TiVCT timing on Coyote for most power

[txcharlie]

Can anyone answer a few questions on VCT?

1. Has someone come up with a setting for OP that produces more power than any other?

2. If so, does it work the same for every application(N/A, blower, turbo)?

3. Does VCT effect spark timing?

[wbt]

Can anyone answer a few questions on VCT?

1. Has someone come up with a setting for OP that produces more power than any other?

2. If so, does it work the same for every application(N/A, blower, turbo)?

3. Does VCT effect spark timing?

It will depend on application and hardware on the car. To dial it in, it is best to put the car on a dyno and sweep the cams. Exhaust, then intake, then exhaust, then intake, etc. until you find the optimal points.

One item to bear in mind....the more cylinder pressure you make, the less timing you can get away with. You can get around this to some degree by running better fuel or fuel less prone to detonation such as e85.

[kris5597]

I agree with WBT. To optimize cam angles, you will need to bracket the cam angles. Find a good starting point for the exhaust to stay constant and bracket the intake, then do the exhaust once you get the intake dialed in. One thing to keep in mind though, changing one could greatly affect performance in a negative or positive way. Its best to take it slow until you get on a good directional path for how much advance on the intake cam and how much retard on the exhaust. More than likely, you will run way more intake advance in the midrange and dial it back up top while retarding the exhaust cam. This is very important on engines I have tuned in the past, lots of tuners don't bother with it because of complexity and time.

Kris

[AKDMB]

How much do you guys end up getting away from the stock Ti-VCT values. I think I have an OK understanding of everything but cam timing, there is a lot of theory I need to read up on before I get into the coyote specific stuff. I know that I have always heard that each header likes it's own exhaust cam timing. My question is, ignition timing builds as much cylinder pressure as we want it to, up until knock, what does Ti-VCT give us cylinder pressure wise that ignition timing doesn't? Does it just make the entire process more efficient, less resistance for the intake and exhaust air to fight? I am pretty lost on this stuff. Ti-VCT is what separates the from the boys tuning wise with these cars. I don't own a dyno so I will do my best to get everything else nailed down, then when the time comes I guess I will rent some dyno time.

[txcharlie]

It will depend on application and hardware on the car. To dial it in, it is best to put the car on a dyno and sweep the cams. Exhaust, then intake, then exhaust, then intake, etc. until you find the optimal points.

One item to bear in mind....the more cylinder pressure you make, the less timing you can get away with. You can get around this to some degree by running better fuel or fuel less prone to detonation such as e85.

What is sweeping the cams?
Would I start with a blanket value for all RPMs? It seems most tunes I have looked at have peak values on intake and exhaust, at 4k and decline from there.
I don't have the money to rent a dyno at the moment, so I'm am using my MAF #/min to measure increase or decrease in power.
Would an increase or decrease in boost change what the optimum vct settings should be?

[txcharlie]

I agree with WBT. To optimize cam angles, you will need to bracket the cam angles. Find a good starting point for the exhaust to stay constant and bracket the intake, then do the exhaust once you get the intake dialed in. One thing to keep in mind though, changing one could greatly affect performance in a negative or positive way. Its best to take it slow until you get on a good directional path for how much advance on the intake cam and how much retard on the exhaust. More than likely, you will run way more intake advance in the midrange and dial it back up top while retarding the exhaust cam. This is very important on engines I have tuned in the past, lots of tuners don't bother with it because of complexity and time.

Kris

Could you explain what bracket the cam means?
The Roush tune has all OP exhaust vct set at 15, so I guess that would be a good starting point.

[AKDMB]

Here's a little bit of info on bracketing cams

http://www.k20a.org/forum/archive/index.php/t-1020.html

[txcharlie]

Here's a little bit of info on bracketing cams

http://www.k20a.org/forum/archive/index.php/t-1020.html

Thanks! That's a lot of dyno pulls.

[AKDMB]

Thanks! That's a lot of dyno pulls.

Exactly what I said

[LSxpwrdZ]

It would be sweet if you could manipulate the WOT cam angles in real time similar to how we can on the Gen5 GM stuff...

[txcharlie]

Exactly what I said

Yeah but you didn't put the burnout smiley for effect. LOL!

[kris5597]

From what I have seen on stock maps, not including the 2015 just yet, at WOT from 3000 to redline, the coyote exhaust cam is locked at 15 degrees of retard. From there your intake starts at 40 degrees of advance and holds it until around 4000 rpm, then drops off from there. Having the intake advance a lot in the midrange is completely normal for most stock cams. This is where all the torque comes from. With VCT you are able to increase the VE of the engine.

Since the exhaust cam is locked at 15 degrees of retard until for most of the time at WOT, I would start there. With bracketing, it will go a little something like this. Without adjusting the exhaust cam, lock the intake cam at 40 degrees advance from 2000-redline, do a pull, record the results. Then retard to 35 degrees of advance, do a pull, record the results and continue backing off until the results become useless. You may even want to try 45 to 50 degrees of advance to see what happens. If your tuning a stock car, you may not find much results in the VCT, however, if you have bolt ons, you have greatly increased airflow, there should be hidden power in the cams.

As you do each dyno pull you will see horsepower higher and lower at certain points in the powerband. At this point you can go through and pick the cam angles the make the most power at different rpm breakpoints to build your VCT map. Remember, with stock cams, it is very unlikely they will like more advance at higher rpm than they do in the midrange. You will almost always see a lot advance on the intake at first and then it back off the higher the rpms go and as VE drops off. Once you get the intake VCT tables dialed in. I would play with exhaust in smaller increments, slightly less retard, like 10-12 degrees of retard, and possibly try even more retard, like 18-20. You will need to have access to a dyno, or get acquainted with the virtual dyno and how to use it.

