graniteguru

iTrader: (1)

I have just completed my S5 NA to JDM Turbo conversion. Complete restoration on car as well. I am good to go except that I am getting an extreme hesitation when I accelerate (even mildly) and try to go into boost. If I feather the gas pedal lightly I can accelerate without going into boost up into the rpms without a problem. The minute I try to boost, it starts to spit and sputter and backfire through the intake. I am thinking that I have a vacuum hose going to the wrong place, my BOV on backwards or something. What I have on the car

N370 Pressure sensor
Stock S5 Turbo
3" downpipe without front converter going into a monza duel exhaust
air pump gone
Stock BOV
Stock AFM
Stock Intercooler

I have attached some pictures of my set-up. I searched and can not find a good picture to help me with where to run the hoses and such for the Cone filter/MAF and BOV.

Any help anyone?

Craiger

iTrader: (1)

It looks like you have a check valve in the vaccume line going to the BOV. The small line going to the BOV can simply come from the nipple right below the BAC valve on the UIM.

Ditch the check valve if that's what it is. It is not needed there and can and will cause problems whichever way it is pointed.

sharingan 19

iTrader: (16)

I had what sounds like a similar problem, but it only happened when I tried to boost in 5th gear. It ended up being a combination of fouling/poor connection plugs and a minor fuel leak.

RotaryRocket88

iTrader: (7)

Yeah, those are definitely check valves off of the secondary throttle setup. Get rid of the one on the BOV line and the one on the boost sensor line. Depending on which way you have the one on the boost sensor, you're probably denying air to flow to it, which is exactly what happens when you go over atmospheric pressure (boost).

graniteguru

iTrader: (1)

Thanks for the replies. Unfortunatley, I put the check valves in thinking that I needed them there to solve the same problem. I had the problem before the check valves were installed. I will remove them though. Could it be that I have capped off the extra nipple on the turbocharger? This line feed the waste gate. Could it be a waste gate problem? This used to go to the boost control valve. According to rotary ressurections write up on removal of emmisions, I can cap this because it is used to boost pressure. With a downpipe, it is supposed to remove the need for this valve.

Is the BOV pointed in the right direction? Right now the arrow is pointing toward the intake inlet on the turbo on the pipe. Should it point the other direction?

mrduece88

What fuel pump are you running? It could be running lean under boost

graniteguru

iTrader: (1)

I replaced the NA with a turbo assembly fuel pump. I did not test the pressure however. I bought a 220 lpm walbro pump that I did not install yet. Maybe I should go ahead and do that. What should the stock pump run for pressure?

RotaryRocket88

iTrader: (7)

I doubt it's a fuel pump issue. If it's running lean enough to keep it from making it to redline, then the amount of knock he'd be getting would have blown the motor already.

Craiger

iTrader: (1)

well, get rid of the check valves right away, as they won't help your situation at all. Next, check the rubber gourments around the bottom of your injectors. If one or more of thoes are badly cracked or missing it can give a symptom like what you describe.

graniteguru

iTrader: (1)

I will go ahead and take the check valves out. The grommets are new. I replaced them with the rebuild that has 100 miles or so on it. Does anyone have a quick run down on the set up of the CAI and the BOV and the pressure sensor. Maybe something is awry with the set up.

I have the pressure sensor hooked up and "t"d to the aftermarket boost gauge and the BOV to the nipple just above where I removed the BAC. I then have the BOV hooked to the intake tube after the MAF and before the turbo inlet. Does this sound right?

HAILERS

How much boost do you see when this crummy running happens?

Have you ever taken the vacuum line off the boost sensor and with the engine idling, felt for vacuum on the hose? Maybe it's not there.

graniteguru

iTrader: (1)

Hailers, I will pull the vacuum hose off of the sensor to check for boost. I do know that the boost gauge that is registering is t'd off of the same line as the sensor. vacu I can't remember exactly what boost I achieve when it starts sputtering, but I think that it only climbs to zero. Something that might help, is that when it starts to go into boost, and I back off the gas and feather the throttle ever so slightly, it will smooth out a little and then I hear the BOV go although it seems that I am no where near maximum boost.

Do you think that I need to re-connect the nipple on the turbo again and re-install the boost assist valve back in?

