Question though. How far (psi) can you go with this? The TPS has a range of 0-100% we all know, and as far as I could remember, the voltage at WOT was 4.5xx volts. Now the question is, how much voltage does the MAP sensor emmit at has 10psi? 12psi? Because if it suprasses 4.5xxV, the V-AFC will be seeing something like 110-120% throttle which I assume would cause it to freak. So really you need to determine what the voltage is per psi before you can figure out how much you can push before the V-AFC losses it's ability to maintain everything. Also, as for wha to set the Hi throttle Lo throttle settings, this is the way I see it. Whatever voltage the MAP emmits at barometric (0.0bar) should be the Lo-throttle right? Let's say at barometric the MAP gives like 2V or something (just pulling numbers out of my *** here), now we need to find out at what throttle position does the TPS send out 2V, say 40% throttle.. now that's what we set the Lo-throttle for, 40%. This way when the V-AFC see's less than 40% of what it thinks is throttle, it'll be usuing the Lo-thottle maps which really coresponds to vaccum. Now you'd just do the opposite for boost. If you're boosting say 7psi, find out what the MAP spits out at 7psi (let's say 4V), ok now at what throttle position does the TPS spit out 4V... 90% ok, now we set our Hi-thottle to 90% and viola! We now have a boost sensitive fuel contoller that can compensate fro vaccum to max boost in a linear fashion Sound right dbman? I'm still interested to know what the max psi the V-AFC can read by way of the TPS though. Also, what the most physical pressure the stock MAP can handle before it's damaged?

 

Im thinking you would need a VAFC/SAFC, bigger injectors..and either a second MAP sensor with a check valve or a J&S...correct?

What can be done about timing though? Just retard it to like 10 degrees?

 

VTC_CiViC you are exactly correct on your hi/lo throttle settings; that was how I worked it and I came up with around 60% / 95%.

The MAP sensor reads approx. 2.8 volts at atmospheric and 5v at its maximum of somewhere between 11 and 12 psi (I have not heard anything about physical limitations of the MAP sensor, just that it is only capable of READING up to 11-12 psi of pressure)... so for your average 7-8 psi setup, exceeding 100% is not a problem, and as far as I can tell, when the input exceeds 4.5V it continues to read 100% anyway.

I'm still looking into calibration though; I believe the VAFC may be able to adapt to a different voltage range for its TPS input but haven't had time to check this out.

 

Dbman: Another question...

How do you know how much fuel is enough at the maximum boost?
Like if you have 0 PSI at -40% and 8 PSI at 0%...how do you know 0% is enough fuel for 8 PSI...and that it shouldnt be +10% for example? I guess thats where a dyno would come in handy?

 

Another question...

Why are bigger injectors really needed? How come you cant just add fuel with a fuel pressure regulator (since I already have one)...and take away fuel as needed..and also add fuel with the SAFC as needed.

For example...if stock fuel pressure is at 36 PSI (w/ hose attached) with 240 CC...you could raise the fuel pressure via a regulator to 46 PSI injectors..which is roughly 30% more fuel.
So you could have 0 boost at -30% and +10% at full boost...taht would work right?
Same concept just with stock injectors.

 

That's where dynos and wideband A/F sensors come in handy.

Regarding the fuel pressure / stock injector idea...
first off, stock fuel pressure is closer to 50-55 psi. Running 7 psi boost safely requires that you be able to deliver at LEAST 50% more fuel than a stock engine at WOT. So that would put your fuel pressure up to around 75-80 psi; around there the output is WAY down on a stock fuel pump. Check the Hondata web site; a stock pump will only flow 200 hp worth of fuel at 75 psi. So you're back to adding a bigass inline high pressure fuel pump. You can do it, sure, but the bigger injectors are a lot safer solution.

Also you need to note that the ECU will throw a MAP code if you try to use the VAFC to push more than +5% since it accomplishes this by boosting the map voltage to the ECU and more than +5 will push you up over 3 volts.

 

55 PSI? Theres no way stock fuel pressure is that high...is there?
Wit hteh hose connected it is at 32-36 PSI and with hose disconnected 36-42 PSI per Helm's manual. I have mine at 48 PSI with hose attached to fuel my cams.

