tubular exhaust manifold: 4-1 vs 4-2-1

JST · Apr 6, 2015

Just checked it. Also it looks that Banks does not apply equal lengths, probably to keep headers as short as possible.
http://assets.bankspower.com/prod_inline_images/1299/PowerPickle_illo.jpg

Jakx1331 · Apr 6, 2015

Some of them are like the ones for amc 4.0 l6. Put one on a jeep xj. But I meant the comment to be a idea to test

Jakx1331 · Apr 8, 2015

So any data?

JST · Apr 9, 2015

Jakx1331 said:
So any data?

I'm still waiting to receive the manifold... the photos were sent by the builder.

Jakx1331 · Apr 10, 2015

When do you think you're going to get it?

JST · Apr 10, 2015

Jakx1331 said:
When do you think you're going to get it?

Somewhere next week. And after that, I'll have to find spare time to fit it.

JST · Apr 19, 2015

I came across this youtube film which explains the mighty mercedes 2014 F1 power unit (1.6 V6 turbo).
One interesting detail is, is has log type exhaust manifolds rather than "conventional" tubular headers! Comment at 5:30

https://www.youtube.com/watch?v=WD4KJorL0wQ

Jakx1331 · Apr 19, 2015

So there saying log style will make more power and boost

JST · Apr 21, 2015

Finally I received the tubular header.
Some specs: header diameter 42.6mm OD, header length about 32-33 cm, totale internal volume about 1300 cc.
So that is roughly 2 times the volume of the standard manifold.

diffas · Apr 22, 2015

Jakx1331 said:
So there saying log style will make more power and boost

Yea. There are no secret on that, that good log type gives you best power.

Jakx1331 · Apr 22, 2015

I'm looking for the best bottom end power/boost. Quicker spool up for rock crawling. Horse power is not wanted.

diffas · Apr 22, 2015

Keep the manifolds as short as possible.

JST · Apr 22, 2015

Jakx1331 said:
I'm looking for the best bottom end power/boost. Quicker spool up for rock crawling. Horse power is not wanted.

Then the obvious choice is logstyle.

I'm thinking about building a 2nd manifold (this time by myself) with same diameter pipes, but as short as possible. So basically similair to the OEM manifold but with better merge and larger outlet diameter, matching the turbine.

Now let's find some spare time to fit this, that's hard these days.

daniel. · May 1, 2015

JST said:
Then the obvious choice is logstyle.
I'm thinking about building a 2nd manifold (this time by myself) with same diameter pipes, but as short as possible. So basically similair to the OEM manifold but with better merge and larger outlet diameter, matching the turbine.
Now let's find some spare time to fit this, that's hard these days.

... Thats it? Someone told you that the log manifold is better than equal runner tubular one and you agree without testing?

Jakx1331 · May 1, 2015

It sucks that we wont know which one is better for a different task. If I had a jetta I'd test this.

JST · May 3, 2015

daniel. said:
... Thats it? Someone told you that the log manifold is better than equal runner tubular one and you agree without testing?

Please read again. Ofcourse I'm not spending a considerable amount of money on a tubular header to put it on a shelf...

I'm halfway now, I expect to make the first tests with the tubular Monday.

Digital Corpus · May 3, 2015

When updating my tune last year my tuner made the comment that my GTB1756 is spooling faster than a VNT17. Then again my head and manifold are port matched, my manifold + adapter + hotside inlet are ported and matched, and I chamfered the hotside outlet to the 2.5" downpipe.

JST · May 4, 2015

Bad luck...
The tubular doesn't fit as it fouls my aircon lines.

I guess I have to cut this header out and route it more upwards...

JST · May 8, 2015

Ok, so after a few fitment issues I managed to mount it.
The first impressions of the tubular headers:
- More linear power delivery, less agressive
- A bit more turbolag
- Slightly changed sound note at rpm>3000 (in a better way!)
- For sure significantly lower EGT

The biggest difference is less torque rise in the 2000-2500 rpm area, probably caused by lower EGT feeding the turbo which then boosts slower. Also at part throttle I used to have a change in acceleration when the VNT opens after spoolup, this is dissapeared.
The top end feels strong, but this could be an impression because of the less agressive low end.
I still have to do the datalogs to see how acceleration (power) is really changed in the rev range.

daniel. · May 9, 2015

Thank you for shearing this mate... Can't wait for the datalogs. For me the biggest advantage of the tubular manifold is lowering the EGT values and I assume it will have bit more power at the top end.

JST · May 9, 2015

So finally some hard numbers. I have to do some more logging to get more consistent results, but for now it gives a clear picture.
The thing that really, really amazes me is the EGT. It is down A LOT!
I'm talking 400+ deg C less than before. So there's a lot of heat loss between the cylinderhead and turbocharger which probably is the cause of slower spool.
I've plotted some acceleration times for tunes 8b, 9 and 10 with log and tune 10 with tubular. You will see it is a bit slower than before, like inbetween tune 8b and 9. But I supect if some exhaust heat can be recovered, this might improve.

Datalogs log vs tubular:

Boost curve:

Acceleration times, measured in 4th gear:

mk1-83 · May 9, 2015

So with tubular you lost 400* egt. This comes to the long individual runners.
Because they are longer and separated they cool way faster then a log style manifold.

Terry270 · May 9, 2015

Be interesting to see what effect wrapping the runners would have.

Digital Corpus · May 9, 2015

I don't suspect heat loss is the reason for the turbo lag, but it's causing the lower EGTs. If this is true, then wrapping the manifold will net higher EGTs and not change turbo response.

The reason in my mind as to why the turbo's lag is greater in the tubular is simply due to the increased volume of the manifold. If you have some way to measure the volume of water you can fit into each, that'll help add another data point.

Fix_Until_Broke · May 9, 2015

So, on one hand, you could add that much more fuel to get EGT's back to where they were which could net significantly more power, but something seems wrong about this...

andy2 · May 9, 2015

There is likely a pretty large temp drop between the cylinder head exhaust port and the turbine inlet.One way to prove this would be to move the egt probe close to one of the cylinder head exhaust ports to measure the temp difference.

JST · May 9, 2015

Digital Corpus said:
I don't suspect heat loss is the reason for the turbo lag, but it's causing the lower EGTs. If this is true, then wrapping the manifold will net higher EGTs and not change turbo response.

The reason in my mind as to why the turbo's lag is greater in the tubular is simply due to the increased volume of the manifold. If you have some way to measure the volume of water you can fit into each, that'll help add another data point.

I do think the heat loss is a major cause. The hotter the turbine is, the higher it boosts.
I already measured both volumes, it is 450cc for the log and 1300cc for the tubular. Ofcourse this tripled volume also will have its effects.

Fix_Until_Broke said:
So, on one hand, you could add that much more fuel to get EGT's back to where they were which could net significantly more power, but something seems wrong about this...

If I would add 400 degrees EGT it would probably melt the pistons.
Don't forget I am measuring at one point, just before the turbine and this point has moved about 150-200mm further away with the tubular.

andy2 said:
There is likely a pretty large temp drop between the cylinder head exhaust port and the turbine inlet.One way to prove this would be to move the egt probe close to one of the cylinder head exhaust ports to measure the temp difference.

Agreed, it would be interesting to see the temp drop in the manifold. Same for the log one.
I think a logical next step is to wrap the manifold and see if it brings the EGT back up.

mk1-83 · May 10, 2015

Does it smoke more as less then with log style ?
Egt you can also see on how much it smoking.
When mine TDI get a little black smoke egt are around 900*
Backing the fuel and see almost no smoke egt are 850*

JST · May 10, 2015

mk1-83 said:
Does it smoke more as less then with log style ?
Egt you can also see on how much it smoking.
When mine TDI get a little black smoke egt are around 900*
Backing the fuel and see almost no smoke egt are 850*

It is the same. Smokeless to 4000 rpm and a light haze above that. Looking at the logs, you will see that the amount of air and fuel is not changed.

JST · May 10, 2015

I did some more datalogging today, because I was not satisfied with the results from yesterday. The circumstances were far from ideal with quite some wind, heavy traffic (could not perform full rpm range all the time) and the undertray missing from the car.

So I did them over today and got much much more constant results and when I looked closer I was delighted about it.
The numbers are much better than before, and in the 4000-4500 rpm range I broke through the 2 secs barrier the first time; 2.01 secs and a very quick 1.93 secs with WMI turned on. And not just one log, all logs are within a few hundreds of secs apart.

So I am confident there is potential in this manifold!

Next step, I am going to wrap it to see if some response can brought back. It should be quite doable with the manifold installed on the car.

tubular exhaust manifold: 4-1 vs 4-2-1

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