Non-Intercooled, Twin-plug ignition timing
 

I've recently finished my 3.4L, 9:1 CR, twin-plug engine build and am running a GT3582R at 7 psi with no intercooler.

I'm interested in any advice/numbers suggest for ignition timing under boost.

When running about 19 deg BTDC at 4000-5000 RPM at 7 psi (150 kpa) I -think- I'm hearing some pinging. A very light intermittent marbles sound coming from the engine that typically isn't present. Despite the sound, it absolutely screams through this range - though I haven't spent much time there out of an abundance of caution.

What sort of timing are you Non-Intercooled guys running?

Knock down the timing or lower the boost until it quits pinging. Every engine is different, the data of others while a guideline may not fully apply to your situation. I think it is generally accepted that those who turbocharge SC's and Carreras (higher compression no IC) run about 0.5bar boost. You don't say what fuel system you have or ignition system, those are huge influencers on what you can get away with.

Thanks Rarly - I totally agree. I'm primarily looking for some more apples-apples data points so I can determine if I'm being paranoid or not!

Fuel and ignition are being controlled by VEMS. Spark comes from 2x Bosch style 3x2 wasted spark coil packs.

This scares me. I wouldn’t sleep well knowing my expensive build was rattling because of boost

Agreed. It has driven me to post on internet forums.

I'm dialing back the heat range on the spark plugs to NGK BKR8EIX from the BPR6ES I was running, dialing back the timing to around 10 deg at peak VE/boost, and adding a touch more fuel to try and keep combustion temps dowb. Lets see what happens!

There is at least one thread in this forum on dyno outputs and engine parameters, and another one called something like the ultimate timing thread...you may want search on these types of topics and there are a lot of discussions out there. Some are twin plug and some include 3.0 and 3.2 conversions.

There is also at least one thread on EFI maps

I would pull some up for you but am typing here while I listen to work meetings at the same time (so I need to go pay more attention to work) :)

Thanks Emery,

I had previously come across those threads and used them as a baseline. I used a combo of several of the maps to come up with my baseline. Sadly - all of the maps I saw were for intercooled setups. I was hoping to catch another non-intercooled loser willing to pipe up :)

My changes seem to work for the better. I think the pinging is gone after swapping to 2 range colder plugs and reducing timing to about 11 deg at peak boost/VE. She rips!

http://forums.pelicanparts.com/uploa...1616096353.jpg

Smart to dial back timing to stop the pinging. I'd wonder about fuel too. If you're lean, especially without an IC, that could be a big contributor to pinging. Meth or eth injection could also help keep things cool.

How do your plugs look? They can show telltale signs of detonation.