I read a thread a little white ago about the sound of a "pinging" engine. That got me thinking about some sounds I've occasionally noticed when at WOT since I installed the HBP on the S/C. Every once in awhile, particularly in the upper RPM range of 3rd gear, I notice a metallic sound kinda like the "nails in a can" sounds that someone had previously described. If this is indeed pinging, what will I need to do? I understand the octane increases may help. We have 92 here. Is is possible that the fuel pressure regulator may need to be turned up a notch to deliver a touch more fuel or is this not the answer? Just wondering if I need to worry about the sounds. Thanks!

 

Sounds like you've got pinging (pre-ignition) by the way you're describing it. Have you tried throwing in some octane boost to see if it goes away? It may add another .5 octane. I also read that some have unplugged the IMRC which helped.

Are you thinking of adding a fuel pressure gauge next to the boost gauge next?

 

Unplugging the IMRC may take care of it. But what you are experiencing is knock. I wouldn't touch the FPR unless you have a fuel pressure gauge to know where you are at and where you are going.

 

Not an expert, but i would bump up the psi a couple of pounds and that should take care of it. i was experiencing the same, need to put a fuel pressure gauge on beforehand though.

 

I was gonna get a dyno soon anyway and they usually like to monitor the A/F ratio at this place. I just don't want too many gauges in my car.

 

I called Comptech and I was told to increase the fuel pressure one full turn (on the FPR) and try that... He said it was probably related to the HBP.

 

Sure would be nice to get the A/F ratio checked to make sure you aren't getting something more serious than pinging -- like detonation. It sure would be nice to see where it was sitting...

Scalbert knows more about the S/C. But, I worry about metallic sounds at higher RPMs near or at WOT...

YMMV

 

The problem is the car goes lean for a moment at the VTEC change over. If your fuel pressure is already about 90 PSI, bumping the regulator up won't do too much as the bypass valve in the pump will start dumping the extra fuel between 85 - 90 PSI.

The first thing I would try is disconnecting the IMRC actuator and see if that helps. It changes the flow dynamics enough to limit the lean spot while not decreasing power. And it is a simple 5 second chore.

 

i think some 93 octane would do the trick

 

How do I disconnect the IMRC? And I thought the actuator action leads to increased power in the TypeS cars??

 

#1 You can pull the connector to it. That would be one option. It will default to "no-actuation."
#2 You could also "mess with the cable" and disconnect it from the actuator.

I'd be thinking about #1 as the easiest option...


I think Scalbert originally determined that there was very little loss in power with the original S/C setup he was running, but I believe a subsequent dyno showed a small gain in power with the actuator working.

If you have a normally aspirated car, the IMRC needs to be working and you're looking at a pretty nasty power loss at higher RPMS with it disconnected or broken. With the forced induction, there is less impact (that's what I believe

 

Correct, I made a little bit more power with it working, 323 WHP versus 315 WHP. But that was with some knock present too. That 8 WHP, or 2.5% change, was not worth the knock. Brad's dyno also confirmed this aspect and was about the same percentage change.

Also, as Eric mentioned, #1 is the easiest. Just pull the connector. You can always put it back on in a matter of seconds.

 

It is, when at or below atmospheric pressure. But once positive manifold pressure is applied the Helmholz effect is minimized or eliminated.

 

Heck, it was you and Corky Bell which made me look into eliminating the IMRC actuation to see if there was a change. You may recal this article:

http://www.geocities.com/mikey9t6/car_uvwxyz_vris.htm

We didn't start with pulling to plug to solve a problem, it was just out of curiosity. It was later found that knock was eliminated with this though.

Also, in both Maximum Boost and Superchargered by Corky Bell, he mentions that once forced induction is applied, fancy manifold systems are practically made irrelevant.

 

Really ??

 

I went ahead and turned the fuel pressure regulator screw one full turn. I ran at the track tonight w/ 7 runs and never heard that metallic sound. I'm thinking the two previous owners of the S/C may have played w/ it a little or the HBP was demanding just a little more juice.

 

how did you do?

 

The problem is that you are already above the pressure of the integral bypass valve in the fuel pump. It opens between 85 - 90 PSI and starts dumping fuel. At the lower revs where the flow rate is lower you can maintain 100+ PSI fuel pressure. But as the revs come up and the fuel flow demand increases the pressure starts dropping. So no matter what you do with the regulator the pump can't supply the higher demand.

Been down this road quite a while ago.

Just try unplugging the IMRC actuator and see what occurs.