[v869tr6]

Finely put in a gauge to see what the back press in the turbine is compared to boost.
Was switching programs around and it looks like the boost controller isn't happy, must have switch it off of duty cycle and back to trying to control boost, oh well, boost pegs the 20 psi boost gauge but back pressure is only slightly higher then boost. Tells me the baby cam is what's holding the combo back.
Quick pull in Drive, but it just shows the dash.
https://www.youtube.com/watch?v=ZM_K...ature=youtu.be

[charlie66]

Cant view the video says its private , But its good you're checking things like this, you will learn a lot..

[Tom Vaught]

Only slightly higher exhaust pressure vs boost is not really a bad thing for a street driven car.

Some Race cars will make more boost vs turbine pressure but that is many times due to an in-efficient intake system.

The turbine has to have enough energy to move the compressor wheel to make the boost and if the exhaust pressure is too low then the compressor load basically flat lines the boost even without the wastegate working much. All about energy and how you use it. if you have 35 psi of boost and 38 on the back pressure you still have 35 psi making a lot of power in the engine.

Tom V.

[v869tr6]

I switched it to unlisted, maybe it will work?
Lame video, but it really helps to get video to watch what I can't as the car is moving.
Looks like back pressure is only a little over 1 to 1 and that really surprised me.
The Luhn oil pump held steady at about 60 psi

[charlie66]

It looks like you have it under control. Next time give us some sound .. lol

[charlie66]

Originally Posted by Tom Vaught

Only slightly higher exhaust pressure vs boost is not really a bad thing for a street driven car.

Some Race cars will make more boost vs turbine pressure but that is many times due to an in-efficient intake system.

The turbine has to have enough energy to move the compressor wheel to make the boost and if the exhaust pressure is too low then the compressor load basically flat lines the boost even without the wastegate working much. All about energy and how you use it. if you have 35 psi of boost and 38 on the back pressure you still have 35 psi making a lot of power in the engine.

Tom V.

Maybe that's why I have less back pressure then boost. Interesting. Is there some sort of a test that can be done to see if a in sufficient intake is causing this, to confirm this when less back pressure then boost happens?

Thanks

[v869tr6]

Now that I have the gauge, which only cost around $20, I am going to check the pressure difference from the turbo outlet to the intake were the dash mounted boost gauge reads. Mainly to see what restriction the 1000 hp e-bay air/water intercooler has.

[Tom Vaught]

We have Pressure Surveyed "Tested" the pressure out of the turbo to the inter-cooler, pressure drop across the inter-cooler, pressure to the throttle body (or carb bonnet), and pressure in the intake runner.

Steve Morris at one time had a 500 cid Chebby engine that was making "X" psi of boost.
The pressure drop across his crummy inter-cooler was 2-4 psi, (he later upgraded to a inter-cooler with about .75-1.0 psi pressure drop).

At 1700 HP the Holley HP 1000 carb was dropping the boost pressure 3 psi across the carb (air restricted by the carb before the air went thru the carb and into the intake).

A Bigger carb (Dominator and Dominator carb intake later allowed over 2000 HP. So it is worth checking the stuff.

Tom V.

[charlie66]

Originally Posted by v869tr6

Now that I have the gauge, which only cost around $20, I am going to check the pressure difference from the turbo outlet to the intake were the dash mounted boost gauge reads. Mainly to see what restriction the 1000 hp e-bay air/water intercooler has.

Sound like a good idea. Keep us posted..

[charlie66]

Originally Posted by Tom Vaught

We have Pressure Surveyed "Tested" the pressure out of the turbo to the inter-cooler, pressure drop across the inter-cooler, pressure to the throttle body (or carb bonnet), and pressure in the intake runner.

Steve Morris at one time had a 500 cid Chebby engine that was making "X" psi of boost.
The pressure drop across his crummy inter-cooler was 2-4 psi, (he later upgraded to a inter-cooler with about .75-1.0 psi pressure drop).

