Coach Adam Sadler decided to include Elite Development Squad regulars Denis Suarez and Courtney Meppen-Walter in the Blues' starting line-up and the decision proved inspired as the two players excelled throughout the 90 minutes.
The unseasonal sizzling temperatures provided perfect conditions and City started the brightest, with Adam Drury and Suarez teaming up in midfield to menace and create chances early on. The Spaniard came close to breaking the deadlock on a couple of occasions, with a shot deflecting just wide of the post and one whizzing over the bar.
The Blues' persistence paid off and with 27 minutes gone Suarez turned provider when his sublime pass found the in-form Hiwula. He confidently finished past United's goalkeeper Liam Jacob to give City the lead and chalk up his seventh goal of the season.
It took just three minutes for City to double their lead with a superb solo goal from Albert Rusnak. The Slovakian tore open the Reds' defence with his powerful run and finished off with a cool strike into the net.
The home side managed to grab a goal back just before half time through striker Gyliano van Velzen and continued to push for an equaliser after the break, with Nick Barmby's son Jack going closest to levelling the scores with a series of chances.
But City remained determined and produced the move of the match with Meppen-Walter demonstrating superb control to find Adam Henshall, whose ball into Drury was fired just wide by the midfielder.
With the Blues oozing confidence and strength, a late penalty after a foul on Rusnak from United defender Luke Hendrie, was calmly fired home to give City all three points. It was an impressive performance from the U18s, with Suarez proving influencial in his creative role in the heart of City's midfield.
Head of Academy Mark Allen was happy with the win but highlighted conceding a goal as an area for improvement.
"It was a very pleasing first half performance and I think we controlled the game," Allen smiled. "We did give away a silly goal before half time though. Whilst we let United back in the game early in the second half, I thought we regained control and went on to win with a good performance."