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Old 4th March 2010, 22:39   #16
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Arrow method

I haven't had a car dyno'ed yet but from a few dyno videos I've noticed that sometimes a car is stuck in one single gear during the test while at other times the car is taken up through it's gears.

Any ideas why / what difference it makes?
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Old 5th March 2010, 09:02   #17
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Check this thread on how GTO's car was Dyno'ed(to check the actual BHP) http://www.team-bhp.com/forum/techni...true-test.html
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Old 5th March 2010, 19:43   #18
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Quote:
Originally Posted by Shan2nu View Post
Thats only for engines that haven't been maintained well. If you keep a check on the engine components and replace them when needed, it shouldn't lose out on power.

Shan2nu
I disagree, even if you change every part of the engine, you'll still never get the same power produced as a brand new engine. There are clearances that increase - connecting rod bearings, bore of the liners, cylinder heads. if you change everything except for the engine block, you'll still have issues with getting back the original bhp. That kind of wear and tear normally accrues to about 25-30% losses.
I remember this when I reconstructed and rebuilt the toyota 1.5L turbo for my esteem. It was an old engine, with major parts renewed - bearings, clutch plate, axles, piston rings, and even turbo, still - never quite the same as a brand new engine. You can, perhaps by changing everything, but that would be too expensive.

Quote:
Originally Posted by aah78 View Post
I haven't had a car dyno'ed yet but from a few dyno videos I've noticed that sometimes a car is stuck in one single gear during the test while at other times the car is taken up through it's gears.

Any ideas why / what difference it makes?
Probably could be test for that rpm and speed at the wheels. Especially done for turbo mods - changing the size of the turbo charger and things like that. Or even to test the transmission if there was any issue with it. reasons could be endless, but on the same lines.

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Originally Posted by salbin View Post
Most of the bigger engines undergo 100% dynamo meter test based on certain specified test cycles.
But some of the high volume production lines producing smaller engines does not test the with the dynamo meter. Instead they do the "Cold Test". Cold test is nothing but driving the engine using a prime mover and check certain aspects like leak, noise, temperature etc.
It is up to the manufacturer to decide whether to go for cold test or hot teat.
In both the cases some engines are taken to the test beds at certain pre-determined frequency for a full cycle testing.
I doubt it, although I might be wrong. Only the parent engine undergoes all the tests for emissions, power, brake dyno test, the rest are just produced on the same lines and they do have to certify that the parts used are the same as the one used in the parent engine. Testing each engine would increase costs of the vehicles and is quite unneccessary if you have a proper QA.

BTW, I'm sure some of you would know this, but I witnessed a brake dynamometer test on a marine engine once, and it was conducted rather differently. the engine is used to drive a propeller, so they use a water brake for testing the bhp. The shaft is immersed in a huge tank with water...and the flow of water is used as the brake.
Brake horse power - the power used to stop (brake) and engine when it's running at it's optimum rating.
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Old 5th March 2010, 20:05   #19
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Quote:
I disagree, even if you change every part of the engine, you'll still never get the same power produced as a brand new engine. There are clearances that increase - connecting rod bearings, bore of the liners, cylinder heads. if you change everything except for the engine block, you'll still have issues with getting back the original bhp. That kind of wear and tear normally accrues to about 25-30% losses.
I remember this when I reconstructed and rebuilt the toyota 1.5L turbo for my esteem. It was an old engine, with major parts renewed - bearings, clutch plate, axles, piston rings, and even turbo, still - never quite the same as a brand new engine. You can, perhaps by changing everything, but that would be too expensive.
That can only mean that you didn't replace the parts that were causin the power loss.

GTO's ex-vtec (lol) was dynoed at 106whp after 8 years, 70,000 plus kms without any engine part replacement. Heck, he is still running the stock clutch.

If what you say is right, then the engine should atleast have shown some signs of power loss even with the filter and exhaust mods. Plus there was a 5.6% slipage loss prob from the clutch.

Rocam is running a TC B16 from the 80s which he has rebuilt and tuned to produce 400whp.

How much power you get from a rebuilt engine also depends on the quality of the build. If you give 10 old engines to 10 diff rebuilders, you see a vast diff in the power output depending on their experience, skill and quality of work.

Shan2nu

Last edited by Shan2nu : 5th March 2010 at 20:07.
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Old 5th March 2010, 20:29   #20
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First of all - 70,000kms is not old.
The engine I bought was second hand with atleast 200,000kms on the clock and I used Maruti Parts which do have higher losses as compared to those manufactured by honda.

