I didn't get much help in the Expy/Navi or SC/TC forums, so I thought I'd try a repost here:

I have a 2000 Lincoln Navigator with the 5.4l 32V Intech motor. On top, I have a Kenne Bell SC pushing 9 psi. What I’m curious about finding out is a definitive way to determine if I am suffering from ‘ping’.

I’ve had a bevy of high performance vehicles during my life so I’m well aware of what it sounds like and I believe I hear a faint pinging at time when I drive. I only think I’m hearing ping between 0-5 inches of VACUUM. The vehicle is tuned well and dead nuts stable under boost. It’s just in that area of low vacuum, just below boost where I think I’m hearing it. It’s not continuous; just tick, tick, tick, now and then. Of course, if I let off or if I tip into the boost I think it goes away.

So what if any definitive measures can I employ to determine if I am encountering pre-ignition? As I understand it, the knock sensor is disabled on my application. My scan tool, AutoTap shows a knock retard data item, but it doesn’t seem active (I see no values). I’ve watched the spark advance when operating in said range and I’ve got a decent amount of advance 7-10 degrees. Of course this drops off to –4 or so as soon as I get in the boost.

What does the board wisdom sayeth?

 

What chip are you using and what's the PCM code? Sometimes the knock sensor can be activated with custom programming.

 

Kenne Bell Switch Chip and DZU3 PCM. I'd sure like to be a bit more agressive in timing. Operation with no chip installed under boost runs like a raped ape but alas is lean or too advanced and I get into some ping (not trivial but not hammering either) between 4600 and 5250.

 

KB's supercharger chips tend to be pretty conservative because they can't rely on the end user doing dyno pulls. By erring on the side of a richer a/f ratio, they err on the side of safety.

Here's the thing to do:

Get a dyno pull that includes an A/F ratio graph. See if you can save a few bucks and check with KB to see if they can adjust the a/f ratio by the graph. A/F is critical to max power within a safe limit. Also, get a graph with the stock PCM.

The reason why you see "raped ape" power with the stock tune is because its too lean. It's also not safe.

If KB won't adjust it, let me know. I'll check into the knock sensor for that code, but I certainly can give you an optimal ratio if you supply a graph. I've done chips for KB SC's before, and someone that works closely with Diablo has a Navigator with a KB SC so there's a lot of hands-on tuning that has been done for it.

 

If I may ask one more question. And I'll be more than willing to pay you or your staff to answer the question, just tell me who to call and speak to.

With the A/F graph we can set the fuel delivery. How do we determine the ignition advance curve? I am also curious as to whether I can use more ignition lead in winter than summer. I've never been afraid to pay and pay well for EXPERT knowledge. In fact, if I had the time to drive the 856 miles to your shop I'd do that.

Can the chip you suggest provide two or three modes of operation? Unboosted, 9psi/93 octane, 14psi 104 octane?

 

Come on guys, we always get to this step and then there are no responses.

 

No... its just that I'm so busy handling my customers (12+ hour days) that I'm swamped. The ignition advance is determined by the amount of boost, and its probably already correct in the chip you have. The key here is the air/fuel ration, and you'll need a dyno to determine that. Where are you getting 104 octane from?

 

Im a little old fashioned, but I would take a long skinny screwdriver and place it on the engine block while shes running, slowly listen and locate her, then state the info.good luck!

 

Sunoco racing fuel (dual fuel setup). Power is as attributable to timing as it is to boost. I'd like to have a bit more exact way of determining how much I can apply. I suppose one we have A/F dialed in we can burn and burn and burn the chip; bringing up timing until detonation and then backing off plus a little extra for safety. That ought to cost a small fortune.

 

Its a good idea for a lifter tapping but a little unpractical for spark knock. I'll take off my hood if you're willing to sit in the engine bay and listen when I mash the go pedal.

 

I do get ping on my FORD when vacuum got below 5 hg. Turned out to both my MAF and plug wires. You're application? Could be a bevvy of things.

 

My application is in my signature. 2K Navi Intech with SC. What I'm looking to do is find a definative way to know if I have it besides listening. If I have it at all, its so mild its barely hearable. No problems under boost, just a tad a 0-5in Hg Vacuum if its there at all.

 

Timing does equate power. However, there is a set formula for it (x amount of timing for every y amount of boost), just as there is for nitrous (x amount retard for every y amount of HP shot) and that's typically not the issue with the KB chips --- its the a/f ratio in their application that usually needs to addressed as they are a little conservative. If you need the formulas let me know and I'll dig up my paperwork.

 

If you know me very well you know I'd love the education. Is there some way I may compensate you for your time?

 

Actually... it'll have to wait. I've had to cut a lot of my list because I've finally decided I'm stretching myself way to thin... for instance, I've dropped support for customer programming EEC-IV computer (86-94, some 95). Right now my priority is freeing up time....