Aussie Roller Cam

[Shelby]

haveing twice the back pressure as boost pressure is never going to be a good thing

why, once the turbo reaches set boost from that point on all the flow is not thru the turbine , the only change is the need'd exh volume to maintain that boost amount,, the entire rest of the exh flow MUST go out thru the wase gate port or waste gate valve , so if you are maintaining a back pressure 2 times that of the air intake charge your exh has way too much restrictive or the turbo is way out of it's ideal working range

useing the rates you post'd an engine runing 20 lbs boost is building over 40 lbs back pressure , not good and can you say HOT

 

example lets say you have a 35mm ext waste gate valve,, and it's set to maintain a boost of 10 lbs , what is realy happening in the exh manifold, pressure starts to build and if all is working right the waste gate will open @10 lbs , now the word open is realitive it dose not have to mean open wide open , but only far enought for the pressure to stabilize meaning the back pressure should almost match the boost air inlet pressures sence that is what is controling the wastegate opening , but air is compressiable so nothing is in direct relationship to whats happening else where theres a bit of catching up going on meaning the waste gates is not opening at a steady amount but it surges up and down playing catch up with the exact number it is supost

to be controling , a lot of this is cause'd by the length the inlet air charge has to travel and how much it cools as it makes it's journey along the nearly 14 foot of oem ic pipeing , how can that be well where the wastegate gets it's reading from can cause a lot of problems right off , if you use a port right out of the compressor houseing that figure and the one going into the head after the throddle plate can be way diff , lets say the waste gate is on the turbo out and the boost gauge is right near the throddle plate , the actual boost entering the intercooler and what the boost gauge is reading can be as much as 5 lbs diff

the waste gate is gona have to work off the highest boost figures in the entire system,

and that is usually right out of the compresor houseing port, not what you boost gauge may be saying on a port after the intercooler

so to fully understand what you back pressure readings are saying you need info at at least 3 diff points of referance 4 if you want to test the after turbo back pressure .

an lets say you have a no muffler 3" full exh system you'd most likely say there is no way you canhave any exh system back pressure at all right , wrong, at sea level you have a little over 13 lbs of air pressure on the inside of that pipe, the turbo must over come that air pressure in order for the exh to flow out ,not a heck of a lot we can do about that but it is a fact , sad thing is a turbo exh turbine is a poor air pump

 

 

now feel free to chop this to pieces if you care to

[toysrus]

haveing twice the back pressure as boost pressure is never going to be a good thing

 

That's a known fact. And like you said ONLY occurs once the Wastegate opens a set Boost level.

 

The obvious way to fix this is to run a "Pop-off valve" or Wastegate on the intake side. But then you need to switch over to a MAP sensor ECU and then again, why bother running an oversized Turbo to only run it at half the max air flow ? This is another topic though..

 

Short answer, look at how the Evo's progressed, they have the Turbo perfectly matched to the Engine and run it at near to max Boost.

 

[Dcrasta]

haveing twice the back pressure as boost pressure is never going to be a good thing

 

 

now feel free to chop this to pieces if you care to

 

Hey man We are all in agreement here as far as I can read. We are using 'strange' terminology Ie (Turbine Inlet Pressure / Manifold Inlet Pressure = Exhaust housing pressure, Intake manifold Pressure).

 

Given the numbers he says he is reading, that 20 PSI Intake manifold pressure should see less that 10PSI exiting the turbo (2:1 Ratio), not 40 PSI.

 

[stand down soldier]

Edited January 31, 2009 by Dcrasta

[TurboRaider]

I have to disagree. Even back in the 80's, manufacturers were already using complex mathematical models to design their cams. Now days you can run simulations on Ricardo and various other software packages to optimise a cam based on the complete Engine. But if you want to do it on the cheap, $50NZ isn't much to get Kelfords ( https://www.capella.co.nz/sites/kelford.co.nz/design-shop/ ) to design one for you. Again their software is only as accurate as the numbers you give them. The more data you can give them the better.

 

You can't go wrong sticking to the Factory cam profile and altering the overlap. Since there is no intake pulse tuning gains to be had due to the exhaust manifold. To bring a Turbo on Boost sooner, you really want the Intake Cam "area" to be as big as possible (Usually ridiculous lift numbers with mild duration) and then exhaust cam to be as efficient (min duration as possible). The engine operates as N/A in offboost conditions, and air intake = exhaust flow x some expansion number. So you can see how its the Intake cam that's the first point of restriction as to how soon a Turbo will come onto Boost. Obviously this is an over-simplified version of how it all works but you get the idea.

 

Not many people here have bothered to share information, time etc as much as Tim C and a few others have so try to help them along in their quest rather then just say they're doing it wrong.

 

Curious any ideas on how advanced the factory profile is? I'm sure its a pretty old design . The advanced math your referring to is it Polynomial, cycloidal or something past that? I plan on mapping out a few cams to get an understanding of the factory profiles so I'm curious what to look for once I get the data.

 

And once I get the data…. Who is capable of doing something better?

 

I always went with the goal was once you decided it was time to open the valve you used your cam design software to make that happen as fast as possible, tuning the profile to account for valve train acceleration limitations. You seem to imply that for some application this is not the case (associating lift and duration ratios with application).

 

Are you referring to the RPM compromise allowed with a turbo motor that allows for a faster valve acceleration? IE: since you don’t have to rev as high to make power, valve dynamics are less of an issue so you can open and close them faster allowing more lift for a given duration?

 

To me that’s more of the RPM range driving the design than a special acceleration profile to account for using a turbo (the profile / acceleration rates of course account for the amount of lift achived for a given duration and the goal would seem to be to maximize the area under the curve).

 

Has that changed?

 

That leave the cam differences between NA and a turbo to the usual, overlap and duration with the profile optimized for good dynamics within the motors operating range.

 

Am I missing something?

 

Thanks,

 

Kevin

Edited February 1, 2009 by TurboRaider

[Dcrasta]

Quick question.

 

All these cams we get when we switch to a mechanical setup, is that a turbo cam or are we all inadvertently replacing turbo cams with NA ones? The reason I ask is my Hydra head car feels better on boost than my old mechanical setup did, and it just dawned on me that we are probably getting caravan cams with these heads (Alabama Cylinder Head ) . A would think a big clue would be when you get a head with regular valves in it and a mechanical setup/cam. How can you tell if its a NA Cam (almost willing to bet most of them are). I know the quest came with a mechanical setup for the older cars (correct???). Another variable

 

 

[toysrus]

Also as far as cam designs go NA or not I always went with the goal was once you decided it was time to open the valve you used your cam design software to make that happen as fast as possible, tuning the profile to account for valve train acceleration limitations.

 

That's 100% correct.

 

There is no real RPM compromise other then the basic Engine piston speed relative to the intake choke diameter. So your current knowledge is up to date.

 

The gains between a fully optimised camshaft and an average camshaft is, luckily for us, of single digit percentages in FI setups. Camshaft development for restrictor class Engines (WRC etc) and 12,000+ RPM Engines is where things go beyond almost all well known camshaft houses. So in that sense, their is little to gain (other then possible job prospects) by doing an in-house or professional post-grad course in Camshafts. You could even say, you'ld get the final answer quicker by trial and error rather then book work first.

 

Anyhow, this is going beyond the scope of this topic. Feel free to PM me if you want to discuss things further.

[scott87star]

haveing twice the back pressure as boost pressure is never going to be a good thing

why, once the turbo reaches set boost from that point on all the flow is not thru the turbine , the only change is the need'd exh volume to maintain that boost amount,, the entire rest of the exh flow MUST go out thru the wase gate port or waste gate valve , so if you are maintaining a back pressure 2 times that of the air intake charge your exh has way too much restrictive or the turbo is way out of it's ideal working range

useing the rates you post'd an engine runing 20 lbs boost is building over 40 lbs back pressure , not good and can you say HOT wink.gif

