Discussion
Can you tell me why I would chose a bike engine over a car engine for a kit?
I guess the following but would love to hear what you all know from experience :-
1) Light and compact for the power produced
2) No reverse gear?
3) How do they cope with relatively low torque outputs - do you just have to rev them to death
4) Presumably no more economical to run (MPG/servicing) than a car engine?
5) About the same price to buy (or are they more expensive)?
6) Do bike engines have catalytic converters these days?
7) Do you have to go for water cooler bike engines?
8) Do you need to swop in a larger altenator to power more kit? (I might like a radio and an alarm)?
9) Assuming sensible use, would a bike engine last as well as a modern car engine (say 80k miles)?
10) Do they only work in really light kits (would they handle 900 kg?)
What did I fail to ask?
Much appreciated?
If you have any questions on accountancy issues let me know....happy to return the favour.
LAW
I guess the following but would love to hear what you all know from experience :-
1) Light and compact for the power produced
2) No reverse gear?
3) How do they cope with relatively low torque outputs - do you just have to rev them to death
4) Presumably no more economical to run (MPG/servicing) than a car engine?
5) About the same price to buy (or are they more expensive)?
6) Do bike engines have catalytic converters these days?
7) Do you have to go for water cooler bike engines?
8) Do you need to swop in a larger altenator to power more kit? (I might like a radio and an alarm)?
9) Assuming sensible use, would a bike engine last as well as a modern car engine (say 80k miles)?
10) Do they only work in really light kits (would they handle 900 kg?)
What did I fail to ask?
Much appreciated?
If you have any questions on accountancy issues let me know....happy to return the favour.
LAW
1) Correct
2) Correct, but there are plenty of seperate reverse gearbox/transaxle units available these days. Check out Quaiffe's website, for a start.
3) Yes - you gear them stupidly low and live life at a 9,000rpm scream.
4) Correct
5) More expensive than a low specification (ie. near standard tune) car engine; cheaper than a car engine that has been tuned to give similar specific power output (ie. bhp/litre)
6) Yes
7) Effectively, yes. There are no modern bike engines with air cooling that are big enough and powerful enough to haul a car and if there were, they would tend to overheat in the enclosed engine bays. Some 'Morgan' type 3 wheelers have used Moto Guzzi or similar air cooled V-twins, though, and something like the old BMW flat twin could probably be made to work in a light enough car.
8) Depends on the car and your usage. Most people put them in very minimalist cars and use them mainly in daylight and good weather, so the electrical loads are light. Radio would only be a problem if you actually expect to be able to hear it. Alarm will depend more on the size of battery and whether you use the car often enough to keep it charged. Use a trickle charger, if you keep it garaged.
9) No, not a cat in hell's chance. People will tell you tales of big bikes having covered this sort of mileage, but (a) they are exceptional cases and, (b) bikes are much lighter and higher geared, so won't experience the sustained high revs that a bike engined car needs. Depends on engine type and usage, but I wouldn't put money on getting more than 30K miles out of one before it is utterly shagged.
10) Yes, they only work well in really light kits; no they wouldn't handle 900kg.
2) Correct, but there are plenty of seperate reverse gearbox/transaxle units available these days. Check out Quaiffe's website, for a start.
3) Yes - you gear them stupidly low and live life at a 9,000rpm scream.
4) Correct
5) More expensive than a low specification (ie. near standard tune) car engine; cheaper than a car engine that has been tuned to give similar specific power output (ie. bhp/litre)
6) Yes
7) Effectively, yes. There are no modern bike engines with air cooling that are big enough and powerful enough to haul a car and if there were, they would tend to overheat in the enclosed engine bays. Some 'Morgan' type 3 wheelers have used Moto Guzzi or similar air cooled V-twins, though, and something like the old BMW flat twin could probably be made to work in a light enough car.
8) Depends on the car and your usage. Most people put them in very minimalist cars and use them mainly in daylight and good weather, so the electrical loads are light. Radio would only be a problem if you actually expect to be able to hear it. Alarm will depend more on the size of battery and whether you use the car often enough to keep it charged. Use a trickle charger, if you keep it garaged.
9) No, not a cat in hell's chance. People will tell you tales of big bikes having covered this sort of mileage, but (a) they are exceptional cases and, (b) bikes are much lighter and higher geared, so won't experience the sustained high revs that a bike engined car needs. Depends on engine type and usage, but I wouldn't put money on getting more than 30K miles out of one before it is utterly shagged.
10) Yes, they only work well in really light kits; no they wouldn't handle 900kg.
From the perspective of someone who runs a bike as daily transport (blade), who is building a bec based on one passenger ride and runs a v8 westfield while the bec is being built...
