hybrid caterham. Would it ever be possible?
Discussion
Hi all,
I know a caterham with a hybrid system might sound like heresy, but I reckon the idea's got wings. A lot of petrolheads at least - including me - want a small, light car with a low-power engine you can enjoy without losing your license. But also want the ability to overtake. a 'leccy motor you can call on occasionally seems the obvious solution.
On the other hand, I love the modular nature of a caterham as opposed to the tightly integrated black-box systems on mainstream cars (well I appreciate that too - in a daily driver. Or at least I appreciate the results). Could you make a hybrid with the former approach in mind?
You'd need:
-somewhere on the drivetrain to mount a motor-generator - before or after the gearbox?
-a second clutch for the motor-generator? This is probably coming off a mainstream hybrid.
-the motor-generator itself, and associated control software, that I suspect is going to have to talk to the ECU - or more likely a single ECU that controls the engine and the motor-generator (again off an existing car). Could such a thing handle the somewhat arbitrary clutch control of a human? The honda insight coupe manages I believe.
-the batteries
I'm pretty resigned to the idea of this being difficult and beyond a single person for quite some time, the question is more whether a small company could make headway. They could pilfer existing tech from bigger companies where it's legal to do so, it's whether the packages a big company like honda develop could be adequately repurposed. I deliberately chose a problem where at least the software side is relatively simple - the motor's control logic is likely to be "engage if a button is pressed AND at full throttle, disengage when throttle is lifted", though charging logic is going to be more complicated.
Additionally, I believe hybrids often cut the alternator and starter motor out to save weight, since the motor-generator can do those jobs. Is that feasible?
I look forward to the replies (probably including one from Max_Torque)
edit: the control logic for the 'leccy motor is probably going to need some sort of check for speed as well - a reasonably powerful motor fully engaged off the lights is going to be bad news.
edit 2: it would probably be sensible to start with dropping, say, the insight drivetrain into an elise or similar. But in the long run I wouldn't trust big manufacturers to produce the appropriate hybrid drivetrain: you'll get paddle shift if you're lucky, no user repairability, crap throttle response, and a weak electric motor designed to be running near-constantly. And the only ones possible to mounted FR longitunidal will be hyper-power V8s.
Cheers.
I know a caterham with a hybrid system might sound like heresy, but I reckon the idea's got wings. A lot of petrolheads at least - including me - want a small, light car with a low-power engine you can enjoy without losing your license. But also want the ability to overtake. a 'leccy motor you can call on occasionally seems the obvious solution.
On the other hand, I love the modular nature of a caterham as opposed to the tightly integrated black-box systems on mainstream cars (well I appreciate that too - in a daily driver. Or at least I appreciate the results). Could you make a hybrid with the former approach in mind?
You'd need:
-somewhere on the drivetrain to mount a motor-generator - before or after the gearbox?
-a second clutch for the motor-generator? This is probably coming off a mainstream hybrid.
-the motor-generator itself, and associated control software, that I suspect is going to have to talk to the ECU - or more likely a single ECU that controls the engine and the motor-generator (again off an existing car). Could such a thing handle the somewhat arbitrary clutch control of a human? The honda insight coupe manages I believe.
-the batteries
I'm pretty resigned to the idea of this being difficult and beyond a single person for quite some time, the question is more whether a small company could make headway. They could pilfer existing tech from bigger companies where it's legal to do so, it's whether the packages a big company like honda develop could be adequately repurposed. I deliberately chose a problem where at least the software side is relatively simple - the motor's control logic is likely to be "engage if a button is pressed AND at full throttle, disengage when throttle is lifted", though charging logic is going to be more complicated.
Additionally, I believe hybrids often cut the alternator and starter motor out to save weight, since the motor-generator can do those jobs. Is that feasible?
