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This is a discussion on wrx cobb stage 2 vs. evo within the Comparison: WRX vs World forums, part of the Community - Meet other Enthusiasts category; Originally posted by emosubaru the above explination only works for the WRX(read: works for the werx ) because of the ...

  1. #31
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    Originally posted by emosubaru
    the above explination only works for the WRX(read: works for the werx) because of the torque curve.

    some cars have a steadily increasing torque curve, and most likely you'd want to run those engines to redline, unless the gear was insanely tall and you'd be better off in another gear.

    pretty much what matters is the last paragraph of my previous post...



    if the torque/hp(it's all the same thing being measured, just like lenght and cm/in.) at this RPM that is being applied to the current gear makes the car accelerate at a greater rate than the matching torque/hp at the matching RPM in the next gear, it's not time to shift yet.


    Yes, I made a generalization, gearing still has an enormous effect. This is why there is such thing as "Drag racing gears" and why Nascar cars do like 7.1 0-60 time but then still finish a quarter mile @ 130 mph(!)


    but still, I'm looking at the dyno plots and the gear ratios:
    1st - 3.454
    2nd - 1.947
    3rd - 1.366
    4th - 0.972
    5th - 0.738

    So we're talking about a stock WRX.

    notice 2/1 = .564, and * 7300 (fuel cutoff) = 4115 rpm.

    Now for the shift for 1st to 2nd that's a huge difference TQ @ 4115 rpm is greater than the ratio between 2/1. (well just eyeballing the dynoplot it's pretty close).
    But remember, lower gears also have less boost. 1st gear is like 9 psi on stock cars right? And dyno graphs are all in 3rd or 4th gear.

    But looking at the other ratios:
    3/2 = .702 = 5122 rpm
    4/3 = .712 = 5194 rpm
    5/4 probably irrelevant to racing.

    Now I'm looking at the dyno of the Vishnu reflash on a stock car, and the ratio of TQ between redline at ~ 5200 rpm is about 120/160 = .75 and the ratio of HP is about 150/175, .86.

    now the amount of TQ lower gear makes over higher gear (2, 3, 4 gears) is just about 1/.71, about 1.4. That' is still clearly edging out the higher gear EVEN on the Vishnu reflash, where the shift slaps you right into the MIDDLE of the TQ peak.

    So this is a pretty rough, linear calculation but you can still see that it's pretty close.

    Of course, modified wrx would be no question.
    '03 white rex
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  3. #32
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    Re: Shifting at Redline

    Originally posted by Dan00Hawk
    I've been under the impression that for maximum acceleration, you want to shift at whatever RPM will put you at your torque peak in the next higher gear...

    So, if for example, your torque peaks at 4500 rpm, then you want to be at that exact point after you shift. If it requires you to redline to do so, then that makes the most sense. If short shifting is required, then do that.

    You need to take gearing and your torque curve into consideration. I'll see if I can find the mathematical equation somewhere, and use the stock WRX's torque figures and gearing to see what comes up...
    I'm just not sure where that comes from, b/c reading my last post, even if you have gears that drop you precisely into the peak TQ range (and we all know how this is incredibly hard to do), it's still numerically less after being multiplied through the tranny than the previous gear.
    '03 white rex
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  4. #33
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    Okay, here is what I gathered from a quick search, and plugging in the WRX figures. I copied it from a webpage from a Miata guy, so please excuse my plagarism in the interest of helping us figure this out.

    Question was asked about horsepower, torque, and shift points.

    Road and Track recently had a piece on calculating shift points. The object is to shift at the RPM thatresults in the maximum torque for the gear that you are shifting INTO. Calculate it this way:

    1. Calculate the ratio between the two gear ratios.
    2. Multiply the result by the RPM at which your torque peaks.
    3. The product is the RPM at which you should shift.

    For example, if 1st gear is 3.454 and 2nd gear is 1.947, then 3.454/1.947 equals 1.774. If your torque peak is at 4000 RPM, then 1.774 times 4000 equals 7096, the RPM at which you should shift from 1st to 2nd.

    The following calculations are based off of a stock WRX which has its listed Torque peak at 4,000 rpm, and stock gears.

