[Yozh]

Originally Posted by iaknown

Ahhh, I wasn't quite following you from the beginning then to be honest. I see where you're going now and am a bit intrigued

I'm very intrigued as well but I do not know what the heck you guys are talking about.

[tuikku]

Originally Posted by petey_highboost

I made 804whp on a 2L mitsubishi engine @ 43psi on e85 with a 3" full turbo back

I do really appreciate your results, but I am talking about 3L, diesel`s as you very well know.

[tuikku]

Originally Posted by Bob@BPC

Some more tech data, Look at how much smaller the M57 intake and exhaust ports are compared to the N52. I would love to see one of these heads ported out

Waste of time...
First you have to get the max aut from stock engine.
It is somewhere above 600hp with stiffer valve springs.
No-one knows piezo injectors that can give that power.

We have here solenoid ones, which are good up to ~700hp.
Suitable to mb.

[HeatherM35d]

Originally Posted by Bob@BPC

So you have ported one out? How do you know?

I would say if there is any trace of smoke then porting a head would lean out the mixture which would burn up fuel you're already injecting. This would help make more power and lower egts.. No matter what horsepower level you're at.

[TDIwyse]

Regarding the exhaust diameter, here's a couple examples I recently came across that compared 3" to 3.5" and what impact it had on high powered turbo vehicles.

One car seemed to show significant gains, one car showed basically no gains.

http://highboostforum.com/forum/show...test-from-2007

http://www.superstreetonline.com/how...ust-test-tech/

[tuikku]

Originally Posted by Bob@BPC

So you have ported one out? How do you know?

Yes I have
Results you can see above, 530d with one (small) vnt turbo.
The thing that helps, was stiffer valve springs, as I told before.

I have ported two MB engine also, OM646 and OM613, same results.
Head flows very good as stock, porting these cdi-engines is not so easy job, if you want some progress also, I doubt that anyone there can do it properly.
There is something more in this case than air flow.

[tuikku]

Originally Posted by TDIwyse

Regarding the exhaust diameter, here's a couple examples I recently came across that compared 3" to 3.5" and what impact it had on high powered turbo vehicles.

One car seemed to show significant gains, one car showed basically no gains.

http://highboostforum.com/forum/show...test-from-2007

http://www.superstreetonline.com/how...ust-test-tech/

No diesel ....
I have a stock exhaust pipe with stock catalysator in my car ....
You can easily measure the back pressure of exhaust pipe.

[TDIwyse]

Originally Posted by tuikku

No diesel ....
I have a stock exhaust pipe with stock catalysator in my car ....
You can easily measure the back pressure of exhaust pipe.

That might be part of the reason your exhaust manifold pressure is so high?

I've measured the exhaust back pressure before to verify the urea catalyst (SCR) was plugging after many miles of driving after removing the DPF/DOC.

http://www.e90post.com/forums/showpo...7&postcount=60

I'm wanting to measure the back pressure again since i'm pushing more power/flow, and I want to know what the pressure delta is across the turbine. The previous data I posted on Exhaust Manifold Pressures includes the turbine plus the rest of the exhaust.

[tuikku]

.
Higher back ressure in exhaust pipe means lower back pressure in manifold.
Think it for a while, and you agree my opinion.

[TDIwyse]

Originally Posted by tuikku

.
Higher back ressure in exhaust pipe means lower back pressure in manifold.
Think it for a while, and you agree my opinion.

I'm interested in the turbine drive pressure to boost ratio, to see how hard the turbo is working to make boost. If the sensor in the exhaust manifold measures 56 psi, and the pressure post turbine in the downpipe is (picking a number close to what I previously measured) 4psi, wouldn't the pressure across the turbine have to be 52 psi?

[tuikku]

.
This is difficult to explain even with my own language...

There is a small back pressure in exhaust pipe, that slows down gas flow, not much but ...
When that ends.
Flow and pressure across the turbine increases, or it seems that it will.
Then the only thing that resists gas flow is turbine, all the pressure comes now against it, total amount of flow does not decrease or increase.

If if the bigger pressure ratio now across the turbine wings tries to push the wing in higher revs to decrease back pressure, => boost pressure likes to rise and system stops it.
=> back pressure rises, nothing more happens.

If I release boost pressure a bit higher , turbine/compressor goes overspeed, or boost rises to sky.

"Smaller" exhaust pipe does not matter when turbo starts spooling, work.
But it helps to keep the (stock) turbo alive in extreme conditions.

Bigger turbo changes the whole idea completely.

[TDIwyse]

Got my first stab at measuring this. Roads are kinda slick and I lost traction in 4th at about 4300 rpm... Hoping to get better data when things dry out.

The pressure in the downpipe (DP) is a few inches after the turbine. The EMP is the exhaust manifold pressure.

This is much better psi than when the SCR was in place...

[tuikku]

.
You have now measured exhaust gas pressure from both side of the turbine wheel.
Not EMP vs exhaust pipe.

[TDIwyse]

Originally Posted by tuikku

.
You have now measured exhaust gas pressure from both side of the turbine wheel.
Not EMP vs exhaust pipe.

Correct. This is what I was wanting to know. Now I know how much pressure is across the turbine (EMP - DP pressure = pressure across turbine).

What would be interesting now, is to put a bigger diameter exhaust system on the vehicle and compare. However, having the exhaust pressure <2psi, I'm thinking that's pretty good. When the SCR was still in place I was measuring ~5-7 psi.