I look forward to the replies (probably including one from Max_Torque)
edit: the control logic for the 'leccy motor is probably going to need some sort of check for speed as well - a reasonably powerful motor fully engaged off the lights is going to be bad news.
edit 2: it would probably be sensible to start with dropping, say, the insight drivetrain into an elise or similar. But in the long run I wouldn't trust big manufacturers to produce the appropriate hybrid drivetrain: you'll get paddle shift if you're lucky, no user repairability, crap throttle response, and a weak electric motor designed to be running near-constantly. And the only ones possible to mounted FR longitunidal will be hyper-power V8s.
Cheers.
Edited by paranoid airbag on Tuesday 25th February 10:32
I could build you that tomorrow if you wanted (or could afford it... ;-)
Two primary issues that will be "system limiting"
1) The size and weight of the batteries to get any meaningful range in a car with a terrible drag co-efficient
2) The lack of a "torque based" EMS, that means integrating the Emachine will not be seamless.
In reality, i suspect that a performance based hybrid system (a-la P1) would be the way to go, with only a couple of kWhrs of battery capacity, and a relatively low power (say 50kW) Emachine & inverter, that is continuously coupled to the crank (to avoid clutches / gears etc). In fact, replace the flywheel with the Emachine to get some weight trade off (not that flywheels on "racey" caterhams are very heavy).
I also suspect, the sensible option would be to use the system to either augment the low rpm torque curve of a small capacity, but highly tuned NA engine (say ~200bhp@9krpm), or to boost the top end power of a downsized turbo (say 1litre turbo)
To do this at minimum cost right now, you would be looking for a motor from someone like zytek or Yasa, off-the-shelf power electronics (probably Semicron) and a relatively std air cooled battery system from Axion. Basic component parts for the electric system will cost you ~£12k in low volumes.
Two primary issues that will be "system limiting"
1) The size and weight of the batteries to get any meaningful range in a car with a terrible drag co-efficient
2) The lack of a "torque based" EMS, that means integrating the Emachine will not be seamless.
In reality, i suspect that a performance based hybrid system (a-la P1) would be the way to go, with only a couple of kWhrs of battery capacity, and a relatively low power (say 50kW) Emachine & inverter, that is continuously coupled to the crank (to avoid clutches / gears etc). In fact, replace the flywheel with the Emachine to get some weight trade off (not that flywheels on "racey" caterhams are very heavy).
I also suspect, the sensible option would be to use the system to either augment the low rpm torque curve of a small capacity, but highly tuned NA engine (say ~200bhp@9krpm), or to boost the top end power of a downsized turbo (say 1litre turbo)
To do this at minimum cost right now, you would be looking for a motor from someone like zytek or Yasa, off-the-shelf power electronics (probably Semicron) and a relatively std air cooled battery system from Axion. Basic component parts for the electric system will cost you ~£12k in low volumes.
A Caterham lightweight flywheel is around 3KG. I think the problem would be packaging the system within the confines of the already limited available space. The P1 system is very sophisticated and innovative, but I just don't think the scope is there given engine and gearbox configurations.
Dave
Dave
[quote=DVandrewsI think the problem would be packaging the system within the confines of the already limited available space. The P1 system is very sophisticated and innovative, but I just don't think the scope is there given engine and gearbox configurations.
Dave
[/quote]
Having just engineered (team effort) a similar installation on a medium estate car I agree - packaging a hybrid is a VERY tricky job - a tiny Caterfield only makes life more difficult. The cooling systems for generator/inverter, battery and drive motors take up significant mass and volume too.
Dave
[/quote]
Having just engineered (team effort) a similar installation on a medium estate car I agree - packaging a hybrid is a VERY tricky job - a tiny Caterfield only makes life more difficult. The cooling systems for generator/inverter, battery and drive motors take up significant mass and volume too.
