Hi Guys. i was wondering if some of you could be helpfull and comment on a couple off pictures off my sparkplugs. i resently build a new exhaust system for my 4 port 13b with stock ports 48 mm ida and dlidfis. .
I just completed jetting the carb on the street without a dyno since the one i usually use is being rebuild.
My fuelpressure is 4,5 psi.
My Plugs are NGK BR8ET
MY Infinity AFR reads 11 alle the way from 3000 rpm to 7500 and its pulling really nicely much better than with the old exhaust and jetting.

But in my mind AFR 11 is a bit to much fuel. but i also think my spar plugs are looking quit good so i called it a day and will wait to hear from you guys.
I just installed the plugs 5 gallons off fuel ago i run premix.


Next Question my exhaust is a dual exhaust all the way and i attached a video were you can see and hear that my front chamber (right Exhaust pipe) is stumbling and not running correctly. i cant eliminate the stumble and therefore i was wondering could there be something wrong with my carb ore os it more likely a bad Apexseal. since i run Dlidfis only the trailing is on the distributercap could it be a bad cap?



Last video is from the last run it was pulling very nicely all the way to 7500 rpm.

Best regards Rasmus Andersen Denmark

 

cant see the vid.. however stumble at 2500- 3000
is pretty normal if you run the f11 emulsion tube
as comes on a little late and at first with a few drips

the trick is in getting the overlap between the idle/low speed and the main circuits to be minimal.
... and without one running out before the other has begun to flow correctly

with f11 you often need to have the three progression hole mod for the low down circuit
and also the rich F70 low down / idle jet
all to carry the engine a little higher in revs on the low down circuit before that e tube and main circuit starts to flow

using a larger air corrector on top of the e tube will also bring down the point the e tube and main jet starts to flow
( this is why typically you see f11 e tubes with such large air jet sizes compared to others )



another issue , independent of the e tube selection
is many inlet manifolds are designed for some of the early cars have bias lean to one side more than the other
this affects the fuel bowl height, and may bring on that sides E tube a little earlier than the other
dropping the fuel bowl height just a fraction below recommends may help it being so pronounced a difference
( if you have a decent bypass fuel system and pump and 3/8 hoses it wont hurt to drop the level a little )

dropping the level a little may also help lean that AFR a little

for best power NA aim usually between 13.2 - 13.7 :1 AFR

 

thankyou the video is to big for uploading unfortunatly so i will try to figure something out. yes the manifold is leaning a bit to one side. the problem is its only the front rotor that has the stumble i know that becaus the exhaust is dual all the way. her is my setup

No vacum
br8et plugs.
23 degrees timing.
dlidfis.
140 air
200 fuel
F3 misture tubes.
f70/10 idle.
42 chokes. .
3 progressionhole

my concern is that i think the plugs looks to be running quit good but the AFR says otherwise.
That stumble is between 1000-3000 rpm.

Could i go to maybe 160 Aircorrector to get rid of some of the stumble

 

https://www.youtube.com/watch?v=tp9W...ature=youtu.be

here we go that should explain my problem.

 

those plugs are maybe on the dark side of ok, i think you could go a little leaner. i did the same with mine, btw, it runs good with AFRs in the 11's and the plugs look good, so i just left it.

 

https://www.youtube.com/watch?v=Bbrz...ature=youtu.be
Here we go a couple of full throttle accelerations on last run.

 

all right what will the difference between going with larger aircorrecter versus smaller fueljet be.

 

the air corrector is the "air bleed"

.. or in comparison the finger closing off the top of the "straw"
going for the bigger air jet leans down the effect of the main mixture fuel jet a little
but mostly brings it on earlier

i see you are using f3 and IIRC these flow reasonable well down low compared to f11

however. you play it as you see it.. 14000 miles away ..





you have margins to lean down the fuel jet and open up the air jet to make it happen sooner

and you may try dropping the fuel bowl a little if things seem to be all to one sided

PS
it does sound like it is an instant rich on one side.. could be one side e tube flowing before other
double check both sides get the same squirt from the acell pump and check both sides have the fuel jet sitting snugly in bottom of the e tube

inspect the e tube and rod all the holes on the tube ( with welders tip cleaners )

and try dropping level just a tad

 

Dude! The tires on that thing! Jesus Christ!

 

Thanks for the reply's guys. I will try to play with the jets a bit. One Thing i did notice right away when i switched from f11 to f3 was that afr was much more the same all the way from low rpm to top.

Otherwise i think its pulling pretty good its just enoying with the stumble at idle.

Btw the tires fra 16" yokohama a006 rally tarmac. Its like being on rails.

 

Love tarmac rally tires

I would not get hung up too much on AFR. My car was reading 11:1 at high RPM (also with injector duty cycle at 125% due to a mapping error) so I worked to lean it out to 12.5-13:1 and now it won't pull past 9500. So maybe it liked having all of that fuel.

The most important thing I have learned about tuning is, give the engine what it wants, don't give it the number you think it should want. If it is happiest at 11:1 then give it that. If it is happiest at 14.2:1 then give it that.

 

thought you guys might wanna see som pictures of the car in action ive only done 2 real races in the car

 

look like fun!

got any in car vidoes?

 

Hallo agian i have entered two Rally-sprints with the new exhaust and the engine is pulling hard and all the way up. sorry no onboard videos yet i have been a little unlucky with the onboard camera will be getting it going for next race october 12.

I do have some great pictures from last weekend i did some really good times. i also just managed to fit a set of adjustable yellow Konis on the rear, the day before the race and they worked great.

 

 

Video from last race we appear
11 min 10 sek in
20 min 23 sek
30 min 19 sek
39 min 03 sek.