Question for the clever people

[Bulletproof]

To show you must change down and not just keep the foot down in a high gear, I will give you the facts about my hilux going up the spooners range out of Nelson

With 35inch tyres on I change into 4th at the start of the hill. I maintain 100kph at about 2800rpm for about 1k up the hill. By then the pyrometer has moved up to over 650 degrees so I start easeing off the accerator to maintain my 650 degrees until my revs drop back to 2400 and my speed is about 80 kph.
At this I am forced into 3rd gear and then I can maintain my 80 kph to the top with the pyrometer just over 600degrees at around 3000rpm

If I kept my foot foot down as some are recommending I would have cooked the motor because at all stage I have the power to accelerate

Richard

[KiwiBacon]

If I kept my foot foot down as some are recommending I would have cooked the motor because at all stage I have the power to accelerate

Richard

What's the hottest your EGT's have ever got?
I've run accidentally past 800 many times, keep sustained at or under 750 deg C. I haven't seen any damage resulting from this yet.
I have met people in the US who run close to 1000 deg C for short bursts and claim no problems but I'm not willing to do that to my engine.

[Bulletproof]

If I kept my foot foot down as some are recommending I would have cooked the motor because at all stage I have the power to accelerate

Richard

What's the hottest your EGT's have ever got?
I've run accidentally past 800 many times, keep sustained at or under 750 deg C. I haven't seen any damage resulting from this yet.
I have met people in the US who run close to 1000 deg C for short bursts and claim no problems but I'm not willing to do that to my engine.

I have gone close to 750 on an overtaking move but only for a short period
On a prolonged climb up the spooners I can't see the point in risking damage to the motor to save half a minute and a dollars worth of diesel

Thats only my opinion and I'm sticking to it.

Richard

[Steve_t647]

Be carefull with those US figures they may be farenheit 1000 deg F is about 550 deg Celcius

the us would need figures around 1500 deg Farenheit to match the 850 deg c figure, it also depends where you are measureing it pre or post turbo (if there is one) the temps are usualy measured at the manifold before a turbo as this is the area the temperatures can cause the most effect, further away the cooler the temp you will see.

as to whats safe well it is more the level of risk you want to take knowing the cost of a rebuild or engine swap.

[Henry]

In answering the fuel economy question, my last 2 company cars have had fuel useage meters. In both cases to use less fuel you leave it in the higher gear and let the engine labour. If you want more power change down. That is my experience watching the fuel meter. the latest car is a auto and it is programed to work that way.

[Bulletproof]

Be carefull with those US figures they may be farenheit 1000 deg F is about 550 deg Celcius

the us would need figures around 1500 deg Farenheit to match the 850 deg c figure, it also depends where you are measureing it pre or post turbo (if there is one) the temps are usualy measured at the manifold before a turbo as this is the area the temperatures can cause the most effect, further away the cooler the temp you will see.

as to whats safe well it is more the level of risk you want to take knowing the cost of a rebuild or engine swap.

The figures I am quoting are all celcius and measured in the collector of the extractors . I dont have a turbo.

And my motor has cost me $10,000 and I am not going to risk stuffing it.

Richard

[turoa]

my motor has cost me $10,000 and I am not going to risk stuffing it.

are you serious?

[nstg8a]

my motor has cost me $10,000 and I am not going to risk stuffing it.

are you serious?

wouldnt surprise me, mines had nearly 6k spent on it, and that was just a basic rebuild...

be pretty easy to spend 10k on a diesel.

[skid]

club member spent 8.5k on rebuilding a 13BT

[Bulletproof]

my motor has cost me $10,000 and I am not going to risk stuffing it.

are you serious?

Deadly serious
Near new motor done 9000ks cost $7850
supercharger setup 1000
intercooler fitted over 500
extractors fitted 400
modify fuel pump 250

total $10,000

Easy to spend money

Richard

[tweake]

To show you must change down and not just keep the foot down in a high gear, I will give you the facts about my hilux going up the spooners range out of Nelson

With 35inch tyres on I change into 4th at the start of the hill. I maintain 100kph at about 2800rpm for about 1k up the hill. By then the pyrometer has moved up to over 650 degrees so I start easeing off the accerator to maintain my 650 degrees until my revs drop back to 2400 and my speed is about 80 kph.
At this I am forced into 3rd gear and then I can maintain my 80 kph to the top with the pyrometer just over 600degrees at around 3000rpm

If I kept my foot foot down as some are recommending I would have cooked the motor because at all stage I have the power to accelerate

Richard

but yours is not a stock standard motor.

no manufacture in their right mind would make a vehicle that cooks when they go full throttle up a hill. if they did they would go broke fixing all the vehicles.

remember 99.9% of vehicles do not have pyro's fitted even counting the aftermarket ones. 99.9% of vehicles do not cook or go bang when they get to a hill.

what did i say before.......

its fine on your motor unless its a thrashed out piece of crap or its highly modded

[KiwiBacon]

Be carefull with those US figures they may be farenheit 1000 deg F is about 550 deg Celcius

the us would need figures around 1500 deg Farenheit to match the 850 deg c figure, it also depends where you are measureing it pre or post turbo (if there is one) the temps are usualy measured at the manifold before a turbo as this is the area the temperatures can cause the most effect, further away the cooler the temp you will see.

as to whats safe well it is more the level of risk you want to take knowing the cost of a rebuild or engine swap.

Those figures were converted, the pre-conversion figures were 1800F. This particular engine was used for streetlight racing against corvettes.

I'll put a pryo in my non-turbo work car one day, probably just before I turbo it. Many people are scared by "factory" EGT levels, even though engines at those levels rarely melt down and usually only with the help of a blocked air cleaner.

[KiwiBacon]

Deadly serious
Near new motor done 9000ks cost $7850
supercharger setup 1000
intercooler fitted over 500
extractors fitted 400
modify fuel pump 250

total $10,000

Easy to spend money

Richard

If you managed to melt down your engine, it wouldn't cost anywhere near that to fix it again.
New head, pistons, valves and clean up the bores.
Your supercharger, intercooler, fuel pump and extractors would all survive fine.

[Bulletproof]

To show you must change down and not just keep the foot down in a high gear, I will give you the facts about my hilux going up the spooners range out of Nelson

but yours is not a stock standard motor.

no manufacture in their right mind would make a vehicle that cooks when they go full throttle up a hill. if they did they would go broke fixing all the vehicles.

remember 99.9% of vehicles do not have pyro's fitted even counting the aftermarket ones. 99.9% of vehicles do not cook or go bang when they get to a hill.

what did i say before.......

its fine on your motor unless its a thrashed out piece of crap or its highly modded

I agree mine is not a standard motor.

Who does have a Std truck ?
If you have a look at landruisers and hiluxs they came out on 700-750x16s ? Who are running that size tyre now ?

Most people I know are on 33s 35s or even bigger so they are not Std trucks. There gearing is miles higher than Std and therefore the need to change down.

On the Spooners range with 32s on I can go right to the top at 100 kph with the pyro under 650 degrees celcius.

Why does every second Prado or surf have a cracked head ?

So to tell people not to change down is wrong and I still stick to the rule to change down once the revs drop back to the max torque rev of your motor.

Richard

[KiwiBacon]

Why does every second Prado or surf have a cracked head ?

Because Isuzu didn't make them.

[wjw]

Why does every second Prado or surf have a cracked head ?

Partly because most are jap imports and were either never serviced properly or spent 60% of their time idling in traffic, but retaining their normal service intervals. As the 1KZ for example have alloy heads, they degrade over time.

On my 1KZ I spent $500 reconditioning the turbo, then 2K replacing the head , then 5k replacing the motor with another 1KZ, only to be screwed by the guy who did it for me. So then spent 5K on a petrol donk, that if it dies I can replace the whole thing for less than $1000. Simple economics for me.

As for what's cheaper to run. I think the petrol, but then the diesel cost me almost 10K, plus 6 months in disputes tribunals, courts etc + 1.5 years without the truck.

IF I had to do the same thing all over again, I would still choose a 1KZ, but would do what bulletproof has done and fit every gauge under the sun and do as much as possible to "prevent" damage in the first place.

[KiwiBacon]

Why does every second Prado or surf have a cracked head ?

Partly because most are jap imports and were either never serviced properly or spent 60% of their time idling in traffic, but retaining their normal service intervals. As the 1KZ for example have alloy heads, they degrade over time.

It's a myth that metals degrade over time. Unless you're talking about corrosion.
Toyotas have a rep for head trouble, the V6's petrols aren't much better than their small diesels. My brother drives one of the last 1KZ's, we'll see if toyota managed to fix the problem. Five years out it looks promising.

When petrol and diesel are the same price at the pump and diesels still have to pay road tax, the running costs will be similar.

[wjw]

Sorry yes corrode would be a better word... two Toyota garages have told me the same thing

[lneil]

A major point with the economy question is that the modern engines with fully computer controlled fuelling/mixture/timing etc. are much more tolerant of the high gear-low RPM scenario. They prevent over-fuelling and maintain efficiency very well.

I have been taught since I was young (&that's a lot of years) to change down, use the revs and avoid labouring the engine. I no longer believe that that is necessarily correct, as over many, many trips checking instantaneous fuel consumption I have found the higher gear-lower RPM to be noticeably more fuel efficient. The obvious proviso is that if you are unable to maintain speed in a climb to the point where the engine falls right off the torque curve, you have held it too long before changing.

