timing vs AFR

[selmerguy]

I am going to have my last try at the track this weekend. I got the car running pretty good aside from the occasional IC pipe getting blown off. While tuning I am curious about what is more important for power timing or afr. Should I tune for the 11.1:1 afr and pull timing so I dont get knock or run richer and get 20 degrees at 7000 rpm. The only way I get to 20 degrees is if I run about 10:1 AFR. Which way makes more power?

 

[pballer]

Pump or race gas will make a difference. assuming your running pump I would shoot for like ~10.5:1 and as much timing as possible. Keep in mind that every car is different and every tuner might tell you something different. depends how much boost you are running as well, as well as many other factors.

 

[420a-t]

On my dsmlink setup I made more power (when I was on pump) when I had a 10:1 afr and more timing as compared to an 11:1 afr and less timing. I could feel it, and dsmlink said I had around 40hp difference between the two. When I'm on race gas, I tune for about 24-25 degrees of timing, and once I get it there, I start to lean it out as much as possible before knock sets in. I have always been told that if you hit 24-25 degrees of timing advance, try to lean it out instead of adding more timing, it will net you the most hp.

 

[selmerguy]

Yeah this is on 93 pump gas. So 10.5:1 is a good AFR for pump gas huh... Shoot I was tuning to lean I guess. I can get about 20 degrees with no knock at that AFR I think.

 

[turboglenn]

A general rule of thumb for me ( one which i usually don't give away, but hey this palce has helped me) is this.

1.) Set the turbo to it's peak efficiency point ( since you and i run the same turbo, i'll give you my method for my turbo) run about 22-24PSI, it's in the range of teh 2nd center "island" but the compressor is still efficiant there.

2.) Turn the timing DOWN ( if you can ) to about 12* or so ( jsut start lower than you knwo it will go)

3.) Set the boost and start tuning A/F's I shoot for 11.2 - 11.5 untill i'm in the range of 26PSI + and then i go for 10.5's to 10.8's

4.) Once your AF's are good, slowly start advancing timing untill you get knock nad then back it down 2* at a time untill there's little to none ( some is exceptable, but not much)

5.) That will give you the best baseline tune.. after the timing and AF's are set from that guide... go back and fine tune the areas that need it.

Hope that helps, it's been one of my main methods for tuning for years

420a-t is pretty much throwing some good info too... on pump gas 10:1 will help with detonation, but waste more fuel ( not important in racinf of course)

 

[CanadianTSi]

Timing will make alot more power than AFR.

If your car is happy at 10:1 then leave it there, the perfect AFR varies from setup to setup.

20 degree's of timing and as much boost as you can get away with should work well.

 

[turboglenn]

Timing will make alot more power than AFR.

If your car is happy at 10:1 then leave it there, the perfect AFR varies from setup to setup.

20 degree's of timing and as much boost as you can get away with should work well.

My street map is at 20 from about 5k RPM and up. It seems happy there, and i arrved at teh number starting at 14 and slowly advancing till i saw/heard any signs of pre-ignition. So i guess you could say that's one way to look at it

 

[JayRolla]

Timing will make way more power. You want to run as much timing possible on a good afr. I would stay around 10.9-11.2 afr and run as much boost possible with a good timing curve. If you can pull a little timing to get more boost than do that. More boost with less timing will make more power then more timing and less boost.

Thats why I love e85. You can set the boost where you want it and leave it. Tune only the afr and add timing. Stuff loves timing and makes awesome power with the timing.

 

[daren_p]

I use to tune my car with an a/f ratio of around 11 to 1 & run as much timing as possible but now with my FP1X cams, the car likes to be abit richer, so I tune around 10.5 to 1. I have no dyno sheets to prove it but with the butt dyno, you can actually feel a pretty big difference by adding or taking away a couple degrees of timing. I have never been able to actually feel (ie not a large enough hp change) a difference from running 10-1 & 11-1. If you can see 20 deg advance on pump, thats not bad at all. I'm happy with the 17-18 deg I see (but timing is also boost related, more boost usually means having to runn less timing) & thats running 23psi.

 

[JayRolla]

I use to tune my car with an a/f ratio of around 11 to 1 & run as much timing as possible but now with my FP1X cams, the car likes to be abit richer, so I tune around 10.5 to 1. I have no dyno sheets to prove it but with the butt dyno, you can actually feel a pretty big difference by adding or taking away a couple degrees of timing. I have never been able to actually feel (ie not a large enough hp change) a difference from running 10-1 & 11-1. If you can see 20 deg advance on pump, thats not bad at all. I'm happy with the 17-18 deg I see (but timing is also boost related, more boost usually means having to runn less timing) & thats running 23psi.

