View Single Post
spuggy spuggy is offline
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,535
Originally Posted by mark houghton View Post
I don't currently use a knock detector...rather, an active ignition retard via pre-set boost level(s).
Safeguard has ignition retard at pre-set boost levels too, but knock retard is a separate feature that can provide additional retard as required (until it doesn't knock, up to 20 degrees extra).

I have the timing advanced over stock and use boost retard feature of the Safeguard to pull it back as manifold pressure increases to arrive stock timing at 12.5PSI. (Initial fairly conservative settings, need to sort out the top-end fueling).

No knock detected whatsoever under full power conditions on the dyno - but as soon as you lift from a full-power run, the Safeguard lights up with the extra motor noise for as long as it takes for manifold pressure to drop below the arm point - the Safeguard has a built-in MAP sensor). Which doesn't hurt power at all, as the throttle is already shut.

Still, the concept of a knock sensor seems very sound whether or not it can hear past all the background noise.
Mine seems to. You do need to calibrate the gain for your sensor/motor.

Hey, the worse thing it can do is cause premature retarding and a little power loss. Seems like a fair trade off I guess.
The only situation where I see any knock retard indication is lower (2600-3000) RPM when the Safeguard arms at 5hg/in due to load/throttle, and usually only climbing hills at a steady RPM and suddenly opening the throttle. I think at least part of this may be CIS going momentarily lean.

For me, the Safeguard pulls back 1-2 degrees of timing for a few seconds (it's always trying to advance each cylinder back to the full setting) in these conditions, although if I goose it harder it will pull back as much as 6-7 degrees of distributor curve before manifold pressure gets high enough that the boost retard starts to kick in as well, CIS catches up and delivers more fuel, or the revs rise - probably all 3 things are a factor, would be my guess.

This pretty much only happens when climbing hills and suddenly accelerating, haven't noticed any knock retard whatsoever doing the same thing on flat and level ground.

As far as power loss, I'd say the car is far more drivable off-boost, ignition advance is independently tunable on-boost, low to mid-range power and drivability vastly improved. It made quite healthy numbers on the dyno.

Full Boost: - stock timing, no false knock. No power loss.

Partial Boost: - Advanced timing, no false knock, better response & more power.

Off-Boost: Maximum timing advance. Much improved throttle response & pickup off the line.

I'm obviously biased, but only because I'm a satisfied customer. I read the thread John linked first time around and decided then to take a chance on the Safeguard.

Finally got around to it and got a professional to install it. (Who, by the way, would happily use MOTEC knock detection on your 930 if you stumped up the necessary megabucks to enable that feature).

I think it works, Guy that installed it agrees. Steve Weiner, Todd Knighton and Jake Raby all have testimonials on J&S's website. Turbocraft sell an ECU that has knock detection.

I don't understand - who exactly is saying "air-cooled motors are too noisy for knock detection"?

John is a great guy to deal with who makes a quality product. That product does just what it says on the tin, as far as I'm concerned - money well spent.

The "blinky light" MSD box is half the price of active per-cylinder knock control - with boost retard.

I think the Safeguard is a no-brainer choice - even if you install it on an otherwise stock motor just to guard against bad gas or other issues (like a detached waste gate hose).
'77 S with '78 930 power and a few other things.
Old 10-14-2010, 05:28 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)