Pinging Puzzle 2.3L Digifant

[WTGPhoben]

I recently had an engine built (2.3L High Compression pistons , oil squirters, mansi ratio rockers, mansi injectors, mansi oil pump) along with a Digifant EFI (from the wiring colors, the harness appears to be from an 89). EFI was a takeoff and was assumed working, but wasn't specifically tested in any way. I have a few thousand miles on the new engine build, and overall it runs fine and passes CA smog with plenty of margin, but under certain conditions, it seems like I believe I'm getting some really bad spark knock:

- Warm Engine (180-200F oil), High load, near full-throttle 3200RPM: Sounds like light pinging 1-2 pings every second on an uneven cadence)
- Hot engine (215F oil), Moderate-load, near full-throttle 4200+ RPM: Ping on every cylinder fire.

In both cases, backing off the throttle will make it go away and pushing it again will make it come back. I run 91 octane fuel. Timing is set to the standard 35deg at 3000 RPM (AFAIK - will double check this obviously).

The above symptoms occur at sea level in warm weather. Old gas (which loses octane over time) seems to make the situation easier to trigger.. Higher altitude makes it harder (above 3000ft, I have not ever noticed it), presumably because the thinner air changes the conditions that are causing it.

Does anyone have theories on what could be happening here? I'd love to have some ideas before I just start changing stuff willy nilly or doing a full diagnostic of everything (which I don't have time for and would rather not pay for someone else to do at market rate if I can avoid it).

I will report back on any suggestions I end up trying.
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'85 Full Camper #westyjanefonda

[?Waldo?]

Larger displacement is generally associated with increased pinging/knocking. Higher compression is also associated with increased pinging/knocking. Considering you have both higher compression and larger displacement while using the same timing spec and FI as the 2.1 which does not have a knock sensor, that combination seems to explain it. Not really a puzzle, considering those factors I would be kinda surprised if it didn't ping without an adjustment to the timing.

[MarkWard]

I agree with Waldo. What was the calculated compression ratio? I’d try backing off the timing 2 degrees at a time. Do that till the knocking is not present.

[Howesight]

You can protect that high-compression engine with the model 1004-Uni.V3 knock control system from J&S Safegaurd. Many owners of older EFI and carbureted vehicles have succefully installed that system to control knock. At only $695.00, the cost of saving that engine is well worth it. I just googled California gasoline octane and just learnt that 91 octane appears to be the highest pump gas available at non-specialty sellers. Up here in BC, our Chevron stations sell 94 octane with no ethanol.

Have a look at their website (which appears overdue for an update):

http://www.jandssafeguard.com/safeguard.html

There is even a member here on the Samba who built his own custom WBX engine with high compression and a few other mods and was very happy once he installed the Safeguard system:

http://www.jandssafeguard.com/safeguard.html
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'86 Syncro Westy SVX

[DanHoug]

back when dinosaurs roamed the earth and massive displacement, high compression engines were the top predator, water injection was popular to control pinging. ain't nothing wrong with the technology, not as fancy as knock control but somewhat cheaper and still allows more ignition advance. plus it keeps carbon at bay.

back in the day, i made a crude system with an atomizer nozzle in the air cleaner and a washer fluid pump with a reservoir. it worked. would blend in some isopropyl in winter to keep the water tank from freezing. lotsa makers of system back in the day, you'll have to shop around now. here's an article on it that covers the basics:

https://www.hotrod.com/features/water-injection-august-1980-982-1190-26-1
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[DigiMatrix]

Which ECU are you using? Are you using the stock chip? I have seen a higher displacement/compression engine go lean at high load. In order to maintain 14.7:1 AFR the long term adjustment winds up to keep the engine fueled. When the WOT enrichment cuts in, the long term correction is zeroed and the WOT enrichment is added. The problem is, the fuel added by the long term correction is greater than the WOT enrichment, so the net result is less fuel so the engine runs lean => pinging can occur. Do you have a wideband to monitor you AFR? If not, you should get one.
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'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me

[dobryan]

You may want to contact Mansispeed about their EFI system. I bet they can set you up so that you'll have no issues.

https://www.mansispeed.com/


(I never want to rely on my ears to detect knocking. By the time it is pronounced enough so my ears could hear it the knock had been happening earlier too.)
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Dave O
'87 Westy w/ 2010 Subaru EJ25 (Vanaru) and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[GoEverywhere]

[4Gears4Tires]

I don't know if Megasquirt is legal in CA. So that may be a consideration.

Crazy that 91 is the top octane available, 93 would have been my first suggestion.

I would not keep running around with pinging. You will get small craters in the top of your pistons.
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'87 Syncro Ferric Oxyhydroxide Superleggera Edition
'85 Westy Sciuridae Domus Edition

[airschooled]

[MayorMcCheese]

How did you add oil squirters?

[Howesight]

I had a couple more thoughts about that knocking 2.3. First, as Dan Houg stated above, water injection is one possible solution and will not require you to reduce spark advance, either at the distributor (base timing) or with the J&S Safeguard system (dynamic spark retard).

But the other thought is that you might have a faulty crankcase ventilation unit. The diaphrgms all fail eventually. Oil fumes in the intake tract can cause knock. I was surprised that your knock was also occurring at relatively higher (say, 4,000) rpm. That suggested to me to look at oil fumes as a possible contributor. Disconnecting the breather hose connected to the intake manifold as an experiment might help determine whether this is contributing.
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'86 Syncro Westy SVX