Warmup and Aggressive MIVEC Maps

[tephra]

thanks Bryan - wanna post a nice Exhaust map for stock turbo/cams?

[HB Speed]

Originally Posted by GST Motorsports

Retard the exhaust in balance to get it to spool even better but you can go too far and make the stock turbo surge like a son of a ***** as well.

26psi @ 2800 rpm!! in 3rd! Surging like a mofo

[GST Motorsports]

Originally Posted by tephra

thanks Bryan - wanna post a nice Exhaust map for stock turbo/cams?

little retard at peak boost (-1/-2) then I taper off to 0. I've tried hard to see if retarding up top work at all on stock turbos, so far, no fun.

running about -15/-20 at cruise seems to work well on the mileage.

[tsitalon1]

Dumb question:

There is no way to cause valve/piston contact with mivec configuration right? If I get wild in my trials I can't damage the motor aside from the normal watching of knock and a:f right?

[Hiboost]

Originally Posted by GST Motorsports

little retard at peak boost (-1/-2) then I taper off to 0. I've tried hard to see if retarding up top work at all on stock turbos, so far, no fun.

running about -15/-20 at cruise seems to work well on the mileage.

Well those Intake MIVEC numbers are quite a bit higher than mine, good to see that I wasn't overly aggressive in my changes based on you getting compressor surge on the stock turbo! I'm haven't started to try and tune the MIVEC for the GT30 turbo but I already have some compressor surge cropping up at 3400-3800 rpm in 5th gear so I'll have to avoid making it worse in that area and maybe only try more aggressive settings at lower RPM's.

Is it safe to say that when you are changing the MIVEC that being right on the edge of inducing surge in 5th is about as much spoolup you want to induce with MIVEC changes?

[Hiboost]

Originally Posted by tsitalon1

Dumb question:

There is no way to cause valve/piston contact with mivec configuration right? If I get wild in my trials I can't damage the motor aside from the normal watching of knock and a:f right?

I'm pretty sure it will start tripping error codes if you enter numbers that are too high and only adjust your cams to whatever the safe limits are. Now if you have different cams or running the car at higher than stock RPM's I would be somewhat more carefull. Likely 35* Intake Advance is about as high as you can go if I remember correctly and you wouldn't want to run that at higher RPM's since you would likely lose power.

[nj1266]

Originally Posted by GST Motorsports

You can try something like this as well



Retard the exhaust in balance to get it to spool even better but you can go too far and make the stock turbo surge like a son of a ***** as well.

Can you use this map w/o retarding the mivec exhaust map?

[BigT]

What do you do to the tune to offset aggressive mivec settings? Lower ignition timing at peak torque? Keep AFR's richer?

[BigT]

I'm not sure if I didn't create a good exhaust map for your intake map, GST, but according to VDR, I lost power all the way across the board compared to a modified JDM map that I was using. It did spool maybe 200 rpm quicker, 25psi at 3300 rpm, but the boost dropped off a lot quicker. I'll be doing a substantial test this weekend after I install a GST boost pill and DTM fmic.

[Hiboost]

Originally Posted by BigT

What do you do to the tune to offset aggressive mivec settings? Lower ignition timing at peak torque? Keep AFR's richer?

For my I just removed 1-2 timing during spoolup areas under boost, torque peak maybe a 1 degree was all I needed to adjust. AFR's generally can be kept at 13.0 tapering down to 12.0 @ 20 psi which should aid spoolup as well.

I'm not sure if I didn't create a good exhaust map for your intake map, GST, but according to VDR, I lost power all the way across the board compared to a modified JDM map that I was using. It did spool maybe 200 rpm quicker, 25psi at 3300 rpm, but the boost dropped off a lot quicker. I'll be doing a substantial test this weekend after I install a GST boost pill and DTM fmic.

It seems odd that boost dropped of quicker, did you do multiple runs to verify the changes on the same day in "Virtual Dyno Room"? I'm still not getting consistant results from that program, could be it just needs more data points. I'll let GST comment on how that map may have effect your pulls compared to the JDM maps.

[BigT]

Also, I want to add that I started a pull in 5th at 2000 rpm and right around 20psi it started to surge like crazy. However, it did hit 25psi by 2700.

[GST Motorsports]

Originally Posted by BigT

Also, I want to add that I started a pull in 5th at 2000 rpm and right around 20psi it started to surge like crazy. However, it did hit 25psi by 2700.

haha yup see my warning in my earlier post.

The map I posted is just a quick idea of what you can try out, it's not a "set and forget" map but rather a map that needs to be tuned for, might not work for your current mods, etc. Yes it will drop your boost level if you are using the same WGDC as a "less aggressive" map.

It's very close to the map that I used for this comparison: Mivec advantage?

[BigT]

hopefully this weekend i'll be able to log a few different mivec maps: gunzo, hiboost, gst, and another map that pete from dgmotors helped me create. i'll post different vdr graphs of each map and lastly a fully tuned map. i know vsr might not be completely accurate, but i'll be doing the runs on the same road and we should have a decent comparison.

[Hiboost]

Originally Posted by BigT

hopefully this weekend i'll be able to log a few different mivec maps: gunzo, hiboost, gst, and another map that pete from dgmotors helped me create. i'll post different vdr graphs of each map and lastly a fully tuned map. i know vsr might not be completely accurate, but i'll be doing the runs on the same road and we should have a decent comparison.

