| Author | Message | ||
     bob uk Unregistered guest Posted From: 92.40.249.159 |
Vlad said wizz bang injection that can take hours to fault find whereas carbs 15 mins max. I agree. Further to that. It is assumed that injection is more efficient than carbs. The difference is however not as large as some think. Probably 2% only. The dizzy and the carb are a mechanical engine management system. Injection is more about emissions than efficiency. Turbo charging is easier with injection. The hot rod guys still favour carbs. One sticking point for hot rodders is the mess of pipe work and bits which is hard to tidy up. Here's an example of injection versus carbs. Jeep multi point injection car weight 1700kg. mpg 16. Shadow carbs car weight 2400kgs. Mpg 12. The difference in weight accounts for the difference in mpg. I would suggest that if I put the 180bhp jeep engine in the shadow it will do about 12 mpg. and the 200bhp shadow engine in the jeep 16 mpg. I do like the instant starting of the jeep. 2 to 3 seconds. The idle is very reliable 700 rpm regardless. What does let the side down is the excessive amount of vacuum pipes. I keep gaffer tape in the car. (Message approved by david_gore) | ||
| Vladimir Ivanovich Kirillov Prolific User Username: soviet Post Number: 207 Registered: 2-2013 |
An interesting point I have really never got to the bottom of is LPG. The media and the car manufactures had much squark about computerized fuel injection being necessary to cut down on emissions but when I did the LPG installers and repairers course decades ago the lecturers stated that LPG puts out hardly any damaging pollutants so the question I have always asked is why then did not western governments force the car manufactures to make only LPG cars. The answer I got was basically the oil companies vetoed it time and again. I am not big on conspiracy theories at all but Mr and Mrs Joe Blow are never happy with the repair costs of a malfunctioning efi vehicle. They never understood carburation so efi was always going to be far out of their league. Then also you have CNG which as I understand it became popular in New Zealand. Admittedly, one used more LPG and CNG to get to along per litre, but if emissions drove the insane drive to efi with all it complications then why was this path taken instead of LPG? Also, you have the event of common rail diesels. As some of you will know if you open an injector line on one of these wonderful engines while its running you can have upwards of 30,000 psi coming in contact with your arm which will produce a bigger mess than a shotgun blast of buckshot and amputation is a certainty. I predicted long ago that there will be intense litigation over this caper as many farmers will one day be in possession of engines where the warning sticker about the danger of common rail injection systems have faded, fallen off and or generally disappeared. It surprises me how many farmers don't know about these dangers and as we all know farmers love to tinker if they can save a buck. Definitely common rail diesel systems are more efficient and put out less pollutants but they are also deadly for the novice. Admittedly I put large oil companies into the same trust basket as the KGB and the CIA along with bankers and insurance companies in that I would trust a stranger before believing any of the profession public relations propaganda coming from the aforesaid biggys. Does anybody have the answer? | ||
| bob uk Unregistered guest Posted From: 92.40.249.159 |
Correction 2% should be 5% (Message approved by david_gore) | ||
| Jan Forrest Grand Master Username: got_one Post Number: 789 Registered: 1-2008 |
Part of the problem with LPG is the vastly greater storage costs. Petrol is normally a liquid at any temperature you're likely to experience on Planet Earth. Propane and butane need to be pressurised to become liquid above -30 Celsius or so. Due to health & safety concerns bulk LPG tanks have to be sited above ground with a significant 'clear area' around them. Bulk petrol and diesel tanks can be safely hidden below ground - and usually are. You can carry some spare petrol or diesel in a small plastic container, while LPG needs a more robust, properly designed and tested pressure vessel. It's the same for compressed natural gas, albeit at lower pressures as it can be 'dissolved' in a solid matrix for superior stability at high temperatures. However CNG is shipped around the world in special tankers and then stored in vast facilities for distribution. Due to the greater use of CNG it's economically viable to invest in such facilities, while it's more 'efficient' to simply burn off any excess LPG produced as a by-product of the oil cracking process. (In the late 19th and early 20th centuries both petrol and diesel were embarrassing waste products in the manufacture of paraffin/kerosene/lamp oil!) Just to make things awakward, petrol can be easily atomised to make it burn efficiently in an infernal combustion engine while LPG requires some heat to turn it into gas in sufficient quantities to run a car. Although mixing it with the correct quantity of air is theoretically simpler, in practice it's the opposite. Due to 'laminar flow' properties in the air/fuel intake paths correct mixing may not occur and the engine will run poorly - if at all. If you watch enough clips on YouTube you will see the occasional LPG equipped car suddenly explode in flames from the less than competent conversions available where safety compliance is just a matter of opinion. More than a few 'convertors' are happy to use a simple dip tube equipped consumer gas bottle in favour of the much more expensive properly designed and tested tank. | ||
