Removed her heart...

[ribbert]

I LOVE those cars and would love see what you'll have down...and of course I would understand if you didn't want to post pics of your precious gems...thanks guys

This would take obscuring and pixelating number plates and rego labels to the next level, leaving the entire vehicle out of the photo!

[fj11.5]

dam, I didn't do that when I posted tail light pics OH NO

[Pat Conlon]

I'm not worried....

[fj11.5]

me either, not like they can't be seen when out and about 

[JMR]

just  thought....what kind of filters are you running? do you also have the bolt on optional air filter adapters?

I have the filter adapters and individual Uni filters as well...  lightly oiled, outside only.  I have had foam filters on various things and like the light oil/clean regularly approach.

Anyway, rode for 150mi today in 100 degree weather and the mid range was much more crisp...  the last ride was about 65 degrees out and the midrange was fat, so the slightly fat hypothesis is supported.  I actually think that's fine and today I got about 32mpg on HWY 130 (twisty and slow), so I think we're fueling OK for break in purposes now.  

The biggest change is low end which is smooth as silk now and easy to depend on.  Top end is also quite a delight, although I am using in moderation out of respect for the new internals.  

Thanks again Frank...  we're not fully tapping the potential yet and I'm sure the dyno tuning will unleash a whole new beast, but she's happy and running well enough to keep me grinning full time right now thanks to some pretty minor adjustments based on very specific recommendations...  I love this site!

Frank

Actually it is the other way around. Lower air temps increase air density and a richer mixture is needed. Higher temps decrease air density and less fuel is needed. High humidity will also richen any given mixture.

[Flynt]

Actually it is the other way around. Lower air temps increase air density and a richer mixture is needed. Higher temps decrease air density and less fuel is needed. High humidity will also richen any given mixture.

Some expert testimony may help here, but the dominant effect is the vacuum produced in the venturi of the carb and how much fuel flows as a result.  More dense air produces a stronger vacuum (due to higher velocity for a given manifold vacuum level) and you get more gas flowing, but the density increase is linear and the vacuum/velocity increases exponentially (see Bernoulli's equation for compressible fluid flow, specifically static pressure change), so you get more fuel than you do oxygen as temp drops and density increases.

It is a brain teaser, but my weber jets for cold weather were smaller than for hot weather.  My FJ in cold weather is running rich in midrange and appears to be closer to stoic ratio at about 85 degrees.  For an EFI system, you do squirt more gas for cold air.  For carb this is also happening, but it is convoluted with the increased vacuum effect. 

CV carbs, like the stock Mikunis, overcome much of this by using venturi vacuum to position the needle for the main jet (the "piston" part is adjusting venturi size to give Constant Velocity or CV).  Weber DCOE and Keihin FCR carbs use throttle position to position the needles directly and the compensation for air density is done by changing jet size.  Some might wonder why the hell you'd do this to yourself since you'll never be right on with the AFR...

Frank

[Pat Conlon]

Just remember these carbs are not set and forget.... they are racing carbs that pretty much demand a hands on approach in order to maximize their true potential.... I know you are a hands on fella so this tuning/tweaking thing is right up your alley. 

CV carbs, like the stock Mikunis, overcome much of this by using venturi vacuum to position the needle for the main jet (the "piston" part is adjusting venturi size to give Constant Velocity or CV).  Weber DCOE and Keihin FCR carbs use throttle position to position the needles directly and the compensation for air density is done by changing jet size.  Some might wonder why the hell you'd do this to yourself since you'll never be right on with the AFR...

This is the reason I have not pulled the trigger on the FCR's, (or the TMR's) on my 1350 motor.

I ride from sea level to 7,000 ft all the time. (almost every ride) Palm Desert to Julian/Palomar/Idywilld, etc.
My OSA temps range from the desert summer 120's at sea level to winter 45's at altitude, and everything in between.

For proper performance, I know that I need more air than the 36mm CV Mikunis provide the 1350 pump, but I do not want to have to fuck around with pulling the seat and tank to have to fiddle/adjust the FCR's.

Therefore....I am looking at/for some 38mm CV Mikunis that were on the pre EFI GSXR's. These should get a bit more air to the pump.
For a street bike, CV carbs are much more adaptable to elevation/temp. changes than flatslides.
I keep remembering the infomercial for the Ronco oven..... Set it and forget it...

[racerman_27410]

Some might wonder why the hell you'd do this to yourself since you'll never be right on with the AFR...

Frank

when  you whack the throttle open at 6 grand and the front wheel jumps for the sky  while you struggle to hold onto the beast it suddenly all becomes worthwhile .... you just cant get that kind of response with a CV carb.  

in practice (with the FCRs and correct base jetting) some simple tweaking of the mixture and pilot air screws can keep the air fuel ratio within reason, if not perfect, regardless of the season....... one just needs to keep a couple of screwdrivers on the bike for a quick roadside adjustment as required.  I just pull the seat and the left side panel for access (take the filters off from left to right)

http://www.magicracing.com/Motion-Pro-Pilot-Screw-Adjusting-Tool--Keihin-FCR-Carbs_p_4122.html

i live at 800 ft and normally ride from 1100 to 4000 ft and my FJ is tuned for those elevations...... its just a bit lean at 800 ft but i find no adjustments are required in the 1100 to 4500 ft range.  

KOokaloo!

[SlowOldGuy]

Some expert testimony may help here, but the dominant effect is the vacuum produced in the venturi of the carb and how much fuel flows as a result.  More dense air produces a stronger vacuum (due to higher velocity for a given manifold vacuum level) and you get more gas flowing, but the density increase is linear and the vacuum/velocity increases exponentially (see Bernoulli's equation for compressible fluid flow, specifically static pressure change), so you get more fuel than you do oxygen as temp drops and density increases.

Okay, I'll play ...

Nice logic, but you forgot to account for the variable venturi effect of the diaphragm slide.  As the velocity of the airflow increases, the diaphragm slide is pulled up to increase the carb throat (venturi) area and thus slow the velocity of the airflow back down to its desired "constant" value.  CV = Constant Velocity (and thus Constant Vacuum by Bernoulli's Equation)

The carb is designed to maintain a certain velocity by varying the throat area and thus maintain a (relatively) constant vacuum.  The larger area allows more air to pass and the higher slide/needle position allows more fuel to flow for the increased volume of air.

Colder air is more dense and since it's flowing at a constant velocity (at least up to WOT), it will lean out a carb mixture whereas less dense hot air, also flowing at the same velocity for a given throttle position, will richen it.

DavidR.

[racerman_27410]

Some expert testimony may help here, but the dominant effect is the vacuum produced in the venturi of the carb and how much fuel flows as a result.  More dense air produces a stronger vacuum (due to higher velocity for a given manifold vacuum level) and you get more gas flowing, but the density increase is linear and the vacuum/velocity increases exponentially (see Bernoulli's equation for compressible fluid flow, specifically static pressure change), so you get more fuel than you do oxygen as temp drops and density increases.

Okay, I'll play ...

Nice logic, but you forgot to account for the variable venturi effect of the diaphragm slide.  As the velocity of the airflow increases, the diaphragm slide is pulled up to increase the carb throat (venturi) area and thus slow the velocity of the airflow back down to its desired "constant" value.  CV = Constant Velocity (and thus Constant Vacuum by Bernoulli's Equation)

The carb is designed to maintain a certain velocity by varying the throat area and thus maintain a (relatively) constant vacuum.  The larger area allows more air to pass and the higher slide/needle position allows more fuel to flow for the increased volume of air.

Colder air is more dense and since it's flowing at a constant velocity (at least up to WOT), it will lean out a carb mixture whereas less dense hot air, also flowing at the same velocity for a given throttle position, will richen it.

DavidR.

That covers temp..... but then you also have to add elevation and humidity levels to the equation.

This is fun stuff!.... well ok maybe not so fun ....but power wheelies ARE fun and ya cant get them without proper tuning

KOokaloo!

Frank

[SlowOldGuy]

Frank,
True!  Elevation and humidity also affect the mixture.  Along with temperature, those factors vary the air density / oxygen content which is an almost negligible input to a CV carb when compared to the air velocity effect.

I remember the good old dirt bike days when I controlled the slide directly.  I might not have been as accurate as a CV carb at providing the optimum mixture at all times, but that '74 MX-360 2-stroke sure was a blast to ride regardless of the A/F ratio I was providing.  I still miss that bike everytime I get on my TTR-230 (what a gutless pig at every throttle position).

DavidR.

[racerman_27410]

Frank,
True!  Elevation and humidity also affect the mixture.  Along with temperature, those factors vary the air density / oxygen content which is an almost negligible input to a CV carb when compared to the air velocity effect.

I remember the good old dirt bike days when I controlled the slide directly.  I might not have been as accurate as a CV carb at providing the optimum mixture at all times, but that '74 MX-360 2-stroke sure was a blast to ride regardless of the A/F ratio I was providing.  I still miss that bike everytime I get on my TTR-230 (what a gutless pig at every throttle position).

DavidR.

David,

I'm sorry about the TTR my friend..... "gutless pig" doesnt sound like much fun.  Big bore? Cams? flatslide? turbo? nitrous?
   surely something can be done ?

I also have a FCR on my DRZ and other than tweaking the mixture screw occasionally its been pretty much set and forget.
Luckily i bought the "T" version of the mixture screw for that one so its easy to adjust on the trail.

http://www.jdjetting.com/xcart/product.php?productid=46

kOOkaloo!

[SlowOldGuy]

David,
I'm sorry about the TTR my friend..... "gutless pig" doesnt sound like much fun.  Big bore? Cams? flatslide? turbo? nitrous?
   surely something can be done ?

I'm biding my time.  My buddy with the Super Tenere also has a WR-450 set up as an S/M streetbike.  I'm sure he'll get restless and want something else next year.  THAT bike is a total blast to ride EVERYwhere! (Well maybe everywhere except for the highway).

DavidR.

[racerman_27410]

I'm biding my time.  My buddy with the Super Tenere also has a WR-450 set up as an S/M streetbike.  I'm sure he'll get restless and want something else next year.  THAT bike is a total blast to ride EVERYwhere! (Well maybe everywhere except for the highway).

DavidR.

now we're talking!   

you'll be pulling horn mono's, jumping ditches into parking lots and riding up and down stairs before you know it 

KOokaloo!

Frank

[Flynt]

...you forgot to account for the variable venturi effect of the diaphragm slide.

I DID NOT!     read a bit more and you'll see I mention the CV advantage.

We're talking about Keihin FCRs (or Weber DCOEs) which are not CV design like the stock Mikunis (or the stock Hitachi SU knock offs on the original 240z).  Agreed CVs are nice in that they compensate for a much wider range of atmospheric conditions, but they're not going to give your wrist the direct ability to step change airflow and squirt gas directly into the intake (accelerator pumps) to get the OMFG reaction Kookaloo represents.

I'm a chronic tuner and having the flatsides will give me hours of play time.  I also really like dyno tuning stuff and am looking forward to the first motorcycle dyno experience.  Crazy when this all started with arguably one of the nicest, best sorted FJs out there...  but look where we are now   

Frank