| Author |  Topic  | |
ratty
V4 Fanatic
United Kingdom
340 Posts |  Posted - 25 May 2022 : 18:26:37  
| | Can someone tell me please what the venturi size is for the standard Fomoco carb fitted to the Saab 96 V4? Also the auxiliary choke size? |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 26 May 2022 : 13:22:50
| Nigel, I measured one for you, venturi is 25mm, but since different variations of this carb have been used by Saab over the years there may be variations. I think FoMoCos came with 23–27mm venturis (in general, not specifically for Saabs). Which part do you mean by "auxiliary choke"?
www.saabv4.com |  |
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ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 26 May 2022 : 23:00:31
| Melle I meant Auxiliary Venturi as on weber's. Maybe they don't have one. The one Saab has standard fomoco and has more bottom end torque initially than the the trials with 32/36. After 3000 rpm it is totally the other way round. 25mm makes sense, giving greater air speed at lower revs I presume. I have found a totally different jet setting for the 32/36 used by Saab. Have ordered some new jets so will give the Saab setting a go hopefully this weekend. Will let you know. What are the choke sizes and jets you have on your 28/36 as a matter of interest? PS. I don't have access to the fomoco Saab at present hence my first question. Also have a weber 34 dgas, same as the 38 dgas, which cologne V6 perform very well on, to play with. Maybe this is the ultimate torque weber I am looking for? All good fun. Also have a 28/36 as well.
nigel martin-oakley | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 27 May 2022 : 09:47:26
| FoMoCos don't have an aux venturi like Webers. I don't know the jetting of my 28/36 DCD off the top of my head (can look it up next month when I'm in my workshop), but from memory it has a 24mm primary venturi and a 27 secondary. This is perhaps a little unconventional as most seem to use venturis that are much closer together in diameter (usually 26/27 on V4s I think). I've set my engine up on the road and with the help of an Innovate MTX-L lambda gauge, and I'm very happy with how it pulls through the rev range. Quick enough off the mark and no noticeable flat spots, it only runs a little too lean on the overrun to my taste, I dislike the resulting exhaust popping that some people think is cool. Current engine is a standard 1.5 with Jetex exhaust with home made front Y-section and Bosch Hall ignition, not used for race/ rally etc.
What Saab DGV settings did you find? I wasn't aware Saab used DGVs, from memory, the S&R catalogue only mentions the 40 DFI and perhaps the Solex 32 TDID? Have you ever had your cars on the rollers?
www.saabv4.com | |
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Woody
V4 Guru
United Kingdom
2764 Posts | |
ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 27 May 2022 : 22:42:09
| | Tried new jets today. Bottom end pick up is better. Will come back tomorrow with settings etc. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 28 May 2022 : 14:05:03
| Nigel, do you have John Passini's Weber book? Taught me a lot.
www.saabv4.com | |
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ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 29 May 2022 : 09:13:56
| Melle, no I don't but will have in a couple of days! Woody thanks for your 28/36 settings again although I feel that Melle and the smaller choke size on the primary is a better bet for most people. And of course for classic trialling torque, bottom end pick up is very important as it is for banger and stock car racing. So to recap I bought the 32/36 new for an everyday economical carb. This it is but only after I fitted a fuel pressure regulator. I swapped the mechanical pump for a low pressure facet 1 to 3 lbs. I did this because the Fomoco was stalling on very steep rough hills. As it turned out it was the Fomoco at fault not the pump so I bought a used 28/36 to try. This was ok but drank fuel. Both the Fomoco and the 28/36 ran fine without a fuel regulator. Then I bought the 32/36 and it seemed to run ok but on odd occasions it would run rich, falter and then seemingly run ok again. Then it seized an inlet valve, then another. It turned out to be too much pressure. 3 lbs is too much pressure for my 32/36 but was ok for the Fomoco and 28/36.Strange. As one of my trialling friends said I always fit a fuel regulator and have never had a problem. There's the moral.
So back to 32/36 the standard jetting was ok for average road use.
Sizes :- Choke: 26 27 : Mains: 140 135 : Idle: 55 50 : Air. Corr.: 165 160 :Emuls.F50 F6. All bog standard.
Went to rolling road, set up timing on new 123 ignition and replaced main jets with 145 and 135.
This gave an output of 77 BHP and a nice flat torque curve between 2000 RPM and 4000 RPM peaking at 97 ft/lbs.
However I am still not happy with bottom end pick up particularly below 2500 RPM. The other day I came across some new jet settings for the 32/36, quite different. This was on 'carbparts.eu jetting table'.
New sizes :- Mains: 150 135 : Idle 55 50 : Air Corr.: 160 185 :Emuls.: F6 F6. This seems to work well. Pulls better after 3000 RPM and has better pick up low down. I will be sticking with these settings for the moment.
