Just throwing a question which has been bugging me for a while ..

Assumption is
standard Evo engine
50 trim turbo / GT30 series
Octane - the best you can get
tuned for NO KNOCK

which one generally makes more ??

A very lean AFR with high boost and low timing ?? 12AFR with very low timing in the region of maybe 6-8 degrees at 7000rpms at 26psi ???

A rich AFR with high boost and high timing?? 10.7-11AFR with timing in the region of 18-20 degrees at 7000rpms at 26 psi ??

what is the max effective timing advance one can go where beyond its no longer useful?? I vaguely understand that point as BMEP??
Does anyone know where that point is on the Evo ??

 

general thought is timing is everything. You can move the afr almost a full point(from a good setting) and see very little HP change. I watched Ben of EFI university do this on a dyno. You move the timing a couple of points or more and power goes or your motor does.

As for what ideal timing is, only your hairdresser knows for sure.
From what I have gathered, knock rears its ugly head before you see a fall off of power from to much timing.

 

Yes, timing is worth more than AFR. I've seen this time and time again on all of my setups. AFR is a pretty linear thing though, you can safely experiement a bit. Timing on the other hand is much more exponential. As advance goes up and reaches the point of diminishing return cylnder pressure will go up exponentially, as will your risk.

On pump gas and aggressive boost you will generally see knock before you go too far with timing advance, but on high octane race gas you can do some damage without seeing knock. I ave seen this happen on my car and friends' cars with the 117 leaded we typically run. I prefer to tune timing on the track (cheaper than dyno, but dyno should be better) watching MPH, which is very consistent as lng as temp doesn't drop drastically over the course of the night (beginning/end of season up here). You will reach a point where you go from each degree of timing being worth about 10 hp/1 mph to going up a few degrees and seeing no gain. On race gas I've been able to reduce mph with more timing. Backing it down brings the mph back up predictably. I tend to run safe AFRs for this testing, like 11:1 on 117 octane. You want to run the least amount of timing that doesn't significantly drop power, for a good safety margin, IMO.

 

Thanks for the info kevin ..

I'm running alky with a 2.2L using a HKS GT2835R .. seems like it's making less power than it was with the 2.0L engine ..then again .. I was running ridiculous timing on the 2.0L

Should've occurred to me that I could have over advanced on the timing and basically building too much pressure

I'm running another test on which is better 50/50 meth/water or 75/25 of either .. right now just finished 75/25 water/meth .. will be starting the other when I get back

When that's done .. I'll reduce timing to see if I can squeeze more out from the car with lower timing..

Seems like the AFR number I find with a highly advanced timing hovers around 11.0:1 .. anymore and it knocks .. any less and power drops .. still wondering if I should lower the timing and run leaner AFR .. like 12s !!!

 

On race gas I've run from ~11.5:1 all the way up to 13:1 and seen less than 1 mph change in trap speeds. I don't think it's worth sacrificing timing or boost to run leaner. I also find that on pump gas I always end up back at 11:1, it just works.

 

What does your normal pump gas timing at wot look like? What should timing be at say 8k at 20 psi on stock turbo and engine? I ask because I am trapping low in the quarter and I looked at my timing maps, and at 8k, im only running 9* of timing. Isnt this low?

 

9 degrees is what the highest load level in the factory ECU will give you, for reference. The top two or three load levels are "warranty maps" as far as I'm concerned... But, that should be around 26 psi though, not 20. At any rate, I tend to mimick the 2g timing map. In fact, I spent a good deal of time porting the 2g timing map over to the AEM at one point, and it really woke the car up, especially in the midrange/part throttle areas. The 2g high load map peaks around 16 degrees. I find this typically works well on the stock EVO turbo on pump gas. I haven't been able to test it recently though, since my bollixed injector timing gave me faster times at timing as low as 7 or 8 degrees, and trap speed was super weak (107ish). Fixing the injector timing brought the power back, so now I have to get back into WOT timing testing. Only one week of racing season left, so I don't know how far I will get. When the 16 degree number was working well for me, I was on DSMlink. My best pump gas times are nothing special though, 12.3 at 111.

 

Goof info Kevin. Have you tried using ECUFlash instead of the AEM?

I think I'm towards the point of deminishing returns now with my timing maps. On the stock turbo I had it pretty well figured out and was making consistant 110mph traps on 93 octain @ 24psi of boost dropping down to 20.5psi by redline. This was w/o cams and with 18* of timing at 7k.