| Lluís Gimeno-Fabra Grand Master Username: lluís Post Number: 351 Registered: 8-2007 |
Hi, Carbs can be as efficient as injection, yes. But the question is in how many circumstances. I have never had the slightest problem spotting problems in EFI systems at least until 2005 -did not need to any later-. The fact that there are dedicated sensors for air temperature, water temperature, CPS and AFR simply makes things much simpler. Whilst it is hard to disagree that CAN-BUS systems need dedicated tools, the fact that they communicate with ISO protocols makes troubleshooting relatively simple. Then comes driving: post 1980's mutipoint systems working on CPS instead of vacuum (a la early Lucas) work always and in all conditions unless a component is at fault... Of course one can be nostalgic about carbs, but when one of those orifices got dirty in a Webber 44... go and seek. And boy, when you had two of these in parallel, did they need trimming. And yes, SU needles got eroded, floating chambers got stuck and at the end we all know you needed a guru to get anything more complex than a two barrel carb working properly. When I moved from my beloved SU's to ITB's working on a CAN-BUS high-tech ECU that can take different mappings for different gears in my racing Cooper I was amazed at the improvement in virtually every single aspect of driving and tuning... Of course a lean carb would be more efficient -and dig a whole in a piston- but now I can be as lean as I want and measuring TPS angular acceleration just multiply fuelling in a nanosecond. I did not include a lambda, which I now regret, just to keep AFR where I wanted it, above stoeichiometric. Not because I am an environmentalist, but because that's where engines are efficient. Issue is also: what are we calling carbs and what are we calling injection, yes the rodder boys have shiny carbs making nice intake noises. But so do my four ITB's punching 160+bhp from 1380cc in my Cooper. So what is next: there is no substitute for cubic inches other than cubic inches...? Best regards, Lluís | ||
| bob uk Unregistered guest Posted From: 92.40.249.229 |
Modern ignition systems that listen for pinking are more responsible for efficient combustion. Engine designers take advantage of such system in the combustion chamber design. Early electronic ignition allowed the fireball chamber to work. Using points wouldnt have worked. Jag V12 HE. Its not so much how the fuel is put in the engine but how its burnt. Older engines were designed to work with the ignition technology of the time. Which is why when points are converted to electronic the engine runs about the same. My favourite carb is the SU because its simple and robust. sticky floats is due to lack of use. The su carb was fitted to many small vans which were used by fleet operators and they never had lots sticky float problems I had a Austin 1100 and did 12k miles and the floats never jammed. Because the main jet (the only jet) hole is quite large blockages are rare and easy to clean if it does get blocked. There's no replacement for cubic inches. However nitrous oxide sorts out that problem. Nitrous will easily double the bhp. But I recommend fit a system capable of double but set it up for 10% and see how it goes. Users often find that the cars chassis is at the limit long before double bhp. Also full power use is limited by road conditions and speed limits. So once the car has accelarated to what ever speed the nitrous turns off. To accelarate say 0 to 60 mph in 5 seconds means 5 seconds of nitrous use. Modern systems use bigger petrol injectors. The air mass meter detects the nitrous and signals the ecu to open injectors longer. These systems are very smooth. Older systems were brutal and scary. I drove a 1500 cc mk1 cortina fitted with nitrous and on damp roads the back end was all over the place. It was difficult to use because one instant its 70bhp then suddenly its got 50 more no warning. A Dutch guy at santa pod drag strip ran an 1900cc opel with nitrous and 500bhp. I dont think it ever actually got to 500bhp because the car was spinning rear wheels for the whole quarter. Oh those crazy Dutch guys. He wreaked quite a few engines. He said that he buys the engines from scrap yards. He doesn't bother rebuilding the engine he bolts on the nitrous bit (a frog plate between the carb and inlet manifold) and the car is ready to race. (Message approved by david_gore) | ||
| bob uk Unregistered guest Posted From: 92.40.249.229 |
Fortunately most who fit or use lpg aren't stupid and fit and use lpg in a safe manor. Every single regulation regarding auto gas use in car has an obvious reason. Just follow the regs and it will be safe. Laminar flow is a problem with intakes but by the time the lpg has gone past the carb piston, past the butterfly, through a hot inlet manifold, past the inlet valve and then squeezed the lpg will be well mixed. (Message approved by david_gore) |
