Another R17 owner planning to upgrade

[dauphproto]

40's generally work better than 45's on a road car. The 45's available had poor positioning of the progression holes, as they were originally meant for big capacity motors, so not great on 15-1600cc.
One of the best 40's around is the DCOE 2 an old Alfa Romeo design which works well in the 13-1600cc. This is the Carb supplied as the DCOE 151 nowadays. It is also fitted with idle air by pass screws which the original did not, all aftermarket carbs are supplied with these now. There are several versions of 45 available today aimed at specific 2ltr.16v application which progress much better than the original 9 and 13, still a bit overkill for a road car
Most people don't realise that the bodies were drilled for their specific application by Weber on oe supplied cars. The Dellorto carb is a much more adjustable device which gives better tuneability, but won't make the outright power of the Weber, which is odd, but true. It also does not have the range of spares available either nowadays.
Generally the fuel pump should be as close to the tank as possible and lower than the fuel level to keep it primed, more or less as you have done. There should be a pressure control (filterking type fitted as close to the carbs as possible) This gives a higher pressure from pump to carbs,anything up to 10 psi, but does not stress the needle valves, as they are only getting 2-4 psi. You are looking for a Tachometric relay which will cut off in the event of engine stop. Most cars use them today as fuel pump relays, but I'm old enough to remember when cars didn't generally have electric pumps.

 

[Shoji]

Just dummied it up for a photo. It is positioned about the same height as the exit pipes from the tank. I think a wire connector should be here on this side of the floor as well. Pipes will be aligned later for rattles and looks. being ali their easy. You'll note I still added the return line and the crinkle in the anodisedbends.
Thanks for the wise notes from dauphproto. I have those 151's and mine are drilled with an extra progression hole. I think I did a thread or posted on here about a method.

 

[Sunroof]

Interestingly the Weber jetting for a 125 bhp 12 G and the 160 bhp 12G, according to the workshop manual, are the same. Perhaps you have to decide whether the car is a road car or race car as then all the settings including the venturi will change and as the main and air jets relate directly to the venturi size so they will also change. Also interestingly the accelerator pump jet has two uses. Until the main jet comes in the car runs on progression holes, the idle jet and a dribble from the accelerator pump so these also come in a couple of sizes.

 

[dauphproto]

Interestingly the Weber jetting for a 125 bhp 12 G and the 160 bhp 12G, according to the workshop manual, are the same. Perhaps you have to decide whether the car is a road car or race car as then all the settings including the venturi will change and as the main and air jets relate directly to the venturi size so they will also change. Also interestingly the accelerator pump jet has two uses. Until the main jet comes in the car runs on progression holes, the idle jet and a dribble from the accelerator pump so these also come in a couple of sizes.

