Lean Spike Coming up on the Brake

General Nitrous Discussion

Moderator: John_Heard

Message
Author
User avatar
jmarkaudio
Posts: 278
Joined: Fri Oct 26, 2007 4:22 pm
Location: Florida
Contact:

Re: Lean Spike Coming up on the Brake

#16 Post by jmarkaudio » Fri Jun 29, 2012 3:24 pm

If you can post all the info on the carb, size, all metering data including air bleeds, idle jet size, intermediate jets, emulsion bleed size number and position.
Mark Whitener
Image
____________

Good work isn't cheap and cheap work can't be good.

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#17 Post by John_Heard » Fri Jun 29, 2012 3:38 pm

I have a sheet on it, but I'm not sure it's accurate re:jets/bleeds etc. as I bought this carb used. I'll see if I can verify the info this weekend and post it.

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#18 Post by John_Heard » Sun Sep 30, 2012 11:52 am

Sorry to be slow to post this, got to working on some other projects.

I just got done tearing the carb down and everything is the same as this sheet, except the Int Air bleeds are not .060, they are .078, which is a long ways from what the carb had originally. The squirters are also .054, not .052. I don't know why those were changed, but must have been set by the previous owner. Would those larger bleeds on the intermediate be responsible for it going lean like that when coming up on the brake?

Image

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#19 Post by John_Heard » Thu Oct 04, 2012 11:48 am

Talked to Patrick at Pro Systems today, he thought I should try going back to .060's on the intermediate bleeds, he thought it was likely the .078's were likely the reason it was way lean at tip in getting on the chip. So, I've got those in it now, hopefully that and the rebuild will fix that issue.

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#20 Post by John_Heard » Mon Oct 29, 2012 11:38 am

Well we tried the .060 intermediates, tip in still lean, went back to .078's, same thing. Didn't really seen any difference with that change.

However I did see a difference in the O2 depending on how I brought it up on the brake on one run. If I brought it up slower, the AFR looks a lot better without spiking way lean. It's sounding like accelerator pump squirters I think?

silvanova
Posts: 143
Joined: Sun Aug 27, 2006 11:55 am
Location: KY

Re: Lean Spike Coming up on the Brake

#21 Post by silvanova » Sun Nov 04, 2012 6:15 am

john, how clean does this Carb run going down the track?
5.004 @142.6

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#22 Post by John_Heard » Sun Nov 04, 2012 9:20 am

It's fine down track, nice and flat and pretty even left/right bank about 12.5:1 if the O2's are correct. I haven't calibrated them recently so they may be off some. Just goes lean when you set the brake and bringing the RPM up on the chip. Maybe I need to just change my staging procedure, I'm a bit gun shy after it coughed a few times so I tend to bring it up in RPM a bit before matting it.

silvanova
Posts: 143
Joined: Sun Aug 27, 2006 11:55 am
Location: KY

Re: Lean Spike Coming up on the Brake

#23 Post by silvanova » Sun Nov 04, 2012 10:39 am

just curious. my Carb is a 1200 and its quite a bit leaner and my o2s show way rich. jmark has been helping me lean it out alot. I had 45 squirters in it and he told me to try 35s. so far it's running a lot better just need to head to the track to get some data.
5.004 @142.6

User avatar
79 Camaro
Posts: 738
Joined: Fri Feb 24, 2006 11:38 am
Location: Caney, Ks

Re: Lean Spike Coming up on the Brake

#24 Post by 79 Camaro » Sun Nov 04, 2012 6:28 pm

I always bring mine up to 2000 rpm's before setting the trans brake. Makes sure the carb don't stumble and the trans has some pressure before setting the brake which holds the car better. But I don't have 02 to see all the fancy stuff .
"THE THROTTLE IS THE DEVIL" By Mr. Willis
"ALL I SEEN WAS HOOD!" By Mr. Heard
MAKO RS-1979
Sponsored By:
Total Removal Contracting-Tim Rogers

User avatar
John_Heard
Site Admin
Posts: 5684
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

Re: Lean Spike Coming up on the Brake

#25 Post by John_Heard » Sun Nov 04, 2012 8:31 pm

That's actually kinda interesting, as I attempt to do that as well, but not quite as high a RPM from what I can see. I did find this when comparing two runs. One run where I had the RPM up higher, it didn't do it. The Arrow shows the pass (blue lines) where it didn't go lean.
Attachments
lean2.png

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest