advancing timing at high rpm?
 

I was looking over my pfc maps the other day, and noticed that the timing was pretty advanced at higher rpm. If I recall correctly I remember seeing something like 20 degrees+, which seamed like alot to me. I've heard that its ok to have more advance past like 6000 rpm because the motor is under less load and it helps keep the torque up. Then again I've always believed that you wanted to retard timing under boost. Any truth to this or am I talking out of my ass?

Your correct, but your statement assumes retard from an already existing map...

If you are creating your own map (start with zeros) you're not going to program in ATDC settings at 6K RPM, but your may throw in a number that is less than what you have programmed at lower boost.
I.E. P10 will be a higher value than P20

I hope that's clear.
Eric.

Thanks for the tips Gordon.

Gordon has become the super tuner for the rx7 community!!!!! :)

Anyone want to share what they run for timing at and after peak torque? For me, peak torque is 4800rpm, I run about 10deg leading with a 10deg split at that point, from 4800 on up I advance the timing gradually to about 20deg at 8000rpm at 15psi.

LOL!!!! I'm very impressed with how much you learned in the past two years in tuning..... Now it's time to move you into the next project....secrets in motor porting.. :)

That is very interesting, I would have NEVER thought playing with the timing would yield that much more HP. If possible, can you send me one of your maps so I can take a look at your timing maps?

I know this is like asking for your bank account numbers in the rotary tuning world lol but I figured I would give it a shot!
Same goes to you Pluto ;)

anthony@rx7s.com

Thanks

Anthony

This is some good info, I hope to see some more input. I have my timing set at 14deg from 15psi thru 18psi (I run 18psi), and it stays 14deg all the way to redline. I had no idea that I might be able to raise the timing as much as 20deg after peak torque. I make peak torque at 4500rpms (352.3) and it holds pretty solid untill a little after 5k rpms, then drops off hard. Horsepower continually rises up where the torque begins to die and holds 365.7 strong untill 6500rpms, then drops to about 340 by 7500rpms. One question I have, if I were to raise my timing after peak torque, is it even safe to run 16, 17, or possible 20deg with 18psi?


Oh, and if anyone wants to send me some haltech maps, please do. I would love to look thru timing maps.
Dans3300@juno.com

Thanks a million Gordon, that helps a ton!! I'll have to plan some more dyno time when the weather cools down to see what kind of improvement I can make.

Gordon,
Why is your peak torque so high in the rpm band? Is it all in the port, or does the turbo have something to do with it?
Thanks for the timing numbers! I will bump my leading to 14 at peak torque and see what happens...

Gordon,
Does the fact that your torque stays pretty much flat between 4500 and 7000rpms have anything to do with advancing the timing after 6000rpms? From where my torque begins to fall off, 5k rpms to 7500rpms, I lose almost a 100ft lbs, I lose about 15rwhp in that range.

I have a question!!!!!

Over the years I've heard and seen it hinted around by various super tuners that you can make alot more power by tuing the split. Does anyone want to go into detail about how much power can be made by playing around with the split and how changes in split affect tq/hp and the curve? Most people just take a number like 10 and use that for thier split all the way thru the map. I know there are some black are secrets here that some of the guys arent wanting to share.

Anyone, if you dont want to post anything you can always PM me. I wont tell your secrets!!!! lol

STEPHEN

That is not high...lol

Mine has torque peak at 6950rpm ! and peak power at 7500rpm, on the dyno. On the road data logs and peak boost (torque) happen about 400rpm later on average.

In my case it is to do with the porting and exhaust manifold/exhaust housing size.

On the topic of split I am one of the few that does not run one at all (due to the ECU I use) My power on 19.9psi pump gas and full road (quite exhaust) is 472rwhp or around 540+bhp at the engine on the dyno (little higher power on road @ same settings). Oh my Spark advance is 12deg BTDC from 150kpa up with no extra advance at higher revs.

I found something interesting with my N/a the other day, my weekend beater FC seemed a bit down on power in the lower end of the RPM spectrum, so I started checking the ignition, the trailing ignition wasn't firing, I traced it to the CAS, I replaced the CAS and got trailing ignition back, I had a bit smoother running but the power was still off, I found that I had no split at idle and low RPM between the leading and trailing, the car was just kind of sluggish at low rpms, but pulled like normal after 4K....
I found the TPS was way out of wack, its setting was beyond the range screw even, giving the ecu a signal of WOT all the time pretty much, so I took the TPS off and filed the holes in the bracket and reattached it so the readings were back in range with the adjustment screw, with it set a 1v output at idle, I had regained the leading/trailing split, seems the FC's ecu looks at TP to determine ignition split, at low loads/rpm's it has split, at wot/higher rpms it has no split.
In having split back in the timing in my car, the engine is smoother and the bottom end is stronger , so even though a rotary will run on leadings alone, I have found that proper leading timing/firing does improve the tractability of the engine. Its interesting to see mazda's strategy in the timing split versus TP and RPM though..Max

I find that most rotaries dont tend to make more power with more advance, unless you are already retarding too much due to low grade fuel. in which case better fuel and more timing can give more power.
Also I find a couple of degrees of Trail timing split adds more power over firing them together, but the difference here is maybe 1% at best.