Man I wish the 1g had a less aggresive timing curve. I see 24-26* timing and I still see a little knock at 15psi. 2g pistons w/ 1g timing curve is not good. Without a fmic I cant run more than 15psi on my 16g. My brother had the same setup as me and a fmic and we could not run more than 17psi without pulling lots of timing.

Pump gas just plain sucks on these small turbos. E85 all the way. Now he can run 26-28psi and 30* of timing with no knock.

 

[2gGSX]

Just a FYI, but after a certain amount of timing there gets to be a very steady rate of diminishing return. Most people would just tune for MBT and call it a day.

 

[pballer]

It's hard to find MBT without a dyno. especially if your not a very experienced tuner. See what I mean about every car and every tuner being different? I have to agree that more timing will gain you more than leaner AFR.

 

[Black_Bullet]

Rule of thumb, Boost makes the most power, then timing, then air fuel ratio; and Im not too sure how compression plays into all of this but i know its a strong variable...

Not that theres anything special about my tune but just to add in for conversation,
I run 17degs timing adv with 11.1 ish air fuel ratio and my evo316g spiking to 22psi and settling to 20lbs 3rd gear up. I tried this same set up with 19degs of timing and it pulled quite a bit harder but in the upper gears was prone to knock. I was going to richen it up to a 10.1 with 19degs timing but said hell with it and kept 11.1 and 17degs . Gas isnt getting any cheaper... Unfortunanly I tune with eprom-rom tuning thru custom chips and its not as convienent or on the fly as you guys using dsmlink or else id have a very finely tuned car .

Also another thing to add, on stock internals its not good to drop the timing too low as I saw were the other guy was mentioning something about starting at 12degs and going up...
Well this would work well on forged internals, but too low also brings a dramatic increase in heat as well and could throw you off. Any lower than 12deg and id say it be too low, but realistically unless you have like 9:5 compression or something i dont see why start timing under 14degs unless the goal was max pump gas boost, in which the thresh hold for that would still be low reguardless of how low timing was.
But as a side note, stroker 4g63s tend to like lower timing...

And Jayrolla, I agree with you about the E85.
Im considering it over meth, and if i did use it id be going for something like 24-25degs timing, 11.5, and 24psi type street tunes.... Good stuff..

 

[GVR4592]

Im considering it over meth, and if i did use it id be going for something like 24-25degs timing, 11.5, and 24psi type street tunes....

That's more like an agressive pump gas tune, I'd imagine you could do better than that with E-85.

 

[JayRolla]

That's more like an agressive pump gas tune, I'd imagine you could do better than that with E-85.

I was going to say the same thing. Ive seen someone on a 16g running 26psi and 32* timing. People I know here are running over 30psi and over 28* advance on t67's running e85.

 

[dsm-onster]

Rule of thumb, Boost makes the most power, then timing, then air fuel ratio; and Im not too sure how compression plays into all of this but i know its a strong variable...

Not that theres anything special about my tune but just to add in for conversation,
I run 17degs timing adv with 11.1 ish air fuel ratio and my evo316g spiking to 22psi and settling to 20lbs 3rd gear up. I tried this same set up with 19degs of timing and it pulled quite a bit harder but in the upper gears was prone to knock. I was going to richen it up to a 10.1 with 19degs timing but said hell with it and kept 11.1 and 17degs . Gas isnt getting any cheaper... Unfortunanly I tune with eprom-rom tuning thru custom chips and its not as convienent or on the fly as you guys using dsmlink or else id have a very finely tuned car .

Also another thing to add, on stock internals its not good to drop the timing too low as I saw were the other guy was mentioning something about starting at 12degs and going up...
Well this would work well on forged internals, but too low also brings a dramatic increase in heat as well and could throw you off. Any lower than 12deg and id say it be too low, but realistically unless you have like 9:5 compression or something i dont see why start timing under 14degs unless the goal was max pump gas boost, in which the thresh hold for that would still be low reguardless of how low timing was.
But as a side note, stroker 4g63s tend to like lower timing...

And Jayrolla, I agree with you about the E85.
Im considering it over meth, and if i did use it id be going for something like 24-25degs timing, 11.5, and 24psi type street tunes.... Good stuff..

