TRD/ Magnuson 4.0 Supercharger Tips, Tricks, and Mods

Had a situation come up, if anyone could chime in with an opinion - would be greatly appreciated.

I recently drove from Denver To Los Angeles. During an uphill stretch in Barstow (eastern California), I was at about 20% throttle, I was in boost, and noticed my AFR went up to 16.5. I let off the throttle, and the AFR went back to 14.x.

I dont have a boost or AFR gauge (yet), but my HU is plugged into my OBDII which can read the stock O2 sensor (which is how I could see my AFRs).

It only happened once. Not sure if I shouldn't be alarmed. Or should be alarmed, and what could the cause? Initially Im thinking the ECU isnt adjusted to the lower altitude and the higher MAF. Or my fuel pump could keep up with the demands.

There's nothing special about my setup, I do have a 2.85 pulley (to offset living at altitude in CO). Any thoughts, theories???

 

Any chance you let up off the throttle during that observance?

 

I was using cruise control, so the throttle does fluctuate.

As soon as I saw it went Lean, I hit the break (to stop cruise control), let off the gas, and resumed (with the AFRs back to stoich)

 

I suspect your cruise control "let off the throttle" and the truck entered DFCO (Decel Fuel Cut Off). Obviously I can't say that's for certain without a log, but that's what I'd put my money on.

In short I don't think you have anything to worry about. If you had a fuel pump issue you'd see your truck lean out progressively as fuel demand increased.

 

hmm...havent come across this term, I will look it up

 

Jesus. The list grows. Hahaha.

So below is a list of all the boys who want to participate in the event in any sort of way even if it's just making a pit stop by their neck of the woods.

Please correct me so I can remove you from the list of I added you by accident. This is who I am gathering off the top of my head.

1. Myself
2. @nudavinci64
3. @Murphinator
4. @garciav
5. @Torspd
6. @loginfailed
7. @SUMOTNK
8. @snowsk8air2
9. @XPOTRPR
10. @JustDSM
11. @Roostfactor
12. @BassAckwards
13. @Lucario Runner ?

 

It is Open Loop Fueling on the opposite end from accelerating when you get pig rich to protect components. When you let off the throttle it enters open loop fueling and goes way lean because the engine is still pumping air, but shut off fuel.

 

Im not saying that isnt it-but I was still going uphill and even though I was in cruise control I dont see CC letting off the throttle at that point

 

Yeah, then unless it blipped under torque management briefly shifting into overdrive potentially. Also, how do you know if you were in boost or not? There is no such monitoring capability in the ECU so beware of potential false readings from scanners (i.e. EGTs on your Taco)

 

I have a MT, so I was in 6th the whole time. I could hear boost being applied (not sure how accurate that is) so couldnt say how much boost I was in

 

I'm not a cam expert by any means but exh valve timing (actual valve timing) stock opens at 54° BBDC and closes 2° ATDC.
The retarded gears just skew that number 3° for a new exh valve timing of open at 51° BBDC and closes at 5° ATDC.

The later opening of the exhaust valve allows the power stroke to push down on the piston for 3 more degrees and the later closing of 5° ATDC allows the exhaust a little more time to evacuate the cylinder.

Since exhaust is a gas and gas has mass, then momentum must be taken into consideration.
Allowing the exh valve to stay open 3° later gives the cylinder a bit more time to empty while also pulling in a stronger intake charge during valve overlap.

Yes we are pressurized now with the sc but that also means much more exhaust mass with each power stroke and we want as much of that mass emptied from the cylinder to prepare for the intake charge.

 

That was easy.

Damn!

 

Maybe sometime this summer, I plan to try the 3° retarded gears even with the stroker and kelfords.

 

I held off on the Kelford as it was noted it may not be good for both. Def curious to see how that pans out.

 

Kelford didn't say it was bad, that stated it would move the power lower

 

So you can basically run cam gears and Kelford cams if you want to?

 

Got it. I understood it differently. With the offraod trucks moving power lower doesnt seem like a bad thing.

 

@nd4spdbh you want in on the grand taco run to Texas? Pretty sure everyone on the list is running your trans tune if they’re an auto

 

so is the consensus that i should put the cam gears in this weekend?