The reigning four-times Formula One champions managed a miserable 21 laps over four days at the first test in Jerez at the end of January after suffering a litany of issues.
Renault have already held their hands up as they encountered hardware and software problems with the new-for-2014 power units.
Now Newey, Red Bull's chief technical officer and the brains behind Sebastian Vettel's recent dominance of the sport, has also conceded to encountering woes of his own.
Speaking at the RAC's Annual Motoring Dinner, Newey said: "What stopped us at Jerez - on our side as opposed to Renault - was a problem where the bodywork local to the exhaust was catching fire.
"It was really a lack of time (that caused the problem). It was something we could have proved out on the dyno (a device that measures engine output) if we had managed to get everything together earlier.
"But Renault have been up against it in terms of their use of the dyno; we have been up against it making the parts in time.
"So had we been a couple of weeks further ahead then that could all have been done in private on the dyno. But unfortunately it was done in public."
Whilst openly stating "hands up on our side, that was a Red Bull problem," Newey has also revealed to trouble trying to accommodate the cooling package required this season.
With the switch to 1.6-litre V6 turbo units, and the introduction of the ERS (energy recovery system), it means the cars now require more extensive cooling systems.
"The Renault seems to have a particularly large cooling requirement," added Newey.
"It is certainly a challenge to package everything in," said Newey.
"The radiator area we need to cool the charge air from the turbo and additionally all of the extra cooling we need for the electrical side of things - the batteries, motor generator unit, control box - is roughly double last year's car with the V8.
"So trying to package that in without compromising the aerodynamics too heavily is a challenge."