How do set the max NSURLRequest data size that gets cached?

Question

On the iphone, I'm using NSURLRequest and NSURLConnection to download images into my app. asynchronously.

I also want these requests to be cached. What I've noticed is that some of my images do get cached and some don't.

I'v implemented the delegate method

-(NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse

For the bigger images, roughly larger than 120k this method is not being called and the request is not getting cached. With smaller images it seems to be working fine.

Is there a max request response size that can be set to allow caching of larger requests?

Is this possibly related to something else?

Thanks,