996 TT Boost Gauge

[antnicuk]

Evening all

Ive recently bought my first 996 turbo. It is an X50 manual with a stage one map. It is supposed to be running 550 bhp. The car also has turbosmart actuators which seem very stiff and seem to have quite a lot of pre load on them.

I was wondering what sort boost i should see on the digital boost gauge on the dash.

if i plant the throttle in 4th at about 3000 rpm the boost hits 1.2 briefly and seems to settle at 1.1 bar. A couple of times 1.3 flashed up then 1.2 and settles again 1.1. If I floor it in 6th ive seen it flick to 1.5 before dropping almost instantly to 1.2 then 1.1. but due to the speeds involved and the boost levels being higher than i'm comfortable seeing i let off quickly. The high boost number just flick up, they dont maintain it and they only appear when i stamp on the throttle, if build boost a little slower before flooring it the boost doesnt spike.

Im thinking that it might be due to the springs in the actuators being quite strong and too much preload meaning they take a split second longer to crack open?

i did buy a new N75 valve but not fitted it yet, i assume if that was faulty the boost wouldnt hold firm after the initial spike and would possibly be lower?

any advice or experience appreciated...

 

[Mac996t]

When I got my car the boost spiked a bit and a new n75 valve fixed it. Mine is also remapped to 1 bar, before it sometimes got to 1.3 bar and after it was controlled really well at 1.0 bar. My car does have standard actuators though. You have to be careful that aftermarket actuators don't need too much pressure to crack them open.
The std actuators only take around 0.4bar to crack and are full open by 0.6 bar. This means the n75 valve can control the boost well. If boost is above what the computer wants the n75 lets more of that boost pressure get to the actuator which open to lower the boost.

If you have actuators that are set to crack very near the max boost pressure then the n75 has a much lower range of control which can lead to spiking

Mac

 

[Jess911]

Perhaps you need a boost controller. 1.5 bar is quite a lot. The Turbo's could probably take it though

 

[Stewpot67]

I have turbosmart n75 set to crack at 1bar with a Markski map holding 1.2 bar after data logging (3rd gear 6k Rev) 5 bar fuel regulator

 

[youngsyr]

Evening all

Ive recently bought my first 996 turbo. It is an X50 manual with a stage one map. It is supposed to be running 550 bhp. The car also has turbosmart actuators which seem very stiff and seem to have quite a lot of pre load on them.

I was wondering what sort boost i should see on the digital boost gauge on the dash.

if i plant the throttle in 4th at about 3000 rpm the boost hits 1.2 briefly and seems to settle at 1.1 bar. A couple of times 1.3 flashed up then 1.2 and settles again 1.1. If I floor it in 6th ive seen it flick to 1.5 before dropping almost instantly to 1.2 then 1.1. but due to the speeds involved and the boost levels being higher than i'm comfortable seeing i let off quickly. The high boost number just flick up, they dont maintain it and they only appear when i stamp on the throttle, if build boost a little slower before flooring it the boost doesnt spike.

Im thinking that it might be due to the springs in the actuators being quite strong and too much preload meaning they take a split second longer to crack open?

i did buy a new N75 valve but not fitted it yet, i assume if that was faulty the boost wouldnt hold firm after the initial spike and would possibly be lower?

any advice or experience appreciated...

Max boost pressures achieved will fluctuate on conditions, even something as simple as air temperature can add or subtract 0.1 bar or so. Cars can boost to different levels in different gears too.

It's also typical for the boost pressure to spike momentarily as the turbos spool up and hit the (mapped) boost limit, so spiking to 1.3 and then holding 1.1 bar would be normal for a mapped car, which sounds like what your car is doing, give or take?

1.5 bar boost does seem high though, for 550 bhp I'd be expecting more like 1.3 bar peak, but if you only see it momentarily once in a blue moon, I wouldn't be too concerned about it.

For you peace of mind, I'd get in touch with the tuner who mapped it and either take the car in for a check up or talk them through its behaviour and make sure it's functioning properly.

I also wouldn't compare my car to anyone else's on here - unless your car has the exact same parts fitted and is mapped by the same tuner to the same performance level, the differences can be significant enough to make a comparison meaningless.

 

[youngsyr]

I have turbosmart n75 set to crack at 1bar with a Markski map holding 1.2 bar after data logging (3rd gear 6k Rev) 5 bar fuel regulator

Interesting - did you use his flashing unit? If so, how did you find it?

 

[Stewpot67]

I have turbosmart n75 set to crack at 1bar with a Markski map holding 1.2 bar after data logging (3rd gear 6k Rev) 5 bar fuel regulator

Interesting - did you use his flashing unit? If so, how did you find it?

Yes very simple, I have 5 maps stored on it due to small changes made all runs were logged and emailed to him. Excellent customer service always keen to get the best out of the car

 

[youngsyr]

I have turbosmart n75 set to crack at 1bar with a Markski map holding 1.2 bar after data logging (3rd gear 6k Rev) 5 bar fuel regulator

Interesting - did you use his flashing unit? If so, how did you find it?

