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Generic question on longevity of modern automotive engines at high load
2

Generic question on longevity of modern automotive engines at high load

Generic question on longevity of modern automotive engines at high load

(OP)
This is a "what-if" question - asked mainly out of curiosity, not because I need to implement any of the scenarios mentioned.

Consider a modern European hatchback designed for fuel efficiency and low price - so low displacement turbocharged engine is the order of the day. Say, 1.0-1.5 liter 4-cylinder petrol engine making 100-200 bhp with turbo. And in a car that weighs about 1200kg. Top speed of around 200 km/h.

Question 1 - imagine the car is driven for several hours daily on the Autobahn, at its top speed. How long would it be expected to last? Which component would fail first? Are cars of this size even designed with enough natural cooling capacity to withstand several hours of full throttle operation?

Question 2 - imagine the same automotive engine, but this time driving a stationary load (like a generator or water pump), or used as a boat inboard engine, or an aircraft engine. In each case assume the engine has sufficient cooling (via cold water supply or oversize radiator), no unnatural axial loading on crankshaft (i.e. propeller thrust loads borne by thrust bearing not directly loaded on crankshaft), and engine spends all its time at 80-100% of rated power. How long will it last this time, and which component fails first?

Reason I'm asking is because modern automotive engines strike me as taking advantage of the fact that full power is used only briefly in a car's typical operation, so they have very impressive specific power figures (over 100hp/liter) - but I can find no data on how durable they are when producing high power for extended periods of time. I'm hoping some automotive engineers can shed light on this question.

P.S. This being my first post, I should probably introduce myself and provide some background. I'm from Malta, have a B.Eng in mechanical engineering and a masters in materials engineering. My current job is package development for a semiconductor assembly plant, main focus being R&D of novel MEMS device assembly processes.

RE: Generic question on longevity of modern automotive engines at high load

Some components of a recip auto engine will be life limited by dynamic fatigue load cycles from high speed operation, such as valve springs or conrods. Other components will be life limited by the high combustion pressures and temperatures at high load operation, like pistons or exhaust valves. And other components like fuel injectors may have a service life mostly based on number of cycles, and largely independent of how the engine itself is operated.

RE: Generic question on longevity of modern automotive engines at high load

1. If the car is sold in Germany, it had better survive the warranty.
2. Similarly for generator or marine propulsion, provided that the installation is properly engineered.

In the specific case of generators, Diesels in particular thrive at sustained power levels of 60 to 90 pct of maximum rating, and develop congestion in various forms at lower power levels.

In the specific case of aircraft propulsion, the maintenance schedules for piston engines are so rigorous that none of the parts have a chance to get old, and even the established manufacturers have no experience with really high-time engines. They don't know how to build one because they've never, ever, been forced to do so.

Emissions- related durability testing has forced evolution of car engines that will last for 100,000 miles, and has forced evolution of design tools and manufacturing techniques that allow rapid development of new engines with similar prescribed durability.

The question you may have meant to ask is, 'What happens after 100,000 miles or equivalent?'.

I don't think anyone really knows. Big ol' 'Merican engines used to cruise well beyond that, given even minimal maintenance, but they can't meet the increasingly crazy emissions regs.


My personal suspicion is that new generations of tiny engines, their power level and effective displacement and internal stresses magnified on demand by turbochargers, will meet the statutory durability requirements. ... and then explode, as every part reaches its carefully calculated fatigue end of life at the same time.

It won't matter which part actually fails first, because collateral damage at high power will take out the remainder of the engine, or there will be no fatigue life left in the surviving remainder. It won't be worth repairing a failed engine, because every part in the junkyard will be within minutes of its end of life.

There won't be a need for junkyards, because everyone will be forced to buy either a brand new engine or a new car when the engine grenades.

<tangent>
Big ol' engine example:
I was not long ago involved in the zero-time rebuild of a pair of Waukesha natural gas engines retrieved from a junkyard (for $25,000 each), which will run at 900 rpm for the next 35 years providing up to 350kWe each, on an unattended oil platform in the GOM. The bare engines weigh 20,000 lbs. each, so they might be a little impractical for a hot rod. They do make a nice chest-thumping bark when you fire 'em up, though.
</tangent>

Mike Halloran
Pembroke Pines, FL, USA

RE: Generic question on longevity of modern automotive engines at high load

Interesting question.

