Maximum Torque Per Litre
Discussion
What sort of fuel are the above engines running?
Is it true to say that vol eff and compression ratio are the 2 dominant features in making the highest specific torque?
I'm really enjoying this thread! As someone with a 1st in motorsport engineering and now working in powertrain I wish university taught more about powertrain fundamentals instead of 2 design modules every year and just filler for the test!
Is it true to say that vol eff and compression ratio are the 2 dominant features in making the highest specific torque?
I'm really enjoying this thread! As someone with a 1st in motorsport engineering and now working in powertrain I wish university taught more about powertrain fundamentals instead of 2 design modules every year and just filler for the test!
Nick1point9 said:
What sort of fuel are the above engines running?
Is it true to say that vol eff and compression ratio are the 2 dominant features in making the highest specific torque?
I'm really enjoying this thread! As someone with a 1st in motorsport engineering and now working in powertrain I wish university taught more about powertrain fundamentals instead of 2 design modules every year and just filler for the test!
Nick,Is it true to say that vol eff and compression ratio are the 2 dominant features in making the highest specific torque?
I'm really enjoying this thread! As someone with a 1st in motorsport engineering and now working in powertrain I wish university taught more about powertrain fundamentals instead of 2 design modules every year and just filler for the test!
You have about nailed it here. Compression and VE rule.
As for teaching you stuff you can use at university I understand your predicament.
You need to be learning from someone who is immersed in the subject of winning racing by virtue of experience at doing so.
May I tactfully suggest attending one of my seminars??
www.davidvizardseminars.com.
Just check to see what big time race winner Dave Mountain has to say about my teachings.
DV
Although for completeness and accuracy we should also mention the critcial parameters of surface area to volume ratio, burn rate, combustion stability and engine friction (both direct and parasitic)
Assuming you have got a nice full chamber (high vol eff = high charge density (assuming WOT)), and you compress it to a nice small volume, how you burn it becomes critical!
You need to burn the complete charge at the smallesty volume possible for two main reasons:
1) This gives you the lagest effective expansion ratio (allows the piston to extract the maximum possible Heat from the charge)
2) This Minimises the Heat lost to the chamber walls.
Do do this you need to burn the charge as fast as possible within the peak cylinder pressure limits. Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
So now you have the most energy transfered to the piston as possible, now you have to turn it (pun intended) into useful rotational work. And here engine friction is you enemy. The lower the total engine frictional losses(FMEP) the higher the useful work (BMEP) from any given indicated pressure (IMEP).
Two routes exist for this:
1) operate at low speed so total friction is low (the "prime mover" approach)
2) design your engine for low friction at high speed (the "F1" approach)
F1 engines rule the roost here by some margin, making > 120Nm/l at over 17krpm!! Whereas a road car engine (Ferrari 458 etc) might just manage this at 8krpm, doing the same at over twice the crankshaft rotational velocity is incredible.
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
Assuming you have got a nice full chamber (high vol eff = high charge density (assuming WOT)), and you compress it to a nice small volume, how you burn it becomes critical!
You need to burn the complete charge at the smallesty volume possible for two main reasons:
1) This gives you the lagest effective expansion ratio (allows the piston to extract the maximum possible Heat from the charge)
2) This Minimises the Heat lost to the chamber walls.
Do do this you need to burn the charge as fast as possible within the peak cylinder pressure limits. Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
So now you have the most energy transfered to the piston as possible, now you have to turn it (pun intended) into useful rotational work. And here engine friction is you enemy. The lower the total engine frictional losses(FMEP) the higher the useful work (BMEP) from any given indicated pressure (IMEP).
Two routes exist for this:
1) operate at low speed so total friction is low (the "prime mover" approach)
2) design your engine for low friction at high speed (the "F1" approach)
F1 engines rule the roost here by some margin, making > 120Nm/l at over 17krpm!! Whereas a road car engine (Ferrari 458 etc) might just manage this at 8krpm, doing the same at over twice the crankshaft rotational velocity is incredible.
