Would You Believe This...

[Stallion]

Okay, I think I see what you mean about the carbs and the fuel. How many barrels do Vettes usually have? 4?

Thanks again!

TR

 

[GerryLP]

15:1 ratio is the textbook A/F ratio. In a perfect world that would be the case, but the world is far from perfect.

Boy...one can't get one past Scam...:L Yes! The 15 to 1 ratio is the ideal and probably the volumetric efficiency and inlet/exhaust port tuning are factors that prevent or limit the ideal fuel/air mixture goal. The key factor to engine carburation is getting the fuel atomized and vaporized (whatever fuel is not vaporized then it won't burn when ignited and it is wasted). Carburators today include many features just to improve fuel vaporization.

As you can see in Gerrys case it made a BIG difference.

Hey people...I am including my dyno run graph that I completed on my car last friday. Notice the bottom horizontal curve how low it is against the fuel/air mixture scale. The second one from the bottom was performed with the air cleaner removed, a 4 inHg secondary spring, and shifting the tranny manually. All these values are at approximately 5,280' of altitude. The conversion to sea level comes in at around 75 to 85 more horsepower.

Since, I have changed the primary fuel jets from Holly 72's to 68's, and I moved the 72's to the secondaries. I am working on getting the timing perfect, and I decided to lower the upper range for the maximum advance to 3,200 as adviced by Mike (Stingray6974). I also had to re-arrange the positioning of the cruise-control rod to the carburator and the throttle. I was not getting WOT. The gas pedal feels alot softer now, and I believe that I can attain WOT.

 

[LT4hitsthespot]

Working on your own car can sometimes be bad but turn out good. I got another vette that way. I went to do an oil change on my Ford 4X4 and was talking to a friend while doing it. I reached under and felt for the drain plug and then drained the oil. I just took and put the required oil back in and knowing how much it took, I got lazy and didn't check the level.

A day or so later I found out what I had done. I had drained the transmission oil pan and then over filled my oil. I felt like an idiot. I didn't do much driving in it before I found out and a ford mechanic told me that it probably didn't hurt it but I was paranoid about it. I got rid of it the next day and drove home with another vette to take it's place.

Great reward for an idiot huh?

 

[BlackNBlue95]

Great reward for an idiot huh?

Shure.. I almost did that once on an import.. had 2 pans that looked very similar front wheel drive either a honda or a toyota can't remmber but they both had similat pans.. and I wasn't paying close attention and pulled the trans plug, oil changes get monotonus (spelling?)thats not all I do but I do alot of them being that I am one of the younger guys in the shop.. ANY WAY.. I knew as soon as I saw the red fluid I put the plug in right away then drained the right oil pan.. and re checked and added a small amount of trans fluid.. it's an easy mistake on those. but on a rear wheel drive usually it's easier not to make the mistake.. eh well you still came out ahead a vette beats any ford any day.. and I don't mean performance wise nessicarily because there are some fast fords out there..
-Rick

 

[sscam69]

Boy...one can't get one past Scam...

:L

Wow Gerry that A/F ratio is all over the place!!:eek.

I guess I am used to seeing the graphs from EFI cars that have REALLY straight lines all across the board.

I need to dyno tune my car but I am trying to do as much as I can before I go.

Hey Gerry I live at ~4000ft. I have the stock jets tuned for sea level but I want to change them to the ones required. I believe Holley recommends 1 or 2 (can't remember at the moment) jet sizes per every 1000 or 2000 feet. BTW I have a 670 Avenger.

Is this what your going on? I am going to buy the jets at the local Autozone for $30 (set) and swap them out. I am also going to adjust the idle vacuum and the timing once I swap them out.

 

[GerryLP]

Hey Gerry I live at ~4000ft. I have the stock jets tuned for sea level but I want to change them to the ones required. I believe Holley recommends 1 or 2 (can't remember at the moment) jet sizes per every 1000 or 2000 feet. BTW I have a 670 Avenger.

Scam, the paperwork that I got with my carb recommends 1 jet nozzle size smaller for every 2,000' of altitude. I jumped from 72's to 68's just going from recommendations from technicians at the dyno shop. Stingray6974 (Mike) suggested that I dyno tune smaller jets until I see no power gain on the chart, and then add two sizes bigger to the last smallest jet size. So I plan to do like you plan to do. I'll buy a whole set, and tune the carb on the dyno. I'll need help for this from someone that can help me replace them quickly so as not to waste excess dyno time.

Is there a dyno shop in El Paso? If not...do you want to come up to I'llbequerky (ALbuquerque), and we'll help each other out? The 1,000 foot difference can be absorbed by going to the next smaller (for my altitude) and higher (for your altitude) Holley jet size. What do you think??

However, I am currently in San Diego visiting family and recoverring from a big scare with my father-in-law. He had a stroke, and things have been dicey since; nevertheless, I'll return to work on the 6th of Jan 03, and so I'll have to return to NM sooner or later.

 

[sscam69]

However, I am currently in San Diego visiting family and recoverring from a big scare with my father-in-law. He had a stroke, and things have been dicey since

I am sorry to hear that, my prayers are with you and your family.

Is there a dyno shop in El Paso?

Yeah theres a guy right down my street that has a chassis dyno that can handle up to 1300hp, but I don't know if its equipped with a wideband O2. I don't know of any other than him. He charges $50 for 3 pulls within 1/2 hour.

If not...do you want to come up to I'llbequerky (ALbuquerque), and we'll help each other out?

Ya know I just might be going up there in a couple of weeks. I am still looking for an engineering job up there, with no success. My undergrad GPA seems to scare people away, Its not bad but not great either. I guess finishing in 4 yrs (shoulda taken 5-5 1/2) and working 20-40hrs (1/2 doing research at school-1/2 working part time) a week wasn't such a smart idea, but then again I put myself through college (parents couldn't afford it) and mangaged to support myself financially 95% of the time.

I might be going up there to talk with my fiances mentor about possible employment with Sandia, if not, places where I can apply for possible employment. It looks like, at this point, she'll have a job up there with them when she graduates in May, get married in June, and move up there at the end of June if not sooner.

 

[sscam69]

Where can i learn more about the wideband 02's and how they work I vaguely remmber an instructor discussing these at an automotive seminar I went to about fuel control.. any websites or anything like that would be appreciated.. he was also talking (I was half asleep after work) about our 02's being basically a lambda switch.. and something about how the wideband varies amperage instead of voltage.. and somewhere a digital signal I dunno would like to know more though..

I don't know exactly how a wideband O2 sensor works BUT I have seen the graphs between a wideband and a "regular" O2 sensor and the difference is in 'the resolution of the picture". With a wideband sensor there is a lot more detail with the readings.

I am trying to learn how EFI works and I am trying to find information on how to manage EFI systems. Ya know like how to manage Spark tables, fuel tables etc. I'll look into it more and give you a heads up on the info, as I am trying to find out myself.

ON a side note I know that you can make one for yourself for about $800. If your the avid do it yourselfer (like me ) or are going to tune multiple vehicles and would like to tune your own engine, be it carb or EFI, you can hook up one of these puppys. Just have to get an O2 sensor bung welded in place.

 

[GerryLP]

I am sorry to hear that, my prayers are with you and your family.

Thanks for the thoughts and well wishes...

Ya know I just might be going up there in a couple of weeks.

Just let me know and I'll provide you with my phone number, so that we can make this work...

I know how frustrating career searching can be. I can relate, and please let me know how I can assist you.