I agree. Creating more massflow nets the most gain. Tune to the max safe boost. Or the boost you're brave enough to tackle . Next get a baseline A/F ratio based on fuel (pump gas: tune to 10.5:1). Then focus on timing. Add a degree at a time until you see knock (timing retard). Then move to the next timing point to create your curve. After that go back to fuel and lean out at each point just before you see knock. You may think that you can't lean her out a little more once you've adjusted for the most agressive timing curve, but you can. Just focus on small incriments.

A note. Retarding timing does not increase the heat in the combustion chamber. It increases the heat in the exhaust track (runners included). It won't hurt cast pistons at all.

 

[Black_Bullet]

I was going to say the same thing. Ive seen someone on a 16g running 26psi and 32* timing. People I know here are running over 30psi and over 28* advance on t67's running e85.

Thats interesting, i havent actually tuned with E85 so i wouldnt know what kind of thresh hold it has but thats still sounds like a lot to ask for the 16g to run everyday. I dont like to push my set up to the max because this is my only car and im on old over 100k stock bottom end. Id rather have leeway incase of any hiccups instead of walking the edge. But good stuff, also since i tune with chips, it would take way too many reburns to get dialed in the way I want, and I dont have to much tuning bench time. But thats good to know that my tune is that conservative as I fixed another minor boost leak and am now spiking 23psi instead of 22.

I agree. Creating more massflow nets the most gain. Tune to the max safe boost. Or the boost you're brave enough to tackle . Next get a baseline A/F ratio based on fuel (pump gas: tune to 10.5:1). Then focus on timing. Add a degree at a time until you see knock (timing retard). Then move to the next timing point to create your curve. After that go back to fuel and lean out at each point just before you see knock. You may think that you can't lean her out a little more once you've adjusted for the most agressive timing curve, but you can. Just focus on small incriments.

A note. Retarding timing does not increase the heat in the combustion chamber. It increases the heat in the exhaust track (runners included). It won't hurt cast pistons at all.

That makes sense, i was always told otherwise. Good to know thanks.

 

[JayRolla]

Thats interesting, i havent actually tuned with E85 so i wouldnt know what kind of thresh hold it has but thats still sounds like a lot to ask for the 16g to run everyday. I dont like to push my set up to the max because this is my only car and im on old over 100k stock bottom end. Id rather have leeway incase of any hiccups instead of walking the edge. But good stuff, also since i tune with chips, it would take way too many reburns to get dialed in the way I want, and I dont have to much tuning bench time. But thats good to know that my tune is that conservative as I fixed another minor boost leak and am now spiking 23psi instead of 22.





That makes sense, i was always told otherwise. Good to know thanks.

The 16g can run 26psi without any major problems. The main problem is getting it too hold that level. The housing's are just to small to hold higher boost levels.

E85 is incredible. My mechanic said he can add as much timing as he wants with dsmlink and still will never get knock. He said he added so much he started to lose power which he has never seen till he started tuning with e85.

Whenever people have knock or tuning issues he says the same thing everytime. Its because your running pump gas. 16g's tunes on pump gas are just horrible. He says run e85 and your issues will be cured. I'm personally going to run methanol injection and see how that goes.

 

[2gGSX]

The 16g can run 26psi without any major problems. The main problem is getting it too hold that level. The housing's are just to small to hold higher boost levels.

E85 is incredible. My mechanic said he can add as much timing as he wants with dsmlink and still will never get knock. He said he added so much he started to lose power which he has never seen till he started tuning with e85.

Whenever people have knock or tuning issues he says the same thing everytime. Its because your running pump gas. 16g's tunes on pump gas are just horrible. He says run e85 and your issues will be cured. I'm personally going to run methanol injection and see how that goes.

This may be the MBT phenomenon, however I've never heard of a car actually losing power after a certain point of increasing timing.

Running E85 and making big power has its own slew of problems, namely getting a fuel pump that can support the huge injectors you need. However, just running even a few gallons in a mixture of pump and E85 can net benefits from the extra ethanol's ability to remove the latent heat of combustion.

 

[wishihadatalon]

I agree. Creating more massflow nets the most gain. Tune to the max safe boost. Or the boost you're brave enough to tackle . Next get a baseline A/F ratio based on fuel (pump gas: tune to 10.5:1). Then focus on timing. Add a degree at a time until you see knock (timing retard). Then move to the next timing point to create your curve. After that go back to fuel and lean out at each point just before you see knock. You may think that you can't lean her out a little more once you've adjusted for the most agressive timing curve, but you can. Just focus on small incriments.

