I haven't been out to the strip for a while, so I went out last night at Speedworld. I loaded in my more aggressive tune before I drove out. I normally mix in some 100 octane unleaded race gas before I run. However, I've wondered if the oil in the intake might cause some pinging. I have installed an air/oil separator in the PVC line and I figured maybe I could run 91 octane with the aggressive tune now.

Well, I was wrong. I ran a 12.43 at 114.80. Pretty slow even for the 3000 foot DA we had at the time. So I looked at the scan and sure enough it was pulling up to 8 degrees of timing during the run.

So I mixed in some 100 octane, about enough to raise the octane to around 94. I ran again and did a 12.42 at 115.89. My ET was about the same, but my 60 foot was 1.95 versus the 1.91 on the first run. But the best way to tell the hp your engine is making is to look at the trap speed. I ran a little over 1 mph faster with the same DA. That is approximately 11 hp more. And the kicker, the computer was still pulling up to 3 degrees of timing. So only 5 degrees more timing is worth 11 hp!!!! That is pretty telling. Now I see why some people run Torco in order to run the more aggressive timing all the time.

I ended up running twice more with a best of 12.35 at 116.1. The corrected mph is about what I normally run, the ET was a little off. For some reason I just couldn't get better than around 1.94 60 foot, where I normally run around 1.89's.

 

Timing is key to making hp. By you running too much though with out the proper octane not only are you losing power by making your car correct it you stand the chance of detonating and doing damage. I would back the timing out unless you know it can run it. Just my .02.

 

No, I do not run this aggressive tune without running race gas. I loaded on my street tune before I left the track. As far as doing damage? That's why the car has a knock sensor and that's why it was pulling timing.

 

The knock sensors detect detonation. Meaning for them to work you are already detonating. When the computer pulls the timing it also pulls an extra few degrees out to get it back to a safe condition.

Its good you put the street tune back on when not on race gas or you could develop problems.

 

Yes, the street tune is very safe, I never get KR.

 

Knock sensors detect knock and there are varying degrees of knock. The knock detected by the knock sensor is very light knock often referred to as "ping" which is actually the most efficient operating range of the engine and won't cause any damage whatsoever. Of course the knock sensor will detect heavy knock also (which is damaging) but hopefully the knock sensor has pulled timing before it gets to that point. Detonation is a very severe form of abnormal combustion and can be very damaging.

 

When I get KR I can not even hear pinging. And I've heard pinging on a number of engines especially back in the 80's and on my 01 Z28. I've also heard severe detonation on a friends 280ZX that we put a turbo kit on, it was not a good sound at all!!! We lowered the boost and it went away, but I was still worried that we hurt that engine.

 

Detonation is or pinging is not good anytime and it's where the combustion is happening before the plug fires. Thats why more octane
which is the resistance of the fuel to preignition or pinging is used.
The noise is the valve rattiling in the guide.
Poor fuel and too much timing are causes.

 

I think what is being said is the light pinging you get will not damage your engine, but heavy detonation will. I had an 01 Z28 that pinged from 4500 to 5200 rpm every time I went wide open. This must have been going on for a while since the car had 60,000 miles on it when I bought it. I fixed the pinging issue and when I had the heads off of it when I did some mods there was zero damage to the combustion chamber or pistons.

 

Anytime you do, you are wasting some power. So it's really best
with no pinging.

 

I bet if you had backed some timing off on unblended pump gas you'd have done the same mph...you need to be able to have a tune that doesn't pull any out...remember, your ECM takes some time to recover from pulling timing (recovery time) and it'll cost mph/ET as well.

 

Excellent point. I should have loaded on the street tune and run the first time with it, then blended the 100 octane and put in the more aggressive tune. Next time I'll try that, but it won't be until Fall, it's getting too hot already in Arizona to run.

 

You're kidding right??? Preignition refers to an abnormal combustion event before the plug fires and is very destructive...it is completely different from detonation. Knock, detonation, or pinging all refer to abnormal combustion events after the plug fires. Pinging is a term used to describe light "knock" where a small amount of end gases self ignite and forms another flame front just as the normal flame front has almost consumed the whole charge. It causes very low amplitude pressure spikes which is why the sound level is lower and the forces associated with it are not much higher than normal combustion. It consumes the charge faster than normal combustion and more closely resembles the ideal Otto cycle PV diagram which represents the combustion event as occurring at constant volume...I.E. the whole charge is consumed with the piston at TDC which of course is impossible in reality. However, the closer we can get to ideal, the more efficient the engine will be or the more HP it'll make. To give you an idea of this, the Hemi engine in a Top Fuel dragster has consumed its spark plug electrode by half track but continues to run by detonation making thousands of HP in the process...they have to shut off the fuel to stop the engine. Of course their engines are rebuilt after every round after having turned a total of only ~600 revolutions in the 1/4 mile run. Think about it, if the engine turned 8000 RPM for the whole run which lasted 4.5 seconds, that would be 8000/60*4.5=600 revolutions...pretty short life I'd say. But then again, they only have to sustain about one second of detonation...pistons and rods are considered throw aways after each run.

The noise is not "the valve rattling in the guide"...it's the pressure spikes vibrating the walls of the combustion chamber. Poor fuel and too much timing are two of the many causes of detonation.

Once again, pinging is not a bad thing...it's actually the "sound of fuel economy" as you approach the ideal combustion event. Here's a really good link posted by Jason from Katech, you'll be amazed at all the good info: