Caterham driver Kamui Kobayashi has conceded that Renault powered teams are currently unable to compete with rivals Mercedes and Ferrari.
Renault has endured a troubled start to 2014 when problems at the first test in Spain restricting the running of Red Bull, Toro Rosso and Caterham.
Kobayashi completed 66 laps and was the fastest of the Renault powered cars, albeit some 4.9s off of the pace set by Kevin Magnussen on the second day of the second test in Bahrain.
"This is what we have in our hand right now so we have to help them to be able to fight with the other engine manufacturers," Kobayashi told Autosport.
"At the moment, we are definitely too weak pace-wise, so we give the maximum chance to them and thereafter we have to work on our car. So we are waiting for the engine system."
"During testing, we meet some other cars and clearly we can see the Mercedes cars are much quicker in the straights, 20-30km/h more and it would mean different braking points, everything, if we had proper power. We will see what we can do in a short time. At the moment, we are definitely quite late."
Kobayashi endured telemetry problems during the morning session but is more concerned by the grip out of slow corners.
"We had many problems on the engine side. This is what we are basically waiting for because we have too aggressive power delivery, which is very difficult to handle under acceleration out of the corner."
"So at the moment, slow corners are very difficult because we don't know how much grip we can get."
While Red Bull and Toro Rosso completed 59 and 58 laps respectively, Lotus has encountered problems with their power unit.
Grosjean's running on Wednesday was truncated by an energy store issue while more software and installation problems limited his running on Thursday.
The E22 has racked up only 26 laps in Bahrain with half of pre-season testing completed.
"We achieved some more laps today but there’s still work to be done," said Grosjean.
"It’s been a frustrating couple of days as I want to get as many laps under my belt as possible, but at least we’re learning some things about the car."