 

example lets say you have a 35mm ext waste gate valve,, and it's set to maintain a boost of 10 lbs , what is realy happening in the exh manifold, pressure starts to build and if all is working right the waste gate will open @10 lbs , now the word open is realitive it dose not have to mean open wide open , but only far enought for the pressure to stabilize meaning the back pressure should almost match the boost air inlet pressures sence that is what is controling the wastegate opening , but air is compressiable so nothing is in direct relationship to whats happening else where theres a bit of catching up going on meaning the waste gates is not opening at a steady amount but it surges up and down playing catch up with the exact number it is supost

to be controling , a lot of this is cause'd by the length the inlet air charge has to travel and how much it cools as it makes it's journey along the nearly 14 foot of oem ic pipeing , how can that be well where the wastegate gets it's reading from can cause a lot of problems right off , if you use a port right out of the compressor houseing that figure and the one going into the head after the throddle plate can be way diff , lets say the waste gate is on the turbo out and the boost gauge is right near the throddle plate , the actual boost entering the intercooler and what the boost gauge is reading can be as much as 5 lbs diff

the waste gate is gona have to work off the highest boost figures in the entire system,

and that is usually right out of the compresor houseing port, not what you boost gauge may be saying on a port after the intercooler

so to fully understand what you back pressure readings are saying you need info at at least 3 diff points of referance 4 if you want to test the after turbo back pressure .

an lets say you have a no muffler 3" full exh system you'd most likely say there is no way you canhave any exh system back pressure at all right , wrong, at sea level you have a little over 13 lbs of air pressure on the inside of that pipe, the turbo must over come that air pressure in order for the exh to flow out ,not a heck of a lot we can do about that but it is a fact , sad thing is a turbo exh turbine is a poor air pump

 

 

now feel free to chop this to pieces if you care to

 

Now why would anyone want to chop that to pieces? This is great educational stuff but in the interest of the original thread topic I'm going to start a new thread as soon as I get the exhaust system pressure Shelby has mentioned. I originally didn't think it necessary as 3" is about as big as anyone goes but we still need to know what it is in order to make comparisons and I certainly know its above atmospheric pressure which is 15 psia here in Houston (at least it was yesterday). I have the other data you speak of, some of it is in the inter cooler specs thread, and you can see you are correct.

 

One thing I feel the need to comment on, you are taking to task the notion that 2X back pressure or TIP is bad. No argument here! Mine is over 2 and its the starting point for building my car. My point is that if you read Corky Bell's book the implication is that most OEM turbo system are far higher than 2X, maybe 3X or worse, so getting it down to that level still leaves a streetable vehicle as going much lower leads to high boost threshold. I for one would like to know the TIP on a stock 88 or 89 running 10.5 lbs stock boost, I know it has to be higher than what I measured. It's important because the Mitsubishi engineers knew all these numbers and whatever that value is they considered it safe for a production vehicle. Think about this in reverse, why do guys blow headgaskets and crack blocks? Because they only think of the intake side of the pressure distribution or "how much boost can I run?". How many threads in the archives have that title? Not knowing that the exhaust manifold or TIP pressure is 3X their "boost" number they crank it up to 15 (now 45 in the exhaust) and bang! Another rebuild thread. The correct question is "how much TIP can I run?", answer that and build accordingly and you'll have a reliable high boost car that is limited only by how high a boost threshold you can stand and the ultimate rpm limit of the motor.

 

Scott

[Dcrasta]

Now why would anyone want to chop that to pieces? This is great educational stuff but in the interest of the original thread topic I'm going to start a new thread as soon as I get the exhaust system pressure Shelby has mentioned. I originally didn't think it necessary as 3" is about as big as anyone goes but we still need to know what it is in order to make comparisons and I certainly know its above atmospheric pressure which is 15 psia here in Houston (at least it was yesterday). I have the other data you speak of, some of it is in the inter cooler specs thread, and you can see you are correct.

 

One thing I feel the need to comment on, you are taking to task the notion that 2X back pressure or TIP is bad. No argument here! Mine is over 2 and its the starting point for building my car. My point is that if you read Corky Bell's book the implication is that most OEM turbo system are far higher than 2X, maybe 3X or worse, so getting it down to that level still leaves a streetable vehicle as going much lower leads to high boost threshold. I for one would like to know the TIP on a stock 88 or 89 running 10.5 lbs stock boost, I know it has to be higher than what I measured. It's important because the Mitsubishi engineers knew all these numbers and whatever that value is they considered it safe for a production vehicle. Think about this in reverse, why do guys blow headgaskets and crack blocks? Because they only think of the intake side of the pressure distribution or "how much boost can I run?". How many threads in the archives have that title? Not knowing that the exhaust manifold or TIP pressure is 3X their "boost" number they crank it up to 15 (now 45 in the exhaust) and bang! Another rebuild thread. The correct question is "how much TIP can I run?", answer that and build accordingly and you'll have a reliable high boost car that is limited only by how high a boost threshold you can stand and the ultimate rpm limit of the motor.