My idea of a hybrid would be a low-power Atkinson-cycle engine sized to provide road-load power up to say 80-90mph and then a large e-machine to deal with the load peaks of acceleration, gradients etc. With a low-friction, undersquare pushrod V-twin (say) with a limiting speed of 3000-4000rpm and geared to make an acceptable top speed at n_max it could be running at 220-230g/kW.h for most of its life. The e-machine and some small-ish storage capacity would give you a useable electric-only range for 80-90% of journeys and the engine directly coupled when necessary giving you "infinite" range. I'm not sure that a seven is a useful platform for this though.
edit: but you could cloak it in a light-weight, ultra-aero body to get your drag to an acceptable level to make hybrid-ing make sense.
edit: but you could cloak it in a light-weight, ultra-aero body to get your drag to an acceptable level to make hybrid-ing make sense.
Edited by AER on Tuesday 25th February 23:47
AER said:
My idea of a hybrid would be a low-power Atkinson-cycle engine sized to provide road-load power up to say 80-90mph and then a large e-machine to deal with the load peaks of acceleration, gradients etc. With a low-friction, undersquare pushrod V-twin (say) with a limiting speed of 3000-4000rpm and geared to make an acceptable top speed at n_max it could be running at 220-230g/kW.h for most of its life. The e-machine and some small-ish storage capacity would give you a useable electric-only range for 80-90% of journeys and the engine directly coupled when necessary giving you "infinite" range. I'm not sure that a seven is a useful platform for this though.
edit: but you could cloak it in a light-weight, ultra-aero body to get your drag to an acceptable level to make hybrid-ing make sense.
Yeah, maybe, but that simply wouldn't be a Caterham anymore, people like to buy the dream, once you start messing with the concept, sales will exit stage left.edit: but you could cloak it in a light-weight, ultra-aero body to get your drag to an acceptable level to make hybrid-ing make sense.
Edited by AER on Tuesday 25th February 23:47
Dave
jimbob82 said:
what about running the electric motor to drive the front wheels? it becomes 4WD then too :P
Might simplify installation somewhat if you can keep the drivetrains separate. At the same time, extra weight and awful steering? I believe pug and citroen have gone down that route before.I think I'm currently worried about thermal shock - for a battery that's only engaged for brief bursts, a fag packet calculation suggests even lead-acid wouldn't be too heavy. And overheating due to sustained use might not be a problem - I've never done a proper simulation of heat flow before but I have mates who have so might bang their ear. But rapidly heating a Li-ion even if it does stay below a "safe" temperature rings alarm bells to me.
Thanks for the names of suppliers btw
. This really isn't a plan for a torque-filling motor like a P1 - I can't imagine that ever being practical for a home mechanic or small business to calibrate. A few extra horses at a button push on the other hand...paranoid airbag said:
Might simplify installation somewhat if you can keep the drivetrains separate. At the same time, extra weight and awful steering? I believe pug and citroen have gone down that route before.
I think I'm currently worried about thermal shock - for a battery that's only engaged for brief bursts, a fag packet calculation suggests even lead-acid wouldn't be too heavy. And overheating due to sustained use might not be a problem - I've never done a proper simulation of heat flow before but I have mates who have so might bang their ear. But rapidly heating a Li-ion even if it does stay below a "safe" temperature rings alarm bells to me.
Thanks for the names of suppliers btw. This really isn't a plan for a torque-filling motor like a P1 - I can't imagine that ever being practical for a home mechanic or small business to calibrate. A few extra horses at a button push on the other hand...
easiest & cheapest option for a few extra horses with the push of a button = NOS I think I'm currently worried about thermal shock - for a battery that's only engaged for brief bursts, a fag packet calculation suggests even lead-acid wouldn't be too heavy. And overheating due to sustained use might not be a problem - I've never done a proper simulation of heat flow before but I have mates who have so might bang their ear. But rapidly heating a Li-ion even if it does stay below a "safe" temperature rings alarm bells to me.
Thanks for the names of suppliers btw
. This really isn't a plan for a torque-filling motor like a P1 - I can't imagine that ever being practical for a home mechanic or small business to calibrate. A few extra horses at a button push on the other hand...
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