How exactly should my boost come in? It seems way too difficult to get the car to go into positive manifold pressure, and it won't seem to do that until the VTEC engagement point or higher. It also seems to rise steadily to reach about 6PSI right at the cutout. Is this all normal? I put boost and oil pressure gauges in at the same time, so I can sort of watch what the boost is doing while I'm driving. It also appears sluggish in a way at low speeds (say in 1st gear) and it seems much happier in 3rd gear or higher. My oil pressure gets as low as 30 pounds at idle, and hits 100 at WOT. Anyone else care to chime in on what kind of oil pressures are normal for this engine? Thanks.

Greg

 

The oil pressure #'s are normal for an engine at operating temp. You'll see higher cold oil pressure at idle, in the 50-70psi range.

As far as boost goes, boost is dependant of throttle position and engine speed. With my Vortech, I could be cruising around 4k rpm, and not be in any boost. As soon as I opened the throttle over half way, I was in positive manifold pressure.

Centrifugal SC's boost rises with RPM, max boost is always at max RPM.

6psi max is correct for a Comptech SC.

 

Thanks for the input. While boost rising to cutout makes perfect sense, I'm kind of dissapointed... I suppose that's why you're going to a turbo then? My WRX takes a little while to spool, but once it's spooled the full 16.5 PSI is there and ready to rock'n roll.

Since the supercharger doesn't build boost rapidly, how exactly is it supposed to provide "instant power". I mean, I thought that was the whole idea behind using a blower in the first place! I've never seen the inside blade arrangement of a centrifigual blower, but apparently it gives up something to a roots style on pressurization at least.

My oil pressure is as you indicated when it's cold, but it certainly does tend to peg the gauge at 100 PSI very easily. That is, in my experience, rare to have that much oil pressure (though certainly not a bad thing). Must be all those RPM!


Greg

 

The centrifugal is engine driven, so impeller speed is directly linked to engine speed. To keep the engine in boost, you have to keep te rev's above 4-5k. Some consider this a weakness of a centrifugal, but it is always predictable in power delivery. the more you rev it, the more power it makes.

As far as the oil pressure issue, the VTEC system requires lots of oil pressure and volume to operate. It takes at least 60psi to maintain VTEC operation. There is also plenty of oil bled off past the rocker pistons. That's why it takes almost 6 quarts of oil. You need enough oil to keep the bearings happy, pistons cool, and VTEC operating.

 

That's why I am thinking about going turbo
But, oh.....the money!!

 

I can't believe how many times I have to correct this misconception. The 'SC = instant power' idea only relates to positive displacement SCs. The Paxton/Comptech and Vortech blowers are centrifugal so boost rises with RPM.

If you want 'instant power' it's easy to get. Just cruise at 5000rpm with the throttle mid way or less. As you are already reving the SC is moving the air, but the bypass is releasing it. Now hit the throttle. The bypass closes and you have instant boost (no lag) and the car wil take off like a bat out of hell.

 

Interesting information. That probably explains the runs where I'm waiting for an opening in traffic (in a lower gear) and then nailing the throttle when it appears. Under those conditions, it does indeed take off. Guess I'll just have to live with what I've got! I was hoping for lots more power at lower RPM though. That way, I'd be able to pull out of corners out on the race track in the next higher gear, saving a shift each way.

Greg

 

Try a smaller pulley. It raises your peak boost, but also move the usable boost further down the rev range.

I'm running an 8lb pulley and it's a great improvement. I went the whole hog and used bigger injectors and AEM EMS but there are a few that have used the stock set up and just let the FPR increase fuel. Even Comptech have done a few of those. Slight adjustment to the FPR is all that is required.

 

Didnt you drive an SC'd s2000 before doing the install?

The things that you are mentioning are why so many people express disappointment when driving an SC'd S for the first time. It's all about learing to use the powerband.

 

Sounds like you should have gotten a turbo instead of a SC.