Rich + More Ignition, Or Lean + Less Ignition, What Is A Safer Way To Tune?

[Rolls]

So I see mainly jap cars where they tune 10:1 and run loads of ignition, but here in Aus people tend to run more like 12:1 with less ignition timing.

What is the safer way to tune? If you have high temps due to a small turbo running at its limits, would the more fuel + more ignition be the better method due to the richer fuel charge providing more cooling to the cylinder?

What is more likely to cause detonation, higher ignition timing? Or higher combustion temps? Is it this simple? Or does it depend on many many other things?

Curious what peoples thoughts are.

Cheers

[89CAL]

I think better quality fuel in Japan has a lot to do with it.

[HYPED6]

Loads of timing and 10:1 will lower your EGT's and you turbo will love you for it.

Both ways achieve the same results. However, 12:0 with less timing gives you less room to move if you tune is not spot on.

For example, If you don't have Air temp correction in your fueling and you get a really nice cool run or air and your mixtures run hi 12's or 13's.

Or battery correction, less voltage, more injector latency, less fuel so lean mixtures.

The next step is, Set your engine up. no pinging 12:1 and hold it flat for 5 minuets at peak torque. See how long it lasts before you back off because your exhaust temps sky rocket over 1000c.

Do the same thing on the same engine with 10.0:1 and more timing with no pinging and know your EGT's aren't going over 750c.

Is either way correct, yes. Dependent on the application.

[Rolls]

So what is more likely to cause detonation, high temps due to leaner combustion or more ignition timing?

[Don Dada]

Ahhh.....Have a look here>

http://www.skylinesaustralia.com/forums/topic/337236-tuning-afrs/

[JonnoHR31]

So what is more likely to cause detonation, high temps due to leaner combustion or more ignition timing?

timing. a lot of the time you can change the afr a fair bit without any effect on knock, whereas timing will always make a difference

[HYPED6]

Both are more likely to ping If anything in the setup is left to chance.

Its not a definitive question or answer. Lets say you can have an engine that makes 200rwkw at 15 deg at 12:1. The same engine pings at 17 deg

now the same engine makes 200rwkw at 20 deg at 10:1 but pings at 22. Both are in as much danger as each other.

If it was my engine, Id look at running 10.5:1 and 17deg and make 195rwkw knowing im probably 3-4 deg from detonation, my engine is rich enough that my EGT's are low.

Every setup is different. I have seen engines that will make 0.5% power difference from going from 13:1 to 12:1 to 10.5:1. No guessing where we leave them.

I have also seen engine loose massive amounts of power from mixtures. This is where knowing what can be safely run and what cant is necessary.

Personally, I have run turbo engines making over 400rwkw very close to 14:1 because I knew I could.

On the other side of the coin, there are engine making over 500rwkw that I run in the 10's because I have too. (stock bottom ends)

Both methods are as safe as each other provided they have been setup correctly.

[Rolls]

Both methods are as safe as each other provided they have been setup correctly.

So going with that if you made the same power with both methods and had just as much timing leeway to detonation which method would you choose?

Does the extra fuel significantly cool the pistons?

[KiwiRS4T]

Knowing the answers to these questions is what makes a good tuner worth his money.

But as it happens a Japanese tuner in one of these threads said they tune rich because experience tells them that this is the way to make engines last in long races without blowing up.

[Lithium]

I would leave the ignition timing bit out of that question, the timing should be decided on case by case. Same thing goes with AFR. I am on my phone so will be a little nonspecific but I tend to use richer AFRs with increasing cylinder pressures, there are safety advantages to having quicker burn speeds but too much fuel isn't good either.

Requirements of the car owner need to be considered, rich in a race car isn't always preferable.. More because of fuel consumption reasons than anything else. ECT and IAT trim are there to help deal with high stress situations too, its up to the tuner to try and anticipate from the info the can collect to create a map which is safe, and performs to the owners requirements in all situations. Don't assume that if you see a rich mixture that its a safer tune than a leaner one, or vice versa.

