Hey guys, finally got her together and she's running... Well, she's running. Had a scare with a tick, but I got that sorted. Balance chain noise, thank God. Anyway, on to a new one. I've done everything except **** it, but I cannot for the life of me get past 6psi of boost. I'm stock parts from the LSJ, no porting,etc. I've adjusted the bypass valve as much as I can without pulling the charger off and saying "welp, that's the butterfly".. I started out making 2-4psi, adjusted it, got 0-1 at 6k WOT, adjusted again, now getting 6psi at 6k WOT. I've heard the bypass valves are notorious for cutting boost... On a car that was meant for a charger. Being this is the 2.4 SC swapped, and not computer controlled, shouldn't I have above 10psi? My needle for my boost gauge with engine off sits just under median of zero, and at idle I'm at 20 inches of vacuum. I'm open to ideas before I change the bypass valve, but seriously starting to consider it. Thanks!

 

how is the bypass valve vacuum system plumbed? it should have the top port of the actuator hooked to the port on the blower inlet, and nothing hooked to the actuators lower port.

is it a mechanical boost gauge or electronic? are you tuning the car yourself with hp tuners? if so, what are the map values showing?

what blower pulley are you running? if your running a stock blower pulley you should see somewhere around 8psi if everything is perfect. even a slight bit of belt slip will cause a loss in boost, and other things like elevation also play a factor.

 

Sharkey,
The bypass valve is plumbed exactly as you say. Top port to the small barb toward the engine, the bottom barb is vent to atmosphere. Boost gauge is mechanical. I am tuning with hp, I'll get the map value tomorrow, but I'm pretty sure it's close to the gauge. Stock blower pulley. I'm at 1,100 ft ASL. If I'm only supposed to create 8# boost on stock, then maybe I'm right where I need to be, considering the position of my gauge being about the distance between 6 and 8 psi (about 2mm) from being zeroed out when the engine is off. I've just always read on stock LSJ setups of people running 12psi at wot. So I thought that was where I was supposed to be too.

 

a stock lsj will make around 12 psi, right at the rev limiter. an lsj is also a smaller 2.0l engine. with a positive displacement blower moves a fixed volume of air per revolution, an m62 is 62 cubic inches per rotation. the larger displacement of the le5 takes more volume from the supercharger to fill the cylinder, and with the fixed amount of air being fed from the blower you end up with less pressure.

have a look at a data log, see what the map kpa is near the rev limiter, subtract the barometric pressure and convert that number to psi using the conversion calculator in hpt and that will give you your actual boost numbers.

 

Sharkey i'm actually in the process of supercharging my G5 Gt with the 2.4 engine and will be going with the 3.1 zzp modular pulley. How much boost do you think I will get from that?

 

here is the formula

((Super Charger Disp/(1/2 Engine Displacement)) * Ratio * 14.7) - 14.7 = Boost Pressure

the stock lsj crank pulley diameter is 6.3"

in a perfect world you should make 11 psi.

 

If you’re using a stock pulley, 6psi is about right. Le5s make less boost on the same size pulley as the lsj because the engine is larger displacement. I saw about 7 when I was on the stock pulley.

 

Chevygirl, what would I make on a 2.9 pulley? I got an opportunity to get a hub and a pulley for 65 locally. Same guy I bought my kit off of. My goal is to get as close to 10psi as possible

 

I made 16psi on a 2.7 pulley. Also, more boost doesn’t mean more power. What you want is air flow. The more air flow you have, the less psi you will have.

 

I made 10 psi with a 2.7" pulley on my destroked 2.4L but its not a very good comparison for anyone haha.

 

Should I be making more than 6 psi on everything stock? Intake, exhaust, everything is stock with the exception of the resonator missing. Still have my cat too. Y'all are talking 10+ with mods... I only dream of that... Gauge and the logs are very close together.

 

We actually just dynoed a 2.4L with a 2.9" on it. Made 12 psi I believe. It had 9:1 compression pistons though. I will have to pull the dyno sheet to verify.

 

How much would the boost change if I'm running stock internals? Like I literally only bolted it on. No real upgrades to the engine yet. Theoretically, in a perfect world, of course. Lol

 

6psi is what you are supposed to be at with stock stuff.

 

^^^^^ exactly what she said. The rods dont like going much past that.

 

Update: got a 2.8 pulley installed today with an oversized idler. What a difference! Went from 6psi on good days to now 10psi constantly. I'll take the extra. And the torque is nuts in the mid range rpms. It leaned out in the 6-7k rpm area but nothing a quick fix on the tune wouldn't handle. This thing is a beast and I'm quite happy with it. Thanks guys and gals, my car is fun as hell to drive again!

Now, on to race that Honda that sounds like a fart machine lol

 

The real/main gain of a pulley drop is a big increase in low and mid range torque. The added top-end horsepower is just a bonus. The smaller the pulley gets, the less HP gain there will be, but still more torque. IIRC from the early days, the difference between a 2.6" pulley and a 2.5" pulley was something like 0 whp and 10-15 wtq.

 

Update... So after some time I started getting a P0300 and lost some boost.. and the infamous white cloud of crap coming from the exhaust. Since my primary coolant is still full, I can only assume the cores are leaking in the intake manifold. Lovely! So I have the o-rings from ZZP, but I tore the end plate gasket, and I can't find it anywhere. Does anyone happen to have a part number to get the end plate gasket? Being that it's rubber, I don't want to just use blue RTV and plug up the cores. Thanks!

 

What? The rods can handle 400hp

 

what? The rods can handle 400hp.