Sort of half knowing what Rice is running, I would say a flat timing curve vs rpm would be quite OK and adding more timing at high rpm wont really give more power, but would run higher risk of breaking something. This would be partly to do with a large turbo that is relatively flat in its torque at high rpm compared to standard sized turbos, and also due to the available fuel.

Don't be too eager to add more timing without knowing full well what is happening. Most 13B's I have done (100's maybe 1000's) tend to like no more than 12 to 14 degrees Lead at 1Bar boost, and almost back to TDC by 1.6 Bar. Trail I would start around 7 degrees and play from there. If you are adding more Lead timing than this you should check what is happening at the crank at high rpm and be sure the trigger is not causing the timing to retard, which would require the maps to be more advanced.

Even on high grade fuels like VP C16, by 1.6Bar I would be lucky to have it as high as 10 degrees Lead to make peak power.

On pump fuel I find running more timing either does not add power in the way it does for a piston engine, ie very small gains, but for these gains you run a much higher risk of detonation. As such I tend to rather loose a couple of HP in return for a motor that lasts under normal use and the possibility of varying fuel quality.

One thing to keep in mind is that I have seen alot of 13B's where the timing marks are different by a few degrees.

Thanks for the input HITman!!!!

OK, so lets see if I'm understanding everyone.

While under vacume according to gmonsen I should run about 20degrees then starts raising it till I'm at around 34degrees by 3000rpms (but still under vacume). Then from there start to curve it down so that by one bar I should be somewhere between 12 and 16 degrees depending on rpms and peak tq.

As I'm curving it down how fast should I drop it, in other words I'll for to go from 34degrees at 0psi down to 12 or so at say 14psi. Should I just drop it a steady 2degrees per psi of boost so that at at 11psi I would be running 12degrees then just hold it there all the way thru the rpms and up to about 16psi of boost. Would that be about right? I'm just trying to get an idea of that the curve should look like and how fast I should drop it.

Thanks everyone, this is all helping be big time!!!!!

STEPHEN

Ok, i'm getting confused. Gordon says advance timing after peak torque, the hitman says don't. Anyone else with some input gathered from the dyno that can share their findings?

I'm going to make it the same all the way across then maybe play around with it after the tq peak when I'm on the dyno.

OK, here is a question, lets say I'm on the dyno and I'm messing with timing after the tq peak. How will I know if I'm safe or if I've gone too far. In other world how do you tune the timing and know if your too far or if you can keep going? Do you do this by watching the egt and making sure it doesnt get too hot???

Thanks,
STEPHEN

Damn, I forgot to ask one other thing. Everyone mentions what timing is safe to run at bar but what about before there? What is safe from 0psi up to 14psi??? If I'm running 20-34 degrees while under vacume should I just slowly taper that off till i get to 12-14degrees around 14psi of boost??? This means I could be running around as much as 22-26 in the higher rpms and low boost like 2-6psi of boost. Would that be ok????

I'm sorry for asking so many questions guys but I'm building a map off of what you guys are telling me and I've never made a timing map before so this kind of info is a HUGE help to me!!!! I realize some of this might be painfully obvious to some of you but to a beginner such as myseft its not.

Thanks,
STEPHEN

Gordon,
Not saying anyone is right or wrong but, I have found that having the high initial(30-35deg) with a timing split up to 15 deg at low rpm does significantly add to response and low end power. The total timing on an engine at full boost seems to be relative to many factors including, turbo design, fuel quality( octane aswell as burn rate) intake charge temp and static rotor compression ratio. Turbo sizing, boost levels and fuel quality do vary from my first hand experience aus-usa. In some instances I have found gains from increasing timing after peak torque, but for customers engines would tend to agree with Hitman about the trade off between power vs risk of detonation.
Congrats- best thread I have read here for quiet some time.

Hey Anthony, you have any news for me? If you know anything yet shoot me a pm.

Thanks,
STEPHEN

GMONSEN - What has to be done to use a MSD amp??? I'm glad you mentioned that because I am just fixing to buy one for my leading coils. Is there something very involved with it that I should know about. I figured it was just a matter or wireing it in like the other amps.

Are we talking about 2 different things? I'm talking about a MSD digital 6. I was also considering buying his MSD blaster coils.

What am I getting in too?????

Thanks,
STEPHEN

"could you explain that to me? my understanding was that the greatest risk of detonation generally was in the range between spool up rpm and peak torque rpm (for me about 3000-6000 rpm). over that the pressures in the chambers is decreasing. my understanding is that the greatest risk of detonation is when the pressure in the chambers is greatest. when that decreases, the risk of detonation decreases. i think this is why more motors seem to blow up at 5000-6000rpm? if this is not right, could you please help explain to me what i am missing?"


I'm with gmonsen. I've been following pretty closely and you guys are a veritable fount of knowledge. Keep up the enlightenment. What's up with timing vs. "cylinder" pressure?

By the time your EGT tells you you're running too hot (lean) it's too late.

Well, if thats the case, how do you tune timing??? How do you know if you can safely advance more or if you need to back it down????

What do you use? I was under the impression you would use a good egt gauge. Surely its not a guessing game, there must be something to look for

STEPHEN