Baffling Boost

**mcandmar** · 14 August 2007, 17:54

Looks ok to me, off boost its going to look like a NA car. @Idle the intake will be a vacume, as the throttle is opened the vacume will drop off. For example steady speed cruising at 60mph it might read -20, @80mph it will drop to -15 etc as the throttle is opened.

Boost side will only happen when driving with the engine under load, sitting still and revving wont produce any boost. If you sit at say 2000rpms in 3rd gear and floor it you will see the boost spike around the midrange and drop off at higher revs. Or left foot brake on WOT to hold the car back you will see the boost rise.

Not sure on what peak pressure you should see depending on your engine and map. Our AAN with a homefry hits about 1.2 in the midrange and occasonaly 1.3. Think overboost might have something to do with that.

**mcandmar** · 14 August 2007, 17:56

Opps sorry ignore that, i thought your gauge was in bar at first glace

10psi is what .6-7 bar, that dont look right to me. Sure your WGFV is working?

**HPmuirt** · 14 August 2007, 18:13

Firstly...Wohaaaa, is that the biggest boost gauge in the world or were you 2 inches from it when taking the pics?

Any chance you could edit your post and shrink the pics so that we can see them properly?

Everything looks OK to me, although as mcandmar says, you do not mention what the car is actually doing for the revs. For example: -

- 2000rpm static and just revving should be the same as at idle i.e. around -0.6 BAR (about - 9PSI).
- 2000rpm constant speed in any gear should give a reading of 0 BAR (0 PSI)
- 2000rpm at WOT should be around +0.5 BAR (8PSI) and rising rapidly!

Also, you have to remember that you have a gauge with different units on the vacuum and boost sides, which makes it harder to read. Much easier to work in BAR as that is how the car thinks

With a stock 3B, I believe you should not see more that around 0.85 BAR or around 12PSI of boost at WOT at around 3000rpm.

Cheers n

Si

**newsh** · 14 August 2007, 18:15

AAArrggg the images are so big, my eyes ...

**Acidburn** · 14 August 2007, 18:29

Has the car got any mods on it? exhaust,chip,filter?

**urquattro-island** · 14 August 2007, 19:48

hmmm

seems like boost gauge is growing, on increased rpm

**Big_kev** · 14 August 2007, 20:22

given some perspective

should now find the pictures more manageable. Apologies to anyone who now has permenant eye damage or ran to spec savers for an eye test

The car apparently has a chip upto around 280Bhp and has a custom handbuilt exaust in stainless by sportscar services in Dumfermline. Appart from that nothing else has been modified. I have replaced the Waste gate frequency regulator to see if this was the initial problem with the pause but didn't solve it. Have ordered samco set to see if any of the hoses are leaking. Nothing obvious on that side but doing anyway as a good upgrade i believe.

Had a quick look at the turbo blades when i had MAF hose off recently and all look ok.

Plugs, leads distibutor have all been replaced.

**HPmuirt** · 14 August 2007, 21:54

Still need to shrink those pictures, although at least with what you have done so far, I have recovered the sight in one eye

As described earlier, you still need to describe exactly what you see at WOT at 2K, 2.5K, 3K, 3.5K etc. i.e. when the boost starts to build, when it suddenly shoots up, what is the max boost, at what revs does it start to drop etc.

Do this on a long hill in say 5th gear, with you foot on the brakes to slow down the acceleration an make it easier to see what is going on.

Cheers n

Si

**nip** · 15 August 2007, 10:24

hi kev, ive the same boost gauge as u , i have a aby runnin approx 280bhp, on idel i see -20, on full boost in 2nd i see 20psi sometimes a bit over, 3rd 4th 5th 6th i see about 20 for some strange reason im seein 24psi

hope its some help to u, sound like u have a boost leak

**Big_kev** · 15 August 2007, 16:27

Let me see if i can shed a bit more light on the sequence of events.

When the car is idling the guage shows anything from 14.5 to 20 on the left hand scale. If i press the accelerator right to the floor the guage immediately jumps to zero on the gauge and then as the car starts accelerating throught the rev range the guage rises steadily to a maximum of 10 psi on the right hand side gauge when it is screaming its nuts off at around 6000rpm. As soom as i lift my foot off the accelerator it returns immediately to 20 on the left gauge.

Let me know if i have to do any further testing shed any more light.

thanks for the input so far.

Kevin

**newsh** · 15 August 2007, 17:09

I thought thats what you were doing, you have to actually drive it to see what kind of boost its making, it just doesn't work parked up, best get someone else to take the pics though , eh?

**newsh** · 15 August 2007, 17:11

I really think its not a good idea to rev it to 6k in neutral either...

**HPmuirt** · 15 August 2007, 17:33

Ahh, as Newsh said, we thought you were doing most of this in neutral but needed to check before jumping in with both feet. Most turbo cars will not produce any boost when revving the engine in neutral (unless they have a turbo destroying anti-lag system like rally cars). At idle you will see a vacuum but when revving you will see a neutral reading.

The ECU will only allow the wastegate to close and start building boost when the engine is under load, therefore you must drive the car to see what is happening. You should therefore use a high gear such as 4th on a 3B car and preferably on a long hill. Start with the revs at around 2000rpm and then boot it - you must put your foot down hard and fast as the ECU will not give full boost if you accelerate slowly , even if you end up at WOT (well on an ABY anyway).

You should see peak boost between 2500 and 4000rpm, depending on your mapping. When and what the peak boost is, how long it stays before dropping back and what it drops back to, should tell the mapping specialists on here which map you are running.

A stock 3B should show a max boost of around 12PSI (16PSI for an ABY). A chipped one might show up to 19PSI (22PSI for an ABY). Don't know how Nip is seeing 24PSI as this is 1.65BAR which I believe is beyond the capabilities of the standard MAP sensor in the ECU, unless changed for an RS2 unit.

Cheers n

Si

**Big_kev** · 15 August 2007, 20:42

Update

Guys

Sorry for the confusion. These photos and commentary were taken while the car was being driven.

Baffling Boost

Baffling Boost

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