A little out of date now but IIRC, Triumph engineers in the 60s were aiming for engine survival of 50 hours at full power.

Against this, 100,000 miles @ 30 mph average would give 3,333 running hours (though dependent on ownership, might never actually see full power use). I also always think it is interesting to compare the running hours at higher average speeds (45 mph average drops the hours to 2,222), which perhaps goes some way to demonstrate why a relatively young, but high mileage car (implying it's done longer runs at higher speeds) is usually a less troublesome buy than an older, low miles car and will run to a higher mileage before failure.

This would also help to explain why big countries (US, Oz, mainland Europe etc) seem to report higher survival mileages than we UK Island Monkeys, where opportunities to sit at high cruising speeds for long periods are more limited.

I realise there are alot of sweeping generalisations here, but my personal experiences in almost 30 years of used car ownership have shown that well maintained high mileage cars remain reliable to very high mileages and it's rarely the engines that fail first.

Another wrinkle is how powerful the engine is in the first place, which obviously goes a long way to dictating how far up its power band it will be operated. I suspect that manufacturers are well aware of this and build their small engines tougher/hp than their big ones.

My first car was a Citroen Dyane with a 602cc flat twin and 29 snorting horses. That was driven with two throttle positions, on or off, and high rpms were needed to maintain progress. It could only manage just over 70 mph flat out so I can safely say that that car did get operated at full power for quite substantial chunks of time. It was admitting to 97k miles when I got it and I added about 5k more. It was still running when sold, but was showing signs of wear!

My current car is a '96 Audi A6 with a 2.5L I5 TDI. It is rated at 140 hp and while it has seen full power use on plenty of occasions, I don't think I've ever managed to hold full power for more than about 90 seconds continuously and then only when overtaking trucks on long hills. It just isn't possible (in UK at least) to hold full power for any longer without running out of road or seriously breaching speed limits. This car is now approaching 256k and engine-wise gives the impression that if I keep doing the scheduled maintenance, it'll double that. The body won't last that long though!

My feeling is that that car engines at least, cold starts, temperature cycling and lack of maintenance kills far more than the actual mechanical wear of hard use. Plenty of engines get scrapped in perfect working order too - I've recycled a few in my time.

Cheers

Nick

RE: Generic question on longevity of modern automotive engines at high load

I have a Honda CBR125 motorcycle, which is also only operated with two throttle positions (open and closed), necessary for its 12 horsepower to make it go anywhere, and usually pretty close to redline, too. I've seen these with over 60,000 km with only oil changes. (Mine has about 20,000 and runs like new)

But, that engine has much lower maximum revs than, say, a CBR600, even though its cylinder is smaller than those in the 600.

I have heard of a street ridden CBR600 in the southern US with over 260,000 miles on it (> 400,000 km) and it has reportedly never been apart.

I recall one of the UK magazines years ago ran a Honda Fireblade at top speed at MIRA for (I think) 24 hours and then tore down the engine, and found no wear. That engine made about the same power from its 900cc as you are suggesting from a bigger engine and did it with no turbo ... it did it with revs, which is generally tougher on everything.

I'm quite sure that nowadays, engines are designed for continuous operation at maximum power while remaining within the bounds of infinite fatigue life on the materials. Lack of maintenance is what usually kills them.

RE: Generic question on longevity of modern automotive engines at high load

I asked a very similar question to this in 2006 in
thread108-150335: automotive engine performance
You can go there to see the answers.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

Whether it constitutes support for my assertions about grenade engines or not, a search on
{"Ford EcoBoost" problems}
will provide a _lot_ of reading material.
It appears that they fell just a little short of the mark, durability-wise,
and will have to add some iron, or fix some software.





Mike Halloran
Pembroke Pines, FL, USA

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Thank you all for the very useful replies.

