rough fwkw to rwkw conversion for 4wd

[Hof]

Hi,

For a landcruiser or patrol size 4wd, what would you say is a good fwkw to rwkw estimate for manual??

I was told a car is approx 75% less for manual and 70% for auto..

Cheers,

Hof

[PGS 4WD]

You mean thre rear wheel kW to be 75% of the engine power? We've been playing on our dyno a lot with various tyres and speeds, ie; gears.
The problems are many in this calculation, we've found that the larger nobby tyres at higher speeds take significantly more power to drive. I've discussed this with the builder of the dyno who agrees as his experience with race cars on slicks and treaded tyres does significantly change the rear wheel power. This is due to the air friction or turbulance around a nobbly tyre that becomes greater with speed.
A couple of recent examples were of a constant 4wd vehicle dynoed on old 35 11 1/2 simexes and then again 4 days later on new (the same tyre) lost approximately 20 kW over 4 tyres, there was no discernable difference in the behaiviour on the road at regular speeds.
Another of a rear wheel drive vehicle that made 114 kW in 3rd 1:1 and 129 in 2nd, under normal circumstances the gear is irrelevant to power as for what you loose in speed you make up in torque and the resultant power is the same. Torque * Speed(rpm) = power. Also noticed was that in 1:1 at higher speed the power appeared to drop 1000 rpm earlier, this is due to the increase in power being less than the increase of power lost to turbulance at the wheels at higher wheel speeds.
So if you want a big figure run small bald tyres at the lowest speed at which traction to the roller is assured.
Bear in mind manufactures are sneaky with their power figures, BHP is a constant not a ramped figure that will be higher, they get their figues on engine dynos with no accessories being driven, no alternator, power steer, fan, water pump. Some have remove oiling, scavenged exhaust and scavenged crankcases that all lead to significant increases in power.

Joel

[KiwiBacon]

Does it matter?

RWkW is the only one that actually means anything.

[Hof]

Yes, I do mean rwkw is 75% of the fwkw, as a rough estimate..

Im not after an exact figure like 73.2899%, I just thought someone might have some experience with a large 4wd and be able to give an ESTIMATE of a realistic figure..

As I said, for the majority of car applications it is accepted that you can estimate 75% for manual and 70% for auto, just wondering how far a 4wd would vary from this??

Thanks

[KiwiBacon]

Bear in mind manufactures are sneaky with their power figures, BHP is a constant not a ramped figure that will be higher, they get their figues on engine dynos with no accessories being driven, no alternator, power steer, fan, water pump. Some have remove oiling, scavenged exhaust and scavenged crankcases that all lead to significant increases in power.

Joel

True for automotive engines. But the truck and industrial engines have a much more real power rating. Bolting an engine up to a generator will show up the BS really quickly.

[PGS 4WD]

The point of all my waffle is that there is no estimate, somewhere between 10 and 50%. My dyno does do a calculation that requires a number of decellerations from 80 klms/h with the engine rpm signal connected to the dyno, it calculates and extrapolates the losses from the tyres and drive train from the data it gathers I have seen engines go from an engine dyno to the same chassis dyno with remarkably similar results however manual transissions give more accurate results than autos and the tyres are a bigger factor with 4wd than cars due to their surface and O.D.
Not to mention some dynos out thier dont comply with any recent standard for accuracy (the Mainline and Dynamic Test Systems do) and many still ollow the operator to enter correction data and/or edit print outs.
Joel

[Zac Zec]

do you have a estimate on power loss in a gq patrol. Would be interesting. I suppose what is the loss on a factory gq from engine hp to rwhp, then percentage differences when increasing tyre size on the same truck (31,33,35,37) and same type of tyre

Cheers

[PGS 4WD]

The most consitsant results are from stock vehicles GQ carby between 70 and 80 rwkW, a stock TD42 turbo Diesel 60 to 65 rwkW, 100 series 1Hz non-turbo 50 to 55 rwkW. Non turbo TD42 47 to 52 ish rwkW.
These sorts of figures I see most often on stock vehicles.

Joel

[madrolla68]

The most consitsant results are from stock vehicles GQ carby between 70 and 80 rwkW, a stock TD42 turbo Diesel 60 to 65 rwkW, 100 series 1Hz non-turbo 50 to 55 rwkW. Non turbo TD42 47 to 52 ish rwkW.
These sorts of figures I see most often on stock vehicles.

Joel

Joel

Finally someone that understands real world figures that include changing power loss figures due to tyre sizes gear oils etc.

We use a similair system to you that measures power losses or drag on driveline on the run down after the dyno run and we are getting very similair results to you indeed.

This brings me to people that will consistently argue with me about the 25-30% rule on power loss, it is absolute BS. Meaning that if you find ten extra Kw at the engine after a mod then you will get those same 10Kw at the wheels.

Anyway your figures are spot on.

[madrolla68]

do you have a estimate on power loss in a gq patrol. Would be interesting. I suppose what is the loss on a factory gq from engine hp to rwhp, then percentage differences when increasing tyre size on the same truck (31,33,35,37) and same type of tyre

Cheers

Hi , i have a GQ wagon fitted with 33" Bridgstone A/T 's 694 tread pattern and get around 30Kw loss.

i dynoed a constant four wheel drive 80 series landy today before a turbo fit and it had nobbly coopers on it and it had 53Kw loss, and wasn't that a joy to drive ,no wonder they wanted a turbo fitted.

[Zac Zec]

The most consitsant results are from stock vehicles GQ carby between 70 and 80 rwkW, a stock TD42 turbo Diesel 60 to 65 rwkW, 100 series 1Hz non-turbo 50 to 55 rwkW. Non turbo TD42 47 to 52 ish rwkW.
These sorts of figures I see most often on stock vehicles.

Joel

Joel

Finally someone that understands real world figures that include changing power loss figures due to tyre sizes gear oils etc.

We use a similair system to you that measures power losses or drag on driveline on the run down after the dyno run and we are getting very similair results to you indeed.

This brings me to people that will consistently argue with me about the 25-30% rule on power loss, it is absolute BS. Meaning that if you find ten extra Kw at the engine after a mod then you will get those same 10Kw at the wheels.

Anyway your figures are spot on.[/quote

So on a tb42 thats 60% loss? Far out!
What sort of engine power are you typically getting out of a stock motor turbo tb42 running 14.7 psi

Cheers

Zac

[PGS 4WD]

About all you will get out of a std pump on a TD42 is about 95rwKw, more boost won't help make more power without fuel, it can help to lower the exhaust temps though provided the turbo is suitably large enough to deliver the boost with reasonably cool outlet temperatures, at that the pump is maxed out and the idle speed may be hard to slow down, also expect a fair bit of smoke off boost.

I also have a petrol 80 constant 4wd, I squeezed 68kW at 4 wheels with 98 fuel, optimized timing, adjusted air flow meter (pre 95) and extractors.

Your TD 42 may loose something like 8 kW to a water pump, 10 to an oil pump, 6 to power steering pump, 8 kW to a gear box 6 kW to a differential, 10 kW driving tyres, 2 kW to unis and tailshafts and so on untill your 100 kW engine makes 50 kW at the wheels, bearing in mind the losses aren't constant, a water pump will create more load at higher rpm until it cavitates and the load may drop, tyres disturb more air at higher speeds and therefore the losses are greater at higher tyre speeds, crankshaft windage increases with rpm and so on.

Joel

[1MadEngineer]

About all you will get out of a std pump on a TD42 is about 95rwKw, more boost won't help make more power without fuel, it can help to lower the exhaust temps though provided the turbo is suitably large enough to deliver the boost with reasonably cool outlet temperatures, at that the pump is maxed out and the idle speed may be hard to slow down, also expect a fair bit of smoke off boost.

I also have a petrol 80 constant 4wd, I squeezed 68kW at 4 wheels with 98 fuel, optimized timing, adjusted air flow meter (pre 95) and extractors.

Your TD 42 may loose something like 8 kW to a water pump, 10 to an oil pump, 6 to power steering pump, 8 kW to a gear box 6 kW to a differential, 10 kW driving tyres, 2 kW to unis and tailshafts and so on untill your 100 kW engine makes 50 kW at the wheels, bearing in mind the losses aren't constant, a water pump will create more load at higher rpm until it cavitates and the load may drop, tyres disturb more air at higher speeds and therefore the losses are greater at higher tyre speeds, crankshaft windage increases with rpm and so on.

Joel

wow they have BIG oil and power steer pumps on those!!!
OIL pump - 10kw at 100psi = 660cc oil pump HOLY COW it would weigh more than the engine!!!
6kw - power steer @ 1000psi = 36cc how do i get one of those, most pumps are ~5cc

the rest of the info is pretty good though.

[madrolla68]

About all you will get out of a std pump on a TD42 is about 95rwKw, more boost won't help make more power without fuel, it can help to lower the exhaust temps though provided the turbo is suitably large enough to deliver the boost with reasonably cool outlet temperatures, at that the pump is maxed out and the idle speed may be hard to slow down, also expect a fair bit of smoke off boost.

I also have a petrol 80 constant 4wd, I squeezed 68kW at 4 wheels with 98 fuel, optimized timing, adjusted air flow meter (pre 95) and extractors.

Your TD 42 may loose something like 8 kW to a water pump, 10 to an oil pump, 6 to power steering pump, 8 kW to a gear box 6 kW to a differential, 10 kW driving tyres, 2 kW to unis and tailshafts and so on untill your 100 kW engine makes 50 kW at the wheels, bearing in mind the losses aren't constant, a water pump will create more load at higher rpm until it cavitates and the load may drop, tyres disturb more air at higher speeds and therefore the losses are greater at higher tyre speeds, crankshaft windage increases with rpm and so on.

Joel

wow they have BIG oil and power steer pumps on those!!!
OIL pump - 10kw at 100psi = 660cc oil pump HOLY COW it would weigh more than the engine!!!
6kw - power steer @ 1000psi = 36cc how do i get one of those, most pumps are ~5cc

the rest of the info is pretty good though.

Maybe it should have read:

"For illustartion Purposes Only!!!!!!!"

[Shadow]

is Hof meaning

RWKW = Rear Wheel Killowatts and FWKW Fly Wheel Killowatts

or FWKW = front wheel killowatts??

[Zac Zec]

The most consitsant results are from stock vehicles GQ carby between 70 and 80 rwkW, a stock TD42 turbo Diesel 60 to 65 rwkW, 100 series 1Hz non-turbo 50 to 55 rwkW. Non turbo TD42 47 to 52 ish rwkW.
These sorts of figures I see most often on stock vehicles.

Joel

Joel

Finally someone that understands real world figures that include changing power loss figures due to tyre sizes gear oils etc.

We use a similair system to you that measures power losses or drag on driveline on the run down after the dyno run and we are getting very similair results to you indeed.

This brings me to people that will consistently argue with me about the 25-30% rule on power loss, it is absolute BS. Meaning that if you find ten extra Kw at the engine after a mod then you will get those same 10Kw at the wheels.

Anyway your figures are spot on.

Hey where is your shop and dyno?

Cheers

Zac

[Hof]

is Hof meaning

RWKW = Rear Wheel Killowatts and FWKW Fly Wheel Killowatts

or FWKW = front wheel killowatts??

Well I did say Land Cruiser or Patrol, so front wheel Kilowatts would be a bit stupid

[PGS 4WD]

Im in melbourne.

Yes the figures I were giving were for example, and in reality we didn't add many other factors, cooling fans ect, my point being the frictional losses are huge.

Interestingly enough if you have ever primed a new engine with a drill you will find that a quality battery drill will come to nearly a complete stall when oil pressure is acheived, a drill may be good for 2-3 Hp and thats at slow speed not the 3-6000 rpm the pump may be spinning at at peak power. I've seen the teeth on holden oil pump drives shear and the oil pump drives in Clevo's and Windsor Ford engines twist and break when high volume oil pumps are used, these losses are bigger than you might think and its why newer cars are built around lighter drivetrains and use lighter oils and lighter valve springs, short skirt pistons and so on, the frictional losses are huge. Anything that gets hot during use is turning power to heat and not going to be measured in full at the wheels, energy is not created or lost it just changes state.

A clutch fan that engages and disengages on the dyno will see a power change of about 5 kW at the wheels. Don't forget tensioners, belts, unis, axle bearings, pinion bearings, ever tried to turn a large diff by hand at the pinion? now try turning it at 3000 rpm.

Joel

[madrolla68]

The most consitsant results are from stock vehicles GQ carby between 70 and 80 rwkW, a stock TD42 turbo Diesel 60 to 65 rwkW, 100 series 1Hz non-turbo 50 to 55 rwkW. Non turbo TD42 47 to 52 ish rwkW.
These sorts of figures I see most often on stock vehicles.

Joel

Joel

Finally someone that understands real world figures that include changing power loss figures due to tyre sizes gear oils etc.

We use a similair system to you that measures power losses or drag on driveline on the run down after the dyno run and we are getting very similair results to you indeed.

This brings me to people that will consistently argue with me about the 25-30% rule on power loss, it is absolute BS. Meaning that if you find ten extra Kw at the engine after a mod then you will get those same 10Kw at the wheels.

Anyway your figures are spot on.

Hey where is your shop and dyno?

Cheers

Zac

United Fuel Injection
479 Great Eastern Highway Redcliffe

Ask for matt .

[Shadow]

is Hof meaning

RWKW = Rear Wheel Killowatts and FWKW Fly Wheel Killowatts

or FWKW = front wheel killowatts??

Well I did say Land Cruiser or Patrol, so front wheel Kilowatts would be a bit stupid

why? cruiser has something like 70/30 torque split from rear to front. Its done by having a bigger side gear on the centre diff for the rear tailshaft.

dunno about patrols.

[nzdarin]

So 216rwkw on 35x11.5 Simex is pretty good then!
With the figures supplied a TD42 GQ loses about 45%.
Using that loss would mean my motor was producing about 390kw at 55% on the injectors, and the injectors can only handle that HP at about 80%. So obviously the loses aren't liner as there is no way my motor was producing anywhere near that HP as it was running rich with retarded timing, and restricted to 5000rpm. (instead of 7300)
I wish we could use it as it would once tuned my motor would have about 545kw when the reality is more like 440kw.
BUT upon saying that using a 30% lose gave us about what we expected so I does that mean the loses are constant hp loses rathr than a % so the more hp the less % loss? That sort of explains the result we got with my truck 2 weeks ago?
ie driving a given drive train will take a certain amount of hp and the auxilaries on a motor will also take a certain hp so regaurdless of how much hp is created the loss will be the same in hp not %. So by increasing the power of an engine at an engine speed then most of that power will end up at the wheels.

[madrolla68]

So 216rwkw on 35x11.5 Simex is pretty good then!
With the figures supplied a TD42 GQ loses about 45%.
Using that loss would mean my motor was producing about 390kw at 55% on the injectors, and the injectors can only handle that HP at about 80%. So obviously the loses aren't liner as there is no way my motor was producing anywhere near that HP as it was running rich with retarded timing, and restricted to 5000rpm. (instead of 7300)
I wish we could use it as it would once tuned my motor would have about 545kw when the reality is more like 440kw.
BUT upon saying that using a 30% lose gave us about what we expected so I does that mean the loses are constant hp loses rathr than a % so the more hp the less % loss? That sort of explains the result we got with my truck 2 weeks ago?
ie driving a given drive train will take a certain amount of hp and the auxilaries on a motor will also take a certain hp so regaurdless of how much hp is created the loss will be the same in hp not %. So by increasing the power of an engine at an engine speed then most of that power will end up at the wheels.

Argh i think people are starting to get it!!!!!

The losses calculated are for non-modded factory spec vehicles.If you want to know how much power your engine is making put it on a dyno that measures it dont guess.The drivetrain losses(excluding tyres) WILL not change no matter how much power you are making.If you make an extra 50Kw over std then ALL of the extra 50Kw gets to the wheels not a percentage of it.

Now if you were running simexs then my guess is you would have lost around 55Kw they are power sucking mutha fuka's.Now your figure of 216RwKw from a TD42???, how modded is it????.I would hazard a guess that that is 216FwKw from my experience but hey im happy to be shown otherwise.

[PGS 4WD]

I heard of a 220 kW TD42 once, it lasted about 30 seconds on the dyno before splitting a bore.
I've seen 160 on 36 inch TSL's at 28 psi intercooled, modded pump and GT 30 roller turbo, new motor balanced and blueprinted.
The PGS Suzuki makes 276 rwkW with a VP motor striked to 4.3L turbo roller running 18psi on 37 inch X-terrains. Shame we keep breaking autos, we've got another to try soon.
I'd be keen to see anyone else who has big numbers in shootout mode on a Dyno Dynamics dyno to see what power they really make!

Joel

[Dozoor]

I may have missed it ,
But how much does the extra gear set absorb ?
and is there a significant difference between chian and gear driven cases on constant fwds ?

Also does anbody know if a ring and pinion set absorbs more power then a helical cut set , other words does transmiting the power through the
90 deg cost power ? strange question i supose

[madrolla68]

I heard of a 220 kW TD42 once, it lasted about 30 seconds on the dyno before splitting a bore.
I've seen 160 on 36 inch TSL's at 28 psi intercooled, modded pump and GT 30 roller turbo, new motor balanced and blueprinted.
The PGS Suzuki makes 276 rwkW with a VP motor striked to 4.3L turbo roller running 18psi on 37 inch X-terrains. Shame we keep breaking autos, we've got another to try soon.
I'd be keen to see anyone else who has big numbers in shootout mode on a Dyno Dynamics dyno to see what power they really make!

Joel

Joel ive seen a couple of full on race TD42's in gq cabbies that made 185Kw but with big power losses from simex's and other nobbly tyres.

Precombustion chamber engines struggle to make big power cause can only pump so much fuel through a pre-com.

Matt

[PGS 4WD]

That makes sense, I never saw those figures personally and don't know what tyres he was on, it was a guy over here from ATOC a 4x4 shop, I figured to split the bore there must be some funky cylider pressure though! We split a bore on a turbo 2.6 Astron in a Sigma at 230 rwkW (pertol of course)

A lot of shops over here wont dyno on 35 and 36's but I will on anything, our rollers are quite large, I did our 49's on our Tough truck car. I just do 3 pre runs, get the average run, do my tuning, and then again average 3 runs and print the two average runs.

Joel

[Zac Zec]

So from your experience you must have a fair idea of fly wheel horsepower for a turbo tb42e running 14.7psi stock motor

I have been having this discussion with a few mates about power loss and i was of the opinion that aside from tyre size it should be a constant providing no additional items have been bolted onto the engine.

Would this be correct?

Cheers

Zac

[madrolla68]

So from your experience you must have a fair idea of fly wheel horsepower for a turbo tb42e running 14.7psi stock motor

I have been having this discussion with a few mates about power loss and i was of the opinion that aside from tyre size it should be a constant providing no additional items have been bolted onto the engine.

Would this be correct?

Cheers

Zac

Yes this is correct, your power loss will remain constant if no other ancillary items have been added or removed.We dont do a lot of petrol cars as we are a diesel fuel injection shop but i will endeavour to find out for you.

If it is in a GQ ,five speed for example with road tread 31's the power loss would be around the 23Kw mark if all is in good order.

[cuthill]

deisel tec in lilydale have done a couple of 200 plus rwkw td42 with no problems. cars still going well 12 months on

[madrolla68]

deisel tec in lilydale have done a couple of 200 plus rwkw td42 with no problems. cars still going well 12 months on

Ok cool, good daily drivers ey??????