Who says stock Yank motors don't make power...
Discussion
Evoluzione said:
R8VXF said:
I stand corrected, though I think my point still stands that valve events need to happen earlier in the cycle to allow the required flow at higher RPM's.
I would be interested to see how they only change one cams timing though, purely from a knowing how things work point of view, not from an argumentative point of view
Basically you just have to be able to turn the timing gear on the cam and lock it, there are a few different ways, Google it, it's no secret I would be interested to see how they only change one cams timing though, purely from a knowing how things work point of view, not from an argumentative point of view
Fiats initial stab at it is reasonably easy to explain without diagrams.They put the toothed wheel onto a helical spline on a hub on the cam, this meant as the wheel comes away from the cam it turns. They operated it by oil pressure: More RPM = higher oil pressure and so it pushed the wheel outwards, it twisted on its splines and changed the cam timing. It seems quite reliable as you don't hear of them going wrong much.
You have an actuator on the end of the cam shaft.
We explored using the Ford system on our TVR engine as it runs quite racey cams and it would have allowed is to advance the timing at the top end to make the most of the high rpms while pulling it back to retain useable torque low down.
Coatesy351 said:
RoverP6B said:
Evoluzione said:
There are a few good reasons why the Meercans still use carbs, 2v per cyl and inches - one is because they're 20yrs behind everyone else. 
They don't use carbs, haven't in donkey's years, except in NASCAR, and even there I think fuel injection is making inroads. As regards cubic inches, I find them (like most Imperial units) much more useful than the equivalent metric units.Rather than at them......
563bhp + 15-20% = 647-675bhp
530lbft + 15-20% = 609-636lbft.
Sanity test time
530/7.0=76 lbft/lt
609/7.0=87lbft/lt
636/7.0=90lbft/lt
The best current production engines are in the region of
991GT3=85lbft/lt
458Stradale=88lbft/lt
If I ever see a dyno plot, the first thing to do is do the sanity check.
Anything above 80lbft/lt is very good for a homologated road engine.
Anything above 85lbft/lt is excetional for a homologated road engine and what should be expected for a decent tuned engine.
Anything above 90lbft/lt is generally unobtainable to anyone without a development budget which would buy the 911 and 458 together, or BS.
I think they are flywheel figures.
530lbft + 15-20% = 609-636lbft.
Sanity test time
530/7.0=76 lbft/lt
609/7.0=87lbft/lt
636/7.0=90lbft/lt
The best current production engines are in the region of
991GT3=85lbft/lt
458Stradale=88lbft/lt
If I ever see a dyno plot, the first thing to do is do the sanity check.
Anything above 80lbft/lt is very good for a homologated road engine.
Anything above 85lbft/lt is excetional for a homologated road engine and what should be expected for a decent tuned engine.
Anything above 90lbft/lt is generally unobtainable to anyone without a development budget which would buy the 911 and 458 together, or BS.
I think they are flywheel figures.
Wow! What an amazing load of optimistic horsepower b
ks in one thread.
When you can pull any number you like out of your arse dyno, it makes no sense comparing anything beyond counting how many sparkplugs it has, although if it determines who's buying the next round of drinks, it might be a useful number, I suppose.
The LSx series engines are quite remarkable things, but they're not miraculous. Like any widget they will have their limitations based on their architecture but this can also offer advantages. Extreme specific power is not one of them, however.
They are light, cheap, relatively small, can be arranged to have a low centre of mass and, by virtue of the low number of bits in them, have low friction for good fuel consumption potential. I don't think many of these are points that the boy racer types are interested in though, but that really is what they're good at. As race engines they are flawed and compromised.
ks in one thread.When you can pull any number you like out of your arse dyno, it makes no sense comparing anything beyond counting how many sparkplugs it has, although if it determines who's buying the next round of drinks, it might be a useful number, I suppose.
The LSx series engines are quite remarkable things, but they're not miraculous. Like any widget they will have their limitations based on their architecture but this can also offer advantages. Extreme specific power is not one of them, however.
They are light, cheap, relatively small, can be arranged to have a low centre of mass and, by virtue of the low number of bits in them, have low friction for good fuel consumption potential. I don't think many of these are points that the boy racer types are interested in though, but that really is what they're good at. As race engines they are flawed and compromised.
