SBC '7747 without Knock Sensor?

[dave w]

I'm interested in hearing Pro's / Con's for operating a SBC '7747 without a knock sensor.

Background Info:
Some BBC's with 7747's did not use a knock sensor. One example I know of is an 87 GMC 1 Ton 7.4 liter.
Anybody know of a SBC '7747 that did not use a knock sensor?
With the stock SBC '7747 timing tables, it seems to me that it would be almost impossible to create spark knock with regular unleaded 87 octane / 10% ethanol gas?
I know how to disable the ESC in the PROM.
Affordable Fuel Injection / Howell Fuel Injection offer TBI systems without knock sensors?

dave w

 

[eagle mark]

There's a few out there. One I know of because it's sitting on the bench is the 1228747 that is for 5.7L and 7.4L in trucks over 10,000 pounds. It comes without Knock and conservative spark. Have to remember truck motors need a 100% duty rated cycle (somewhere in RPM range) for high loads for extended periods of time.

I used to work for AFI and I can tell you the Knock Sensor circut can cause more problems then worth. Just read a diagnostic manual and it reads "Hit side of block with hammer and see if it sets a knock code" This also happens in racing and since they are selling systems for even non GM motors who knows if it will work and when.

I think the new 427 PCM has a list of differant knock sensors. I'd like to try running all of them and seeing the differance.

Myself I find it's a good tool to tune. run the timing up under worse circumstances, see knock, back off a couple degrees. When your done the knock shouldn't come in... Then turn it off..

 

[MNorby]

While we are on the topic of knock, how much knock is detrimental for an engine? Watching ALDL on a hard WFO pull through all the gears I get say 10 knock counts currently. Granted I'm still working and logging this setup but was a question I starting thinking about.

 

[eagle mark]

An engeeneer from detroit has told me a little ping will not hurt an engine. But knock will. I don't know how to gauge that from 1=ping and 10=knock. But he also told me they ran engines on the dyno under load with ping for 100 hours with no damage but while engines under light knock can explode within half hour.

Find the areas of knock and back out 2-3 degress and do it again.

I had a Caprice 9C1 Cop Car that would register knock and back out the timing. I took out timing till their was none and it still got a knock reading. So knock sensors hear noise! Not just knock...

 

[GMC Truck]

Absolutly they hear noise! Put a gear drive in your engine and see what happens! The knock sensor is "tuned" to a frequency not a sound so anything that keys onto the frequency will set it off.
They use them on marine engines and now outboard motors have them as well. If you cant control the mixture with o2 sensors you control the timing with a knock sensor. Most autos use both because of demanding EPA regulations forcing the engines to maximum lean conditions for smog.

 

[ryoken]

yup... and commufornia is pushing hard for O2's..... actually Merc has a setup, but it got put on the back burner when the economy tanked.. guess someone thought it was a bad time to hammer the marine industry...

i haven't seen one in person yet, as i'm not sure if any have been put on boats yet.. but i've seen pics... it's an integrated manifold with O2.. it's huge, ungodly expensive, etc, etc....

but, if it's a boat with FI, it's got a knock sensor... since day one......

 

[dave w]

Just some facts to post. The pic below are for a stock 350 timing table and a stock 454 timing table. There is also a compare pic to show how much more timing the 454 has. The 454 did not have a knock sensor. The compare pic is using TunerCats so the table is different looking. TunerPro compare does not do math like TunerCats.

I'm going to finish my current wiring harness project ( Re-Working a used Painless TBI harness) without a knock sensor. I'm also going to delete the Emission stuff and VSS also. Now that's what I call a truly Painless TBI wiring harness.

dave w

 

[eagle mark]

Is that with initail advance figured in?

 

[dave w]

Is that with initail advance figured in?

Ok, Let me explain. It's not a simple answer with or without initial advance. It's really a question about the MAIN Spark Bias. It depends on which .XDF is used, TunerPro or Moates.net. The TunerPro .XDF ADDS the MAIN Spark Bias in the timing table. The Moates.net does not add the MAIN Spark Bias in the timing table.

The pic's below shows the same .bin, but different .XDF files.

In the post above, the timing tables are both with the TunerPro .XDF defination.

dave w

 

[Wyomingboy]

Dave W.

I don't know if this would help you, but I am considering getting one of these standalone knock detection systems to work with my new FAST FI system so I can run all the timing the motor can handle. And I have poor hearing, so I don't want to rely on my own ears.

http://www.jandssafeguard.com/

I haven't called them yet, but the testimonials sound very intriguing.

If your motor is pretty much stock, then it doesn't sound like you would have too much trouble. Especially as I know you do your own data logging to check on it.

Good Luck