CNC Machined 1GR-FE Exhaust Cam Gears (3° Retard)

How did you determine this? Crank gear is similar chain diameter to cam gear chain diameter.
Also, it has been confirmed that the URD’s ARE 3 degrees.

 

Standard in 4 stroke engines, cam turns at 1/2 crank speed. Valve events happen once (360 degrees) per all 4 strokes, which is 720 degrees of crank rotation.

 

Camshaft and valve timing theory is a deep rabbit hole, in which there are many dependencies and variables, combined with real world results not always matching theory. Although minimal overlap in theory is good, it is completely necessary in actuality.

Remember, just because there is some overlap doesn’t mean that raw fuel is being pushed out the exhaust. It takes time for the fresh air/fuel to get past the intake valve and move over towards exhaust during the overlap period. Perfection is when the incoming charge pushes lots of the chamber volumes’ burnt gas out, but doesn’t escape out the exhaust itself. But engine speed, boost, chamber volume, port flow rates and other variables complicate this.

Does anyone know the actual valve timing events, duration at 0.050”, lift, rocker ratio, etc? How much overlap exists now? I’d bet it is tiny.

 

But, But when the crank is at TDC and 3 degrees relative to that position is 3 degrees.

 

Actual URD can gear as provided by @Wild Heart

Call it 1.5 if you want to. I think we’re getting caught up in discriptions of products that are specifically not meant to be used for reproduction.

 

That cam gear will have exhaust valve events happening six crankshaft degrees later than the stock gear. I guess the quote is just written incorrectly.

The bigger question I'd like more info on is if retarding the exhaust cam actually is the correct way to go for a 1GRFZE.

Does anyone have any more info as to why exactly APR went this way?

 

I think the description is of cam angle not crank angle. Physically, when you set the timing chain and sprocket positions, the camshafts are 3 degrees retarded, from where they were. That's how I read URD's description, and I think that's how they implemented it. I totally get what you're saying, but they are describing camshaft angle despite what they say.

Having said that, I clicked on your instragram link. Nice work on the bimmer. I think this conversation would best be had with a nice whiskey! Also, we have the same taste in welding equipment, I like!

No real idea on the S/c vs. N/a argument. Seems like both engines benefit proportionally. We are dealing with variable valve timing on the intake side, so the overlap effected more by that? Does having a retarded exhaust cam just allow you to run more timing? I'm asking questions I really have no clue on.....

 

Typically, more overlap on N/A and S/C applications. Where this was built for. Improves cylinder scavenging. Which reduces the cylinder temps, and a little timing can be added. Per Scott and Allan, from APR. Also, not to be used on turbo engines. In most scenarios. As turbo configurations can pressurize the exhaust and blow back that exhaust into the intake. Due to increased overlap.

 

I can machine out some gears that are 360° of retard REALLY easily. But then that would be something you should never do.

 

Never go full retard.

 

Jig is consistent with both oem and the gears we had machined out. Oem gears on the outside pictured here. Installing some tomorrow.

 

Looking good!

 

Today is the day!

 

Gears are in and fit great. Lunch time now then reassembly.

 

Looking forward to results man!

 

I'm confused, doesn't the math work the opposite way? If 720° cam = 360° crank, then 3° cam = 1.5° crank?

 

No you have it flipped.

 

Need updates

 

One hour test drive currently in progress. Initial results are looking great

 

Test drive successful. Sending Justin current tune with before/after log files for evaluation. My initial impressions are slightly more power throughout with noticeably more in easy around town stuff say at 30-55mph. No extra vibrations or feelings from the "less balanced" cam gear that i could pick up on. Ran the truck up to 5650rpms without any issues. Knock learn is improved. Install took me some time but the machining I did seems to be very tight tolerances. I took measurements while inside to ensure any gears I produce will fit.
Cheers