VVT Solenoid- Red Bullet or Bull@*$% ?

WARNING! Long winded post below with lots of technical content!
Continue reading at your own peril.

SO, for a while I have been intrigued by the claims made by Red Bullet about
their VVT solenoid. Better, faster, MPGer, etc. Initially, I was skeptical, both
because the website has lots of marketing hype with no data, and because as a
mechanic I don't see how "shortening the response time" of the VVT system
would have any significant gains - the system (at least on a Prius) usually isn't
being commanded to make rapid changes to cam timing. I BELIEVE IN DATA. I
don't want adjectives, or testimonials. I want tests that I can perform (or at least
understand the procedure) and the results from those tests. Anything else in my
eyes is here say, opinion, or placebo affect.

First, what is VVT? ICE design is a series of compromises. Power vs. emissions vs.
MPG vs. cost. The ICE is an air pump- the timing of the valve opening and closing
(in relation to the crankshaft or piston position) directly affects how efficiently that
pump works (which affects the other variables). Using a camshaft to mechanically
control the valves is a cheap and reliable solution, BUT the "best" valve timing
changes as RPM and load changes, while the cam lobes are "fixed". So a cam
design that's good at low speeds doesn't work well at higher rpm and vice versa.
Variable Valve Timing allows the camshaft to rotate with respect to the cam
sprocket- altering when the valve timing occurs vs. crank position (at a decent cost).
This allows the engine to operate more efficiently over a broader RPM range. It doesn't
increase horsepower, but it can "flatten the torque curve".

How does it work? The ECM controls a solenoid that has an electromagnet that
moves a round piece of steel (called a pintle). The pintle pushes a round bit called the
spool valve while a spring pushes back. The spool valve is in a housing that
directs pressurized engine oil through passages in the cylinder head to the
intake camshaft sprocket (VVT actuator). Controlling how much oil goes into two
different sections of the actuator controls the camshaft timing. With the solenoid
"off", the cam is fully retarded (timing is "late" vs. the crankshaft). With the
solenoid fully "on", cam is fully advanced (timing is "earlier" vs. the crankshaft).
Changing the voltage will change how much the spool valve moves- allowing the
timing to be changed slower, or to "hold" cam timing steady by keeping equal
pressure in the two sections of the actuator.

I wondered about how well the Red Bullet would work, eventually I went and
bought one to test it. Then to be thorough I bought a new OE unit from the
Toyota dealer, as well as the cheapest one I could find on amazon.

But how would I test them? Don't have a dyno to measure torque at the crank.
Acceleration tests have way too many variables. MPG tests have even more
variables. I know, why not measure what the website claims that the RB does?- ie,
how fast it takes for the VVT system to respond to solenoid commands.
Now I must say that while I generally like Toyota and how they design things,
when it come to the VVT system and scantools- their engineers were schmucks.
Most other makes have USEFUL VVT data and tests- desired and actual cam
position, solenoid % commands, even position error. Great stuff. Not Toyota- the
data is "turned off", even though the system is always "in use". Data IS there but
only while performing a VVT bidirectional test. The "VVT CTRL percent" test is fairly
useless as it takes a long time to change the solenoid command one click at a time
(+1%, +1%, +1%....-1%, -1% etc). The "VVT CTRL on/off" test is better- it rapidly
commands the system to full advance (73% DC) or full retard (12% DC), but both
tests ONLY function at idle- don't really have lots of oil pressure then and Prius likes
to shut off the ICE when it wants. Any throttle applied will cancel the test.
The lack of VVT scan data made it difficult to determine what the ECM was
commanding, and even if there was data, a scan tool is much too slow to
evaluate VVT function and effect.

It was time to bust out the oscilloscope and get crafty. A scope displays electrical
signals along with a time base- so you can "see" things the same as what goes in
and out of the ECM. Voltage is displayed on the up & down axis of the graph while
time is shown from left to right. (it's a fancy voltmeter that uses piles of colored
string instead of numbers).

The ECM controls the VVT solenoid by switching the positive power supply to it
on-and-off really fast (300 times a second). The solenoid can't open and close
anywhere near that quickly- but by changing the percentage of time that the
voltage is high (14.0V) or low (0V) [during each of the 300 cycles per second], the
average voltage is changed- which controls how far the pintle and spool move.
This is known as Pulse Width Modulation (PMW), and the percentage is called
"uty cycle" (DC). 100% positive duty cycle for this system would be 14V, 90% = about
12.6v, 50% = 7V, 10% = 1.4V, 0% = 0V, etc. After driving the car for weeks while
scoping the VVT, it appears that 12% DC is "full off" - retard. 37 to 42% is "hold the
timing steady". 45% and up is "advance" but I seldom saw anything much above
50%. Here and there I briefly had 55-60%. 50% and 60% DC were the "advance" target
I used for manual testing while 15% DC is "retard" (effectively the same as 0%) .

The ECM has sensors that it uses to monitor the crankshaft and camshaft position
(and how they relate to each other). Each sensor generates a pulse of AC voltage
when a spoke from the trigger wheel (on the crank or camshaft) passes by. The
crankshaft has 34 teeth spaced 10 degrees apart with 2 teeth missing to create a
signature pulse that the ECM can recognize (aka 36-2 pattern.) The cam has 2
pulses during one crankshaft revolution then 1 pulse for the next - again to allow the
ECM to ID where in the 4-stroke cycle the engine is. Here is the waveform for my Gen2.

