Hello, Newb with a forged motor question
 

Hello all,

First, I'm an american car guy for the most part. Have owned Vettes, Mustangs, Camaros, etc. So I'm very familiar with those but thought a Miata would be a lot of fun to buy and throw on a turbo. I've owned several boosted vehicles so I'm not new to the tuning/boosting game, but I usually know what the base motor can handle before I throw a blower on it.

I've searched but have a question about the bottom end. Is anything forged or no? What is the weak link for these cars when being boosted? Assuming the tuning is good what can you expect from a stock bottom end (HP wise) and are there easy upgrades to increase longevity? This would be for a DD car.

Thanks,

GNH

Hi there. This has been discussed multiple times, and I believe can be found in the DIY sticky. Essentially 250hp is your limit before you really need upgraded rods. By that time you might as well also do pistons & rings. You're also going to need a coolant reroute, dual feed fuel line, bigger injectors, and a proper engine management system. You can essentially DD the car with 200ish HP and not worry about internals.

Thanks for the info...I'll see if I can find the sticky.

whats with the collective obsession of dual-feed fuel rails?

The series of tubes don't get clogged that way.

There have been plenty of discussions about cylinder 4 starving with the OEM rail but I agree with you. It's not necessary if you're shooting for around 200whp.

The stock crankshaft is forged and nitrided and should not be turned down. It will handle more horses that you can make without extensive head/cam/intake work.

Fixed. I'd be willing to bet that the stock crank would be fine upwards of 600hp. Maybe more.

What Rafa said hit on the topic somewhat. Before the coolant reroute really caught on, it was believed that the rear cylinders were not getting as much fuel as the front cylinders with the OEM rail, the thinking was that starved cylinder = hotter/lean cylinder which would obviously break parts. Then the coolant path was questioned and found to be the bigger issue. That being said I've seen quite a few 250-300whp Miatas with stock fuel rails.