A BOV/hiccup question

[old skool]

I've got a Blitz Super Sound atmospheric BOV. I have been having problems with a hesitation or hiccup under medium boost (~3-5psi) while going up an incline, usually freeway driving. It does this on flat ground under load most of the time also. I was doing some searching and saw that this hiccuping is most likely caused by the BOV itself. My question is, will adjusting the rate at which the BOV opens/closes relive some of this? From doing a google search i came accross this: http://www.alltrac.net/tuning/bovfaq.html, and it seems that the spring tension may be a little bit too high for the AFM. Also, if it is better for me to just get a recirculating BOV, what kind, if any, would match up to the blitz flange? Thanks!

Related mods: Lex/550, 12psi w/ AVC-R, WBo2 - AFRs look really good (14.5-14.7s @idle, low low 9s WO) & NBo2 - constantly rich...full bars like AT&T, Aeromotive FPR ~30psi Vac off.

 

[DBN]

Recirculated BOV is always better. Low 9 AFR at WOT? That seems a little too rich to me. I was under the impression that 11.5 to 12 was good. I'd also like to hear about this hiccup ordeal as mine has been doing this lately.

 

[hvyman]

recirc is only good for between shifts and letting off to idle. 9s are way to low. could be the bov itself havnt heard to good from the blitz bov other than sound.

 

[old skool]

that's kinda what i'm thinking, that the BOV is causing a rich condition due to not letting enough pressurized air out at low boost. is this a correct assumption? I know that i should get recirculating one, but as for the time being, is that a good temporary fix?

 

[jdub]

The only time a BOV vented to atmosphere causes a rich condition is when you let completely off the gas petal. Air (which the ECU expects) that would have been reinserted back into the intake is missing...a momentary rich condition occurs. At idle the engine can't handle it and can stall. A engine speed above idle, the BOV should be closed during acceleration...under boost and you let off the throttle the BOV opens to prevent compressor surge. If the BOV is opening under boost, it would act like a boost leak.

Looks like to me you are running too rich at mid to WOT...11-11.5 would be what you want to see. Something doesn't make sense...you said FP was 30 psi vac off. That's less psi than TSRM spec. What is it with vac on? (that is the normal condition after all)

Do you have any ECU codes?

 

[old skool]

no codes...shit, i'm sorry, i meant van on. What should it be ideally?

 

[jdub]

With the Lex/550 combo, it depends....drop it down to 25 psi (vac on) and pull the EFI fuse for a reset. Drive and monitor AFR.

 

[old skool]

check, I will do that now and get beck to you shortly.

 

[old skool]

wouldn't want to stay running for the first 2 trys. Revs dropped below 500 so i held it up around 800 until the wbo2 counted down, then it stayed running. AFRs were high 15s at normal cruise and dropped into the low 10s WOT. Still had the hiccups.

 

[jdub]

Drive it a day or two to let the ECU relearn. Stay out of any sudden jump from cruise to boost (especially if you have no EGR installed). If it stays like this, bump FP 2 psi higher.

Does the Lex still have the adjustment screw installed? Is it in the factory position or have you adjusted it?

 

[old skool]

i will do that.

actually, haven't looked at the AFM much. i haven't touched it but the previous owner may have. Didn't have the 550s when i got it so who knows if there was something done to try and "compensate". i'll check it out, maybe post a pic if i feel it's prudent.
Thanks maing.

 

[old skool]

^so the hiccups are pretty much gone as far as i can tell..except in 5th gear it does it a lilttle coming up from cruising speed. AFM screw is all the way in i believe...about 5mm or so into the AFM body, doesnt look like it's been moved. I't still rich than a bitch though. saw a 9.2 on the wb today..not quite full on goose, but a hard accel up to ~5k and let off.Oh yeah, j-tube is bypassed. Would that dashpot mod help with the "rich than a bitch" situation?
Hope you can uderstand all this: http://www.supramania.com/forums/showthread.php?t=7364&page=281

 

[jdub]

This is with FP at 25 psi? What are your AFR's at idle & cruise?

The dashpot mod Brad did will not do anything to help this.

 

[old skool]

it kept stalling out @ 25 psi so i raised it to 30 and the prob went away, idle returned to normal, etc... but my AFRs at cruise are in the mid 14s, at idle anywhere from 14.3 - 15.2

 

[jdub]

So, you put it back to the 30 psi you started with and it went away?

You are still too rich at WOT...I would drop FP to 28 psi. You are looking for a balance. Try turning the AFM screw all the way out on it's engagement range.

 

[old skool]

yeah, i dont know if the dude never pulled the EFI fuse when i he adjusted the FP, but yeah, it went away. I'll drop it down to 20. What kind of symptoms will i see if turning the AFM screw all the way out doesn't go over well? i think earlier you said i should be seeing AFRs in the 11 range at WOT? Is there another fuse i should pull after adjusting the screw?

 

[jdub]

Turn screw out = more bypass air through the AFM = leaner condition. Balance FP with this screw to get the AFRs where you want.

 

[old skool]

aha, thanks...yeah i'm definately new to this whole thing.