1)Yes
2)Quaife mech reverse or cobbled together electric reverse
3)Not to death but you keep them above 5k and they're fine
4)More economical than a car engine to a point from what I understand
5)More expensive. From 500 for someting older to 1k for an R1 (injected) to lots more for a busa
6)Yes but insufficiently large to get a car wth a bike engine through sva
7)Yes, I'd say so. There's the odd exception but nothing relatively modern
8)It can be marginal but you can get by
9)Easily. I've just had the head off my 27k blade to fix a spark plug thread and there's no wear. One blade made it to 250k with no major work. The reason it's exceptional is more to do with riders habits than any engine issues. Gearboxes can be a weak point when in a car though
10)The lighter the better but they put them in minis but you'd be pushing it at 900Kg imo.
The main thing is that they keep the car weight down and the replacement cost is reasonable if you blow one compared with a tuned car engine (busa excepted) and the sheer speed of the gear change.
Mark
1)Yes
2)Quaife mech reverse or cobbled together electric reverse
3)Not to death but you keep them above 5k and they're fine
4)More economical than a car engine to a point from what I understand
5)More expensive. From 500 for someting older to 1k for an R1 (injected) to lots more for a busa
6)Yes but insufficiently large to get a car wth a bike engine through sva
7)Yes, I'd say so. There's the odd exception but nothing relatively modern
8)It can be marginal but you can get by
9)Easily. I've just had the head off my 27k blade to fix a spark plug thread and there's no wear. One blade made it to 250k with no major work. The reason it's exceptional is more to do with riders habits than any engine issues. Gearboxes can be a weak point when in a car though
10)The lighter the better but they put them in minis but you'd be pushing it at 900Kg imo.
The main thing is that they keep the car weight down and the replacement cost is reasonable if you blow one compared with a tuned car engine (busa excepted) and the sheer speed of the gear change.
Mark
Edited by dern on Saturday 1st July 00:41
To expand on a couple of points:
2) I was being a little tongue-in-cheek with the 9,000rpm bit, but you do need to recognise what 5,000rpm+ means in practice. Most modern car engines are similarly happy at 2,000prm (ie. half the revs), and BECS often have very short gearing. To put some numbers to it (since you're an Accountant!), gearing varies but a typical modern road car will have a top gear that pulls around 27mph/1000rpm engine speed, so at a motorway cruise of 85mph the engine would be spinning at 3,150rpm or thereabouts. Gearing of BECs similarly varies, but a typical figure would be 14mph/1000rpm, so at 85mph the engine would be spinning at approx. 6,000 rpm. Draw your own conclusions.
4) In terms of economy, I'd say that there probably wouldn't be enough in it to worry either way, but for comparison I did a long trip in my Elise S160 last weekend and actually bothered to work out the fuel consumption for the first time: 1800cc car engine in a relatively high state of tune, in a car which would be considered heavy by BEC standards, over 300 miles of mixed driving - some of it hard, some of it stuck in queues - averaged 33mpg. You might get a little more than that from a BEC (any offers from the BEC owners? 36mpg perhaps?), but not a huge difference. With modern engines with fully mapped fuel injection, to be honest fuel economy is more down to driving conditions and how heavy a right foot you have, though the lighter weight of a BEC has some benefit (often offset by the fact that it is fitted to a Seven type car with lousy aerodynamics!).
Beyond fuel costs, of course, you have to take into account servicing. Bike engines really need more frequent oil changes with the best synthetic oils, and cost of parts like filters and plugs is higher than for something out of a Ford or Rover. Overall, my guess is that BECs are probably a little more expensive to run, but not by enough to worry about.
9) Mark: Were those 27,000 miles done in a car though?
Engine wear is related mainly to the loads placed upon the engine (crank wear) and the revs it has had to work at (top end wear). In their original bike installation, these engines are relatively lightly stressed on both accounts. My friends with big bikes tell me that it is very rare to take them above 7000 rpm because (a) you don't need to and, (b) you never get the chance on public roads. Apart from an occaisonal caning on clear mountain roads, they live their life at very moderate revs (mostly below 6K rpm) and crank loadings. With the much shorter gearing and higher vehicle weights they have to cope with in a car, wear is dramatically (read exponentially, in mathematical terms) increased.
As Mark says, quite apart from engine wear, you usually have much bigger issues with gearboxes and clutches, which are similarly overloaded compared to their original application. One of the reasons for the sheer speed of the gearchange (apart from the obvious one - that it is sequential) is that bike gearboxes have dog engagement rather than the synchromesh engagement of a road car gearbox. Sequential dog boxes are readily available for car applications if you want them (again, see Quaiffe's website, for a start). They are usually only fitted to competition cars, though, because it was realised a long time ago that they aren't really suitable to meet most people's expectations on a road car: you will knock the dogs off and need regular rebuilds and you will find them pretty clunky if you get stuck crawling in traffic. Dog boxes (whether fitted to a bike or a car engine) give superb fast gearchanges for track/competition use, but few people would want to live with them on a car used for commuting. For a roadgoing car which is a weekend toy, you pays your money and you takes your choice...
