Jump to content
SAU Community

Recommended Posts

I have noticed this a bit it the past with my car but it became more of an apparent problem today going up a long steep hill. When at full boost or accelerating I have no probs, but when sitting at a constant speed on boost (not full obviously) say going up a hill the boost level will start bouncing up and down and you hear a bov type noise (I presume it's the bov's opening a closing), it's almost like the controller or the bov's won't hold low amounts of boost for a long time. Anybody experienced this problem before or have any ideas what it could be due to?

Sorry about the poor explination, I can't think of a better way to explain it :ninja:

Link to comment
https://www.sau.com.au/forums/topic/132061-boost-fluctuation/
Share on other sites

I have noticed this a bit it the past with my car but it became more of an apparent problem today going up a long steep hill. When at full boost or accelerating I have no probs, but when sitting at a constant speed on boost (not full obviously) say going up a hill the boost level will start bouncing up and down and you hear a bov type noise (I presume it's the bov's opening a closing), it's almost like the controller or the bov's won't hold low amounts of boost for a long time. Anybody experienced this problem before or have any ideas what it could be due to?

Sorry about the poor explination, I can't think of a better way to explain it :D

Hello Kyle,

Could you have a faulty blow off valve?

Have you done any work on the intercooler or exhaust lately?

Sound like a block of some-sort.

Is your petrol pump making funny noises on start up and shut down?

This can be caused by fuel delivery also.Less fuel for motor to keep turbo's spooling.

Does it feel like it wants to stop and go...stop and go when the turbos play up?

The other thing it could be is boost controller ,do you run one?

But then again could be compressor surge...as Paul has said.

Good luck.

Hope I have been some help

paulr33 - I though it may be compressor surge or flutter(dunno what that is, is it the same as comp surge :() just been waiting for someone to say it to see if it's a possiability.

700HP-GTR33 - Haven't done any work on any of the intake stuff since i had the car but then again it has also been doing it most of the time i have had the car so may be worth a look, is there anyway to check the bov's off the car to make sure they are working properley?

Pump only makes funny noises when it's at high rpm/boost I know that thats the pump surging though cos it can't supply enough fuel to the engine, car despratley needs injectors, pump, fpr, and a new tune, it's the next thing I need to do on the car. Though could this same thing be causing this problem at low rev's injector duty is only about 30% ish when it does it?

Does it feel like it wants to stop and go...stop and go when the turbos play up?

Yep thats exactly what it feels like.....

Car has a Blitz Dual SBC and a Power FC.

Thanks heaps for the help no doubt I will have a million more questions :(

Edited by Omurru
where is the hiflow from

Woops forgot to answer this one, no idea on where they are from I don't even really know the specs of them, the turbos were done by the first aussie owner of the car who had it before the guy I bought it of had it. When I bought it I was told they are 'custom turbos capable of running 2bar and holding 1.5 all day and they have upgraded steel wheels'. I bought the car for the engine not for the turbos though...there the cheap part.

hiflows sometimes can be associated with compressor surge.

this is commonly seen as fluttering whilst ramping up or coming boost.

compressor surge is actually boost past the compressor wheel is higher than what the compressor map can supply. ie the compressor map says the max flow in the ideal scenario is 19psi but when its ramping on boost it actaully peaks past 22psi so the compressor wheel surge's

start by checking the basics : fuel flow, fuel pressure, check spark plugs, intake etc.

Then move on to check BOV after you are sure everything else is fine. If you don't know how to test the above things then you will waste a lot of time trying to solve your problem.

hiflows sometimes can be associated with compressor surge.

this is commonly seen as fluttering whilst ramping up or coming boost.

compressor surge is actually boost past the compressor wheel is higher than what the compressor map can supply. ie the compressor map says the max flow in the ideal scenario is 19psi but when its ramping on boost it actaully peaks past 22psi so the compressor wheel surge's

Didn't he say it only does it at around half boost (~0.4 bar)

I doubt the turbo would be surging at this level.

no he said its fine on 0.50 bar but no ok on 0.90bar

nah it is the other way round when at max (0.9) it's fine (i think i haven't really checked it when not accelerating) but when not accelerating and sitting at say 0.5 the problem occurs....

now thats wierd

yup....theoretically could you check the bov's of the car? ie. supply pressure to them and then cut it of somehow to see if they were holding??? I work at for Qantas so I should be able to rig something up to test them, just wanna know if it's a waste of time or not....as not really sure exactly how they work, never looked into it.....

other than that might do some research on compressor stall....thanks for the help as well guys!