Mike, tbuelna - do you have any idea of the longevity of an automotive engine converted to run an experimental aircraft, in terms of hours between overhauls? I'm aware of a lot of air-cooled VW beetle engines powering homebuilt microlights, and I was wondering whether it would be possible to capitalise on modern cheap, lightweight high-power turbocharged engines for an experimental microlight. Aerospace engineers will be well aware of the advantages of turbos at altitude, though with this being an automotive engine I don't know how it would cope with flying at altitude design-wise. And I'm not familiar with maintenance schedules for automotive conversions on experimental aircraft - does the owner/pilot have to come up with a suitable schedule himself, or maybe copy one from an existing similar certified piston engine?

Nick - my first car was a Ford fiesta/fusion. 1.4 liter NA petrol with 80bhp. Used to use full throttle quite often. My current car is an Alfa Romeo MiTo - 1.4 liter turbo petrol with 135bhp and MultiAir (for those not familiar with the term, MultiAir is a hydraulic valve actuation system whereby power control is done by variable intake valve duration [early intake valve closing or late intake valve opening] instead of a throttle body. That way the pumping losses are eliminated and they claim a 10-15% improvement in fuel efficiency and specific power compared to conventional (throttle-bodied) petrol engines). I barely ever have the room to use full throttle for more than 20 seconds at a time, and that's only at 2am when the roads are empty! Same engine with a bigger turbo is offered in the QV model with an output of 177bhp. So curious as to whether such an engine would make a practical experimental aircraft engine or whether it would have durability problems since getting 100hp/l means quite a high BMEP, and you'd have to run it all day at 5000rpm to get all 135 horses...

Brian - with regards to full power operation - so assuming fatigue life is infinite, is the cooling system in the car usually sufficient to permit continuous full throttle operation? Or will the engine slowly start to overheat?

Berkshire - thanks for the link. Seems a reasonable assumption is 2000 hours at full throttle, and Diesels are more suitable than petrols for extended high-power running?

RE: Generic question on longevity of modern automotive engines at high load

I know of a gentleman who powered a Cozy Mark IV aircraft with a Mazda rotary. As far as I know, his only semi-catastrophic failures (engine kept running but with no boost) were due to the stock turbo hot side wheel detaching itself from the shaft a couple of times. Apparently those turbos are not very well suited for sustained high load use.

RE: Generic question on longevity of modern automotive engines at high load

The cooling system in a car these days is designed for continuous full load ... PROVIDED that the car is moving through the air at a speed that is appropriate to the power output! It still needs an appropriate amount of cooling air coming through the radiator.

Aircraft usage demands a whole lot of considerations that are not present in an automotive application. The average aircraft piston engine is air cooled ... it's a whole lot easier to get that to pass FMEA (failure mode effects analysis). They have redundant ignition systems, etc. In my last car, once upon a time, I had a coolant hose spring a leak while on the motorway. While the car came home on a tow truck after that happened, it did in fact come home. If that happens 2 km up in the air while you are crossing mountains or a big lake ... consequently, no comment from me on the advisability or suitability of an automotive engine in an aircraft.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Brian - Coincidentally, in my previous job doing aircraft maintenance at an FBO, I had the opportunity to work on a Diamond DA42 ("twin star") with twin 170bhp Austro Diesel engines. Water-cooled, turbocharged, 4-cylinder in line - and apparently based (originally) on Mercedes 2-liter Diesels. 85 bhp/l is not bad - I think they're miles ahead of the ancient Lycoming and Continental horizontally opposed engines where a typical one in a Cessna 172 needs 9 liters of displacement for just 170 bhp. The TBO of the Diesels is quite reasonable - 1200 hours or more at this point (Link)

I never understood why aviation laws stipulate dual ignition systems (14 CFR Part 33, Subpart C, § 33.37). It's not like the ignition system is the least reliable part of the engine, at least with modern solid-state systems, in my limited experience. The CFR still permits the use of one fuel injector per cylinder (for engines that use them), one fuel pump, one oil pump, one cooling system, one radiator, one alternator, and one timing belt. So why would they be so hard on the ignition system, and require drilling two holes per cylinder for the spark plugs to make the engine qualify for certification (a requirment that an unmodified automotive engine can't meet), when they still permit single points of failure (like the single oil pump, whose failure would disable the whole engine)?

