Don't trust to popular science.
As example upcoming "historic" book "Armies of the Volga Bulgars & Khanate of Kazan" by Osprey publishing.
http://www.ospreypublishing.com/store/Armies-of-the-Volga-Bulgars-and-Khanate-of-Kazan_9781782000792
Book illustration of Ottoman-fashioned Bulgars must cause recognition from European reader: "Oh, they are Turks!".
But Bulgar language is not Turkic. Only one language from Bulgar group is survieved. It is Chuvash language.
From "Introduction to Altaic philology: Turkic, Mongolian, Manchu" by Igor de Rachewiltz and Volker Rybatzki.
Chapter One: Chuvash-Turkic
Other work show common root's of Old Bulgar language with Pamir languages (i.e. Eastern Iranian languages, for example Avestan language is often classified as early Eastern Iranian ).From "The language of the Asparukh and Kuber Bulgars, Vocabulary and grammar" by Peter Dobrev.
Mediaval autors don't known about Turkic nature of Bulgars.
Ahmad ibn Fadlan write about Bulgars: "They have a lot of merchants who journey to the land of the Turks,"
http://www.s155239215.onlinehome.us/turkic/10_History/IbnFadlanEn.htm#Bulgars
And last thing. Turks firstly appears in VI century AD in Rouran Khaganate. The early Bulgars (or "Proto-Bulgars") may have been present in the Pontic Steppe from the 2nd century, later Bulgars took part in the Hunnic raids on Central and Western Europe between 377 and 453. In this time no Turks exist yet.
But people don't read historic sources, or serious scientific books.