2) I was being a little tongue-in-cheek with the 9,000rpm bit, but you do need to recognise what 5,000rpm+ means in practice. Most modern car engines are similarly happy at 2,000prm (ie. half the revs), and BECS often have very short gearing. To put some numbers to it (since you're an Accountant!), gearing varies but a typical modern road car will have a top gear that pulls around 27mph/1000rpm engine speed, so at a motorway cruise of 85mph the engine would be spinning at 3,150rpm or thereabouts. Gearing of BECs similarly varies, but a typical figure would be 14mph/1000rpm, so at 85mph the engine would be spinning at approx. 6,000 rpm. Draw your own conclusions.
4) In terms of economy, I'd say that there probably wouldn't be enough in it to worry either way, but for comparison I did a long trip in my Elise S160 last weekend and actually bothered to work out the fuel consumption for the first time: 1800cc car engine in a relatively high state of tune, in a car which would be considered heavy by BEC standards, over 300 miles of mixed driving - some of it hard, some of it stuck in queues - averaged 33mpg. You might get a little more than that from a BEC (any offers from the BEC owners? 36mpg perhaps?), but not a huge difference. With modern engines with fully mapped fuel injection, to be honest fuel economy is more down to driving conditions and how heavy a right foot you have, though the lighter weight of a BEC has some benefit (often offset by the fact that it is fitted to a Seven type car with lousy aerodynamics!).
Beyond fuel costs, of course, you have to take into account servicing. Bike engines really need more frequent oil changes with the best synthetic oils, and cost of parts like filters and plugs is higher than for something out of a Ford or Rover. Overall, my guess is that BECs are probably a little more expensive to run, but not by enough to worry about.
9) Mark: Were those 27,000 miles done in a car though?
Engine wear is related mainly to the loads placed upon the engine (crank wear) and the revs it has had to work at (top end wear). In their original bike installation, these engines are relatively lightly stressed on both accounts. My friends with big bikes tell me that it is very rare to take them above 7000 rpm because (a) you don't need to and, (b) you never get the chance on public roads. Apart from an occaisonal caning on clear mountain roads, they live their life at very moderate revs (mostly below 6K rpm) and crank loadings. With the much shorter gearing and higher vehicle weights they have to cope with in a car, wear is dramatically (read exponentially, in mathematical terms) increased.
As Mark says, quite apart from engine wear, you usually have much bigger issues with gearboxes and clutches, which are similarly overloaded compared to their original application. One of the reasons for the sheer speed of the gearchange (apart from the obvious one - that it is sequential) is that bike gearboxes have dog engagement rather than the synchromesh engagement of a road car gearbox. Sequential dog boxes are readily available for car applications if you want them (again, see Quaiffe's website, for a start). They are usually only fitted to competition cars, though, because it was realised a long time ago that they aren't really suitable to meet most people's expectations on a road car: you will knock the dogs off and need regular rebuilds and you will find them pretty clunky if you get stuck crawling in traffic. Dog boxes (whether fitted to a bike or a car engine) give superb fast gearchanges for track/competition use, but few people would want to live with them on a car used for commuting. For a roadgoing car which is a weekend toy, you pays your money and you takes your choice...
Sam_68 said:
To expand on a couple of points:
2) I was being a little tongue-in-cheek with the 9,000rpm bit, but you do need to recognise what 5,000rpm+ means in practice. Most modern car engines are similarly happy at 2,000prm (ie. half the revs), and BECS often have very short gearing. To put some numbers to it (since you're an Accountant!), gearing varies but a typical modern road car will have a top gear that pulls around 27mph/1000rpm engine speed, so at a motorway cruise of 85mph the engine would be spinning at 3,150rpm or thereabouts. Gearing of BECs similarly varies, but a typical figure would be 14mph/1000rpm, so at 85mph the engine would be spinning at approx. 6,000 rpm. Draw your own conclusions.
I'm not sure I understand this. If you want to put the bec in a car which will be used on a daily basis and you don't want it sitting at high revs on the motorway you'd gear it accordingly by changing the final diff ratio. Similarly, with a car engine, if you want acceleration rather than relaxed cruising you'd also gear it accordingly. I grant you than the lack of torque in a bike engine and the light weight lends itself to a lower geared, acceleration oriented car but if you were putting a zetec or a v8 in something like a westfield then you wouldn't necessarily gear it for 150mph anyway. 2) I was being a little tongue-in-cheek with the 9,000rpm bit, but you do need to recognise what 5,000rpm+ means in practice. Most modern car engines are similarly happy at 2,000prm (ie. half the revs), and BECS often have very short gearing. To put some numbers to it (since you're an Accountant!), gearing varies but a typical modern road car will have a top gear that pulls around 27mph/1000rpm engine speed, so at a motorway cruise of 85mph the engine would be spinning at 3,150rpm or thereabouts. Gearing of BECs similarly varies, but a typical figure would be 14mph/1000rpm, so at 85mph the engine would be spinning at approx. 6,000 rpm. Draw your own conclusions.
