Recommended AFR on full boost ?

My 3.0 L NSX is running with a LoveFab turbo kit and I wonder what's the allowable AFR at full boost?
The engine internals are stock and I'm running 8 psi of boost.
As a safety measure I have an independant AFR gauge that allows me to check real time what's happening.
I noticed that my AFR's will sometimes drop below 11.0 at full boost?
Sounds way to rich to me?
Would a minimum of 12.0 be OK?

At 8 psi I'd target around 12.2 for some margin of safety, below 11 is rich and that low of boost. What ems and what turbo?

I have the AEM ECU but I don't know exactly what turbo is fitted?
It came std with the LoveFab kit.
Are you also running a turbo?

I've been evolving and testing a turbo system design over the last year on my NSX. The prototype kit I had been running that I actually just removed a few weeks back is based on a Comp Turbo Oil-less 6062 with a T3 footprint, for the next iteration we are evolving the system to use a twin scroll Borg Warner EFR 7670 for better response and proper usage of the efficiency range of the turbocharger. For example, 8 psi (~ 440 hp NSX) on a 750 hp capable turbo (commonly used in NSX kits) is below or just at the beginning of its efficiency range, which results in poor transient response (Full boost @ 4000 - 4500 RPM), less torque, and even less power in some cases. My NSX is actually on my lift rite now as I'm making a few of additional changes in addition to a V2 turbo system, including an all new Haltech Elite based tuning package, and an air to water inter-cooler.

Is this a series 2 AEM EMS?

No it's the Series 1 from AEM.
Works perfectly as far as I can tell?
I'm also running with an air to water intercooler to keep the IAT's under control.
I read the documentation on the Comp Turbo Oil-Less.
Looks interesting for sure.

Have you had the car tuned professionally?

E-Nough Logic said:

Have you had the car tuned professionally?

Click to expand...

Yes and no!
As I live in France, the tuning was done by exchanging e-mails with Cody @LoveFab.
The car works fine but I believe I'm not getting the full performance at full boost?

CB72 said:

Yes and no!
As I live in France, the tuning was done by exchanging e-mails with Cody @LoveFab.
The car works fine but I believe I'm not getting the full performance at full boost?

Click to expand...

I'm going to have the same issue when mine is mapped again, i can't afford to fly Cody over again so was going to get it mapped professionally locally.

Then i was hoping to hire a dyno for an hour with wifi and ask Cody very nicely if he would remote in to my laptop via logmein while it's connected to the ecu.

I don't think it's the preferred way because it might be a little laggy and the tuner may not catch something as it happens and doesn't get a real feel for what's happening. However on the basis it should be a safe tune because it's already been tuned and you would be driving it hard anyway because you have had it tuned then surely it's no harm in putting it on the dyno and getting a second opinion from someone who actually specializes in our cars and we know we can trust.

Alternatively we could consider going halfs on flights etc. I could consider this some time next year if i was to change the turbo and injectors.

My AFR would make more sense if plotted on a curve. At full boost, low RPM, i'm at about 12. At full boost, mid RPM, i'm at about 11.2-11.4. At full boost, near readline, I start to bleed in more fuel to end up at around 10.8 at redline. It's costing me some power at the top end but i'd rather have the safety. I'm also conservative on my timing at the top end as well. Keep in mind crappy California 91 octane gas.

RYU said:

My AFR would make more sense if plotted on a curve. At full boost, low RPM, i'm at about 12. At full boost, mid RPM, i'm at about 11.2-11.4. At full boost, near readline, I start to bleed in more fuel to end up at around 10.8 at redline. It's costing me some power at the top end but i'd rather have the safety. I'm also conservative on my timing at the top end as well. Keep in mind crappy California 91 octane gas.

Click to expand...

Your tune sounds very similar to mine.
When on track I use 98 octane gas so I suppose I could go a little leaner?
I'd be interested in your timing?
I'll look up mine FYI.

- - - Updated - - -

jaffaz32 said:

Alternatively we could consider going halfs on flights etc. I could consider this some time next year if i was to change the turbo and injectors.

Click to expand...

That might be a good idea.
A local tuner killed my friend's NSX by pulling 500 whp with stock internals...
BTW how do you get by the pollution test?
My car failed it as the regulations get tighter and tighter.
We should maybe get Cody to insert a Catalytic converter in the exhaust that we would use only for this purpose?