At 1700 HP the Holley HP 1000 carb was dropping the boost pressure 3 psi across the carb (air restricted by the carb before the air went thru the carb and into the intake).

A Bigger carb (Dominator and Dominator carb intake later allowed over 2000 HP. So it is worth checking the stuff.

Tom V.

Thank you Tom

[BruceWilkie]

Quote:
Originally Posted by Tom Vaught View Post
Only slightly higher exhaust pressure vs boost is not really a bad thing for a street driven car.

Some Race cars will make more boost vs turbine pressure but that is many times due to an in-efficient intake system.

The turbine has to have enough energy to move the compressor wheel to make the boost and if the exhaust pressure is too low then the compressor load basically flat lines the boost even without the wastegate working much. All about energy and how you use it. if you have 35 psi of boost and 38 on the back pressure you still have 35 psi making a lot of power in the engine.

Tom V.

Originally Posted by charlie66

Maybe that's why I have less back pressure then boost. Interesting. Is there some sort of a test that can be done to see if a in sufficient intake is causing this, to confirm this when less back pressure then boost happens?

Thanks

Keep in mind ...there may be nothing wrong as well. Positive delta pressures are not necessarily a bad thing.

Pressure read in the manifold or turbine housing, or for that matter individual ports is only going to be a number between peak and zero(possibly negative). At least with any instrumentation you or I might have.
So basic gauge is only telling you that you might have a restriction on one side or the other.
Manifolding may be fine and perhaps more or less overlap window may be an area to explore.
You can flow your head, intake and throttle on a bench and resolve restrictions there especially if your intake wasnt ported to your heads.

Ultimately nothing can go in the chamber until chamber pressure becomes lower than the intake pressure. If you have NO overlap window nothing goes in until piston moves sufficiently past TDC to lower chamber pressure below intake port pressure. That situation effectively decreases amount of charge available AND mixes with at least a chambers worth of hot spent residual charge. Neither of which are desirable.

SOME overlap window AND low or positive delta pressure allows some purge of the chamber while piston goes thru tdc dwell/overlap. This effectively is like adding CI and allows for less charge dilution. This = greater power potential !

Exhaust backpressure(pre wastegate/turbine) also affects chamber pressure exchanges!

As long as you have good or better turbine response low to positive delta is desirable.
When delta goes significantly negative(much higher exhaust pressure than boost) it can limit power. Power cant increase as much as it should for the amount of boost seen at the intake.(example raise boost to 30 psi and car barely picks up or doesnt pick up over 25 psi setting)

[BruceWilkie]

Originally Posted by v869tr6

Finely put in a gauge to see what the back press in the turbine is compared to boost.
Was switching programs around and it looks like the boost controller isn't happy, must have switch it off of duty cycle and back to trying to control boost, oh well, boost pegs the 20 psi boost gauge but back pressure is only slightly higher then boost. Tells me the baby cam is what's holding the combo back.
Quick pull in Drive, but it just shows the dash.
https://www.youtube.com/watch?v=ZM_K...ature=youtu.be

Exhaust opening rate and point where it opens/closes are worth looking at as well as overlap window.

Be careful with closing rates on either side(valvetrain control).
Generally open rate can be faster than close rate.
Dump as much exhaust pressure as you can BBDC without excessively heating your exhaust when cruising. Race only can dump sooner than street/strip combo.

[charlie66]

Originally Posted by BruceWilkie

Quote:
Originally Posted by Tom Vaught View Post
Only slightly higher exhaust pressure vs boost is not really a bad thing for a street driven car.

Some Race cars will make more boost vs turbine pressure but that is many times due to an in-efficient intake system.

The turbine has to have enough energy to move the compressor wheel to make the boost and if the exhaust pressure is too low then the compressor load basically flat lines the boost even without the wastegate working much. All about energy and how you use it. if you have 35 psi of boost and 38 on the back pressure you still have 35 psi making a lot of power in the engine.

