Hey Josh,
Adding timing can be a good way to help them come on boost. But you need to be very careful how you do it cos each turbo/engine combination has different spool characteristics. The idea is that you can actually run a lot of timing before boost comes up but then you need to remove it very quickly once boost comes up. This happens within 500 to 1000rpm band.
I learned heaps about this when tuning my mate's auto 180SX. Being an auto, the tuning in the "boost transitional" area was critical. This is an oft overlooked part of the tuning. It was only after we'd finished tuning it on the dyno and he'd been driving it for a few weeks when he rang me and asked if anything could be done about getting better response in that area. We finished up adding quite a bit of timing. Which helped a lot. He was very happy with the results.
It's also worth paying attention to mixtures here because it's where things are going from "14.7:1 closed loop" to the "11.5 - 12.5:1 open loop" power mixtures. If they hold closed loop too long it will make them feel very laggy.
PL
tuning my sr
Moderator: Matt
how much timing is alot? most timing maps I've seen run 14-17deg as boost comes on.
Here's a post from Enthalpy, the main sr rom tune gy in the U.S.
Here's a post from Enthalpy, the main sr rom tune gy in the U.S.
timing should pretty much level out over 3500 rpm, like this
for 0 boost:
500 RPM - 20 deg
1000 - 20
1500 - 22
2000 - 25
2500 - 27
3000 - 30
3500 - 32
4000 - 32
4500 - 32
.
.
.
7500 - 32
thats a good baseline to start with...rememeber though thats 0 boost...not full vacuum. the reason for having the timing increase as you get toward 3500 is that the actual time that the combustion has to take place gets relatively long at lower RPMs. so the igntion advane should be less. the burn time of the a/f mix is a relatively fixed time for a given intake pressure. so if the time of the compression stroke is getting longer due to low RPM then you want the ignition advance to be less so that you can reach peak cylinder pressures at the appropriate time (15-20 Deg AFTER TDC).
when i build my timing maps i keep 20 as my minimum timing all the way down to full vacuum but the 3500rpm value goes up to 40 or 42 deg. so it looks like this:
500 RPM - 20 deg
1000 - 20
1500 - 24
2000 - 28
2500 - 32
3000 - 36
3500 - 40
4000 - 40
4500 - 40
.
.
6500 - 40
7000 - 36
7500 - 34
the only weird change is that I like to roll off the timing in the high rpm high vacuum areas...just as a safety measure. when you have timing increasing as vaccum increases you get the equivalent of a vacuum advance distributor. very good for part throttle driving. vacuum advance is necessary for becasue the air / fuel mix is at a much LOWER initial energy state when it is pulled in at a high vaccum. all the molicules are pulled farther away from each other and thus your burn time takes longer. so you need to start the burn sooner to reach peak pressure at the correct time.
as the car comes into boost you will have boost retard...so say for an example of 1.0 kg/cm2 (14.7 psi) with .75 deg/lb retard you will need to take away exactly 11 degrees of timing. so your timing map at 14.7 psi should look like this
500 RPM - 9 deg
1000 - 9
1500 - 11
2000 - 14
2500 - 16
3000 - 19
3500 - 21
4000 - 21
4500 - 21
.
.
.
7500 - 21
the timing retards under boost for the exact opposite reason that it advances under vacuum. witht he af mix coming in at a much HIGHER energy state due to pressure you get a much faster burn rate. so you need to fire the mix later (less advance) to get peak pressure at the correct time. you can see that i would pull the timing out from everywhere. even in places that you might not ever see boost. it's more of a safeguard than anything. also it make s for very linear maps, and ones that are easy to view if you have 3-d map viewing in your EMS software (haltech e-11).
one of the things that people miss most about making basemaps and tuning cars is the linearity of the system. if you have big bumps or changes in your maps you are doing something wrong. the engine is a remarkably linear device. evene when you include turbocharging...values should always be smooth for both fuel and ignition.
Good stuff. I agree with everything he says except for the timing he's running in the mid range at full boost. SR's are very touchy here (probably because they make such good torque in the midrange = good cylinder filling).
Other engines would probably be OK with those figures but SR's are different. You need to take a lot more out in the midrange. The timing maps look quite bizarre. If you were to run 21 degrees at 3500-4000 on 14psi your SR would rattle hard enough to nearly blow it's head off! You'll need to take 8 to 10 degrees off of those figures or you'll be headed for a wallet haemorrhage.
PL
Other engines would probably be OK with those figures but SR's are different. You need to take a lot more out in the midrange. The timing maps look quite bizarre. If you were to run 21 degrees at 3500-4000 on 14psi your SR would rattle hard enough to nearly blow it's head off! You'll need to take 8 to 10 degrees off of those figures or you'll be headed for a wallet haemorrhage.
PL
I'm gonna stick with the map you gave me until i get dyno'ed with the knocklite ,but I would like to play with trying to get the turbo spooling quicker. how much did you advance the timing for quicker spool? should I just leave it alone? will it knock if I advance to much right before it comes onto boost?
Thanks so much everyone for helping me. its really appreciated.
Josh
Thanks so much everyone for helping me. its really appreciated.
Josh
Ummm - yeah. Leave it alone. There's about 10 degrees extra in there already!
Having said that, it's certainly worth checking. If your car comes on boost fast you may even need to remove some timing. Fortunately it's quite easy to hear knock in this area cos the engine isn't really making masses of noise until it reaches full boost. Should be a good way to test the Knocklite.
PL
Having said that, it's certainly worth checking. If your car comes on boost fast you may even need to remove some timing. Fortunately it's quite easy to hear knock in this area cos the engine isn't really making masses of noise until it reaches full boost. Should be a good way to test the Knocklite.
PL
Hi Ed,
Yeah, they certainly love timing. But in the midrange you gotta be really careful. 8.5:1.
It's always tempting to add more timing but it will come back to bite you if you get carried away in the midrange. You can start tipping it in again up top no probs. They'll handle 20 degrees at 14psi up top.
PL
Yeah, they certainly love timing. But in the midrange you gotta be really careful. 8.5:1.
It's always tempting to add more timing but it will come back to bite you if you get carried away in the midrange. You can start tipping it in again up top no probs. They'll handle 20 degrees at 14psi up top.
PL