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
Max_Torque said:
Although for completeness and accuracy we should also mention the critcial parameters of surface area to volume ratio, burn rate, combustion stability and engine friction (both direct and parasitic)
Assuming you have got a nice full chamber (high vol eff = high charge density (assuming WOT)), and you compress it to a nice small volume, how you burn it becomes critical!
You need to burn the complete charge at the smallesty volume possible for two main reasons:
1) This gives you the lagest effective expansion ratio (allows the piston to extract the maximum possible Heat from the charge)
2) This Minimises the Heat lost to the chamber walls.
Do do this you need to burn the charge as fast as possible within the peak cylinder pressure limits. Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
So now you have the most energy transfered to the piston as possible, now you have to turn it (pun intended) into useful rotational work. And here engine friction is you enemy. The lower the total engine frictional losses(FMEP) the higher the useful work (BMEP) from any given indicated pressure (IMEP).
Two routes exist for this:
1) operate at low speed so total friction is low (the "prime mover" approach)
2) design your engine for low friction at high speed (the "F1" approach)
F1 engines rule the roost here by some margin, making > 120Nm/l at over 17krpm!! Whereas a road car engine (Ferrari 458 etc) might just manage this at 8krpm, doing the same at over twice the crankshaft rotational velocity is incredible.
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
Good post here - saved me a lot of time!!!Assuming you have got a nice full chamber (high vol eff = high charge density (assuming WOT)), and you compress it to a nice small volume, how you burn it becomes critical!
You need to burn the complete charge at the smallesty volume possible for two main reasons:
1) This gives you the lagest effective expansion ratio (allows the piston to extract the maximum possible Heat from the charge)
2) This Minimises the Heat lost to the chamber walls.
Do do this you need to burn the charge as fast as possible within the peak cylinder pressure limits. Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
So now you have the most energy transfered to the piston as possible, now you have to turn it (pun intended) into useful rotational work. And here engine friction is you enemy. The lower the total engine frictional losses(FMEP) the higher the useful work (BMEP) from any given indicated pressure (IMEP).
Two routes exist for this:
1) operate at low speed so total friction is low (the "prime mover" approach)
2) design your engine for low friction at high speed (the "F1" approach)
F1 engines rule the roost here by some margin, making > 120Nm/l at over 17krpm!! Whereas a road car engine (Ferrari 458 etc) might just manage this at 8krpm, doing the same at over twice the crankshaft rotational velocity is incredible.
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
Pumaracing said:
Any comments on the cross plane crank deal Mr Vizard or whatever other reasons V8s seem to make more torque per litre than smaller cylinder flat plane inline 4s with 2Vs per cylinder?
Actually 'no' on this one Dave. i have given it a lot of thought as to whether there is some advantage in the exhaust system or whatever to a two plane crank instead of a single plane on a V8. Unfortunately I don't even like my own theories on this so you would probably have a field day with them. The ProStock guys have tried them and have failed to meet the power figures they already had. Now this does not mean an absolute point is being proved here but it does give us a good pointer on which to base ideas on.
Let's start the ball rolling on this one as I would like to know - or at least have a functional idea.
Let's have your in depth thoughts on this one Dave.
DV
Max_Torque said:
Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
A small note.. many high rpm engines like F1 have relatively high ignition advance numbers and many of them doesn't exactly have fast (enough) burn to be optimal. 
Max_Torque said:
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
I REALLY hope that's not the benchmark of today. Even our hardly-tuned Toyota 2JZ 3-liter turbo engine makes 823 Nm to the wheels with ease on a low boost tune, and many are far, far beyond this. That's 274.3Nm/Liter for a spark ignition drift car engine built to last more or less indefinitely. David Vizard said:
Actually 'no' on this one Dave. i have given it a lot of thought as to whether there is some advantage in the exhaust system or whatever to a two plane crank instead of a single plane on a V8. Unfortunately I don't even like my own theories on this so you would probably have a field day with them.
The ProStock guys have tried them and have failed to meet the power figures they already had. Now this does not mean an absolute point is being proved here but it does give us a good pointer on which to base ideas on.
