That's odd. When I put more speed on the ball, I, and I think most bowlers, tend to rev the ball more. That makes me suspect you're not using your normal release when you throw it harder, maybe not keeping the hand behind the ball, or your wrist in the same position or your thumb in the normal position for a quick release.

Don't forget: with more speed your ball is not going to hook as much. I hope you're not interpreting that as meaning you put less revs on it.

As always hard to say without a video.  You can create more ball speed and less revs and less ball speed and more revs.  If you are arming or muscling the ball to much you may not be getting a good wrist snap at the bottom of the swing. Think of a bullwhip. If you swing it really hard with only our arm and a firm wrist no snap. If you swing you arm with a relaxed wrist and hit the end big snap.

There is a misconception out there that revs seem to be the most important thing.  "Manufacturing revs" can lead to some pretty bad habits and/or injuries. 

Start with your footwork, arm swing, and other mechanics and make sure your timing is good.  If your mechanics are good then the (proper) revs will fall into place.  Realize that you will have a rev rate "range" that will be natural for you and your style. 

I agree with Lane Carter's comments.  I do feel that many of the players I see with low revs have hanging issues, due to wrong pitches, spans, or  to wrong bevel, or knuckling.

Get the fit right, get  timing right and nearly everyone with a fingertip grip will have plenty of hook and revs and hopefully speed!

Regards,

Luckylefty

I think there was a trade off between speed and revs in the old style release where we hit up on the ball to get revs.  The first cup wristers increased revs, at the expense of speed.  When the first reactive balls came out the added friction put more of a premium on speed. Many of us learned that the so called less is more release where we rev it from the back of the ball at the bottom of the swing both increases revs and ball speed. 

If you are seeing a trade off, I suspect you are lifting and releasing slightly on the upswing. When you do this gravity becomes the enemy and does not allow a strong release and a lot of ball speed unless you are abnormally strong.