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How bad is the rich spike if I put a BOV on my 740?

ZVOLV

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
First of all, I did a search and read all the threads that came up. It sucks that you ask for up to 1000 results, but you can only get 50!

The only thing I found was Gecko mentioned that his 740 would stumble if he blew off at low boost.

I have an HKS BOV already welded into a volvo IC to tbody pipe. I even ran it on my car with the vac hose to my CBV disconnected. I lost a few psi of boost, but the car still ran OK. I just did that for fun BTW.

Is the rich spike during shifts bad enough to cause any real problems? Is it significant enough to harm performance or gas milage?

Hey california guys.... is there such thing as a smog legal BOV that has a CARB number?
 
Thanks Doug. Do the kjet cars run rich with bovs too? I am just wondering if somebody here has run a BOV on a 740 with the LH fuel sys.

There seems to be a lot of heresay about running rich on the lh system, but i havent read any info(besides gecko) from people who have actually run a BOV on the LH sys and their reactions.


I am sure there are plenty of people here that run BOVs on the 700s.

Does anybody have experience with problems using a bov on the 700s? I am interested in any qualitative or quantitative data. (experiences or guage data)

Mine has a check valve in the signal line for the BOV.


BTW I am running a m46 tranny right now.
 
if the engine has a metered air system (the 760 i'm getting has an air flow meter... dont' know what it's called in volvo speak) ...if you went for a BOV thats vented to the atmosphere it's naturly going to go pig rich... the air was mesured before it got compressed... you are suddenly releasing a good bit of air that had already been mesured by the computer saying that the engine would need xxx mount of fuel for that amount of air... because you dump it boom you've gone rich... some cars i know of will stall out they go so rich...

idealy if you've got a car that meters before the throttle body you want to recurculate the air... run a hose from the bov to before the compressor but after the AFM... this will also improve your off throttle turbo response as it's still pushing some air though the turbo... the down side is you are recirclating pre-heated air... it's the price you pay... but the motor won't run rich every time you remove your foot from the skinny pedal

mark
 
Thanks for your post donalson. Please dont get offended if this post seems rude or condecending. I am just interested in hard data and experience not just heresay. You obviously know your stuff though. :wink:

I already am well aware of the AMM situation. I have read MANY posts of people just saying "yeah, you will run rich b/c you have a AMM and it will vent metered air"

Obviously it will run rich on shifts, but how bad is it? I wont put a BOV on if it will hinder performance.


I like dougs comment about how the fuel gets cutoff during decel anyways. According to my innacurate A/F meter is is off the charts lean when I let go of the pedal. (no reading on meter)

I also remember somebody saying the Group A cars would puff black smoke during shifts. ( running rich. for the noobs)

I ran the BOV and it seemed fine to me. I was also running a disconnected CBV, but i dont know if the CBV affected the mixture.


I appreciate any advice given, but please dont just tell me I will run rich. I would like to hear from people who HAVE RUN A BOV ON A 700 w/ LH fuel management. BTW i have lh2.4 not 2.2 if anybody can think of a reason why that would matter. :wave:


I like your idea, donalson, about the air going into the front of the turbo to keep it going. I came up with that thought too. Does that mean a CBV is superior to a BOV because instead it will help keep the turbo going?
 
doh had a good long post but the internet ate it.

basicly... i have no experaince on volvos... and there is no best of bov type stuff :) depends on a few thing some of which i have no clue of.

what in volvo speak does the AMM stand for? toyota speak it's air flow meter (AFM)

thanks
mark
 
guidom12345 said:
Obviously it will run rich on shifts, but how bad is it?
please dont just tell me I will run rich.
Click to expand...

Tell ya what, why don't you try it and tell us how rich you run? Then we'll alll have hard data to refer back to the next time someone asks... (What are you looking for, like percentage rich? Is there a particular number you'll feel happy with?) It's gong to change from car to car anyway....

