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Discussion Starter · #1 ·
(numbers rounded for sake of simplification)

After reading numerous reviews stating the Quad runs 35 psi, this didn't sound right to me with the power output and lead me to research about the turbos and boost.

I've since learnt about psia and psig, big difference i.e. one bar (Google if you're not aware).

So really, the Quad runs 20 psi (psig) which makes sense.

I only say this because when cars are reviewed and psi is mentioned, it has always actually been psig in my reading experience, but with the Quad, they've still said psi, but it's actually been psia, a good 14.7 psi difference!

If you didn't know better like me, well hopefully now you do. Sneaky buggers, reminds me of Ferrari tactics.
 

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20 psi is a realistic number. 35 psi, only for those kids trying to brag about a big peak HP number and never consider things like engines grenading.

I'd be interested to hear what the performance tuners have to say.
 

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2018 Q4 with Fiamenghi Ti exhaust, Race Mod, and Tecnico wheels.
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(numbers rounded for sake of simplification)

After reading numerous reviews stating the Quad runs 35 psi, this didn't sound right to me with the power output and lead me to research about the turbos and boost.

I've since learnt about psia and psig, big difference i.e. one bar (Google if you're not aware).

So really, the Quad runs 20 psi (psig) which makes sense.

I only say this because when cars are reviewed and psi is mentioned, it has always actually been psig in my reading experience, but with the Quad, they've still said psi, but it's actually been psia, a good 14.7 psi difference!

If you didn't know better like me, well hopefully now you do. Sneaky buggers, reminds me of Ferrari tactics.
Maybe it is sneaky, maybe it is the truth. Of particular interest is if the waste gate opens based on psia or psig. Traditional waste gates open based on psig, allowing the engine to produce less power at higher elevations. If the waste gate opens based on psia, then you should get consistent max power over a wide range of altitudes with only turbo lag time increasing and maybe lower RPM torque decreasing with altitude. A mechanical boost gauge installed on a QV or 2.0T would let us all know.

Also, did you confirm that the boost is 35psia or is this conjecture? Some very high performance engines run boost as high as 60psig (formula 1 cars, high performance piston engine airplanes).

If psia is being used for the waste gate, obviously one needs to make speed runs at higher altitude (Bonneville?) since aerodynamic resistance decreases markedly with altitude.

Cooling also decreases with altitude, both for the engine and the electronics. Most electronics have a maximum altitude rating and with all the electronics built into Giulia I have to wonder if the potential issues were considered. Typical max ratings for electronics are in the 8000 to 11000 foot range (the transfer switch in my house is rated 6000 feet, even though I have it installed at 7500 feet). I regularly drive up to 9600 feet (about 4.4psi lower than sea level) and Pike's Peak in Colorado (the highest paved road in the USA) is over 14000 feet (about 5.8psi lower than sea level).
 

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Discussion Starter · #6 ·
Well, there is a difference between 35psi and 35 psi of boost. These terms cause a lot of confusion.

The car starts with about 14.7, which is standard atmospheric pressure. Add in 20 pounds of boost and you have just about 35psi absolute, of which 20 psi is boost.

Greg
Correct.


In the pub, I'm quite happy stating my Ferrari engine runs at 35psi boost.

You also need to consider mountains.
Your Ferrari engine runs at 35 psia, not 35 psi boost, as boost is psig. So it's actually 20 psi boost.

The point of this thread is about reading car reviews, you might read a review that says a car is running 12 psi, meaning it runs 12 psi boost, sure no problem, that's psig.

But with the Quad reviews, they've been saying 35 psi without mentioning that's actually psia! They should say 20 psi (i.e. boost, for consistency).

All the other car reviews could add another 14.7 psi to their numbers and sound more impressive if psia was the standard in what 'psi' means, but in my reading experience, psi has always actually meant psig because they're talking about boost.
 

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I plan on doing a boost tap to measure the manifold pressure sometime in the next couple weeks.

Any aftermarket boost gauges being released anytime soon?
 

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Congratulations on being the most boring (and IMHO) non relevant thread so far. I know...some of you gear heads need to dissect the stats that mean little or nothing to most of us. That said I respect your engineering knowledge...but it's a bit like eating the best steak you ever had and arguing about the type of plate it's served on.

Just drive boyoes!
 

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Congratulations on being the most boring (and IMHO) non relevant thread so far. I know...some of you gear heads need to dissect the stats that mean little or nothing to most of us. That said I respect your engineering knowledge...but it's a bit like eating the best steak you ever had and arguing about the type of plate it's served on.

Just drive boyoes!
If it's that non-interesting to you, then why are you jumping into the conversation???



About that plate, I think bone china is much better than plaster of Paris. But the real art is in how hot the kiln is when it's fired.
 

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Correct.




Your Ferrari engine runs at 35 psia, not 35 psi boost, as boost is psig. So it's actually 20 psi boost.

The point of this thread is about reading car reviews, you might read a review that says a car is running 12 psi, meaning it runs 12 psi boost, sure no problem, that's psig.

But with the Quad reviews, they've been saying 35 psi without mentioning that's actually psia! They should say 20 psi (i.e. boost, for consistency).

All the other car reviews could add another 14.7 psi to their numbers and sound more impressive if psia was the standard in what 'psi' means, but in my reading experience, psi has always actually meant psig because they're talking about boost.
No, in the pub my 510bhp Ferrari engine most definitely runs at 35 psi boost. It also weighs 1524KG because everything is made of carbon fibre. How else would it get such an amazing Nurunburg time?
 

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Discussion Starter · #13 ·
LOL Cassino. Yes, many things exist as truths while at the pub, not always outside though.

Pub lyfe hommie.
 

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Congratulations on being the most boring (and IMHO) non relevant thread so far. I know...some of you gear heads need to dissect the stats that mean little or nothing to most of us. That said I respect your engineering knowledge...but it's a bit like eating the best steak you ever had and arguing about the type of plate it's served on.


Just drive boyoes!
If it's that non-interesting to you, then why are you jumping into the conversation???



About that plate, I think bone china is much better than plaster of Paris. But the real art is in how hot the kiln is when it's fired.
Fair enough. One too many after dinner drinks and I spouted off unreasonably. Enjoy the conversation
 

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Discussion Starter · #16 ·
This conversation seems pretty much wrapped up now anyway, I hope somebody learnt something :|
 

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Speaking of boost (and a way to keep this thread active), I have a question:

Do we have whisper waste-gates? I never hear any blow-offs.

Steve
 

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Speaking of boost (and a way to keep this thread active), I have a question:

Do we have whisper waste-gates? I never hear any blow-offs.

Steve
I've never heard a peep out of my Ti. My 4C farts and burps like school boy.
 

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Speaking of boost (and a way to keep this thread active), I have a question:

Do we have whisper waste-gates? I never hear any blow-offs.

Steve
Both the 2.9L and the 2.0L have recirculating systems, which excess boost pressures & boost pressures when the waste-gate closes, empty out into the factory sealed induction system. Open this up and a symphony occurs. (If that is your cup of tea, its mine)
 

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Would definitely prefer to hear them blow-off, as long as it didn't negatively impact power. Thanks for the explanation. I was wondering why I couldn't hear them.

Do any options exist to address this?

Steve
 
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