OK I'm stumped

[Nightmare302]

Car was making ~24psi with a whipple 3.4 stock lower and 3.25 upper. I changed my tensioner and installed a nations alternator after the old alternator died. After the install my manifold pressure is only around 4 and the car taps out at 15psi exactly. It hits it and instantly stops building any more boost, no bleed off like a slipping belt it is perfect then just flat lines. I've checked for vacuum leaks but can't find any even with a smoke test. The boost bypass is functioning as it should and I do not see any signs of belt slip. I'm totally stumped. The car randomly started completely random issues starting and stumbles on a quick tap of the throttle. If you stand on it, it does fine but if you just blip it and it stumbles. Datalogs show my AFR bouncing around at idle which I assumed was the cause of a vacuum leak. I'm lost.

 

[Blkkbgt]

Something is leaking. How much psi did you use when you did the smoke test? It's very possible that you didn't use enough pressure for the leak to show itself.

 

[98 Saleen Cobra]

Belt slip?

 

[joshcarp81]

So you changed something electrical......
Maybe that's where you need to look

 

[Nightmare302]

Something is leaking. How much psi did you use when you did the smoke test? It's very possible that you didn't use enough pressure for the leak to show itself.

Around 2 psi on my ghetto rigged smoke system. It's possible that I couldn't find it due to it being "less than professional".

Belt slip I can all but rule out due to the other problems arising. Plus, it doesn't build boost then fall off it goes directly to 15 then stops. No bleed off not change just flat.

Not sure what an alternator could due to cause this behavior but I will attempt to unplug it and see if it does anything.

 

[Bdubbs]

Damn cars can be frustrating. I'm assuming you checked for codes. I've seen it time after time, replace one part then a totally different issue pops up.

Is your pcv hooked up? Are you running cats on x pipe? Something has to be leaking or clogged up.

 

[03cobra#694]

Something is leaking.

For sure, something got disturbed on the alt install.

 

[Blkkbgt]

Around 2 psi on my ghetto rigged smoke system. It's possible that I couldn't find it due to it being "less than professional".

Belt slip I can all but rule out due to the other problems arising. Plus, it doesn't build boost then fall off it goes directly to 15 then stops. No bleed off not change just flat.

Not sure what an alternator could due to cause this behavior but I will attempt to unplug it and see if it does anything.

2 psi is way to low, that won't show you anything unless a gasket of some kind was completely gone. You need 25 to 30 to show any leaks. If your boost is flat lining at 15 psi anything below that won't show up.

Iam willing to bet that whatever leak you have just happens to coincide with your alternator replacement and isn't actually related.

 

[CobraBob]

For sure, something got disturbed on the alt install.

That's my thinking, too. Some line likely got loosened on the alternator install. I definitely would do a proper smoke test using higher pressure. And go from there.

 

[Nightmare302]

An alternator doesn't touch anything besides the alt bracket and the belt. I'll report back after I test another boost gauge out of the turbo car.

 

[joshcarp81]

I was getting at maybe a voltage issue?......I realize it doesn't touch anything. Just saying that is what you were working on.

 

[jwood222]

Make sure the pulley size of the old alternator and new alternator are the same, could be bottoming the tensioner with just the slight load. I'm a turbo car, but when I received my Nations alt the pulley was smaller, I had to call them and make sure it was correct.

 

[Nightmare302]

Make sure the pulley size of the old alternator and new alternator are the same, could be bottoming the tensioner with just the slight load. I'm a turbo car, but when I received my Nations alt the pulley was smaller, I had to call them and make sure it was correct.

The new pulley was larger. I'm going to order a new belt as well.

 

[Bdubbs]

The nations alternator pulley is about 2.9" and factory is 2.6". I see my normal 20.5-21psi and I just got done installing this alternator.

Maybe slip with bad tensioner or belt, but I highly doubt it's the alternator. You can notch the tab on stock alternator allowing a tighter belt.

 

[Nightmare302]

The nations alternator pulley is about 2.9" and factory is 2.6". I see my normal 20.5-21psi and I just got done installing this alternator.

Maybe slip with bad tensioner or belt, but I highly doubt it's the alternator. You can notch the tab on stock alternator allowing a tighter belt.

The tensioner is a new UPR piece. The next step is to buy a slightly larger belt and try again. Wondering if this is too tight. If that doesn't work then I will switch to the old belt and factory tensioner and test again. I tried to cancel my UPR order 2 times and just get a metco brace but they would never respond to me so I'm stuck with this thing, hopefully it's not faulty as their customer service sucks.