I have a feeling that the reason you're not getting a satisfactory respone isn't that anybody is stonewalling you, but rather that by the time anyone here put a BOV on their car, they had done away with the stock fuel managment...
 
AMM is generally a hot wire that varies in resistance, sensing the mass of the air as it cools the wire. Cold=low resistance.(High flow/density)

Speed density software approximates air flow using MAP sensors, air temp, RPM, and throttle. GM used speed density conversions to straighten out squirrely Mass-Air Flow meters in some late 80s V6 cars.

Vane Air-Flow meters use a spring loaded door calibrated with a spring, that swings open as air goes by, operating a potentiometer. They generally are used in conjunction with air temp sensors and sometimes have the fuel pump switch in them.
 
I will be installing a DSM 1G BOV on my 92 940. This IS an Air Mass Metered car. I will be venting to the open air untill it stops to work well for me.

The ETA of this project is up in the air, hopefully end of the week. Waiting on free TIG welding you cant really nag someone too much when you want something done for free.

I will keep the board informed on my progress; I will start a new post with voltage readings from the O2 sensor, Pics, and my general impressions.


My thoughs are I'm not going to set it up untill I know for a fact that it wont work... if it works... I just saved myself a lot of trouble. Eventually i will run a closed system, thats my goal.
 
Everybody says I will run rich, but i just want to know if it is enough to skip the whole BOV idea. I should look into the recirculating kit that robin was talking about.....


I just want to know if somebody has run one and had major stalling problems, fuel consumption increase, or performance increase/decrease ETC

I dont want anybody to get the wrong impression about my attitude. I am always grateful for any help. I hope I dont sound pushy or impatient. THe tone and meaning of words can really be misinterpreted when its only text. I am trying to be nice and polite, but I wanted to make it clear that just telling me I will run rich is redundant.

It would be a bummer if people just keep saying that you cant use a BOV because its a AMM car. That has been said enough.



BTW I have heard about 3 or 4 names for the AMM. Air flow sensor, air mass meter, mass airflow sensor. I am sure there is a correct name, but people get the point really fast.


Thanks to all.
 
I have a Greddy Type S blow off valve vented to atmosphere on my 744ti. My BOV is mounted on the IC to Throttle Body pipe, I removed the red and white check valve (no noticeable difference with or without the valve on the BOV). I notice no bogging after the BOV opens, I just end up with some popping out of the exhaust, no major problems. I adjusted tension on the spring so the valve stays closed at idle, car runs fine. I do notice the air/fuel pegs rich for several seconds after the BOV opens, but I have not had any driveablity problems. Mileage only got worse because I gas it everywhere so I can hear the BOV... :-D
 
damn you must pay through the ass for that fuel in honolulu :freak:

i am also curious about the whole BOV issue, i have an 88 760 turbo and i would love to have that noise if it wouldn't **** up the car. nothing like buzzing a honda civic and drowning out their ****ty high revving engines that sound like goddam weed-whackers with a good whoooosh of air. but as mentioned everyone just seems to say "well you're gonna run rich." i feel your frustration bc everyone i asked about it said that too. in the end, i consulted two mechanics who work on volvos and both of them told me it was the dumbest thing i have asked them about yet... but then, they also told me not to buy a turbo because the parts would be more expensive to repair and it's quote "not that much a difference." :roll: after driving a stock naturally aspirated 1990 240, believe me there's a goddam difference. but they were right about the turbo being an expensive fixer.

ok whew i need to stop typing now. soon you can rest your eyes...

basically if you drive the car as your main daily driver, i wouldn't recommend it from all the negative effects it can have, particularly after long-term use (the sporadic bursts of richness cause extra wear n tear). but if this is a car you are looking to have fun with... GO FOR IT!! and as mentioned above, share the numbers with us!

as a final note, i can't see as a burst of richness here and there would hurt performance...i've always been told that running a little on the rich side will give you a little more bang but wastes gas. it probably depends on just HOW rich it ends up running...but maybe im just tired and being retarted by now

in any case, have fun and drive fast!