RE: Generic question on longevity of modern automotive engines at high load

MikeHalloran - your reference to the Ford Ecoboost engine/s is right on the ball.
Through industry links, I have heard that some aspects of the cooling system have been designed without much thought to manufacturing processes and the rate of degradation of the cooling system internals (casting debris, swarf, products of corrosion), resulting in coolant not necessarily being where you would like it to be.

I had a look at a sectioned display 1.0 Ecoboost - the pistons were reminiscent of racing pistons of not so long ago - very short, almost non-existent skirt. The rods, from what I could see, were nothing special - the I-section was what you'd think typical for a production engine. I gather that nearly all rods these days are laser scribed and snapped across the big end, but I also hear the odd story about b/end bolting causing failures owing to inadequately developed bolt types/torques/torqueing methods.

One has to consider that the Ford Ecoboost is currently at 100bhp/litre and the next iteration will probably be 120bhp/litre. It's not so long ago that these were racing outputs from engines that had little durability capability.

Many years ago, I was involved with the testing of truck engines in the range 254 to 380 cu in and the baseline test was, after a thorough oil consumption bed-in, 55 min at full load, rated speed, followed by 5 min at idle, no load. This was continued for at least 1000 hours and in some cases 1500 hrs.
Of course, there was no thermal cycling going on, as you would get in real use.

Bill

RE: Generic question on longevity of modern automotive engines at high load

I don't think you can paint all of the "Ecoboost" engines with the same brush. I have heard of issues with the 3.5 V6 Ecoboost in the pickup trucks, but little about the 1.0, 1.6, 2.0 three and four cylinder engines. Most of the issues that I've heard of with the 3.5 EB aren't necessarily mechanical-failure but more to do with real-world issues that didn't turn up during their validation testing like moisture condensing/freezing in the intercooler, etc. (VW is having same trouble with 2009-onward TDI engines and will be using a liquid-cooled, temperature-regulated intercooler in the next generation) Obviously hindsight suggests that this means their validation testing was half-baked and didn't cover enough ground to reveal the faults ...

The lightweight pistons in the 1.0 EB stand to reason. That engine is an inline-three with no counter-rotating balance shaft. Keeping the pistons light keeps vibration in check.

RE: Generic question on longevity of modern automotive engines at high load

Well, Brian, I'm not painting them all, just recounting conversations I've had with FMC devt engrs here in Europe re the 1.0L engine.

Bill

RE: Generic question on longevity of modern automotive engines at high load

So it's the 1.0 EB that you are mentioning, when you talk about the cooling system design issues?

The thing about the 1.0 EB that has me concerned, is the timing belt running in oil.

RE: Generic question on longevity of modern automotive engines at high load

The current favorite engine for conversion from automotive to aviation seems to be the Subaru 4 and 6 cylinder series. I have 2 friends using the 6 cylinder Subaru's in RV7 aircraft, they have 4 years and 2 years of use. The only modification they made was retrofitting larger radiators after experiencing overheating on full throttle climb outs on very hot days.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

We used to build stationary products with a load/output similar to a genset, using automotive type engines. We could load them to 80% and expect 2,000 hour + life with mostly successful results. Ford 4-cylinder, Daihatsu 3-cyl., and Nissan 4-cylinder engines I do recall surviving the life test. This was circa. 1990-2000, and the engines were naturally aspirated, not turbocharged.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Berkshire - can you provide more info on the type of Subaru engine they used? Boxer or inline? Turbo or NA? What dispacement and bhp? Was it derated? I'm assuming this was registered under "experimental" aircraft category to get around the dual-ignition regulation?

RE: Generic question on longevity of modern automotive engines at high load

LMF5000
I have two friends with RV's using the 6 cylinder boxer layout with an Eggenfellner reduction gearbox. The gearbox is controversial, people either love them, or hate them, and factory support is spotty. I will contact them this Saturday. I am doing a weight and balance for one of them, I will ask the specifics on displacement and horsepower. I have another friend with a Kitfox with a belt drive reduction 4 cylinder inline motor. He has not reported any problems with his, other than that the unit is a bit heavy for his aircraft.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Thanks, I would really appreciate the info if you could get it!

