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Discussion Starter #1
I went out to the Silvia NSW Dyno Night and I put my car up on the rollers.

The first question everyone asked when my car went up was "What are those tyres?", followed by annoyance as the guys had to pick all the stones that were stuck onto my tyres.

Thanks to the guys at UniGroup not knowing that my car has 6 gears, they did the first two runs in 4th. So my last run, in the right gear, was with a of heat soak.

At any rate, I put down 167.1kW, with a power curve that's basically linear and a torque curve that's dead flat.

I got pipped by a Cortina with a Windsor 302 (which pulled 168kW) to not make "Top Other" (it was a Silvia night, after all) but the only car that got close to mine had 1.5L of displacement (and more modification) to get an extra kW. Had I been in the right gear and no heat soak for the first run, perhaps I could have carried off the win.
 

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Discussion Starter #2
Pictures and scan of dyno graph to come.
 

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What did the S14 and S15 200SXs pull on that dyno (if there were any)?

ps. Congrats on the 'almost' win ;-)
 

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167.1 rwkw on 4th gear is good.

Mine got about 153 rwkw on 4th gear :( with unichip only get 164rwkw on 4th gear :(

Do you think all because the wheels diameter might effect the power read?

what other performance mod you had in the car?
 

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Discussion Starter #5
Here are the results (scroll to bottom). The S14a that pulled the top figure is an absolute monster. I know the previous owner (who did all the work) and he knows a lot about SR20DETs, is meticulous, and spent a lot on the vehicle.

As you can see, though, Silvias making 170rwkW+ are common these days. A few years ago, making anywhere near that was a good figure.


The Dyno Dyamics dynos are meant to compensate for air temp, pressure, tyres and the rest. It can only make guesstimates on how much to correct for, of course.

The mods I have on the car are the HiTech and Popcharger.
 

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Do you think all because the wheels diameter might effect the power read?

Different dynos ... you can't really compare a reading from one dyno to another. I've seen as much as 40kW variation betwen dynoes. Compare your and Scathing's trap-speed from the 400m runs, and you'll see that there's not much difference.

Not only that, but it's not unusual to go tothe same dyno on 2 different days, and produce readings 5kW greater/smaller than before. Dynos are designed for tuning of cars and measuring gains/losses with mods ... but for that you need to be doing it all yourself, and going to the same dyno.

ps. Do you have a different wheel/tyre diameter at the moment? I though that you were running the same overal diameter as OME?
 

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Thanks for the results sheet ... I'm trying to find some 'benchmark' cars in there that one car draw a baseline from. Best I could find are:

- S12 Gazelle (stock, 108kW) = 60kW
- XT6-T (stock, 240kW) = 221.1kW
- Commodore VT SS (stock, 179kW) = 150.2kW

Not sure which S15 (or S14) 200SXs were stock as they all seem modified. The lowest reading for an S15 I found was 137.1kW, but I it does not list the mods or whther it is stock.

Not sure if these numbers can give us any baseline as I can't see any pattern or relation between these numbers.
 

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There is now way a XR6t is 240kw at the crank stock.... why lie about the power? :headshake:


Maybe it'll just confirm how llama the xr8 is..tehehehe :lame:
 

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Originally posted by DavidM@Nov 14 2004, 07:46 PM
Do you think all because the wheels diameter might effect the power read?

Different dynos ... you can't really compare a reading from one dyno to another. I've seen as much as 40kW variation betwen dynoes. Compare your and Scathing's trap-speed from the 400m runs, and you'll see that there's not much difference.

Not only that, but it's not unusual to go tothe same dyno on 2 different days, and produce readings 5kW greater/smaller than before. Dynos are designed for tuning of cars and measuring gains/losses with mods ... but for that you need to be doing it all yourself, and going to the same dyno.

ps. Do you have a different wheel/tyre diameter at the moment? I though that you were running the same overal diameter as OME?

My car has a different diameter of wheels than the OEM.

19"X8.5 245/40
19"X9.5 275/40
 

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db350z, shouldn't you be using 35 profile tires and not 40?
 

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db350Z - I think that the 167kW was recorded in 5th gear on the last run, not 4th gear.

Zuffy - the XR6T may make more than the 240kW rated at the crank, but that still doesn't make it quick. Or alternatively, the car is not stock as it states in the table.
 

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19"X9.5 275/40

Yeah, why not 35 profile which is a really good match? As it is, the 275/45/19 at the back will produce 4% speedo error. That means when the speedo is showing 100kph, you're really doing 104kph.

Also, it can have an effect on the dyno and if the operator did not take the tyres into account, then it could have read too low.

My car has a different diameter of wheels than the OEM. ... yeah i think it's 35

In thatcase your rears have the same diameter as the OME 245/45/18 and therefore you have no speedo error (differing from EME) and also it should not really effect the dyno reading.
 

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does wheel diameter affect the dyno?

Wheel diameter does not necesarily effect anything ... it's the tyre diameter that may affect a fair few things (including dyno figures).

So you can keep your OME wheels, but put a different 'height' tyre on them and you will affect a lot of things like the speedo reading, oddometer, gearing and possibly even the dyno reading (unless it is set with your tyre specs).