    Here is how I calculated:

    1st gear = 3.454
    2nd gear = 1.947
    3rd gear = 1.366
    4th gear = .972
    5th gear = 0.738

    Ratio of 1st to 2nd = 1.774 times 4000 = 7096 RPM
    Ratio of 2nd to 3rd = 1.425 times 4000 = 5700 RPM
    Ratio of 3rd to 4th = 1.405 times 4000 = 5620 RPM
    Ratio of 4th to 5th = 1.317 times 4000 = 5268 RPM

    They also mention that things get kind of screwy when you have a very flat torque curve. As (the example Road and Track gave) when you have a turbocharged car such as a Saab turbo. For this car, the shift points are at 1 to 2 at 3745rpm and 2 to 3 at 2908rpm, as the peak torque occurs at 1950rpm. With the flat torque curve, the shift point is definitely less important.
    So shifting at those points, will put you at the "magic" 4,000 rpm point of the torque peak, theoretically providing maximum acceleration, according to Road and Track.

    I think it would be interesting to find out, doing some back to back testing. Maybe we are leaving a few tenths at the track by shifting at redline in everything but 1st gear...

    Still fun to debate and have a good discussion about, though.
    Last edited by Dan00Hawk; 11-10-2003 at 05:23 PM.
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  5. #34
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    Looking at it again, though, seems to go against common sense. We all know how a WRX seems to "fall on it's face" when we shift to 4th. So it seems to make sense to wind 3rd out to redline for all it's worth to avoid that dreaded 4th gear for as long as possible. Like Verc posted, perhaps the numerical mechanical advantage of the lower gear outweighs the "Road and Track" theory...

    Sorry for getting off topic. I'm going to repost in the drag racing section for those interested in continuing this discussion. Well, for those that haven't put me on their "ignore" list, anyway.


    2007 VW GTI 6 spd. No times yet
    2000 Firehawk convertible 6spd- 12.52 @ 114.7 mph. 2.09 60'

    Sold: 2004 Mini Cooper S. 14.95 @ 93.8 mph.
    Sold: 2004 GTO 6 spd. 13.4 @ 104.5 mph
    Sold: 2002 WRX 5spd. 13.39 @100.7 mph. 1.81 60'
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  6. #35
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    Re: Shifting at Redline

    Originally posted by Dan00Hawk
    I've been under the impression that for maximum acceleration, you want to shift at whatever RPM will put you at your torque peak in the next higher gear...

    So, if for example, your torque peaks at 4500 rpm, then you want to be at that exact point after you shift. If it requires you to redline to do so, then that makes the most sense. If short shifting is required, then do that.

    You need to take gearing and your torque curve into consideration. I'll see if I can find the mathematical equation somewhere, and use the stock WRX's torque figures and gearing to see what comes up...
    That's what I always thought, but with HP because HP is power up high in a gear, while torque is power down low...
    I just bought a STi!!!

    Love it!!!

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    Re: Re: Shifting at Redline

    Originally posted by 04EJ25
    That's what I always thought, but with HP because HP is power up high in a gear, while torque is power down low...
    Wait, I see what you are saying. Be in the torque peak after you shift. That makes sense. Therfore you never lose power after shifting...
    I just bought a STi!!!

    Love it!!!

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  8. #37
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    Originally posted by Dan00Hawk
    Okay, here is what I gathered from a quick search, and plugging in the WRX figures. I copied it from a webpage from a Miata guy, so please excuse my plagarism in the interest of helping us figure this out.



    So shifting at those points, will put you at the "magic" 4,000 rpm point of the torque peak, theoretically providing maximum acceleration, according to Road and Track.

    I think it would be interesting to find out, doing some back to back testing. Maybe we are leaving a few tenths at the track by shifting at redline in everything but 1st gear...

    Still fun to debate and have a good discussion about, though.
    4000RPM's sounds about right, leaving your shift around 6000 to 6500RPMS. Try it out. I was using a G-Tech-Pro in my WRX to calculate max HP and torque. I was using 2nd gear. With a COBB stage 2, Perrin uppipe & DP I was pushing 220HP at around 5750RPM's...
    I just bought a STi!!!

    Love it!!!

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    I believe most the people who run the fastest times with stock turbos all wind out their gears to fuel cut.

    'nuff said. boom.
    '03 white rex
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  10. #39
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    Originally posted by verc
    I believe most the people who run the fastest times with stock turbos all wind out their gears to fuel cut.

    'nuff said. boom.
    And at one point, most people believed the world was flat, that the sun revolved around the earth, and that it was impossible to break the sound barrier, too.

    I still think it is possible to consider that maybe shifting 500 rpms before redline in 2-3 and 3-4 might yield better results than shifting at fuel cut.

    See the Drag Racing section for more discussion on this topic.


