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Thread: OST-037: Under Pressure

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2016-01-21 16:57:27
Originally Posted by oldeskewltoy

Took a moment away from the head to think about getting this on the bench.

something not often seen... call it piston's eye view......

above is my 86mm flow adapter laid over cyl #1....

more to come......
2016-01-21 23:59:30
So all the chamber and bowl blending is finished, next I set each valve to each seat, numbered them, and then proceeded to measure the chamber volumes.

So just a quick recap... I've gently reshaped, the chambers, and had the valve job performed, setting the valve depths. With the new valves....

The chamber volume has risen....

somewhere between .8cc and .9cc... and that includes the added volume from the new valves

Chamber volume equity is within 0.25%

Now that we have a volume we can determine how much of a cut we want....

So whom are the math wizards following this??? As we can see from the flowbench adapter the chamber is 86mm across except @ each squish pad. I need 3 volumes.... Based on an 86mm wide circle, how much volume is a .01mm cut, and a .025mm cut, and how much is .038mm cut.... need my sum in CC's
2016-01-22 02:38:37



in CCs
2016-01-22 17:27:35
Originally Posted by zeneffect



in CCs

so adjusting for squish pads...
.01mm = .2cc
.025mm = .5cc (round from .52)
.038mm = .8cc

hmmmmmm, something's not right..... .01mm = 0.0003937008, rounding that is .0004, or 4 ten thousandths. This is imcorrect, a typical "clean up cut" (minimal) is about .003" - .004", thousandths, not ten thousandths. I've used incorrect variables... by a factor of 10

Part of why I record all my work in forums like this is to catch mistakes BEFORE they happen! Now in this case the issue isn't actually how much material is removed... but the resulting volumes. So... the actual variables are .1mm, .25mm, and .38mm. Assuming since it is a factor of 10, that are volumes also get bumped. So our volume will change but not by tenths of a cc, but full cc.

2cc for a .1mm cut (.004")
5cc for a .25mm cut(.010" - rounded from .0098")
8cc for a .38mm cut(.015" - rounded from .0149")

So a clean up cut will take about 2cc giving us a 39.4cc chamber. Going back to our compression calculator... and adjust the 41.4 down to 39.4 we have a current static CR of 10.6.

more to come.....
2016-01-27 22:37:21
Originally Posted by oldeskewltoy

small bit of explanation.... the above gif was taken from a Brit TV show called, "Are You Being Served", comedy about department store employees. The gif is from an episode where that mannequin repeats, "I like it, I like it...."

So my comedy sucks.... or maybe being kind... it is esoteric....

but my head work is why I'm here... NOT my comedy! Below, this clients SR20VE came back from the machine shop wearing its .004" re-surface

Originally Posted by oldeskewltoy

Finally.... I measured the heads thickness....

... although 137.02 is confirmed(5.394")

So now that she has been surfaced, I'm preparing to flow the head.... test springs to the right....

more to come.....
2016-01-27 23:02:31
Very nice, excited to see the results of the flow test

Sent from my SM-N900V using Tapatalk
2016-01-28 01:48:00
Hmmmmm, flowbench numbers are all over the place.....

alleged stock SR20VE #'s



Neither is that close to the other..... Any other SR20VE flowbench results????
2016-01-28 01:53:57

I'd guess 8 cfm from graph to graph by eyeballing it... then again I'm on a phone so could be way off. The portflow numbers were pulled from MotoIQ and we're of Mike Kojima's head. I believe they went +1mm on the exhaust side which is represented by the modified graph. just fyi so it's not taken as a baseline or comparison as its not really apples to apples.

Original article found here.

These curves look similar to #2
Last edited by zeneffect on 2016-01-28 at 02-28-01.
2016-01-28 02:43:25
Lift. 0.100 0.200 0.300 0.400 0.500
Inlet CFM Stock 85.2 158.6 219.0 252.8 261.7


Lift. 0.100 0.200 0.300 0.400 0.500
Exh. CFMStock 85.5 146.2 170.0 175.0 178.0

From our friends down under.
2016-01-28 18:09:52

MotoIQ's results align well enough(2% or less difference) with the results posted by 2_liter_turbo from his post http://www.sr20-forum.com/all-motor/75696-de-head-package-budget-infotainement-2.html#post1001166. The Aussie #s, and the bench flowchart, "one" I posted above, both seem off.

Not using them as a baseline.... but would like real/honest numbers to compare too(see if we are in the "ballpark"), since we don't have before #s on this head..... When I flowed the Toyota 7MG head my numbers came up pretty close to others who previously posted their #s.
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