dcg9381

So I'm at a point where I'm tuning timing on a 2.4L 8-valve motor. Forged pistions 8.5:1 CR.
I've got my fuel spot on per LC-1 wideband, but I haven't tuned fuel for a blown setup before and I found that by starting with the same timing map as this motor would have naturally aspirated (when not under boost) my timing was way too low and I had high EGTs that didn't do good things for my turbo (rebuild #2).

The overall question is when tuning timing, how do you know where the limit is? I understand concepts of pulling boost per PSI, etc, but setting that initial 100KPA (no boost) timing point - do you let it detonate and then back off a few degrees?

The only advice I've received off this forum is to "read my plugs" to tune timing... Either that's smoking crack or I'm simply not interested in reading plugs to determine timing...

Minor Threat

Dyno.

Det-cans.

Google?

Walter

yeah..just advance ur timing until u listen when ur car begin detonates..then retard some dregrees



plugs it's good way too for knowing ir u are runing very rich or lean

Chris Harris

If you are not interested in learning to read plugs than you arent interested in learning to tune timing. Simply the best way to know what is going on inside of the combustion chamber is to pull a plug and look at it as it is the only thing you can physically view that is in that combustion chamber during the burn...

Reading plugs and the dyno...only way.

dcg9381

So you're saying outside of the LC-1 that I've purchased from you, I still need to learn to read the plugs? I've got complete engine logging - boost, timing, A/F, etc.

Adding an EGT and I still need to have a look? Tuning 2-strokes, which I'm familiar with - proper tuning requires a new plug quite often to be able to read it correctly.


Det-can, eh? I hadn't heard of that.. Great concept. I was thinking of buying knocksense, but many posts indicate that the manual method may be better.. thanks for the tip!

Chris Harris

Yes, wideband only measures one part...Air/Fuel. The wideband will really tell you nothing about timing. EGT will get you so far but can give you false readings about your engine timing if the data is interpreted improperly.

What do you think all of those gearheads did back in the day when there wasnt electronics like there is today? They read plugs...

You can actually tell EVERYTHING about what is going on in the cylinder if you really know what you are looking at. I know guys that dont use widebands, knock monitors, etc and they SOLELY use plugs to tune everything (timing & Air/Fuel)

dcg9381

I understand that old school gearhead read plugs.. And I've done that for "old school" applications myself - like tuning 2-stroke motorcycles or jetskis.

However, I wouldn't be able to tell you the difference in 14.0:1 vs 14.7:1 (or even greater) if I didn't have a wideband.. I also understand *now* based on my own experience running too high EGTs, that I shouldn't just rely on the wideband - but if I had a wideband and an EGT gauge - is there more that can be learned from reading the plugs? How many guys doing dyno tuning as a service pull plugs after each tuning run?

Walter

i THINK reading plugs tell you if you run VERY rich or VERY lean ... i think... it's good to know that but i think with a WB you will be more accurate for to know ur A/F