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Porting Nissan's Sr20


oldeskewltoy

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I've seen quite a few threads in Rollaclub showing SR20 swaps. As I've done some porting on the SR20, and I have a new client whose SR20VE I'll begin porting next week (if all goes well on delivery to me).

 

 

 

Between now and then I'll drop a few photos, and some flowbench results from my "play" with a highport SR20DE

 

 

 

sr20deheadfwdrough_zps092539ba.jpg

sr20deheadstrippedcamsiderough_zps14720e60.jpgsr20deheadstrippedchambersiderough_zps0f3bdd8d.jpg

 

Not a lot of fwd heads around so "beggars"(me) couldn't be choosey.

 

 

 

For those who know something about SR20s... this is a 2.0 liter dohc 4 cylinder - fwd "highport" 1st gen SR20DE. It uses HLAs (hydraulic lash adjusters) as part of the valvetrain

 

 

Obviously the first thing to be done - was cleaning up the mess

 

normal_sr20de_head_stripped_chamber_side_clean.jpg

 

normal_sr20de_head_stripped_cam_side_clean.jpg

 

And for easier imagination the paths through the head have been marked out in Sharpie

 

normal_sr20_intake_and_exhaust_paths.jpg

 

The intake and exhaust bowls have been measured - nothing fancy so far...

 

Intake:

sr20_intake_seat_diameter_29_33.jpg

 

Exhaust:

sr20_exhaust_seat_diameter_24_47mm.jpg

 

 

 

Observations

 

 

Intake:

  • the bowl and seat work allow the valve to breath to its maximum, the intake valve head is 34mm. Typically the best compromise is somewhere between 85% and 90% of the valves diameter should equal the bowl/seat. The SR20 is pretty good straight away at 86%(29.2mm).
  • Short Radius - the short radius is the only place to easily increase the overall valves draw on the port. A un corrected short radius that interferes can have little or no air flow at lower lift points. This will hurt overall filling of the cylinder, and lower power

Exhaust:

  • The exhaust valve is 30mm, using the same formula (85%-90%) the seat/bowl should be at least 25.5mm(85%), but stock exhaust seat/bowls are only 24.7mm on average(82%).
  • The short radius was garbage interfering far worse in the exhaust port then it does in the intake.

 

more to come..... :D

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Initial impressions.... the casting itself is a bit rough, more deburring could be done to the castings, especially the top of the head which holds the cams and valvetrain. The chambers on the other hand appear to be well placed, with very little evidence of edges that would promote detonation (ping). The intake paths are bow legged shaped to allow for the HLA, the intake seat/bowl could use blending to better take advantage of the angled port, and mild short radius. The exhaust bowl/seat is far worse, significantly too small, the port provides little or no room for an adequate short radius, while the splitter, port roof, and narrowing walls are far too intrusive, and appear to truly restrict airflow.

 

 

 

Too begin with... as this head is one for discovery.... and as such I'll be performing different porting on 2 of the 4 cylinders, leaving 1 cylinder to use as a control. What do I mean when I say "control", I'll be using my flowbench to monitor any gains, or losses do to my porting work. I'll be leaving #2 cylinder and its ports completely untouched. I'm leaving #4 untouched for the time being, but may use it to "assemble" the knowledge I learn from porting #1 - within the lines, and #3 - outside the lines.

 

 

Initial impressions....

 

1) the casting itself is a bit rough' date=' more deburring could be done to the castings, especially the top of the head which holds the cams and valvetrain.

2) The chambers on the other hand appear to be well placed, with very little evidence of edges that would promote detonation (ping).

3) The intake paths are bow legged shaped to allow for the HLA, the intake seat/bowl could use blending to better take advantage of the angled port, and mild short radius.

4) The exhaust bowl/seat is far worse, significantly too small, the port provides little or no room for an adequate short radius, while the splitter, port roof, and narrowing walls are far too intrusive, and appear to truly restrict airflow.