On the other hand you can get different size rims, and then tyres that will have the tyre diameter exactly the same as OME, and your speedo, oddometer, gearing and dyno readings will be the same as they would be with OME wheels/tyres.
 

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David - If I understand you, the car will give different dyno figures on different circumferences (?).

If that's so, then gearing must also affect the readings ?

Will 3rd read higher? than 4th?

If so, how's different cars/models get compensated for in a dyno shootout/comparison?

All a bloody mystery to me!

FRIZZLE again.
 

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Yes gearing affects the dyno readings. I do not think dyno operators take gear ratio into comparison during a dyno comparison, apart from chosng the gear ratio closest to 1:1. In our case its 5th gear. A 3rd gear dyno pull should read higher than a 5th gear as its gearing is higher. A higher number multiplied by the same amount of engine power will result in a higher reading.
 

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David - If I understand you, the car will give different dyno figures on different circumferences (?)

Yes.

If that's so, then gearing must also affect the readings?

Yes, and so does the tyre pressues as they can change the tyre diameter.

Will 3rd read higher? than 4th?

Yes, but the readings between different gears are not that hugely different (actually I'm not sure why they are different?). We're talking about 10kW difference in the reading, while in truth the power to the ground between the 3rd and 5th gear is significant ... like 60% difference if I'm not mistaken.

If so, how's different cars/models get compensated for in a dyno shootout/comparison?

I'm no expert on dynos, let alone the 'shootout mode', but I'll say that the readings between 2 different dynos are not really comparable even if both are in the 'shootout mode'. They might be in the same ball-park, but considering that every kW counts, 10 - 20kW variation does not make for a good comparision. Best thing between twodynos is to find a 'benchmark' figure that will tellyou the variation between the dynos. ie. if dyno A reads a stock '04 WRX at 115kW, and dyno B reads it at 140kW, then we know that there 25kW difference between the dynos, and you 'should' be able to use that to compare car dynoed on one dyno to a car dynoed on the other dyno. Though, I'd take all this as approximations, and that's all.

Here is what I pressume about dynos:
- dyno will read the exact speed that the car will reachin any gear ... and that is no matter what the car is. Afterall, it measures the tyres spin the dyno rollers.
- It needs to know your gearing ... or at least the final drive if you pressume that every car has a gear 1:1 ratio. I pressume that this is something that is downloded in the software and they have this info for every car. Same goes for the cut-out.
- From gearing and speed it should be able to figure out your tyre diamter.
- I don't see why the dyno would not have archives of all the gear-ratios and if that was the case, then it would not make any (significant) difference to what gear you're running in as it would be able to work it out and hence compenstate the figures for that.
- Though, dynoing in a 'taller' gear will produce 'smoother' and more accurate reading just due to the smoother power delivery. Lower gears are more likely to produce 'slip' on the dyno.
- dynos read the ambient temperature as well as humidity and compenstate the figures accordingly.

Last of all, and most importantly, as far as I know, dynos do not measure acual power, but lots other things from which it then calculates a figure that 'looks like' power. This calculation is based on the reading and all the figures that are stored (or punched in) the dyno. Not only that, but then it will scale this number by an arbitary constant just to print a value that looks kind of in the ballpark.

Therefore the figure that you see onthe dyno is not really related to the power of the engine ie. you read 160kW, and hence pressume that there are 40kW of drive-train losses. That pressumpion is not correct. Also the figures are scaled by a bunch of constants that vary from dyno to dyno (the shootout mode tries to standardize these, but I don't know how strong this standard is from dyno to dyno).

So the best thing you get out of a dyno is the shape of your power curve. And if you go back after changing something, then the dyno should tell you what difference it made. Also, if you bring bunch same make cars there, then it should show you the differences between them. Last of all, if you bring bunch of different cars toone dyno, and that dyno has all the gear and tyre specs for each car in it's software, then you should be able to compare the figures between the cars.

ps. I would not take the above as gosspell, as I'm making a lot of pressumptions ... I'd love someone know knows about this kindof stuff to chime in.
 

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Discussion Starter #20
Like David, I see dynos as a tuning tool. In the end, its just a gauge. Just like your oil pressure, or temperature gauges. It doesn't make the car go faster in any respect. While its good to get the readouts for these things if your car's not running properly, since it can give you warning of impending failure, should everything be hunky-dory you really don't need to know the outputs at all.

The power figure itself doesn't mean anything - the only useful information you get from a dyno is the shape of your torque curve (which is all the rollers measure. Power = torque x RPM x constant, so that's how the power figure is determined). If you have a turbo car, then plotting boost and your A/F ratio is good too.

The finite number you make is borderline meaningless. Aside from the various environmental factors (ambient temperature, humidity, air pressure, etc) that the "shootout mode" is meant to compensate for, to give you a comparable figure with other vehicles, it still can't be 100% accurate. Different days will give you different results. Different dynos will too.

It also doesn't relate directly to how it runs on the road. A big dyno figure might just mean peaky power delivery, which is not the fastest car. Also, being stationary, you're more likely to get heat soak and other factors that aren't the same as when you're rolling.

I put it up there to have a look at the curve, although I should have dyno'ed it in stock form to see the differences. I won't be doing any other "power" mods until the warranty expires, so this one was more for a bit of fun than anything.
 
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