SP or SE

[Daz]

Dyno day we had a while ago.

My stock SE...106kw.

Dazs' stock SP...121kw.

Same dyno,same day.

My SP this morning, same dyno different day, one piece of hose, 160.5kw.

Also, there was another stock SP on that same day running 130rwkw.

[Okibi]

I just found an old \"reprinted from Wheels Magazine February 2002\" SP vs S2000 article.

They price the SP at $55,540 or $58,040 with aircon

\"The turbos only hiccup (guarenteed to be gone from the production version) is a momentary heart-skip when you back off the gas after being hard into it\"



Weight 1,119kg
Power to weight:134/kW/tonne (That makes it 119.7 kw?)
Compression ratio:10.0
Power 150kW/6800rpm (at the engine I guess?)
Torque:280Nm/4600rpm
Specific output: 82kW/litre
Gear Ratios:3.76/2.27/1.65/1.26/1.00/0.84
Differential Ration:3.64
Turns Lock-to-lock: 2.7
Turning Circle:9.2m

Fuel Consumption: Average 11.0L/100km

(Oran Park, dry temperature:21\"C Driver: Mike McCarthy)
Standing-start acceleration:
0-60 km/h:3.2sec
0-80 km/h:4.6sec
0-100 km/h:6.5sec
0-120 km/h:8.7sec
0-400 m/h:14.6 @ 157km/h

[Garry]

\"The turbos only hiccup (guarenteed to be gone from the production version) \"

They lied.

[Bevan]

So why did Mazda claim 121kw at the wheels?

Na, they claimed 121kw at the flywheel.

[Garry]

Mazda seems to have untold trouble reading dyno charts. They overquoted the power figures on the RX8 and the NB8B and it cost them a lot of money on buy backs and compensation in the US. Maybe they underquoted on the SE just in case they read the graphs wrong again?

[Bevan]

Maybe they underquoted on the SE just in case they read the graphs wrong again?

Maybe. I can't imagine how it only loses 13-15kw in the drivetrain. It's normally a bit higher than that...

[Casey]

My typo. on the 121rwkw ..........

But the obvious consensus is that the SE is 108kw at the wheels and a very suspect 121 kw at the flywheel. The USA Mazdaspeed has the same approx. 148rwhp or 110rwkw (DynoDynamics in all cases). The same car is rated at 178 flywheel hp or 133 kw. No doubt in my mind that Mazda has made another deliberate error.

Moving on to the SP (with a very similar drivetrain), it should be losing roughly 133 - 110kw i.e. 23kw. This would mean 150 - 23 = 127rwkw minimum or 157 - 23 = 134rwkw (depending which original press you read).

Since the SE is definitely producing the figures found by so many club members, can we then assume that the SP should be producing in the order of a stock 130 rwkw, not the 120 rwkw? The acceleration times would support this, any comments (of course you fool).

You're right Boris, there is no desputing the massive difference in acceleration times showing that the real world power difference is bigger then the dyno figures suggest.

The most logical explaination of the contracting of the comparitive dyno figures is that the SE has a lower final drive then all other NB8B/Cs, SP included. That means if both an SP and an SE were dyno'd in 4th gear (which is an identical gearbox ratio) and the dyno operator didn't compensate for the actual gearing presented at the rollers, the SE would read a comparitively higher power figure then the SP (or any other NB8B/C).

Someone who has access to a gearing spreadsheet could show the differences, and the SE also has a bigger OD at the tyre treads which will also affect a rolling road dyno figure to its advantage I suspect (I'm basing this on the reason why Massy Furguson's have such tall rear tyres to gain more tractive effort ).

I have access to an engine dyno - anyone game to take out their SE and SP engines for a flywheel power comparsion?

[Alf]

SE also has a bigger OD at the tyre treads which will also affect a rolling road dyno figure to its advantage I suspect (I'm basing this on the reason why Massy Furguson's have such tall rear tyres to gain more tractive effort ).

Is the because you're talking through your here? Can't have it both ways, either lower gearing gives you mechanical advantage or taller tyres do.

Cheers,
Alf

[SPy vs. SPy]

SE also has a bigger OD at the tyre treads which will also affect a rolling road dyno figure to its advantage I suspect (I'm basing this on the reason why Massy Furguson's have such tall rear tyres to gain more tractive effort ).

Is the because you're talking through your here? Can't have it both ways, either lower gearing gives you mechanical advantage or taller tyres do.

Cheers,
Alf

and in this case, the wimpy SE may have both.

a higher final drive should be offset by bigger tyres, ie the rear wheels rotate less often (fd ratio) but travel a further distance (circumferece ie bigger tyres) therefore if the bigger tyres and higher FD ratio combined are less than a stock car, then there's a mechanical advantage to the SE.

Ultimately for each engine revolution the cars should move forward the same distance, otherwise this needs to be offset in the power calculations.

[Casey]

SE also has a bigger OD at the tyre treads which will also affect a rolling road dyno figure to its advantage I suspect (I'm basing this on the reason why Massy Furguson's have such tall rear tyres to gain more tractive effort ).

