Compression question

Post by **Touchdown038** » Tue Dec 13, 2005 9:03 pm

So when I rebuilt my motor this summer I had the machine shop deck the block and also smooth out the head for flatness... he said he had to take off 4/1000" off the head. I thought no big deal...

Well it's started pinging occasionally. Not too bad, just under heavy throttle.

Could this be because the decking/milling (is that the term?) increased the compression, making it so my motor won't like 87 octane crap? Or is it another reason?

For what it's worth, most of the typical sensors are new, except the MAF and the TPS. Both are assumed to be working correctly. Also, putting in 89 gas helps it a bit.

Anyone?

Post by **Chezedik** » Sat Dec 17, 2005 12:34 am

You dropped the head, and therefore raised compression. However, your stock comp is 8.6:1 so it shouldn't be a big deal. The thing to remember is that Nissan rated HP the same from 89-90. So I would suggest finding a 90 ECU and seeing if that fixes it. You will likely find that you will lose power but also ping. Anyone else have a comment?

Post by **BadMojo** » Sat Dec 17, 2005 12:30 pm

I'm pretty sure that Nissan didn't intend for the KA24E or KA24DE to run on 87 octane. When you say that 89 octane helps a little, does that mean you are still getting detonation on it?

Have you tried running 91 or higher octane?

Post by **Touchdown038** » Sat Dec 17, 2005 12:33 pm

I drove home (350 miles) yesterday on 92 octane (for some reason, midgrade was 92 at a station in eastern WA), and it did ping a little bit, but not really too bad at all. Only going uphill under medium throttle.

I was under the impression that only the DE was meant to use premium gaso, and the E could use whatever... I might be wrong though, someone correct me on that.

Post by **Chezedik** » Sat Dec 17, 2005 8:56 pm

Since you seem to ping when engine load increases, I would try a proper injector cleaner, and maybe back timing off a little. Also, it is possible that your head has been lowered more than once. You can use whatever on either. It says that 'for maximum performance' use premium.

Post by **180fan** » Sat Dec 17, 2005 9:22 pm

Dunno, my old KA24E ran fine on 87. I suspect there are other things causing it. Have you checked the timing?

Post by **Chezedik** » Sat Dec 17, 2005 9:26 pm

If the E is like the DE then changing timing is not done by accident. It is easy to mess up distributor timing, but changing base timing is the key. Still, all things considered, do check your timing with a light.

Post by **Touchdown038** » Sat Dec 17, 2005 11:05 pm

Checked it today, it's at about 17 degrees... I'm gonna set it at 15 tomorrow and see if that helps. The injectors could possibly be dirty, seeing as how they came with the old engine and I dunno when they were previously replaced. I would really doubt that the head has been lowered more than once, so I'll try the cleaner (I run it occasionally) and try messing with the timing as well.

Post by **Chezedik** » Sat Dec 17, 2005 11:25 pm

No, what I was suggesting with the injector cleaner was that the combustion chamber might have some carbon build-up that is heating up and causing ping. But bad atomization can cause ping, too.

Post by **Touchdown038** » Sun Dec 18, 2005 12:46 pm

I would really doubt that the combustion chamber has major enough carbon deposits to cause ping already, since I just rebuilt it 4 months ago... but there's always a chance I guess.

Post by **Chezedik** » Sun Dec 18, 2005 1:47 pm

Yeah, 4 mos probably isn't enough time. I would say check the timing.

Website · Post by **s13sr20chris** » Sun Dec 18, 2005 2:00 pm

considering the small compression increase i would say that is not the prob. i believe you have a air/fuel or ign problem. drive it under load to where its pinging for a good while. while its pinging really good, shut the motor off and coast to a stop. hop out and pull plugs. note the condition.

also, are you using good plugs? whats the heat range?

Post by **Chezedik** » Sun Dec 18, 2005 4:17 pm

What would he hope to see?

Website · Post by **s13sr20chris** » Sun Dec 18, 2005 4:26 pm

maybe one plug is damaged or defective. shoot i dunno. it could show which cyl is messing up.

Post by **Chezedik** » Sun Dec 18, 2005 5:20 pm

Fair enough.

Post by **Touchdown038** » Sun Dec 18, 2005 6:15 pm

They're new plugs, not sure of the heat range but they're stock NGKs looked up on the computer at Napa. Don't remember the number exactly... I could try this and see if there's any deposits or anything I suppose...

Post by **Chezedik** » Mon Dec 19, 2005 9:50 am

They should be BKR5E-11, if you would like, you could go to the BKR6E-11. This could help your ping problem.

Website · Post by **s13sr20chris** » Wed Dec 21, 2005 5:27 pm

yeah, 6 is good. the idea is that you want to see what the plug looks like while its pinging. the plug will clean itself up after that. i read that trick in an oldschool honda hop up book a long time ago. i have never used it but its been in my back pocket just waiting.

Post by **S13inBatnRuge** » Fri Dec 23, 2005 8:01 pm

will the bkr6e-11 work for the ka24de motor?

Compression question

Compression question

Re: (Chezedik)

Re: (Chezedik)

Re: (Chezedik)

Re: (Chezedik)

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