Many seemingly opposite points raised so far are valid. The condition and design of the engine, petrol or diesel, type of transmission, torque characteristics etc. will all have a bearing on the absolute best technique for your particular vehicle.

I guess my two cents worth is to not do anything to the extreme. i.e. don't cane the living sh*t out of it at redline and, equally, don't lug it down near idle RPM where you have little efficiency but massive internal stress (particularly bottom end).

Yet another interesting point is that the latest common-rail diesels can use a multiple sequence injection cycle, which can incorporate three seperate injections in one combustion cycle and avoid the high stresses associated with commencing full injection before TDC. This allows very low RPM operations, still with very good torque.

Also, modern fully lock-up auto's are not more fuel hungry than manuals at most highway travelling speeds, as the accepted extra fuel-burn comes from the torque-converter efficiency loss, in fact the slightly higher gearing of many autos makes them more economical than an equivalent manual model when operating on the open road.. Around town, however, the extra fuel consuption does become noticeable.

If you are serious about saving gas, then remember that driving style has a much greater impact on economy than almost anything else. Get very familiar with what works in your vehicle and drive as smoothly as possible. Of course you will intolerable to be around if you get that anal about the last tenth of a percent of economy!! Most of us are happy with burning a fraction more gas and enjoying our driving a heck of a lot more.

[KiwiBacon]

I have been taught since I was young (&that's a lot of years) to change down, use the revs and avoid labouring the engine. I no longer believe that that is necessarily correct, as over many, many trips checking instantaneous fuel consumption I have found the higher gear-lower RPM to be noticeably more fuel efficient.

I suspect this might have been necessary in the past to get decent lift from the engine. Back in the days where 100,000 miles was a long lived engine. Now if an engine won't do 300,000km it's a POS.

Also, modern fully lock-up auto's are not more fuel hungry than manuals at most highway travelling speeds, as the accepted extra fuel-burn comes from the torque-converter efficiency loss, in fact the slightly higher gearing of many autos makes them more economical than an equivalent manual model when operating on the open road.. Around town, however, the extra fuel consuption does become noticeable.

There's still a large gulf in efficiency between a locked up auto and a manual. The auto has a lot of extra internal drag relating to lubriction pumps and planetary gear sets. www.amayama.com has a whole range of japanese car specs, every comparison I've found between auto/manual in the same vehicle results in a fuel penalty of at least 1km/l in the japanese 10/15 fuel consumption cycle.

My shopping basket is the only automatic vehicle I own (it'll be manual as soon as I can find a wreck to donate the parts), I have spliced in an electric over-ride on the torque-converter lockup solenoid. This lets me lock the transmission up at any speed by flicking a switch.
Even on a long flat drive with the converter locked up the whole way (say dunedin to christchurch) I cannot get the same fuel consumption figures the manual vehicles get.

As you've said, when the torque converter isn't locked up, the auto transmission is like a leaking fuel tank.

[Bulletproof]

35 years ago I used to be with Leyland and AEC trucks. Most of their motors had a compression ratio of 16 to 1 and the motors had very long strokes with direct injection. The max rpm was 2200 , but they were governed back to 1800 rpm as a motor with a long stoke cant handle high revs. These motors would work all day at 1000rpm and enjoy it.

Today's motors have a red line close to 5000 rpm . To achieve this the stroke has shortened up and in some cases the motors are over square meaning the bore is bigger than the stroke.
At the same time the compressions are now up to 22.5 to 1 . The max torque is developed at around 2400rpm as in the case of the toyota KZ and 3L ,5L as seen in hiluxs and prados.

These motors are not designed for slogging low revs . In between these two examples we have all the other diesel engines so no one can really give blanket advice when it comes to when to change up or down.

Thats why the max torque rev is the safest advice to give as to when to change down because in the case of the leyland trucks it is very low, where with a hilux a person should change down at 2400rpm

Cheers Richard

[KiwiBacon]

35 years ago I used to be with Leyland and AEC trucks. Most of their motors had a compression ratio of 16 to 1 and the motors had very long strokes with direct injection. The max rpm was 2200 , but they were governed back to 1800 rpm as a motor with a long stoke cant handle high revs. These motors would work all day at 1000rpm and enjoy it.

Today's motors have a red line close to 5000 rpm . To achieve this the stroke has shortened up and in some cases the motors are over square meaning the bore is bigger than the stroke.
At the same time the compressions are now up to 22.5 to 1 . The max torque is developed at around 2400rpm as in the case of the toyota KZ and 3L ,5L as seen in hiluxs and prados.

These motors are not designed for slogging low revs . In between these two examples we have all the other diesel engines so no one can really give blanket advice when it comes to when to change up or down.