Things are a little different with the 35r on the car. I have start all over again but it sure is fun.

 

I have an AEM too, so Im not limited to 9*. Is there a way I could see these DSM maps? I have 280 cams and everything else, and I only trap 107 in the quarter. Its upsetting . What was wrong with the injector timing? What was causing the problem?

 

There is a recent thread in the AEM subforum where I talk about it briefly. It's a huge subject, and I'm still playing with it myself. The problem was the way the base map phased the injectors, and nearly a complete lack of any meaningful injector advance settings. AEM admits that they spent about 2 minutes on injector advance just to get it to run, and the end user is responsible for setting it up properly. It can be adjusted on a dyno the hard way, or it can be put in the ballpark mathematically. It's also important to note that injector advance is based on injector phase, if you don't know how your injector phase is setup the advance numbers won't have any real meaning. There is some info in the AEM forums, but just barely enough for me to figure it all out. I would start reading there to see if you can get a handle on it.

Edit> The timing. I have the 2g timing maps available to me because I own DSMlink as well. I am not sure that they have offered this info to the public, so I don't want to pass it around. You may be able to find it with some searching on various sites or google, but essentially at max load (which I believe equates to boost in the high teens on those cars, could be wrong though, haven't looked in a while) timing dips as low as 4 degrees around 2500 rpm or so, hits 10 degrees by 5k, and 16 degrees around 6500. I continue the trend upward to 17 degrees by 7500 or 8000 to get rid of that ridiculous flatline. Now, not everyone can get away with this much timing on the EVO/AEM for whatever reason, so you may have to lower it. But this will give you an idea of the basic shape of the 2g curve, which you can maintain by rasing or lowering the whole curve by some amount, if you wish to do so. It still is really up to you to make the timing make sense for your car. Even before road testing I spend a good deal of time unporking a lot of the factory ****ery, then spent hours road/track testing and tweaking.

 

For turbocharged cars, the two main factors for making torque at a given rpm are boost and timing, not timing and a/f.

For naturally aspirated cars, tuning is much easier. You advance timing to MBT (not BSFC, thats something else) or knock limit. For power, you want to on the rich side of stoich. The reason most engines, espsically forced induction engines run fuel enriched at WOT (lower a/f ratio) is to control heat. Extra fuel acts as a coolant (albeit a poor one compared to water) and keeps EGT's in a range that wont smoke your valves, catalysts, etc.

Now for FI cars, we have an extra knob to play with, boost pressure. So the question you should be asking is, is it better to run higher boost levels and low timing advance, or lower boost levels and higher timing advance...

This is a question that cannot be answered by rule of thumb. It is different for different engine designs (mitsu vs srt4 for example). In order to answer this question, the scientific way to do it is to do spark sweeps at various boost levels. Meaning, you pick a boost level, say 20 psi and see how far you can advance timing, look at the power curve, and try it again at say, 20.5 psi. This takes a long time, but its the only way to do it properly. The other problem you may run into is that you may make best torque at 4k rpm using 21 psi, but at 6k, you make best torque with only 20 psi. This presents a problem with mbc style boost control. Well, thats a bit off the beaten path, but you get the idea.

Boost has a point of diminishing returns, just like spark. When you increase boost, your going to get the point where you need to back off spark advance so much to avoid knock that the net effect is a loss in torque.

In regards to running "very lean AFR with high boost and low timing", you cant really do that safely. Remember, the whole point of running rich is to control temperature. Now a lot people think that when you retard timing that your EGT's go down. This is actually the total opposite of truth. EGT's go UP with less timing advance. So in other words, the less timing advance you run, the more fuel you need to use to control EGT.

So the question you need to ask, and then asnwer with testing is:
"Is it better to run high boost, less spark advance, more fuel" or
"Lower boost, more spark advance, less fuel"

 

You are correct

 

What should the air/fuel ratio be set at///////// 11.5 to 1........is this too lean and dangerous?

 

Rule of thumb:

Pump gas 11:1
Race gas 12:1

On pump gas:
EVO8 at 23 psi should be able to have 6* at peak torque and run to 20* at redline.
EV09 at 23 psi should be able to have 7* at peak torque but only needs 14* up top.

I add 2* for race gas as well as lean out the AFR one fuel point.

 

So you're saying an EVO 9 on C16 can only do 16 degrees of timing at its highest peak in high RPM?