Sam_68 said:
Beyond fuel costs, of course, you have to take into account servicing. Bike engines really need more frequent oil changes with the best synthetic oils, and cost of parts like filters and plugs is higher than for something out of a Ford or Rover. Overall, my guess is that BECs are probably a little more expensive to run, but not by enough to worry about.
In the application a bike engine would normally be placed the car would tend to do less miles a year and possibly more track days so you'd probably end up changing the oil with the same regularity for both. The statement that bike service items are more expensive than car parts are just not true unless the car you're comparing it with it your mums 1.1 escort. Sure you can throw cheap service items at your car and more cheap versions of service items are available and indeed cheaper oil is available but you aren't comparing like with like by suggesting that you car engined performance car can and should be fitted with them.Sam_68 said:
My friends with big bikes tell me that it is very rare to take them above 7000 rpm because (a) you don't need to and, (b) you never get the chance on public roads. Apart from an occaisonal caning on clear mountain roads, they live their life at very moderate revs (mostly below 6K rpm) and crank loadings. With the much shorter gearing and higher vehicle weights they have to cope with in a car, wear is dramatically (read exponentially, in mathematical terms) increased.
I don't know what bikes your friends ride but with a sports bike such as the blade or r1 whose engines are normally used for a bec you rarely ride in below 5k... I certainly don't anyway and mine is my daily commute. I generally change up at 9k if I'm pootling along and 11-12k if I'm wanting to go a bit quicker and as soon as I get down to 5k I change down. I suspect your mates may ride more touring oriented bikes or possibly triples or twins because if they ride blades and r1s around below 7k they wasting their money on maintaining those bikes imo and would be better off with 600s. This isn't meant to be in any way judgemental but your claim that a sports bike engine spends most of its time below 7k is wrong.dern said:
I'm not sure I understand this. If you want to put the bec in a car which will be used on a daily basis and you don't want it sitting at high revs on the motorway you'd gear it accordingly by changing the final diff ratio.
1) If you geared a BEC to do 27mph/1000rpm in top, it wouldn't have enough torque at the back wheels to pull the skin off a rice pudding.
2) You simply can't get diff ratios tall enough to acheive that sort of gearing, anyway - you would need to use a step-down gearing, but even this didn't give such tall gearing, even in high ratio top, because Murray knew that the engine lacked the torque to pull it.
The effective maximum for a BEC with readily available gearing components is about 17mph/1000rpm in top. My Elise has a close ratio gearbox with a short top gear, yet is still geared for 20mph/1000 in top and even then is, frankly, tiresome at a motorway cruise because of the sustained (relatively) high revs.
I don't especially want to reopen the whole 'lack of torque/gearing' debate again, but if you do a seach on this forum you'll come across a previous thread where it has been discussed in great detail.
dern said:
The statement that bike service items are more expensive than car parts are just not true unless the car you're comparing it with it your mums 1.1 escort.
I'm comparing it with my Elise Sport 160, which uses standard Rover/MG service items. My mum, for the record, doesn't drive.
I agree that for track use, it won't make any difference, but I made the rash assumption that we were talking about road use?
Dern said:
I don't know what bikes your friends ride but with a sports bike such as the blade or r1 whose engines are normally used for a bec you rarely ride in below 5k... I certainly don't anyway and mine is my daily commute. I generally change up at 9k if I'm pootling along and 11-12k if I'm wanting to go a bit quicker and as soon as I get down to 5k I change down. I suspect your mates may ride more touring oriented bikes or possibly triples or twins because if they ride blades and r1s around below 7k they wasting their money on maintaining those bikes imo and would be better off with 600s. This isn't meant to be in any way judgemental but your claim that a sports bike engine spends most of its time below 7k is wrong.
Blackbird, Hyabusa, Ducati (so yes, I acknowledge that V-twins are much lower revving) and Honda Fireblade (but ridden by an old fart who thinks I drive my diesel Toyota Avensis company car recklessly, so should probably be riding a Honda C90, never mind a 600!). The comment came from the guy who rides the Blackbird, though, and the guy with the Hyabusa was in agreement at the time, so we are talking about bikes with rather more power and capacity than the Blade; I accept that a Blade will use more revs, but again it won't spend its whole life in a bike running at 9,000rpm plus.
I didn't mean to imply that the bikes were never taken above 7,000 rpm, just that the percentage of time they spent at higher revs was relatively limited. Are you suggesting that your 250,000 mile Fireblade spent its whole life being bounced off the rev limiter? If so, where did it come from...if there is anywhere left on the planet with roads that allow that sort of behaviour, I want to live there!
I honestly think it's fair to say that any bike engine will be running at much higher average revs when fitted to a low geared car than in its original bike application. Would you dispute this?
Sam_68 said:
1) If you geared a BEC to do 27mph/1000rpm in top, it wouldn't have enough torque at the back wheels to pull the skin off a rice pudding.
Why would you do that though given that you'd be gearing for a top speed of 324mph? Sam_68 said:
2) You simply can't get diff ratios tall enough to acheive that sort of gearing, anyway - you would need to use a step-down gearing, but even this didn't give such tall gearing, even in high ratio top, because Murray knew that the engine lacked the torque to pull it.
Ignoring your target figure of 300+mph and aim for something like 130 which is more sensible then you can easily get diffs to get your car to these sort of speed and higher if you want to spend more money. Sam_68 said:
The effective maximum for a BEC with readily available gearing components is about 17mph/1000rpm in top.
No offence Sam but what are you talking about mate? A blade has a relatively low redline at 12000rpm and with your figures this gives 204mph... no one is going to gear a bec for that kind of speeds unless they turbo'd it and frankly if they did and had the power to get their then I would suggest that this is probably sufficient and if you have the choice of a max speed up to 200mph you'd be more than happy. Sam_68 said:
I'm comparing it with my Elise Sport 160, which uses standard Rover/MG service items. My mum, for the record, doesn't drive.
What are you comparing with your rover items? Do you know how much a fireblade oil filter costs for example? Do you really run mineral or semi in your elise? Sam_68 said:
I honestly think it's fair to say that any bike engine will be running at much higher average revs when fitted to a low geared car than in its original bike application. Would you dispute this?
Yes, I think you're wrong as I've already said. I use the full rev range is whatever car/bike I own... in my honest opinion the numbers are just numbers and all I care about is that I get enough power/torque to propel me at the rate I want. I rev my golf to 6500rpm, my v8 to 6000rpm and my blade to 12000rpm simply because that's the rev range when the power is (more or less). If my golf rev'd to 12000rpm instead of 6500rpm and it accelerated in the same fashion and was no noisier or peakier then the numbers on the tacho would, imo, be irrelevent. Regards,
Mark
Edited by dern on Saturday 1st July 13:20
Edited by dern on Saturday 1st July 13:20
dern said:
Why would you do that though given that you'd be gearing for a top speed of 324mph?
1) To get piston and crankshaft speeds down to reasonable levels, thereby extending engine life to your entirely theoretical 250,000 miles. Piston speed (in feet per second) is one of the major factors in engine life. In the old days, magazines like Autocar used to quote figures for piston speeds...these days, the level of technical 'dumbing down' is such that most people haven't even heard of the concept. The best that you will get from the majority of BEC enthusiasts is the peal of wisdom that 'they are built to take the revs', without any real understanding of the design constraints involved. They are built to take the revs, but not at such high averagerevs as are imposed by the low gearing of a BECs, not with the expectation of doing 100K miles(let alone the 200K mileage between rebuilds that is the current benchmark for car engines) and not dragging around 500+ kilos of car and driver.
2) To give relaxed cruising at the sort of revs and noise levels that people have come to expect in modern cars. If you are willing to live with the high revs, fine, but you cannot ignore the fact that it is an issue which militates against the use of bike-type engines in cars for most people. You might be a sufficiently rabid enthusiast to live with the shortcomings because you feel that they are outweighed by the performance benefits, but to deny that there is any compromise involved is absurd.
Plenty of cars have dramatically over-driven gearing in top, these days; the standard Elise is geared for a theoretcial 175mph in top (actual top speed about 126mph) and things like Corvettes are geared for theoretical top speeds of 250mph plus.
dern said:
...aim for something like 130 which is more sensible then you can easily get diffs to get your car to these sort of speed and higher if you want to spend more money.
You can, but your engine will still be spinning at much higher revs than a normal road car and, on average, much higher revs than it would be likely to experience in the application for which it was originally designed.
dern said:
No offence Sam but what are you talking about mate? A blade has a relatively low redline at 12000rpm and with your figures this gives 204mph... no one is going to gear a bec for that kind of speeds unless they turbo'd it and frankly if they did and had the power to get their then I would suggest that this is probably sufficient and if you have the choice of a max speed up to 200mph you'd be more than happy.
See above...gearing choice is a little more complex than just working out a theoretical top speed. I agree that no-one would gear a BEC that tall, but you have to accept that the fact that BECs only work well with ultra-short gearing means that they suffer compromises in terms of noise, cruising revs, engine/gearbox life etc. that aren't present in a car engined car.
dern said:
Do you really run mineral or semi in your elise?
I run Mobil 1 synthetic and the Elise 160 is a bit of a special case in that it has 6000 mile service intervals. If I were driving a car with a 'normal' K-series, or Duratec, or whatever, I would be quite happy with lower cost full synthetic or a good semi-synthetic; there is an awful lot of bullshit talked about oils, and most modern oils of the correct viscosity are perfectly adequate for road use.