Yes very simple, I have 5 maps stored on it due to small changes made all runs were logged and emailed to him. Excellent customer service always keen to get the best out of the car

Excellent, would you consider renting the flashing unit out to a fellow member? :thumb:

I purchased a map from Markski during his Black Friday sale, but need to check for boost leaks before going through the mapping process. I'm hoping to only map the car once (or at least go through the tuning process once), so splashing out for a new flashing unit doesn't seem to make sense.

Would also be interested to hear about the hardware/software that you used to log your runs - did you use a Durametric or another data logger? :thumb:

 

[Stewpot67]

Hi

Unfortunately you can't use mine as they are linked to the vin number, my brother has been using Markski also and he purchased one as we were worried by confusing maps ie stick the wrong one in!! I agree leaks are a major issue you need to resolve it cost me £1.2k as I found a cracked turbo amongst other things.

I have used my brothers Durametric and given upgrades I have done money well spent..

Stewart

 

[DJones]

You really need to start with a pressure test to ensure it's air tight or you will be chasing shadows to some degree.

You then want to check the cracking pressure of the wastegates with a mittyvac. The pump gauge doesn't want to show over 14psi when they crack.

You can also try running it with the N75 disconnected, hence the gauge shows spring pressure only.

You you then want to data log it so you can see precisely what's happening with boost and importantly see where your fuelling is at.

The boost you describe won't damage the car but any fuelling issues could.

It all sounds much more complicated to explain than it is to do and what you've described doesn't sound to far amiss.

Unfortunately a side effect of increasing the boost threshold is a slight spike around 4K, you can improve it with the right springs and preload but you cam make it significantly worse with even a small amount of excess preload.

Hope it helps

Darren.

 

[diverzeusy]

Well said Darren 👍
I'm in the process of leak hunting, I have found the #16 check valve passing air, so as I don't fancy returning to boost leaks once the engine is back in (it's so easy whilst out) I'm currently awaiting a delivery of all the valves, Venturi, fuel vapour valve etc. I'm not saying that these are all bad, I just want a 100%reliable car, knowing that these items are new and all boost/vac pipes zip tied, I may just be able to sleep 🙄😀👍
As for Markski he certainly knows his stuff, a little blunt but to the point and gets the job done 👍

 

[Stewpot67]

Well said Darren..

You really need to start with a pressure test to ensure it's air tight or you will be chasing shadows to some degree.

You then want to check the cracking pressure of the wastegates with a mittyvac. The pump gauge doesn't want to show over 14psi when they crack.

You can also try running it with the N75 disconnected, hence the gauge shows spring pressure only.

You you then want to data log it so you can see precisely what's happening with boost and importantly see where your fuelling is at.

The boost you describe won't damage the car but any fuelling issues could.

It all sounds much more complicated to explain than it is to do and what you've described doesn't sound to far amiss.

Unfortunately a side effect of increasing the boost threshold is a slight spike around 4K, you can improve it with the right springs and preload but you cam make it significantly worse with even a small amount of excess preload.

Hope it helps

Darren.

 

[youngsyr]

Well said Darren 👍
I'm in the process of leak hunting, I have found the #16 check valve passing air, so as I don't fancy returning to boost leaks once the engine is back in (it's so easy whilst out) I'm currently awaiting a delivery of all the valves, Venturi, fuel vapour valve etc. I'm not saying that these are all bad, I just want a 100%reliable car, knowing that these items are new and all boost/vac pipes zip tied, I may just be able to sleep 🙄😀👍
As for Markski he certainly knows his stuff, a little blunt but to the point and gets the job done 👍

Are you going to get the coolant pipes pinned/welded while the engine is out?

 

[antnicuk]

Thanks all. Really helpful and also reassuring. I'm just in the process of refreshing the suspension. Once done, I'll check the actuators and that the wastegates are opening freely. I'll also pressure test the lines to the N75 valve and the cracking pressure for the actuators.

Are there any write ups or videos on how to check for leaks? Can it be done effectively with the engine in. I've got a mittyvac but do I need a smoke machine to do it properly?
Thanks again

 

[youngsyr]

Thanks all. Really helpful and also reassuring. I'm just in the process of refreshing the suspension. Once done, I'll check the actuators and that the wastegates are opening freely. I'll also pressure test the lines to the N75 valve and the cracking pressure for the actuators.

Are there any write ups or videos on how to check for leaks? Can it be done effectively with the engine in. I've got a mittyvac but do I need a smoke machine to do it properly?
Thanks again

This shows it in great detail:

https://www.youtube.com/watch?v=Qf2FIBX1L98&ab_channel=ClintHightower

No need for a smoke test, in fact a smoke test won't show up some of the internal leaks (pressure leaking past check valves when it shouldn't).

This is also a good forum for 996 turbo owners:

https://www.facebook.com/groups/51112745387

Whereabouts are you based? I'm about to undertake a boost leak test on my 996T once the weather improves slightly. :thumb: