Chingon's Engine Build

[Chingon1]

@XR7-4.6 was the tuning with the cams really crazy?? I tuned my boosted bird but didn’t have to worry about cams in the mix, any pointers?

@Grog6 that’s too much haha we’re lucky the computer does all the work for use.



Just installed the accufab 8mm pivot pins into the block, a lil nerve racking trying to get the tap nice and Str8 but honestly it was pretty str8 forward.

Tomorrow I’m picking up the internals and hopefully assembling the short block, going to set the end gaps to 22 top ring and 26 bottom ring, I’m kinda leaning to 24 bottom but I heard it’s good to have the bottom one bigger.

 

[XR7-4.6]

@XR7-4.6 was the tuning with the cams really crazy?? I tuned my boosted bird but didn’t have to worry about cams in the mix, any pointers?

I wouldn’t call it crazy, idle is the issue. Once you’re above idle it’s just normal tuning, not n fact I haven’t changed a thing besides injector delay using the excel file I got from Brandon. But with idle if the cams have a lot of overlap it can be a challenge to keep it from stalling or surging at idle. Unlike WOT tuning the idle tuning can be done with the car parked flicking the throttle blade and datalogging.

The challenge is a wideband and fuel trims from the narrowbands aren’t necessary accurate at those RPMs since there’s so much reversion with both valves partially open so the tack I’ve taken which I don’t necessarily know is the right one is to minimize the ISC (IAC)duty cycle at desired idle to a minimum and open the throttle blade more with the stop screw everyone tells you to never ever mess with. You also want to get the idle integrator to 0 in the logs. This basically removes the IAC from the equation for idle stability and leaves it to fuel/spark.

Right now mine’s just ok. Currently I have it in forced open loop/adaptive off 100% of the time it’s running so the oxygen sensors don’t overcorrect a lean condition that isn’t there due to the overlap(I’ve tried every parameter to get it to go to OL at idle only but I’ve never been able to do it yet), but I still have ways to go and am still figuring it out. I’m probably going to end up raising the idle up from 750 now to 850 or even 900 if I’m desperate next. If it’s still a problem I’ll be hooking up a vacuum gauge and tuning the old fashioned way (albeit without the convenience of a distributor lol)

 

[Chingon1]

I wouldn’t call it crazy, idle is the issue. Once you’re above idle it’s just normal tuning, not n fact I haven’t changed a thing besides injector delay using the excel file I got from Brandon. But with idle if the cams have a lot of overlap it can be a challenge to keep it from stalling or surging at idle. Unlike WOT tuning the idle tuning can be done with the car parked flicking the throttle blade and datalogging.

The challenge is a wideband and fuel trims from the narrowbands aren’t necessary accurate at those RPMs since there’s so much reversion with both valves partially open so the tack I’ve taken which I don’t necessarily know is the right one is to minimize the ISC (IAC)duty cycle at desired idle to a minimum and open the throttle blade more with the stop screw everyone tells you to never ever mess with. You also want to get the idle integrator to 0 in the logs. This basically removes the IAC from the equation for idle stability and leaves it to fuel/spark.

Right now mine’s just ok. Currently I have it in forced open loop/adaptive off 100% of the time it’s running so the oxygen sensors don’t overcorrect a lean condition that isn’t there due to the overlap(I’ve tried every parameter to get it to go to OL at idle only but I’ve never been able to do it yet), but I still have ways to go and am still figuring it out. I’m probably going to end up raising the idle up from 750 now to 850 or even 900 if I’m desperate next. If it’s still a problem I’ll be hooking up a vacuum gauge and tuning the old fashioned way (albeit without the convenience of a distributor lol)

Interesting, those cams I’m looking at have 114 overlap I think. Which is pretty much stock numbers if I’m correct , since you have NA cams I’m assuming their aver lap is around 110-108??

 

[XR7-4.6]

Interesting, those cams I’m looking at have 114 overlap I think. Which is pretty much stock numbers if I’m correct , since you have NA cams I’m assuming their aver lap is around 110-108??

That’s lobe separation angle, though it contributes to overlap. If the intake and exhaust lobe durations are low enough you could have zero overlap regardless of LSA, (which is basically factory cams).

On 4 cam engines you can set the LSA to whatever you want, mine’s 112.5 degrees. With 230° duration on both cams and that LSA the overlap is about 5°

 

[Chingon1]

@XR7-4.6 there we go that’s what I meant. I think stock PI cams are in the 116 range, so those stage 2 shouldn’t be too far off. Did you do the pivot pins on your engine?

 

[XR7-4.6]

@XR7-4.6 there we go that’s what I meant. I think stock PI cams are in the 116 range, so those stage 2 shouldn’t be too far off. Did you do the pivot pins on your engine?

Nah, from what I’ve read over the years those aren’t necessary to upgrade until you run heavier valve springs or are running way higher RPM than I am. My cams have a lot of duration but they aren’t high enough lift to necessitate upgrading either.

And yeah I believe 116 LSA is stock for both 2V and 4V, which is more emissions friendly