It sounds like you experienced some of Javier's "wild reds"
It is not my usual subject, but I have shot cars and aircraft in Ektar in full sun with good results. Not super results, but not bad. Here is one of a Caddy:
Not real great, but not too bad either. I had a bit of over-exposure going here and the red looks a little flat as a result. It may be that more attention to the scan might yield better results as well (I used default settings from the Coolscan 5000).
You did not mention what ISO you were shooting at or where you had your processing/scanning/printing done. My experience has been that quality processing is essential as is appropriate exposure. I was getting very mixed results before I switched to a local pro lab.
I did a set of exposure tests last year with the results posted on this thread:
https://www.pentaxforums.com/forums/pentax-film-slr-discussion/66735-ektar-ex...2-2-stops.html
In summary:
- Avoid overexposure
- Avoid underexposure even more
- Use a pro lab for processing
Steve