word is the readings the the VAFC gives out are wrong when you use a 3 bar map sensor...is this true? how do you like the set-up, and which map sensor did you use? thanks for info.

 

lol, what are you VAFC guys doing to boost more? lol * bump *

 

if by incorrect readings you mean the manifold pressure that the afc shows, yes, it would be wrong, unless you could program the afc otherwise. the 3 bar sensor puts out 5V at 28 psi, while the stock MAP puts out 5V at 14psi, or so. I believe that's the case, so I guess you could just divide it by half?
so, here's my question...

At what point would the 3bar sensor exceed 2.8v as it's output? I'd think that you could run whatever that amount of boost is, on the stock computer with NO piggy-backs and just larger injectors. Is this correct?

 

2.8 volts corresponds to 9.2 psi of boost on the 3 bar MAP sensor. You'll probably have problems doing this though since larger injectors take longer to open, you can't just use injectors that are twice as big and use a MAP sensor with half the output. Using a 3 bar MAP sensor is just like using two resistors in series as a voltage divider to scale your MAP sensor voltage down it doesn't work very well as you know. You need to add more fuel at idle to compensate for the longer opening time of larger injectors. That's what the circuit is for. Have you got those chips yet?

 

sigh, i'm just trying to find the easiest way to boost over 12psi w/ the vafc hack.

 

Easiest way is to DO IT RIGHT. I'm using the AFC hack up to 10 PSI but only until I can afford the AEM EMS.

IT'S DANGEROUS....did you not read about how the AFC hack affects timing?

 

Sorry for the delay guys!

I just tried to hookup a GM 3 BAR MAP sensor on my VAFC hacked turbo H22a. Should I mention that I'm running -50% all accross with 550CC/m injectors. I'm at 9 psi and want to boost more.

With the stock sensor: the idle MAP varies between 2.90 and 2.95 V

With the GM sensor, the idle MAP varies between 2.80 and 1.05 V

Result: The idle is shity and since the variation range is now larger, I don't even feel like trying to alter my fuel correction values. I think it's always gonna bug with this setting...

I was wondering, in the SENSOR TYPE function of the VAFC, is there another setting more approriate for the 3 BAR MAP sensor??? The setting is now IN: 06 OUT: 06.

Thanks for your help.


[Modified by Blaast, 6:17 PM 9/19/2002]

 

 

what would happen if you were to add a check valve with the AFC hack...could you boost more then?

 

With a check valve, of course, no problems with hitting the sensor limit. However, the Honda ECU will not see boost and will not richen the mixture with boost. In other words, the VAFC hack won'T work anymore and you will need a RRFPR to add fuel per psi of boost. (That's a step back, IMO).

So, How do I get this GM MAP sensor to work? I'm sure there's a way to "TO IT RIGHT" is it?

 

i've been trying to think of ways but IMO just save for a hondata or soemthing... it's like $472

i'll be ordering mine soon

 

If you are using a 3 bar MAP sensor you don't neet a -50% cut anymore. I'm surprized you were able to start the car with a 3 bar MAP and a -50% cut. Installing a 3 bar MAP is just like applying a -33% cut across the board.

I think that with 550cc injectors and a 3 bar MAP you should try a 0% correction first and go from there you may even need to add fuel at idle with 550cc injectors and a 3 bar MAP

 

Its call a standalone...hondata or AEM EMS. The hack is just that...a hack. It works awesome for what it is. But with anything over 10psi you really need to start worrying about ignition timing and a bunch of other things.

Invest in a standalone so you dont have to invest in another motor.

and about the 3bar...ive said this about a 1000 times. The 3bar will give the stock honda computer all sorta of weird map signals. It wasnt designed to use that type of a sensor. Its like flying blind.

The p28 ecu maxes out the injector duty at around 72-73%...so even if you can fool it to run more boost you are only going to get 72-73% injector duty. And with 450cc you are going to be running lean after ~10-12psi, with 550s you might beable to squeeze more out..but its going to run like crap all other times.

Your best option is to run more fuel pressure and set your afc at -50%. Thats your best bet.

liam

 

By wiring a MAP sensor into the TPS on the afc, you are still giving the ecu similar map values...you are just giving them two different ways.

one way you are using a map limiter so you dont see over 0psi and then are using another map sensor to step up values in the afc. From -40% to around 0-5+%. So the end result at full boost is say +5% on the afc....or just about at the limit of the fuel maps.

The other way...you have the afc set at -40% and let an unrestriced map do the stepping up. At full boost again, you are close to the fuel map limit of the ecu.

Both ways work...just the 2nd way (the best way) does the stepping up correctly. The end result is similar.

liam

 

I'm certainly gonna try that... Thanks for the suggestion.

Just to clarify, I'm using the "BEST" VAFC HACK.

 

if i ran -50% what do you think i should have for a idle Fuel pressure? ugh...more dyno time

 

Arggggghh! You are already cutting the MAP signal by -33% by using a 3 bar MAP sensor. Don't pile another -50% on top of that. Using a 3 bar reduces you're MAP signal plenty already.

 

i should have been more specific, i was refering to what liam said...about just running hack and upping FP and lowering to -50%