I actually have a friend who built an X-air microlight a few years ago. He spent €10,000 on the aircraft and €30,000 on a two-stroke two-cylinder Rotax (about 40-60bhp I think) to power it. From the little time I spent with it, the engine is not terribly impressive. Quite hard to start (prop spins but engine doesn't fire), though reliable enough once it's actually started. Sadly an automotive power plant wouldn't come anywhere near the light weight of this one due to being 4-stroke and liquid cooled. Probably the best bet would be an air-cooled motorbike engine, but not too convinced one would last long at a constant 10,000rpm...

RE: Generic question on longevity of modern automotive engines at high load

Quote (LMF5000)

Mike, tbuelna - do you have any idea of the longevity of an automotive engine converted to run an experimental aircraft, in terms of hours between overhauls?

LMF5000-

The duty cycle of a recip piston aircraft engine is far different than a typical auto engine. The auto engine operates most of its life at light load and low speed operation. The recip piston aircraft engine has a duty cycle (ground-air-ground cycle) that involves a short period of high speed, high load operation during take-off and climb, followed by extended periods of operation at 60%-70% speed and full load. So it seems likely a recip piston auto engine used in an aircraft would have significantly reduced MTBR due to mechanical/thermal fatigue issues in many of its components.

RE: Generic question on longevity of modern automotive engines at high load

LMF5000,
Your friends price for a 50hp Rotax engine sounds off by a factor of 10. The highest price I can find is about 7000 euros for a 503, or 582 ,or similar with a gearbox and electric start .
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Berkshire - you're correct, that is a little high. It's a Rotax 582. Using the configurator here I recreated their setup for 10,900 CAD (€7500). Add €2000 for a carbon fiber prop, and shipping costs to Malta. Not sure what else is included in the €30k figure. I will ask next time I see him

RE: Generic question on longevity of modern automotive engines at high load

LMF5000,
The Subaru engines they are using in the RV 9's are 3 litre 6 cylinder boxer engines generating about 180 to 200 horsepower through a reduction gearbox using an MT electric constant speed 3 blade prop.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Hi Berkshire,

Thanks for getting back to me. Interesting how they both use horizontally opposed engines - as are certified engines. Perhaps they have the advantage of being lighter because of less balance weight?

Anywhay, very interesting that they use an electric constant speed prop. I didn't know they existed until you mentioned it. Only ever saw planes with fixed pitch and hydraulic CS props.

RE: Generic question on longevity of modern automotive engines at high load

You question the requirement of dual ignition systems in aircraft engines. And yes the rules are based on the old days.
When most all ignition systems used breaker points. They always were the weak point in the system, also the high tension components could be bothersome as well, all items that make redundancy a good thing. It would have been much more difficult to use 2 spark plugs per cylinder using one distributor or one magneto than it is with 2 or more.
2 spark plugs on an aircraft engine should be a necessity especially in the old days, with the higher TEL concentrations used then. Spark plug fouling was pretty common. And saying nothing about the efficiency increase with the extra ignition source.

As far as I know any durability testing on automotive engines using 100% plus of rated power are all done using precisely controlled conditions on a dynamometer. I've also questioned if the cooling system and exhaust system in the average car would withstand full power output for extended time. I think the average car uses maybe 20% of max hp in normal driving.

RE: Generic question on longevity of modern automotive engines at high load

Rule of thumb 30 years ago at two different manufacturers was that the prototype of a new design of car engine had to survive for 100 hours at full power on the dyno before the base design could be signed off, and at that point it was released to the mainstream development team. As to what the actual life of a /production/ engine at full power would be on a dyno, I don't know. As you have pointed out this is a serious bit of design overkill, real drivers in most countries spend remarkably little time at full power, for the most part (yes, I have the data). If they have autos they actually spend very little time above 60% red line. Incidentally the running-in event that killed most engines on a dyno is full revs with no or light load, reputedly.

Cheers

Greg Locock


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RE: Generic question on longevity of modern automotive engines at high load

(OP)
"Incidentally the running-in event that killed most engines on a dyno is full revs with no or light load, reputedly."

