Optimum timing with Biodiesel?

[diy_fool]

I tried this over on the biodiesel section with no replys, perhaps someone over here knows something...

I was wondering if anyone has experimented with the timing using biodiesel for maximum performance. My ride is B100 most of the year dropping to B70 for the winter.

Got to install an 11mm pump this weekend and the performance is amazing according to my butt dyno. It has way more power in 3-4k rpm range. The car can sometimes break the tires loose in first gear if I mash it on dry pavement. That's with new and sticky Goodyear Eagle F1 225's. It could never do that before. My timing is now slightly retarded from nominal.

The IQ is now about 2 with smooth idle and slowdown.

The previous timing setting with the 10 mm pump was running slightly over advanced, just above the line. That's the way it was when I got the car and I never bothered to adjust it.

So I'm wondering if the performance gains are all in the pump and or the timing adjustment.

Is there a preferred timing setting running B100?

 

[Suns_PSD]

Running Bio will advance your timing a bit due to the higher Cetane.

I spoke to some scientists on the subject some time ago and they calculated that the B-20 I was running in my PSD was advancing my timing approximately .5-1 degree.

 

[Aron]

Biodiesel may reduce ignition delay, but I'm not sure how it would change timing. Timing is mechanically set, unless the engine has a common rail setup where there are an infinite number of settings for fuel injection.

If the timing was advanced it would raise your cylinder peak pressures, this setting should give you more power. If you are retarding the timing you should have lower cylinder pressures.

Just to clarify, as an example, advancing the fuel timing one degree would be a change from 10 degrees BTDC to 11 degrees BTDC. Retarding the the fuel timing one degree would move the timing to 9 degrees BTDC.

 

[diy_fool]

Thanks Suns this is the kind of information I was looking for.

My original setting was already over advanced, outside the spec limits, by a little. Running B100 would then make the effective timing even more over advanced, perhaps too much. Advancing the timing helps performance only up to some point.

The engine pulls freely now up to redline while before the excitement was mostly over at 3K.

When I get some free time I should play with the timing a bit and see what happens.

 

[Suns_PSD]

Biodiesel may reduce ignition delay, but I'm not sure how it would change timing. Timing is mechanically set, unless the engine has a common rail setup where there are an infinite number of settings for fuel injection.

If the timing was advanced it would raise your cylinder peak pressures, this setting should give you more power. If you are retarding the timing you should have lower cylinder pressures.

Just to clarify, as an example, advancing the fuel timing one degree would be a change from 10 degrees BTDC to 11 degrees BTDC. Retarding the the fuel timing one degree would move the timing to 9 degrees BTDC.

You are correct about the ignition delay. As long as one is not running Propane, ignition does not occur until the injector fires in a diesel. But higher cetane does result in peak CPs being reached sooner as the fuel burns faster. So the CP peak occurs sooner effectively advancing timing.

I've done CP testing and tuning on my 7.3 and higher CPs do not automatically create more hp. Somtimes the CP peak occurs so soon that the peak that should occur at around 4 degrees ATDC for maximum hp/ torque/ mpg actually occurs when the pistin is still coming up. This results in very high CPs and LESS hp. It also breaks parts.

I've watched a PSD truck get driven cross country for CP tuning that got 13 mpg on the way to the shop. CPs were lowered from 3200PSI occuring at 1 BTDC to 2400psi occuring at 5 ATDC. Torque went up around 90 pounds, hp up 20, and the truck got 18 mpg on the way back home. The injection timing that results in maximum torque is called MBT (Maximum Braking Torque) and always results in maximum mpg. Also, for the given power produced the least strain on the motor occurs when injection timing maximizes MBT.

MBT is not when the injection event should begin but it is where the main CP spike should occur. It is where the piston is still close enough to TDC yet the burn is really peaking out.

The text book MBT is 4 ATDC but high revving motors like less and slow revving motors like more.