Mark_Z28

I just messed around today with my 03 with an original G-Tech Pro, which I bought when they first came out. I did one run and got a 7 sec 0-60, as fast as the MX5 in the magazine. Geuss I need to get serious and try it again.

DavidM

The Mazda makes more torque across most of its power band than the S2000 makes at it's peak

Hmmm, that does not sound right. MX5 is rated at 188Nm (peak) and the S2000 at 208Nm (peak). That is a 20Nm advantage to the S2000 at the peak.

Looking at the power F20c power/torque curve from Mugen (for a stock F20c), it shows that the S2000 has:
- Over 160Nm from 2,000rpm.
- Over 180Nm from 3,000rpm.
- Over 200Nm from 5,500rpm.
- Around 210Nm from 6,500rpm to 8,500rpm.

So unless the MX5 is seriously underrated, or there is a major difference in drivetrain losses, then the S2000 should have more torque than the MX5 anywhere above 3000mph. Not sure how much torque does the MX5 have below 3000rpm, but even there ther S2000 could/might have more torque.

So from what I gather, the S2000 should have at least 10% torque advantage practically enywhere/everywhere.

If the gearing is close, then your thinking seems correct.

I would think that the gearing not close and the S2000 will have ~10& shorter gearing compared tot he MX5. Also there's about 10% weight difference.

So if we were to go just by theory then we have:
1. ~10% more weight in the S2000.
2. ~10% more torque in the S2000.
3. ~10% shorter gearing in the S2000.

Does that mean that the S2000 would be quicker or slower than the MX5 when in the same gear and at low/lower revs? Would be great to know so if someone with the G'tech could roll off the line, then punch it from ~5kph onwards, and then publish the times then that would be great.

Thanks again for the info ideas so far.

ps. I'm only guessing at what the MX5's torque curve looks like, but going by the stats it'll have less than 188Nm everywhere but at the peak. 20% variation on torque over the usable rev-range is pretty standard for decent N/A engines these days.

smurf2k

Well, if we take those dynographs at face value, then the mx5 motor does produce more torque (more or less) from 3500rpm to redline

however, because it has a shorter redline, and i assume the cars are geared similarly that they reach the same max speed at redline, then the s2000 would have shorter gear ratio (higher multiplier), and ultimately produce more torque at the wheels on an MPH-by-MPH basis

would be lots more fun if i could test it in person though

ace123

i remember a post (street encounter?) where an s2000 owner was fooling around with an MX5 (pretty sure it was a new one). he ran his car right up to the start of VTEC and shifted right when the cams were switching over. he was neck and neck until he couldn't stop himself and let it wind all the way up. then he blew by.

don't we make about 160hp at 6k on ap2s? that's pretty close to the MX5, so it seems like they should be close until the MX5 shifts and the s2000 hits vtec.

RED MX5

Rather than looking at factory ratings I'm looking at actual dyno plots, which are posted above.

You don't have to guess about the MX5's torque curve; I posted a dyno plot in the post you're quoting. Just look at the plot and see for yourself.

Keep in mind that acceleration is a function of thrust and weight, and that thrust is a function of torque, gearing, and tire diameter. Look at the WHP curves above. The reason the S2000 makes more power is because the engine spins faster, and it makes a LOT more power than the MX5. Power tells you how quick and fast a car is. Torque only tells you how hard the engine twists the flywheel. A car that revs higher, usually has shorter gearing (numerically higher), so even though it may have less torque, the thrust and acceleration can stll be greater. Revs and gearing are as much of the power equation as displacement.

If somebody can get gearing and tire diameter info for the MX5, we can calculate the acceleration. The calculations will agree very closely with measurements made with a *properly calibrated* accelerometer. The problem with accelerometer measurements is that, like a dyno, they depend on accurate user calibration. Most dyno operators do a better job of calbrating their dyno than most Gtech users, so their results are more reliable. It doesn't matter whether you measure the acceleration with an accelerometer or with the roller on a dyno, becaue either way, the accuracy of the output is only as good as the input. GIGO.

The best way to calibrate accelerometers is to use a dyno plot. You measure acceleration, calculate WHP or TQ from the results, and compare to a dyno plot. If the curves don't match, either the dyno or the accelerometer calibration is off.
But the thing you need to realize is that the two are interchangable. With good inputs, they produce identical outputs.
Dyno's vary, but we even have correction factors for comparing readings between dynos.

Anyway, we have all the information we need to calculate the exact acceleration of the S2000, and all we need is gearing and tire info to do the same for the MX5.

-------------------------

However, I've got to ask; Why would anyone even care about comparing such vastly different engines?

RED MX5

[QUOTE=smurf2k,Mar 4 2008, 11:01 AM]Well, if we take those dynographs at face value, then the mx5 motor does produce more torque (more or less) from 3500rpm to redline

however, because it has a shorter redline, and i assume the cars are geared similarly that they reach the same max speed at redline, then the s2000 would have shorter gear ratio (higher multiplier), and ultimately produce more torque at the wheels on an MPH-by-MPH basis

would be lots more fun if i could test it in person though

RED MX5

Street encounters are always suspect. Back when my S2000 was bone stock I outran Tripper Cook's Skyline R33 GTR, which was making 400 WHP at the time. Obviously a 400 WHP Skyline is a lot quicker than a 187 WHP S2000, but I still pulled Tripper in second and third gear (after which he gave up). On the street the encounter is usually more a function of the driver than the car they're driving.

