996 TT Boost Gauge

[Stewpot67]

Clint Hightower on Facebook

 

[antnicuk]

Thanks.
I'm in Essex near Epping.
I'll have a look at the video.

 

[Jimbob2911]

I've just been through this whole process on my 996 with markski. Agreed with everyone he is a top bloke, and knows his stuff. I like his manner to the point and no messing around. Do it his way as he knows.
I got the tune ready but first carried out leak checks. I bought his bottom hose connection kit. Really easy to use and simple to get to.
I had leaks from diverter valves, throttle body seal and y pipe. All easily fix's am I'm no mechanic, but thankfully YouTube delivered.
It now has around 525 according to markski with what I have done and it hits 1.3 occasionally , dropping back to 1.2. I did think I showed 1.5 first day and markski said that is wrong and dangerous. Think it was my eyes as onl6 hit 1.3 now.
Transformed the car ..

 

[youngsyr]

I've just been through this whole process on my 996 with markski. Agreed with everyone he is a top bloke, and knows his stuff. I like his manner to the point and no messing around. Do it his way as he knows.
I got the tune ready but first carried out leak checks. I bought his bottom hose connection kit. Really easy to use and simple to get to.
I had leaks from diverter valves, throttle body seal and y pipe. All easily fix's am I'm no mechanic, but thankfully YouTube delivered.
It now has around 525 according to markski with what I have done and it hits 1.3 occasionally , dropping back to 1.2. I did think I showed 1.5 first day and markski said that is wrong and dangerous. Think it was my eyes as onl6 hit 1.3 now.
Transformed the car ..

Excellent news. :thumb:

I think a lot of people misunderstand how boost and boost control work in cars. They expect a hard limit of say, 1.3 bar, never to be breached and held to the red line.

Actually what happens is that there's a slight delay between the car sensing it has reached the programmed boost limit and then being able to stop the boost increasing.

This is why you typically see cars initially boost to say 1.3 bar and then drop slightly (to around 1.1 bar on our cars) and hold that level for as long as the turbos are capable of providing enough air and the engine is capable of dealing with the power. 1.1 bar is the determined safe held boost target level, the spike to 1.3 bar when coming on boost is just an acceptable consequence of the delay in the boost control system.

However, air pressure varies with temperature, weather and altitude, so you can see small variances around those numbers. Humidity and even the gear the car is in can also play a part in how quickly boost thresholds are reached and by how far the car breaches its target boost level.

In short, it wouldn't surprise me if a car mapped to 1.3 bar peak / 1.1 bar held saw momentary spikes to 1.5 bar once every now and again when coming on boost.

It's when the boost curve is erratic and spiking to say 1.8 bar or not reaching 1.0 bar that indicates you have a problem.

 

[youngsyr]

This is a good example of what a car's boost control is trying to do and how it does it:

The blue line is essentially torque.

Thin dotted green line is target boost.

Thick green line is actual boost.

You can see the car is programmed to max out the boost at 24 psi (1.65 bar) by 3,000 rpm, then gradually let it fall to 20 psi (1.45 bar) by 7,000 rpm.

However, because the car has quite a big single turbo, it cannot spool up fast enough to reach the target at 3,000 rpm, but does is allowed to get to the boost target as quickly as possible, with boost control kicking in at around 3,600 rpm and 22 psi, which is still below the target boost.

Note at this point that the turbo isn't just increasing the amount of boost provided, it's increasing the acceleration in the amount of boost provided, i.e. it's producing more and more and more boost, more quickly.

The engine is producing a lot of energy in the exhaust in a feedback loop with the turbo:

more energy out of engine -> more energy into turbo -> more boost into engine -> more energy out of engine -> repeat

So the car overshoots the boost target briefly before being brought back to the target by the car's boost control system.

It's worth noting that the boost control on this car isn't that great - you'd hope to see a much more steady boost line after peak boost.

Also, the graph shows you how the car ultimately controls the boost - it opens up the wastegate on the turbo to bypass exhaust around the turbo. WGDC is Waste Gate Duty Cycle. Basically how much the wastegate is open.

 

[Parsley]

Do you guys use wideband lambda gear at all??

Lots of talk of boost limits etc but nobody really talks about afr!!