 

[/quote']

 

1 - as I mentioned, the casting is a bit rough leaving many areas containing sharp edges. From my experience, often times poor casting areas lead to sludge build up because the oil and debris sits in these areas "cooking" into place as the miles go by. Making these areas less prone to holding the oil and debris, helps keep the engine cleaner, and easier to shed oil back into the oil pan. A second, and purely selfish purpose is with me constantly changing its position on my porting bench, the roughness really hurts my hands..... :cry:

 

2 - below is a view of the Chambers #3 and #4 , I've blacked out the valve openings to avoid distraction.... squint.gif

 

As you can note, other then doing a tiny bit of blending around the seats, putting a ~.020" radius on both "squish" pads, and polishing the chambers I've had to do very little.

 

sr20_chambers_3_polished_and_4_untouched_valves_black.jpg

 

 

As a comparison here is a small gif showing a 4AGE combustion chamber as it goes from stock, to finished

 

flg3z5.jpg

 

 

 

what on earth is this????? And what does it have to do with porting an SR20???

 

SR20_jig_in_lexan.jpg

 

more to come.... :D

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what on earth is this????? And what does it have to do with porting an SR20???

SR20_jig_in_lexan.jpg

 

 

 

No guesses... really? Not even a shot in the dark? :eatlead:

 

 

How about a few hints.......

 

The lexan sheet you see is just a template....' date=' the final version will be in steel

 

[img']http://ost.ebeans.ch/albums/userpics/10005/normal_SR20_valve_setting_plate_lexan_and_steel.jpg[/img]

 

Does that make it easier??? How about if I add that the "14 1/2" you see written on the steel plate refers to degrees, does that help at all???

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Making a template to machine out valve guides for thicker valves?

 

first..... thank you for at least playing along.... :party:

 

 

The plate is not for overboring the valve guides.

 

 

"from another forum"

OK. Looks like it's used to hold the valves open? So you can perform the flow test right?

 

bingo... it is the tool I'll be using to set the valve openings....

 

Here is a sample of it in use... the use is to show you the viewers that I can set this tool at any height... note the tool on the bottom of the photo... and note the valves @ the top of the photo. note one side is set much further then the other. That shows that I can adjust, and set each valve anywhere I want during flowbench testing

 

SR20_valve_setting_plate_steel_holding_one_valve_open_further_then_the_other.jpg

 

 

 

Now being able to set the valves is important... just as important is knowing exactly how much... so I plan for the plate to accept a dial guage to read the amount of lift

 

SR20_valve_setting_plate_steel_nearly_finished_just_needs_wedges_for_gauge1.jpg

 

 

and the finished tool......

 

sr20_valve_setting_tool_finished.jpg

 

The dial gauge will "read" from the edge of the spring retainer

 

 

and a view mounted to the head....

 

normal_sr20_valve_setting_tool_finished3.jpg

 

 

This tool is imperative in correctly reading the flow through the head. It allows me a VERY reliable - REPEATABLE method of measuring the valve lifts so that I don't "cheat".

 

How can you cheat? Simple really, just be off by .001" or more and the reliability goes out the window... a PERFECT, ACCURATE valve setting tool is required to provide reliable figures

 

 

 

 

Now that the valve setting tool is finished, its time to re-configure my flowbench to measure the SR20 head. Last Summer(2014) I had a new bore adapter "machined" to 86mm so I could begin to check cylinder heads that use that bore... (3SG, 1/2JZ, SR20, FA20/4U-GSE, and a few others....)

 

86mmadapter_zps2a48e735.jpg

 

I will then place an SR20 headgasket on the bench to determine where the alignment dowels will be drilled into the flowbench table to properly align the head over the 86mm bore adapter.

 

 

 

Here is the "view" the flowbench will see...

 

86mm_bore_over_chamber.jpg

 

 

 

 

More to come....... :D

Edited by oldeskewltoy
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A few different views of the SR20DE port passages....

 

normal_sr20_intake_and_exhaust_paths.jpg

 

normal_SR20_cut_away_head_showing_intake_and_exhaust_paths.jpg

 

 

Now compare those views with a few others.....

 

4af_formula_one_sr20.jpg

 

Same similarities... while there are other differences....

 

Two of the views above seems to show the SR20 intake ports to have a similar shape to a Formula One design :thumbup but hold on... the F1 design doesn't have an HLA to avoid :mad:, the top view showing the port layout is our issue here. The port opening is marginally 50mm (do to costs, the port opening varies at the seam from 49 to 50),

normal_sr20__1_intake_port_view.jpg

 

the intake valves are less than 9mm apart from each other,

sr20_gap_between_valves.jpg

 

and the HLA makes the port splitter somewhere close to 23-24mm at its widest point.... and so you get a bow legged intake port.....

