The NSX dude

So I dropped my car off for service and I'm still having boost isssues. I would say 1 out of every 10 WOT's it seems to break up. I know its not bad gas as the dealer said it would be happening constantly.

I have replaced the fuel pump, spark plugs, coil packs and smoke tested the system. Still having the same problem. The wierdest thing is the car has no check engine lights and is 100% stock.

What is my tech missing? He is now going to pressure test it he said. He's thinking its a vaccum line or something stupid.

neanicu

Did you check your diverter valves?

The NSX dude

Twice, holding vacuum.

Next?

Dock

How much boost do you show at WOT?

The NSX dude

0.7

Dock

Find a hill, slow to 2000 RPM in 3rd gear, and go WOT going up the hill. Note maximum boost and at what RPM you notice any issues with the boost (or with the power delivery). Report back.

Dock

Or if the road can't hold high RPM in 3rd gear, slow to 1000-1200 RPM in 2nd and do the same routine (and maybe a steeper incline).

neanicu

Pressure testing it is a really good idea! Of course you want to do it under load,see if it exhibits your problem. You want a constant pressure,no bouncy needle.
How are your actual turbos? Are they leaking any oil?
How many miles on the car?
Any recent work that has been done to it?

The NSX dude

Less in 2nd gear, more in 3rd and 4th gears. Starts at about 3k RPM and only on WOT. Happens about 1/10 of the time. Very odd.

neanicu

How are your wastegates?
Did you check those?
Quote :

' A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost pressure in turbocharger systems, to protect the engine and the turbocharger. One advantage of installing a remote mount wastegate to a free-float (or non-WG) turbo includes allowance for a smaller A/R turbine housing, resulting in less lag time before the turbo begins to spool and create boost. '

neanicu

Starts at 3K because only then are the turbos kicking in...

neanicu

0.7 Bar is perfect for stock. If you had a boost leak I believe you wouldn't have been seeing 0.7....
Are you sure it's your boost...?
How's your clutch?

The NSX dude

My car has 9,9XX miles but sat and wasnt really used often since 2007. In 2007it had 9,750 miles. I had a PPI done at Mckenaa Porsche in Cali and they said the car was perfect. No issues. I'd avoid them as they obviously didnt know anything. Seems obvious something was off.

I have the car at a Porsche dealership here in NJ, they are super nice and very helpful.

993GT

if more boost is present in higher gears(ie in 5th vs 2nd) then it is likely 'weak' wastegates, or less likely but possible vacuum/boost leaks

Dock

A stock Turbo doesn't build boost below 3000 RPM? Mine has been modified so long I can't remember what stock does in terms of boost.