Also...I have added 10% fuel with the S-AFC in the past with no problem..no check engines lights or anything.

 

Perhaps just a discrepancy between our cars... I often forget that there are many different cars and engine combos on this board.

 

thats what i do with my honda..i run two honda map sensors. It has also seen 15psi boost over sea level..so it reads at least that much. The honda sensors are a 2bar..so it should read to 14.7psi. (i am pushing the limit a little )

liam

 

That is one of the coolest ideas i have ever heard of. Awesome work. I think i might try this...it should give very good throttle responce and good gas milage at the same time (tuned correctly of course)

liam

 

Other sensors exist. want 15 psi? GM 2 bar.

want 30 psi? GM 3 bar.

I am going to runa 3 bar on the car i am working on... Ill let you guys know how that works out.

 

Geoff...but how will the AFC recognize more voltage?
The TPS goes from 0 - 5V...and 5V is around 11-12 PSI as stated.
So if you have 16 PSI...it would be like 6V for example..and the AFC wouldnt recognize it...right?

 

My B18C1 and D16Y8 both idle at about 35psi and are at a little over 40psi at WOT just for comparitive purposes. And dbman, the V-AFC has options for different types of TPS's which use different voltage amounts, so perhaps one of the other ones would be better suited for te V-AFC to determine boost? Gotta try that out

 

Thats good to know...any idea what the other voltage ranges are?

 

It's in the manual

 

Hehe... now we're getting somewhere.

 

The GM is *still* 0-5 V, its just on a different scale.

In that case, 14.7 psi is 5 v.

Use a 3 bar? 29.4 psi is 5v

get it?

 

Ahh..I gotcha

Hey Geoff..maybe a turbo is in the near future

 

Hehe... Geoff beat me to it; I just got back from looking up the V range on the GM sensor to make sure they were still on the 5V scale. That being the case I might be tempted to go to a dual-map sensor myself.

Another note... this may be hard to do, but the TPS input on the VAFC is auto-calibrated on the Cylinder # / TPS type selection screen - you have to hold the throttle at 100% and then at 0% so it senses your range. Since ours are all set to max at 4.5V because of our TPS sensors, we need to convince the VAFC to extend its range out to 5 volts - we need all the resolution we can get. If you can just patch a 5V source to the input while you're on this selection screen, you could force it to calibrate this way.

 

exactly what i had in mind...

Or you could just run 30 psi into the 3 bar using a regulated air source

resolution is definatley key tho. So for most all applications the 2 bar will work the best becuase it is going to be slightly more accurate. Gott remember to retard the ignition timing. This makes a ton of sense to go with a j&s 2.0 if you dont have an MSD BTM. ahemmm PAUL!!!

 

I though you could replace your honda sensor with a GM 3bar sensor and still run the stock computer with no mods....so is this not correct?

So lemme give you an example. Lets say i am boosting 12psi on my stock honda MAP sensor which gives voltage to my erl mf2 (AIC computer). If i swap the MAP to a GM 3bar sensor am i going to have to reconfigure the erl mf2 because 12psi is giong to be a lower voltage with the GM sensor then with the Honda sensor?

liam

 

If the ERL MF2 bases it's boost calculations on what the MAP signal tells it, then I'd assume yes you'll have problems because what the ERL was designed to recognize and what the MAP will be showing will be two different things. The ERL was designed to work on the stock Honda MAP values, not GM's. Make sense?

 

Hello!

 

I'm pretty sure the ERL MF2 comes with its own 2 BAR MAP sensor.

 

For everyone who's been watching this, I'm putting together a little personal (read: unreliable) website to post the ideas, diagrams, etc. G has emailed me his own electronic MAP limiter schematic which seems very simple, effective, and cost around $20 max to build, although the more we talk about this, it seems an auxiliary GM 2 or 3 bar map sensor would still be the best solution for this plan. I'll post the address when I get the site setup but the address will most likely be dbm.myip.org but this will be a dead link until I get my server running on the desktop.