A note. Retarding timing does not increase the heat in the combustion chamber. It increases the heat in the exhaust track (runners included). It won't hurt cast pistons at all.

It can play hell on your exhaust valves though. That is why if you choose to use a egt gauge (though not really important anymore), you are supposed to mount it close to the head.

 

[JayRolla]

This may be the MBT phenomenon, however I've never heard of a car actually losing power after a certain point of increasing timing.

Running E85 and making big power has its own slew of problems, namely getting a fuel pump that can support the huge injectors you need. However, just running even a few gallons in a mixture of pump and E85 can net benefits from the extra ethanol's ability to remove the latent heat of combustion.

Ive never heard of it either. But he said the butt dyno and dsmlink netted loss in power. I believe every word the guy usually says from what Ive seen him build and for how long he has been doing it.

The fuel pump is not a problem, dual 255lph walboros works just fine. Mixing e85 with gas makes tuning a bi***. It can be done but it will always be different each time you mix and you need to retune evertime unless you make a perfect mixture.

 

[wishihadatalon]

I got a stock rod that begs to differ. No knock + retard == by by rod. It would seem that there is definatly a minimum timing for cast internals, not a maximum.

However, retarded timing to me, means more cylinder pressure since there is less space in the combustion chamber upon ignition (if the valves are still closed)

Wouldn't that be more timing? Retarding the timing means that you are firing closer to tdc which means by the time the flame uses all of the fuel to drive the piston down, the piston will already be traveling down. Pre ignition or too much advance will cause excessive cylinder pressure and broken parts because you are firing too far before tdc thus causing the entire mixture to ignite and expand before the piston has made its full upstroke.

Less timing means that you fire your a/f mixture too late and cause the burning mixture to not be fully used on the pistons down stroke (less power) and you leave it to burn as it exits the cylinder and into the exhaust manifold.

 

[Black_Bullet]

The 16g can run 26psi without any major problems. The main problem is getting it too hold that level. The housing's are just to small to hold higher boost levels.

E85 is incredible. My mechanic said he can add as much timing as he wants with dsmlink and still will never get knock. He said he added so much he started to lose power which he has never seen till he started tuning with e85.

Whenever people have knock or tuning issues he says the same thing everytime. Its because your running pump gas. 16g's tunes on pump gas are just horrible. He says run e85 and your issues will be cured. I'm personally going to run methanol injection and see how that goes.

Thats awsome about the E85's potiential. I plan to upgrade turbo to a BB Fp3052 eventually and run 25psi daily with E85 as I know that turbo will like being up there, and survive being up at that psi more than a old 16g would. Im hoping that my FIC 850s, and my 48psi base fuel pressure plus a supra Denso 260lph F.pump and upgraded lines and fuel filter can supply enough fuel for that psi for at least as low as an 11.7 afr on e85.
.. As far as 26psi on the evo3, I know the 16g can do it ive experimented with 25lbs before. But im talking about lifespand here, what i mean is id like to keep my set up in a range were i can extract as much performance as possible without making the reliability ridiculous...

This may be the MBT phenomenon, however I've never heard of a car actually losing power after a certain point of increasing timing.

Running E85 and making big power has its own slew of problems, namely getting a fuel pump that can support the huge injectors you need. However, just running even a few gallons in a mixture of pump and E85 can net benefits from the extra ethanol's ability to remove the latent heat of combustion.

I agree that after a certain point youd loose power... In a very unscientifical view point, too much of a good thing can be a bad thing for instance...

 

[2gGSX]

To put it back into scientific perspective, igniting the intake charge early enough to actually allow combustion to finish and expansion to occur before TDC would increase resistance against the piston by using the same thing which is supposed to push the piston down after TDC and make power (one issue sieving power via two pathways).

 

[dsm-onster]

I got a stock rod that begs to differ. No knock + retard == by by rod. It would seem that there is definatly a minimum timing for cast internals, not a maximum.

However, retarded timing to me, means more cylinder pressure since there is less space in the combustion chamber upon ignition (if the valves are still closed)

Hmm, I have seen 10-15 different melted pistons/bent rods from excessive timing advance. I've seen none from retard. Igniting the gases sooner than later (both before tdc), the expanding gasses are forced to compress as the piston continues to push to TDC.