Thats why the max torque rev is the safest advice to give as to when to change down because in the case of the leyland trucks it is very low, where with a hilux a person should change down at 2400rpm

Cheers Richard

You're comparing a large truck engine to a small ute engine.
Interestingly I've never seen a direct injection engine with a compression ratio much higher than 18. The 22.5:1 is the domain of indirect injection engines which were never factory turbocharged. The turbocharged 1KZ-TE's were dropped slightly to around 21:1.
http://www.toyotasurf.asn.au/techsite/d ... specs2.pdf

I've never seen specs for a diesel with stroke smaller than bore, even the VW 1.9 which revs to almost 5k has a significantly longer stroke than bore (79/95mm). Can you provide us some specs for one?
But the biggest question of all, has anyone ever killed an engine from running it at low rpm. If so what was the damage and how was it traced back to lugging as the cause?

[Bulletproof]

You're comparing a large truck engine to a small ute engine.
Interestingly I've never seen a direct injection engine with a compression ratio much higher than 18. The 22.5:1 is the domain of indirect injection engines which were never factory turbocharged. The turbocharged 1KZ-TE's were dropped slightly to around 21:1.
http://www.toyotasurf.asn.au/techsite/d ... specs2.pdf

I've never seen specs for a diesel with stroke smaller than bore, even the VW 1.9 which revs to almost 5k has a significantly longer stroke than bore (79/95mm). Can you provide us some specs for one?
But the biggest question of all, has anyone ever killed an engine from running it at low rpm. If so what was the damage and how was it traced back to lugging as the cause?[/quote]

The only point i'm trying to make is there are so many different engines used that one rule does't apply to them all.

The B series cruisers 3B , 13B , 14B ,15B direct injection motors all tend to resemble truck motors as opposed to the Prado KZs and the Hilux indirection motors.
The 14B has counter balance shafts that handle lower revs better as well.

A 2400 cc hilux motor has a bore 92mm and a stroke 92 mm making it square.
A 5L 3000cc toyota motor has a bore of 99.5 mm and a stroke of 96 making it over square .

Cheers Richard

[tweake]

The only point i'm trying to make is there are so many different engines used that one rule does't apply to them all.

says it all

[KiwiBacon]

A 5L 3000cc toyota motor has a bore of 99.5 mm and a stroke of 96 making it over square .

Cheers Richard

Wow, what a freak.
I can't understand why toyota didn't just take the turbo off the 1KZ-TE.
Or why they didn't sell the 1KD engines here sooner, they've been in europe for years.

[NJV6]

Quality of fuel here aparently......

[KiwiBacon]

Quality of fuel here aparently......

I've heard that one, but I don't buy it. Mercedes and BMW were selling their commonrail diesels here before low sulphur was mandated.
I think they just automatically ship us the "third world" engines to save some $$.

[darinz]

Throw away the manual & get an auto..it will just do its own thing

and autos suck even more gas than manuals so thats a backwould step.

Crap!
A modern auto isn't going to use much more fuel than a manual. When you take into account lock up torque convertors, higher gearing the speed of gear change and therefore reduced lost momentum. The real world differences are not very much (but auto does use more). If you listen to guys doing outback touring in Oz then they are saying that auto's are more economical over those extreme distances.

As for the original question, it is quite easy. An engine has 2 inportant rpm ponts.. Peak torque and peak HP. You want to keep it between these points. Peak HP is going to use more fuel obviously so keeping the rpm down and load down will achieve this. Wide open throttle uses fuel, so part throttle is what you want to achieve. I don't have facts or figures to back it up but WOT and low revs will use more fuel that part throttle and high revs.

But as I've replied to something near the beginning of the thread this has probably been said already!!

[KiwiBacon]

[If you listen to guys doing outback touring in Oz then they are saying that auto's are more economical over those extreme distances.

Really? I have heard the exact opposite. Auto car and manual car that are almost identical on the same trip, manual uses far less fuel.
The only time an auto can use less fuel is when you've got a complete muppet driving the manual. It's surprising how often this is the case.

I posted up some BSFC maps earlier which show the points of minimum fuel consumption. They aren't between maximum power and maximum torque.

[lneil]

Dont forget, BSFC maps do not take into account factors outside the mechanical componentry of the vehicle.

A common myth is based on engine efficiency points, and is that the optimum consumption occurs around 80-90kmh in most vehicles. This is grossly incorrect as the aerodynamic drag at those speeds far outweighs the slight efficiency advantage. If you watch an instantaneous consumption meter you will realise that a low speed (around 40-55kmh) in top gear is dramatically more fuel efficient, but absolutely useless information as I've never yet met anyone who would want to travel long distances at that speed.

Last time I checked this in a small modern car, I got around 60mpg at 60kmh, and 47mpg at 100kmh.