CB72 said:

Your tune sounds very similar to mine.
When on track I use 98 octane gas so I suppose I could go a little leaner?
I'd be interested in your timing?
I'll look up mine FYI.

Click to expand...

I believe they measure octane rating differently in the States compared to Europe, might just be UK but in the UK it is Ron, I think 99 Ron here is a different octane to 99 in the States. Might be wrong though.

CB72 said:

That might be a good idea.
A local tuner killed my friend's NSX by pulling 500 whp with stock internals...
BTW how do you get by the pollution test?
My car failed it as the regulations get tighter and tighter.
We should maybe get Cody to insert a Catalytic converter in the exhaust that we would use only for this purpose?

Click to expand...

It is a problem for me also, I know a guy who knows a guy. There are tricks also, taking it for a hard drive before hand can help.

It's really frustrating as my car is more mechanically sound than most cars on the road of it's age or newer but fails emissions not even by much. For how often i drive it, does it really matter.

I had Cody make a cat bolt in option for mine when i was running the FIC it still failed on emissions. I've gone with a standalone now, not sure how that would affect emissions, it's not been tested since.

Yes the US uses (RON+MON)/2, so our 91 octane is RON 95.3 (highest available in California) and our 93 is RON 97.4 (the only good thing about the east coast). RON 98 is better than anything normally available, other than race fuel.

jwmelvin said:

Yes the US uses (RON+MON)/2, so our 91 octane is RON 95.3 (highest available in California) and our 93 is RON 97.4 (the only good thing about the east coast). RON 98 is better than anything normally available, other than race fuel.

Click to expand...

That's interesting.

Shell VPower Nitro+ is 99 Ron
Also Tesco which is a supermarket here in the UK is 99 Ron.

Regular fuel is usually about 95 Ron other brands BP, Esso higher octane is from 97 to 98 Ron.

So our fuels contain more octane than over in the states?

I filled up at a petrol station near the nurburgring that has 102 ron.

So in theory, a tune should be safer here in the UK with our fuels or we could perhaps squeeze a little more power out of our tunes.

jaffaz32 said:

That's interesting.

Shell VPower Nitro+ is 99 Ron
Also Tesco which is a supermarket here in the UK is 99 Ron.

Regular fuel is usually about 95 Ron other brands BP, Esso higher octane is from 97 to 98 Ron.

So our fuels contain more octane than over in the states?

I filled up at a petrol station near the nurburgring that has 102 ron.

So in theory, a tune should be safer here in the UK with our fuels or we could perhaps squeeze a little more power out of our tunes.

Click to expand...

If you're curious... tuning with meth (effectively an octane booster) yields about 20-25 whp higher on my low boost CTSC with aggressive timing. Again, so many factors are in play but my tuner and I have stabilized my tune, on crap gas, at 350whp with conservative timing. Hope you find that balance. Too much retard in timing or too rich a tune will yield high EGTs.

This is stock Compression Ratios?

I also have lovefab kit with stock c30.. At full boost im around 11.2 and 6psi was on a previous tune from another nsx, have yet to get it retune but its allmost been 1yr since.. I drive it as much as possible so definitely not garage queen. And rarely am i at full boost just normal driving putting around town..

Short answer? There is no "ideal" AFR. The "ideal" AFR for each individual car varies depending on multiple factors; fuel octane, boost, IAT and timing advance being the most important. More timing, more boost, lower ocatne, or higher IAT typically calls for richer AFR. Conversely, less timing or boost, lower IAT and higher octane can generally tolerate leaner AFR. There are multiple permutations, each with its own "ideal" AFR. The goal is to make the most power possible while avoiding detonation. Since the stock engine has such a high static compression ratio, richer AFR (<12:1) are preferable to leaner mixtures. Personally, I'm satisfied if my AFR are >10.5:1 but <12:1. Honestly, AFR is probably the LEAST important variable to worry about. Timing and boost are much more effective (and potentially dangerous) variables for making power and ensuring a detonation free car.

Random question... do your ECUs not have knock prevention?

Mine will automatically pull timing of knock is detected.

- - - Updated - - -

I've also set it to autotune based on a predefined AFR table but only at +/- 10% from my base tune when not in boost and +/- 2% under boost loading.

RYU said:

Random question... do your ECUs not have knock prevention?

Mine will automatically pull timing of knock is detected.

- - - Updated - - -

I've also set it to autotune based on a predefined AFR table but only at +/- 10% from my base tune when not in boost and +/- 2% under boost loading.

Click to expand...

Fancy pants... :tongue:

What ecu are you running?

jaffaz32 said:

Fancy pants... :tongue:

What ecu are you running?

Click to expand...

Nothing fancy really

Just an old HKS F-Con Vpro (v.3.3). It's probably 10yrs old.

You should possibly look into a more modern EFI solution such as the Haltech Elite for a number of reasons including safety, vastly cleaner emissions, and also longevity. We use the Haltech Elite platform whenever possible for the previously stated reasons.

The Haltech Elite "auto-tunes" all the time with real time computation and long and short term trim tables just like OEM's do. You tell it what AFR you want when, it's internal algorithms figure out how to make that AFR, including everything important in its computation. Similarly for timing - it figures out where your timing should be, all the time - real time. It doesn't just run the timing map you tell it. It makes micro adjustments to increase/decrease timing, registers knock variance via long term/short term memory, in addition to IAT, etc, and gives you the best possible timing all of the time. All using the CAN Bus protocol which is what all modern OBD2 cars use.

I believe Cody has switched to Haltech Elite for its many benefits over previous EFI systems, we swear by Haltech as well.

The problem with the older AEM S1 and S2 ecu's is the tuning tables don't have enough resolution to get an OEM quality tuned car, and they are all injector pulse based which leaves ALOT to be desired... The Haltech Elite, and also the Infinity can greatly increase performance over the legacy EFI systems. We don't run the Infinity nor have we experience with it because Chief Engineer at our shop is also crew on a Haltech Race Team so I can't comment on anything Infinity. We have seen a number of S1 and S2 builds that were night and day difference in running characteristics when switched to the Haltech platform.

The new ECUs are really incredible.

I would assume the new ECUs have provisions for sensor failures as it relates to the auto-tune features. For example a O2 wideband could fail and tell the ECU the car is running super rich, when it really isn't. It will then pull a bunch fuel and motor will lean out and potential kaboom. I'm assuming there's a safety feature for this.

RYU said:

Random question... do your ECUs not have knock prevention?

Mine will automatically pull timing of knock is detected.

- - - Updated - - -

I've also set it to autotune based on a predefined AFR table but only at +/- 10% from my base tune when not in boost and +/- 2% under boost loading.

Click to expand...

I haven't used the autotune feature on my AEM S1 as I don't fully understand how it works?
For instance on page 138 of the manual the "Auto mapping" menu allows you to set the "weight before change" I suppose it sets the cumulative data required before making any change but what about the "Target accuracy"?
The example shows "100" ???
Does this mean 100% or else?
Last but not least will the automapping change the fuel map automatically or can you look at it before putting it into service?

- - - Updated - - -

gesundlich said:

Short answer? There is no "ideal" AFR. The "ideal" AFR for each individual car varies depending on multiple factors; fuel octane, boost, IAT and timing advance being the most important. More timing, more boost, lower ocatne, or higher IAT typically calls for richer AFR. Conversely, less timing or boost, lower IAT and higher octane can generally tolerate leaner AFR. There are multiple permutations, each with its own "ideal" AFR. The goal is to make the most power possible while avoiding detonation. Since the stock engine has such a high static compression ratio, richer AFR (<12:1) are preferable to leaner mixtures. Personally, I'm satisfied if my AFR are >10.5:1 but <12:1. Honestly, AFR is probably the LEAST important variable to worry about. Timing and boost are much more effective (and potentially dangerous) variables for making power and ensuring a detonation free car.

Click to expand...

Thanks for the feedback.
This video from Haltech shows that AFR doesn't play a great role in terms of power ( within limits of course)
https://www.youtube.com/watch?v=Zzn3-ygH-v8

[MENTION=19738]CB72[/MENTION] wish I could help but I'm not familiar with the aem units. Unless you have safety fail-safes I would say do not use the auto-tune feature. Too risky...

RYU said:

[MENTION=19738]CB72[/MENTION] wish I could help but I'm not familiar with the aem units. Unless you have safety fail-safes I would say do not use the auto-tune feature. Too risky...

Click to expand...

Good advice. Thanks!
BTW, I noticed on your build thread that your exhaust uses some valves to divert the gases through a cat under normal driving conditions?
Do you have any further details you'd like to share?
I'm almost sure I could pass the emission's test here in France with your setup?
The test is quite basic: first measurement at idle and then they run the engine at 3000 rpm at no load.