Let's start the ball rolling on this one as I would like to know - or at least have a functional idea.
Let's have your in depth thoughts on this one Dave.
DV
On the crank itself I have nothing additional to what I posted at the start of the thread. On the torque figures in general I think there may be several reasons why the V8 does so well compared to most of our 4s.The ProStock guys have tried them and have failed to meet the power figures they already had. Now this does not mean an absolute point is being proved here but it does give us a good pointer on which to base ideas on.
Let's start the ball rolling on this one as I would like to know - or at least have a functional idea.
Let's have your in depth thoughts on this one Dave.
DV
Very few inline 4s I can think of have heads that can be modified really well and even fewer have both high flowing ports and a good chamber design. I can get an awful lot of airflow out of a Ford CVH head, the most of any head I've ever modified, but the hemi chamber kills any chance of a good burn. The Pinto with filled ports is not a bad compromise but even with a dry sump and all the other fancy bits thrown at it the engine in your Pinto book only just scraped over 80 ft lbs per litre and the Chevies seem to manage that without trying hard.
The Peugeot 205 and VW Golf have ok chamber shapes but aren't downdraft enough for really decent flow figures and you find a waterway if you try to get the Golf head to flow well. The Ford Crossflow has quite nice ports but a terrible chamber.
I suspect the sheer amount of development thrown at the Chevy engine over the years and the ready availability of custom made CNC ported heads with good wet flow and nice chamber design makes it much easier to achieve good power and torque than we can over here with modified OE heads on average 4 pot engines, none of which obviously have any custom made head castings available for them.
However even with all this factored in it should still be possible to get good torque figures from a 4 pot even if the outright power per litre is limited by head flow. Given that they seem to hit a brick wall at about 80 ft lbs I'm still left thinking the crossplane crank or the absolute cylinder size must be factors in the Chevy equation.
If cylinder size is a factor then you can hopefully tell us how BB Chevies compare to SB ones. Do they produce even more torque per litre or does it go down? Maybe we can at least eliminate that variable.
Getting above a certain torque output per litre is difficult, from my observations and experience with the Opel 2400 cih engine it is possible to get 100 Newtonmetres per litre and about 90 bhp per litre.
Filling the bottom of the inlet ports gives some extra torque and better low-rpm response/driveability, like taking full throttle from 2500 rpm instead of 3500.
The torque and power curves are not peaky, with useable power from 2500 to 6500, peak power comes at 5900 and stays there till 6500, then at 6800 it is "game over".
Last year, we did some testing at my usual dyno, altering cam-timing, ignition, filled the intake-ports, and fitted bigger downpipes, the old ones were 44,5 mm (1,75 in) and the new ones are 50,8 mm (2 in)
The torque and power were 250 nm and 170 bhp before and 256 nm and 190 bhp after the tune-up.
So it was well worth the trouble :-)
Filling the bottom of the inlet ports gives some extra torque and better low-rpm response/driveability, like taking full throttle from 2500 rpm instead of 3500.
The torque and power curves are not peaky, with useable power from 2500 to 6500, peak power comes at 5900 and stays there till 6500, then at 6800 it is "game over".
Last year, we did some testing at my usual dyno, altering cam-timing, ignition, filled the intake-ports, and fitted bigger downpipes, the old ones were 44,5 mm (1,75 in) and the new ones are 50,8 mm (2 in)
The torque and power were 250 nm and 170 bhp before and 256 nm and 190 bhp after the tune-up.
So it was well worth the trouble :-)
SWR Performance said:
Max_Torque said:
Something like an F1 engine (or a large prime mover engine!) is efficient because MBT timing falls very close to TDC. The more you have to retard the ingition (to avoid over pressure, or detonation, or simply to allow enough time for the charge to completely burn) the worse the efficiency of the system. Using cylinder pressure data to define the 10,50, and 90% burn angle is critical in developing an effective combustion system. The other advantage of a fast burn is that it precludes the possibility for detonation and pre-ignition phenomena. (the charge can't sympathetically ignite in the end gas region if it has already burnt when P&T increase!)