 

Scott

 

Well said. We need to start compiling real data its long over due. Next turbo Manifold I put on my car will have provisioning for EGT probe and a TIP probe.

 

[Tim_C.]

My grinder's cams are consistently precision ground. I've had two cams that acted a bit wierd that could have been the grind, but I never got them back to return to the grinder so I could never say for sure. Most grinders are a lot sloppier than that. My point is I am willing to send our desired specs to the grinder to see if he can do it without losing a lot of base, or too much base loss to preload a hydraulic lifter. Otherwise we might just want to stick to a mechanical cam and live with a smaller base yet. It is best to use the '83 valves with a smaller base cam, even a mechanical one. That helps correct the geometry some.

 

Getting the perfect grind involves using blank cores or lobe welding, both of which are more expensive than most of us want to spend.

 

All OEM 2.6 L cams were NA, if that is what you were asking DC?

 

Maybe that is why the header is such a large gain on these engines. The TIP is much more efficient?

[Shelby]

ok heres the reason for the "chop this to bits" coment,, what i type is what i have learn'd on my own it's not from any books on turbo chargeing or basic force air engine

manuals , so some if not most of my knowlege is not scientific but real world experiances of a life time working on cars , and a little understanding of how some of it works

i ment to say heres my ideas what do you think and where am i wrong

 

i did do some real world exh system back pressure tests years back, on the stock exh and a 2.5" system , the stock system wo cats had over 1 lb of back pressure and the 2.5 with no cats not enought for my gauges to read , it had to have some but i had no way of reading it

now reading exh manifold pressure is something i have been meaning to get arround to but never seem to get done , i can say porting the exh houseing waste gate and passages did lower it a bunch , even after 5 1/4 runs i have never seen the exh manifold glowing

Edited February 2, 2009 by Shelby

[Dcrasta]

All OEM 2.6 L cams were NA, if that is what you were asking DC?

 

Maybe that is why the header is such a large gain on these engines. The TIP is much more efficient?

 

So our cam is the same as the other 2.6 (caravan) grinds? Wow. Im suprised by that. Maybe I should check out one of the turbo cams in the starion.au sites.

 

Headers are more efficient (from what Im reading) if they can keep the exhaust energy high and not allow the pulses to collide or reverse direction. Log manifolds sometimes can have reversion problems because sometimes 1 and 4 are aiming directly at each other.

 

 

[Tim_C.]

Yeah, all OEM 2.6L cams are pretty much the same with maybe a .007 difference in lift between mech and hyd.

That makes sense on the log. I am installing one of Chad's headers and a bigger turbo on my '87 as soon as I can get around to putting it on. I have a MAFT I am putting on too, until I get time to install the MPI.

[TurboRaider]

My M7 head just arrieved from AU.

 

So far it looks pretty decent, some light scoring of the cam journals but nothing to worry about.

 

The roller rockers have a slightly lower ratio than the V6 rollers. My guess would be 1.55 to1. That also says that using the V6 rollers with it would reduce the overlap slightly and increase the lift.

 

I will have more info once I get it stripped down.

 

Kevin

[Shelby]

i'l be looking for your info before i install mine , i'm realy looking for ward to see how the aussie roller will work

[Tim_C.]

That was my guess too. 1.55:1. The roller depth was in between the 1.5 and 1.6 roller rockers. I just wasn't sure that it was a direct indication of ratio, but it makes sense that it is.

 

Yes, I am anxious to see Kevin's measurements too.

[TurboRaider]

That was my guess too. 1.55:1. The roller depth was in between the 1.5 and 1.6 roller rockers. I just wasn't sure that it was a direct indication of ratio, but it makes sense that it is.

 

Yes, I am anxious to see Kevin's measurements too.

 

Me too.....

 

I got a pair of electronic drop indicators and an an rotary encoder to make the measurments today. I already have the data logger to read all three of them at the same time.