The test subject in use is my 2006, with 175K (and apparently decent maintenance
by the previous owner). I performed several tests on each solenoid- attempting to
minimize variables and create repeatable results. I installed the solenoid and
drove it a few days (can't say that I noticed any particular "seat of the pants"
difference for ANY solenoid). Engine oil is generic synthetic with a couple
thousand on it- level is full. Then for the tests I warmed the engine up until the
radiator fan cycled several times.

First test was to unplug the solenoid and manually apply full power and ground
("ready" at 14V but ICE off) while using an amp clamp to scope the current used
by the solenoid- I wanted to see the electrical characteristics. All three (OE, RB, AND AM)
use about the same amount of current, but the amperage patterns indicates that each
pintle moves differently. Likely different return springs, but could also be
changes in pintle design.

Next was the scantool VVT control test (not a great test but the ECM is consistent,
so I figured I could compare each solenoid- apples to apples). I used the scantool
test to drive the solenoid from "OFF" (12% DC or full retard) to "ON" (73% DC or
slam it fully advanced). "Maintenance mode" is nice to keep the ICE running but
it stops when you exit to go to the VVT tests-I hit the throttle to start the ICE and
shifted to neutral to keep it running . I capture the cam and crank sensor signals
as well as the VVT solenoid control. The scope software converts the solenoid
control into a duty cycle graph. When that graph changes state, I zoom in and start
comparing the two sensors until I see that the cam is fully advanced or retarded
and count how many engine revolutions it took to accomplish that. Each entry
resulted from at least 3 samples that were averaged together and rounded up

After that I wanted to try things at higher RPM. So I used my function generator
(electronic test widget that produces different electrical signals: sine wave,
square waves, etc- doesn't everyone have one of these?) to output a 0-12V
adjustable pulsewidth signal at 300Hz to drive a mosfet and added a couple
diodes to clean up the signal. (So the PWM is inverted once at the FET, but I only
had a N type FET so I am controlling the NEGATIVE side of the solenoid - PWM is
effectively inverted twice, but have to keep that in mind when looking at the
scope- ie, 60% on the function generator is 40% on the scope but it's on the
negative side so it equals 60% on the positive side- which is how the ECM would
have controlled it- bleh!). This setup drives the solenoid directly- no ECM, so I can
rapidly switch duty cycle to whatever I want (within limits). I propped the throttle
down to bring the revs to 2400-2500 in park and ran several 15-50% and 15-60%
(advance) tests and back again (retard). Results were measured and averaged as
before.

Now let's meet the contestants. First up is the OE replacement from Toyota, $87
from the local dealer. Fits like the original because it's made like the original. Should
outlast the car. GO team OEM!!


Next is the REEEEEEEDDDDD Bullet!!! Faster is the master, redder is better,- (err
wait I minute- it's NOT red). What?- but it's called the RED bullet. (Sorry- must have
run out out of red coloring). Well, it USED to be red. Seen it on the website. In
fact, it looked very very similar to the much pricier "Quantum Solenoid". Eh-
whatever. $113 + shipping gets you this performance MONSTER (that arrived in a
"Chiayi Racing" box). go rb- yippee. (ps- fits just fine)

Last is the bottom of the barrel, cheaper is a keeper. amazon's "most thrifty"
AfterMarket offering that goes for the princely sum of just $10.52 plus tax! (free
shipping with prime!) No brand name on it anywhere! It looks like you might
expect for the price. The mounting tab had to be bent out then shimmed with a
washer, and I had to be careful getting the connector JUST right to plug it in.
Who knows how long it will last, but "hey it's a part!". Let's give it up for team
miser!


NOW, here's the test results. - that I measured on MY car using the parts that I
received. YMMV



Well....Ummm. Yeah. SOoooo, the Red Bullet was slower on all tests when
advancing cam timing when compared to the OE solenoid, and only slightly
faster than the cheap AM unit at 50% DC. All units were able to retard about
the same.
The world has been enlightened. Do what you will with this- now live long and
prosper.

Edit: forgot to add that total range for VVT adjustment is about 38 degrees.

Maybe we can call it "the Bullet formerly known as RED"?

 

If you like the product, then it's good for you.
I just want to see some proof that it does what it says (more oomph) the way it says it does it (by faster VVT).

Posted via the PriusChat mobile app.

 

Well, trying to process the data from real "on the road" driving is a PIA. I don't know of a way to force consistent operation of the VVT system. Drive several times in what seems to be identical manner and get different results- or perhaps very minor timing adjustments. Short form is I can't beat the programming- it'll do what it's gonna do.

My thought was perform tests with more variables under direct control in order to get repeatable results.

I just want see how the RB is "faster".

Posted via the PriusChat mobile app.

 

Well, I bought my Red Bullet from that site that you linked (redbullet.net), all correspondence was with Max Jen International.
What's interesting is a few months ago I was considering doing all this but didn't buy then - here was a screenshot from the site in June.

When I did purchase the solenoid the site had changed to what is shows now.

If you scroll to the bottom of the pics in the prius section you see this.

That's the same brand as the box my part came in. So if there is more than just a color change then it is because Max Jen changed suppliers or designs- or ownership.

 

If anyone wants to loan me an "old" Red Bullet, I could run the same tests on it and see.

Posted via the PriusChat mobile app.