That would tend to suggest that they are not the ideal settings. Lots of strange things happen,that are not in the textbooks in the real world. If you get a chance to look down the venturi on a side draught at full noise, on the dyno, you will see the engine pull fuel from everywhere it can Idles, progression holes pumps and the mains. This is why it can be usual to trim the air correctors on an Engine that is going rich right at the top. The text book tends to tell you the engine pulls from the idle hole at tickover (the one you adjust with a screwdriver) This is receiving emulsion from the idle/ idle air corrector, this same jet also supplies the holes in the progression well. This can be the case right up to 3000 rpm when the main circuit starts to come in, you can change the point this happens by changing the main emulsion tubes, Weber do them numbered, but not in any order. The acc pump jet comes in many sizes and covers the gap between idles and mains, plus the pump discharge jet can be changed in the base of the fuel well. This alters the duration of the acceleration pump, by returning fuel to the well rather than squirting it all down the venturi. Every Renault I have had didn't like big pumps, even the 1700 is only on a 40 with a large discharge to really limit its duration (35 is the smallest)
I recently witnessed a 1500 cc single cam Fiat engine, which had been set up on the dyno, but had given less than ideal numbers, with a poor spread overall. It was pretty top endy and was poor below 4000 rpm.. It is a Fiat X19 circuit race car, so driveability was not high on the agenda. However my Mate had a theory that the exhaust manifold primaries were too large diameter and the Exhaust was too short. They had another manifold made up with Inch and seven eighths primaries in place of the Two and a quarter originals and they put another pass into the system with another 2 180 degree bends. They had added about a metre of exhaust and allowing a third of a metre for a 90 degree bend the theoretical increase was more like 2.3metres.
To say I was sceptical would be an understatement, so I accepted the invite to the rolling road session to see how it would be. On the first power run it was rich across the range, really rich.
Long story short it ended up down 10 on the Mains from 145 to 135 and it was good across the board. That is a monumental change to the fuelling. It also made 5 BHP more at the top than before, but sensationally was up 14 BHP at 4000rpm.
Having driven it in both guises it might as well be a different engine.
The only difference made was the exhaust changes, but it now scavenges much better than before, the air speed is so much higher, that the fuel jet had to be reduced, we tried several other changes, but the first guy who dynoed it, really knows his stuff and had the slope correct. We also had tried adjusting the ignition timing, but it was best where it had been previously set
I am always fascinated by Engine set up. It is best to try to imagine with a competiton motor that it is actually alive. It is the closest a machine gets to actually be Living.
The numbers tell the story. The engine was shy before Prompting the drive to make the changes. It came off the rollers at more or less the magic 100 BHP/litre for a 2 valve engine.
The only way to know if the Motor is right is a run on the dyno if you can or a session on the rollers if you can't. It's much easier to make changes on the dyno without the car getting in the way, plus being a hard connection there is less room for errors.
It's great fun watching other people spend large sums of money and get results, I can see why my Mate does what he does.

 

[geckoeng]

That would tend to suggest that they are not the ideal settings. Lots of strange things happen,that are not in the textbooks in the real world. If you get a chance to look down the venturi on a side draught at full noise, on the dyno, you will see the engine pull fuel from everywhere it can Idles, progression holes pumps and the mains. This is why it can be usual to trim the air correctors on an Engine that is going rich right at the top. The text book tends to tell you the engine pulls from the idle hole at tickover (the one you adjust with a screwdriver) This is receiving emulsion from the idle/ idle air corrector, this same jet also supplies the holes in the progression well. This can be the case right up to 3000 rpm when the main circuit starts to come in, you can change the point this happens by changing the main emulsion tubes, Weber do them numbered, but not in any order. The acc pump jet comes in many sizes and covers the gap between idles and mains, plus the pump discharge jet can be changed in the base of the fuel well. This alters the duration of the acceleration pump, by returning fuel to the well rather than squirting it all down the venturi. Every Renault I have had didn't like big pumps, even the 1700 is only on a 40 with a large discharge to really limit its duration (35 is the smallest)
I recently witnessed a 1500 cc single cam Fiat engine, which had been set up on the dyno, but had given less than ideal numbers, with a poor spread overall. It was pretty top endy and was poor below 4000 rpm.. It is a Fiat X19 circuit race car, so driveability was not high on the agenda. However my Mate had a theory that the exhaust manifold primaries were too large diameter and the Exhaust was too short. They had another manifold made up with Inch and seven eighths primaries in place of the Two and a quarter originals and they put another pass into the system with another 2 180 degree bends. They had added about a metre of exhaust and allowing a third of a metre for a 90 degree bend the theoretical increase was more like 2.3metres.
To say I was sceptical would be an understatement, so I accepted the invite to the rolling road session to see how it would be. On the first power run it was rich across the range, really rich.
Long story short it ended up down 10 on the Mains from 145 to 135 and it was good across the board. That is a monumental change to the fuelling. It also made 5 BHP more at the top than before, but sensationally was up 14 BHP at 4000rpm.
Having driven it in both guises it might as well be a different engine.
The only difference made was the exhaust changes, but it now scavenges much better than before, the air speed is so much higher, that the fuel jet had to be reduced, we tried several other changes, but the first guy who dynoed it, really knows his stuff and had the slope correct. We also had tried adjusting the ignition timing, but it was best where it had been previously set
I am always fascinated by Engine set up. It is best to try to imagine with a competiton motor that it is actually alive. It is the closest a machine gets to actually be Living.
The numbers tell the story. The engine was shy before Prompting the drive to make the changes. It came off the rollers at more or less the magic 100 BHP/litre for a 2 valve engine.
The only way to know if the Motor is right is a run on the dyno if you can or a session on the rollers if you can't. It's much easier to make changes on the dyno without the car getting in the way, plus being a hard connection there is less room for errors.
It's great fun watching other people spend large sums of money and get results, I can see why my Mate does what he does.

