The triple DTM champion believes that the victory achieved by Laurens Vanthoor, Kevin Estre and Andre Lotterer for Porsche Penske Motorsport in the Qatar 1812km season-opener gives BMW "hope" in the first year of its WEC programme with the M Hybrid V8 run by WRT.
But he stressed that following a best result of 10th at the Losail International Circuit, promoted into the points by Cadillac's disqualification, BMW still has work to do.
Asked by Autosport for his views on the impact Porsche's victory has had on the BMW camp, Rast said: "It definitely gives hope because you can see that the LMDh car actually can fight for overall victory, we are the same car category more or less, so the potential is there.
"But probably we need a bit more time.
"Our test programme in the winter or last year for this season was a bit compromised due to a lot of weather. I’m not saying that this is the reason, but we were not very lucky with the weather conditions and didn’t do a lot of dry running.
"Every test we get now in dry conditions helps a lot to just make another step.
"Even though it’s just for driver comfort or more consistency in the car, that helps already. We just need more time and more testing to get on that level."
Source: Autosport