JET-A-VATOR Experiment

Doug Berg · Posted: Thu Apr 23, 2015 1:44 pm Post subject:

Here's my take,,,, The compression ratio is somewhere near 8 to 1 @ tdc!!! The compression ratio @ 34 degree's timing is 4 to 1,,,, So w/ the throttle open it's 4 to 1!!! w/ the throttle closed it's 8 to 1!!! The more you retard the timing ( the more complete the combustion ) (burns more fuel) (JAV is doing the same,,, Compounding the burnt fuel,,, even more burnt) So if the engine is burning more fuel when the throttle is closed,,, That fuel is basically "disappearing" Because the wheels are not going around!!! That's why opening the volume screw w/ timing retarded more fuel disappeared!!! "I think" (and it's up to what the engine thinks) That w/ the higher initial timing It'll start to like "opening" the volume screw!!! Instead of it just burning it while the car is "not in motion"!!!! (burning less fuel while the car is just sitting) Doug...

Porsche60 · Posted: Sat Apr 25, 2015 4:29 am Post subject:

got my JAV. thank you Doug!
it's 30%.

i hooked up AFR gauge before installing JAV, so that i can see how it changes.

then i installed JAV, without changing jets.

what i have found so far:

1. JAV smoothed acceleration especially for low throttle.

2. JAV slightly enriched low throttle and slightly leaned WOT.

since WOT was lean, i changed main jet 5 richer.
Doug recommended 7.5 richer but i thought it is too rich by AFR.
i have an experience that rich main jet caused bad mileage before.

so, WOT got richer than before installing JAV.
not getting MPG record yet.

i feel that i have to change pilot jet, maybe richer, and probably main jet leaner.

Quokka42 · Posted: Sat Apr 25, 2015 4:58 am Post subject:

Remember that the WOT with the JAV is equivalent to 70% throttle without, and that WOT is where you don't ever want to run lean. Low throttle is where you want to be able to lean out (use less fuel at cruise,) If more fuel at WOT gives more power you will spend less time at WOT - so you tend to use the same or less fuel.
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vamram · Posted: Sat Apr 25, 2015 5:09 am Post subject:

Porsche60 · Posted: Sat Apr 25, 2015 5:39 am Post subject:

i run 34pict-3.
but i wrote Bergs wrong jet number... lol

i forgot that my carb has larger venturi and ran 140 main / 55 pilot before installation.
anyway, i have a set of jets.

so, i changed pilot 5 richer (60g) and runs better.
but not sure if it's good for MPG.

vamram · Posted: Sat Apr 25, 2015 6:13 am Post subject:

A larger venturi? What brand carb is it?
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Porsche60 · Posted: Sat Apr 25, 2015 7:12 am Post subject:

brand is Bocar but venturi was enlarged by someone.

vamram · Posted: Sat Apr 25, 2015 8:55 am Post subject:

Do you know what your MPG was before the JAV?

I have an update w/out having made any changes from the last update:

23.63 MPG

Big drop. The only thing I can figure is that I spent much more time in stop-n-go traffic and took a lot of short trips during this latest batch.

I've put on about 2k miles on the car since installing the JAV. I think w/my engine, that's probably about as good as it's going to get.

Frank - a difference w/driving around town here is that distances to places are short, whereas in Miami you could drive 5 miles one-way to get to a Sedanos!
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Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!!

Porsche60 · Posted: Sun Apr 26, 2015 3:23 am Post subject:

Before JAV:
last week, i had an opportunity to drive highway for 140 miles one way, and climbed 4000 feet.

mileage were 26mpg outward (uphill) and 35mpg homeward (downhill).

After JAV:
today, i drove 80 miles highway. no up and down.
mileage was 26mpg.

the result is fair considering that i richened up both main and pilot jets.
i will replace pilot from 60 to 55 then calculate mpg again.

Frank Bassman · Posted: Sun Apr 26, 2015 5:51 am Post subject:

That is true... I still averaged 28.4something. After getting stuck on the turnpike from nw 74th to sw 88th streets.... traffic is so bad that now i go north to krome av and take that down to kendall drive!

vamram · Posted: Sun Apr 26, 2015 7:21 am Post subject:

Ha! That Krome avenue round-a-bout is a nice excuse for a cruise! You're probably adding 20 miles to your commute! Same thing around here adds about 1.5 miles to my trip home! Laughing

vamram · Posted: Mon Apr 27, 2015 4:01 pm Post subject: MPG UPDATE

26.17 MPG w/the retard hose re-connected.

Thinking of dropping back down to the 130 jet...

Porche60 - any updates?
_________________
Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
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Save the Supers!!

Porsche60 · Posted: Mon Apr 27, 2015 10:30 pm Post subject:

I drive only weekends so wait until next weekend.

i think 23-24mpg/city, 28mpg/highway is good enough for a stock 1600.

tire pressure also affects mileage.
i run 22psi front, 28psi rear. those numbers are low compared to modern cars.

