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post #11 of 23 (permalink) Old 04-18-2014, 06:02 PM
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Originally Posted by CanyonRider View Post
Further analysis. Our torque curve is relatively flat from 4500 to 5200 - meaning this is the range where the car pulls hardest. If we look at this 700rpm sweet spot range:

With 25.5" tires:
Sweet spot torque:
1st: 26-30
2nd: 45-52
3rd: 66-76
4th: 87-101
5th: 113-130

From the video, you can see the car accelerates well up to about 100mph. I am shifting from 4th to 5th at around 100, just as the toque curve is dropping off. But when I get to 5th, I am well below the sweet spot of the torque curve and the car falls flat - damn 0.733 5th gear!!
CR
Just a reminder that the peak torque is where you get the maximum HP/rpm ratio from the engine.

HP=TN/5250, T= (HP/N)x5250

Max acceleration comes when you shift to maximize hp. I have an excel ss I wrote called "shiftpoints" where you can graphically see the best shift points. I'll send you a copy if you want. But for a hp curve like yours, increasing with rpm, you get the best acceleration by shifting at redline (6000rpm?) in each gear. For a turbo with a big torque peak, and a falling hp curve, you may well need to shift before redline.

IMHO, too much emphisis is placed on the torque curve. Torque is work done (ft-lbs), while Hp is work done per minute (ft-lbs)/min . In other words, hp is how fast you get the work done.

Did you keep the rear bar soft?

.

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Last edited by KevinK2; 04-18-2014 at 06:17 PM.
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post #12 of 23 (permalink) Old 04-18-2014, 06:37 PM Thread Starter
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Having a great weekend. I'd say the car is working pretty well. :-)

http://m.youtube.com/watch?v=qXGDTFs7Pxw
Did anyone notice the Lotus in the right-side fence at the entry to pit road at the end of lap 11 and 12? Had to be towed back to the pits with a broken rear end and some left rear body damage. Pretty sure it'll buff right out.

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Last edited by CanyonRider; 04-18-2014 at 06:44 PM.
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post #13 of 23 (permalink) Old 04-18-2014, 06:44 PM Thread Starter
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Originally Posted by KevinK2 View Post
Just a reminder that the peak torque is where you get the maximum HP/rpm ratio from the engine.

HP=TN/5250, T= (HP/N)x5250

Max acceleration comes when you shift to maximize hp. I have an excel ss I wrote called "shiftpoints" where you can graphically see the best shift points. I'll send you a copy if you want. But for a hp curve like yours, increasing with rpm, you get the best acceleration by shifting at redline (6000rpm?) in each gear. For a turbo with a big torque peak, and a falling hp curve, you may well need to shift before redline.

IMHO, too much emphisis is placed on the torque curve. Torque is work done (ft-lbs), while Hp is work done per minute (ft-lbs)/min . In other words, hp is how fast you get the work done.

Did you keep the rear bar soft?

.
I started with the RSB full soft and then did a session with it in the middle. The car got very loose in T5a and T21 so I put it back to full soft. I really liked it there. I could get it to rotate well in T5a and by keeping some throttle on I could keep the rear planted in T21.

Looking forward to going back in Sept. I was short shifting this time, but with a new clutch I'm going to try some different shift points.
Thanks,
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post #14 of 23 (permalink) Old 04-18-2014, 08:16 PM
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Originally Posted by CanyonRider View Post
I've been thinking about this myself. My current 275/35/18s are 25.58"dia compared to the OEM 215/50/17s at 25.46"dia that the ECU thinks I have. It seems like the speedo should be about right and I should be able to get to 120 before the ECU starts shutting me down. I think the bigger issue is gearing. Being a frugal family sedan, 4th and 5th are over-drive ....

.... Doing some quick math (assuming 6500rpm shifting and 25.5"dia tires), my theoretical top speed in each gear should be:

1st - 38
2nd - 65
3rd - 95
4th - 126
5th - 163

Unfortunately, I seem to be topping out at around 112mph. I think a couple of things are going on: I'm short shifting to 5th because the revs are building very slowly in 4th and I'm thinking "this isn't being nice to the engine".

Remember from my Dyno run, peak torque occurs at about 4950rpm and drops pretty linearly from there to redline. So the revs are trying to build as the torque is dropping resulting in the car not gaining much speed at the top end of 4th gear.


The last time I was at VIR, I was on 245/35/18s at 24.75"dia and running the numbers again we get:

Max Speed:
1st - 37
2nd - 63
3rd - 92
4th - 122
5th - 158

It seemed like with the shorter tire I was getting 2-3mph more on the straight - I assume due to the lower overall gearing.

Not sure what my next step is. Given the power and weight of this car, I should be able to get to 120 easily.

CR
I could be wrong, but it looks like you are doing a lot of short shifting, based on watching the video when you had open track. Going from t17 to t1, you shift from 3-4 at 75mph, then 4-5 at 100mph. From the speed vs gear table with 6500 rpm shifts, thats 5300 rpms at both shift points, and 4100 rpm when you engaged 5th ... with only ~140 hp at that point.

Let me know what i'm missing here. It would be helpful if you could list the gear you are in at each turn. That's better than me guessing. Also, verify if the indicated speeds are accurate. Need to resolve this before deciding on a 4 speed or 5.

Are there any Mazda/Ford 5 speeds with better gearing?

.

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post #15 of 23 (permalink) Old 04-18-2014, 08:21 PM
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Quote:
Originally Posted by CanyonRider View Post
Did anyone notice the Lotus in the right-side fence at the entry to pit road at the end of lap 11 and 12? Had to be towed back to the pits with a broken rear end and some left rear body damage. Pretty sure it'll buff right out.

