Quote:
Originally Posted by CNCguy
Another yes vote for the race mufflers. They sound very good. Anxious to see what that beast will do.
I am having a hard time getting my head wrapped around what effects the cam travels will have on performance and how it is used to eliminate the EGR. The exhaust residue in the LZ9 LIM that I have suggests that, at some position, the cam timing allows exhaust to go into the intake and makes me wonder if the higher exhaust pressure of a turbo will have an adverse effect when the VVT is at max travel. Maybe... just maybe I think too damn much.
Anyway... great to see that you are making progress Joseph.
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From what I've read it's actually the advance that gives the 3900 its EGR effect and are you sure the residue in the intake is not from the PCV feed since it feeds top center of the intake plenum?
In case I didn't mention it here my cylinder pressures are all in the 213-235 range with 4 cylinders at least 220 and the last two cylinders to be tested 5 & 6 213 as a result of the cam advance.
You and I discussed some time ago a difference in the cam specs you measured vs. what Delta camshafts told me. I was given the impression the stock cam specs were a bit narrow in the LSA and that would make sense given I read in my camshaft & valve train book that a narrow LSA favors the EGR effect which could explain what you are seeing in your engine.
When I setup the engine I found that retarding the cam really isn't retarding it much at all but more like putting it in the straight up position since at TDC the intake valve starts to open just as the crank starts to turn off of TDC, suggesting the engine was cammed for peak output with the cam fully retarded and likewise fully advanced with a transition in the middle moving from idle rpm to max rpm.
My reground cam however is cut for high end performance so the intake valve doesn't open until the crank is turned a few degrees off of TDC. Before I had instances of low to no power brakes coming to a stop so starting the cam in the parked/stock position should make for a great improvement.
I'll post a video of the VVT effect at idle later. My dyno simulations show that the engine should produce 350 hp 0n 7 psi at 6500 with the cam parked and 416 hp retarded. I'll look at the simulated static cylinder pressures vs. actual later although they will not be comparable due to the associated engine speeds.
I should have test drive video today.