I've heard it said before that revving an engine with no load is dangerous. The (non-technical) sources I read allege that the harmonics that would otherwise be dampened by the load are instead allowed to run free and stress the engine. Personally I've never exceeded 4000 revs in neutral. I hear the modern VWs also have a drastically reduced rev limit in neutral or with the clutch pressed - though whether this is to prevent damage, or actually meant to be a primitive form of launch control I don't know.

RE: Generic question on longevity of modern automotive engines at high load

I remember reading in a contemporary Car and Driver article on the all new 1984 Corvette, that the driveline and specifically the hydraulic clutch were engineered to withstand "sidestepping" the clutch pedal... bigsmile

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Generic question on longevity of modern automotive engines at high load

I wonder what that really meant. Conceivably the hydraulics could be arranged to permit a maximum flow rate and consequently mitigate the harshness of a sidestepped clutch engagement. Beneficial for most everything but clutch disc wear, for which warranty replacement could be denied based on "abuse".


Norm

RE: Generic question on longevity of modern automotive engines at high load

Frankly the 84' Vette didn't have enough power to abuse much of anything...

RE: Generic question on longevity of modern automotive engines at high load

Some kind of flow restrictor is used in the hydraulic circuit of at least some automotive clutches. When I was an auto tech the guy in the next bay wound up putting an unsprung-hub, ceramic-metallic-puck racing clutch in an AWD Mitsubishi Eclipse as per the customer's request. Part of the job included removing some sort of restrictor in the hydraulic circuit. The clutch manufacturer (I want to say it was Clutch Masters, but it's been a long time. I remember the pressure plate was painted white) advised that sidestepping the clutch without the restrictor in place would probably result in the generation of spare parts in a hurry, and that it was only recommended for "race applications". I don't know how it was to drive, but I imagine that damned clutch snapped shut like a bear trap every time the owner pulled away from a stoplight.

RE: Generic question on longevity of modern automotive engines at high load

As I recall, the 84 Corvette sidestep manouever was described in the article as intended to give a satisfyingly hard launch and/or wheelspin.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Generic question on longevity of modern automotive engines at high load

At 240 HP it was considerably more powerful than it's predecessor (200 HP) and pretty much everything else on the American market save some exotics costing 3 times as much. It was the first multipoint EFI from Chevy. We had two in out test fleet and they were way faster than the BMWs & Jags, even the V12 XJS (which was rated for more power but must have weighed at least 1000 more pounds and was crippled by a 3 speed automatic).

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RE: Generic question on longevity of modern automotive engines at high load

dgallup, IIRC the 240 hp rating was for the later TPI engines. Early cars had less, and 84 was Crossfire-injected (two TBI units on a crossram manifold, RPO code L83). I think this gave way to an iron-headed TPI engine (RPO L98) in 85 and half of 86, and an aluminum-headed TPI from late 86 to 91. The early cars also had a Super T10 manual with a Doug Nash overdrive that could be engaged in the top 3 gears. This gave it the name 4+3. The transmissions were good but the overdrive units were trouble prone.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
I can't say I really see the point of the sidestep manoever. My first car had 80bhp and it could do burnouts just fine simply by releasing the clutch quickly (by foot) at 2000rpm and flooring it. I don't really see the point of lengthy burnouts themselves to be honest, except for purpose-built drag cars that need to warm up the slicks before a run. And for showing off, obviously ;)

RE: Generic question on longevity of modern automotive engines at high load

It is said that a sidestep engages the clutch more quickly than conventionally releasing the clutch. Put another way, the clutch can engage faster than the driver's foot can come up, so sidestepping prevents the clutch pedal from "riding" the sole of the driver's foot on the way up. I've never timed it, and I would suspect that the time difference is not very big, but sidestepping does eliminate the chance of getting your foot hung up when your snow boots and the pedal bracket of your college roommate's 1986 Z-28 try to inhabit the same space at the same time.

