Tag: horsepower

Veloster N Engine Modes Dyno Tested

The Veloster N has three power levels and three exhaust sound settings, which you can customize to your liking. There is also an economy mode that limits boost pressure and should provide better fuel milage. But how much do these modes differ in power output?

The N Custom mode shows the engine and exhaust sound have three settings each.

I wanted to know, so I went to Overdrive Automotive in Johnson City and had them dyno my car. (Side note, if you are in Central or Southern NY, I would highly recommend Overdrive for tuning your Megasquirt or whatever, they know Miatas really well.)

The rollers are at ground level, so the car is lifted up for dyno testing.

I didn’t test all the modes, figuring it was most important to get the data for the lowest and highest power settings.

  • Eco: This mode is supposed to limit boost pressure to 6-7 psi and return better fuel milage. I believe this is a separate setting than the lowest engine mode available in N Custom mode, so I selected this mode from the preset modes on the steering wheel button.
  • Normal: This is the lowest setting in N Custom mode, and probably the same as choosing Normal mode from the presets. This is the mode I use for all street driving (or when I’m on track and forget to turn on N Custom).
  • Sport: I didn’t test the tune in between Normal and Sport+. I didn’t test the middle exhaust setting either.
  • Sport+: This is the highest engine setting, which I initially set with the quietest exhaust, because I don’t like pops and bangs or loud pipes.
  • Sport+ with exhaust: Same as above, but with the exhaust in the loudest setting. This mode has the burble tune and exhaust valve open, and should show the highest power output.

Note that this test was done on a DynoJet, and so all readings are corrected for elevation and temperature. The engine is bone stock and has about 4000 miles on it (it was replaced once under warranty).

Shockingly, the dyno recorded virtually identical power output in each mode. Even in the green Economy mode, which is supposed to limit boost pressure, the dyno read 244 hp and 251 ft-lbs.

244 hp, 251 ft-lbs

Notice there’s a dip in the chart at one point, the dyno operator said this was likely the ECU pulling timing for a second to deal with heat. The engine was in Eco mode on this pull, but you can see that just a second later the engine picked back up again and posted identical numbers to the other modes.

244 hp is about a 12% drivetrain loss, which is better than I expected. But note that the car was going into winter storage, so I filled the tank with ethanol-free 90 octane, and it may make more power on 93, and even more when the engine loosens up.

What do the engine modes do?

Given that all modes made the same amount of power, the next question is, do the engine modes do anything at all? Knowledgeable people in the N world have stated that the different tunes change the engine’s responsiveness and boost targets in the mid-range, rather than max power. Other sources suggested that the engine modes are only different at partial throttle.

Maybe that’s true, but what about Eco mode? From every account I’ve read, nobody is actually getting better fuel mileage in Eco mode. One source claimed Eco mode only works in the UK. Or that Eco mode is different on different platforms, and limits Velosters to 12-13 psi, but Elantras are limited to 6-7 psi. Well one thing is for certain on my car, either there is no low-boost mode, or all modes are low boost.

Next let’s talk about the tunable exhaust. It did add loudness, but without adding power, I don’t see the point. I like to hear my tires working, it helps me drive at the limit. And so louder pipes just limit my driving.

Finally, there’s the pops and bangs of the burble tune. Internet pundits claim this is to keep the turbo spinning, so that there’s less turbo lag between shifts. I can’t confirm or deny this, as dyno pulls are done in one gear, and so lag (or the lack of lag) doesn’t show up on the dyno. I have a manual transmission, and so I could see this being useful if I missed a shift, but for someone with a 8-speed DCT, I’d question the usefulness of the Rice Krispies soundtrack.

Next year I’ll test the different modes on track and see if I can determine any difference in the data. It may be difficult to ascertain that through the noise of driver error, but we shall see what the Aim Solo data logger says.

At this point, all I can say for sure is that there’s no difference in power or torque in any engine mode or exhaust setting.

Miata vs RX-7 Aero

Not so different. Yet so different.

In 1993, the Mazda Miata had a coefficient of drag of .38, and the RX-7 had a Cd of .29. Same manufacturer, same year, both two-door sports cars, and yet the RX-7’s had 20% less drag.

