veedubbed

Well, I just blew an apex seal on my back rotor 3 nights ago, but while I'm waiting for a new shortblock, just thought I would check in and make sure my AFR's are acceptable.

I put a 3" turboback on the car and removed the emissions ad put in 690cc secondarys all at once. It spools a hell of a lot quicker with all of that, and up until my secondary's kick on it was running at a steady 12.8, under maybe 5-6 pounds. When the secondarys kick on, it would run up to 12-13 pounds and the AFR's would be in the mid 11's. Is that pretty safe for that boost?

Also, it would idle in the mid 12's. Not really sure why.... but I do that if I set my TPS to the factory indicated 1K ohms at idle, the car would run horrible. The only way to make it idle smooth and run good is to set the TPS to 0K ohms at idle. Ideas on that one?

C. Ludwig

iTrader: (27)

Your a/f ratios aren't bad per se but there is more that influences "safe" than just that. You're pushing the stock turbo pretty hard at 13 lbs. Your sig doesn't list a front mount so I assume you're still using the stock top mount which is also being over worked at 13 lbs. Lastly, dunno about Virginia but it's been 100 degrees here in Louisville for the last week. We were seeing 130* manifold temps off boost in a car we were tuning last week. So stack all that up and you're pumping very hot air into the chamber. Hot air is a big contributor to detonation and that all needs to be addressed to be "safe". At the point where intake temps are extremely high super rich mixtures aren't neccesarily going to save an engine from detonation.

veedubbed

Well, the thing is, 13 pounds was off the wastegate........

I just put 3" turbo-back on it, and before it would hit 6 pounds and stop, but now it hits 6, then creeps up to 12-13. I guess maybe I should port the 'gate or look into an S5 unit for the new shortblock.


That all makes sense though, I was beating on it pretty hard. A front mount is next on the list of go fast goodies so I will get my intake temps down with that.

C. Ludwig

iTrader: (27)

You've just discovered what every other person who's put a free flowing exhaust on an other wise stock TII has. You're playing in dangerous territory. Even with the larger secondary injectors.

The turbo is running out of it's efficiency range at 13 psi. You should port the wastegate and do whatever you need to do to get it back down below 12 psi. At that point if you want more power look for an upgraded compressor on the stock turbo or an aftermarket kit. A good intercooler is also pretty much a must.

Fuel and spark control would be great. The rtek has show great results in the range of turbo size/fuel you're playing in and the price can't be beaten. Want a big single then you just need to pony up for a standalone and do it right the first time.