[tuikku]

.
Ok
Sorry, I don`t understand.

[TDIwyse]

Originally Posted by tuikku

.
Ok
Sorry, I don`t understand.

Well, if I know how much turbine pressure it takes to produce a given boost pressure, and I also know how to measure the mass air flow (beyond the limit of the OEM MAF), I can get insight into the compressor map of this external waste gated system. Then, one could make an educated comparison against other options. Assuming the manufacturer's or users of these other options would also post data...

Without data, you're just another person with an opinion - Edwards Deming

[TDIwyse]

A good discussion regarding why measuring the pressures on both sides of the turbine is enlightening, and how the size and back pressure of the post turbine exhaust system impacts turbine efficiency. The quoted section from the Garret turbo engineer is very enlightening as he goes over exactly how this exhaust back pressure affects the turbine.

http://forums.tdiclub.com/showthread.php?t=130644

"Here's a worked example (simplified) of how larger exhausts help turbo cars:

Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say, 10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is:
(14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure

So here, the turbine contributed 19.6 psig of backpressure to the total.

Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine discharge. In this case the engine sees just 17 psig total backpressure! And the turbine's contribution to the total backpressure is reduced to 14 psig (note: this is 5.6 psig lower than its contribution in the "small turboback" case).

So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is where all the engine's VE gains come from.
"

[tuikku]

.
How do you intend to take advantage of that lower back pressure ?
Back pressure is just a tool, nothing more.
As long as the turbo works, as I like, I do not care about it, it just a tool.
These diesels work just as good as you get the turbo working.

You need a bigger turbo, it is clear.
And with it, every numbers got better too...

Look after your earlier measurements.
There is still a thing, that I have not talked before.
If turbo just can do it, a little bigger boost gives more power, even though it do not give more air.
Why ?
Because, in these di-diesels air flow just do not tell everything.
There is still one thing left, swirl.
Swirl is the main thing, pure max air flow is not enough.

[TDIwyse]

Originally Posted by tuikku

.
How do you intend to take advantage of that lower back pressure ?
Back pressure is just a tool, nothing more.
As long as the turbo works, as I like, I do not care about it, it just a tool.
These diesels work just as good as you get the turbo working.

You need a bigger turbo, it is clear.
And with it, every numbers got better too...

Look after your earlier measurements.
There is still a thing, that I have not talked before.
If turbo just can do it, a little bigger boost gives more power, even though it do not give more air.
Why ?
Because, in these di-diesels air flow just do not tell everything.
There is still one thing left, swirl.
Swirl is the main thing, pure max air flow is not enough.

I was curious if there was going to be any advantage to going with a bigger exhaust, which could theoretically lower backpressure, which would allow the turbine to be more efficient, which would make the whole turbo work more efficiently . But the back pressure I measured showed the system I have is doing a good job as it is.

Regarding the power vs boost statement ... I have looked at my previous measurements (and a lot I haven't posted), and I do not see an increase in power with the last increasing boost setting. The AFR's were better, the EGT's were better, EMP's a little higher ... but no more power. In fact, the power was a little lower ... but it was within the margin of what I'm able to do in a repeatable fashion.

I was hoping to do more testing on this with a more sophisticated electronic boost controller for my EWG where I can tailor the boost/EMP curve vs rpm and further optimize the power tradeoffs. First test run with this controller was tonight. So far I'm not impressed and the simple manual boost controller kicks it's arse. However, I haven't tried using the rpm dependent control feature yet.

[DWR]

Originally Posted by tuikku

.
If turbo just can do it, a little bigger boost gives more power, even though it do not give more air.
Why ?
Because, in these di-diesels air flow just do not tell everything.
There is still one thing left, swirl.
Swirl is the main thing, pure max air flow is not enough.

Swirl is created by velocity. The importance of swirl is homogeneity of the mixture. Homogeneous diesel/air mixtures burn more quickly. This means the combustion pressure can be more optimally timed in crankshaft degrees. It is possible to have higher velocity for a shorter duration and not flow more air.

The situation will do exactly as you say. With increased back pressure, additional exhaust will be left in the cylinder. When the intake valve opens, the higher boost will increase the velocity of the incoming air. However, the cylinder will appear smaller due to the residual exhaust, therefore the intake event will essentially be shorter. Net airflow will not increase as expected.

However, swirl is by no means the "main thing". If that were true, then you should close the 2nd intake port, and make more power, because that will create the highest swirl.

Here's the deal though. If you increase the boost and reduce the expansion ratio (increase the turbine's phi), you get more swirl and more air. Let's agree that both of these will lead to more HP.

[tuikku]

.
I almost agree.
Theory and practice are not now exactly the same.

The first port do the swirl mainly - yes, but that is not the whole thing.
Swirl collapses, when air flow speed become too high.
The second port has two as important jobs, more air and keep the swirl alive by reducing total air flow speed.
Controlled air speed and a lot of boost gives the best swirl and best result.
I do not give up on this matter.
More air is useless without swirl, tested.
It is very very easy to spoil the head by porting it so that airflow is great but do not work, at all, smaller amount of air with good mixing gives better result.


Really hope, that you understand, what I am tried to tell.

[HeatherM35d]

Maybe the true solution is a high flow head, lower compression, lots of boost and a high swirl piston design. But I don't want to give you details on the entire build. Getting a little side tracked on this thread with riddles.