Shifting in the POWER BAND

[MothAngel]

When should i be shifting gears to keep the car in the power band.  Also does the fact that it redlines at 9000 change this based on conventional manual trans.

thanks in advance

[clive]

Hi and Welcome to MRC.

From memory peak power is produced at 6700 which means this is it\'s strongest area, so by letting the revs drop off to this area you may find the car pulls stronger and therefore accelerates harder from this point on.

It could be that you find this more effective than just "buzzing"
it high in the gears, be interesting to hear your findings.

Hope this helps

[iaint]

From my understanding of how gearing works the optimal shift point is different for each gear.

Whilst the engine produces peak power at a certain range of revs the gear you\'re in will determine how the torque is applied to the wheels - i.e. you get much more torque per turn of the wheels in 1st than in 5th.

You\'d need a dyno sheet (and calculator) to work out where the best \'usable\' power band is - you want to keep it wide enough so that you get while between shifts and also want to keep it somewhere close to peak power.

If you decide that usable is 85% of peak power you\'ll end up with one range (maybe 4800-7500 rpm), if you decide 80% then it\'ll be bigger (e.g. 4400-7800) and using 90% might be 6000-7100rpm.  The trade-off is power v time to change gears...

I think the \'usable\' range will be wider in lower gears then higher ones due to the torque availability...

Iain

[zevans]

I was gonna post and ask if anyone had a dyno for an RX8 hi-power yet - if so drop me an email and I\'ll work out the shift points...

Clive, it\'s not always just after peak power - it depends on how quickly the torque drops off after that point - ie the shape of the curve as well as the size of it. It\'s sometimes better to hang on in a lower gear so that you drop into the next gear higher up the curve. (I expect NA rotarys fall into this category because you don\'t have a lot of torque at the bottom of the range.)

Changing gear loses you about 20% of torque at the wheels (= genuine oomph), so you change at the point where you will regain at least 20% of engine torque by doing so.

Had a quick look at the ratios and it looks to me like the 5-speed has been geared for economy (har har) and driveability, and the 6-speed has been geared for proper driving. :hyper: In fact the different gearing probably makes more difference than the different engine map!

I got the impression on my test drive that you\'d never ever use 5th and 6th driving hard - 4th seemed like it would keep going until well over a ton...

[Leeman]

Originally posted by zevans

I got the impression on my test drive that you\'d never ever use 5th and 6th driving hard - 4th seemed like it would keep going until well over a ton...

.......So does 3rd ........

But seriously, when booting around (as this car seems to thrive on being driven hard).....5th and 6th rarely get called upon.

[Glenn Butcher]

Originally posted by MothAngel
When should i be shifting gears to keep the car in the power band.  Also does the fact that it redlines at 9000 change this based on conventional manual trans.

thanks in advance

Not sure if I understand the question - do you mean when driving hard?  

If I was driving the car (manual) on a circuit I would be shifting just before the 9,400rpm limiter.  This way when pulling the next gear it would drop back to the point of most power - so lets say if the engine makes 240hp at 7,000rpm or thereabouts that power would pretty much stay flat on the power curve to the 9,400rpm.  So going through the gears, the engine won\'t drop past (say 6,500rpm).

If you are talking about driving around on the street, and always wanting to be in the power area of the engine.  Then simply keep the revs above the 4,000-5,000rpm mark in 2nd, 3rd (depending on speed) - of course this won\'t be great for your fuel bill.

I have an Auto RX-8, it is a 4speed auto. If I want to ensure I\'ve got power when I want, I have to keep it up in the revs (that is what na/non-turbo rotaries are all about ).  So most of the time around the city I\'m in 2nd in the auto, but again isn\'t great for fuel - hence if I leave it in drive it would normally go to 3rd and 4th in the auto, depending on speed etc.

[zevans]

Originally posted by Leeman
.......So does 3rd ........

LOL

Test drive was in the wet and there\'s only so much a salesman will put up with.

