Ok I went to the dyno meet today and managed to pull off 190 RWHP.

Here's my sheet:



I see that my AFR is around 11 after 4.5k RPMS. How much can I tune my SAFC to get a wee bit more power.

Thanks

 

you can tune to 12 i believe if you have an NA. Ive heard of some going as lean as 12.5ish, but I would stay at 12.

 

how much - % on the safc would raise the AF 1 point.

 

Go back to the dyno and have it tuned properly. Don't guess.

 

was the first time he dyno'd it not propor?
can we get a bigger pic of the dyno? that one sucks.
If you need a host email it to me: Nicerx7@aol.com

 

btw, do you have a t2 or an NA
Edit* and what mods?

 

He has an '87 t2, according to his profile. Each tuning job for every car will be different, so it is ultimately up to you and if you cannot tune it properly, have a professional do it.

 

Just emailed you a bigger pic of the dyno sheet.

The pic I uploaded to imagestation was huge but when I linked it here it got shrunk.

I have an 87 T2 Mods:

RB Turboback
Walbro
FCD, BOV (<- if you wanna call those mods)

 

what was your boost? 190 seems kinda low.

as for tunning. you do a dyno run. adjust a bit. dyno run, adjust abit, dyno run etc....

you can't just do it once.

 

I didn't say it wasn't, I said he should go back to the dyno and have the S-AFC tuned properly instead of asking us to guess what correction figures might give him the AFR he wants. That's a good way to lose an engine...

 

7.5psi on the stock s4 turbo.

 

If you uploaded the original large picture go to your imagestation and click on view original and it will show you the full size picture and you can load it here.

 

Oh ok, thanks. I dont get how to tune the AFC quite yet either. like the +/-%, say you are running 11:1 at 3500rpms.. what would tuning it -50% give you for an AFR?

Anyways, here's his dynosheet:

 

The beast appears to be suffocated above 5krpm.

 

22:1, point being though that the engine would not be running at the same RPM because it wouldn't be able to make enough power to turn itself over. So the AFR would change again..
Really like NZConvertible said, you can't just guess and plug in numbers, some engines will respond slightly different to how much fuel you inject.

So don't try and tune a SAFC by doing one dyno run and trying to extrapolate AFR adjustment numbers from that to plug into your SAFC. Do it while your at the dyno.

 

What he said. Don't guess!

 

I've heard of people going to 13 no problem on n/a... 12 is alright, but you can go leaner and see greater gains

 

that's the stock intake's fault. replace that intake with a 3" pipe and K&N and you'll soon realize how crappy the stock piece is. Through experience, on my car with only exhaust, my boost reaches 10psi at around 5k and falls to 7psi by redline. With my intake on, boost goes to 10psi till 4k then jumps to 17psi till redline. That was with unported S4 wastegate.

 

There is no suffocation above 5000 rpm. The
dyno chart appears to be perfectly normal.
Peak torque will be made at 5250rpm, and stock
intake or any intake kit wouldn't move that by
much.
Horsepower dropping after 6200 rpm indicating
this engine sports a stock porting or close to stock
port configuration. It seems that you can move
everything from 6000 rpm up half a point. That
might give you a little more power and move the
peak hp up a few hundred rpm. However, since
you have very limited control over your timing it is
not advisable to lean out too much more.

 

I dont see why tuning -50% off of 11:1 would give you 22:1, seems like it woudl give you 16.5:1, while tuning -100% (which isnt possible) would give you 22:1... explain to me?

 

11:1 -> 11 : (1*0.5) -> 11:0.5 -> (11*2) : (0.5*2) -> 22:1

This is of course keeping in mind that the actual air flow stays constant...
Which of course it doesn't like I said above.

Maybe you could explain to me how you worked yours out? You might be right... I don't know much when it comes to things like this, i'm only a mere student

 

An interesting correlation I've found on a few stock dynographs is the hump between 4k and 4.5k rpms. This is obviously after the secondaries are firing, so there should be plenty of fuel to support the incoming airflow. Has anyone else noticed this tiny lean hump on bolt-on fc's?

 

-50% is half, so it you tell the ECU it's getting half the air is really is then it's inject half the amount of fuel. An AFR of 11:1 means 11 parts air to 1 part fuel (by mass), so if you half the amount of fuel you get 11 parts air to 0.5 parts fuel which is the the same as 22 parts air to 1 part fuel (22:1). Make sense?

FYI, if you set the S-AFC to +50%, an 11:1 AFR would in theory change to 7.3:1, but I doubt the engine would even run...

 

Lol ok, thx jason