adjustable vaf bypass valve. give advise please

[aaronthehic]

I have read about alot of work being done to remove the restrictive vaf meter giving apparently 11hp at the wheels <P>My idea is to make a mechanical timed bypass valve to open up when the vaf would become restrictive.<P>I would cut my old intake up and remove one of the butterfly valves with its housing <P>connect this to my banana tube inlet and build adjusting screw to adjust air flow<P>then connect the two feed lines from the vris<BR>two my third vris valve using two diodes to stop back feeds <P> so as the motor reaches 4K this valve would open and stay open until 6.5K<P>any comments are appreciated.

[David Coleman]

letting unmetered air into the engine is quite possibly the worst thing you can do. It would register as a HUGE vacuum leak.

[curtklze]

Actually that is a good idea.<P>but you have to make sure that the valve opens only after the VAF has reached the end of its travel.<P>Under WOT the VAF will bottom out and the computer will just go in to a fixed set of parameters for fuel and timing.<P>At that point the air is not being metered because the sensor is stuck against the back of the housing by the incomming air.<P>I would put a micro switch on the throttle so that the valve would only open at wide open throttle and also make sure that the valve dosent let too much air in or the sensor return spring may push the sensor back and that would screw up the fuel and timing .

[pelado]

This has been discussed before, however I don't know if it could be found without a very complex search........<P>Like Dave said, bad idea. <P>True, this would add more air at WOT and the VAF is ignored by the time you get to WOT anyways but...tuning this thing would be impossible without some complex control system. How do you expect this to work, open this butterfly at WOT leaning out the mixture until you reach pre-ignition and the PCME retards the ignition timing due to the knock sensor? That's not much control if you ask me and is liable to result in a trashed engine.<P>Plus, like Curt said, letting in more air between the VAF and the intake could upset the differential pressure across the VAF causing it to close and totally screwing everything up.<P>You'd spend a lot of time (and money) trying to get it to work. This is money that could have been spent on nitrous oxide (more oxygen, same idea) or a stand alone computer system that uses a MAP sensor and ditches the VAF.<P>Thumbs up for thinking outside of the box but IMHO I don't think it's worth pursuing.<p>[ August 31, 2002: Message edited by: pelado ]

[aaronthehic]

I think a wot switch is a good idea because at wot the air meter would be ignored anyway I beleive.<P>Then at wot the car runs it's preset maps which are very rich on my setup.<P>I would then have the valve open with 1 maybe both vris <P>my a.f. meter will show how the mixture is to prevent leaning and I can adjust acordingly.<P>As far as price I own the a-spec intake so that is free . leaving me to buy 2 diodes<BR>etc.<P>I have thought about n2o and I don't think it is worth what I need + I don't trust it unless I did a muiti port injection to prevent intake backfire

[David Coleman]

I maintain my position against it. You might as well drill holes in the intake runners and put valves on them to get more air in. or just kinda set the intake manifold on the studs, not really torqued down...

[Zoso124]

plus a A/F ratio will be pretty much worthless on our cheap a-- O2 sensors, and they way are cars are set up if you ever install one, it will just seem to bounce back and forth (lean to rich).

[David Coleman]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Zoso124:<BR><STRONG>plus a A/F ratio will be pretty much worthless on our cheap a-- O2 sensors, and they way are cars are set up if you ever install one, it will just seem to bounce back and forth (lean to rich).</STRONG><HR></BLOCKQUOTE><P>Hence the reason people shell out the big bucks [1000USD+] for wideband O2 sensors, so they get a REAL reading of what's going on...

[pelado]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by aaron the hic:<BR><STRONG><P>has anyone heard dyno results from a set like this , It still makes sence to me that if the part is restrictive you should be able to bypass the problem without losing the balance of the stock setup<P>please continue to post </STRONG><HR></BLOCKQUOTE><P>Aaron, nobody is crazy enough to set this up and then spend dyno time trying to tune it. <P>If you wanna go forward with it, then do so. Let us know how it turns out.

[LiQuId]

If you are wanting to get rid of your VAF than the best thing to do will be to switch it to a MAF. But then you will have to make mods to your E-Prom.

[aaronthehic]

O.k. thank you everybody for posting<P>I am still pondering the proceedure but the unrelialilty of the stock O2 is a problem since they cost 250$ canadian<P>as long as it has not been tried (if it has not) then someone will have to try it.<P>Is their any news on the eprom maf mod since I last searched<P>ie. does it work as well as stock?<BR> <BR> how much?<P>where?<P>last time I checked guys were working on the chipsets to change the signal maf-vaf<BR> [img]shrug.gif"%20border="0[/img]

[pelado]

Only two people came up with a VAF-MAF conversion. <P>The general consensus is that it's just as easy to get a MAF, ECM, and wiring harness from a 98 or later 626 as it is to do the conversion.