WyomingTII

I was wondering, does porting effect durability? This question has two parts to it? First of all does porting itself reduce durability? Second of all, does the braaap reduce the longevity of the motor? I thought maybe the rich lean scenario caused by porting that goes on inside the motor causing the iconic braaap may somehow hurt the motor, furthermore it would apply the force of the explosions to the internals then release the force when it miss fires acting like a hammer in the same way compressor surge/ turbo bark is bad for/hard on the turbo. See I always tune it rich enough that it doesn't braaap at idle.

j9fd3s

iTrader: (3)

there are two parts to it.

1. the hole in the housing can be unreliable. poster child is the J-Bridge port where you cut into the water jacket, and the water seal. you put sealant on it, but its not going to run for 100,000 miles worth of heat cycles before it starts leaking. ive also seen a lot of street ports that were done wrong and let the side seal hit the port, which breaks the side seal.

2. the USE of the engine changes. notice that the stock ~79 Rx7 engine will happily run for over 100,000miles, but the competition engine is only good for 600 miles. this is because the stock engine spends most of its time under 30% throttle and 3,000rpm, whereas the competition engine spends 80% of its at full throttle and its running up to 9,000rpm, that is a HUGE difference. if it weren't for the carbon apex seals that the competition engine runs, which wont last as long as the stock iron ones, it would probably last longer than the stock engine, if it was driven the same way.

peejay

I have about 50k on a bridge ported 13B. Most of the parts in that engine had maybe 160k on them before I built the engine. Still runs fine although compression is a little soft because of chrome flaking. The rotor housings weren't perfect when I built the engine and there is nowhere to go but downhill.

Change the oil frequently, feed it clean air, and you won't have problems. As noted, wear is directly related to use, not porting.

Way way back on the pre-WWW days, I remember one of the rotorheads in Australia was commenting that his J-bridge with carbon seals finally needed a rebuild after 13 years...

WyomingTII

I see, well is the braaap bad for the motor or should I not worry about it?

peejay

When you are under load it smooths right out.

j9fd3s

iTrader: (3)

the 787B Braps, its at the track every weekend all summer, and it went 20 years between rebuilds. i wouldn't worry about it.