A small note.. many high rpm engines like F1 have relatively high ignition advance numbers and many of them doesn't exactly have fast (enough) burn to be optimal. Max_Torque said:
Of course the other option, and one now being taken up across the board is simple to use forced induction to increase the engine's volumetric efficiency far far beyond that availible from simple dynamic ram effects. Modern common rail compression ignition engines are the current benchmark. Although only hitting manifold volumetric efficiency values in the low 80's, due to the high boost pressures (>2bar gauge these days) they often have 160% engine vol eff. Combined with high effective compression ratio's (geometric CRs have fallen to limit Pmax), slow speed operation, and fast burn rates (direct injection with controlled burn profile with multiple pre/post injection events (up to 7 or 8 on the latest EMS) massive specific torque outputs are now possible (BMW 550d: 172 lb.ft/litre 247Nm/litre !!)
I REALLY hope that's not the benchmark of today. Even our hardly-tuned Toyota 2JZ 3-liter turbo engine makes 823 Nm to the wheels with ease on a low boost tune, and many are far, far beyond this. That's 274.3Nm/Liter for a spark ignition drift car engine built to last more or less indefinitely. Not entirely true. Yes, due to the high crank speed and corresponding short time period availible for combustion, the MBT ignition point somewhat is further advanced from TDC in the crank angle domain. But if you work out the mass fraction burn from the heat release data you still find that the F1 combustion system is very very fast burning (hence it makes massive torque at super high speed) In fact, typical ignition angles are very close to those for an engine going 2 times slower!
RE: Toyota turbo.
And is suppose your engine meets all the worldwide emissions standards, does 20k miles between services, passes an EU/Federally mandated driveby noise test, does 45mpg when cruising, runs on all types of fuel, starts and drives perfectly between -30degC and +50degC and from sea level to 3500m, develops peak torque across 85% of it's rev range, is durable to >100kmiles, and can be built in minutes for a low price.
No? Thought not!
That's the thing about modern production engines, Yes, their basic specific output can be easily beaten, but it's all the other stuff they manage at the same time that marks then out as special ;-)
(and also the reason the development of a new engine architecture will set its maker back by something larger than £500M these days!)
Max_Torque said:
RE: F1.
Not entirely true. Yes, due to the high crank speed and corresponding short time period availible for combustion, the MBT ignition point somewhat is further advanced from TDC in the crank angle domain. But if you work out the mass fraction burn from the heat release data you still find that the F1 combustion system is very very fast burning (hence it makes massive torque at super high speed) In fact, typical ignition angles are very close to those for an engine going 2 times slower!
Yes. But still they have to run angles that put them at the point of diminishing returns, any increase in airflow that increase the lead needed for MBT timing lead to a loss of power. And I would think the increased potential for fast burn due to inchamber turbulence should increase to a degree that would dictate an optimum igition point far lower than we see today.Not entirely true. Yes, due to the high crank speed and corresponding short time period availible for combustion, the MBT ignition point somewhat is further advanced from TDC in the crank angle domain. But if you work out the mass fraction burn from the heat release data you still find that the F1 combustion system is very very fast burning (hence it makes massive torque at super high speed) In fact, typical ignition angles are very close to those for an engine going 2 times slower!
Max_Torque said:
RE: Toyota turbo.
And is suppose your engine meets all the worldwide emissions standards, does 20k miles between services, passes an EU/Federally mandated driveby noise test, does 45mpg when cruising, runs on all types of fuel, starts and drives perfectly between -30degC and +50degC and from sea level to 3500m, develops peak torque across 85% of it's rev range, is durable to >100kmiles, and can be built in minutes for a low price.
No? Thought not!
That's the thing about modern production engines, Yes, their basic specific output can be easily beaten, but it's all the other stuff they manage at the same time that marks then out as special ;-)
(and also the reason the development of a new engine architecture will set its maker back by something larger than £500M these days!)