Edited by AER on Wednesday 29th April 04:46
AER said:
They are light, cheap, relatively small, can be arranged to have a low centre of mass and, by virtue of the low number of bits in them, have low friction for good fuel consumption potential. I don't think many of these are points that the boy racer types are interested in though, but that really is what they're good at. As race engines they are flawed and compromised.
[/footnote]
But as a mass market value for money option they are unmatched [/footnote]
R8VXF said:
That will be at the wheels if I know Surrey Rolling Road, factor in the 15-20% driveline losses on top of that figure...
So we're looking at 662-704bhp at the crank? Based on the median of those two figures, that suggests 35% more power than claimed, or else their dyno is overreading significantly, or a bit of both.swerni said:
I wouldn't call 12- 13% substantial.
I wouldn't when it's on top of 150bhp, but on top of 505bhp, you're going to feel that extra 60bhp... but can you comment on R8VXF's comment above?RoverP6B said:
R8VXF said:
That will be at the wheels if I know Surrey Rolling Road, factor in the 15-20% driveline losses on top of that figure...
So we're looking at 662-704bhp at the crank? Based on the median of those two figures, that suggests 35% more power than claimed, or else their dyno is overreading significantly, or a bit of both.swerni said:
I wouldn't call 12- 13% substantial.
I wouldn't when it's on top of 150bhp, but on top of 505bhp, you're going to feel that extra 60bhp... but can you comment on R8VXF's comment above?Manufacturers do not homologate engines at 80% of their true power, why would they. If GM could homologate the engine in the Corvette at 700hp, they would. Think of the marketing value in such a figure.
Even if it really is 563bhp, which I doubt as rolling roads are not accurate means of delivering measured flywheel power, a 10% difference would be on the outside of where you might expect to see the best engines. And that would be in the case of GM homologating the worst engines off the production line in order to ensure all customers have at least 505bhp.
stevesingo said:
That is not a wheel horse power figure! Unless you are so delusionally blinded by you love of OHV V8 engines.
Chill out mate, I only said that as SRR generally don't like giving fwhp figures in my experience. I don't know whether swerni has a stock motor or not, so just assumed not. I don't have a blind love of OHV engines, I just like the LSA I have in my VXR8. Gonna get a V12V in a couple of years to go alongside it.
I also currently have an E46 320cd and a VX Corsa 1.2 SXi Twinport. Now that has just reminded me of another tech we haven't spoken about yet. Valve deactivation. At low RPM the twinport works on 2 valves per cylinder activating the other two at 3700 rpm. It is a proper hoot to drive and you have to be in the right gear at all times else you ain't getting anywhere unlike the GTS that can go from 15-130 mph in 4th without feeling like it is bogging down anywhere. As someone said the other day, it is relentless.
stevesingo said:
That is not a wheel horse power figure! Unless you are so delusionally blinded by your love of OHV V8 engines. Manufacturers do not homologate engines at 80% of their true power, why would they. If GM could homologate the engine in the Corvette at 700hp, they would. Think of the marketing value in such a figure.
I was just responding to the other poster who said take the figure quoted and then add in the 15-20% driveline losses on top of that. Manufacturers often sandbag over power output - Porsche is well-known for so doing, and BMW F10 M5 owners have reported their cars topping 600hp on the dyno when the book figure is 552PS. Chrysler, meanwhile, with its Hellcat range, quotes 707hp and 650ftlb, but dynos are picking up quite a bit more than that (MotorTrend got 635whp and 591wtq on K&N's pretty accurate dyno, so reckon on 747hp/695ftlb at the crank - a subsequent MT dyno test elsewhere saw consistent results of 666-672whp/604/606wtq, which is probably down to dyno optimism - in all cases, it was running Chrysler's 8-speed TorqueFlite autobox, which is a license-built copy of the ZF 8HP) - and a Jalopnik article has stated that (according to an anonymous Chrysler insider), with a MAF sensor and wideband O2 sensor rather than its usual MAP sensor, they're able to reduce emissions significantly, such that power raises (to as much as 825bhp) could be in the offing... all unverified at the moment, of course, but it'll be interesting to see how they get on... swerni said:
Ever driven a 500+ BHP car weighing 1400kgs? 60bhp is going to make very little difference.
No, I haven't. I would still have thought you'd feel it...R8VXF said:
RoverP6B said:
swerni said:
Regarding those saying the dyno test wasn't representative - you've got to have an alternator and battery to run the ECU, ignition, injection etc, and the lack of an exhaust only compensates for the lack of a proper induction system having air rammed into it by the car's motion...
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