More importantly, I would be changing that oil (and other service components like filters and spark plus) two or three times less frequently on a 'normal' car compared to a modern sportsbike engine. On a BEC, due to the higher loadings and higher average engine speeds imposed by the car application compared to the bike application, I'd also be looking at changing the oil more frequently than the normal service schedule for the bike.
Correct me if I'm wrong, but the Fireblade bike has 4,000 mile service intervals? The oil filters cost about a tenner, from what I'm told, so only a couple of quid more than a car filter, but you'd need 3 of them (and 3 lots of expensive synthetic oil...the Fireblade's sump capacity is, surprisingly, not significantly smaller than most cars) for every one you'd need on a car, even if you don't increase the servicing frequency to compensate for the extra strain you are putting on the engine?
dern said:
I use the full rev range is whatever car/bike I own... in my honest opinion the numbers are just numbers...
So do I, but I think you misunderstand the concept I am trying to get across.
I will usually hit the redline in any vehicle I drive every time I use it, but not for extended periods. What I am trying to get across is that average revs, over the whole of a journey are not that high. If you take into account all the time you spend cruising at normal traffic speeds, sitting at junctions and slowing down for corners, the amount of time in any given journey that a big bike spends above 7K rpm is not that big, in percentage terms. With a BEC which, as you say, really needs to be kept at moderately high revs all the time to compensate for the lack of torque when pulling such a large weight, the average revs that the engine has to work at will be much higher and it will also spend proportionately more time right at the upper end of the rev range than it would in a bike, if you are driving quickly. See earlier comments about piston speed and engine wear.
Numbers are what engineers use to design things. If you make an engine use different numbers to those the engineers envisaged for it, expect reduced lifespan and occasional catastrophic failures.
Edited by Sam_68 on Saturday 1st July 14:38
Sam, before carrying on (which is interesting, don't get me wrong, but the football is on in a minute) do you have any experience of running a bike engine either in a bike or in a car? Have you been out in a bec or ridden a superbike?
Regards,
Mark
Regards,
Mark
Edited by dern on Saturday 1st July 15:44
Yes, I've got many years experience of BEC's, from early days working on (I used to set up suspension as part of my living) and driving single seat hillclimb cars like Jedi's and Megapins (which, it might surprise many current BEC enthusiasts, have been around for a long time - I first drove one in the late '80's, but they predate that), through to having driven several current generation 'Seven' type BECs on both road and track.
edited to add...used to make a bit of money out of freelance motoring journalism, too, and I've encountered several in that line of work, but no, I've never owned one - you'll have gathered that they are not especially my cup of tea for road use, though I'd happily buy one for pure track use. Experience of bikes is limited to pillion passenger...again, never really appealed to me, and I don't have a bike licence.
Apart from the one, brief passenger ride that you mentioned earlier, what is your experience of driving them?
edited to add...used to make a bit of money out of freelance motoring journalism, too, and I've encountered several in that line of work, but no, I've never owned one - you'll have gathered that they are not especially my cup of tea for road use, though I'd happily buy one for pure track use. Experience of bikes is limited to pillion passenger...again, never really appealed to me, and I don't have a bike licence.
Apart from the one, brief passenger ride that you mentioned earlier, what is your experience of driving them?
Edited by Sam_68 on Saturday 1st July 15:56
1) Light and compact for the power produced - YES
2) No reverse gear? - YES but not usually a problem.
3) How do they cope with relatively low torque outputs - do you just have to rev them to death - YES, they are not low torque, they just operate over a wider rev range just like a performance car engine does, just choose your revs according to the state of tune and rev range of the engine.
4) Presumably no more economical to run (MPG/servicing) than a car engine? NO
5) About the same price to buy (or are they more expensive)? SOME are more to buy but when you look at it from a pounds/bhp they vare very cheap compared to tuning say a Vx or Duratec engine to make a car perform the same. Don't forget they come with 6 speed seq gearboxes as standard ! (A standard Westfield/Dax Hayabusa with 175ish bhp will perform on track similar to a 215-220bhp Vx/Duratec car)
6) Do bike engines have catalytic converters these days? SOME do but you can add one if you need it for SVA
7) Do you have to go for water cooler bike engines? NO but how much work do you want to invent for yourself ? Using an air cooled engine will make less power and need additional cooling . . . not a great idea unless you already happen to have an air cooled 200bhp engine looking for a home ?
8) Do you need to swop in a larger altenator to power more kit? (I might like a radio and an alarm)? Get a good battery but if you want a radio in the car maybe a BEC isn't right for you ?
9) Assuming sensible use, would a bike engine last as well as a modern car engine (say 80k miles)? 40k miles yes, at 80k I suspect it might be in need of a refresh - about £1200 depending what needs to be done.
10) Do they only work in really light kits (would they handle 900 kg?) YES, would be a mistake to use a standard bike engine in a car weighing over 750Kg unless you want to spend your whole life at max revs/throttle.
2) No reverse gear? - YES but not usually a problem.
3) How do they cope with relatively low torque outputs - do you just have to rev them to death - YES, they are not low torque, they just operate over a wider rev range just like a performance car engine does, just choose your revs according to the state of tune and rev range of the engine.
4) Presumably no more economical to run (MPG/servicing) than a car engine? NO
5) About the same price to buy (or are they more expensive)? SOME are more to buy but when you look at it from a pounds/bhp they vare very cheap compared to tuning say a Vx or Duratec engine to make a car perform the same. Don't forget they come with 6 speed seq gearboxes as standard ! (A standard Westfield/Dax Hayabusa with 175ish bhp will perform on track similar to a 215-220bhp Vx/Duratec car)
6) Do bike engines have catalytic converters these days? SOME do but you can add one if you need it for SVA
7) Do you have to go for water cooler bike engines? NO but how much work do you want to invent for yourself ? Using an air cooled engine will make less power and need additional cooling . . . not a great idea unless you already happen to have an air cooled 200bhp engine looking for a home ?
8) Do you need to swop in a larger altenator to power more kit? (I might like a radio and an alarm)? Get a good battery but if you want a radio in the car maybe a BEC isn't right for you ?
9) Assuming sensible use, would a bike engine last as well as a modern car engine (say 80k miles)? 40k miles yes, at 80k I suspect it might be in need of a refresh - about £1200 depending what needs to be done.
10) Do they only work in really light kits (would they handle 900 kg?) YES, would be a mistake to use a standard bike engine in a car weighing over 750Kg unless you want to spend your whole life at max revs/throttle.
Edited by busa_rush on Saturday 1st July 16:53
Sam_68 said:
Apart from the one, brief passenger ride that you mentioned earlier, what is your experience of driving them?
None, that's it. All my experience is from running bikes. I can't agree with you on the longevity of bike engines nor on their inflexibility but I don't have the experience or any hard evidence to suggest that you're wrong... you may well be right and I'll find out when I finish my bec although for obvious reason I hope that I am right. It may well come down to, as so many things do, which one an individual likes best I guess. I agree with you that a bec isn't the ideal for a road car though and the original question could be better answered with an idea of what use the car will be put to.
Regards,
Mark
dern said:
....the original question could be better answered with an idea of what use the car will be put to.
I must admit that I jumped to some rather rash conclusions here that may have coloured my responses...I assumed from the questions about high mileage reliability, alarms and ICE, and 900kg kerb weights, that we were talking about a definite bias toward regular road use.
If you are talking about a track day weapon or limited-mileage weekend toy, much of what I said about servicing costs, piston speeds and high-mileage reliability is naturally irrelevant. You simply aren't going to rack up enough mileage for it to make a whole lot of difference!
As you'll see from my profile, I prefer a car engine (Sylva Phoenix/Clubmans Crossflow) even for a weekend toy and occasional track day machine. If I did more track days and very limited road mileage, I'd probably tip in favour of a BEC.
If it wasn't for the fact that most track days don't allow single seaters, I'd probably look at a cheap Jedi or OMS for nothing but track use and stick to car engines on the road, though.
It is very much down to personal choice, though. I used to be of the hair shirt and scourge persuasion myself, when I was in my 20's, but these days even the Elise 160 (which likes to be driven in the 3,500-7,750 rpm rev range and has relatively low gearing for a modern car) is loud enough and restless enough for me to find tiresome on longer trips.
Maybe it's middle age creeping up, but 10K miles a year behind a Fireblade engine geared for 14mph/1000 rpm with a dog box, is my idea of the sort of thing that the US is (allegedly) doing to muslims at GITMO.
Edited by Sam_68 on Saturday 1st July 21:20
Sam_68 said:
dern said:
Why would you do that though given that you'd be gearing for a top speed of 324mph?
1) To get piston and crankshaft speeds down to reasonable levels, thereby extending engine life to your entirely theoretical 250,000 miles. Piston speed (in feet per second) is one of the major factors in engine life. In the old days, magazines like Autocar used to quote figures for piston speeds...these days, the level of technical 'dumbing down' is such that most people haven't even heard of the concept. The best that you will get from the majority of BEC enthusiasts is the peal of wisdom that 'they are built to take the revs', without any real understanding of the design constraints involved. They are built to take the revs, but not at such high averagerevs as are imposed by the low gearing of a BECs, not with the expectation of doing 100K miles(let alone the 200K mileage between rebuilds that is the current benchmark for car engines) and not dragging around 500+ kilos of car and driver.
