S13 SR20det Boost lag, bad gas mileage - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

boost86 · 09-05-2010, 11:04 PM

So I got this car from a guy I know recently, and he wasn't able to fix this problem. The car builds boost very slowly and gets horrible fuel mileage.

The motor is an s13 sr20det with a brand new s15 turbo, megan exhaust manifold, pbm front mount, etc.

When I go wide open throttle, the car is laggy and slow. On the boost gauge, the boost builds very slowly upward. It's like 3 lbs.. 4 lbs .. 5.. 6.. 7.. 8.. 9.. 10..

So once I reach 10 lbs of boost, the car obviously feels much faster, but I'm at like 6000+ rpm's to get to it. Not to mention, the car gets terrible fuel mileage. I burnt through over an 1/8th of a tank in 15 minutes. The car misfires very slightly at idle.

Possibly problems:
-Timing?
-TPS?
-WG Actuator?

I'm pretty lost, all I'm looking for is some suggestions where to start. The previous owner claimed the timing was set at 15 degrees, but I'm going to check it out anyways.

cotbu · 09-06-2010, 07:14 AM

Just so you know, your description is basically impossible for a properly setup s15 turbo, unless the problem is so obvious you're just overlooking it.

Check turbo to manifold gasket, head to manifold gasket, then boostleak test piping then make sure your turbo is not faulty or dying (spin it, feel for up/down and side play) waste gate connected to flapper, and functioning correctly.

also check for stored codes

boost86 · 09-07-2010, 12:31 AM

Today I ruled out vacuum leaks, boost leaks, and gaskets. I messed with the timing and got the car to run a little bit better, but its still really laggy.

I guess the next thing I can do is check to see if the wastegate is prematurely opening.

EDIT: Timing fixed the problem, it was off by over 10 degrees.

09-05-2010, 11:04 PM	#1
boost86 Leaky Injector Join Date: Nov 2008 Location: WA Posts: 105 Trader Rating: (2) Feedback Score: 2 reviews	S13 SR20det Boost lag, bad gas mileage So I got this car from a guy I know recently, and he wasn't able to fix this problem. The car builds boost very slowly and gets horrible fuel mileage. The motor is an s13 sr20det with a brand new s15 turbo, megan exhaust manifold, pbm front mount, etc. When I go wide open throttle, the car is laggy and slow. On the boost gauge, the boost builds very slowly upward. It's like 3 lbs.. 4 lbs .. 5.. 6.. 7.. 8.. 9.. 10.. So once I reach 10 lbs of boost, the car obviously feels much faster, but I'm at like 6000+ rpm's to get to it. Not to mention, the car gets terrible fuel mileage. I burnt through over an 1/8th of a tank in 15 minutes. The car misfires very slightly at idle. Possibly problems: -Timing? -TPS? -WG Actuator? I'm pretty lost, all I'm looking for is some suggestions where to start. The previous owner claimed the timing was set at 15 degrees, but I'm going to check it out anyways. Last edited by boost86; 09-06-2010 at 01:14 AM..

09-06-2010, 07:14 AM	#2
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 50 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	Just so you know, your description is basically impossible for a properly setup s15 turbo, unless the problem is so obvious you're just overlooking it. Check turbo to manifold gasket, head to manifold gasket, then boostleak test piping then make sure your turbo is not faulty or dying (spin it, feel for up/down and side play) waste gate connected to flapper, and functioning correctly. also check for stored codes __________________ LoverTechnologies "Half Broken Things!"

09-07-2010, 12:31 AM	#3
boost86 Leaky Injector Join Date: Nov 2008 Location: WA Posts: 105 Trader Rating: (2) Feedback Score: 2 reviews	Today I ruled out vacuum leaks, boost leaks, and gaskets. I messed with the timing and got the car to run a little bit better, but its still really laggy. I guess the next thing I can do is check to see if the wastegate is prematurely opening. EDIT: Timing fixed the problem, it was off by over 10 degrees. Last edited by boost86; 09-10-2010 at 12:15 AM..