Is the because you're talking through your here? Can't have it both ways, either lower gearing gives you mechanical advantage or taller tyres do.

Cheers,
Alf

Sorry Alf - just my tiny brain trying to work through this. I was thinking that the slightly taller tyres may lower the final drive even further (hence my embarrsing reference to a farm tractor), but you are saying the opposite. I wasn't sure on this point, so I'll take your position as correct. In any case, the SE has a lower overall fianl drive as it's in gear speeds (road) are lower per engine revolution then a normal NB8B/C or SP.

[Techno]

At the 2005 dyno day in Victoria an SE put out 94-96 RWKW.

The SP put out 118RWKW.

But that is only half of the picture. You need to look at the area under the chart line and the SP is a clear winner.

BTW are you measuring in mechanical or metric output. Metric is around 98.6% of mechaniical.

[Alf]

In any case, the SE has a lower overall fianl drive as it's in gear speeds (road) are lower per engine revolution then a normal NB8B/C or SP.

Do you have a source for this? Looks to me like the same gearbox ratios throughout the gears and same diff ratio. However, I'm only going by what I can find on the web. Certainly the Mazda Aus. site http://www.mazda.com.au/specifications_pl.asp?ID=51 gives the 2004 SE & standard manual ratios as identical (The only SP specs I could find were on autoweb, not exactly a reliable source. http://autoweb.drive.com.au/cms/A_54727/newsarticle.html

Perhaps you're getting confused by the lower top speeds in each gear of the SE. This is due to the rev limit

Let me say that my first dyno day is later this month, I've never been near one before, so am most likely also talking through my However, aren't dyno measurements usually taken at whatever gear gives 1:1 (or, as close to it) gearbox ratio, to reduce gearbox losses (i.e. 5th gear for six speed MX-5 gearboxes)?

This isn't meant at all to detract from the fact that the SP is more powerful than the SE, always has been.

[Alf]

In any case, the SE has a lower overall fianl drive as it's in gear speeds (road) are lower per engine revolution then a normal NB8B/C or SP.

Do you have a source for this? Looks to me like the same gearbox ratios throughout the gears and same diff ratio. However, I'm only going by what I can find on the web. Certainly the Mazda Aus. site http://www.mazda.com.au/specifications_pl.asp?ID=51 gives the 2004 SE & standard manual ratios as identical (The only SP specs I could find were on autoweb, not exactly a reliable source. http://autoweb.drive.com.au/cms/A_54727/newsarticle.html

Perhaps you're getting confused by the lower top speeds in each gear of the SE, due to the lower red line and rev limit?

Let me say that my first dyno day is later this month, I've never been near one before, so am most likely also talking through my However, aren't dyno measurements usually taken at whatever gear gives 1:1 (or, as close to it) gearbox ratio, to reduce gearbox losses (i.e. 5th gear for six speed MX-5 gearboxes)?

This isn't meant at all to detract from the fact that the stock SP is more powerful than the stock SE, always has been. Can't see much point in pretending that the difference is either less than or greater than what's measured.

As techno rightly points out reducing the dynamometer output to a single "peak power" figure is misleading, too. The difference in areas under the graph is more important. The fact that the SP can stay in a gear longer due to its higher rev limit is important in real life, too.

</rant>

Cheers,
Alf
(The older I get, the faster I was).

[Casey]

\\Perhaps you're getting confused by the lower top speeds in each gear of the SE, due to the lower red line and rev limit?

I remember reading it when the pre-production models were with the press and I'm sure it was in Mazda's pre-realease send out. At the time I though it was unfortunate that the SE suffered the double-whammy of both a lower rev limit and a lower final drive, let alone the loss of SVT.

Never trust Mazda Australia's web page to garnish useful information

Edit - you are right that the 1:1 gear is fifth, but the speeds at the roller are too high and dangerous to use this gear, so fourth is preferred by the dyno operators.

[Alf]

Well, had the car up on a Dyno Dynamics at Caulfield Jag with the boys today. Right after a stock SP.

Mine put out 102 rwkw, while the SP put out 112.

I'm a little sus that this SP might have read a bit low as it only reached 106 on its first run. The guy running the dyno said that the SPs were noticeably different from other turbo cars in that they generally reached higher power on the second run. My guess is that the car had been standing for a while after having been dríven a fair way and was suffering from heat soak during its first run. Who knows if it might have improved more on a third run.

My car, on the other hand drove virtually from the highway onto the dyno (about a 3 minute wait). My 2 runs were virtually identical at 102 and 102.5.

The real difference between the SE and the SP, though, was in the torque figures. The SE came in at 2400 N (I'm guessing this should be Nm as the Newton is not a measure of torque), if I remember correctly (with this soggy wine soaked blanc-mange I call a brain) the stock SP was over 3700 - on the second run. I might be getting it mixed up with one of the two modded SPs, though.

Oh yeah, these dyno operators didn't wimp out, all runs were in in 5th.
Cheers,
Alf