Jump to content
Sign in to follow this  
damunk

running rich on light throttle

Recommended Posts

damunk

idle is okay - bit lean at 16-17 - need bigger idle jets

1/2 - 3/4 throttle perfect 13.8- 14:7 - you can feel car feels right - feels easy, power

 

but very light throttle,  feathering , seems boggy

afr is around 11.5 , so going up hill 11.3 ish, so  then i give it more throttle 50-70% throttle  -afr shoots up even up hill up to 13.5 and feels like it is right again.

 

is it supposed to be like that.

all these readings are when everything is super warm. thats when i noticed it the most.

using TPS load on megajolt

Share this post


Link to post
Share on other sites
dvderlm

If this was a carb, for max power / climbing steep hills / overtaking you want 12.6 to 13.2:1 AFR (unless turboed).

For going up a hill at steady speed mid 13s is fine.

Richer than 12.2 loses power usually.

Cruising at light throttle 15 to 16 is good economy. Idle is whatever gives best vacuum (less a fraction). 13.9 to 14.2:1 is usually carb happy zone,

but 14.7:1 idle is what to aim for with injection and cat. It produces most CO2, but cat does conversion . 

 

The more you can advance ignition without knock, the leaner you can run. 

 

Watch out for large overlap cam distorting the readings

 

 

 

Edited by dvderlm

Share this post


Link to post
Share on other sites
damunk

i will read that thread as i got schrickcams - i aint to fussed about lean idle. so it looks like my timing needs sorting for light throttle - lower loads. 

my problem is light throttle - i used to be able to get 14.7-15.5 with the same set of carbs.

 

but ive im using a different default map so it must have affected light throttle

Edited by damunk

Share this post


Link to post
Share on other sites
dvderlm

Yes, very likely. Everything interacts. There's a timing map for a Hillman Imp engine Clan Crusader that goes for much more advance at light loads.

 

Get the timing right, then experiment with mixture, and repeat. 

 

You might need bigger idle as it extends from idle to 3500 ish revs on most carbs, so you may be running on main jets too early.

Which carb.

Share this post


Link to post
Share on other sites
damunk

CBR600 F4 1999 - from new I have done 8000 miles on them.

I will stick with this idle as it warms up it gets to 15.5 AFR

I know when it is too lean, you can hear a popping noise in exhaust. Happens at around 16.5-17.0 AFR

 

Yeah I will have a look at my map n see what the advance is for light load.

 

good thread by the way that you posted earlier.

 

btw going doing 1. 6 conversion with race cams makes noise alot louder, sounds like a race car, i assume thats normal.

on idle sounds like a race car, deep sound

Share this post


Link to post
Share on other sites
dvderlm

Get a 4 gas analyser reading. If the HC is high that will likely be ignition not advanced enough.

 

If the deep sound is smooth not raucous It'll be good.

There's a Mustang 5 litre near me whose startup sound is adjustable in software... think one of the settings is 'love your neighbours'.

https://social.ford.com/en_US/story/vehicle-type/performance/new-mustang-gt-v8-quiet-start-tames-the-growl.html

 

Share this post


Link to post
Share on other sites
damunk

no its not as bad as that lol. mine sounds like a car, not a tractor

by the way you ever used the ks3 phormula knock sensor 

Share this post


Link to post
Share on other sites
damunk

i got the ks3 phormula, will plug it in n check it out. tryna find peeps with it so can check whats lowest hz frequency setting i can put it on.

never used a knock sensor before

Share this post


Link to post
Share on other sites
dvderlm

900/(Pi *cyl radius in mm) is the knock resonance in kiloHertz according to the TI data sheet and the backshed article.

Edited by dvderlm
  • Thanks 1

Share this post


Link to post
Share on other sites
damunk

mines 7.5hz then

Share this post


Link to post
Share on other sites
damunk

i bet they use the same chip in all of them. and sell unit for £400, thats how much it cost . i got it around 2 years ago

Share this post


Link to post
Share on other sites
damunk

ah man, thats brill, thanks so much for that, so a case of setting it to that and using the gain to amplfy if needs be.

Share this post


Link to post
Share on other sites
dvderlm

Yep, and fit sensor where it picks up knock best ..

 

Wonder if Megajolt can use knock sensor like megasqurt?

http://www.megamanual.com/ms2/knock.htm

 

has some location recommendations too.

Share this post


Link to post
Share on other sites
damunk

no megasquirt is better, think megajolt doesnt do it. not sure on that.

the ks3 comes with a bosch sensor. you attach it to back of the afh block, think its behind cylinder number 2

Share this post


Link to post
Share on other sites
damunk

yeah i was gunna buy from these first but ended up going with ks3, they have some youtube videos lol  looked more professional outfit than j&s

j&s looked like he made it diy

ks3 looks like a fancy piece of kit

 

but these two are popular 

Share this post


Link to post
Share on other sites
damunk

using the megajolt default map. only driving up to 3000rprm during break in.

 

defsultmega.png.220b2dbd3e5e4fe4ffe8b201e14da124.png

 

 

 

Share this post


Link to post
Share on other sites
dvderlm

Default map will work, safe but not optimal.

I used 

http://useasydocs.com/theory/spktable.htm

which is a calculator then interpolated from the 8x8 table for manifold psi and revs, 

but clipped max advance to 36 ish for the Amethyst 

-which is far simpler curve not 2d grid-

as my engine GK is high compression and the Dignition is also cautious.. and using Momentum 99 octane to be safe.

 

Then spent ages adding a few degrees at idle live and seeing what happened at 1000rpm.

Then tweaking the mixture and seeing how low revs would pull smoothly at low and mid loads like when exiting a large roundabout in third gear,

then adding proportionate amount if it helped..

 

Needs quiet traffic.

 

So, you are going to use the KS3 to tune the ignition map?

Are you going to do it on a dyno? 

Edited by dvderlm

Share this post


Link to post
Share on other sites
damunk

going to do it on dyno at bogg brothers but wanna sort out this rich AFR at light throttle problem before i take it to them.

 

Share this post


Link to post
Share on other sites
damunk

turned out to be intake pipe ducting flange on the air box. it kept popping out one corner but i would not have thought that would result in a richer mixture under light throttle.

if anything would have expected it to be more leaner.

Share this post


Link to post
Share on other sites
dvderlm

Normally the easier air can flow in the leaner it will be - unless you add more fuel. The colder that air the leaner it will be - unless you add more fuel.  K&N filters suggest increase of 0.05 for main jets in carb versus OEM paper filter.

 

Which I guess is why huge filters and cold air feeds are popular, especially with injection engines. 

Share this post


Link to post
Share on other sites
damunk

right so when the flange popped out abit . it must have sucked warm air from the engine bay and disturbed the air flow to make it richer at light throttle.

it,s a carb so fuel would be determined by the air anyway. hmmmmmm

Share this post


Link to post
Share on other sites
dvderlm

Above normally is for fixed venturi. If it changed how the slide moved the mechanism it could go richer. Bike slide carbs have one more variable - the needle taper curve. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Terms of Use Privacy Policy Guidelines