Hi guys.
Still trying to work through this lean problem I've got with my supercharged motor. I've disconnected the blower now, so it's just a low compression standard aspirated engine. However it's still runs lean when I accelerate. On tickover it's fine. But when I accelerate, even if it's only a bit, it goes completely lean straightaway.
Any ideas guys.
The fuel pressure's set at 3psi, carbs are dual 48mm drla's.
It could well be that some jets are blocked, give me a Solex and I'm well away, but with these DRLA's I haven't a clue where anything is. Please help.....
Q&A 's
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bad62bug
- Posts: 288
- Joined: Sun Dec 31, 2000 12:01 am
Q&A \'s
Go to this site and ask for a good starting point for your motor specs. Theirs a lot of good people there http://www.cal-look.com/index2.html
P.s. the more info they have from you the better the help.
P.s. the more info they have from you the better the help.
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Muffler Mike
- Posts: 3186
- Joined: Tue Feb 20, 2001 12:01 am
Q&A \'s
just a thought here. you have fuel pressure ok, but do you have volume??????????????
pressure and volume are two completly different things.
pressure and volume are two completly different things.
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Plasticfantastic
Q&A \'s
Don't know of an exact way to check (I'm sure there's a high priced gizmo) but let me throw out some things you probably already thought of;
What pump are you using...GPH's?
Any chance of a voltage drop at the pump?
I KNOW you're not using stock diameter fuel line...any bends too sharp?.. HIGH volume filter?
The last thing that's been nagging me...any chance once it heats up you're getting what we call over here.."vapor lock"??
(fuel boiling in the line which would cause it to die not just lean out)
[This message has been edited by Plasticfantastic (edited 06-10-2001).]
What pump are you using...GPH's?
Any chance of a voltage drop at the pump?
I KNOW you're not using stock diameter fuel line...any bends too sharp?.. HIGH volume filter?
The last thing that's been nagging me...any chance once it heats up you're getting what we call over here.."vapor lock"??
(fuel boiling in the line which would cause it to die not just lean out)
[This message has been edited by Plasticfantastic (edited 06-10-2001).]
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moggy
- Posts: 651
- Joined: Fri Mar 09, 2001 12:01 am
Q&A \'s
Pumps a FI unit, filter is a high volume unit. All fuel piping is sized right. I've run out of ideas so I'm taking it down to a rolling road just to double check the jetting is correct and get a second (experienced) opinion on the whole thing. I'll let you all know the results.... Thanks for all the input.
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Chuck Schneider
- Posts: 345
- Joined: Wed Mar 21, 2001 12:01 am
Q&A \'s
Moggy, how are you using a FI pump with carbs. The fuel injection pump is made for a high pressure.
The jets are located on the top of the carbs. You should be using a turbo emulsion tube to richen it up in the higher rpm's. If it idles good go bigger on the main fuel jets. If the idle and the mains are too lean then you can go smaller on the air correction jets. The idles use the air correction jet to get air on dellortos.
You really need to get a air fuel gauge and weld in an 02 sensor to actually see what is going on with the A/F ratio. If you don't have a gauge then you are just guessing and don't expect the world if your guessing when jetting an engine.
The jets are located on the top of the carbs. You should be using a turbo emulsion tube to richen it up in the higher rpm's. If it idles good go bigger on the main fuel jets. If the idle and the mains are too lean then you can go smaller on the air correction jets. The idles use the air correction jet to get air on dellortos.
You really need to get a air fuel gauge and weld in an 02 sensor to actually see what is going on with the A/F ratio. If you don't have a gauge then you are just guessing and don't expect the world if your guessing when jetting an engine.
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moggy
- Posts: 651
- Joined: Fri Mar 09, 2001 12:01 am
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Just got back from the rolling road...and don't I feel stupid (no change there then)
Firstly we compared my a/f guage to the one on the rolling road and we found that I got the wire the wrong way around on the a/f display so when it was showing lean it was actually rich, DOH! After that was sorted, it was still running slightly rich and had a bit of a flat spot at 3800rpm. The guy put 170 mains on replacing the 180's I had on there. this solved the problem.
The car now runs like a dream. It registered 163bhp at 6000rpm at the wheels. With 6psi boost and 24degrees advance, I can't wait for August now, when I crank it up to 10psi, put water injection on it and advance it to 31 degrees (200 at the wheels I hope). But for now I'm just gonna enjoy what I've got for the rest of the summer.
Oh and just for reference, I drived 50 miles there, 50 miles back, oil temp never got over 225 farenheit (110 degrees C) cruising at about 65-70mph.
I'm off to spank some BMW's, see ya.....
[This message has been edited by moggy (edited 06-15-2001).]
Firstly we compared my a/f guage to the one on the rolling road and we found that I got the wire the wrong way around on the a/f display so when it was showing lean it was actually rich, DOH! After that was sorted, it was still running slightly rich and had a bit of a flat spot at 3800rpm. The guy put 170 mains on replacing the 180's I had on there. this solved the problem.
The car now runs like a dream. It registered 163bhp at 6000rpm at the wheels. With 6psi boost and 24degrees advance, I can't wait for August now, when I crank it up to 10psi, put water injection on it and advance it to 31 degrees (200 at the wheels I hope). But for now I'm just gonna enjoy what I've got for the rest of the summer.
Oh and just for reference, I drived 50 miles there, 50 miles back, oil temp never got over 225 farenheit (110 degrees C) cruising at about 65-70mph.
I'm off to spank some BMW's, see ya.....
[This message has been edited by moggy (edited 06-15-2001).]
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jeivw
- Posts: 2
- Joined: Fri Jun 15, 2001 12:01 am
Q&A \'s
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by moggy:
<B>Hi guys.
Still trying to work through this lean problem I've got with my supercharged motor. I've disconnected the blower now, so it's just a low compression standard aspirated engine. However it's still runs lean when I accelerate. On tickover it's fine. But when I accelerate, even if it's only a bit, it goes completely lean straightaway.
Any ideas guys.
The fuel pressure's set at 3psi, carbs are dual 48mm drla's.
It could well be that some jets are blocked, give me a Solex and I'm well away, but with these DRLA's I haven't a clue where anything is. Please help.....</B><HR></BLOCKQUOTE>
<B>Hi guys.
Still trying to work through this lean problem I've got with my supercharged motor. I've disconnected the blower now, so it's just a low compression standard aspirated engine. However it's still runs lean when I accelerate. On tickover it's fine. But when I accelerate, even if it's only a bit, it goes completely lean straightaway.
Any ideas guys.
The fuel pressure's set at 3psi, carbs are dual 48mm drla's.
It could well be that some jets are blocked, give me a Solex and I'm well away, but with these DRLA's I haven't a clue where anything is. Please help.....</B><HR></BLOCKQUOTE>
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Matt Keene
- Posts: 406
- Joined: Wed Apr 25, 2001 1:01 am
Q&A \'s
See you at Gary's Picknic on Sunday? (North Weald) How 'bout a head 2 head? You are producing exactly the same rear wheel horsepower as my Oval so it would be fun to see how they compare...