Which makes more power- leaner burn or more ignition timing

[Visco]

I have been looking over flashes from various tuners and am not sure I can figure out what the best philosophy is for the Evo 4g63-non mivec.
Are there any general estimating rules for determining the power increase based on fuel trim versus timing points?


For street/light track use. Stage 1 mods.
91 CA pump gas.


Is it run as lean as possible (11.5 -12.0) an dial back some timing advance?
Or run it pretty lean (11.0-11.5) and advance the timing?

For safety reasons, the ECU should pull tiiming if knock is encountered with either tuning philosophy.

[littlejap33]

isnt it scarier to run lean? but i heard it makes more power but u get higher knock

[earlyapex]

Ask 5 people, get 5 different answers.

For 91 octane, without driving the car in a bubble, you should aim for high 10's, low 11's

Depends on timing, boost level, flow mods, intent of driving, sensitivity of car, etc etc

[BHCevo]

+1

The answer is: it depends.

Don't forget boost is the third variable here. You really have to juggle all three.

On my car, I found that going richer really didn't enable me to increase the timing that much. On the otherhand, if I went toooo lean then at some point my timing needed a huge retard in order to keep knock under control.

Neither extreme was good for power or drivability.

So I basically run as lean as I can while still getting "acceptable" timing advance. And I haven't even started talking about how I chose boost.

Good look finding what the torque is as a function of four independent variables: boost, timing, AFR and engine speed.

[Visco]

It seems that everyone likes to run about 22psi peak (3rd gear) on stage 1 mods. I assume that tuners have enough data to somewhat optimize that parameter of the equation.

I guess that the simple answer is to initailly decide on the A/F ratio that you want to run, tune to it and alter the timing advance to fit.

If these decisions are made early then there really is no tradeoff of A/F versus timing.

[Skiracer]

Every car behaves differently. So, it would be hard to make a blanket statement regarding each car's character.

[leaveit2bevo]

isnt it scarier to run lean? but i heard it makes more power but u get higher knock


um no, the more knock the more timing pulled=less power.

[SpoolinEVO]

Generally speaking there is only one way to find out and thats on the dyno. Working in a dyno shop, I learned that there is one sweet spot for both fuel and timing and thats where it makes the most horsepower. For boosted cars like ours the only way to do it is set a given AFR ratio like 11.2-11.5 and set peak timing to a conservative level. Watch the power increase, decrease, or stabilize by increasing or decreasing AFR, then slowly in 1-2 degree increments do the same for timing. Once the changes become less noticeable, you've found its sweet spot.

[vortech_g35]

GT42...

[trinydex]

theoretically speaking you want to run as little timing advance as possible. igniting the fuel mixture far before the piston is at tdc is making the motor work against itself (there's tons of complexity in this subject that i'm going to prefer to wash out in favor of this generic rule of thumb), is bad.

[DR MOSS]

effiency is key. a happy medium between fuel AFR and degrees of spark at a given point.

[nj1266]

Another point that you have to take into consideration is combustion chamber design. The Evo has a very old combustion chamber design that does not lend itself to very lean AFRs. More recent turbo motors like the Ecotec or the BMW can run as lean as 12:1 by redline in part due to direct injection and in part due to combustion chamber design that allows the fuel mixture to burn quickly and effeciently. A faster burning flame front has less of a chance to self ignite under boost/heat.

[in-n-out-310]

Where are the real tuners at? I wanna hear their input.

[trinydex]

Another point that you have to take into consideration is combustion chamber design. The Evo has a very old combustion chamber design that does not lend itself to very lean AFRs. More recent turbo motors like the Ecotec or the BMW can run as lean as 12:1 by redline in part due to direct injection and in part due to combustion chamber design that allows the fuel mixture to burn quickly and effeciently. A faster burning flame front has less of a chance to self ignite under boost/heat.
does any of it have to do with compression?

[BHCevo]

You can get away running lean(er) at redline because high RPMs suppress knock.