There’s nothing magical about the RX-7 shape, and if you compare its Cd to new cars, it’s only so-so. In The Most Aerodynamic Cars You Can Buy Right Now there are many cars with Cds from .27 down to .22, and a unicorn at .189. (Follow along in this Aero Timeline and see how Mercedes has incrementally improved their aero from high .4s down to .24 complete with wind-tunnel smoke trails.)

But let’s stick with the same year and manufacturer, and see what would happen if you could magically put a RX-7 body on a Miata, and what that would do for performance and fuel economy.

Calculating top speed

To calculate top speed, I’ll use the RSR Bonneville Aero-Horsepower & Drag Loss Calculator. I’ll enter data for a 1993 Miata, with frontal area of 18 sq feet and a Cd of .38. Miatas of that vintage had about 116 crank hp, and if I multiply by .82 to simulate driveline losses, that’s about 95 hp at the rear wheels. (You can argue driveline losses, I’m using figures from Competition Car Aerodynamics.)

First I want to calculate top speed, so I’ll throw some numbers into the calculator until the Horsepower Needed field reads 95. Turns out that 116 mph is the top speed.

Now I’ll drop a RX-7 body on the Miata, and drop the Cd to .29. The top speed goes up by 10 mph to 126 mph. Wow!

However, top speed is rarely important, so I’ll plug in some more common values. I’ll use 60 mph to represent the exit of a corner, and 90 mph to represent a faster section of track. How much power is required to go that fast, and how much power remains?

CdHP to go 60 MPHHP RemainsHP to go 90 MPHHP Remains
.3816.578.546.848.2
.2913.881.237.857.2

At 60 mph, the low-drag RX-7 body has an additional 2.7 hp available over the standard bodywork. Meh. At 90 mph, there’s an additional 9 hp available from the sleek RX-7 body. Wow! Obviously, the faster you go, the more important drag becomes.

Simulating lap time

Drag is obviously important, but more important is lift (downforce). We need the numbers for both drag and lift in order to calculate a lap. I don’t have any published numbers for lift on a Miata, but the Hancha group did CFD testing and I’ll use their lift value of 0.27. In Race Car Aerodynamics (p. 19) Katz lists the RX7 at .24 lift, and AutoSpeeds article on Aero Testing even breaks that down into front lift vs rear. Let’s plug these values into OptimumLap and simulate lap times at my local track, Watkins Glen International.

MiataRX7 MiataDelta
Drag.38.29.09
Lift.27.24.03
Lap2:34.932:33.381.55
1.5 seconds!

So a Miata with a RX-7 body would go over 1.5 seconds faster than a stock Miata. Some people would give their left nut for a second-and-a-half per lap. I’m betting that with windows open, which is how I’ve always raced, the RX-7 advantage would be even higher. This because the Miata hardtop is quite wide, and acts as a parachute, especially when in yaw.

Fuel economy and race strategy

In sprint racing, fuel economy is meaningless, but in endurance racing, it can be important. Especially if longer stints will allow you to do one fewer pit stop during the race, or if your car is right on the cusp of doing the maximum allowed stint. OptimumLap shows a 2.5% decrease in fuel economy using the RX7 body. That doesn’t seem like much, but it can be a big difference.

Let’s use my race Miata as an example. It burns about 7 gallons per hour, and with its 12.7-gallon gas tank, it can go about 1:50 before the tank runs out. This is not a problem in AER where stints are 90-minutes long. But in Champcar or Lucky Dog, stints are two hours long, and I end up doing an extra stop each day. In cases like this, 2.5% fuel economy can be a huge deal.

So not only is the RX7-bodied Miata going 1.5 seconds faster per lap, it’s doing that while burning 2.5% less fuel. If I calculate the total number of laps per stint, the driver in the stock Miata can do 42.6 laps per stint. The driver in the RX-7-bodied Miata can do 44.1 laps.

Imagine if Mazda made a RX-7-bodied Miata, without the design compromises of a convertible top. It would be sleeker, lighter, more rigid… and probably fall flat in sales. Ah well, it would have been great on track!