Originally Posted by sixshooter
Fuel pump is making too much pressure/flow for the fpr. Go back to a stock pump. A good stock pump will make plenty of power, much more than you should ever run with bandaids.
You probably won't take this advice because some buddy or some guy in a magazine has a Walbro that works and I'm just some guy on the internet, and how could a stock pump be better than anything aftermarket? It has to do with being the right tool for the job. It's akin to trying to use a 17mm socket to remove a 10mm fender bolt - you have more capacity than you need but it is to your detriment and not to your benefit.
In my defense it was fine for literally 12 years when I needed 40 psi (per Bell Engineering docs...OK 36 but they say up to 40) with my 1.6 injectors to avoid lean tip in. I have the Walbro 255 that everyone thought was the best option 10+ years ago and that is mentioned in this article http://miataturbo.wikidot.com/fuel-pump
which looks like it was copied over from solomiata.
I had figured with the 15% bigger injectors this would be like running a base pressure at idle of 46psi which I had done for a while (50 actually I was a bit paranoid) with no issues. Where am I wrong in this thinking aside from the obvious (don't work)?
FWIW - popped the top on my afm and used a screwdriver to simulate a little more tension...no help. Actually started to falter either way very quickly. Supports the "overpowered fuel pump" suggestion I think.
I have a whole in tank assembly lying around here somewhere with a stock pump on it, I'll swap that out and see if it works for me.
I suppose this also means instead of the approximate right pressures being 36+8*psi, now I need to be looking at 31 psi idle and 7 psi/pound of boost?
So this probably isn't bad injectors? They were old. Not high mile, just long time in box in attic.