2) To give relaxed cruising at the sort of revs and noise levels that people have come to expect in modern cars. If you are willing to live with the high revs, fine, but you cannot ignore the fact that it is an issue which militates against the use of bike-type engines in cars for most people. You might be a sufficiently rabid enthusiast to live with the shortcomings because you feel that they are outweighed by the performance benefits, but to deny that there is any compromise involved is absurd.
Firstly, with all due respect Sam I think you're blindly regurgitating what you've been told and don't really understand the technical bits either. Have you actually done these piston speed calculations for example? If you had, you'd know that the smaller the engine stroke, the slower piston speed for a given engine RPM. Take an R1 engine with stroke of 52mm, at 12,000rpm the piston is travelling at 20.8 m/s. Your Rover 1.8 K Series (according to Google) has a stroke of 89mm, and at 7,000rpm guess what it's piston speed is.... 20.76m/s, exactly the same!!
Secondly. I know you've since clarified your comments and said that for a limited mileage car its not as relevant, but I can't think of anyone at all who'd compromise their kit car just to extend the engine life to 100,000 miles, let alone the 250k miles you've mentioned! These aren't every day cars and they don't appear on too many company car schemes, so they aren't going to be doing high annual mileage. I reckon less than 1 in 50 kit cars (of any kind) gets driven over 10,000 miles a year let alone the 30k+ you'd need to do annually to ever think about troubling your 250k target, so its just not important to the vast majority of owners. Even if you are straining the engine more, the vast majority would also happily replace/rebuild an engine after 5 years of hard uncompromised driving even if it had only done 20k miles and not bat an eyelid or think they'd been short changed, you simply cannot compare qualities / expectations people seek from a kit car to what they seek from their daily hack.
The same applies for motorway cruising, very few will do it very often, so it's not of primary concern to the majority of owners. Ive owned a BEC for 4 years now and have several good friends who also own them, plus countless others I know about from forums etc, and I have NEVER heard of a single person gearing a BEC to anything like the ratios you're suggesting, for starters without tractor tyres you couldnt achieve 17mph/1000rpm because there are no differentials numericallly low enough to achieve it with regular wheels/tyres, and secondly if you did gear for 17mph/1000rpm in top gear, you'd be able to do over 100mph in FIRST and would struggle mightily to pull away without frying the clutch. Most will aim for ~10-12mph/1000rpm in top which means it will top out at around 120-130mph. OK so its not ideal for cruising on the motorway at 7-8k rpm, but at the same time you can't compare it to how a car engine sounds / feels at the rame rpm, a bike engine at 7k is as smooth and stress free as a car engine at 3.5k (partly because piston speeds are similar!), so its not anywhere near as bad as you suggest.
Sorry if this sounds like a bit of a rant at you, but I honestly think that you're way off track with pretty much everything you've said there.
Chris
Edited by Locoblade on Wednesday 5th July 22:31
A very brief response, Chris, 'cos I'm in a rush:
1) Yes, I'm aware of the comparative piston speeds between the K series and a typical bike engine.
2) My point with piston speeds was that one should not expect the intergalactic mileages of 100K-250K being suggested by Dern.
3) Engine wear is clearly not all about piston speed. Bottom end wear is partly about piston speed. Top end wear (to camshafts, valve guides etc), is more directly rev related (coupled to valve lift and steepness of camshaft profile, obviously).
4) You are correct to state that the K series experiences similarly high piston speeds at high revs. VHPD K-series engines in Elises and Caterhams (190bhp spec, etc.) need regular rebuilds too, and are similarly incapable of the sorts of very high mileages being bandied about. I would expect the engine in a Sport 160 Elise (which is nothing like as highly stressed as the 190bhp versions) would be pretty shagged by about 60K miles, too.
I don't consider myself an engine specialist (my speciality has always been suspension design and set up), but I have built racing Imp engines capable of over 120bhp/litre, so I don't consider myself a complete numpty!
1) Yes, I'm aware of the comparative piston speeds between the K series and a typical bike engine.
2) My point with piston speeds was that one should not expect the intergalactic mileages of 100K-250K being suggested by Dern.
3) Engine wear is clearly not all about piston speed. Bottom end wear is partly about piston speed. Top end wear (to camshafts, valve guides etc), is more directly rev related (coupled to valve lift and steepness of camshaft profile, obviously).
4) You are correct to state that the K series experiences similarly high piston speeds at high revs. VHPD K-series engines in Elises and Caterhams (190bhp spec, etc.) need regular rebuilds too, and are similarly incapable of the sorts of very high mileages being bandied about. I would expect the engine in a Sport 160 Elise (which is nothing like as highly stressed as the 190bhp versions) would be pretty shagged by about 60K miles, too.
I don't consider myself an engine specialist (my speciality has always been suspension design and set up), but I have built racing Imp engines capable of over 120bhp/litre, so I don't consider myself a complete numpty!
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