Kris

[MikeOD]

I've got the intake cam in buddies car at 44 degrees of advance to 4000 RPM, then I retard it down to 17 degrees for 6500 RPM...not quite linear.

The exhaust cam I have at 8 degrees at 2K, coming up to 17 degrees by 4000 then back down to 11 degrees by 6500...those changes are a little more linear. That's what seemed the best to me based on street/track data, didn't dyno it yet.

I'm also targetting 0.84 lambda at full throttle and ~24-25 degrees of spark advance.

[txcharlie]

From what I have seen on stock maps, not including the 2015 just yet, at WOT from 3000 to redline, the coyote exhaust cam is locked at 15 degrees of retard. From there your intake starts at 40 degrees of advance and holds it until around 4000 rpm, then drops off from there. Having the intake advance a lot in the midrange is completely normal for most stock cams. This is where all the torque comes from. With VCT you are able to increase the VE of the engine.

Since the exhaust cam is locked at 15 degrees of retard until for most of the time at WOT, I would start there. With bracketing, it will go a little something like this. Without adjusting the exhaust cam, lock the intake cam at 40 degrees advance from 2000-redline, do a pull, record the results. Then retard to 35 degrees of advance, do a pull, record the results and continue backing off until the results become useless. You may even want to try 45 to 50 degrees of advance to see what happens. If your tuning a stock car, you may not find much results in the VCT, however, if you have bolt ons, you have greatly increased airflow, there should be hidden power in the cams.

As you do each dyno pull you will see horsepower higher and lower at certain points in the powerband. At this point you can go through and pick the cam angles the make the most power at different rpm breakpoints to build your VCT map. Remember, with stock cams, it is very unlikely they will like more advance at higher rpm than they do in the midrange. You will almost always see a lot advance on the intake at first and then it back off the higher the rpms go and as VE drops off. Once you get the intake VCT tables dialed in. I would play with exhaust in smaller increments, slightly less retard, like 10-12 degrees of retard, and possibly try even more retard, like 18-20. You will need to have access to a dyno, or get acquainted with the virtual dyno and how to use it.

Kris

Thanks Kris! That gives me a better picture of the procedure.

[txcharlie]

I've got the intake cam in buddies car at 44 degrees of advance to 4000 RPM, then I retard it down to 17 degrees for 6500 RPM...not quite linear.

The exhaust cam I have at 8 degrees at 2K, coming up to 17 degrees by 4000 then back down to 11 degrees by 6500...those changes are a little more linear. That's what seemed the best to me based on street/track data, didn't dyno it yet.

I'm also targetting 0.84 lambda at full throttle and ~24-25 degrees of spark advance.

Thanks Mike! I've seen some tunes with similar settings.

[kris5597]

I've got the intake cam in buddies car at 44 degrees of advance to 4000 RPM, then I retard it down to 17 degrees for 6500 RPM...not quite linear.

The exhaust cam I have at 8 degrees at 2K, coming up to 17 degrees by 4000 then back down to 11 degrees by 6500...those changes are a little more linear. That's what seemed the best to me based on street/track data, didn't dyno it yet.

I'm also targetting 0.84 lambda at full throttle and ~24-25 degrees of spark advance.

That's very interesting VCT tables. For simplicity sake, I always keep the VCT numbers around an even number. 45,40,35, etc. I wonder if there is really a difference running 17 instead of 15 or 20, and 45 instead of 44. Normally small changes like that don't affect anything, and my OCD would like 45 better than 44 lol. I'll have to test that when I get around to hopping on the dyno here.

Appreciate the good discussion. Let's keep it up guys!

Kris

[kris5597]

One thing I forgot to mention, you will want to work on the VCT tables after fueling and ignition is dialed in. From there, depending on how the VCT adjustmen's go, you may be able to add more timing, and your fuel trims may need to be adjusted for as well.

Dialing in the MAF voltage first could be a way to see if VCT adjustments are increasing or decreasing airflow based on large fluctuations in fuel trims. Probably not the most ideal, but could aid for street tuning.

Kris

[MikeOD]

That's very interesting VCT tables. For simplicity sake, I always keep the VCT numbers around an even number. 45,40,35, etc. I wonder if there is really a difference running 17 instead of 15 or 20, and 45 instead of 44. Normally small changes like that don't affect anything, and my OCD would like 45 better than 44 lol. I'll have to test that when I get around to hopping on the dyno here.

Appreciate the good discussion. Let's keep it up guys!

Kris

It's probably not a major difference...I was trying to keep the tables somewhat smooth...I found that if I was a little jerky with the cam tables, you could actually feel it when the car pulled...kinda like when v-tec "kicks in yo" in a Honda lol...if I kept the numbers transitioning smoother, the car seems to pull smoother.

[txcharlie]

It's probably not a major difference...I was trying to keep the tables somewhat smooth...I found that if I was a little jerky with the cam tables, you could actually feel it when the car pulled...kinda like when v-tec "kicks in yo" in a Honda lol...if I kept the numbers transitioning smoother, the car seems to pull smoother.

Makes sense to me. Kicks in YO! ROFL!!

[kris5597]

It's probably not a major difference...I was trying to keep the tables somewhat smooth...I found that if I was a little jerky with the cam tables, you could actually feel it when the car pulled...kinda like when v-tec "kicks in yo" in a Honda lol...if I kept the numbers transitioning smoother, the car seems to pull smoother.

Oh absolutely, you want the VCT tables to transition smoothly for sure. Of course, it's highly unlikely that the car would "like" a large change in VCT angle at, for example, 2500rpm- 25 degrees then 3000rpm- 50 degrees, at that point, yes I would call it VTEC if it does lol.

Kris