Funny about the MX5 encounter you describe though; My wife and I have done a few pulls putting her E320 Benz against my S2000, and it's exactly the way you describe the MX5 encounter. We're on the street, so I can't launch hard. As a result, I have to wait for VTEC. We pull side by side, dead even, in first gear, but only until I hit VTEC, then the little Honda just scoots away. LOL, of course the FI has changed that more than a little, but that's the way it was when my car was stock. Now I'm wondering how the MX5's acceleration compares to the E320.

RED MX5

BTW, in theory I'd expect the MX5 to produce more torque and power across most of its powerband. Here's why ...

The S2000 is "tuned" to make peak power at high revs. While VTEC allows the valve lift and timing to change, effectively changing a part of the tuning, there are other parts that do not change, including the intake and exhaust systems, both of which are tuned for maximum output at high revs. At lower revs the intake and exhaust tuning is less than optimal. The MX5, on the other hand, is fully optomized for operation at lower revs, so it makes more torque and power at lower revs. I really don't see how it could be otherwise, given that the two engines are of the same displacement and of very similar configurations.

DavidM

Rather than looking at factory ratings I'm looking at actual dyno plots, which are posted above.

Thanks RED MX5, but I don't think they are comparable. ie. each is probably using a different scaling factor (which is pretty normal for dynos). I find it hard to believe that the MX5 would be so underrated that it would have have ~15% more torque than an F20c... which is one of the best torque-per-liter engines in the world. Not even M3, GT3, or Ferrari engines produce anywhere that much more torque-per-liter.

It it were true then either either the MX5 is underated and has ~240Nm of torque (instead of factory claimed 188Nm), or F20c is way overated and has ~180Nm (instead of factory claimed 208Nm).

You don't have to guess about the MX5's torque curve; I posted a dyno plot in the post you're quoting. Just look at the plot and see for yourself

True. According to the plot the MX5 should have 188Nm between 4,000 and 5,000rpm and (up to) 20% less elsewhere. So S2000 should have more torque from 3000rpm onwards. Even at 3,000rpm S2000 should have ~15Nm more torque, which is a 10% advantage.

Most dyno operators do a better job of calibrating their dyno than most Gtech users

I don't know ... dyno numbers to me are pretty useless. Only the shapes of the curves there seems of use as I've seen massive differences in dyno numbers even for the same car on the same dyno and at the same day. Also it's not unusual to have 2 same make cars producing 2 very different power/torque figures on the dyno, only for the one with the lower numbers to be quicker then accelerating.

To me, much more 'real world' results are the acceleration numbers. As long as the G'tech numbers are validated/repeated a few times, then they should be pretty close (in particular with the newer G'techs). Would love to see some G'tech numbers to balance the info here.

all we need is gearing and tire info to do the same for the MX5.

I can provide that ...
http://www.mazda.com.au/Models/Current%20m...ifications.aspx

Gearing:
1st = 3.709
2nd = 2.190
3rd = 1.536
4th = 1.177
5th = 1.000
6th = 0.832
reverse = 3.603
finaldrive = 3.727

Tyres are 205/45/17.

Weight is 1106kg (without driver).

However, I've got to ask; Why would anyone even care about comparing such vastly different engines?

It's not the engines that I'm interested in comparing but the cars. ie. Is an S2000 as quick in day to day stop-start driving as an 2.0L MX5? Or it is quicker even in those circumstances (ie. rolling of the lights off idle and accelerating to ~40kph)?

If it's a pull from a standstill or slow roll, then any driver worth his salt is going to use the clutch and a launch of sorts to get into the power band.

I dissagree with that when talking on the road, in day-to-day driving. ie. on a way to work you may stop/start 50 times, and you're not going to be reving/launching/'riding clutch for each of those starts. So what happens is one has to 'climb' through the entire rev-range to get into the powerband.

No question as to what'll happen once you're in the powerband, but most of the time you get there by climbing through the entire revrange.

Also, I'm not interested in comparing drivers here, but simplty the 2 cars.

Please keep in the input / info coming ;-)

I'd expect the MX5 to produce more torque and power across most of its powerband.

F20c has very flat and high torque output. It has a pretty flat torque between 3000 and 6000rpm, then it steps up and is flat from 6500rpm onwars. Still, even between 3000 and 6000rpm, F20c produces 90% of it's peak torque. And also even between 3000 and 6000rpm it produces more torque than most other 2.0L engines at their peak.

F20c torque curve is very flat and very high (compared to other 2.0L engines). I can't think of other 2.0L engine that has as much torque as F20c (and that is across the rev range) as usually there's more like 15 to 20% torque drop off away from the torque peak. The dyno plot posted earlier indicates that MX5 has ~20% torque drop off at 3000rpm.

I remember a post (street encounter?) where an s2000 owner was fooling around with an MX5 (pretty sure it was a new one). he ran his car right up to the start of VTEC and shifted right when the cams were switching over. he was neck and neck until he couldn't stop himself and let it wind all the way up. then he blew by.

Any chance of posting a link?

ace123

i think this was it. less useful than i thought though.

https://www.s2ki.com/forums/index.php?showt...&#entry11575091