The 2016 Nurburgring 24 Hours winner had qualified second in the #3 GetSpeed Mercedes-AMG GT3, but hopes of victory for the car he shared with Jules Gounon and Daniel Juncadella were ended by damage sustained in contact with the #115 Porsche Cayman GT4 in the Stefan Bellof-S section of the track.
Engel managed to get back to the pits despite a broken right-rear shock absorber, but the damage proved too severe to repair and the car retired in the seventh hour.
On-board video footage shows the Porsche move right to leave Engel a gap on the left, before moving across and instigating the collision.
Writing on social media after the race, Engel said the non-finish was a "tough one to take when a car moves right and then suddenly back to the left", before calling for drivers to stick to their line when being lapped by GT3 machinery.
"To the amateurs out there we respect you and want you in this race," he wrote.
"But PLEASE stick to your line and don’t change line unexpectedly or zig zag. If you move right then stay right. If you change back to the left like in this instance you are not predictable."
Engel said he has no desire to see the amateur element of the 24 Hours lost, as the race "lives from the pro and amateur coexistence" but said knowledge and adherence of the rules needs to be improved.
"Unfortunately there are still too many out there driving 30, 40 or 50kph in a Code 60 or slamming the brakes next to tow trucks which you are supposed to pass safely at reduced race speed," he said.
"This makes the race a lottery and creates unnecessary danger.
"I’m not saying the pros are perfect, we make mistakes too. But some of the driving out there this weekend has really been terrible.
"It’s been a talking point between many of the pro drivers behind closed doors. So I hope in the future we can get back to better years where there were more cars on track but the quality of driving was also much better - especially the amount of zig zagging!"
Dacia team critical of Pro standards
Engel's crash wasn't the only dramatic incident in the 24 Hours, as a production Dacia Logan entered by Ollis Garage Racing was destroyed following contact with Laurin Heinrich's Dinamic GT Porsche 911 GT3 R.
The reigning Carrera Cup Germany champion making his debut in the 24 Hours made contact with the SP3 Dacia driven by Maximilian Weissermel also at the Stefan Bellof-S.
The Dacia was then fired violently into the barriers, the incident caught by an on-board camera on Manuel Lauck's TCR Hyundai.
Weissermel fortunately escaped without injury after initial complaints of back pain, but team boss Oliver Kriese confirmed that the car is "a total loss" as the Logan's engine is no longer in production.
"It's a miracle the driver got out of the car alive at all," Kriese told Autosport's German language sister site Motorsport-Total.com. "The rear was crushed to the cage."
Heinrich was fined over €3,000 for causing an avoidable collision, but this was poorly received by the team.
A statement on Instagram defended the actions of its drivers and was critical of suggestions that slower cars shouldn't be involved in the event.
"After it has been mentioned in social media by some that the little ones should not drive along at such an event, we would like to say here again very clearly: We have ALWAYS made room and at any time signalled through flashing where you can overtake us," it said.
"Perhaps we should consider not handing out the Nordschleife permit to the young drivers after two NLS races and letting them drive the big cars! Maybe they should start with the little ones first to know how they react and act.
"As a small team fighting for every €, it hit us hard. The driver who caused the accident is simply given a new car!"
Additional reporting by Sönke Brederlow