 

Whats left is to make a pair of mounts for the drop indicators to measure the valve opening and mount the rotary encoder to the cam. The company I work for was nice enought to let me borrow about $1100 worth of measuring equipment to run these test. I also got two software developers to help write a application to display the data.

 

Short term I can bring the raw numbers into a spread sheet for graphing and to find the opening and closing points.

 

Kevin

Edited February 4, 2009 by TurboRaider

[Tim_C.]

That is really awesome Kevin!

One thing to remember too is that a 1.xx ratio rocker only has that ratio in one general area of the wheelhouse so to speak. You probably won't see the full ratio anywhere either, especially with a hydraulic rocker. I've had guys measure my cams and get upset that the lift was .003 short! It all depends on the head, and other factors as to how much lift, duration, etc... you actually get. Plus, you are measuring actual figures, not advertised, like duration. Cam companies love to fudge those numbers to help sell the cam. They know that the set-up could possibly achieve those numbers, so they advertise it that way.

 

 

[Tim_C.]

Well, the head I ordered from Australia got lost in the mail! I have a few AUS cams and rockers to work with, but I don't have the AUS head I want to put on the CBRII car. I wanted to test it out on that car. I have a Magna intake with a Meag Squirt to put on too, but I might need to run the stock '83 TBI.

 

I am still putting an AUS cam in a fairly new marnal head for an '86 ESiR. I hope to have it running by the end of March.

[Shelby]

and our dear post office wants to raise rates to make up for their poor service :taz:

 

last summer i had one of the postal guys ask me ,, hey what is in them packages you send out,, i laugh and say some thing even your apes can't distroy solid steel plates ,

he said i wonder'd cause i drop'd one on my foot and it dam near took my toe off

would have if it wasn't for the steel toe'd shoes

[TurboRaider]

Well, the head I ordered from Australia got lost in the mail! I have a few AUS cams and rockers to work with, but I don't have the AUS head I want to put on the CBRII car. I wanted to test it out on that car. I have a Magna intake with a Meag Squirt to put on too, but I might need to run the stock '83 TBI.

 

I am still putting an AUS cam in a fairly new marnal head for an '86 ESiR. I hope to have it running by the end of March.

 

Tim,

 

Sorry to hear that.

 

To update the cam testing work. I machined up one of the adaptors I need and will make the other two on Thursday. I spent a bunch of time getting my basement hobby shop set up so I have a nice warm place to work. Lights wired, cat 5e drop for my computer, new monitor for the computer, microscope, oscilloscope, soldering iron and a few other things.

 

I still have to paint the walls and get my wifes craft shop done....

 

I should be able to take data and post results this weekend.

 

Kevin

[Shelby]

sorry Tim i for got to say i'm sorry also , any help from them or did you get the ol blank stare

[Tim_C.]

sorry Tim i for got to say i'm sorry also , any help from them or did you get the ol blank stare

 

The sender filed for an investigation. There were two boxes. One with the cams and rockers, and one with the complete head. That's about all i know at this point.

[Shelby]

good luck with the head lost thing,,

 

now you mention'd an important thing,, hyd lifter colapse,, there is no way he'l get any sort of acurate finding when useing an oil fill'd hyd lifter,,the lifter is gona have to be "0" lash'd by some mechanical means (spacers ,shims ,etc )

 

been there done that

[Tim_C.]

Tim,

 

Sorry to hear that.

 

To update the cam testing work. I machined up one of the adaptors I need and will make the other two on Thursday. I spent a bunch of time getting my basement hobby shop set up so I have a nice warm place to work. Lights wired, cat 5e drop for my computer, new monitor for the computer, microscope, oscilloscope, soldering iron and a few other things.

 

I still have to paint the walls and get my wifes craft shop done....

 

I should be able to take data and post results this weekend.

 

Kevin

 

Cool. As long as your wife knows we need your info worse than she needs her craft shop done! :eek1bluegreen: That should go over real well!

 

No, I'm in no big hurry. I haven't sent the other cam out to my grinder yet either! Too much going on it seems.

 

Shelby: Yeah, he knows the deal on getting these measurements. I haven't said anything Kevin doesn't already know. I think I remember he was measuring cams before and used a solid metal insert for the lifter.