L67 20psi pulley help

[Immortality]

Yea exactly, but it's not a useless measurement.

I've been studying heads and engine live flow for a number of years.
It's probably the hardest part of a car to wrap your head around.

Don't take my word for it, take Gale Banks word for it.

 

[losh1971]

13 pounds is oodles through an L67. Your efficiency would fall on its arse much beyond that if it hasn't already. The M90 is not only small it's roots style, I wouldn't expect anything ground breaking. If you can get it to push 20 pounds and drive I'll eat the engine with BBQ sauce

This is what I was thinking, just wasn't going to say anything.

 

[Immortality]

If you want really good advice for a L67 talk to Bazspec, they'll be able to tell you what it should make roughly.

 

[shane_3800]

This is a perfect example of engine flow/restriction vs boost pressure vs power production.
High flow under the blower equals more power.

Plus the blower in this test wouldn't be getting hot so you would get an efficiency boost.

(Stock)
Blowers are best spun at 7psi or lower.

 

[Immortality]

Just the act of creating boost (compressing air) creates heat. All blowers/turbos create heat.

The M90 is way to small for a LS motor, it is marginal on the 3800, especially the older 3rd gen M90.

7psi is meaningless by itself. On the L67 the stock blower has a 3.8" pulley and creates 6lbs of boost, that same pulley on a LS motor would make less boost.

But we're getting away from purpose of this thread which is the supposed missing boost on a L67.

 

[shane_3800]

Just the act of creating boost (compressing air) creates heat. All blowers/turbos create heat.

The M90 is way to small for a LS motor, it is marginal on the 3800, especially the older 3rd gen M90.

7psi is meaningless by itself. On the L67 the stock blower has a 3.8" pulley and creates 6lbs of boost, that same pulley on a LS motor would make less boost.

But we're getting away from purpose of this thread which is the supposed missing boost on a L67.

Yea so if you make 0psi there's no compression heat, frictional yes.
Then the more and more you compress the higher the curve spikes on heat production, it's not linear.
So PSI makes a huge difference to heat, which is likely why the efficiency drops off after about 7-10psi on a M90.

 

[shane_3800]

Also before intake valve pressure aka boost tells you power production somewhat.
So N/A you have 0psi or 1 bar so 14.5psi over true 0, aka atmospheric pressure.
If you increase that by 2x to 14.5psi or 29psi over 0, you roughly will double your N/A power.

 

[Immortality]

Yes but that assumes 100% efficiency and in the real world it doesn't quite work like that.

But we are heading off topic here.

 

[shane_3800]

I would like to see the boost curve.
You know that useless information.
At what RPM is it making 13psi?
Because what you should see is it start off much higher at low RPM, then as the engines efficiency improves and the blowers starts to drop off due to heat, you should see the boost curve dropping.

But regardless of boost, the blower can only make 500hp as seen in the video posted.
That was 500hp at 4-5psi, if you have a smaller engine you will have more boost for that power but you won't hit that because the heat screws up the efficiency.
An intercooler can't help with blower efficiency because you're not cooling the blower.

These M90's from memory have an efficiency curve that peaks around 7-10psi, pushing past that and you're just wasting power from the engine into heating up air to cool it down again.

What is my recommendation after all this, port the heads and add a cam shaft to increase engine efficiency and decrease boost. Or increase pully size and if it still makes 13psi your power will increase.

 

[Ginger Beer]

I would be curious if the IAT after the blower and cooler

I'm not a mechanics or tuners ar5ehole, but, from my years of playing with boost on track and street cars...

PD blown: knowing the PSI is irrelevant, what you need to know is the RPM of the blower to ensure you are not over spinning it, and IAT post cooler which is based of how hard you spin the blower and how efficient your intake charge cooling system is

PD pulleys are set and forget, you base it of how strong your engine is built is for power, and start with a slightly larger than desired pulley to see how much power you make, and work your way down monitoring IAT and ensuring blower RPM efficiency if you want more power

A PD spun too hard will just make heat robbing power, a PD running in efficiency range RPM making only 10 psi of charge pressure can make the same power and have safer combustion than the same set up running 20 psi in a over spun blower running superheated air

There's calculations and specs used to ensure your blower is running in its efficient RPM range, never over spun a PD and expect it to work efficiently or safely

Turbo: On a turbo car a boost gauge is a nice to have if you lose a reference line on a wastegate, or cook one closed and over boost, but, do you need a boost gauge if you use a electronic boost controller, nope, as you can just add or remove targets there, then simply "page up for power", if it over boosts it typically flashes red to let you know about issues, well, every electronic boost controller I have used has over boost warnings

Can you easily see the little numbers on a electronic boost controller when you're giving the car the beans, I cannot, but I have noticed it flashing

Well, that's my experience anyways, take what you will from that