wdwalker

i think you're the one who is misinformed, buddy. backpressure in the exhaust system of a turbo car, especially one with a small 4 cylinder engine, is very valuable in spooling a big turbo. think about it, when not in boost, the system acts like a n/a vehicle. i'm sure you aren't going to argue that on a non aspirated vehicle that overly large exhaust piping that eliminates backpressure is good for torque gains.

Koby

No.

If you put any resistance (backpressure) on the turbine, this is going to slow the rate at which it can spool. Go read some basic books on turbocharger theory. Don't even try to associate N/A cars with Turbo. You are confusing yourself and everyone else.

fusion210

Actually you don't want back pressure behind anything.
You want exhaust velocity. :P

J-SMITH69

backpressure can be a good thing on a turbo street car.

just like small charge pipes can be good too.

Shift_Spool

Dammit! Well we replaced the plug wires, and the rotor (it was rusted). We fixed the dip and i'ts making more power with the timing fixed. It has some random misfiring like once in the pull. But it still isn't making the power it should. I'm out of ideas. And so is Matt.

bermanator

basic rule of turbocharging - the less backpressure the better
learn yo ---- fool

Donald125

check compression.
check CAM timiing,

Shift_Spool

I think the compression is fine, it's runs great when not in boost.


This is how Matt explains it

Alright we did some more tuning today and it still isn't making a difference. In fact bigwig found out how to import the p13 maps into uberdata so this time we were using actual p13 timing maps. Total timing is around 22*. We got the afr line real smooth right up around 11.7-12:1 with no dips. We even regapped the plugs(when i checked them they were at .035) down to .028. We also replaced the plug wires with ngk blues and replaced the rotar in the distributor. It is very apparent that the car is having ignition problems. There are all kinds of little misfires in the graph where it goes reads very lean for a split second that show up on some pulls and on other pulls they don't show up except for maybe 1 or 2 little misfires. I even tried adding and subtracting timing in the boost columns without much change at all. There is definintly something wrong here

Shift_Spool

Well I think I'm going to be replacing the wastegate beacuse it's an ssautochrome and it is now running 11 psi, and it should be around 8.5 psi. And I may replace the turbo also because it's also from an ssauto kit, and even though it says 10 psi, maybe it's crappy 10 psi. I dunno. I wanna get a bigger turbo anyways.