Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

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jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Tue Aug 22, 2017 12:49 am

One of my objectives when starting this s/c project was to try and optimise the hardware
for best performance. By this I mean make the system as efficient as possible by reducing
the resistance to flow of the intake and exhaust. In particular, I wanted to improve the
intake ducting as this is a known restriction on the OEM 4AGZE system.

So I used 2-1/2" OD (60mm ID) tubes with mandrel bends and a 60mm throttle. To get the
car running I hooked up the OEM AE86 intake ducting and filter, as by a pure fluke, the
open end of the throttle ended up in more or less the same position as the original AE86
throttle. Looked great... just like a factory install :)

Image

Since I have been running the car I have been curious as to why I have not been able to
reach the boost numbers that were predicted by the s/c data sheets. There are a number
of factors that can affect the boost produced, and I have been looking at them to see if
I can get closer to the predicted numbers before changing the the next size pulley. Right
now I am looking at the restriction caused by the OEM intake and filter.

Image

I have got hold of a cheap ebay digital differential pressure gauge that reads up to 2psi
max above or below atmospheric. I have hooked this up to a tapping on the throttle body
so that I can read the pressure drop across the intake and filter, and hope to get readings
tomorrow. With a positive displacement s/c the pressure ratio across the s/c is fixed at
any given rpm, and any restriction on the intake side means a roughly equivalent loss of
boost on the discharge side.

It was always my intention to make a low restriction intake/filter setup, and I have the
pieces ready to go... only have to finish making the brackets to hold the filter steady.

Image

I have used 3" tubing and a quality filter, so I am hoping to recover at least 1psi of lost
(= free) boost once it is installed. But I'll post the results no matter how it turns out :)

EDIT: Experiment was a fail as it turns out the spigot on the throttle body that I was
using to measure vaccum was the evap connection. So it was seeing engine vacuum as
soon as the throttle began to open and therefore no use for measuring intake restriction.
There will be a delay while I drill and tap the TB for a new barb.

Cheers... jondee86
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jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Thu Aug 24, 2017 5:29 pm

Tested the new intake today and it made a BIG difference to how the engine
pulled above 4000rpm... WOOT !!!! Be like... twinscrew kicked in YO :shock: :D 8-)

Just gotta put the OEM stuff back on and test that. Hope to do that tomorrow and
then I'll post the results.

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jinx » Fri Aug 25, 2017 4:44 am

read a few testimonials of definite gains from increasing piping diameter around the stock sc12
the vast majority never bothered to. It's the little details, eh....
Would b interesting to c ur final results. Good job (as usual)

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Fri Aug 25, 2017 5:02 pm

Results are in and look like this....

Intake Pressure Drop
Apexi Intake; 1.43kPa @ 7490rpm
OEM System: 5.91kPa @ 7480rpm

Engine Manifold Pressure
Apexi Intake: 143.3kPa @ 7490rpm
OEM System: 136.4kPa @ 7480rpm

So by reducing the intake pressure drop by 4.48kPa (0.65psi) I gained 6.9kPa or
exactly 1.0psi of boost
:) This shows that the OEM system is actually quite efficient
and acceptable for stock N.A engines. I'm pushing a bit more air thru the engine so
N.A. the pressure drop would be more like 0.5psi max. A fresh filter element would
be even less !!

The gain from the freer-flowing intake will be progressively greater as I raise the
boost level (and intake airflow), so I am more than happy with these results. When
working with small capacity engines like the 4AGE, every little bit counts !!!

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Wed Dec 06, 2017 1:15 am

Been chipping away at this project, driving the car whenever I get the chance and
getting a few things done that need to be done before the car goes to scrutineering.
Catch can is mandatory for any track events so grabbed a cheap ebay can and found
a place for it right under the air filter :D

Image

Don't think that will be a problem as I have run the engine and checked the cam cover
vent. Feels like there is a lot of air coming out but it is just pulsations due to pumping
action of the pistons. And no sign of any oil in the vent tube. Made a bend out of a piece
of tube from an old outdoor VHF TV aerial and epoxied it into the outlet. Easy call to
make when I saw the price of 12AN fittings !!! Just have to find a piece of black hose
to hook it up.