I see a lot of people getting maps/actuators/turbos changed but seems very little talk of afr. Perhaps you have wideband gear in the car? Genuinely interested. It only takes an injector problem on one cylinder and and pop on a car running lots of boost.

 

[youngsyr]

Do you guys use wideband lambda gear at all??

Lots of talk of boost limits etc but nobody really talks about afr!!

I see a lot of people getting maps/actuators/turbos changed but seems very little talk of afr. Perhaps you have wideband gear in the car? Genuinely interested. It only takes an injector problem on one cylinder and and pop on a car running lots of boost.

I believe the cars have a wideband lambda fitted pre-cat in each side of the exhaust for the car's normal fueling system and this is just datalogged by Durametric etc during tuning.

You're right though - the above is just referencing boost, which is only part of the tune. Fueling is the another part (and is a whole other story!).

Knock is also monitored by the car as standard and by the tuner (if he's competent!).

 

[Parsley]

Do you guys use wideband lambda gear at all??

Lots of talk of boost limits etc but nobody really talks about afr!!

I see a lot of people getting maps/actuators/turbos changed but seems very little talk of afr. Perhaps you have wideband gear in the car? Genuinely interested. It only takes an injector problem on one cylinder and and pop on a car running lots of boost.

I believe the cars have a wideband lambda fitted pre-cat in each side of the exhaust for the car's normal fueling system and this is just datalogged by Durametric etc during tuning.

You're right though - the above is just referencing boost, which is only part of the tune. Fueling is the another part (and is a whole other story!).

Knock is also monitored by the car as standard and by the tuner (if he's competent!).

Ah ok cool just wondering. Knock is easily controlled by the cars ECU as you say. I would imagine the mapper uses det cans anyway when mapping. I was just curious as I think some people don't realise the dangers of something running lean. I've seen many molten pistons over the years lol. (Not on Porsches I might add)

 

[youngsyr]

Do you guys use wideband lambda gear at all??

Lots of talk of boost limits etc but nobody really talks about afr!!

I see a lot of people getting maps/actuators/turbos changed but seems very little talk of afr. Perhaps you have wideband gear in the car? Genuinely interested. It only takes an injector problem on one cylinder and and pop on a car running lots of boost.

I believe the cars have a wideband lambda fitted pre-cat in each side of the exhaust for the car's normal fueling system and this is just datalogged by Durametric etc during tuning.

You're right though - the above is just referencing boost, which is only part of the tune. Fueling is the another part (and is a whole other story!).

Knock is also monitored by the car as standard and by the tuner (if he's competent!).

Ah ok cool just wondering. Knock is easily controlled by the cars ECU as you say. I would imagine the mapper uses det cans anyway when mapping. I was just curious as I think some people don't realise the dangers of something running lean. I've seen many molten pistons over the years lol. (Not on Porsches I might add)

In my experience of tuners over the past 15 years, det cans are old tech and mappers just log the car's knock sensors which are more sensitive and informative anyway - you have a record of all the parameters of precisely when the knock occurred.

 

[Parsley]

Do you guys use wideband lambda gear at all??

Lots of talk of boost limits etc but nobody really talks about afr!!

I see a lot of people getting maps/actuators/turbos changed but seems very little talk of afr. Perhaps you have wideband gear in the car? Genuinely interested. It only takes an injector problem on one cylinder and and pop on a car running lots of boost.

I believe the cars have a wideband lambda fitted pre-cat in each side of the exhaust for the car's normal fueling system and this is just datalogged by Durametric etc during tuning.

You're right though - the above is just referencing boost, which is only part of the tune. Fueling is the another part (and is a whole other story!).

Knock is also monitored by the car as standard and by the tuner (if he's competent!).

Ah ok cool just wondering. Knock is easily controlled by the cars ECU as you say. I would imagine the mapper uses det cans anyway when mapping. I was just curious as I think some people don't realise the dangers of something running lean. I've seen many molten pistons over the years lol. (Not on Porsches I might add)

In my experience of tuners over the past 15 years, det cans are old tech and mappers just log the car's knock sensors which are more sensitive and informative anyway - you have a record of all the parameters of precisely when the knock occurred.

Old tech :lol: describes a lot of members on the forum. Including me. :thumb: