Normal boost / vacuum levels

cjep · Post by **cjep** » 30 Jun 2013, 06:56

Hi

I have a 98 C70 HPT, that I have just completed stage 0 on (thanks heaps everyone I could not have done it without this site)

I have a quality boost gauge, but I am not getting very hight boost readings. What is normal?

I am getting:
idle: 17-18mmHg
decelleration - up to 22mmHg
WOT 1st and 2nd - up to about 6psi
WOT 3rd and above - up to about 8 psi *

*This reading may not be 100% accurate. I have an auto, and to get these readings I have to be going pretty fast, and the police are pretty unforgiving to speeders over here.

I have replaced all my hoses, and have double checked for leaks, but there are so many hoses, it feels like you can never be 100%

I suspect these readings are on the low side. If so, what should I be checking? Could it be the TCV? The wastegate actuator rod out of adjustment? Something else?

I have ready heaps here about increasing boost levels, but I want to make sure it is all good at stock settings first.

Thanks in advance!

Post by **Pauloil** » 30 Jun 2013, 07:01

odd, but your vacuum levels are very sim. to mine as reported by the torquePRO app. I have. And yes, when I push on the gas, it goes down. I thought it was good to know baseline number in case I ever get a VACUUM leak, then I will know the baseline number. HOW IS your car running?

cjep · Post by **cjep** » 30 Jun 2013, 16:02

The car is running quite well at low RPM, i.e. every day driving, but just does not have the upper end power I expected.

I just noticed that my numbers may be a bit misleading, and should read:
idle (in gear): 16-18mmHg
idle (in park): around 19 mmHg

I drove the car to work this morning, and my gauge goes hardly/never into pressure. In traffic, it goes from around 18mmHg to about 10mmHg (on light acceleration), and when I accelerate moderately it goes up to 0 quite quickly. But for it to go into positive boost, I need to give it a lot more, basically WOT, where it takes some time to get up to the max levels for that gear

Is this normal behaviour? I am quite new to my car, so don't really know what to expect.

Post by **JRL** » 30 Jun 2013, 16:30

Numbers are close
I suggest you tighten the wastegate rod about one turn

cjep · Post by **cjep** » 02 Jul 2013, 04:52

I have tightened my wastegate rod two turns (first one, didn't notice any difference, and then another)

I have made a video of my boost levels. This is a 0-100km/h WOT run:

This can't be right can it?

Post by **JRL** » 02 Jul 2013, 05:48

Ehhhhh, close
You failed to mention the miles on the car
I had an exceptionally fast 99 T5M (stock ECU) but is was a manual. It ran at about 6-7 in first gear and 10 lbs in all the other gears (with spikes to 11+ in 3rd), but that car was completely rebuilt, every vacuum hose was new, breather was new, and so forth.
It could be as simple as your boost gauge accuracy, or where it's tapped into, etc.

cjep · Post by **cjep** » 02 Jul 2013, 06:15

Thanks again for the quick reply JRL, I really appreciate your feedback.

The car appears to be in pretty good condition. It has 150' km (just under 100' miles) on it, and I have just completed stage 0. It has a full service history from volvo initially, and from a volvo indie after that. Hasnt been modified at all.

I have replaced all vacuum hoses, except the ones after the check valve to the canister. They seem pretty good, but who knows. Maybe I can just block off that part of the system temporarily? (or permanently?)

One thing that I did when replacing the vacuum hoses, was to put a bigger vac hose between the side of the manifold to the PCV. I did this because I couldnt get a smaller vac hose to go over the nipple on the manifold/PCV and didnt want any joins. But now that I think about it, that will help leak pressure out of the manifold to the PCV which is unpressurised. Was that a bad thing to do?

Thanks again!

cjep · Post by **cjep** » 02 Jul 2013, 16:08

And I forgot to mention, the boost gauge is tapped directly into the vacuum tree.

echase76 · Post by **echase76** » 02 Jul 2013, 20:37

My '98 t5m runs 18 in hg at idle and 22 in decel. I have approximately the same numbers as JRL for boost. I run about one waste gate turn. Cheap boost gage tapped into tree.

Post by **matthew1** » 02 Jul 2013, 20:53

cjep wrote:

This can't be right can it?

It's low. Here's a good low-boost troubleshooting topic.

Please post back to this topic, not that one.