Webers or Fuel Injection

[colin gray]

Hello Colin,
"I find your comments very enlightening as I was also considering injection, however straight pipes to the airbox and possibly SU's or a setup on a rolling road for the Strombergs looks like a better option all being considered."
If you mount two pipes with a bigger diamter to the airfilterboxes and you make a hole of 45 mm longline in the two front silencers, the mixture is becomming weaker. Unfortunately too weak.
Can can't cure this with "turning srews" at the carb. You need 4 carb needles, which are less thick in the upper area (thin end of needle), the the small round cleft between the carb-needle and the jet is a very little bit bigger. Through thius bigger cleft, more gas can flow.
You need to measure the mixture, that you can see, if it is okay. You have to know, how much is okay. There is a book from Des Hammill "Tuning the SU-Cabrs). Buy thuis book !!! In this book he has a very clear desciption, how to change to shape of the needle, if you prepare a motor with different air-filters and different exhaust system for racing.
To measure the mixture, you have to mount a wide-band lambda measuring system into the car. I bought one from 'innovate' for roundabout 170 pound. You can drive with the car and can see JUST in time, how the mixture is. Depending of the position of the lambda-"Sonde' in the exhaust system, you can check one carb or two carbs of one side of the motor.
Invest this money and effort. The result for my car was, that in the rev range between 2000 und 4000 rpm, the motors with carbs was much stronger than the same motor of a friends car with EFI. I have done this test two times with the same result. 5,3 Vs 5,3 and later 6,0 vs 6,0.
If you don't want to shape needles with 1000er sanding paper, you can mount 4 SU Carbs. For SU carbs you maybe can find some needles which will "fit" and produce in different rev ranges and different throttle positions the correct mixture. S U offers 700 different needles.
I have produces 4 needles by myself It was a lot of work. But at the end I had a good result.
If you do all this correct, you never will miss EFI on your V12. Together with the 2,88 plus the long Getrag my 6,0 L HE car has a gas consumption of roundabout 19 mpg when cruising. Again no need for EFI.
'Empe'.
Regards Wolfgang Gatza

Hi Woolfi, Des Hammill book on its way. To read each Carburettor via a Lambda am I right to assume 4 x Lambda's are required 1 x in each in each downpipe? I guess it would then be Multiple gauges or some sort of switching system.

My E is purely a road car so I am just looking for better efficiency and cleaner running as I am aware in standard trim although a joy to drive the V12 is considerably compromised in the breathing department.

I would be happy to try re shaping the needles and I have all grades of abrasive paper down to 1600#, is it a case of needle in the Lathe or a small drill (Dremel) in the vice? and is the method via trial and error until the Lambda reading is good?
Regards
Colin

[Barry]

Hi Woolfi,
Whilst I respect your knowledge and expertise on things V12, I have to say I think you are wrong and my car is the proof! Fuel injection with absolutely no bugs, and more power than any carb equipped car....
The LPG idea is really interesting, and I wait with interest to read more on that topic.
Best Wishes
Barry

[MarekH]

All Woolfi has done is recognise that changing either the induction or exhaust, i.e. the airflow, means that a change in fueling is also needed. Using a lambda sensor means it is possible to tailor the the fuel flow to the airflow. If you look in the appendix to the Stromberg Carburettor Book, the needles all divided into ten and their diameters are listed as a table. (Roger Bywater has done the same as Woolfi, changing the fueling to match his modified exhaust and induction system).

Contrary to what you might think, merely fuel injecting a car doesn't increase the power of the engine*, but it does enable you (meaning it enabled Roger) to map the fuel delivery even more accurately than by needle, even with an unsophisticated and obselete batch fired system like the Lucas 16cu which can't be monitored or adjusted by the end user.

I note both of you are still running the old Lucas distributor.

You can put four lambda sensors onto the downpipes if you wish. This is very marginal for distance away from the exhaust ports, so it is best done with short (up to 1") spacer tubes between the downpipes and sensors to take the plugs just out of the direct exhaust flow. My setup has been running like this for about ten years now.

If you really want unlock more "free" power and economy, then fit a mapped ignition and run lpg. It's a higher octane fuel and is about half the price of petrol. If you look at the Zytec XJS maps I posted on jag-lovers.com, you'll see there is a sharp divide between a lean cruise region and medium to heavy load power region on the ignition maps, so you can have your cake and eat it and experiment to your heart's desire if your ECU allows you to make those changes yourself.

kind regards
Marek

*you'll both be running equally rich, at full throttle and max revs

[max-it-out]

The carb needles are made of quite a soft metal ( looks like brass ) so you need to be careful when using sandpaper that you don`t thin them too much - once its gone , it can`t be put back on
I discovered my Strombergs were probably from a TR6 and the needles ( B1AF ) gave too lean a mixture so poor acceleration . The first try at thinning the needles gave much better throttle response , but sooty black plugs , so 2 new needles had to be ordered . A much more cautious approach was used the second time . First , a medium coarse sandpaper was used to put some scratches on the needle , then these were polished out using chrome polish .
The result seems ok , but have not tested it on a RR , so no real data .

[MarekH]

If you look in the Knowledgebase, you'll probably find David has already posted all the needle data for you. You can then see which needles are richer/leaner and whether this is at high/low load and compare.

If you look at the lower table I posted, then the carburettor equivalent would be one which has the numbers the same value going from left to right all along. This means you'd be running the same fuel setting at every rpm, whereas the fuel injected car has clearly been set up to run richer or leaner than that at different revs. (It runs richest mostly at about 4500rpm according to the table - I assume it is pulsewidth/10 in mSec, as the top table is ignition advance in degrees/10, i.e. 396 = 39.6' advance at 3250rpm and low load .)

kind regards
Marek

[Woolfi]

At most of the time, my 6,0L HE motor at small part throttle and medium part throttel is running with a lambda of roundabout 1,05 to 1.10. When crusing with this mixture, an injectet car can't take much less gas. 5% les would be a great number. My car is driving when crusing with roundabout 18 - 20 mpg.
In the city these numvers ar much higher.
The difference in gas consumption between an injecteed car and the same car with carbs would be biggest, when driving in the city. If the injection is stopping gas supply at overrun, this can make a bigger difference in consumption.
Barry told us, that his car is runnung very strong and better than a carbed EV12 with 6,0L. Has he TESTED on a road ? No, shure not. I have done this test two times in my life on a free Autobahn. Both times - for my BIG SURPRISE- my carbed car accelerated MUCH better than the car with injection, when accelerating from 2000 rpm up to 4000 rpm in 4th gear. Both cars driving with roundabout 50 mp/h in 4th gear and the drivers pressed the pedal to the metall and waited what happened. My car has a axle of 2,88, the other car had a 3,07. Therefore the difference in torque was bigger, than the difference in accelaration.
A test with two other cars ha a small scientific reliability. Therefore I would like to make this test again. Shure I know, that the cars must have the same displacement and also the same axle ratio.
As long as nobody shows me on a REAL road, that his EV12 with an injection is accelerating better betwwen 2000 and 4000 rpm, I don't believe him. Maybe yes. Maybe the two cars had a bad programming.
I know, that this story sounds like a fairy tail of a fool, who loves his own car. But it is not. I am interessted in the truth, that I will be able to find better technical solutions.
Upon 4000 rpm the injected motor is stronger, has more power and the car is leaving the carbed car slowly.
Also I know very well, why modern cars have an injection. Better starting, better iddle, lower gas consumption and higher power. I am not a fool. But in these two tests I realised, that the torque curve of the carbed EV12 seems (!) to be higher than the torque curve of the injected car between 2000 and 4000 rpm.
Regards Wolfgang Gatza