Still, you just said "it is the benchmark of today" ... no criteria beyond that was mentioned in your post. And is suppose your engine meets all the worldwide emissions standards, does 20k miles between services, passes an EU/Federally mandated driveby noise test, does 45mpg when cruising, runs on all types of fuel, starts and drives perfectly between -30degC and +50degC and from sea level to 3500m, develops peak torque across 85% of it's rev range, is durable to >100kmiles, and can be built in minutes for a low price.
No? Thought not!
That's the thing about modern production engines, Yes, their basic specific output can be easily beaten, but it's all the other stuff they manage at the same time that marks then out as special ;-)
(and also the reason the development of a new engine architecture will set its maker back by something larger than £500M these days!)
So my post is still valid, we were talking of the torque values possible per liter. And I doubt most other modified engines as herein mentioned follow the criteria you now mentioned. 
And, production cars of today starting perfectly at -30ºC? That will be in the lab. Last winter we saw the true facts of that here.
SWR Performance said:
And, production cars of today starting perfectly at -30ºC? That will be in the lab. Last winter we saw the true facts of that here.
You only have to look to Alaska and huge areas of Canada to see that pretty much every OEM who sells cars and trucks there can successfully operate them down to -40.GavinPearson said:
ou only have to look to Alaska and huge areas of Canada to see that pretty much every OEM who sells cars and trucks there can successfully operate them down to -40.
Well, last winter many cars still under warranty here, i.e. less than 5 years old, had to be towed, placed inside and heated for them to even start. We had -35ºC for a week, below -22 for months on end, and my friend who is a technician at Ford here said they had close to 800 rather new cars coming in refusing to start in a 3 month period. While older vehicles started with far bigger reliability.. That coldest week they spent all that week stuffing the dealership with frozen cars and starting them, the mechanics did NO other work for a week. I saw that with my own eyes, so I'm not quite sure I'll trust them to -40 at a cabin in the mountains without having a snowmobile handy...If you take a quick look at the owners manual, there is specific things regarding climatic conditions. Oil viscosity for one. Operator error is the greatest failing of the motoring public. Drive car short journey, lights on, heated rear screen on, heater on. Turn engine off. Attempt to restart in the morning. Surprise surprise!
The OEM manufacturers have far greater capacity to produce better engine that the tuning community, don't kid yourself otherwise. The thing is, it is not their market or business to do so.
The OEM manufacturers have far greater capacity to produce better engine that the tuning community, don't kid yourself otherwise. The thing is, it is not their market or business to do so.
SWR Performance said:
Well, last winter many cars still under warranty here, i.e. less than 5 years old, had to be towed, placed inside and heated for them to even start. We had -35ºC for a week, below -22 for months on end, and my friend who is a technician at Ford here said they had close to 800 rather new cars coming in refusing to start in a 3 month period. While older vehicles started with far bigger reliability.. That coldest week they spent all that week stuffing the dealership with frozen cars and starting them, the mechanics did NO other work for a week. I saw that with my own eyes, so I'm not quite sure I'll trust them to -40 at a cabin in the mountains without having a snowmobile handy...
stevesingo said:
If you take a quick look at the owners manual, there is specific things regarding climatic conditions. Oil viscosity for one. Operator error is the greatest failing of the motoring public. Drive car short journey, lights on, heated rear screen on, heater on. Turn engine off. Attempt to restart in the morning. Surprise surprise!
The OEM manufacturers have far greater capacity to produce better engine that the tuning community, don't kid yourself otherwise. The thing is, it is not their market or business to do so.
I'm not stupid. I know the OEM's have FAR better capabilities than the guy down the street in his garage. The OEM manufacturers have far greater capacity to produce better engine that the tuning community, don't kid yourself otherwise. The thing is, it is not their market or business to do so.
What I am talking about is that if they should be considered to "start perfectly at -30" they should have considered the fact that many users drive short journeys in winter. How many living near a major city has more than 15 minutes to the nearest shopping center or to work? If one HAS to drive for the better part of an hour to ensure a proper restart the day after, I would say the car's electrical system is marginal at best. After all, the alternator should start recharging the battery right away after a heavy start and not barely be able to feed the heater, lights, etc. and not recharge the battery at all in 15 minutes of driving time.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff