I thought that I might venture over to thedieselplace for a change. Looks like a great forum.


I've been messing with the timing on the blue machine, and here are some of my results:


I went from 1* BTDC @ 1400 RPM to 3* BTDC @ 1400 RPM. The engine clack is noticabely louder at idle to about 1500. Beyond that, the volume and quality of the clack sounds normal. My coworker's 96 Powersmoke is still ten time louder though.

As predicted, turbo lag increased slightly, and boost levels were down by about 1/2 psi. There was more smoke throughout the rpm range, but cruising EGTs were lower by 50-75 degrees. It also feels like I picked up just a little bit of power; nothing much though.


I turned the timing down to 2* ATDC @ 1300 this afternoon. There is nearly zero black smoke unless you're really hammering down on it. Boost is very responsive throughout the rpm range, but power is down just slightly. All this at the cost of EGTs. They are much higher than desired at around 750* cruising at 60 mph. They rise quickly on any hill too.

Either tomorrow or the next day I'm going to experiment with advancing the engine to a few different points between 0 & 2.5 degrees BTDC @ 1300. I'll post another update afterward.


I am looking forward to the set of 6.5TD injectors that are on their way. http://forum.thedieselpage.com/ubb/biggrin.gif I figure that the better atomization of fuel will really help out.


I have a running record of my timing adjustments:
http://www.oliverdiesel.com/images/mt480/6.2_Engine_Timing_Figures.xls

Very interesting results. Thanks for the report!

It looks like we have a winner here.

I bumped the mark forward to 2* BTDC @ 1300 rpm. There's hardly any smoke, power is good, and turbo lag is almost non-exsistent. I think this is a good setup for an engine like mine - a conservative fuel rate and low pressure injectors like the 6.2 long style.

One thing that was of note:
I test three different positions today to find the right one, and though I moved the pump each time, the marks settled to the same place. There is no strong correlation between the position of the timing marks and the timing figure. Depending on how I jiggled the pump, I could get two timing results that were as mugh as 5* different, but at the same physical location. This just confirms that the factory-provided timing marks are a great ballpark figure for when one replaces their IP.

I'm going to get some highway miles on it, and see if the economy was affected at all.

Next up is getting some new 6.5TD injectors.

Okay, so I went on a short 200 mile round trip yesterday, and here's what I found. Ambient temp was about 95 F, and I averaged 70 mph @ 2000 rpm. Cruising boost was 3.5 psi, and EGTs hovered at 600 F.

I found that with the newest timing of 2* BTDC @ 1300 rpm I got an average of 1 mpg better economy. The first 100 mile leg has some decent hills, and economy was just under 17 mpg whereas it had previously been 16 even. On the second 100 mile leg, the road was nearly perfectly flat, and economy was 17.5 mpg. Edited by: Dieselboy