According to vagcom (vcds-lite, using Measuring block 115)
my actual boost is almost always a little higher than the specified boost. I dont believe this is a problem.

The general range of boost is from 980 mbars to 1540 mbars (14 psi to 23 psi). At idle, the specified boost is 980 mbars, and the actual is about 1000 mbars.

It takes about 1.5 seconds for actual boost to catch up to specified boost (turbo lag) under pressure, and about 5 seconds for actual boost to slow down to specified boost after engaging.

Just checking - does all of this sound about right for a stock car?

Any other measuring blocks that I should pay special attention to? (thinking about my o2 sensors and a p0420 code).

Thanks!

 

For a STOCK CAR? NO boost is around 7-9 psi!

 

Yeah there shouldnt and cant be any boost at idle, actually exactly the opposite with vac, and a stock car doesnt boost that high. Maybe the numbers arent accurate or valid unless the car is boosting. So if actual at idle is 1000, maybe make 1000 your zero (I dont think its a coincidence your idle is exactly 1000), then 540 mbar would be your max which is just above 7psi which sounds much more like it... if that makes sense to you (depending on your gear it will vary, but the max on an '01 was a little more than 7-8 psi I though, more like 8-9 or 9-10)? I would be 1000 is zero actual and if it doesnt change unless you are above about 1/2 throttle basically, it wont actually be boosting before that.

If you dont have any problems there arent really any specific blocks to look at, you can look at misfire counts and see if you are missing a little bit, not enough to throw a CEL, you can look at your fuel trim to see if its adjusting alot (which would indicate fueling or air issues), but generally that throws a CEL.

 

just get a boost guage

 

Ahhh - didnt I once hear in a physics class (or science, at least) that air pressure at sea level is 17.x psi??

Sooooo - that makes sense (now that I think about it).

So, it sounds like I'm either missing some boost - or I wasnt testing it hard enough (I was just driving around town and couldnt push it all that hard.).

 

Im not positive on this but try flooring it for at least 5 seconds in 3rd or 4th gear at 3k rpms or so and see if its any higher. I think boost varies at certain gears, and obviously at certain rpms. I do think a boost gauge might give you better readings also but give that a shot. At minimum this would be a good way to make sure you dont start to loose boost from what you already have if you dont want a boost gauge.

 

my car peeks at about 12 psi and is consistant between 10-11 psi stock

 

thanks for the input. but . . .

If I had a boost leak, wouldnt my specified boost be higher than my actual boost?
So, the fact that my actual boost is higher than the specified boost (slightly) seems to be a good sign. Correct??

By the way - if I did invest in a boost gauge - would it show me both specified and actual boost values?

Although I'm looking at the boost right now, its only because it makes sense to spot check the major systems to make sure that everything is still working properly but I don't really intend to pay attention to my boost 24/7. I check my oil level and tire pressure too - but only once a week or so (and there was a time when I thought that once a month was good enough). I really don't need/want to see those values 24/7.

Thanks for the input!

 

Overall it probably isnt the best way to measure boost.. since the actual measurement seems to start at 1000, then whos to say your specified isnt on a different scale. But if it were on the same scale, you would be right it probably is boosting enough.
A real boost gauge only shows actual boost, people dont really care about specified, basically you want it to get to a certain point when you floor it, and you want a certain amount of vac at idle (both would show vacuum line issues, etc.), thats what people mainly use them for. Another small thing, is people use them to make sure they dont boost when the engine is really cold.
You can buy a boost gauge and use it only temporarily if you want, that would save you the expense of the gauge holder, I personally like having it, and you dont have to look at it all the time, but it sounds like you dont want it there all the time. IMO, I wouldnt bother getting one if you dont want to have it all the time, and continue to use your VAG to make sure you get the same amount of boost you do now further down the road.

 

Thanks Dallas and everyone.

I think you've nailed it on several points.

1. vagcom is measuring in mbars instead of psi.
2. air pressure at sea level is about 17 psi or 1000 mbars
3. so my actual boost is in the 8-9 psi range - as far as i've tested it.
4. thanks for the reminder to not boost when the engine is cold. This is my first turbo and those reminders are helpful.
5. I like the interior of the car and don't want to install extra gauges (plus lazy - don't want to do the work and spend money unless needed. Now if I talk myself into chipping then a boost gauge might be necessary).

thanks again!!