You need enough uncombusted charge in the cylinder for long enough to knock to start....high engine speeds shorten the time window that knock can occur in.

Some good papers from that MIT group show this result rather conclusively. Everything else being equal etc...

[BHCevo]

Implementing direct injection forces a significant combustion chamber redesign...for obvious reasons.

In any case, the cylinder cooling effect of direct injection seems to be the dominating factor in turbo applications, allowing for more compression, more boost or a combination of the two.


In DI, the gas droplets undergo vaporization entirely inside the cylinder, with the hot cylinder itself supplying the enormous latent heat of vaporization needed for the liquid->vapor phase change. Thats some good cooling.

In port injection, much or all of this vaporization occurs outside the cylinder and thus the cylinder cooling effect is much smaller.

[trinydex]

my question (possibly not regarding what bhc has said about di) is, isn't it true that higher compression motors run leaner when boostin?

[Mellon]

I like 11.2 on 91 octane @ 21psi and as much timing as it can handle without knocking for best power. anything in the 10's afr will seriously kill power regardless of how much timing you try to throw at it.

[SoCalRedLine]

fwiw... im running spool 12.1, to 11.7 (now with the colder air temps) to 11.1 @redline with about 14-15° of timing advance.Â* not getting any constant knock... only sporadic 1-2 counts here/there...

...all on stock boost.

[WOT]

I like 11.2 on 91 octane @ 21psi and as much timing as it can handle without knocking for best power.
this is what i shoot for as well on my car.....safe power....

just eliminate as much back pressure within the exhaust system as possible & you'll be able to add more timing...then you'll have to add more fuel to maintain your 11.2 traf, as your making more power!!

[SoCalRedLine]

^thats pretty much what ive gotten. The hotter air from more boost, and the turbo going towards its limit of efficiency... you wont be able to run as lean or as much timing without risking detonation.

adding water/meth inj, you can gain back some of the timing, and help prevent detonation.

...im also running the VVT map Neji posted.
Mods:
HKS dropin
Tanabe
RRE HFC
Muffler delete (like dl_EVO's, i convinced him to buy that one)

p.s. you guys did a great job tuning DL's car, he is pretty stoked...

[Mellon]

fwiw... im running spool 12.1, to 11.7 (now with the colder air temps) to 11.1 @redline with about 14-15° of timing advance. not getting any constant knock... only sporadic 1-2 counts here/there...

...all on stock boost.



Yea makes sense on stock boost. You can run about that timing with the boost tapering the way it does. Once you start flowing a bit more with boost control,etc, the timing needs to come down up top to make it more consistant. 9-10* at 7k is the norm.

The 8's can run a bit leaner mixture than the 9's can from my findings. Same with timing. The 8's can run a bit more timing up top compared to the 9's with the same mods.


weird, I'm able to run at least 2-3* more timing on the 9's, perhaps it's a difference in the MIVEC map.

[SoCalRedLine]

^(its cause hes biased towards 8's.... shhhhhhh...lol)


...j/k

[Mellon]

lol, I am too but it's hard to deny that the IX is better out of the box and mod for mod.

[SoCalRedLine]

^true... advantages of waiting... as with any 'tuna' car they save the best (bells & whistles) for last...lol

[nj1266]

fwiw... im running spool 12.1, to 11.7 (now with the colder air temps) to 11.1 @redline with about 14-15° of timing advance. not getting any constant knock... only sporadic 1-2 counts here/there...

...all on stock boost.

Wait until you up the boost and run 19 psi by redline. then you will have to pull timing down to 10-11* by redline. Your AFR would need adjusting after you up the boost, but I would still target the AFR that you have. I would even target 13-12.5 during spool up.

[nj1266]

this is what i shoot for as well on my car.....safe power....

just eliminate as much back pressure within the exhaust system as possible & you'll be able to add more timing...then you'll have to add more fuel to maintain your 11.2 traf, as your making more power!!



Bingo...The ticket is to eliminate all back pressure on a turbo car. I see no point in running an O2 housing, for example, and then running a high flow cat. Either run an O2 housing with a tes pipe or do not run one at all. I wish I can run my Evo w/o an exhaust at all.

[nj1266]

Yea makes sense on stock boost. You can run about that timing with the boost tapering the way it does. Once you start flowing a bit more with boost control,etc, the timing needs to come down up top to make it more consistant. 9-10* at 7k is the norm.

The 8's can run a bit leaner mixture than the 9's can from my findings. Same with timing. The 8's can run a bit more timing up top compared to the 9's with the same mods.


That is scary....I replied to Redline w/o reading your post and now I find that we recommended almost the ame timing by redline. :twisted:

[WOT]

this is what i shoot for as well on my car.....safe power....

just eliminate as much back pressure within the exhaust system as possible & you'll be able to add more timing...then you'll have to add more fuel to maintain your 11.2 traf, as your making more power!!


Bingo...The ticket is to eliminate all back pressure on a turbo car. I see no point in running an O2 housing, for example, and then running a high flow cat. Either run an O2 housing with a tes pipe or do not run one at all. I wish I can run my Evo w/o an exhaust at all.
backpressure is additive....

once its there, it doesnt disappear. in your o2 example above, i would think that a o2 housing would still be beneficial with a cat....you just wouldnt see the same gains as if you were running a test pipe.

in all the turbo testing i have done, a large short tailpipe from the turbo is best = minimized backpressure.

power goes up to when the exhaust is exiting into a low pressure area or in a rea where the exhaust is being extracted vs. high pressure area of the car

[leaveit2bevo]

that why we need the wot spec 02 houing/DP!!

[WOT]

^ i am working on it.

[atlvalet]

I see no point in running an O2 housing, for example, and then running a high flow cat. Either run an O2 housing with a tes pipe or do not run one at all. I wish I can run my Evo w/o an exhaust at all.


Or you can run one of my 100cell race cats :) They're as close to a test pipe as possible without killing trees and small children.

[Mellon]

I had a muffler shop once tell me my car would be faster with a cat because engines need backpressure hahaha. I think what he failed to realize is that we already have a massive exhaust restriction...the turbine fins!

[nj1266]

I had a muffler shop once tell me my car would be faster with a cat because engines need backpressure hahaha. I think what he failed to realize is that we already have a massive exhaust restriction...the turbine fins!

On NA cars exhaust pipe sizing is beneficial to power production. Too large an exhaust pipe and you will lose power. Too small an exhaust pipe and you will choke the engine. I laugh when I see reglar NA Honda civics with 3 inch exhaust piping.

[nj1266]

I see no point in running an O2 housing, for example, and then running a high flow cat. Either run an O2 housing with a tes pipe or do not run one at all. I wish I can run my Evo w/o an exhaust at all.


Or you can run one of my 100cell race cats :) They're as close to a test pipe as possible without killing trees and small children.

post a link please. I would like to see one.

[Mellon]

I had a muffler shop once tell me my car would be faster with a cat because engines need backpressure hahaha. I think what he failed to realize is that we already have a massive exhaust restriction...the turbine fins!

On NA cars exhaust pipe sizing is beneficial to power production. Too large an exhaust pipe and you will lose power. Too small an exhaust pipe and you will choke the engine. I laugh when I see reglar NA Honda civics with 3 inch exhaust piping.


I think it's mostly low end torque that the NA cars have to worry about with oversized exhaust but don't quote me on that...I try to learn as little as possible about NA cars :)

[nj1266]

I think it's mostly low end torque that the NA cars have to worry about with oversized exhaust but don't quote me on that...I try to learn as little as possible about NA cars :)

You know what I did not like turbo cars before I owned the Evo. A lot of my friends installed turbos on their SR20 powered cars, but I never understood the attraction. Now that I have owned a turbo car, I really get it. I do not think that I can own an NA car again. I am really thinking about adding the new Cooper S to my car collection. I love that little car.

[Mellon]

there are a couple of Cooper S wearing some fools out at the local Autox...I couldn't belive it.

[atlvalet]

Or you can run one of my 100cell race cats :) They're as close to a test pipe as possible without killing trees and small children.

post a link please. I would like to see one.



The one on the left is 100 cell. THe one on the right is 300 cell, like the ones Random Tech makes.

Just a note, the housings will be slightly different but the cores will be the same. mrfred from EvoM will soon be running one and so will Smack from NorCalEvo. I am in the middle stages of getting these produced. Bryan liked them and they hold boost almost as well as a test pipe, minus the watery eyes factor :)

http://i188.photobucket.com/albums/z230/atlvalet/300vs100.jpg

[WOT]

WOW- the cats your about to offer look amazing.

[TeKiZeRo]

Atlvalet, when do you think those will be in full production? I would love to get my hands one one. I hate the feeling of slowly dying in my car whenever I have to stop :).

[Mellon]

there are a couple of Cooper S wearing some fools out at the local Autox...I couldn't belive it.


Haven't been to many autox's then eh? ;)


I rarely miss one around here

[atlvalet]

Hopefully in the next month or two :) These will not be made in China :)

[TeKiZeRo]

Are you going to design it to look like a TP or a cat? :)

[trinydex]

I had a muffler shop once tell me my car would be faster with a cat because engines need backpressure hahaha. I think what he failed to realize is that we already have a massive exhaust restriction...the turbine fins!

On NA cars exhaust pipe sizing is beneficial to power production. Too large an exhaust pipe and you will lose power. Too small an exhaust pipe and you will choke the engine. I laugh when I see reglar NA Honda civics with 3 inch exhaust piping.
it is dangerous so make this generalization. you will not lose power if your exhaust is too big. you'll lose power on the low end and gain power on the high end. however if your car does not have the revs to get to where the power increase is shifted then that's like putting cams that have too much lift for your stock head, no additional benefit and much increased complications and shortcomings.

[trinydex]

Hopefully in the next month or two :) These will not be made in China :)
have you been testing these hard in roadrace conditions at all? i would get a cat but i'm afraid i'd melt it. i spit fire regularly from my car in those high load situations at partial throttle where my bov opens.

[awdnottwo]

Around here it usually the supercharged miatias that beat up on everybody at the auto-xes.

[atlvalet]

I know these have been used in SCCA autocross races, and possibly HPDE's...but I can't give you hard data. Smack from NorCal will have one soon, and I know he beats on his car. So, soon, he can give his feedback.

Since the catalyst is metal, I'm not sure if you could melt it...but anything is possible.

I could make these look like the RRE rally cats, but that would be extra. Right now I am just focused on getting these produced. Target pricepoint is $250, including 2 gaskets with fire rings. You should be able to use existing OEM bolts. O0

[trinydex]

don't make it look like a rallicat. make it look like a stock cat :]

are you gonna call it the valetcat :]

[atlvalet]

I think I am going to call it the 8/9 Design Race Cat :)

[mhgsx]

I think I am going to call it the 8/9 Design Race Cat :)


Does it clean well enough to keep the CEL away??

[atlvalet]

I think I am going to call it the 8/9 Design Race Cat :)


Does it clean well enough to keep the CEL away??


I don't think cleaning has anything to do with it. I could be wrong, but I think it has to do with flow. Once in a blue moon I'll get a CEL, but that's when I'm logging with my CReader not in the OBD-2 port. I recommend everyone get a CReader. They're cheap and effective.

[trinydex]

it has to do with cleaning. otherwise you could put a tiny exhaust on your car and pass smog.

[nj1266]

^^^It could be both, but the trick is to use an anti-fouler and space the secondary O2 sensor from the exhaust stream.