I still feel though the 34 DGAS Weber I have with its 24mm chokes will be the best. All I have to do is rebuild it and re jet it.
Also have fitted Corsa power steering. Absolutely transforms the car with either wide wheels and or very low tyre pressures, or both! I have managed to keep the original steering wheel assembly and gearchange so still looks like 'proper Saab '. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 29 May 2022 : 15:51:45
| Found my current 28/36 DCD jetting table:
Primary | Secondary
Main Jet 130 | 155
Idle Jet 60 | 70
Emulsion Tubes F30 | F30
Air Corrector 220 | 180
Accelerator Pump Jet 70
Needle Valve 175
Venturi 24 | 27
Auxiliary Venturi 4.5 | 4.5
Starting Air Jet 150
Starting Fuel Jet 150F1
Nigel (and anyone else who wants it), if you email me at saabv4[at]saabv4[dot]com I'll send you a PDF of the Weber factory tuning manual.
What control box did you use for the power steering? I have an Wagon R+/ Agila column ready to go in the 95 when I eventually get to it. Very interested in seeing some pics of your set-up.
www.saabv4.com | |
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ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 29 May 2022 : 17:48:11
| Thanks for that jetting table. Would love to know what it produces on the rolling road. Will email for tuning manual. What is your fuel consumption like driving lightly? I used to get between 22 to 28 MPG with my 28/36. The 32/36 was returning 30 to 40 mpg. I haven't managed a long drive yet with the new jets.
Got the control box from jimny bits ebay. Corsa control box. £20.00 approx. I think they are all very similar these days. You will have to get one which is matched to Wagon R ECU set up. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 29 May 2022 : 19:25:56
| I've never had it on the rollers. I have a part-built brand new engine for the 96, and I plan to have it on the rolling road with that after breaking it in. I'm going to use the current (known good) engine for my K-Jet conversion, that should see some progress this summer hopefully. In reality I only have about 1–2 weeks of workshop time most years and lots of other projects too, so don't hold your breath!
I'm not exactly sure about economy to be honest. Will see if I can do some miles when I'm in NL this summer and do some mileage calcs.
I'll check out eBay for an epas control box.
www.saabv4.com | |
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ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 29 May 2022 : 21:50:38
| The rollers is the only way to know exactly what you have got. And then when I hope I have made an improvement, the rolling road will prove me right! You know I think most people think that using a rolling road is very expensive. Not necessarily if you use the right guy, and get to know him.
As a matter of interest I don't run a modern these days. I have 2 V4's and a 2cv. That is it ! I love it.
Projects I have this summer is rebuild 2 gearboxes v4, strip and rebuild 2cv steering rack, strip engine, minor rebuild 2cv, work out cheapest best super charger for v4 for trialling and having fun. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 30 May 2022 : 08:31:27
| I don't race or rally my cars and I don't really care about ultimate performance, I just want engines that pull nicely throughout the rev range and don't cost an arm and a leg to build. The only reason I want my 96 on the rollers at some point is that I'm curious as to what my slightly tickled but otherwise standard V4s make in comparison with £££ big valve, fast cam etc. engines built by pros. (don't get me wrong, theirs will produce more HP, just curious to see the difference.) In the end HP is in itself a rather meaningless figure anyway, and as a late friend who rallied a bog standard V4 always put it, 'it's fearlessness when cornering that wins races, not money spent on the car'.
I'm really happy with the lambda gauge (in combination with a rev counter) in the 96 as it has made it has made identifying the cause of flat spots etc. so much easier. I also found it invaluable to identify blocked jets etc.
Keep us posted on your supercharging adventures Nigel, that will certainly be interesting!
www.saabv4.com | |
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ratty
V4 Fanatic
United Kingdom
340 Posts | Posted - 30 May 2022 : 16:52:24
| I don't race or rally my cars, can't afford it! Yes I do classic trialling and it is a big challenge to be fairly successful using a production car. The last Tamar trial I entered last year cost me in total under a hundred pounds. Not bad for a days entertainment with 15+ hills to try and climb.
I have only just started to use the rolling road and now for the first time I know what I have got. All the improvements I have done myself with help from a few friends. Some of the Peugeot's and the golf's produce up to 200 BHP with a similar amount of torque. But both Karl with his 1700cc car and myself are not far behind. So if I have made some improvements then I will put it on the rollers to see what increases I have.
As Enzo Ferrari said 'BHP sells motor cars, Torque wins races'!
I'm really interested in your lambda gauge, what type, where is it fitted and how you use it to tune your carb. etc. any info would be appreciated.
Supercharging won't happen for a couple of years. But I intend to do it. One big question is do you blow it before or after the carb.? Both can be done. The beauty of supercharging is you have very controllable instant power right through the rev. range. Ideal for my sport. | |
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| | Topic | |
Fomoco carb.