-Corey
 
Mizugori said:
basically if you drive the car as your main daily driver, i wouldn't recommend it from all the negative effects it can have, particularly after long-term use ... i can't see as a burst of richness here and there would hurt performance...
Click to expand...

So... if you're expecting no change in performance at best, and expecting negative effects on durability...why the hell would you bother?

Why not just get an electronic "BOV effect" speaker, if all you want is the "whoosh" noise?

Seriously, I can almost understand people installing BOVs due to the belief that it helps stop their compressor blades from fatiguing - even though they really just want the noise. But not if you expect nothing but negative effects (and noise) from it. That's crazy.

tim
 
i'm running a BOV on my 760 turbo with motronic ECU.no problems whatsoever.plus even if it does run a little rich,it won't harm the engine with extra boost anyway.It's always better than running lean...
But honestly i can't see it causing me any problems..

My friend is also running a BOV on his 940t with an auto.he also has no problems there.
 
hahaha i love how i dig up a 2yr old thread and manage to restart debate on the issue...

tedium, i dunno what the hell to say. how can you ask why. its simple-because i f*cking can. i WANT that noise. and there are several claims that it may improve performance in subtle areas... more than just the compressor... also the potential harm is minimal... so if it makes some of us happy to get a whoosh noise what harm does it do... if you notice, the original issue raised in this thread was in regard to the extent of the harm in adding a BOV... and no one really substantiated an argument that it is all that harmful. in fact 2 or 3 people have had good results with it.

and as for your electronic whoosh noise suggestion... jesus man why don't i just drive a ford fiesta, and play some recorded V-8 sounds on the casette... come on man...
 
Mizugori said:
hahaha i love how i dig up a 2yr old thread and manage to restart debate on the issue...

tedium, i dunno what the hell to say. how can you ask why. its simple-because i f*cking can. i WANT that noise. and there are several claims that it may improve performance in subtle areas... more than just the compressor... also the potential harm is minimal... so if it makes some of us happy to get a whoosh noise what harm does it do... if you notice, the original issue raised in this thread was in regard to the extent of the harm in adding a BOV... and no one really substantiated an argument that it is all that harmful. in fact 2 or 3 people have had good results with it.

and as for your electronic whoosh noise suggestion... jesus man why don't i just drive a ford fiesta, and play some recorded V-8 sounds on the casette... come on man...
Click to expand...

2 or 3 might have had good results, thousands of maf based cars have had poor results. There is no rich spike in boost, its a rich spike when you let off the gas, and it will frequently stall the car. if you want the noise, put a cone filter and leave things plumbed stock. quite frankly the noise is cool for about 2 days then it gets annoying, really annoying when you're trying to stalk someone and dont want to give the game away (and then there are those who hear the noise and plant it forthright, also not desireable).

harm? like fouling plugs?
Gain? none, in fact it makes the car run worse, there are no perks, it doesnt help the compressor any more than if you run a CBV back into the intake.
 
it will not work ever give it up..this had to have been figured out since 03..i tried and the car won't run right..at all...sounds great...you don't have to worry about the plugs...that sh1t will not work..this post should be dead :slap:

this is benflynn on gregs computer
 
Mizugori said:
hahaha i love how i dig up a 2yr old thread and manage to restart debate on the issue...

and there are several claims that it may improve performance in subtle areas... more than just the compressor... ..
Click to expand...

it is going to hurt performance because you are no longer putting the compressed air in front of the turbo ( wich helps keep the tubo spooled).
 
benflynn said:
it is going to hurt performance because you are no longer putting the compressed air in front of the turbo ( wich helps keep the tubo spooled).
Click to expand...

thats actually not why it helps the turbo spool faster. There is no inheirant advantage to recircing over just venting in a system that meters air after the turbo (Speed denisty or blow through maf)... the venting of the pressure front thats reverting through the intake tract before it gets to the exducer on the compressor wheel is what helps spool the turbo faster... by not stalling it out.
 
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