[tsh]

Is a drop in power between 8000 and 9000 normal, or was my demo car a bit broken? It felt a bit slower than the TII, but that might have been just cause it was a bit smoother! Gear changes seemed to come up very quickly with the 6 speed box!

Sean

[MothAngel]

thanks guys this helps out  very much.  I just got mine today; tit. Gray w/ manual trany

[clive]

Originally posted by gbutcher



 If I want to ensure I\'ve got power when I want, I have to keep it up in the revs (that is what na/non-turbo rotaries are all about ).  

l gotta agree with that statement

I had an EGI ( N/A Gen2) for some three years, and yes you have to work it or it used to feel a little dead:) ,

The reason l put about buzzing is that from experiance if you hang on to the gears too long and stay really high in the rev range l used to kinda feel l was looseing forward acceleration,

l did note that at one stage RX-8 Owners were experianceing a power drop off, but lt sounded more like they were finding a slight drop before the real torque kicked in .

Which brings it back to the fact that you need to "work"  a N/A Rotary a little to get it up n going, and that\'s real fun and of course you get that wonderfull N/A Rotary sound    

This is why l look forward to hearing what a few different RX-8 owners find.

[BlueAdept]

Damn that rev limiter...

The published peak power for the UK hi-power car is 8200rpm... so when driving hard, I normally try to shift at 9, (Which normally means a little more than 9)... that way, you\'re back as high up the power band as possible after the shift...

There is obviously enough power there, but it seems to let rip at 7200 or so, giving you somthing like a 2000 rpm band to try and stay in if you\'re going for broke...

That\'s my experience anyway... comments?

[Glenn Butcher]

Hi BlueAdept!

Do you know what the drop in revs is when you go through the gearbox?

I think the hi power manual keeps making power up to the 9500rpm mark, you can rev it to that so that when you pull the next gear it is pretty much in or around that 8200rpm mark.  Mazda wouldn\'t have let you have that many revs if it wasn\'t beneficial

Another reason why I say this is because of this video:

http://www.mymazdarotary.com/rx-8_videos/time-attack.avi 17MB (Right click and save target as).

This is a VERY good driver, he is using all of the rpms in the engine - if he is doing this then it must be making power up there and it must help to put it at the correct revs when pulling the next gear.

[BlueAdept]

I\'ll have to go out and try later... I think it drops about 2000 rpm depending on which gear you\'re shifting to/from...

Either way, the rev limiter is at 9400 and by aiming for around 9000 I normally get it in just before that... there\'s certainly power up there, and it doesn\'t drop off fast at all over the peak... although as I said, the peak is 8200...

If you\'re really hauling then you wanna be in that zone between 7000 and 9200 where that wonderful rotary battlecry can be heard by everyone around.

[BlueAdept]

Gears and RPM\'s...

Well, given these numbers gleaned from the US forum,

Rear wheels = 225 45 18
 Diff - 4.1
 1st - 4.02
 2nd - 2.46
 3rd - 1.77
 4th - 1.33
 5th - 1.08
 6th - 0.9

And a calculator, I get this... (Sorry about formatting, It looked good in Excel.

Speed
2000
3000
4000
5000
6000
7000
8000
9000
Rev drop on shift


1st
9
13.5
18
22.5
27
31.5
36
40.5
3570


2nd
14.7
22.1
29.4
36.8
44.1
51.5
58.9
66.2
2580


3rd
20.5
30.7
40.9
51.1
61.4
71.6
81.8
92
2287


4th
27.2
40.8
54.4
68
81.7
95.3
108.9
122.5
1729


5th
33.5
50.3
67
83.8
100.6
117.3
134.1
150.8
1533


6th
40.2
60.3
80.4
100.6
120.7
140.8
160.9
181
NA

[BlueAdept]

Note,

On a second look, those ratio\'s were "preliminary"... although I can confirm that they are pretty accurate... at least 1, 2 and 6 are spot on from my observations..