That would be great to see! I'll be testing some different intake cam settings on the dyno on Tuesday. There are some ideas that dropping the intake cam advance down a bit earlier, 5000 vs 6000 would help power, only one way to find out!

For larger turbos I think that slight exhaust retard on the top end might help as well. Anyone find a good article about tuning for mid range and top end power with intake and exhaust cam settings?

I know in general:

Retard exhaust/advance intake for spool

Reduced intake advance for top end power

[Hiboost]

I found this post that may explain things a bit better:

http://www.galantvr4.org/ubbthreads/...age=12&fpart=1

Dialcaliper wrote:

Cams and valve timing are actually affecting your effective compression and expansion ratios (which are quite different from the static compression ratio of your pistons). In a "theoretical engine" your cam would have a tiny 180 degree duration and instantaneous ramp rates (the valve opens to its full height immediately), and the intake and exhaust valves would open and close at the top and bottom of the stroke.

But because the air has inertia, and you can't open the valve immediately with a cam, you need to open the valves earlier so that the air starts moving before the piston starts down, and close them later so that you have the valve open while the air is still moving. You can also overlap the valves so that the air moving out of the exhaust "sucks" air in from the intake to get it started moving faster (aka scavenging)

All of those events mean that the actual compression ratio is never as high as the "static CR" of the pistons. This is why longer duration cams allow you to run more timing advance (because you've actually dropped your compression ratio even more). Alternately, you can bump the static CR ratio up higher to get back some of the actual CR that you lost. The longer duration the cam, the higher the static CR you need to get the same "actual" compression. (This is why people get away with running CR's of 9.0-10.0 while using large cams, but the same CR with shorter/stock cams are more likely to have detonation problems).

The general effects (broken down) are as follows:

Advance centerline (both cams): powerband moves to lower RPM
Retard centerline (both cams): powerband moves to higher RPM

Increase overlap (retard exhaust, advance intake): Sharper (higher) power/torque peaks, narrower powerband
Decrease overlap: (advance exhaust, retard intake intake): Flatter power/torque peaks, broader powerband
You are basically balancing valve opening and closing events to trade between stroke efficiency, effective compression (and expansion) ratios and cylinder filling efficiency.

Since the intake valve closes after the bottom of the intake stroke, closing the intake valve earlier gives you a longer compression stroke, and higher peak cylinder pressure.

But at higher RPMs the valves are open for a much shorter period - with the later intake opening there is not enough time for the cylinder to fill so the peak pressure actually drops off.

Likewise, the exhaust valve opens before the bottom of the exhaust stroke, so opening the exhaust valve later gives you a longer more efficient expansion stroke.

But at low RPM the exhaust valve closing later (while the intake valve is open) causes some of your intake charge to pass through the engine, and get vented into the exhaust manifold.


When you just move one gear, you're making two different adjustments, which can be good for specific situations. Advancing or retarding the intake gear only is an effective way to adjust engine behavior, without really messing everything up.

Advancing the intake gear simultaneously moves your powerband lower by moving the advancing the centerline (towards the RPM range of your turbo spoolup) and increases overlap, increasing the airflow at that point - you allow more air to pass out of the exhaust valve, helping the turbo spool and giving you a stronger, but peakier midrange. Obviously this ends giving you a up costing you on the top end because the earlier intake close reduces cylinder filling.

Retarding the intake gear simultaneously both moves your powerband higher (keeps the intake valve open longer) but also increases your compression and peak pressure, making the powerband broader and more drivable. You lose a little potential power due to lost overlap, but give the engine better manners in the mid to top end.

As you might guess, there's a lot of stuff going on, and a lot of compromises being made. The only way to really find the best setting is to decide what you're trying to do, and try adjusting a couple degrees at a time until you find what you want. There's no ideal setting for every part of the powerband (This is why variable valve timing is such a brilliant idea - you can, with certain limitations, find a more ideal setting for every part of the powerband)

Smaller turbos like advanced, shorter duration cams because they run out of breath up high, while big turbos are better with retarded, long duration cams because they spool up much later, and produce more power at the top end.

To make it even more complex, the cam settings on a turbo engine will vary based on where your turbo hits its sweet spot, and what kind of characteristics you're trying to get out of it. OEMs tend to put shorter cams with a peakier low end with small turbos, because you can make up for the loss at the top end by simply adding boost and throwing in taller gears. They do the same thing for auto transmissions. N/A MT cars tend to run higher RPMs, longer duration cams for more power, and shorter gearing. Ironically, cars with bigger turbos get tuned more like N/A engines.

Another sidenote is that a in a stroker engine, displacement is increased, but the valve events are happening at the same RPM as a normal stroke, you're just trying to pull more air in. As a result, the stroker will like a bit more cam duration and earlier valve opening due to the piston speed, but less overlap is required. This in turn gives you the characteristic of a broader torque band at lower RPMs (in addition to the increased torque from crank length). Likewise, it has a harder time breathing up top.

I guess I didn't really answer the question, because there's no "perfect" setting, but if you understand a bit about what's going on, you can experiment and find one you like with any type of cam.