Tom V.




Keep in mind ...there may be nothing wrong as well. Positive delta pressures are not necessarily a bad thing.

Pressure read in the manifold or turbine housing, or for that matter individual ports is only going to be a number between peak and zero(possibly negative). At least with any instrumentation you or I might have.
So basic gauge is only telling you that you might have a restriction on one side or the other.
Manifolding may be fine and perhaps more or less overlap window may be an area to explore.
You can flow your head, intake and throttle on a bench and resolve restrictions there especially if your intake wasnt ported to your heads.

Ultimately nothing can go in the chamber until chamber pressure becomes lower than the intake pressure. If you have NO overlap window nothing goes in until piston moves sufficiently past TDC to lower chamber pressure below intake port pressure. That situation effectively decreases amount of charge available AND mixes with at least a chambers worth of hot spent residual charge. Neither of which are desirable.

SOME overlap window AND low or positive delta pressure allows some purge of the chamber while piston goes thru tdc dwell/overlap. This effectively is like adding CI and allows for less charge dilution. This = greater power potential !

Exhaust backpressure(pre wastegate/turbine) also affects chamber pressure exchanges!

As long as you have good or better turbine response low to positive delta is desirable.
When delta goes significantly negative(much higher exhaust pressure than boost) it can limit power. Power cant increase as much as it should for the amount of boost seen at the intake.(example raise boost to 30 psi and car barely picks up or doesnt pick up over 25 psi setting)

You're reaching over my head some what with that explanation Bruce . lol! When you say over lap window do you mean over lap of the cam? I think I have 18 degrees...

[BruceWilkie]

Originally Posted by charlie66

You're reaching over my head some what with that explanation Bruce . lol! When you say over lap window do you mean over lap of the cam? I think I have 18 degrees...

Overlap window is what the engine "cares" about. 18 degrees only tells you timing point to timing point. Whats occurring at the valve is more important to understand.
Actual point the intake comes off the seat and point exhaust fully seats are important and tells you how long(duration) the window is open. How high and fast the window gets opened affects how much gets thru.

So look at overlap as a window that needs both width(duration) and height to help determine how much can get thru.

Boosted you want as much chamber purge as you can get while the piston is nearly parked thru tdc without blowing excessive amounts of raw fuel into your turbine.
So you trade time the overlap window is open for how high the overlap window its open.
Ramp rates on the cam combined with rocker ratio is how this is controlled.
There are limits to how fast you can open/close valves and surprisingly you can push opening rates faster than closing rates.
Closing too fast is easier to lose valve control and create harmonic havoc, valve bounce etc..


A real learning experience that helps visualize whats occurring is to map a cam on a V8. Cylinder head off on passenger bank and dial indicator(s) on #1 cylinders valve retainers. #6 cylinder will show you where #1 piston is in relation to your valve movements on #1 and your degree wheel is there for you to see/map the timng points.

Observing where the piston actually is(#6 piston movement mirrors #1 piston movement) at any given timing point combined with dial indicator telling you how far the valve(s) moved is quite enlightening. (its also kind of tedious)

PS you can cheat if you just want a basic visual! Use a 1 cylinder flathead motor(lawnmower) and observe piston/valve movement simply by taking the head off. The valves are in the block.

[v869tr6]

Charlie, Bruce and Tom thanks for the input.
Going to hook the gauge to the compressor outlet tonight.
The gage I have is rated at 1.5% error, don't know what the aeromotive boost gauge in the dash is rated at but I will see what the difference is.
Now that I know the turbine isn't at 2 or 3 to one I think the turbo will still support my needs.
Once I have the stud torque issue resolved I don't care if I have to go past 30 psi to get to the power level I need to go sub 8.50's
Next time the heads are off I plan to put the sleeves that Charlie has used, as the top hat washer are helping but aren't the answer for the studs the go thru the exhaust

[charlie66]

What I do is after I check the differences in exhaust pressure and intake pressure I swap the gages to see if they stay the same numbers..

