stevetzoid
|
| posted on 7/7/07 at 04:30 PM |
|
|
X/Flow Carb Problem.
Hi all, I race in the 750 Locost series and I am having a problem with the webber carb it's a 28/36 with twin 24 chokes I beleive, It appears to
be a common problem with a lot of the cars racing in the championship but either I am getting faster or the problem is getting worse.
When I come out of a high speed corner and put the hammer down the engine seems to flutter for a few seconds and then picks up again. It happened at
mallory at the hairpin, Cadwell at the rise onto the mountain and the hairpin and also out of Park corner the problem appears as though the engine is
out off fuel and then picks up again.
1, Regulator fitted 3 Psi
2 all filters fitted
3 baffled tank
4 red top fuel pump
5 webber filter fitted
6 float height checked
anyone with any thoughts because this is starting to cost me time and possibly points.
Regards Steve Evans Locost no 39.
|
|
|
|
|
GazzaP
|
| posted on 7/7/07 at 04:39 PM |
|
|
Hi steve
I have the same problem so i will await the answers...
Also of topic do you still have the old rollcage you took of your car?
Cheers
Gary
Locost #44
www.gmpmotorsport.co.uk
|
|
|
mark-wiring
|
| posted on 7/7/07 at 05:07 PM |
|
|
Ok been a few years since a played with carbs but ill have a punt.
Could it be that there is a problem caused by the float affecting the fuel level in the chamber and your finding that at the points on the track you
actually dont have the required fuel for the engine rpm's stored in the chamber.
What im saying is that during a lap the float shuts off the flow to the chamber thus leaving you without the required fuel for that moment of flutter
then obviously it catch's up and off you go again.
Dont know the carbs you have so this won't work if you dont have a fuel return to the tank. If you have then try this;
Take the float out.
http://www.v10viento.co.uk
Have to recommend
http://www.extraefi.co.uk/
For all Megasquirt needs
|
|
|
stevetzoid
|
| posted on 7/7/07 at 05:35 PM |
|
|
Roll cage
Hi Gary, I have had a couple of people after the cage but no one has come up and collected it so I still have it.
Regards Steve no 39.
|
|
|
gazza285
|
| posted on 7/7/07 at 08:38 PM |
|
|
Open up the plug gap a bit.
DO NOT PUT ON KNOB OR BOLLOCKS!
|
|
|
britishtrident
|
| posted on 9/7/07 at 09:33 AM |
|
|
Fuel surge either in the tank or the float chamber
First try running with more fuel in the tank
Also check the accelerator pumps are working.
Try running with standard fuel pump and no regulator.
[Edited on 9/7/07 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
NS Dev
|
| posted on 9/7/07 at 11:56 AM |
|
|
I don't race my locost and it doesn't have a crossflow in it so I am not really qualified to answer, the chap to ask is Matt Gilmour
(Procomp)
However, it did occur to me that if you are running that carb and manifold setup, is it not angled a touch to allow for the angle of the engine in the
escort (down at the rear, so the carb is angled up at the rear?? )
If so, could it be that you effectively have a low float height now the engine is installed level? I know you have checked the float height but I
assume that is as per haynes for the escort, so in reality it will not be right if the angle is changed??
Might be worth bending a spare float tab slightly to get a touch more float height and see if it helps. Keep your existing one as a spare so you are
not panicking at a meeting!
edit, P.S. I also know that many run the std carb at the wrong angle fine on the road, but if it is this problem it may be that the slightly low fuel
level only becomes a problem on the track where consumption is high and corners are hard.
[Edited on 9/7/07 by NS Dev]
[Edited on 9/7/07 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
|
|
|
Terrapin_racing
|
 posted on 9/7/07 at 01:01 PM |
|
|
I would suspect the carb float height causing lean mix on heavy cornering.
Set it at manufacturers height as a starting point to optimise the float level. Too low of a fuel level can cause a cough or missfire while heavy
cornering but too high of a fuel level can cause flooding and a cough or missfire while cornering Experimenting with this height may help to overcome
the problem. Trial n error I'm affraid
|
|
|
stevetzoid
|
| posted on 9/7/07 at 09:40 PM |
|
|
Thanks for the info guys, the only question is what about hills? up and down, but tonight I checked the float level and it does look a little bit low,
however I checked the engine sitting on the drive and I noticed if I open the throttle smoothly the engine picks up ok, if I jam open the throttle
from 750 rpm then the engine is a bit slow to pick up is this just because it rely's on a vacumn ie cause and effect then reaction? in other
words open the throttle smoothly rather than a switch on off.
|
|
|
britishtrident
|
| posted on 10/7/07 at 06:59 AM |
|
|
From your description the engine is running weak, check the accelerator pump is supply a good squirt of fuel when flooring the throttle.
Also clean all the carb jets.
I think it may not be helped by the carb jetting, in it original home in the front of an Escort your carb was fed with hot air through a airfilter
which was large enough to hold a fair ammount of fuel vapour dropplets which get sucked back in when the throttle is floored.
[Edited on 10/7/07 by britishtrident]
[Edited on 10/7/07 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
D Beddows
|
| posted on 10/7/07 at 09:12 AM |
|
|
The answer I'm afraid is that most old dgv carbs do this to some degree or another and 9 times out of 10 it's nothing to do with fuel
surge/pressure or float levels. In fact fuel regulators cause more problems than they solve in the usual 750MC set up in my experience.
The foolproof solution is to buy a new one (although the ones they make now aren't the same quality of the old ones - and they're at least
a couple of hundred quid) but I got so fed up taking apart and rebuilding the d*mn things it seemed the way to go.
The reason for your problem is probably as detailed at
http://www.theautoist.com/weber_carb.htm
The link to the diagram doesn't work but this one does (and the numbering is the same btw)
http://www.carburetion.com/diags/3236DGVDiaginfo.asp
|
|
|
