Kris H

I got some extremely bad, devastating news unless somebody corrects me...

First of all i came to the lab to see this:



Isn't there supposed to be some kind of a manifold template on the head while examinig the flow? I guess it makes a difference.. And probably a huge one..

As for the results, i can only hope the calculations are off big time since otherwise my head has been completely ruined by the machineshop which did the mods.. Intake flow:

Stock valve size.

L/d. Lift. CFM
.050 .073 70.6
.100 .146 131.8
.150 .219 178.7
.200 .291 210.4
.250 .364 236.5
.300 .437 257.5

Max lift on my cam is around .433. If it all is correct this actually puts my 16v head in the 8v teritorry and records as the worst flowing 944 16v head measured on this board..

333pg333

Your lift should be much higher Chris. Something looks incomplete with that testing. What cam is it? What is the stock cam lift for that head?

Kris H

If that makes a difference the numbers were corrected to 25" while most people here correct to 28".. That's one thing. The other - the guy told me it is not possible to go much further as he claimed 12.5mm to be the full possible travel of my valves.. However the measurements were taken by a guy who doesn't usually do it. The usual machine guy took a few days off lately due to daughter being ill or something.. Btw you can see detailed settings on the screenshots below:





Forgot to answer you:
I don't know the stock lift of a 944s. It's for sure less than my cam has, cause the machineshop grinded the head down about 5 mm if not more in order to clear the cam profile..

The cams are custom one-offs.. They were supposed to be prototypes based on the onwelded stock cams, the plan was to check if they do the job and produce new ones on their design while i do after season engine inspection..

Kris H

on lindsey's website, there is an altitude correction chart by superflow. According to it, I should multiply my numbers by 1.060 to get from 25" to 28" but it still gives very poor results (worth to mention their annotation, that the chart does not work like intended):

L/d. Lift. CFM
.050 .073 74.8
.100 .146 139.7
.150 .219 189.2
.200 .291 223.0
.250 .364 250.7
.300 .437 273.0

somebody told me lack of the manifold dummy takes about 10% of the flow. Even if i compensate that, i would get:

L/d. Lift. CFM
.050 .073 83.1
.100 .146 155.2
.150 .219 210.2
.200 .291 247.8
.250 .364 278.6
.300 .437 303.3

which is still worse than what MichaelMount measured as stock 944s head.. but it does not look as bad as i thought it did. However the angle at early lift on all the other measurements is much nicer, steeper.. mine seems to build up flow very slowly..





i just took a quick measure of my spare intake cam..
its max lift is more like .473 so I guess the guy miscalculated something...
I will have to ask them to go over it one more time...

ptuomov

Noticed some 928 flow figures there. This thread has some more for reference: https://rennlist.com/forums/928-foru...ughout-15.html , starting at post #218.

333pg333

So just to clarify, do the cams on the 4 valve heads have less lift than 2 valve heads?
The lift in my 2v race cam is .595 intake.

Also, as you've touched on. Virtually everyone else is measuring at .28" Mercury which will make a difference.

blown 944

A lot less patrick.

Those numbers do seem low to me.

Christoper, are you sure you measured that cam correctly? IIRC they only have around .350 lift. It's been a long time since I measured, but thats what comes to mind

refresh951

It is important to radius the entrance and eliminate sharp edges to ensure no turbulence at the mouth. It's common practice to stick a bead of plasticine around the edge of cylinder head ports. IIRC it can make quite a difference in the results (5-10%).

333pg333

Thanks Sid. iirc the stock 968 head flows somewhere near 350cfm.

Kris H

ptuomov - thanks. I am familiar with that thread.

Shawn - thanks, what you are saying backs what i've heard.. but it makes me sad that even if I add 11% to the measurements it's still a bit to low compared to other people here.

Sid, yes, I'm pretty sure i measured it correctly but I used most primitive method possible (didn't have proper caliper on hand so used a ruler and a nail..) I may be 1mm off but that's it. I can measure it properly today.

If you say .35 is stock lobe lift then it seems legit, as it's equal to about 9mm, my cam has approx. 12mm lift, and the machineshop grinded about 5mm of material from the lifter area to clear the lobes.



btw here's where i got the altitude correction table: http://www.lindseyracing.com/LR/Parts/TGHEADS.html can somebody explain why is it so, that their 10"->28" transition calculation is so far off from the actual 28" measurements?
after all it looks like it's provided by the flowbench manufacturer. one would expect it to be valid..

Another question that bugs me is - how did MMount and alexdgrt manage to measure 16v heads up to 0.6" lift? It seems impossible to go over .500 (if this is reachable since "my" guy says it ends at ~.49)...

Voith

I think that is achieved by grinding bottom end of lobes and using valve caps.

Kris H

I have measured my intake lobes:

lift 11.4mm (.45"),
"full" duration 117°, i guess it should be multiplied x2 to make it crank degrees, so -> 234°
duration @ 0.05" = 90°. Same thing -> 180°

At the moment I only have my spare intake camshaft in hand, so I can't measure LSA or overlap..

edit: angle correction

333pg333

Another thing to bear in mind is that flow benches can give different reads on different days due to ambient temps and electrical loads. Not sure quite by what variance but something to consider.

Kris H

I asked them to repeat the test today with some changes (my exhaust springs, hardware correction to 28", tests on specific absolute lift values of .05 .1 .2 .3 .4 .45 and .5 instead of .05 l/d ratio increments.. ) Still without inlet guide though.

I will get the results in a few hours. Doubt much will change, the only two factors different today are weather and altitude correction.. We'll see.

Voith

Why don't they use plasteline on intake ports?