i've got a bit of a problem and don't really know how to address the situation, it may be a simple fix but not really knowing much about carbs i don't really know where to start.
I've got a 1.7 gl with a solex 28-34 carb and i have fitted a high flow air filter.
It works great up to about half throttle giving a lovely induction whistle and pulls nicely, but my problem comes when i stick my foot down. There is a large drop in power (car stop accelerating and is held back) and a large amount of noise (sounds like a chav exhaust) is produced, causeing me to have to drive at no more than half throttle when i know the engines got more to offer.
I reckon the causes of the problem could be any number of things but the main areas i think it may be are
not enough fuel?
jet too small - drill out? what size?
increase fuel pressure? - adjustable regulator?
exhaust/manifold restriction? - new manifold+exhaust project?
too much air?
I have no clue where to start on the problem but any help would be greatly appriciated.
high flow air filter - 1.7 - solex carb
yes i've but a 'mushroom' style filter on (gauze and foam) and removed the old including the warm air intake.
I did this because the exhaust manifold is attached to the intake manifold and the carb so i thought there would be heat conduction between them which would be preventing the carb from freezing.
It also doesn't get any better with time when the under bonnet temperature has built up either? so i'm not sure if the carb is freezing, although i may be wrong.
I did this because the exhaust manifold is attached to the intake manifold and the carb so i thought there would be heat conduction between them which would be preventing the carb from freezing.
It also doesn't get any better with time when the under bonnet temperature has built up either? so i'm not sure if the carb is freezing, although i may be wrong.
I've been running without a warm air intake for the last 6months, aside from it taking a bit longer to warm up, the car seems a lot better for it (never thought I'd say that...)
How have you attached the mushroom to the carb? Sounds like an airleak, but I can't think why that would be giving you those symptoms, normally with an air leak it'll work best at full throttle.
The solex has a twin choke set up, and it sounds like when you are coming onto the second choke is when the issues are happening, any chance of a vid of whats happening?
How have you attached the mushroom to the carb? Sounds like an airleak, but I can't think why that would be giving you those symptoms, normally with an air leak it'll work best at full throttle.
The solex has a twin choke set up, and it sounds like when you are coming onto the second choke is when the issues are happening, any chance of a vid of whats happening?
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
thanks for the help....
it may be an air leak and i will check this, this weekend becasue apparently the solex carb has a vacum operated second choke? (was told this because the mk1 escort has the same/similar solex carb and it used to be a fairly common problem) so i will check and see if it is an air leak which is a simpler problem to address than a blockage somewhere which it could also be, but i belive it may be a long weekend which may result in me making a mechanical linkage for the second choke if it is vacum operated and not making enough of a depression......
it may be an air leak and i will check this, this weekend becasue apparently the solex carb has a vacum operated second choke? (was told this because the mk1 escort has the same/similar solex carb and it used to be a fairly common problem) so i will check and see if it is an air leak which is a simpler problem to address than a blockage somewhere which it could also be, but i belive it may be a long weekend which may result in me making a mechanical linkage for the second choke if it is vacum operated and not making enough of a depression......
Nah, sorry mate, it's already mechanical. I'm very dubious about the air leak, as full throttle the carb wants the most air of any position anyway. Can you get a vid of it?
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
The carb doesn't have an air leak.... i think? but i'm ruling that out
Tried to make a vid, but i only have a camera phone that gave a really bad quality video and couldn't zoom in ... I'll see if i can get a better one at the weekend.
But i think the problem is the second butterfly. it opens REALLY late! i would have thought it would come in at about half throttle but it comes in more like 3/4. The butterfly is also quite stiff so i think i will lubricate it and then see if i can adjust it a little to make it come in a bit earlier and see if that makes a difference
.... tho i'm not that sure, anyone got any ideas if its not that?
Tried to make a vid, but i only have a camera phone that gave a really bad quality video and couldn't zoom in
... I'll see if i can get a better one at the weekend. But i think the problem is the second butterfly. it opens REALLY late! i would have thought it would come in at about half throttle but it comes in more like 3/4. The butterfly is also quite stiff so i think i will lubricate it and then see if i can adjust it a little to make it come in a bit earlier and see if that makes a difference
.... tho i'm not that sure, anyone got any ideas if its not that?
It should come in VERY late, last 3/4 sounds about right. Out out interest, have you tried putting the old air box on and seeing if the problem goes away?
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast
i never really noticed it with the old air filter, but its the sound that brought my attention to the problem more.
....suppose it could also be a blockage in the carb somewhere. so i'll strip it down and blow it through with a compressor if i get a chance at the weekend and see if that has an effect.
....suppose it could also be a blockage in the carb somewhere. so i'll strip it down and blow it through with a compressor if i get a chance at the weekend and see if that has an effect.
Blown the carb out and it is making more power at full throttle but not quite enough, and the engines running a little rough still.
