Zapata

Has anybody ever dynoed the car with the v-afc?

spiroh

Astroboy has. So has johntypes, although he had a fuel pressure regulator on top of the v-afc. I might go after I install the RES.

Mike

Is that a custom FPR?

Zapata

any idea if it contributed to any gains? I think it would just flatten out the powerband.

spiroh

Yes.

spiroh

John did see some gains. I dont remember what the gains were. Hopefully he will read this thread, and respond.

KCPreki11

So i'm guessing you've already ran it rich? Just look up john???something or another in the directory...i haven't seen him post often but he has a good website.

scalbert

Actually, stoichiometric ratio is 14.7:1 for gasoline and is the best ratio for producing the least amount of emmissions. Basically it burns 'cleaner' at this ratio. Definition: "Stoichiometric or Theoretical Combustion is the ideal combustion process during which a fuel is burned completely."

But it is not the ratio for optimal power. Most engines do make the most power in the 12.5:1 - 13.0:1 range which a few just above or below this.

Or as Corky Bell states in the book (a must read...):

"When testing, two significant numbers will be required: cruise AFR and full-throttle AFR. Cruise AFR will likely be in the range of 14.0 to 15.0 to 1. Full throttle is where the fun is and should be close to 12.5 or 13.0 to 1."

spiroh

So is that less fuel or more?

CLUofI

More fuel.

mackdaddy

Whoops. You go boy! And thank you for explaining it so well. I actually knew that, but had a serious brain fart while typing that statement. Forgot allllll about a correction.

And trust me, the fun does exist in the 12:1 ratio range. I just got back from cruising around for 20 minutes (can you say long way home!,) and barked 2nd gear like there's no tomorrow several times. Some had this early in the game, mine wouldn't cooperate until now.

Gotta love the power of cold air too!

Damn I wish I hadn't sold my Gtech-pro awhile back......

Crazy Bimmer

you track guys need to get rid of your CLS and buy a used supra!!

scalbert

Depends on where you start and where you end up. By adding fuel with the same mass of air you are richening the mixture, or also stated, lowering the AFR (Air/Fuel Ratio).

What the A'pexi unit does is alter the MAP (Manifold Absolute Pressure) signal but it the adjustments allow it to be altered only when you need it such as at certain RPM or throttle inputs. This then doesn't cause the PCM to adjust for idle or cruise situation.

It basically reads in the current MAP sensor voltage and outputs a similar voltage to the PCM's MAP input. The outputted voltage is user adjustable. By increasing it you are telling the PCM there is more air than what is actually present so the PCM squirts a bit more fuel.

Conversely if you reduce the signal you tell the PCM there is less fuel so it will injector a bit less, leaning out the mixture a little from where it would have been.

You can't look at the terms rich and lean as absolutes when fine tuning. If someone says they leaned out the mixture some that isn't a quantifiable value. They may have just gone from 12.5:1 to 12.7:1, or maybe 13.0:1 to 13.1:1. They may have no idea what their AFR is; they just know they went a little leaner.

Now people will warn that you don't want to go too lean, which is very true. But what that value is not set in stone for all cars and is dependant on other factors such as timing, fuel grade, etc.

KCPreki11

So you haven't tried it?

spiroh

I've only tried raising the fuel with my V-AFC. Never with a FPR.

scalbert

Juts be aware that an FPR will the base pressure which in turn the PCM will trim out these changes, to a point.

With the V-AFC you are adjusting based on RPM settings typically leaving the fuel setting alone close to idle and cruise speeds. So during normal driving the PCM gets the same signal as it would without the device present. But go into WOT, where the PCM does not re-calculate traim value or rather it is in Open Loop, and the V-AFC feeds false signals to get the desired WOT fueling.

spiroh

With the V-AFC, you can control standard driving, and WOT.

scalbert

Very true, my point was that most leave idle and cruise setting alone. Unless you have modified the car to where it requires adjustments to get the FT back to 0% it is best left alone.

This then allows for independant WOT control without affecting idel and cruise fueling. Why mess with it when it works correctly and passes emission. The fun is at WOT and that is what most typically use the V-AFC for tuning.

spiroh

scalbert,

I'm glad we have people like you on this board. Priceless.

Spiro

TL_Type_S

Spiroh!

Great runs man!

Hey, did you run out in Wisconsin? I think elevation there is close to 4000 ft. That's pretty high up. I have a feeling you ran at a different track.

There is only one type of car that loves cooler weather more than the CL-S/TL-S ... the supercharged GM's .. Buick Regal GS and the GTP/GTX ... wow ..


Raj

spiroh

Is it 4000ft? Yes did go to the track in Wisconsin.

scalbert

Hardly 4000', I beleive the highest point in WI is about 1600' with most being well below that. Lake Michigan is just below 600' with Madison, WI coming in at about 800'.

I would assume the track was at more of the southern end of WI?? If so the track was probably between 600' - 800' elevation.

BTW, a handy elevation finder:

http://www.mit.edu:8001/geo

It would have been nice to see a CL-S turn those times at over 3/4 mile elevation, but is definitly not the case..

Black CL-S 4-Life

Great times..now go kick some Maxima ass!

charliemike

97% humidity and 40 degrees F?

Wow. Is it gonna snow there?

johntypes

elavation is 676ft my car went 14.48@97.50mph spiroh had a higer fuel setting on vtech then i did but his car always winsagainst me