Hi my name is Nathan and I'm new to the Forum. I own a 99 S70 GLT and if I understand correctly the little I know about turbos my GLT is a low pressure turbo. Does this mean there is less turbo lag and the turbo kicks in at a lower RPM? So is there any other significant difference or Pros /Cons with having an LPT?

Nathan

 

basically, ......yes.
Low pressure turbos like the one in the volvo and the VW 1.8t are smaller units designed to boost lower in the rev range.
Since they are generally smaller than 'high-pressure' turbos they require less energy to spin the impeller... hence boost with less lag.

The LPTs tend to get a workout all the time and are generally limited in the amount of max boost you can squeeze from them if you are to mod your car.
the HPTs will give you more boost at the expense of low end grunt and throttle response. They take more time to 'spool up' and create boost.
I've had a 98 passat 1.8t (LPT), a '04 WRX (HPT), and my '98 v70xc(LPT). The volvo 'feels' like a cross between the 2 others.
the WRX was a dog until about 3k rpms then WOW...... I wish I still the had the car... The wife made me get rid of it when we had our second child :-(

The Passat didn't feel like it even had a turbo... it was a 5spd and it had practically zero lag. I've also been in the 'tiptronic' version and it sucked... not a good fit for that car, IMO.

The v70xc feels a little laggy off the line but you can hear and feel the turbo spooling up and doing its thing around 2k rpm. It's as if you can modulate speed a lot more without having the car shift gears. As opposed to a Honda Accord that is always shifting gears 'looking' for the right gear.
I love blasting up I-70 to Copper Mtn in the winter time. The turbo makes driving a lot of fun.

 

LPT is all about boost pressure. My S40 was rated at 7 psi. Yes they are smaller and not capable of produceing hugh amouts of pressure. As far as how the turbo works it is based on the EPROM (chip) as when and how much pressure to release. I have had my chip reprogrammed and now boost pressure is rated about 16 psi. They also remaped the entire engine configuration as to allow a max boost pressure at a lower rpm. If i remember my 7psi usually spooled up at about 30 kph and was very moderate all the way up. Now with the reprogram boost spools at closer to 20 km/h and is getting full pressure a hell of a lot more quickly. Not only that but now instead of the computer limiting to boost through out the spool I get more pressure at a faster rate. The timing and other things that are computer controlled have been remapped to accept this, Down side now I have to run fully synthetic oil, trans as well and use premium gas (not regular).

 

I have a 99 s70 awd, with the 13g turbo in it. LPT by the way. Stock I was running 5-7 PSI. Now with my SpeedTuning ECU upgrade I am running 12 PSI.

Yes our little LPT's spool up faster with less lag. The most boost that I would want to run on a LPT would be like 15. That is my opinion. Since I think 20 PSI or anything above 15 is out of its effciency range.