 

 

More can be done here ... mostly because this is a production automobile head, and as such typically there is enough casting material available to better shape, not only the intake port... but often the entire head.

 

 

 

 

 

The SR20DE has a 34.25mm intake valve

 

SR20_intake_valve_diameter_34_25mm.jpg

 

 

Our valve seat ID measures...

 

sr20_intake_seat_diameter_29_33.jpg

 

doing the math... the seat bore is almost 86% of the valves diameter. This percentage is very good for a stock set up, typically I try to get the bowl to 85%-90% of the valves diameter to equal the seats bore. So since the seat is in the range, only minimal work will be performed on the seat.

 

As I begin to work cyl #1(staying within the lines). The very first things I look at is the seat and bowl alignment. This SR20 is far better than a few of the 4AG heads I've worked, SOOOO the focus on the SR20 intake seat/bowl is the short radius....

 

 

 

#1 cylinder - Note the protrusion on the bowl on the right(#1 valve), it doesn't have to be a lot, that protrusion you see makes the low lift airflow stagnant because at the valve the air/fuel charge has to navigate a sharp angle. The #2 seat/bowl shows the initial reshaping of the short radius.

 

 

SR20__1_intake_short_radius_close_view.jpg

 

 

 

SR20__1_intake_short_radius_showing_different_port_roof_radius.jpg

A bit more work in this view, the #2 bowl is showing mild re-shaping to allow more volume. I'm careful to port areas that will "straighten" the angles, or in this case do my best to minimize the bow legged effect. With that in mind note I worked the outside of #2 bowl(far left of bowl on left). This minimizes the angle, that the air/fuel charge has to navigate. A similar, yet not quite as significant amount of material was removed from the inside(right) of the bowl on the left.

 

A slightly different perspective... showing the overall shape of the bowl and seat transition - the key areas to note in this view are the 3 and 9 positions inside each bowl

 

SR20__1_seats_and_bowls_showing_work.jpg

 

 

Lets get back to our control... #2 intake bowls, and seats

 

sr20_2nd_chamber_intake_seats-short_radius_number.jpg

 

So what I've done is increased the area around the bowl for the opening valve to draw upon.

 

 

 

More to come........ :D

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Do you have a moveable pitot so you can measure flow velocity at different points around the valve edge??

 

How much worse is it around 'A', right beside the bore??

 

Yes..... BUT I can't measure inside the flowbench sampling cylinder. The head is sealed down against the bench. I can measure inside the port.

 

(I guess I could make a jig so I could either blow through the intake port, or draw through the exhaust port and then have the cylinder affixed to the head and THEN measure around the valve head.....)

 

BUT if you are asking if the intake valves are too close "A" (shrouded) to the cylinder wall for a good draw.... they might be(I doubt it), but there are far more flaws to address that are far easier to quantify/fix before I worry about valve shrouding.

 

 

 

I needed to make another tool....... very simple caliper

 

homemade_measuring_caliper_2_panel.jpg

 

 

A stock intake port is approximately 27mm (+ or - 1mm) and 100mm long @ that diameter

 

sr20_measuring_port_ID_-_26_95-27mm.jpg

 

 

A stock intake splitter is approximately 24.5(+ or - .50mm) wide....

 

sr20_measuring_the_width_of_splitter.jpg

 

 

 

 

So... how much "extra" material is around the HLA?

 

 

Maybe the first question should be What is an HLA? HLA = Hydralic Lash Adjuster - for simplicity think of this as your shims for adjusting valves. An HLA fills with oil and acts as a fulcrum for a "Y" shaped rocker. The HLA fills and removes the excess gap between the rocker and the cam.

 

middle example is stock set up

 

ep098_pivot_02.gif

 

 

 

The HLA is 17 mm in diameter, making the HLA hole 17.0something in diameter, but surely under 17.1mm... so subtracting 17.1 from 24.5, that leaves us about 7.3mm of unnecessary splitter width. What we don't know is how evenly set the HLA bore is in relation to the two bow-legged intake ports.