I want to replace front strut inserts to soft ones and increase tire pressure.

veedubcrazy · Posted: Tue Apr 28, 2015 8:15 am Post subject:

I routinely get 30+ mpg's with my '67 and I don't even use a JAV. It's a 1641 (low comp) w/ an E100 cam. I upped the main to 125 (might be a 127.5 I got from ac.net, its been a while) in the 30pict1 carb too. All else is stock. Stock trans with proper tire pressure. Now, its not a daily driver but in/around town and hiway nets me 30+. I have touched 36mpg before but that was 60mph with the wind pushing slightly...
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Porsche60 · Posted: Tue Apr 28, 2015 8:52 am Post subject:

actually, i don't expect MPG from JAV.
all i want was smooth acceleration when it's cold outside. (below 55F)
this effect improves mileage, i think.

it's not that cold already so i can't figure out how it helps!

i think less MAP improves mileage, because it needs less fuel.
you can create less MAP by less opened throttle, smaller venturi, higher altitude, and JAV.

but less MAP means less performance, for a same engine.

vamram · Posted: Tue Apr 28, 2015 8:56 am Post subject:

At this point, I'm keeping the JAV for the smoother feel of the engine, as Porche has corroborrated.

I haven't seen a dramatic change in MPG and I've been running w/it now for over 2k miles, probably double what I normally drive in the same stretch of time, just to put it to the test.

I did drop the main back down from 135 to 130 this morning. I'll keep posting MGP updates.
_________________
Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!!

Doug Berg · Posted: Tue Apr 28, 2015 10:22 am Post subject:

Sorry to take so long,,, We were Drag Racing in So Cal this weekend,,,, The JAV's % of restriction is based off of the "area" of the throat's size (choke,,, or venturi) The 34 pict is 26mm (measures 26.2 - 26.3mm) (or 541mm of area) The 30% JAV is 1.75mm hole x 151 holes (or 363mm of area) Which is roughly 33% restriction!!! If you open up the throat size to 28mm this would be closer to 40% restriction!!! (area is,,, the radius squared X 3.1416) Doug...

Doug Berg · Posted: Tue Apr 28, 2015 10:57 am Post subject:

Vam,,, something else is going on!!! For it to be @ 23.?mpg w/ both hoses connected,,, Then disconnect the retard hose & it go's up to 27.5mpg,,, then back to 23 mpg,,, reconnect the retard hose & back to 26mpg The #'s should be way more consistant than 3 - 4 mpg variance!!! Porsche 60 stated an increase in torque across the board w/ the zoomtube,,, One of the way's this is done,,, is by moving "more fuel" across the top of the piston!!! He also stated richer @ "part throttle" !!! This is also moving "more fuel" across the top of the piston!!! But I also believe that it is "more scavanging" @ overlap (not burning or "raw fuel") (also could be more initial timing than your's has) I've never tested a zoomtube,,, or JAV w/ vacuum distributor Always stock muffler or extractor,,, and an 009 centrifical advance distributor,,, (So I'm in the "learning" process with you!!!) "I think" Porsche 60's is a zoomtube & 009 distributor??? Maybe he will "share" his initial & total timing #'s !!! If you don't mind that we do both JAV's in "your post" I don't wanna hijack it or offend you!!! Doug...

vamram · Posted: Tue Apr 28, 2015 11:11 am Post subject:

No offense taken, Doug. I welcome someone else taking a shot at it, after all it's in keeping w/the "experimental" nature of the topic, no hijack worries.

I can only go by what my numbers are showing me after 2k miles. I'll keep posting back my results as I go, but I'm sticking w/the DVDA!! Love my factory dizzy! And from what I've seen in timing it, it's pretty tight!

Victor
_________________
Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!!

Doug Berg · Posted: Tue Apr 28, 2015 12:24 pm Post subject:

I don't wanna "over complicate" or "over simplify" things!!!! From what Porsche 60 said,,, kinda proves the JAV is vaporizing the fuel more effectively,,, If the mix is broken down better,,, It should be in a "lighter" state,,, (weight wise) and easier to be vacuumed out (@ overlap) For it to be leaner @ "WOT" also means easier to burn,,, (more complete combustion) (signs of less total timing!!!) The air jet controls "top end" enrichment!!! In the U.S. I've only seen 75z & 80z air jets,,, A smaller air jet will fatten up the top end!!! (richer) or more total timing!!! This will also increase initial timing so smaller pilot jet or tighter on the volume screw To lean the bottom end & fatten up the top end!!! My uncle (mom's brother) had a V.W. repair shop for years,,, And he asked me if I had ever taken a pair of side cutters (wire cutters or dikes) and crimped the emulsion tube to restrict flow (something I've never done but is and option if you have a spare to test with!!!) Doug...


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