Mr "Dauphproto" Magic tale I will admit !!! When in UK I used to witness some evenings in the Kenny Roberts MotoGP dyno room. My friend who worked the dyno used to do testing on carburetor engines as well. As the Weber was easy to jet in place he would run one choke on a 500 single. Exhausts made huge changes with diam and length. And I learned good Exhaust velocity was needed for good driving torque and HP feel.

Ray

 

[COL]

That would tend to suggest that they are not the ideal settings. Lots of strange things happen,that are not in the textbooks in the real world. If you get a chance to look down the venturi on a side draught at full noise, on the dyno, you will see the engine pull fuel from everywhere it can Idles, progression holes pumps and the mains. This is why it can be usual to trim the air correctors on an Engine that is going rich right at the top. The text book tends to tell you the engine pulls from the idle hole at tickover (the one you adjust with a screwdriver) This is receiving emulsion from the idle/ idle air corrector, this same jet also supplies the holes in the progression well. This can be the case right up to 3000 rpm when the main circuit starts to come in, you can change the point this happens by changing the main emulsion tubes, Weber do them numbered, but not in any order. The acc pump jet comes in many sizes and covers the gap between idles and mains, plus the pump discharge jet can be changed in the base of the fuel well. This alters the duration of the acceleration pump, by returning fuel to the well rather than squirting it all down the venturi. Every Renault I have had didn't like big pumps, even the 1700 is only on a 40 with a large discharge to really limit its duration (35 is the smallest)
I recently witnessed a 1500 cc single cam Fiat engine, which had been set up on the dyno, but had given less than ideal numbers, with a poor spread overall. It was pretty top endy and was poor below 4000 rpm.. It is a Fiat X19 circuit race car, so driveability was not high on the agenda. However my Mate had a theory that the exhaust manifold primaries were too large diameter and the Exhaust was too short. They had another manifold made up with Inch and seven eighths primaries in place of the Two and a quarter originals and they put another pass into the system with another 2 180 degree bends. They had added about a metre of exhaust and allowing a third of a metre for a 90 degree bend the theoretical increase was more like 2.3metres.
To say I was sceptical would be an understatement, so I accepted the invite to the rolling road session to see how it would be. On the first power run it was rich across the range, really rich.
Long story short it ended up down 10 on the Mains from 145 to 135 and it was good across the board. That is a monumental change to the fuelling. It also made 5 BHP more at the top than before, but sensationally was up 14 BHP at 4000rpm.
Having driven it in both guises it might as well be a different engine.
The only difference made was the exhaust changes, but it now scavenges much better than before, the air speed is so much higher, that the fuel jet had to be reduced, we tried several other changes, but the first guy who dynoed it, really knows his stuff and had the slope correct. We also had tried adjusting the ignition timing, but it was best where it had been previously set
I am always fascinated by Engine set up. It is best to try to imagine with a competiton motor that it is actually alive. It is the closest a machine gets to actually be Living.
The numbers tell the story. The engine was shy before Prompting the drive to make the changes. It came off the rollers at more or less the magic 100 BHP/litre for a 2 valve engine.
The only way to know if the Motor is right is a run on the dyno if you can or a session on the rollers if you can't. It's much easier to make changes on the dyno without the car getting in the way, plus being a hard connection there is less room for errors.
It's great fun watching other people spend large sums of money and get results, I can see why my Mate does what he does.

I reckon a good dyno guy is worth his weight in gold, I have spent many hours playing with Webers, ignition timing and road testing and get nowhere fast. I find you are better to get to the stage where you can drive it to the dyno and get it setup properly. A few hours on the dyno is money well spent. Do a few nights overtime to pay the dyno guy, better results and less frustrating.