I have exactly the same problem however mine is in a rb20det with rb25 highflow turbo. Goin up long hills on the highway if i build boost slowly, at about 5psi boost gauge will bounce up and down (max boost is 10psi atm). But once it it hits 10psi everything is fine. Mine usually only does it between 3000 and 4000rpm and more often in high gears, eg 4 and 5. For the moment i have been putting up with it but would love to find the solution.

AFM?? they can do cause that.. but not sure about under load

Hello again,

AFM's.....give them a clean and check connections.

Sensor's O2 might also cause this problem.

When have you last checked your spark plugsand coils?

Last car I had Mazda 929 had corrossion on the leads, it would play up when I was at low revs.

At high revs the car would run fine.

You really need a tune....get one before it causes bigger problems for you.

The tuner will identify your problem.....it should be apparant under low load conditions.

Cheers

Will give the AFM's a clean and a check, I know one of them is wired up pretty dodgely....Spark plugs were changed about 300k's ago there BKR7E's gapped to 0.7mm, coil packs are about 5000K old.

Might be a good time to get that new pump and injectors and get a tune. It was tuned by Godzilla Motorsports just before I bough the car but am unsure of any details of the tune appart from what the dyno graph shows me....

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Let's be honest, most of the people designing parts like the above, aren't engineers. Sometimes they come from disciplines that gives them more qualitative feel for design than quantitive, however, plenty of them have just picked up a license to Fusion and started making things. And that's the honest part about the majority of these guys making parts like that, they don't have huge R&D teams and heaps of time or experience working out the numbers on it. Shit, most smaller teams that do have real engineers still roll with "yeah, it should be okay, and does the job, let's make them and just see"...   The smaller guys like KiwiCNC, aren't the likes of Bosch etc with proper engineering procedures, and oversights, and sign off. As such, it's why they can produce a product to market a lot quicker, but it always comes back to, question it all.   I'm still not a fan of that bolt on piece. Why not just machine it all in one go? With the right design it's possible. The only reason I can see is if they want different heights/length for the tie rod to bolt to. And if they have the cncs themselves,they can easily offer that exact feature, and just machine it all in one go. 
    • The roof is wrapped
    • This is how I last did this when I had a master cylinder fail and introduce air. Bleed before first stage, go oh shit through first stage, bleed at end of first stage, go oh shit through second stage, bleed at end of second stage, go oh shit through third stage, bleed at end of third stage, go oh shit through fourth stage, bleed at lunch, go oh shit through fifth stage, bleed at end of fifth stage, go oh shit through sixth stage....you get the idea. It did come good in the end. My Topdon scan tool can bleed the HY51 and V37, but it doesn't have a consult connector and I don't have an R34 to check that on. I think finding a tool in an Australian workshop other than Nissan that can bleed an R34 will be like rocking horse poo. No way will a generic ODB tool do it.
    • Hmm. Perhaps not the same engineers. The OE Nissan engineers did not forsee a future with spacers pushing the tie rod force application further away from the steering arm and creating that torque. The failures are happening since the advent of those things, and some 30 years after they designed the uprights. So latent casting deficiencies, 30+ yrs of wear and tear, + unexpected usage could quite easily = unforeseen failure. Meanwhile, the engineers who are designing the billet CNC or fabricated uprights are also designing, for the same parts makers, the correction tie rod ends. And they are designing and building these with motorsport (or, at the very least, the meth addled antics of drifters) in mind. So I would hope (in fact, I would expect) that their design work included the offset of that steering force. Doesn't mean that it is not totally valid to ask the question of them, before committing $$.
    • The downside of this is when you try to track the car, as soon as you hit ABS you get introduced to a unbled system. I want to avoid this. I do not want to bleed/flush/jack up the car twice just to bleed the f**kin car.
×
×
  • Create New...