RE: Generic question on longevity of modern automotive engines at high load

crerus75 - Those Cross Fire dual throttle body systems were awful, I thought they were only on C3 Vetts and Camaro/Trans Am but you are right, the first year C4 had it too. Maybe our 2 C4 Vettes were prototypes or maybe they were actually 85's, definitely had port injection. That was back when Chevy had massive problems with fuel injector plugging on the small block V8's. We did a lot of testing and had a driving loop that could plug the OE injectors in about 2 weeks with high olefin fuel. Our injectors were the OES fix but you had to take your Vette back 3 times with injector problems before they would replace them. The first 2 times they just cleaned them which was totally ineffective.

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RE: Generic question on longevity of modern automotive engines at high load

Quote (crerus75)

Put another way, the clutch can engage faster than the driver's foot can come up, so sidestepping prevents the clutch pedal from "riding" the sole of the driver's foot on the way up. I've never timed it, and I would suspect that the time difference is not very big . . .
At the drag strip, the time difference to full clutch engagement is likely less important than the lower likelihood of having the clutch go into some sort of full slip condition as a result of slower engagement.

More abusive than I care to subject any of my cars to.


Norm

RE: Generic question on longevity of modern automotive engines at high load

I always thought side-stepping the clutch was to simulate an "idiot start" - one where a driver mistakenly slips off the pedal instead of releasing it progressively.

- Steve

RE: Generic question on longevity of modern automotive engines at high load

Since this thread has derailed into a discussion about abusing engines and drivelines, I'll continue the derailment by sharing a fantasy of mine that was prompted by the Home Depot pickup truck rental offer, 75 minutes for a flat rate around $20. In my fantasy, I would go to the Home Depot with floorjack, a pair of jackstands, a brick, a lawnchair, and maybe some popcorn. I would rent the truck, jack up the rear axle and support it with the jackstands, start the engine, put the transmission in drive, and place the brick on the gas pedal. Then I would sit in the lawnchair enjoying my popcorn for the remainder of the 75 minutes, with the engine bouncing against the rev limiter, and the odometer racking up miles at 100mph+ bigsmile

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Generic question on longevity of modern automotive engines at high load

(OP)
hemi - that's a good idea. The ensuing conversation (when they discover you added 125 miles in 75 minutes) would be hilarious...

Course it's based on the speedometer being connected to the driven wheels not the other axle ;)

RE: Generic question on longevity of modern automotive engines at high load

What makes you think they don't have a governor on that rental that limits it to 70 mph?

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RE: Generic question on longevity of modern automotive engines at high load

On a couple of rental trucks I have used, the governor was set to 55mph The truck would accelerate like a scalded cat to 50 then struggle for the last 5mph.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Since we seem to have derailed this thread into a general discussion on cars (and I'm the original poster), I'd like to take this opportunity to ask another (completely irrelevant) question.

I just skidded into a kerb with my car. Right front tyre hit pavement while steering was at full left lock to try and counter the skid. Forward speed at impact was well under 30km/h.

Car is now pulling slightly to the right. Needs 15 degrees of left steering input to go straight. Steering wheel returns to perfectly horizontal position when released with car moving.

Hit tyre is holding pressure fine (and is within 0.5psi of left one). Rim is scratched but not bent. Control rod looks visually straight, same as one on other side (didn't check wishbones). Acceleration and braking don't affect the pull. Wheel balance is subjectively fine (no vibration) at up to 60km/h (didn't risk going faster).

Can you experienced gentlemen please provide some suggestions? Would a simple wheel alignment likely work?

RE: Generic question on longevity of modern automotive engines at high load

A "simple wheel alignment" will point you in the direction of the problem, you most likely bent something.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

Quote (berkshire)

On a couple of rental trucks I have used, the governor was set to 55mph The truck would accelerate like a scalded cat to 50 then struggle for the last 5mph.
Well, in that case, I would include in my kit a device for calibrating the computer settings (no rocket science these days), and move the road speed governor out of the way! wink

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: Generic question on longevity of modern automotive engines at high load

(OP)

Quote (berkshire)

will point you in the direction of the problem, you most likely bent something

How unfortunate. So a wheel alignment shop won't be able to bend things to cancel out the problem?

RE: Generic question on longevity of modern automotive engines at high load

I am afraid that at this point you just have to go find out.
B.E.

You are judged not by what you know, but by what you can do.

