L67 20psi pulley help

[CookedVy]

Hey guys, I’ve just recently put a l67 In my vy Ute. It’s got a 20psi pulley with 5% overdrive and a2a intercooler kit. Had it on the dyno a couple times to get it running nicely but can’t seem to get it to push more then 13psi. Done smoke test throughout the whole system which it passed with no leaks. I do have slight belt slip but nothing serious, at least not enough to loose 9psi somewhere. I’ve had all the gaskets from the vally upwards and still same issue. It’s got a yella terra snout and have been told the charger was ported to suit it. Any suggestions on why I’m missing 9psi somewhere

 

[Immortality]

You are not loosing 9 psi.

I don't know who started the naming convention for M90 pulley sizes but using boost ratings is simply wrong as (I believe) it is based on calculated boost using a M90 on a completely stock motor and it's simply not possible to use a pulley that small on a stock motor.

Using the 20psi pulley or 2.55" pulley as it should be known means you are seriously over spinning the little M90 and it's a fair way out of it's efficiency range which means it produces a LOT of hot air. Hot air takes up a lot of volume, when you run that hot air through your A2A system and bring the temperature way down that same amount of air now takes up a lot less volume. When you reduce the volume you see that as a drop in boost but what you have gained is a lot more density and that is what matters. Then add in some pumping losses from all that pipe work and your heat exchanger and it's probably about right.

Your tuner should be able to explain this type of stuff.

The only place you are possibly going to loose boost is via the boost bypass valve inside the blower if it doesn't shut fully.

 

[Immortality]

To quote some yank who might know a thing about boost, "the boost gauge is dead" Gale Banks, and he is correct, boost is simply a measure of restriction but does not take into account the temperature of that air charge and temperature has a great effect on boost.

Have a look on youtube, he has lots of video's about boost and density, most of it these days is in relation to diesel engines but Gale Banks is a old Petrol head from way back and a true guru of adding boost to almost anything.

There is a reason his company builds a **** load of diesel engines for the US military.

 

[CookedVy]

To quote some yank who might know a thing about boost, "the boost gauge is dead" Gale Banks, and he is correct, boost is simply a measure of restriction but does not take into account the temperature of that air charge and temperature has a great effect on boost.

Have a look on youtube, he has lots of video's about boost and density, most of it these days is in relation to diesel engines but Gale Banks is a old Petrol head from way back and a true guru of adding boost to almost anything.

There is a reason his company builds a **** load of diesel engines for the US military.

Yeah right, also forgot to mention it has 20thou pistons 82 degree thermostat, ported heads and charger. I know I won’t make the full 22psi but 13 seems a little low. I was told I would only probably make 16-18psi so 3-5psi is missing somewhere. I’ll check the boost bypass and see if it’s functioning properly and see how that goes

 

[CookedVy]

To quote some yank who might know a thing about boost, "the boost gauge is dead" Gale Banks, and he is correct, boost is simply a measure of restriction but does not take into account the temperature of that air charge and temperature has a great effect on boost.

Have a look on youtube, he has lots of video's about boost and density, most of it these days is in relation to diesel engines but Gale Banks is a old Petrol head from way back and a true guru of adding boost to almost anything.

There is a reason his company builds a **** load of diesel engines for the US military.

Also running a brand new 14 in 1 digital gauge, shows a solid 13psi at 4th gear

 

[Immortality]

Measure the boost pressure coming out of the blower then you'll have a good idea what the pressure differential is through the A2A system.

 

[shane_3800]

To quote some yank who might know a thing about boost, "the boost gauge is dead" Gale Banks, and he is correct, boost is simply a measure of restriction but does not take into account the temperature of that air charge and temperature has a great effect on boost.

Have a look on youtube, he has lots of video's about boost and density, most of it these days is in relation to diesel engines but Gale Banks is a old Petrol head from way back and a true guru of adding boost to almost anything.

There is a reason his company builds a **** load of diesel engines for the US military.

Yea but a boost gauge is useful.
I find it foolish to suggest that.
You are correct in what you say, but boost measurement is essential to know what your charger is doing.

How do you electronically control a turbo without that information?
Yes it's a misunderstood measurement but is indeed essential.
You might note the Gale Banks always has a boost measurement, thus he spends the time to install a sensor.

 

[Immortality]

Yea but a boost gauge is useful.
I find it foolish to suggest that.
You are correct in what you say, but boost measurement is essential to know what your charger is doing.

How do you electronically control a turbo without that information?
Yes it's a misunderstood measurement but is indeed essential.
You might note the Gale Banks always has a boost measurement, thus he spends the time to install a sensor.

Boost is useful if you know what it should make so then you know when it's not making enough or too much.

You control a turbo by boost because that is what it creates but without knowing the temps just adding boost doesn't always make more power or make the car go faster if you are outside the tubro's efficiency range. Same goes with blowers.

 

[shane_3800]

Boost is useful if you know what it should make so then you know when it's not making enough or too much.

You control a turbo by boost because that is what it creates but without knowing the temps just adding boost doesn't always make more power or make the car go faster if you are outside the tubro's efficiency range. Same goes with blowers.

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.

 

[Pollushon]

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