Also got the small (75MM dia) pulley installed on the supercharger now, so starting to
work on a tune that I can take to the dyno. Running 50:50 meth and water spray to
keep manifold inlet temp under control. Typically runs around 70degC and the spray
does a reasonable job of controlling the temp rise when running at WOT. All in all I am
very happy with the way this is comng together :)

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby aukword1 » Wed Dec 06, 2017 3:25 pm

Glad you are happy with the project thus far. It is looking great btw. I'd be interested to see what the dyno numbers are with a smaller SC pulley. Also, you can probably run a larger crank pulley to add even more boost like the 4agze guys do. Anyhow good luck with it all!

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Wed Dec 06, 2017 6:36 pm

aukword1 wrote:Glad you are happy with the project thus far. It is looking great btw.

Thanks :) It makes enough power now to be a fun ride, and that is really what this build
is all about. It will go on the dyno to get the timing set properly, and that should help get
the power up a bit, and I'll be happy with whatever it makes once it's tuned.

Not planning on spinning the s/c any faster. The only future mod that I might look at is
getting a set of cams. I'll need to see where peak torque is sitting, and then decide if I want
to push the peak any higher. That will make more power, but if it hurts bottom end then
I don't see any point. The best thing about the engine right now is the instant response
when you get on the gas, and I don't want to lose any of that :mrgreen:

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby oldeskewltoy » Thu Dec 07, 2017 9:48 am

jondee86 wrote:[ The best thing about the engine right now is the instant response
when you get on the gas, and I don't want to lose any of that :mrgreen:

Cheers... jondee86


I'd be interested to see your dyno print out.... The 4AGZE I built for a client last year made over 175#/ft @ around 2000 rpm, with a peak torque of 210#/ft @ 4200, while retaining the SC12....
OST Cyl head porting, - viewtopic.php?f=22&t=300

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jinx » Thu Dec 07, 2017 3:31 pm

oldeskool, that 1.6 SC12 deserve a build thread. Got a link ?
Sounds strong. Chasis dyno? What cams? porting? boost? SC plumbing mods ?
Any little tidbits may improve this twin screw torque even more

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Thu Dec 07, 2017 5:43 pm

oldeskewltoy wrote:... peak torque of 210#/ft @ 4200, while retaining the SC12....

Yusss.... does look like good numbers. I don't think I will anywhere near that as what
you get out pretty much depends on how much you can squeeze into the cylinders. And
the SC12 runs 1.2 litres/rpm whereas the S5-210 runs 0.94 litres/rpm. So 27% more
displacement, and depending on how fast it is spinning, the SC12 could be making
17-18psi of boost.

I'm not planning on running the s/c any faster than whatever it does with the 75mm
dia pulley and an 8000rpm (for the dyno only) redline. Normally I will be running with
an 7800rpm limit just for reliability. Pretty sure the torque curve rolls over around
5000rpm, but it's very flat and gentle so power will keep going up until redline.

Yeah... some pics of the finished installation would be nice oldeskewltoy ;)

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby oldeskewltoy » Fri Dec 08, 2017 6:28 am

jinx wrote:oldeskool, that 1.6 SC12 deserve a build thread. Got a link ?
Sounds strong. Chasis dyno? What cams? porting? boost? SC plumbing mods ?
Any little tidbits may improve this twin screw torque even more


:arrow: viewtopic.php?f=13&t=19447
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Fri Dec 08, 2017 5:01 pm

oldeskewltoy wrote:Image

Been looking at this and wondering about the shape of the torque curve ? I would
have expected something more like this one...

Image

With the work and parts that you put into the engine, I would have expected that
it would keep making power for a bit longer, and not roll over so hard ? Maybe the
SC12 just hit its limit early due to the higher flow capacity of the head ?