Craiger

iTrader: (1)

The BOV doen not open when you hit max boost. It opens when there is more pressure in the IC piping than in the manifold. The wastegate is used to keep boost under control.

If you hear your BOV opening then the valve may be defective or it is not hooked up to a good vaccume/boost source.

Are you 110% sure that none of the rubber gourments fell off the injector while your were installing the fuel rail? If one is missing than it can cause a symptom very similar to what you describe. If I were you I would quickely pull the rails off and check to make sure they're all there.

graniteguru

iTrader: (1)

It could be a defective BOV. I have the three items hooked up to the one nipple on the UIM. Maybe it is not strong enough. I will get a vacuum checkerto check the BOV. I probably should replace the stock BOV. I bought this one used for the conversion, but really don't know what I have. I will pull the UIM and check the grommets on the injectors. I have now replaced the fuel pump with the walbro HO fuel pump and the check valves and will try that in the morning. Does anyone know a decent BOV that won't break the bank?

Craiger

iTrader: (1)

The stock BOV is actually pretty decient at least for stock applications. If you feel the BOV is defective then you might just want to pick up another stock one. If you are going to pick up another one get something that is reciculated so that you don't go stupid rich when you shift or lift off the throttle.

graniteguru

iTrader: (1)

Thanks. Not knowing a whole lot about the BOV, I guess they sell different ones for the re-circulate type or is it just that you take the exit pipe on the BOV and put it back to the intake pipe just before the inlet on the turbo?

Craiger

iTrader: (1)

Yes, rather than venting the charged air to atmosphere it recirculates it back into the TID after the MAF. Not all valves can be recirculated... if the valve can be than it will say in the description.

jamesallen

graniteguru,

I am having a similar problem with my car. Although, it's not and RX, but same problem that when I give it some gas, the turbo kicks in and then my car starts to splutter away and the fuel pressure starts to dance. I'm not sure if you have a fuel pressure gauge, but I would suspect if you do not, that a similar problem is occuring

I have a 255 lpm walboro pump, my injector seals are tight, but I have no idea about my BOV in terms on functionality (which is something I am looking in to).

Keep me in the loop as to what you might think is the problem if/when you find a solution to the problem and I will do the same.

Cheers,
James

XR4Ti

Spannersrx7

i would definatly check the timing mine did that as soon as i hit boost because base timing was incorrect it would adjust with boost and be completly wrong

immanuel__7

iTrader: (8)

im getting the same prob as well... its kind of odd... im reinstalling my stock bov and looking at timing as we speak the only other thing thats not connected at this time is the sensor on top of the intake before the therottle i think its the intake temp sensor.. i wounder if that could do it as well?

graniteguru

iTrader: (1)

UPDATE: I checked the BOV and it is allowing air to pass without vacuum being applied. Is this normal? The FSM says to test by applying vacuum and it should allow air to pass. Conversely, does this mean that it should not allow air to pass without vacuum?

FC3Sdrift

iTrader: (5)

is there a way to tighten it up

how do you expect your turbo to boost the atmosphere and your engine lol

it should only allow air to pass when the pressure in the IC piping is greater than the manifold, other wise its allowing metered air to escape, does it have idle problems???

its like trying to fill an air compressor that has a big hole in the side

graniteguru

iTrader: (1)

It has had consistant idle problems in the past. It is pretty smooth right now, but I am having a very difficult time setting the timing, the TPS and the low speed idle rpm. I have seen many discussions in the archives about venting and not venting. I want to keep venting internally with the new BOV. Any suggestions on a relatively inexpensive setup to keep the stock venting?

Craiger

iTrader: (1)

Possibly. As I stated earlier in this thread, the BOV opens when there is a pressure difference. If you want to know if it's leaking you need to apply equal pressure to the nipple and the "in". If you put 5psi through the BOV and nothing on the nipple then there is no reason the stock BOV shouldn't open.

The FSM test procedure tests to make sure the BOV will open when it is supposed to and not cause compressor surge. That test will not find out if the BOV is leaking under boost.

cendo54

iTrader: (2)

just wanted to let you know a friend had the same problem and it turned out to be rubbish in the air bleeds under the secondary injectors. at least i think that's what the part is called. lol

would rev fine w/o load and then not boost under load. exactly same thing on my car. now it runs fine and boosts smooth to redline. just thought to post in case it may be a similiar problem.