[DVS JEZ]

^^^ perfect answer. Summed up. Depends on use of the car.

[GTScotT]

I'm not going to read the entire thread, and will agree with the two above that it is case by case.

I will make ONE comment, and try to stick to it being one.

It is my firm opinion that leaner tuning makes for bigger numbers, and richer tuning makes for faster cars. I do not mean this in absolutes, I mean that there is a set boundary of what works for every setup, the leaner end of the spectrum will give you nice numbers and a very happy sounding tune while the richer end of the spread may feel to have a shorter powerband yet will generally pummel through the gears instead of holding onto the revs (accepting that gear/rpm = exact speed).

I guess that's just my opinion though. Jez I will need to send you another email BTW! You may be disapointed, may not haha.

[Rolls]

An interesting reply from Pete from nistune over on the nistune forums

A *very* good question. And one I've grappled with myself. I've also noticed the same thing - Jap tunes tend to run a lot of fuel + a lot of timing.

Unfortunately I don't have a straight answer. I don't think there is one. I've tried tuning both ways and about the only conclusion I've reached is that you gotta give an engine what it wants. I've often found that SR's like to be leaned out - running them richer than 11.5:1 will usually cost you power. Although you're obviously always balancing AFR's with timing.

Other engines can be run crazy rich and still make good power.

I tend to run DE+T jobs (high comp) richer purely because they won't take any timing if you run them lean.

I think one big contributing factor is intercooler/turbo efficiency. If you're doing something to cause high inlet temps then you'll probably finish up having to run more fuel to help cool things down (read: keep detonation away). But if you're not pushing the turbo too hard and you have a decent intercooler (+ free flowing exhaust) then you'll get away with leaner mixtures. I run my mate's SR like this. He's put a lot of effort into optimising the combination of hardware on his engine and I tune it at 12.3:1. It loves this lean AFR and still runs a fair bit of timing - but I wouldn't dare go that lean on other engines that I don't know so well!

On average I'll tune between 11.5 and 12:1 unless I have a good reason to go richer/leaner. Often on track cars I'll try going richer to add a safety margin. I'll tune for say 11.7:1 and then towards the end of the tune I'll bump K constant up 5% and do a quick run. If there's not much difference in power then I'll leave them rich. Did an RB the other day that only lost 2kw by going down to low 11's. That's where I left it.

I read an interesting article on the Nissan Lemans cars once. They were running them crazy lean (with I assume highly optimised IGN timing figures!) - and doing it for 24 hours. A big ask. But you can do stuff like this when you have TOTAL control over everything. Fuel quality/consistency being number one. They'd also have detailed air temp compensation tables - as well as telemetry/logging so they could trim things out during the race if reqd. Not to mention being able to optimise things like combustion chamber design specifically for the tune they wanted to run!

At the other end of the scale are the drifters. You're often dealing with tired engines with suspect components controlling them - you just can't run that close to the edge. Combine this with owners who have little mechanical sympathy and don't know/care about about their engine and you need to add a big safety factor to your tuning.

OK, I'm raving now, so I'd best stop! What was the question again? Oh yeah, fuel vs timing. Give the engine what it wants is the bottom line for me. I err on the side of more fuel if in doubt - lower EGT's can't be bad.

You'll find that everyone has their own idea about what works though. I'll be very interested to hear from some of the guys who actually know stuff.

PL

If you are a member over there here is the link

http://forum.nistune.com/viewtopic.php?f=12&t=1995&p=14150#p14150

[rob82]

I would leave the ignition timing bit out of that question, the timing should be decided on case by case. Same thing goes with AFR. I am on my phone so will be a little nonspecific but I tend to use richer AFRs with increasing cylinder pressures, there are safety advantages to having quicker burn speeds but too much fuel isn't good either.

Requirements of the car owner need to be considered, rich in a race car isn't always preferable.. More because of fuel consumption reasons than anything else. ECT and IAT trim are there to help deal with high stress situations too, its up to the tuner to try and anticipate from the info the can collect to create a map which is safe, and performs to the owners requirements in all situations. Don't assume that if you see a rich mixture that its a safer tune than a leaner one, or vice versa.

