Meanwhile, back in Toronto, Flash repeats the process with Warp.

*AUTHORIZATION GRANTED: WARP, B-05*

And off he goes to join his brother!

Right before Warp appears in the entrance, Impulse hears the mechanized voice on his end. *RECOGNIZED: WARP, B-05*

The same happens when Flash follows him through the zeta-tube a few seconds later.

*...FLASH, 04* 

He nods approvingly when he sees Impulse is back in costume. "Right, this way to the racetrack."

He zips off, simply assuming they're quick enough on the uptake to follow.

Yep. They're right behind him.

Then they can zoom through identical windowless metal corridors until they come out onto a massive indoor racetrack, which curves around at each end, somewhere in the distance to form a giant loop around the outside edge of the facility. There are observation windows along the inside in this particular section. 

"We'll go round the track once as it is, then I'll head up to the control panel and start adding complications," Flash explains.

"There are no lanes, and anything goes as long as you don't hurt each other - or me - or damage the equipment. Not that it's particularly fragile, but I race Superman around this track; the rules are calibrated for him." 

Warp snickers.

"I'll do my best not to mess up your racetrack," says Impulse, bouncing again.

"We'll see," he says, flashing them a smile, and takes off clockwise around the track with no further warning. 

Time to see how Impulse measures up in a straight race where there are no shortcuts. 

—slower than Warp. Noticeably so. And he's clearly trying, it's not a tortoise-and-hare situation.

Warp finds this endlessly entertaining.

- also, it turns out he wasn't anywhere near his top speed when the race ended.

Hmm. Well, adding some obstacles to slow Warp down might level the playing field a little. 

"Was that as fast as you can go right now?" he asks both of them when they come to a halt back where they started. 

"I'll check on the system, but I'm pretty sure Warp was getting close to Mach 5 at the end there."

"I think I could still go faster."

"I keep trying to go faster, and the weird thing is that it works but not right away, like there's some kind of - reservoir of speed that will dispense more on request but takes a second to get around to it. I don't think that's how this is supposed to work."

He frowns.

"No, I've never experienced anything like that. Do you have to do that every time, or is there a practice effect?"

"I wasn't measuring, obviously, but I think the top speed I got to in the race to the zeta tube is the same top speed I could reach without trying when we did this race. And then I was back in that pattern of - spaced acceleration."

"Well, that's something at least," Flash says. 

"Right. Warp, I want to see what your top speed really is; run a few more laps until you think you've hit it, and we'll see what the computers measure."

He turns to Impulse. "I want you to tell me everything about your experiments that could possibly have led to a difference between your powers and his."

Off goes Warp.

Impulse frowns thoughtfully.

"As far as I can tell, there isn't anything," he says. "We used the same batch - I was very careful about lab safety, there's no reasonable chance anything got into it that shouldn't have - and I'd have expected it to not work, or explode, or something along those lines, if I'd messed up that badly - we're identical twins so it's not likely to be a difference in our respective reactions to the formula, there aren't that many things that are different between us - and the way the difference is presenting itself is deeply puzzling, why would I have a limited top speed that I can raise by wanting it to be higher?"

"It's probably the alchemical side that's the issue, rather than the straight chemistry," Flash contributes.

"Which unfortunately means it's out of my expertise - I'm afraid I leaned somewhat heavily on my predecessor's notes for that part of my formula. I might ask around in the League if it continues to be a problem, see if any of them know more." 

He glances at Warp blurring by.

"All right. It's not particularly inconvenient so far. There aren't that many purposes for which I might need to break Mach 5. It does kind of bug me not to know what's going on, but that's not urgent."

"Fair enough. I expect you'll let me know if that changes," Flash says wryly.

"Let's go ask the computer what your top speed was just then."

He heads up the stairs in the direction of the control room for the track. He needs to be there for the next part anyway, and he has a feeling Impulse will be fascinated by it.

Impulse follows Flash.

The control room is pretty impressive. As well as a viewing window onto a section of the track, it has multiple monitors that, between them, cover a decent portion of the rest. A bank of controls let someone standing in the room change the environment of the track, adding both holographic and physical obstacles, or environmental effects like snow, heat or cold.

Flash pulls up an analysis of Impulse's speed.

"Mach 4.2, not bad. Warp managed 4.5 in that lap, and he's up to 4.8 right now - 4.9 - "

"What's your recorded top speed?"

He checks the logs. 

"The highest I've managed on this course is...Mach 12, apparently. I keep trying to push it higher every so often, but there's only so fast I can go and still have time to make it round the corners."