Inlet Manifold flowtests

[jogi730]

I am gathering as much information as possible to see why my engine was suffering so much lag. I strongly suspect one of the causes to be the Inlet Manifold, so I had it sent to be flow tested by an independant company. For comparison I got hold of a manifold I know to be of 'good design'.
There are big differences in the figures attained, but not being technically minded I was hoping some of you on here could explain how the differences would impact on performance.
The results are in the link as I do not know how to place them directly into this thread.
Many thanks
Chris

[Acidburn]

Notes:
Test purpose: Intake manifold comparison test using Flowbench.
Flowbench calibration was done before and after tests with scientifically calibrated
calibration plates from two different manufacturers.
Flowbench desing is orifice type and room temperature did not change during tests, so
all measurements is within 1% error marginal.
Bare head: Test was made with ported Audi S2 for which these intake manifolds are
made for. Valve sizes are stock and porting work can be considered as typical porting
from professional head porter. Cylinder head was flowed with perfect venturi at the
intake runner throath to minimize flow loss.
Pro-mo: Test was made with intake manifold from Pro-Mo Racing Service using typical
maximum lift values of engine camshafts. This indicates maximum possible
horsepower from engine with perfect parts and is a good way to compare intake
manifold efficiency.
Copy: Test was made similarly to Pro-Mo test, but using intake manifold "copied" from
Pro-Mo Racing Service desing. Flowbench testing indicates less power potential when
using this type of intake manifold. Power loss depends of used
camshaft lift, engine RPM, boost pressure and engine volymetric efficiency.

Is that any help mate?

[jogi730]

Wish I knew how you did that? That's great - thanks Pete
Chris

[Rusty]

I'm at a slight loss as to what those results are for, as they seem to be for the head rather than inlet... or is it combined?

[Jamo]

Combinied it's showing the total flow via the inlet manifold into the head at valve level.

Basically from what I can tell the old manifold was restrictive at a given valve lift.

[Rusty]

So Yogi's car is runnin manifold number 2? That's quite a lot more restrictive.

[4WheelDrifter]

It looks to me like the cylinder head ports were subjected to a vacuum (28 inches of water) as a bare head, with a Pro-mo inlet manifold, then Jogi's 'custom' inlet manifold, and the differences in flow (cubic feet per minute) were observed at 10mm and 12mm of valve lift.

It seems Jogi's IM didn't flow quite as well as the Pro-mo one. It would've been interesting to see how a stock IM would perform as a comparison, to show if there was any gain in running the IM Jogi did. I would assume that one of Repo's manifolds would flow well anyway.

[Smiley]

the numbers of the ADU/3B/AAN IM would be interesting here.
To me, a second point is that this numbers are measured with a constant valve lift only. The numbers per cylinder would be of interest, as the AAN IM is mentioned to be 'preferring' some cylinders. This has something to do with these complicated thermodynamics and the waves of air formed by the frequent valve operation. Maybe someone is around to give some more light on this magic..

[jogi730]

Interestingly enough, a flowtest was carried out on the standard AAN IM. The flow on that was some 5-7% better than the special custom made one. I wonder how this can be explained?

[jogi730]

http://www.s2forum.com/photoplog/images/714/1_IM_comparison.jpg

[Jamo]

Interestingly enough, a flowtest was carried out on the standard AAN IM. The flow on that was some 5-7% better than the special custom made one. I wonder how this can be explained?

Side on inlet between the 5 cyclinders.

Remember these test are not definitive about overall performance.

[repo]

The reason these were tested was that when I examined the special intake Chris had, I told him the design is bad just by looking it.

As it was originally built to enhance the spoolup, I doubted the design, and Chris wanted me to have the intakes tested.

Tests prove what I claimed, the design is restrictive, and that's what counted. Not the actual numbers.

Also, there is no reason to test other runners, as all the runners in Chris' old IM had the same basic flaw. Missing trumpets at the end of each runner. Test was carried out by measuring the same cylinder over and over again.

Not even mentioning how much extra work that would have been for the tester, to redo the same procedure four times per each cylinder, when the idea was only to prove that there is something desperately wrong in the upgrade intake. So, it seems to cut the flow some 5% at it's worst over stock one - the actual piece it's made of, and we all know, the original idea was not to reduce the intake flow with the modification, that's been carried out to this intake.

[jogi730]

Remember these test are not definitive about overall performance.

My understanding of these things is quite limited. But a friend did explain this to me as best he could. Very basically, the principle is the more flow you get, the more boost you can run early on. Even 0.1 bar more boost at 2000rpm is quite significant as this all becomes accumulative the further up the rev range you go.
More boost means more responsive engine - or less lag maybe?

Now if this is a starting point, any tuning garage that designs and builds an intake manifold must be aiming to achieve more flow than a the original manifold, especially if reducing lag is the goal? Or am I missing something?
Cheers
Chris

[DJones]

My understanding of these things is quite limited. But a friend did explain this to me as best he could. Very basically, the principle is the more flow you get, the more boost you can run early on. Even 0.1 bar more boost at 2000rpm is quite significant as this all becomes accumulative the further up the rev range you go.
More boost means more responsive engine - or less lag maybe?

Now if this is a starting point, any tuning garage that designs and builds an intake manifold must be aiming to achieve more flow than a the original manifold, especially if reducing lag is the goal? Or am I missing something?
Cheers
Chris

Chris,

I think you are absolutely right. Indeed if the inlet tract is restrictive it can in its self make (a modern) turbo surge.

Darren.

[4WheelDrifter]

Interestingly enough, a flowtest was carried out on the standard AAN IM. The flow on that was some 5-7% better than the special custom made one. I wonder how this can be explained?

Now that is interesting.
The 'custom' IM looked a poor design, but the numbers prove it. Why would anyone want to have an IM that flows worse than stock? Repo's IM results provide a good example of what can be done.