By that logic you run more addtional fuelling at peak torque rather than at peak revs? Thats dumb - you want to increase the cooling with increaseing heat cycles (RPM) not cylinder pressure. Cylinder pressure has no bearing on any commanded equivalence ratio or Catalytic/exhuast temp model I've seen. And I've tuned all sorts from direct injection BMW's to port injected vovlo's that will run stioch throughtout the majority of peak rpm no matter the load.

This topic is quite trivial as there are so many factors about the engine design that influence what additional fuelling is required at high load/rpm.

[Dose Pipe Sutututu]

By that logic you run more addtional fuelling at peak torque rather than at peak revs? Thats dumb - you want to increase the cooling with increaseing heat cycles (RPM) not cylinder pressure. Cylinder pressure has no bearing on any commanded equivalence ratio or Catalytic/exhuast temp model I've seen. And I've tuned all sorts from direct injection BMW's to port injected vovlo's that will run stioch throughtout the majority of peak rpm no matter the load.

This topic is quite trivial as there are so many factors about the engine design that influence what additional fuelling is required at high load/rpm.

I'm going to back up lithium on this one, with increased cylinder pressure you increase heat produced, thus heating up the turbo and/or the manifold which in turns creates even more restriction (if the turbo housing is small). I find most of the knock will always appear around peak torque and not as much towards the top end.

From my opinion, Ignition is a very important thing, but we'll leave it out of the picture, lets talk about cylinder pressure and exhaust gas temps. As you approach MBT, you will notice the EGT will increase dramatically as well, when you dial in more fuel towards MBT the EGTs will stay more constant. I find with RPM increase you will not generate as much heat, even if you dial in 2~3 extra degrees after MBT because the cylinder pressure has dropped dramatically.

If you guys are bored, hook up an EGT and test it out. I won't waffle on anymore

[rob82]

I'm going to back up lithium on this one, with increased cylinder pressure you increase heat produced, thus heating up the turbo and/or the manifold which in turns creates even more restriction (if the turbo housing is small). I find most of the knock will always appear around peak torque and not as much towards the top end.

From my opinion, Ignition is a very important thing, but we'll leave it out of the picture, lets talk about cylinder pressure and exhaust gas temps. As you approach MBT, you will notice the EGT will increase dramatically as well, when you dial in more fuel towards MBT the EGTs will stay more constant. I find with RPM increase you will not generate as much heat, even if you dial in 2~3 extra degrees after MBT because the cylinder pressure has dropped dramatically.

If you guys are bored, hook up an EGT and test it out. I won't waffle on anymore

Not exactly following what you are trying to say but do you realise that the majority of cars dont have a flat torque; hence if you biased your commanded equivalence ratio to cylinder pressure you would end up having a rich midrange with a leaner topend.

Dont confuse cylinder pressure with boost pressure - in most applications they are not a simple function of one another. And adding addition timing past MBT will only add to higher chamber temps and EGT's.

[Rolls]

What does MBT stand for?

[Lithium]

I made it obvious that I wasn't writing up a full tuning guide based on my view of the world and quantified that by saying everything depends on the case. If you have tuned that much and understand MBT then think about your typical timing curve in a non knock limited setup. Keeping it basic, consider timing and fuel both are a part of the start of a burn you have created and are measuring the results of, timing defines the start of the bang, fuel defines the burn rate. Cylinder pressure, piston speed, and all sorts can affect or should be considered when punching numbers to result in a good reliable tune imho.

Odds are I either don't know what I am talking about or you will again read just the surface of what I said and decide as such (or both) so I'll shut up now.

[Dose Pipe Sutututu]

I never confuse boost with cylinder pressure. As you reach mbt, cylinder pressure increases and decreases as it pass mbt. I never once mentioned anything about boost or a torque curve being flat

[Rolls]

Odds are I either don't know what I am talking about or you will again read just the surface of what I said and decide as such (or both) so I'll shut up now.

Lithium the world isn't out to get you, try being a little bit less defensive!