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jinx » Fri Dec 08, 2017 5:48 pm

unless I'm reading it wrong? ....that thing looks like it's making an unusal amount of tq
thats what accompany's an unusal amount of effort/detail
@6500rpm torque is still ~155 ft-lbs.
It does appear that the SC12 makes the best out of the improved midrange VE, than falls behind a bit in the hi rpms
...as should be expected.
Such a street car should be a blast.. especially geared right
Don't recall what cams, spec'd in that sc12 thread. May boost the tq here as well

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby oldeskewltoy » Mon Dec 11, 2017 7:53 am

That engine is using an SC12! The entire build was predicated on the SC12's retention. Now to be "fair", this is running a double size intercooler, and it does have aftermarket management, and an O/S pulley, but the SC12 was retained... and yes the cams durations would indicate the ability to twist another 2000 rpm, but the SC12 is out of its league by this point.

The head work around the intake valves was based on boosting port velocity, and in fact although using O/S valves the peak flow on this head @ .350" lift was only halfway between a ported stock valved head, and the oversize valve head that followed. On the exhaust side the ports grew to 34mm, with all the tricks I know.
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

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jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Tue Dec 12, 2017 12:59 am

If the guy is determined to stay with an OEM s/c he would benefit from hunting
down a SC14 and adapting it to his engine. But still a basic Roots design and there
are a lot of better designs around now. The law of diminishing returns bites pretty
hard when you start pushing the SC12 way past its intended operating envelope.

Still. as said above, with the correct gears and short shifting, anything that hits
like that off the bottom should be a hoot to drive :)

Cheers... jondee86
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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jinx » Tue Dec 12, 2017 3:24 am

maybe on paper the roots is "bad", but i for one can't c it
Several full street 1.6 SC12 AE86s go 13.9-13.7s with only bolt ons. No porting, oe cams
Incredible from a 'torquey' puny 1.6 imo. Excellent platform to build on I'd think
Add a 7A bottom end, head work, aftermarket cams diaed in, inj, SC plumbing bottlenecks removed, etc...
I'd love to build one (something like Rollapats') to maximize potential

1.8 street miata gone 12.7 with a scrappy junkyard setup, M90... spinning on street tires!
another build 1.8 MP62 20psi stunned turbo miata owners who drove it.
Said it pulled like a V8, had unreal torque and sounded like a giant superbike. Nothing any turbo 1.8 did
dunno if his build thread still up, but car mentioned/seen here;
http://www.fiero.nl/forum/Archives/Arch ... 85816.html

not a roots vs.... comment, but only to highlight its proven awesome capability, when explored
Sure I'd think the twinscrew is even "better".... but by how much ? I'm wondering. :?
Didn't Mr2swift do a lot of twinscrew testing and dynoing. I gotta search the info. 300+hp at some point iirc??

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Re: Gonna start a build and see where it goes ===> TWINSCREW !!! :-p

Postby jondee86 » Tue Dec 12, 2017 12:40 pm

jinx wrote:maybe on paper the roots is "bad", but i for one can't c it

Compressed air is still compressed air no matter what kind of s/c you use. The only
difference is how much noise, power and heat it takes to compress the air. A basic
two-lobe Roots blower still gets the job done just fine, and is the father of all
"positive displacement" vehicle superchargers. Recent developments have added
lobes and twisted them to reduce noise and pulsation and improve efficiency.

From a packaging point of view, it is important to match the s/c to its intended
application. Toyota matched the SC12 to the 4AGE when they designed the 4AGZE
and in stock configuration it worked as intended. The only thing that makes is "bad"
is when it is pushed way past its design operating conditions. It is then no longer
matched to the application.

In the case of the OST SC12 build the engine is crying out for a larger capacity s/c.
Put a correctly sized Eaton on that engine and it should make 300 plus hp :)

Cheers... jondee86
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