@Chemahkuu:
I think it's also worth questioning whether any low-level warp field that might exist under impulse power, presumably for the purpose of mass reduction, even exists without the benefit of the stardrive section. You were pointing to glowing nacelles in TMP as evidence of the operation of a low-level warp field during the impulse burn. If the nacelles are generating that low-level warp field, then no nacelles means no low-level warp field.
As for why it might be plausible that a low-level warp field affects time dilation, consider that evidently no (extreme) time-dilation occurs at warp. If it did, we would have noticed it many times over, for one example in people on Earth aging at radically different rates than people on starships. The dialog in TMP is, as I said, an order to go to warp .5. That could be taken as an implication that the effects on the ship are similar to those when the ship is at warp, which would mean no appreciable time dilation.
I think it's also worth questioning whether any low-level warp field that might exist under impulse power, presumably for the purpose of mass reduction, even exists without the benefit of the stardrive section. You were pointing to glowing nacelles in TMP as evidence of the operation of a low-level warp field during the impulse burn. If the nacelles are generating that low-level warp field, then no nacelles means no low-level warp field.
As for why it might be plausible that a low-level warp field affects time dilation, consider that evidently no (extreme) time-dilation occurs at warp. If it did, we would have noticed it many times over, for one example in people on Earth aging at radically different rates than people on starships. The dialog in TMP is, as I said, an order to go to warp .5. That could be taken as an implication that the effects on the ship are similar to those when the ship is at warp, which would mean no appreciable time dilation.