I took it to a local garage and they seemed to think something was up and said it could be the mixture but i would need to probably put it on a exhaust gas analyser to see what is coming out the other end.... sounded expensive but i will probably have to do it before my mot anyway.
I took it to a local garage and they seemed to think something was up and said it could be the mixture but i would need to probably put it on a exhaust gas analyser to see what is coming out the other end.... sounded expensive
but i will probably have to do it before my mot anyway.-
swordfish210
- Posts: 147
- Joined: 03 Nov 2007 05:18 pm
- Location: Chippenham
It's probably just running lean now because of the extra air flow and the original jets can't supply enough fuel. Let he garage put it on the EGA and see what it's kicking out. Try to aim for a 3% Co2 output and 800 hydrocarbon PPM, that should sort it.
Proud owner of a Crummy Volvo and a Ratty old 205
Its running lean on the second stage throttle. I bet the jets have been fiddled with and you've got the wrong sizes in there now, but there's also a chance that its blocked with some muck, so take the float chamber off, and take all the jets out, being very very careful not to mix them up. You should have the larger air jet and the smaller fuel jet in the primary system and the smaller air jet and the larger fuel jet in the secondary stage.
Get some clean neat petrol or carb cleaner and give them a good wash, and if you see any grit, use a very fine wire and poke it out, but the jets are very soft so if you poke anything too thick in there you'll enlarge the calibrated holes.
Then I agree with Swordfish, get it onto a gas analyser and see what its putting out. Specs are 0.5-2.0 % CO. but I'd aim for about 1.5% CO
Get some clean neat petrol or carb cleaner and give them a good wash, and if you see any grit, use a very fine wire and poke it out, but the jets are very soft so if you poke anything too thick in there you'll enlarge the calibrated holes.
Then I agree with Swordfish, get it onto a gas analyser and see what its putting out. Specs are 0.5-2.0 % CO. but I'd aim for about 1.5% CO
Afternoon all, just putting my oar in.
1. Secondary throttle flap operation is indeed mechanical only.
2. The secondary flap begins to open when the primary is just over 2/3 open.
3. The problem sounds very much mixture (weak) related - lack of the "std" air cleaner setup will give leaner mix (nice noises will always have their penalties) - but not, I feel, to the extent described here. It looks like the free flow filter is exacerbating an existing problem.
4. As Pettaw has suggested it may be a case of sticky fingers getting the jets wrong or ir may be that one or both of the Cisacs full load enrichment devices are not functioning. One relies on low and part load depression to hold closed a diaphram controling a valve. As the primary throttle butterfly reaches 1/2 - 3/4 open vacuum in the primary venturi fall away sufficient to allow the enrichment valve to open. This supplies extra fuel to the area above the main jets mixing area (around the air emulsion tubes). The valve diaphram cannot be holed as this would allow enrichment under all conditions but the valve may be stuck shut or the enrichment passage may be blocked. The second full enrichment is triggered by the greater air flow ocurring when the secondary throttle flap opens fully - a low pressure zone is formed in the top of the secondary venturi which draws extra fuel directly from the float chamber and into the second choke. Being purely airflow triggered the enrichment passage may be blocked OR perhaps the air filter currently fitted may have changed the air flow sufficiently to have moved, or prevented from forming, the low pressure zone that triggers this second enrichment system. (test this by reinstalling the factory air cleaner set up and see if the problem goes away).
Oar withdrawn - Mac.
1. Secondary throttle flap operation is indeed mechanical only.
2. The secondary flap begins to open when the primary is just over 2/3 open.
3. The problem sounds very much mixture (weak) related - lack of the "std" air cleaner setup will give leaner mix (nice noises will always have their penalties) - but not, I feel, to the extent described here. It looks like the free flow filter is exacerbating an existing problem.
4. As Pettaw has suggested it may be a case of sticky fingers getting the jets wrong or ir may be that one or both of the Cisacs full load enrichment devices are not functioning. One relies on low and part load depression to hold closed a diaphram controling a valve. As the primary throttle butterfly reaches 1/2 - 3/4 open vacuum in the primary venturi fall away sufficient to allow the enrichment valve to open. This supplies extra fuel to the area above the main jets mixing area (around the air emulsion tubes). The valve diaphram cannot be holed as this would allow enrichment under all conditions but the valve may be stuck shut or the enrichment passage may be blocked. The second full enrichment is triggered by the greater air flow ocurring when the secondary throttle flap opens fully - a low pressure zone is formed in the top of the secondary venturi which draws extra fuel directly from the float chamber and into the second choke. Being purely airflow triggered the enrichment passage may be blocked OR perhaps the air filter currently fitted may have changed the air flow sufficiently to have moved, or prevented from forming, the low pressure zone that triggers this second enrichment system. (test this by reinstalling the factory air cleaner set up and see if the problem goes away).
Oar withdrawn - Mac.