NZ951

B951S, Could you please post the values so I may plug them into my pcl file?

Sean Hall

B951S,
You're probably aware of this, but keep in mind your turbo probably has less back pressure then the turbos the ingnition maps you're using where set up for.
Back pressure is proportional to combustion chamber temperature, thus back pressure affects combustion chamber pressure( and temperature) significantly.

So, your timing curve will look something like this: maximum advance, decreasing until peak torque is reached, then increasing to peak horsepower.

I've got to do the same exercise with my car, so I'm really interested to see what timing values you end up with.

Rage2 posted some obersavations about his timing setup awhile back. From what I could tell, he was spot on. Might be worth a look.

-Sean

B951S

Thanks for the tip Sean, I read Rage2 posts and there is some real good advice. My approach is to try and model the stock timing and then move incrementally from there. Hopefully, with help from others, I should be able to make safe incremental changes to the pseudo stock map for the obvious operating changes brought about by the bigger turbo.

I was interested if you might speak to increasing timing after peak torque for a bigger turbo?? I think I have a good map for advance at light load and then the dip around full torque, but I think there is probably room to be a bit more aggressive top end with my turbo. My current map extrapolates the stock WOT map at 10psi and gets something like about 18 at 15psi on 93 gas. Should I run it back up to 20 or >20 after torque peak?. I may get to a load type dyno if possible but if I can get close enough to optimum wile staying safe, I will be happy.

NZ951, I sent you a PCL file with the timing table in it (the other data will not be set up so just use the values out of the table in your own PCL)
Thanks

rage2

According to Danno, the stock timing isn't agressive at all. Also remember to tune for the worse fuel possible, unless you're willing to drive far to get the right fuel (assuming it's a daily driver).

I have my car tuned to the limits of 92 octane. Most gas stations sell 91, so I'm fairly limited as to where I can gas up.

My timing maps looks something like this at WOT in terms of total timing.

38 degrees off boost
as boost increases, retard to around 22-24 degrees
18 degrees at peak torque
back up to 24 or 25 degrees at redline.

The advance near redline increases torque significantly, which allows me to make peak hp at around 6900rpm with fuelcut at 7000rpm on a stock head and stock cams. The only flow changes was an extrudehoned intake manifold.

Russ Murphy

Howdy rage2.
It sounds like your map has continued to evolve. Would you mind posting your current map? I'm always looking for ways to tweak my SDS. B951S will have to do a little interpretation, but I think it'll certainly provide some insight.

B951S

Excellent input guys, I can turn Rage's current map into reality on the link in a matter of minutes. as its a direct cell (loadxrpm table) input.
Thanks a bunch.

NZ951

Do you think that PCL you sent me will be ok to run on my car? Are you running it at the moment? Little help here before I change the values. Mine are very different from those you sent me... having said that, the valuves I have are the default Link ones.

rage2

Yep, I've made the changes actually about 6-8 months ago, and I've been running it like this since then.

Since we have quite a bit of different hardware, and I live up in the mountains at 3700ft elevation, my map would probably be useless for you. So, I'll give you something better... how to tune your standalone safely and reliably. Damn, my tuning secrets are comin' out... .

First off, get a good knock monitoring tool. You need something that can hear ANY sign of knock, even at high rpms. Don't rely on the SDS knock sensor, because if you have it adjusted wrong, it might not pick up very minor knock. You want to pick up knock BEFORE it can be heard outside the car. If you can hear knock from the engine outside your car, it's already very severe. You want to pick up knock that's normally not audible.

Next, make sure your boost controller can hold boost stable. Makes tuning 10000x easier. Also, fill your car with the gas that you want to tune on. Try to do this on a hot day... .

When you're on the dyno, set your entire timing under boost curve to 20 degrees total. Slowly turn up boost and adjust for 12.2:1 A/F ratio. Keep going until you hear the first sign of knock. It'll most likely be at peak torque in the rpm range where you will hear the knock. At that rpm cell, set timing to 18 degrees. So now your pump gas boost level is set. Why 18 degrees? From my experience, 18 degrees is the maximum retard on our motors for acceptable EGT's. Any less timing, and EGT's start becoming damaging on our valves. Of course if you run the entire rev range at 18 degrees, it's gonna be too little timing. This value should only be used at the rpm where peak tq occurs.

Now, at every other RPM level, slowly advance timing until you hear knock using your knock monitor. Once you hear knock, retard it back 2 degrees as a safety window.

Once this is all done, you'll have your personal "perfect" timing and fuel curve, and you'll notice that your tq curve at high rpms drop a lot less, and hp will climb all the way to redline.

I managed 360whp by tweaking timing curve on 92 octane. A gain of 20whp from my street tune and fairly flat 20 degree timing curve. Driving the car feels awesome, as long as I keep the car in boost (about 3500rpm), it pulls hard and even all the way to redline. Took a while of getting used to not hitting the rev limiter because I used to shift when I feel a drop in power.

rage2

Oh, almost forgot, at lower boost levels (between 0psi and your maxboost), you can start to advance the timing in that area too. It should be fairly linear, so pick a few spots, tune for it, and interpolate the timing numbers in between. Same techniques can be used for the vaccuum portions of the map too. By tweaking these areas, you can gain tons in fuel economy too, which is a bonus.

And for Russ, since SDS doesn't have a 3D map, you're probably going to see some odd timing holes everywhere other than WOT . It's not a big deal, I usually run a little more advance and let the knock sensor take care of the odd spots.

tazman

rage2 what knock sensor do you use for your tuning and where did you mount it?

NZ951

I just tried the plot that B951S modeled. I got a lot of audible knock... Have reverted back to the stock Link values, nice and safe at the moment. Anyone got a Link computer with decent timing values that would be somewhat suitable for my setup?

BoostGuy951

Rage2 you are the man. I think its unbelievable you were able to keep the torque decent so far up there in the revs with the stock cams. Keep up the good work. Did you make Peak TQ at 6900 with the stock rods and valve springs?

Duke

I believe he made peak HP not TQ at 6900.
Peak TQ at 6900 with rev limiter at 7000 would not be too good performance wise!

Russ Murphy

Thanks for your effort and insight rage.

rage2

Peak torque was constant between 5100rpm-5800rpm at around 295-300ft/lbs of torque. It dropped to 265ft/lbs at redline, and 274ft/lbs at 6900rpm hp peak. Boost was set at 12.5psi.

BTW - if I made peak TQ at 6900rpm, that would be 394whp haha. At 12.5psi and pump gas that would be pretty cool. I think with a set of properly matched cams, it can be done. Something like :

http://www.jmengines.com/camshafts.htm
Runs on stock springs too .