present subjunctive vs imperfect subjunctive

Question

You have lessons covering the usage of each tense when preceded by pedir, but I don't see anything about how to distinguish when one is more appropriate than the other. The tense of "pedir" doesn't seem to factor in. There are examples of pedir followed by either tense in each lesson.

Answer

Hola R
I'm not sure if you mean when to use pedir in the present or past tense or when to use a specific tense in the subjunctive in the subordinate clause? Can you clarify that?
If what you mean is how to know when to say:
Te pido que me ayudes vs Te pedí que me ayudaras
this depends on whether you are making a statement in the present or in the past, "te pido que..." or "te pedí que..."; every time you use it in the present tense, the natural sequence of tenses is "present indicative (main) + que + present subjunctive"; every time you use it in the past tense, the natural sequence of tenses is "past tense indicative (main) + que + imperfect subjunctive";
This is what you also find in for example:
"Espero que seas feliz." vs "Esperaba que fueras feliz.", or "Quiero que te vayas." vs "Quería que se fuera."
Is this what you meant?
Saludos
Inma