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Thread: Detonation at 2000rpm only

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Posts: 11-18 of 18
2013-01-31 11:35:38
#11
if youre running little to no timing on such a simple setup and still detonating... it isnt detonation -__-
2013-01-31 12:20:30
#12
Originally Posted by blo0d
if youre running little to no timing on such a simple setup and still detonating... it isnt detonation -__-


Exactly. That's why we're so confused. Pulled the plugs yesterday and they had a fair whack of carbon and crap on them, and so did the pistons. Thinking maybe it is pre ignition being caused by the multitude of carbon deposits in the motor?
2013-02-01 07:20:25
#13
Your pinging is from too much timing.

Based on your timing map (hard to see and very blurry), you still can cut timing from 1600-2400 rpm and load cell 9-28. At those load and rpm points, you still have 22* and 15*. Take off 2* or better yet change the 22* to 15*.

Now for the most important part of the map you need to cut timing. You need to cut the timing at 2400 rpm. You may have forgot or was unaware the ecu interpolate timing and fueling. It will take in 4 cells in map and average them. Let say you are driving around at 2000 rpm and 32 load. At that point on the timing map you have 10*, but that's not what you are going to get. The ecu will take four cells/values around that point and average them. So the final timing output will be higher than 10*
Notice how abrupt your timing change is between 2000 and 2400 rpm. Good luck.
2013-02-04 19:34:50
#14
Originally Posted by niSSSdan
So, in the last week I altered the tune on my SR20VE N15 (20V bottom end, 16VE head, 11:1 comp). Gave it a bit more down low and a bit more up top. Feels really good now and not as gutless.
Anyhoo, I only increased my 1600-2000rpm timing from 10 degrees to 12. Which is bugger all. In any case I added a little more fuel to compensate.

Now, the issue is that it will ping at exactly 2000 rpm and literally nowhere else. And it will do it with minimal load, just any increase in gradient will do it. It's also regardless of ambient air temperature, at night, early morning, midday sun, whatever. It will do it.
And then it won't. If I pull up at lights and turn the car off and then back on again, pinging is impossible to induce let alone notice. Ringing it at 1800-2400rpm, nothing. No ping. Turn the car off at destination and come home and it's back! But still, only at 2k. If I downshift and get it above 2.5k it's no worries.

What do you think people? I'm thinking that my ecu may be getting a wee bit dodgy, I'm not sure what else it could be-surely can't be a fuel pump thing as it's rpm specific right?

For now I have turned the timing back to 11 degrees just incase that was the cause, but it just seems so odd to be able to be fixed by restarting the car.

Let me know what you think in any case guys, I look forward to your responses

Cheers, Dan.


I had pinging / misfire problem with my sr20ve and it was the f**ing gas, i changed garage to get my gas and now it's alright!

Put some injector cleaner and change the spark plugs
2013-02-06 17:53:34
#15
Your timing will be much higher then 10deg due to interpolation and your base timing. Hard to read but that looks to be around 20+deg. At that RPM mean piston speed is down so you could very possibly have knock with good gas.

"Pre-Ignition" is much different then detonation. You would have melted a piston if you were capable of doing so.

Tell you what, take from 2k-3.2k and drop it down 5+deg under all loads and go for a spin. This should take you 10 minutes max and tell you where your issue lies.

You are most definitely not at the fine tuning stage yet.

Another important thing you should practice is running with the laptop while driving, and using a program capable of outputting your real-time advance after interpolation and any trim tables or compensations. This is crucial to realizing where you are operating and avoiding harmful detonation. Data logging this data vs. RPM would also be key in identifying the problem in minutes if you have that capability.

Keep us posted.

Walker
2013-02-06 18:06:18
#16
i bet dude is checking his timing with a spun pulley...

i still say rod bearing.
2013-02-07 03:37:38
#17
Thanks heaps for the responses guys!
I fixed this issue just the other day by going back to a different map. It's weird because this map is leaner than the one it was pinging on. It may have been a corrupt file or some shit, it was very strange.
I'll post up the current fuel and ignition maps when I get on the laptop if you'd like to see where the differences are.

As 200_sx said, bad fuel could have been part of the problem too, car has a fresh tank and some fuel system cleaner in it at the moment.

Yeah Walker I have driven with the laptop plugged in a number of times to see where my trace is running throughout both maps, that's why it was pulled back to 10* at those low rpms as on the original base tune (designed for a normal 10.3:1 VE it was disgusting amounts of pinging at low rpm) My rings are probably well shagged by now lol...

I hope I don't have a spun pulley as it's a brand new 20V bottom end, well it has 30,000 kms on it now.

Ah well it's about to cop E85 along with a Walbro 255 and 550cc injectors in the next month or so.
2013-02-07 04:19:18
#18
Take it from me. The Sr20VE will take allot of detonation NA :offended: Don't ask me how I know. That makes these NA engines great for tuning experiments irate:.

Anyway glad you got it sorted!

Just an fyi, richer mixture is not always less prone to detonation. It is a rule of thumb that VERY rich is going to cool the charge and help prevent detonation. Just as VERY lean will cause for less heat and therefore less detonation.

It is likely richening your mixture caused you to be slightly richer then stoichiometric. You had essentially tuned for peak flame temperature which occurs in the 13's depending on the octane and a few other variables. This will lead to more knock tendency VS. a stoichiometric (14.7) burn. Coupled with whatever your timing was, could have caused for noticeably large amounts of detonation. Of course this is all blabber here since we do not know your afr's. Just wanted to give you an idea of why the "richer" mixture could have excited more detonation.

This tells me you should work to verify your base timing so you can move forward knowing what your actual timing is. I guess investigate a spun pully, and verify with your timing light. Then get back to tuning!

Walker
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