My studs don't move one bit any more. Those sleeves really did solve that sinking problem ... You wont be sorry...

[charlie66]

Originally Posted by BruceWilkie

Overlap window is what the engine "cares" about. 18 degrees only tells you timing point to timing point. Whats occurring at the valve is more important to understand.
Actual point the intake comes off the seat and point exhaust fully seats are important and tells you how long(duration) the window is open. How high and fast the window gets opened affects how much gets thru.

So look at overlap as a window that needs both width(duration) and height to help determine how much can get thru.

Boosted you want as much chamber purge as you can get while the piston is nearly parked thru tdc without blowing excessive amounts of raw fuel into your turbine.
So you trade time the overlap window is open for how high the overlap window its open.
Ramp rates on the cam combined with rocker ratio is how this is controlled.
There are limits to how fast you can open/close valves and surprisingly you can push opening rates faster than closing rates.
Closing too fast is easier to lose valve control and create harmonic havoc, valve bounce etc..


A real learning experience that helps visualize whats occurring is to map a cam on a V8. Cylinder head off on passenger bank and dial indicator(s) on #1 cylinders valve retainers. #6 cylinder will show you where #1 piston is in relation to your valve movements on #1 and your degree wheel is there for you to see/map the timng points.

Observing where the piston actually is(#6 piston movement mirrors #1 piston movement) at any given timing point combined with dial indicator telling you how far the valve(s) moved is quite enlightening. (its also kind of tedious)

PS you can cheat if you just want a basic visual! Use a 1 cylinder flathead motor(lawnmower) and observe piston/valve movement simply by taking the head off. The valves are in the block.

Thank you Bruce, Now im even more confused ! lol! I wish I had your understanding on this stuff....

[BruceWilkie]

Charlie about 53 yrs ago when I was in 5th grade I took Dads new lawnmower apart to see what made it work. (Why I didnt mess with old one is beyond me)
Thats where I got my 1st visual of piston movement vs valve movement.

I got my azz skinned then had to make it run again(plus mow lawn the rest of my life lol).

At that age all I knew was 4 cycle...intake/compression/power/exhaust. Had no idea there were timing marks for the cam and the point cam had to be in right place too. I got to take it apart a few times but finally did get it running in time to mow the grass. The old mowers engine soon found it way onto a homemade go-kart...a motorhead was born.

Dad still remembers and thinks of me anytime his lawnmower gives him trouble lol

[charlie66]

Originally Posted by BruceWilkie

Charlie about 53 yrs ago when I was in 5th grade I took Dads new lawnmower apart to see what made it work. (Why I didnt mess with old one is beyond me)
Thats where I got my 1st visual of piston movement vs valve movement.

I got my azz skinned then had to make it run again(plus mow lawn the rest of my life lol).

At that age all I knew was 4 cycle...intake/compression/power/exhaust. Had no idea there were timing marks for the cam and the point cam had to be in right place too. I got to take it apart a few times but finally did get it running in time to mow the grass. The old mowers engine soon found it way onto a homemade go-kart...a motorhead was born.

Dad still remembers and thinks of me anytime his lawnmower gives him trouble lol

Lol! I remember doing that once or twice, as well as taking apart my father brand new vacuum cleaner , an I can tell you that , that didn't go to well in his eyes , but unfortunately I didn't get the education you did out of it. haha. But I did turn in to a motorhead because of things like that !

I definitely would like to learn more about getting optimal valve timing for a boosted motor..

[taff2]

Want optimal cam timing for your boosted engine? Call one of the good cam manufacturers/grinders with all your details and ask for a recommendation! They have far more experience and knowledge on these matters than most of us have.
If however you want to learn about these things then there is a lot of info out there,just couple that with about 20 years experience and you will be good to go.