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Also worth mentioning that you can configure it to show on the top of the screen (where it shows the range by default). That way you can always see it no matter what screen you're on.
My boost shows 1 at min. all the time when in Sport +.
Also shows the boost in sport mode when downshifting but certainly throttle dependent (eg I don’t see 10+ boost when just downshifting).
The fact we hear the fans spool up as we add throttle leads me to believe they aren’t completely passive.
On the subject of boost......why isn't there at least some boost going to the engine at all times? What are the turbos doing when it reads 0 on the gauge? Are they being bypassed and not spinning or are they spinning but not adding any pressure to the intake side?....
Here's my non-expert crack at it:
No, at lower RPMs and low throttle turbochargers actually reduce the engine's power a bit due to resistance to the flow of the exhaust stream and since they aren't yet spinning fast enough to produce a gain in intake pressure. The point at which they start producing power is called the "boost threshold", something you can search for. There is no single RPM for a particular engine that this occurs, it changes due to a combination of factors (primarily throttle, RPM, and load I'd guess). The heat-induced expansion and flow rate of the exhaust gas has to be fairly high to produce boost. Just driving along at normal speeds and normal-to-light throttles won't be enough to produce much (if any) boost.
I think the only time the waste gate opens to allow some exhaust to bypass the turbos is when the intake pressure they are generating gets too high. If you opened it under normal cruising, the turbine would spin down and take longer to spin back up, increasing turbo lag.
Makes me miss my old 87 930, when that boost needle finally moved all hell would break loose.
Old-school turbo guys will want to change it to BAR instead of PSI ... just like I changed my oil pressure ; )
But unlike the old school turbo, the 3 liter 991.2 engine makes enough HP and torque for normal driving. And when the boost does climb above zero, things get fun--just like in the old days.
I also had a '87 930, which I bought from Wilbur Marshall who bought it new. It scared the crap out of him every time he drove it but he loved it so he kept it for while and he told me he would take people for a ride and would take it easy at first then he stepped on it...he loved to watch the expression of his passenger's face when boost kicked in. He also said he had more fun in the car than playing football. I did the same thing to people - what a blast that car was in the day.
Better headers and cats should spool the turbos up sooner. Probably don't raise maximum Booost without a tune, right?
Mine seems to like 4000+ rpm b4 it hits 17 psi boost, driving mostly in Sport. Id do the headers and cats, but just spent some change on ceramic tint, PPF, and X51 PowerKit. It only has 2200 miles. So ill wait a while, till I'm convinced which headers and cats are best.
I could go catless, as no annual is required where I live.
Then there are the tunes, but I'm going to wait on that too, at least a couple years into my factory warranty.
I noticed same thing which caused me to initiate this topic here. The guys above educated me on that if you put the 991 in "Sport Plus" you'll see the psi boost gauge fluctuating up/down during acceleration in the 3500ish and up range. I only have 200 miles on my T so I have been VERY careful not to exceed 4k rpms and when in "Sport" mode you won't see any psi boost other than 0, unless you really WOT the car which I'm not about to do.
We have just negotiated a deal on the Soul Performance Hi-flow cats, with or without PSE, for $1850 shipped, which is a great deal and an easy bolt-on install with no CEL. If someone is interested contact Austin at Vivid Racing and mention the Rennlist deal and me (Bob Z.) to get the deal: austin@vividracing.com
No Sport Chrono, thus no Sport + in this car. Since it's a manual I didn't really see the need, but who knows maybe I should have.
This is how I have my gauge set up.
why bother look at coolant temperature? It maxes out at 194°F and does not go higher, except if there is a problem, in which case alarm and oil temperature will alert you. Battery voltage is more important to watch than coolant temp.
On the subject of boost......why isn't there at least some boost going to the engine at all times? What are the turbos doing when it reads 0 on the gauge? Are they being bypassed and not spinning or are they spinning but not adding any pressure to the intake side?
I have had two 991.2's. One a PDK and now a manual. With both cars and daily driving I rarely see/saw the boost gauge change from 0.
Unlike the PDK that likes to shift early and keep the engine around 2,000 RPM, my manual car sees a lot of 3,000-5,000 RPM shift points, but still 0 on the boost gauge (ok maybe 1 psi). I can't imagine that at 4,000-5,000 RPM's there is not enough exhaust gas to spin the turbos and provide boost. I wonder what the strategy is?
I've come to realize that in my car: Smooth acceleration = 0 or minimal boost.....Gas pedal pushed quickly or floored = boost.
I think it's more a function of gas pedal position. I can floor mine at 2000 rpm and get boost by moving pedal to floor. So I think the revs are less important. Of course the amount of torque is based on revs.
I'm still in break-in period on my TT and haven't yet even gone to Sport +. In Sport mode, my boost gage sits at 0 psi until I get on it just a little bit.
In tight highway traffic I had to get on it once over 4000 rpm and the thing was like a rocket...hope no damage was done...ha ha
10-03-2018, 06:46 PM
