still having the same issue.

[FE3-323]

still having the same issue. under heavy acceleration i.e. i give it WOT it cuts & backfires type of thing on me. overboost light flashes.

fully cleaned GTX injectors
plugs gapped to .032
No clue on my A/F ratio until I can get a wideband reading.


WTF is the issue?

[yvanlavoie20]

like small leak on your waste-gate ??? on mine until the hose is securely hooked on wastegate it make the same thing

http://members.cardomain.com/yvanlavoie20

http://www.fordfestiva.com/members/Yvan/yvan.htm

http://www.fordfestiva.com/multimediaandfun/gallery/yvan/yvan's_bp_turbo_swap.htm

http://www.fordfestiva.com/forum/viewtopic.php?t=4590

[Lex]

You are hitting the stock boost cut. Remember that this cut is hit when the VAF opens up past a certain point. You can raise the cut by tightening the VAF spring but you will also run the risk of leaning out.

Get a boost gauge. You are running a VF10 hybrid which is bigger than the VJ20 with the same sized wasteage. The VF10 pulls more air through the VAF at the same Psi than the VJ20 did causing an earlier overboost conditions. If you haven't ported the wastegate, do so now because it is a must.

Also if you have a boost controller completely remove it. Make sure your lines are tight etc etc and that your wastegate actuator works.

[elscotto80]

Might also want to try to gap the plugs even less. I had a similer problem, although not boost cut, just cutting and bogging when I would floor it and then when it got to the upper RPM's it would bog. Try .028.

[Bax]

To deal with the boost cut you need some sort of piggyback, a wideband and messing with the vaf.
When the vaf can't measure air anymore (wide open flap) this is when it happens.
You must tighten the tension of the flap, so the ecu thinks there is less air coming in, then with the help of the wideband, monitor and adjust the mixture with the piggyback to have the desired a/f ratio. I hope you have a good fuel pump too. :D

[FE3-323]

well here's what i figured out. Since i rerouted the fuel pump opening relay to the VAf & removed the ECU's control over it, the ECU thinks its cutting fuel but really isn't. Which is the cause for the backfire. i've come to the conclusion that im going to drill & tap the AFM housing just the same as the stock NA meter. & insert the stop screw system so that i can have control of how far the flap is allowed to open. this should allow me to stop the door just before the ECU would normally see boost cut, & all without having to adjust the clockscrew tension & mess up the A/F. This should effectively allow me to run as much PSI as I deem until my A/F ratio becomes unstable to support the psi.

thoughts?

I'll be replacing my fuel pump on friday with a NEW walbro, My old one was effectively junk & did not move any fuel.

as far as the plug gap goes, im fairly certain I could open the gap somewhat larger to increase my flame front, & make more power. its possible that I did not even need to gap them as small as I did.

[Lex]

well here's what i figured out. Since i rerouted the fuel pump opening relay to the VAf & removed the ECU's control over it, the ECU thinks its cutting fuel but really isn't. Which is the cause for the backfire. i've come to the conclusion that im going to drill & tap the AFM housing just the same as the stock NA meter. & insert the stop screw system so that i can have control of how far the flap is allowed to open. this should allow me to stop the door just before the ECU would normally see boost cut, & all without having to adjust the clockscrew tension & mess up the A/F. This should effectively allow me to run as much PSI as I deem until my A/F ratio becomes unstable to support the psi.

thoughts?

I'll be replacing my fuel pump on friday with a NEW walbro, My old one was effectively junk & did not move any fuel.

as far as the plug gap goes, im fairly certain I could open the gap somewhat larger to increase my flame front, & make more power. its possible that I did not even need to gap them as small as I did.

I would not simply stop the flap from opening like that because you don't know how far you want it to open in the 1st place. I especially wouldn't do this without a wideband installed.

[FE3-323]

meh, it will be alot of testing involved. Creativity makes the greatest things. Perhaps there is a voltage that I can figure & compute into the position of the VAF flap, so i know where overboost cut is supposed to be. like i said tho, alot of testing.

I stuck a wideband in today &got a 12.5:1 A/F ratio at the leanest point. so i still have a little room for more boost. NOTE I wont be increasing the boost unless its on they dyno with the wideband installed so i can see how its acting.

[Lex]

Also remember that the VAF works not only by reaching a steadystate voltage but also by acting as an underdamped system where it "slams" past its steady state value on sudden acceleration etc.

Test it out and see what happens - let us know. Did you figure out how much boost you are making?

[FE3-323]

I take that back, its not going to be difficult at all. Looking at the circut board i can see where the slide sets its limit @. if the slide touches the last metal pad poof!, overboost. so simply drilling & tapping the hole & the problem will be solved.
15PSI here I come.

[FE3-323]

8.5PSI is what i was seeing today on the dyno. that was just letting the wastgate do its thing. no boost controller inline.

[Lex]

I still don't think it's a great idea .... but I dont want to get into the discussion of how the engineering of it all works - just be careful with it all. I ran 16 psi on the BP55 ECU without hitting boost cut with the RX-7 VAF

Can you post a pic of your VAF opened up if it's the GTX one?

[FE3-323]

all of the internals on the AFM's are the same. adjusted differently, yes but they all look the same inside. nothign special to see if you've ever opened one up.
im moving more air then normal. & the "Y" code bp26 AFM doesn't like it too much. dave told me that the stock BP26(GTX) system sends a signal @10PSI to cut because of overboost.

207.27 WHP 189.74 FT. LBS @8.5PSI can't wait to see 15 PSI

[Lex]

have you tried tightening the VAF flap at all?

Those are some nice numbers. Im surprised the torque is not higher though. Is this with the cam setup you have in the other thread?

[MD323]

wow thats good #'s dood, this is definetly turning out to be an interesting setup you have