make 300 ft lbs peak torque.

 

One makes max torque at 2626 rpm - this one has a small turbo that runs out of steam early

 

One makes max torque at 5252 rpm - this one has a big turbo that take a while to spool up

 

Both engines are mounted to the same transmission in the same car.

 

Which one will pull harder when it's making peak torque? Which car will be faster? Both cars have equal torque, so why is the car with more power faster?

 

Power = Acceleration

[Deer Killer]

Watts = Pounds

Dogs = Cats

 

I can just say whatever I want.

 

:/

[Brady]

Watts = Pounds

Dogs = Cats

 

I can just say whatever I want.

 

:/

Point is that they're going to pull equally hard at max torque - they'll be putting the same amount of torque to the wheels, but the car with the higher horsepower is going to be much faster. You'll never build a gasoline powered engine that has a perfectly flat torque band ... so we deal in the realm of power. For real world driveability, I'll take a car with good torque down low, but if we're talking about all out speed and acceleration, power is going to take the crown every day of the week.

[BOY]

You do feel the engine torque, its what gets you out of the hole and what your butt dyno is calibrated for. What moves the car is torque. What moves the car fast is power. My RS-T will whoop a 2.0 WRX in 1-3, I ahve a tiny RHB5VF-10 and a mild street cam that makes all its power below 5k RPMs. I had the car on the dyno years ago and put down 197lb-ft at 3000 RPMs but after that the torque took a nosedive due to the small turbo (much like a restrictor on a rally car). The HP was on in the 155-160 range (don't recall the exact #). Now I've tuned the car a little better but I'd still say that I'm under 170 awhp but still making at least the ~200 lb-ft. In a straight away a WRX will walk me on the hwy, I make a lot more awtq than he does but he has the power up top (and we're geared completely differently, which doesn't help).

 

I wasn't too long winded was I

[Brady]

You do feel the engine torque, its what gets you out of the hole and what your butt dyno is calibrated for. What moves the car is torque. What moves the car fast is power. My RS-T will whoop a 2.0 WRX in 1-3, I ahve a tiny RHB5VF-10 and a mild street cam that makes all its power below 5k RPMs. I had the car on the dyno years ago and put down 197lb-ft at 3000 RPMs but after that the torque took a nosedive due to the small turbo (much like a restrictor on a rally car). The HP was on in the 155-160 range (don't recall the exact #). Now I've tuned the car a little better but I'd still say that I'm under 170 awhp but still making at least the ~200 lb-ft. In a straight away a WRX will walk me on the hwy, I make a lot more awtq than he does but he has the power up top (and we're geared completely differently, which doesn't help).

 

I wasn't too long winded was I

 

No, not long winded at all. The key here is again that the gearing isn't equal. If you threw the same transmission in both cars, the WRX would become the faster vehicle again as long as you kept the respective motors in their respective power bands.

 

Out of the hole, as you note, the RS-T would be faster, but the WRX would reel you in quick. I don't think anyone is looking to build a car that does it's absolute fastest 60' time if it means you can't ever get the car moving after the initial pull.

[Brady]

How much boost are you running on the RS? What kind of engine management? Stand alone or did you use the LINK piggyback. Stock pistons? '99 had the 9.7:1 CR, right?

 

I want to hear more about this RS-T!

 

When I think about how much I've spent on the Legacy in the last year, I sometimes wish I had just kept my '02 RS and slapped a turbo in it and owned the car outright!

[700watts]

You do feel the engine torque, its what gets you out of the hole and what your butt dyno is calibrated for. What moves the car is torque. What moves the car fast is power. My RS-T will whoop a 2.0 WRX in 1-3, I ahve a tiny RHB5VF-10 and a mild street cam that makes all its power below 5k RPMs. I had the car on the dyno years ago and put down 197lb-ft at 3000 RPMs but after that the torque took a nosedive due to the small turbo (much like a restrictor on a rally car). The HP was on in the 155-160 range (don't recall the exact #). Now I've tuned the car a little better but I'd still say that I'm under 170 awhp but still making at least the ~200 lb-ft. In a straight away a WRX will walk me on the hwy, I make a lot more awtq than he does but he has the power up top (and we're geared completely differently, which doesn't help).

 

I wasn't too long winded was I

 

not at all:icon_bigg

[700watts]

http://lachlan.bluehaze.com.au/usa2001/vermont2001/05jul2001a/mvc-014f.jpg

 

You can't feel power, the only way to know the power band is to look at a graph, and then of course the graph isn't correct because it doesn't account for real world conditions like boost and turbo lag. This should be astoundly obvious to anyone who drives a GT, especially a stage 2 GT. Hit the throttle at 3k, and hit the throttle at 6k. Bleh.

 

I have to admit.......This post and or pic is hilarious :lol: :lol: !!!

[Brady]

I think it's hilarious too, because boost and turbo lag are completely irelevant. The post only makes sense if you only have one gear to choose from. Otherwise, I'd rather hit the throttle at 6000 rpm in 2nd gear than hit the throttle at 3000 rpm in 3rd gear ... but maybe that's just me.

[Deer Killer]

I think it's hilarious too, because boost and turbo lag are completely irelevant. The post only makes sense if you only have one gear to choose from. Otherwise, I'd rather hit the throttle at 6000 rpm in 2nd gear than hit the throttle at 3000 rpm in 3rd gear ... but maybe that's just me.

Actually you don't know that until you account for turbo lag, you could be producing less boost in second, when you shift into 3rd with a pre-spooled turbo you could get a lot more torque out of the engine than you were expecting. This happens in first gear a lot, and changes all over the place depending on your mods and state of tune.

[BOY]

How much boost are you running on the RS? What kind of engine management? Stand alone or did you use the LINK piggyback. Stock pistons? '99 had the 9.7:1 CR, right?

 

I want to hear more about this RS-T!

 

When I think about how much I've spent on the Legacy in the last year, I sometimes wish I had just kept my '02 RS and slapped a turbo in it and owned the car outright!

 

I run between 6 and 8 psi on a stock block, WRX injectors/pump/intercooler/recirc vavle. EM is GReddy Emanage and it is really half-assed for the tune. I also have a custom bent header w/ integral UP, custom DP (2 1/2" tubobaco w/ high flow cat), cobb stage1 cams... shall I go on? The "kit" (junkyard salvage really) cost me less than $1500 (including the exhaust)! I've been boosted for ~20,000 mi now

 

As for the different powerbands/gearing I've seen swapped RSs -vs- stock WRXs and the gearing makes all the difference... equally modded the WRX will start to pull up top...

[700watts]

I run between 6 and 8 psi on a stock block, WRX injectors/pump/intercooler/recirc vavle. EM is GReddy Emanage and it is really half-assed for the tune. I also have a custom bent header w/ integral UP, custom DP (2 1/2" tubobaco w/ high flow cat), cobb stage1 cams... shall I go on? The "kit" (junkyard salvage really) cost me less than $1500 (including the exhaust)! I've been boosted for ~20,000 mi now

 

As for the different powerbands/gearing I've seen swapped RSs -vs- stock WRXs and the gearing makes all the difference... equally modded the WRX will start to pull up top...

pictures please ?

[Brady]

Sounds like a great setup!

 

What kind of EGTs do you typically see?