CR
I'll look for it. The years when I tracked my Triumph (trip webers et al), I never saw another British car make it through the day without breaking down!

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post #16 of 23 (permalink) Old 04-19-2014, 08:10 AM Thread Starter
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Originally Posted by KevinK2 View Post
I could be wrong, but it looks like you are doing a lot of short shifting, based on watching the video when you had open track. Going from t17 to t1, you shift from 3-4 at 75mph, then 4-5 at 100mph. From the speed vs gear table with 6500 rpm shifts, thats 5300 rpms at both shift points, and 4100 rpm when you engaged 5th ... with only ~140 hp at that point.

Let me know what i'm missing here. It would be helpful if you could list the gear you are in at each turn. That's better than me guessing. Also, verify if the indicated speeds are accurate. Need to resolve this before deciding on a 4 speed or 5.

Are there any Mazda/Ford 5 speeds with better gearing?

.
Here's a session from Sunday. Couple of things to note:
  1. There is a substantial delay in the speedo (1-2sec). My sampling rate is fairly slow - I'll be fixing this before the next event.
  2. I added g-force values and tranny gear to telemetry.
  3. Next event I will have the tach and throttle position input to my telemetry.
  4. I'm definitely short shifting to 5th, but not to 4th.
  5. Listen late in the session - @24min mark the clutch slips badly as I shift to forth. It seemed to slip more as it got hot.
  6. Notice in 25min I was not passed by a single car.
  7. Notice the first car I pass (Pewter Vette) I pass again on lap 12. I must have been running 10sec faster/lap to catch him again.
  8. You may notice I reach for the shifter at T14 before heading down hill. This is muscle memory reflex. When I run the full course at VIR, I down shift to third at this point. On North course, I'm already in third. Doh!

https://www.youtube.com/watch?v=vxhWsCi5V-M

As for alternate trannys and gear sets, I understand the Australian Mondeo uses the 3.0AJ with a different tranny that has a more track friendly gear set and final drive. Any Aussie friends wanna help me out?

CR

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post #17 of 23 (permalink) Old 04-22-2014, 08:00 PM
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Here's a session from Sunday. Couple of things to note:

I'm definitely short shifting to 5th, but not to 4th.



CR
I was watching you exiting out of T17, and on lap 4 at 8:23. It seems like you shift from 3rd at 80mph at that time, as you did on another clean lap. This time, however, you skipped 4th and engaged 5th.

But if at 80mph in 3rd, the rpm is 80*6500/95 = 5500 rpm. Sounds a bit short ?

Speed in Gear at 6500 rpm

1st - 38
2nd - 65
3rd - 95
4th - 126
5th - 163

It appears the dyno curve ends at 6000, and with a good clutch you considered 6500 shifts. Do you know what the torque or hp is at that rpm?
I'd like to run my shift-points calculator.

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post #18 of 23 (permalink) Old 04-23-2014, 02:41 PM Thread Starter
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I was watching you exiting out of T17, and on lap 4 at 8:23. It seems like you shift from 3rd at 80mph at that time, as you did on another clean lap. This time, however, you skipped 4th and engaged 5th.

But if at 80mph in 3rd, the rpm is 80*6500/95 = 5500 rpm. Sounds a bit short ?

Speed in Gear at 6500 rpm

1st - 38
2nd - 65
3rd - 95
4th - 126
5th - 163

It appears the dyno curve ends at 6000, and with a good clutch you considered 6500 shifts. Do you know what the torque or hp is at that rpm?
I'd like to run my shift-points calculator.

.
Yeah, a couple times when there was no one around me, I shifted from 3rd to 5th and just cruised down the front stretch - trying to save the clutch a bit.

You really can't go by the speed in the telemetry - the sampling rate is too slow.

Here's raw video of my last session of the last day. The sky was overcast so you can actually see the tach. 4000rpm is at 12 o'clock. 6500 redline is at 3 o'clock. Most 3-4 shifts are above 6000, most 4-5 shifts are near 6000.

Also, notice how much the oil pressure jumps around - wow!

Mazda6 @ Virginia Intl Raceway April 6, 2014 - YouTube

Finally, notice at 15:15 there is coolant on the track ( a car blew a radiator hose) - it can be clearly seen in the video although I didn't notice it in real time. It may not look dramatic, but when the car slid there unexpectedly it provided a little extra pucker.

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post #19 of 23 (permalink) Old 04-23-2014, 08:31 PM Thread Starter
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Here's raw video of my last session of the last day. The sky was overcast so you can actually see the tach.
Hmmmm - apparently not. On my computer it is easy to see the gauges, but after uploading to Youtube - not so much. Bummer!

CR

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post #20 of 23 (permalink) Old 05-15-2014, 09:29 PM
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.... Finally, notice at 15:15 there is coolant on the track ( a car blew a radiator hose) - it can be clearly seen in the video although I didn't notice it in real time. It may not look dramatic, but when the car slid there unexpectedly it provided a little extra pucker.
The pavement on Turn 7 on the big track at Summit Point is not visible as you approach from Turn 6, and I always took it flat out in 4th gear in my 924 Turbo, at about 80 mph.

Summit Point Raceway - Trackpedia

Someone had gone off course and sprayed dirt all over Turn 7, and when I hit it with most all my weight on the outside tires, the back end came around and with quick countersteer I was going sideways and scrubbed off a lot of speed. Another pucker moment.

But I had help in saving it .. practice on a wet skid circle 2 hrs before, and the high polar moment of inertial of the car with the transaxle in the rear, which slowed down the partial spin.

.

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