RE: Generic question on longevity of modern automotive engines at high load

Quote (LMF5000)

So a wheel alignment shop won't be able to bend things to cancel out the problem?

Sounds like you bent the steering arm on the right side knuckle just a little (BTDT, left side).

If that is in fact the case, it'll be easier and far better to get it replaced rather than trust straightening it out, and I doubt that a repair/alignment shop would accept liability for straightening it anyway.


Norm

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Took it to a wheel shop for inspection. Bottom right wishbone is bent inwards - the paint has chipped off in the center of the wishbone where the kink is worst. Steering link seems OK but steering is very slightly harder to turn than usual. Car has all-electric power steering system, no hydraulics.

The right wheel is also about 1cm closer to the back of the car than the left wheel is (i.e. can only fit 4 fingers between tyre and mudguard on RHS compared to 5 fingers space on LHS).

This car has a basic MacPherson strut suspension - single shock absorber on top, control arm (wishbone) on bottom. Like so:

I will be un-bending or replacing the wishbone and doing an alignment afterwards. Could something else be bent as well, besides the wishbone, to be causing the lateral displacement of the wheel towards the back?

RE: Generic question on longevity of modern automotive engines at high load

"Could something else be bent as well?"

After the shop did their inspection did they mention suspicions of damage beyond the control arm?
How sure are you (how sure >>can<< you be ?) that the wheel was not displaced prior to whacking the curb?

Was the skid on dry road, wet road, gravelly road, snowy road, or icy road?
On snowy surfaces I practice quickly winding/unwinding steering lock when the front wheels skid. Each time we pass from straight thru maximum traction to skidding it pulls the front end a little bit more. My daughters yell when I drive like that on snowy days, but then each of them have driven straight into poles and trees, and I have not. yet.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Tmoose: I was there under the car while the shop was doing the inspection. Going back on Monday for a more detailed look. He said I was lucky it was the wishbone that's bent. Didn't mention any other damage. I'm pretty sure everything was straight before as the car only has 7000 miles (bought it "used" - it was an ex showroom test drive vehicle).

Skid was on glassy tarmac on wet road (wet from dew, it was 1am). Don't think you have the stuff overseas, but here in Malta some roads are coated with this cheap shiny high-glass tarmac with very poor grip. To make matters worse this was a sharp hairpin bend up a 30-degree incline and the road was barely two lanes wide between kerbs. Course there were no road lights so in the darkness I didn't realise how far I was far from the apex, went to take the turn a little faster than I should have (well, at least I know that now...) and steering lost all self-aligning resistance - i.e. the front wheels lost all grip. No tyre skidding noise either. I instinctively applied full lock to the left and pressed the brake but there was not enough space to my right and the rim banged into the kerb. Then the car bounced left and the tyres regained traction, so now it was heading straight into the wall on the left, but I managed to correct that in time and get it straightened.

I've never driven in snow. I suppose the grip level would be similarly poor (considering I'm using summer tyres). Funny thing is I had taken this car to a small race track in Sicily and had no trouble going round every bend with tyres screeching (correcting the understeer with extra steering input). It's FWD so has a natural tendency to understeer when the grip limit is exceeded but it's very neutral and easy to control. It also has traction control, torque vectoring and the other modern driver aids, but since it was in "dynamic" mode (aka sport mode) at the time they were not operating as agressively as in "normal" or "all weather" mode.

RE: Generic question on longevity of modern automotive engines at high load

(OP)
Well, got the car back from the repair shop today. Replaced the lower wishbone (€68, shipped all the way from Latvia!) and had an alignment done (€70, including wishbone fitting). Car now drives straight with hands off and steering feels symmetrical. Only odd thing is that the steering seems to need more effort to turn than I remember. I have the alignment sheet and seems the shop used the databank values for the MiTo Sport (Quadrofolgio), whereas mine is a normal non-sport MiTo.

The left wheel was not impacted, so using this wheel's values before and after the alignment, I can see what they've changed:
Half-toe increased from -40' to -5'
Camber reduced from -17' to -34'
Caster reduced slightly from +2*56' to +2*40'

Would any of these account for the increased steering effort? Power steering motor is fine because steering is very light when parking, it's only with speed that it stiffens up.

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