 

Exact HLA placement inside the splitter is as yet not fully determined by me, or a photo or some other evidence I've been able to find. The cut away shown a number of posts above doesn't include the HLA :( The view below kind of shows it, and yet it isn't specific. What you can tell in the view below is the HLA does interfere on the intake side, while it appears to not be an issue on the exhaust side.

 

110298_10mg.jpg

 

 

So, by simple mathematics there is SOME room along the splitter for removing some material to help "straighten" the port, and remove some of the bow-leg the ports follow. This will help, but my little home made calipers found another problem....

 

no guessing on this one.... we know the valve is 34mm, the bowl/seat @ 29mm, and now....

 

A stock intake port is approximately 27mm (+ or - 1mmmm) and 100mm long @ that diameter

 

Think about that for a moment... the port = the throat for nearly 4" of length. The "throat" in an intake port is the narrowest point inside the port' date=' it is designed to help speed up airflow a short distance from the valve. This narrowing also limits reversion(the air/fuel charge "bouncing" off the closing valve and moving back up the manifold). Often times, especially in performance engines, the throat is preceded by a gradually tapering section that goes out to the flange, and it either connects to an intake plenum, or an ITB. The tapering section is similar in principle to a velocity stack. The SR20, having a "throat" 4" long only chokes down the air volume by having a set diameter through this part instead of a tapered diameter. So if, along with straightening out the air passage we can add a taper to each port, in theory, we should be able to see noticeable gains in volume, with minimal loss in velocity.

 

 

So lets move on to what all this means.... Intake port - 4 panel as it transitions from stock to "within the lines" = inside "stock" openings - note I have not increased the opening size, I've worked within the original casting, and at no time have worked beyond that. The outermost green dotted crescent highlights that the area just inside the ports edge got the majority of the work, and not the edge itself

 

 

[img']http://ost.ebeans.ch/albums/userpics/10005/sr20__1_intake_port_4_panel_1k_pixel_tall.jpg[/img]

 

Look carefully... in the 2nd view down I diagram what I'm doing. Note the orange dotted line, it shows where I worked the splitter at its widest point. It shows I changed the shape, that I removed a bit more material from the roof and floor of the splitter while taken only a minimal amount from the splitter wall. Remember our measurement of 24,4mm, that is at the narrowest point at the center of the splitter, but do to the extreme arc of the port, the splitter at the roof and floor are closer to 40mm, and with care offer up a LOT of material that can be removed if done carefully... as shown by the time you get to the bottom view.

 

 

 

The other green dotted line/arc show additional areas of material removal. They also begin to highlight the narrowing, and shaping of the splitters leading edge.

 

 

So... why did I leave a large section of the port walls untouched?

 

 

 

A unique view... 3 slightly different angles on my SR20 port work. Cylinder #2, my control, on the left, cylinder #1(within the lines) on the right...

 

SR20_comparing_intake_ports_of_cyl_1_and_2_3_panel_showing_3_views_inside_the_intake_port_1001wide.jpg

 

... these views help to show how I've worked the top and bottom of the splitter, it also shows how I've shaped the bowls to blend into the seats. The top view shows the splitter roof, the center view shows the center work, and the bottom has more of a focus on the splitter floor. Also the short radius blending is plainly visible.

 

 

This photo also shows I left a large portion of the port walls untouched... so I ask again... Why did I leave sections of the port wall untouched?

 

 

 

 

 

more to come..... :D

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The whole purpose of this head is to experiment with porting ideas, and then putting those ideas to the test - using a flowbench. With that said, a few things besides the head had to be arraigned - for one setting up and re-calibrating the flowbench. Up to now I've either had 82mm, or 84mm cylinder sleeves, this was the first time with the 86mm sleeve. Besides the new sleeve, the bench surface had to be prepared to "take" an SR20 head.

 

I will then place an SR20 headgasket on the bench to determine where the alignment dowels will be drilled into the flowbench table to properly align the head over the 86mm bore adapter.

 

 

 

I need a jig to keep a hand drill square so I can drill the appropriate holes........

 

said jig

image_7094.jpg

 

 

 

speaking about drilling the appropriate holes....... |blink| .... you'd think Nissan would have stuck with metric....

 

sr20_15-32_drill_headbolt_bore_size.jpg

 

 

have you ever tried to find a 15/32" dowel??? Good luck!!! I eventually found a company who would make me 1000... at the cost of $195.00 :no:

 

 

 

So... its time to see if I can make something that will work... 1/2" thick wall aluminum tubing...

 

sr20_making_alignment_dowels.jpg

 

 

add an inline cut.... and viola... 15/32" dowel....

 

sr20_making_alignment_dowels3.jpg

 

 

now that I have the dowel solved... lets go to the bench.....

 

 

SR20_headgasket_layout_on_flowbench.gif

 

**IF** I were to try and use a "conventional" layout, the holes from the Toyota heads would interfere with the new holes needed for the 15/32" dowels... so a slight rotation of the layout provides me an unmolested area to drill to receive the dowels.

 

 

So with the new adapter, and a new mounting solution set up, I re-calibrate the bench for the 86mm adapter, and so now that the bench is ready.......

 

 

 

More to come...... :D

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While I've been writing this thread you have seen me use "within the lines" and "outside the lines" a few times... Let me try to show you what I mean.....

 

Intake: stock - "within the lines" - "outside the lines"

 

sr20_intake_samples_stock_inside_and_outside_the_lines_annoted.jpg

 

 

Exhaust: stock - "within" - "outside"

 

sr20_exhaust_3_panel.jpg

 

Both intake, and exhaust "outside the lines" ports are still in the roughing out stage.... but you should still get the idea.

 

 

"Outside the lines" began as an instinct based on the knowledge I had gained over the years working the Toyota heads. My instincts were to prove pretty good, I just wasn't bold enough......... :evil:

 

The last generation of the SR20 was a variable cam timing version, much like the 3SG went through a few versions ending with the BEAMS, the SR20 had a few revisions, ending with the VE.

 

The VE was the only SR20 head to have a modified exhaust port outlet. All previous SR20 heads use the outlet you see in the above gasket. The VE uses a different gasket

 

normal_SR20VE_exhaust_gasket.jpg

 

 

Not only is the new gasket taller roofed, but they add a bit of girth as well..... all while retaining the same floor (gasket's lower edge)

 

VE_gasket.gif

 

 

 

 

With a taller roof, I "push" the exhaust port and viola........

 

exhaust_port__3_out_of_the_lines.gif

 

here is a 1st gen SR20 head with an exhaust port superior to even the SR20VE :dancetall:

 

 

 

more to come...... with numbers, I promise...... :D

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Part of the plan in getting this on the flowbench is to make light seat pressure springs(>15#s) to keep the tool from flexing, and just not to over tax the tool by using regular valve springs... I ran out to the hardware store... and pick up 4 cheap compression type springs that have almost the same OD as the Nissan valve spring...... but require much lighter force to operate

 

test_spring_before_cut_to_size.jpg

 

but they are a bit too long... so a cut in about the right place and we are good to go

 

test_spring_cut_to_size.jpg

 

 

 

so I can assemble the head with the test springs.....

 

 

set_for_flow_bench_testing_cyl_2_-_the_control_with_arrows.jpg

 

 

Here is how the dial indicator follows the valve

 

dial_gauge_resting_on_retainer_1.jpg

 

dial_gauge_resting_on_retainer_2.jpg

 

Head is set on the flowbench, #2 intake is being tested in this photo, this is our control - untouched

 

sr20_head_on_flowbench_smaller.jpg

 

 

 

The numbers for #2 intake (the control) are

inches - CFM

.050" - 44.5

.100" - 88.1

.150" - 122.7

.200" - 154.5

.250" - 178.2

.300" - 189.7

.350" - 198.7

.400" - 203.8

.450" - 207.7

 

The numbers for #1 intake (porting within the lines) are

.050" - 44.2

.100" - 88.7

.150" - 125.6

.200" - 158.9

.250" - 181.6

.300" - 197.2

.350" - 206.2

.400" - 212.5

.450" - 217.5

 

Finally the numbers for #3 intake (porting outside the lines) are

.050" - 44.1

.100" - 87.8

.150" - 124.5

.200" - 158.9

.250" - 183.3

.300" - 202.1

.350" - 214.7

.400" - 223.3

.450" - 228.3

 

 

 

 

 

more to come..... :D

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