    2007 VW GTI 6 spd. No times yet
    2000 Firehawk convertible 6spd- 12.52 @ 114.7 mph. 2.09 60'

    Sold: 2004 Mini Cooper S. 14.95 @ 93.8 mph.
    Sold: 2004 GTO 6 spd. 13.4 @ 104.5 mph
    Sold: 2002 WRX 5spd. 13.39 @100.7 mph. 1.81 60'
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  11. #40
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    Originally posted by Dan00Hawk
    And at one point, most people believed the world was flat, that the sun revolved around the earth, and that it was impossible to break the sound barrier, too.

    I still think it is possible to consider that maybe shifting 500 rpms before redline in 2-3 and 3-4 might yield better results than shifting at fuel cut.

    See the Drag Racing section for more discussion on this topic.
    With all of the goddies in both of your cars (yes, I'm talking about the extra weight items too) and the fact you run those times I'm impressed. I'd take the advise we're both giving now as law. THE WORLD IS ROUND!!!
    I just bought a STi!!!

    Love it!!!

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  12. #41
    Registered User 1fastsubie's Avatar
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    Ratio of 1st to 2nd = 1.774 times 4000 = 7096 RPM
    Ratio of 2nd to 3rd = 1.425 times 4000 = 5700 RPM
    Ratio of 3rd to 4th = 1.405 times 4000 = 5620 RPM
    Ratio of 4th to 5th = 1.317 times 4000 = 5268 RPM
    FWIW, This is very close to what I have found doing my own experiments. The rpms are up a bit because of mods but you get the idea. My car is Stg2 minus engine managment + uppie, with MBC set to 15psi. I have tried shifting all over the place to see how to get the best MPH/ET with my car.

    it goes like this:
    1st->2nd redline+
    2nd->3rd 6500
    3rd->4th 6300

    = best time of 13.31 @102.8mph

    For whatever reason my car likes a shorter shift to 4th gear better than running out 3rd. Even when I was stock I got better times shifting to 4th rather than banging off the limmiter through the traps. I think My MPH shows this too.

    -Fess
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  13. #42
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    Quote Originally Posted by 04EJ25
    How well can your dad drive?

    My suggestions:

    1. From standing still- launch at about 4500-5000 RPM's with a quick but smooth clutch "drop"

    2. Shift at about 6300 to 6500RPM's; NOT redline!

    3. I don't know how the EVO is geared, but try to race him in the 1/8mi, NOT a 1/4...

    You should do well. If you can race a hell of alot better than your dad then try to take him in the 1/4.

    I just got my Stage 2 today with a Perrin uppipe, and Perrin DP (not a full turbo-back). In the rain w/ my G-Tech I ran a 13.7@101MPH. That was in the rain! I've been messing with the G-Tech maps I've stored to find where peak HP is. It looks like my Rex is at 220HP between 5800 to 6500RPM's depending on the run. After that, HP drops off. My fastest 1/8mi run was 8.91@81.9MPH. That was in the rain today too. I hope that helps! Good luck!

    I did the same thing as you and tested my stage 2 wrx in the rain also. I pulled a 4.9 sec.
    0-60! It was amazing! I did it with 23.5 lbs. wheels too! Man maybe I have a freak too!
    My car looks just like this without the skirts and roof wing! Yeah baby!
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  14. #43
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    Quote Originally Posted by WRXin'
    Well that's great! Since I'm a stage 4 I shouldn't have anything to worry about then. Now to find an EVO to race
    Haha, my EVO and I are game

    But, I always thought that Cobb STG 2 and a Stock EVO where pretty much dead even. I know when I had my STG 2 WRX I stayed dead even with my friends STI until 90 then we shut down. However I do know if the race had lasted once I shifted to 4th gear it would of been a murder. If you guys could film your race that would rock I'd love to see it!!

    Staton
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  15. #44
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    Quote Originally Posted by postban
    Well that's interesting, I am Stage2+UP, 214WHP/220WTQ, Dynapack.
    Good to know I have a chance, thought they would mop the roads with me. Rarely see one around here though.
    Over at Godspeed? I dynoed 232 WHP stock at Godspeed in my EVO, but like you said the EVO is around 200 lbs heavier than a WRX so it would have been a great race back then. Last time I was at Godspeed I dynoed 375 WHP on pump gas and 411 WHP on race gas

    Keith
    Miss the wifes WRX, but love my Ralliart!
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  16. #45
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    i beat an evo with intake and bov 4 out of 5 times.. the time i lost was because i had 2 ppl in the car. they jumped out afterwards. =)
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