It should be just fine to run that lean at lower boost levels if your car is tuned. I don't get richer than 12.0 until after 10#. I've even ran as lean as 12.2 at over 20# on several occasions just to see if it made more power (it did). Tune the car on the dyno and it will let you know where it's happiest. With my tune, the extra fuel is there because I wanted a little safety buffer.

Point begin in those threads that 11.x isnt going to help you stay out of detonation range when your timing is on the edge and intake temps sky rocket.

What I'm trying to account for is minor cylinder to cylinder variations that exist in every car. If your timing is on the edge and your intake temps sky rocket you have other issues.

I remember that thread...

End of the day it depends on many factors... Rules only apply to well sorted motors.

Spookyfish, my AFR was at 12.7 at the upper RPm limit and richer at peak torque 12.0. That is on 93 octane and water wetter in the FM radiator at Savannah temps. 80's-90's As I richened it up it didnt have the crisp response it had when it was leaner.

Savington, you said you richened yours up and found power. I am wondering if you added it to the whole map, the peak torque, or the top of the rpm range? Mine still felt like it wasn't as responsive when it got richer.

Y8, hook me up man, no reply? I know you have benn working with the Hydra a while now.

The reason for retuning now is that the old map went to 30 psi. I remaped it to 21 psi for a finer tune. Also the old AFR map was very basic. 14.5 off boost quickly sloping to 11.5 by 8psi. The map didnt have any change for deceleration, idle, or rpm. I am shooting for a slightly lean highway cruse 14.7 to 17.0 on decel. The map is sloped to slowly richen to 11.5 at 21 psi and lean about .5 from 4000 to 7400. It is rich at idle 13.8 to help smoth the big injectors and A/C idle problems.

Also my timing map was not very smooth either. I may be shooting my self in the foot with this but it is a learning experience and an attempt to make the map as fine as possible. I did make some det cans to use when I get back.

it's "y8s" and I didn't see the direct question to me but let me try to guess...

I haven't used VE / fuel dual maps on the Hydra. Mine was only a 2.1 version. But if I was going to, I would start by setting the VE map to 100% everywhere and getting a rough tune on the inj pw map.

Here is why:

most engine management has a fixed resolution for fuel pulse. lets say it's .01 ms. At idle on a 550cc injector, your fuel pulse is around 1.50 ms. .01/1.50 = .0067 or .67% of the fuel delivered.

at max boost at high rpm, you might need 15.00 ms. .01/15.00 = .00067 or .067% of the fuel delivered.

In short, you gain effective resolution at the place you dont really need it.


... enter VE.


VE (Volumetric Efficiency) traditionally is the amount of air sucked into a motor compared to its displacement. At a given load and RPM, you can predict the fuel needed by knowing how much air the motor ingests. (this is what AFR is, right? Air / fuel ratio).

For tuning, the theory is similar only a little backwards. You know the fuel (you type it into your pulsewidth map) and then measure the airflow (MAP and RPM) and have to create a synthetic VE value to correct any error.

If by some miracle your fuel pulsewidth map was ABSOLUTELY ERRORLESS AND PERFECT, then the VE table would be the actual VE of the BP motor. But we know your map is imperfect as any tuned map is (except maybe Mazda factory maps)...

So you get close in the fuel pulse map and just make it nice and smooth. You could just do a planar map increasing pulsewidth from 0kpa to 300kpa and flat from 0rpm to 8000rpm and let the VE map do the rest. That's how Electromotive (Tec3) and (I think) Adaptronic do it... assume fuel delivery is linear and increases directly with MAP (not RPM) and correct with VE.

y8s Thanks for the reply. I have been a little tied up getting helicopters back in the air. I had to print your reply to digest it. It is a little deeper than I expected but I think I understand what you are telling me.

Because FM sent a pretty good map I am working off of it. I will concentrate on the fuel map and then let it build the VE map from it. Before I let it auto tune the VE map and let it build the fuel map but because I didnt have a dyno to load the car at a certain rpm the auto tune could not see the cell long enough to tune.

sorry to threadjack here, but you more experienced tuning guys do lend the knowledge here. After reading that some of you say 12's are too lean for full boost it raised an eyebrow for me, I was on a rich basemap sinking to 10.5's in full boost. Pulled some fuel made some changes, seeing about 12.3-12.5 full boost with no knock at all, this is on a very conservative spark map. To my question though, what exactly do you guys feel like is a good/safe AFR for idle, light load/cruise, decel?

14.7:1

idle, light load, decel, and WOT all have very different requirements.

idle needs reasonable power and stability but also efficiency so you're not wasting gas sitting still. 14.7 is obvious but not always stable (maximum N/A power is what, 13.5AFR?). Since you have limited airflow and RPM, you can only generate more power by either advancing spark or changing fuel. I personally try to idle around 14.3 as a reasonable compromise. If your car idles well at 14.7, do it.

light load/cruise is all about efficiency and emissions. too rich and you waste fuel and pump out hydrocarbons. too lean and you raise EGT and pump out NOx. 14.7 is the best AFR for emissions, but you can go as lean as the car will reliably run. Reasonable range is probably 14.7-15.4. Some guys here have run up to 16:1 and possibly higher without issue.

decel: shut off the injectors.

the track guys tend to like a slightly rich biased tune in boost since they like the margin of safety over absolute optimum power. I tend to agree once you start getting to serious boost levels.

Remember you can't always hear detonation. It's worth 5%-7% more fuel in boost to reduce the chance of the silent killer. 11-11.5 AFR once you're above 5 psi.

There is an article written by Klaus from Innovative Motorsports that goes over this.

http://www.innovatemotorsports.com/resources/rich.php

In the end, when you're talking about taking an engine to 2-3x the stock power level and detonation being the biggest enemy, running richer is just a simple way to keep an engine safer.

Good input, I appreciate it. I'm currently running 13.8-14.3 at idle, 13's in the light cruise/load, and it just shuts fuel out all together in decel full lean. I got rid of my chinacharger last week and have a garrett on the way so I'm curious to see how the change in size of compressor and turbine plays out on my already slightly adjusted AFRs

^Troof. This approach also helps keep exhaust gas temperatures in check, which is no bad thing.