Imran21

iTrader: (5)

Hi guys,

I have a version 3 type R on which i have fitted a VF34 turbo. The boost is fine in gears 1, 2 and 3 (1.2 - 1.3 bar) but in 4th and 5th i get a lot of turbo flutter (compressor surge??) at about 1.1 bar after which the boost settles down to 1 bar.

Could this be due to weakening of my DV?? I also have the large silicon turbo intake pipe & a recirc Forge DV but i've had these for a while now and never had this occurrence with the VF 28 i had on the car prevciously. And why does it only happen in 4th and 5th gear??

Cheers,
Imran

apac

iTrader: (2)

i get this sometimes fairly randomly. i would love to know why it happens.

The rookie

iTrader: (1)

Compressor surge is caused by having too much boost at too low a flow rate, think of it like an aircraft wing, fly too slowly and the angle of attack of the wing to maintain level flight becomes too high and it stalls, in the same way the airflow over the turbine blads is too slow for the amount of work (boost) so the airflow stalls off the back of the blades (many seem to think the turbo stalls like an engine - aka stops - not true at all of course) and makes the surging ch-ch-ch-ch-ch noise. (not wastegate flutter or flutter at all.

If the DV was weak and leaking this would increase airflow so help prevent surge - so its not that!

Most common cause is aftermarket turbo intakes (as scoobynet project spec C) as the designs are often poor on approach to turbo and what the turbo needs to try and reduce the likelyhood of surge is nice even laminar airflow with no tight bends on entry to cause turbulance!

I think the answer in yor case Imran is to stop it overboosting to 1.1 bar! Or at least stop it boosting too high until the airflow (engine speed) is high enough to prevent surge!

Simon

Imran21

iTrader: (5)

Thanks for that Simon.

So does it mean that my engine speed is low only in 4th and 5th as it only happens in those gears? Its fine in the first three gears and boost is 1.2/1.3 bar in those. And how do i increase engine speed then?

Cheers,
Imran

petedotuk

I take it you only get the surge when cruising in said gears then Going WOT?
The main culprit will be the turbo intake, I used to get it really bad(could feel it and hear it) and my mapper couldn't get rid of it. It would start @ around 1bar then as revs picked up & the engine was able to use the air the turbo was suppling it dissapered, I was running 1.5bar @ the time.

I changed my mapper to Andy F who was able to smooth it but not remove it. It wasn't present on map A @ wastegate pressure. In my case it was the induction kit that was creating the surge.

mr_D

iTrader: (12)

i get this. im running a vf35 and silicon intake. with no dv!

Imran21

iTrader: (5)

Hi Pete,

Yes, I get the flutter whether i'm cruising and then WOT or even just flat out through all the gears - but only in 4th and 5th. And i also have an induction kit as well...... so from the looks of it this is a normal occurrence??
But why did it not happen when i had a VF28 on the car which would give me boost of 1.3 bar in 4th and 5th with no issues??

mr_D

iTrader: (12)

the acurator on the vf 34/35 is a bit weaker i believe. i done a pressure test on my mates vf28 compared to my vf35, his would hold on 1.5 bar and mine would drop rather quick at 1.5bar. this i believe is what causes it!

The rookie

iTrader: (1)

Rubbish, I've told you what causes it!

You get it in higher gears as the rpms you get it at you rarely hold in lower gears as you accelerate through.

Most silicon intakes are shocking and much worse than the standard part they replace, I suspect you won't get surge (forget 'flutter' or wastegate flutter' its not that and it leads to people misunderstanding what causes it).

You're more likely to get surge on a bigger compressor wheel as the air velocity is reduced (larger flow area, approx same flow = lower average velocity).

To alleviate it get it mapped so you run less boost at those speeds where you get it (and the IHI isn't robust to surge, it will knock out the thrusts sooner rather than later), longer term sort out the route cause, usually poor flow into it, so cruddy intake pipes and or induction kit.

Simon

petedotuk

If you go back to standard induction & turbo intake you will eliminate the surge. The standard equipment is more than adequate to supply the correct amount of air that your turbo can demand. I found the surge very annoying and as I said before the only time it wasn't there was when running wastegate pressure which was no fun.
As Simon above has said the 34 is bigger so is pumping in more air than the 28 did @ the lower RPM's.

What size is your turbo intake? 2.5" or 3"?

This doesn't mean if u fit a bigger turbo you'll get surge. I recently fitted a MD321T with an agency power hard pipe turbo induction and have no surge issues. It's all about fitting the right parts @ the right time.

The rookie

iTrader: (1)

Agreed Pete.....