How much did the rebuilding and retuning cost? I did say it was possible, just that it would be too expensive.

I agree on the rebuild quality and moreover on the original builder of the engine...you just can't do this kind of remodding with every engine on the market.
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Old 5th March 2010, 20:47   #21
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Quote:
First of all - 70,000kms is not old.
Old enough to show some signs of power loss at the rate you're takin about. If you say an old engine (lets take your 2,00,000km example) shows around 25-30% loss in power even after rebuilding the major parts except the engine block, this engine should be losing atleast 40-50% of its power without a rebuild.

So 50%@2,00,000 kms without part replacement equates to 17.5% power loss@70,000kms.

Shan2nu
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Old 6th March 2010, 00:13   #22
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although your calculations are accurate, you can't really compare two different engines in such a straightforward method, not in the practical sense and not when the past history in one of them is unknown.
Added to the fact that one is a diesel and the other a petrol engine, both with tremendous differences in operating parameters and with the known fact that diesel engines are normally subjected to higher stresses than petrol.

Now take this friend's car - 7-8yrs old - and singly owned, therefore properly cared for - you can't expect that much of a drop at 70,000 kms. My present car is 4 years old and already crossed 90K and since I've taken care of it, I know that it hasn't been abused, therefore I know it's a young engine.

But, w.r.t to the second hand engine I bought, I don't really know how much it was abused before being sold. I did get it cheap though and the entire conversion cost me under 2 lakhs. So, I guess that would mitigate some of the stuff I said.

Last edited by Otto : 6th March 2010 at 00:16.
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Old 6th March 2010, 00:50   #23
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Quote:
although your calculations are accurate, you can't really compare two different engines in such a straightforward method, not in the practical sense and not when the past history in one of them is unknown.
That was exactly my point. A well maintained engine with the required parts replaced on time, will be able to maintain its power over the years.

In your case, the power output maynot have been satisfactory due to other reasons.

Shan2nu
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Old 6th March 2010, 11:20   #24
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you still haven't gotten the points I made

1. You can't compare performances with petrols and diesels so plainly and
2. Engine wear is not linear it's exponential - therefore an engine at 100,000kms does NOT perform 50% better than one at 200,000kms. This is because as the engine ages, other parts begin to end their life, thus increasing costs inorder to maintain those figures.

I was giving you the demonstration of a car used for 8 years with 70,000kms compared to one used for half that time in the for the same mileage because I was proving the point that the car had hardly been driven, and therefore 70,000kms was new!
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Old 6th March 2010, 12:56   #25
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Quote:
you still haven't gotten the points I made

1. You can't compare performances with petrols and diesels so plainly and
2. Engine wear is not linear it's exponential - therefore an engine at 100,000kms does NOT perform 50% better than one at 200,000kms. This is because as the engine ages, other parts begin to end their life, thus increasing costs inorder to maintain those figures.

I was giving you the demonstration of a car used for 8 years with 70,000kms compared to one used for half that time in the for the same mileage because I was proving the point that the car had hardly been driven, and therefore 70,000kms was new!
So to even say that an old engine will lose 25-30% of its original power (inspite of having all the major parts replaced) is just your personal estimate based on what you experienced with your build. This does not mean that all engines that have done 2,00,000kms will show such loss in power and this is what i was trying to say.

2ndly, you cannot judge an engines life just based on how many kms it has clocked. An abused engine with 70,000kms will show much more wear and tear as compared to a well maintained engine with equal mileage.

An engines life is not decided by how many miles it has done but rather how it has done those miles. So 70,000kms is long enough to do a great deal of damage on an abused engine.

And my calculation of 17.5% wear at 70,000 was just to show you that you cannont calculate wear and tear with numbers. It never works out. So the kind of power loss you're talking about is impossible on a well maintained engine, especially when the worn out/damaged parts have been replaced.

You were just unlucky with your engine rebuild.

Shan2nu

Last edited by Shan2nu : 6th March 2010 at 12:58.
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Old 6th March 2010, 15:07   #26
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In answer to the original question, and if Wikipedia is your friend, then have a look at Horsepower - Wikipedia, the free encyclopedia :

SAE net crankshaft horsepower


In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net hp testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.

SAE certified crankshaft horsepower


In 2005, the SAE introduced a new test protocol for engine horsepower and torque.[12] The new protocol eliminates some of the flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as SAE-certified.
A few manufacturers such as Honda and Toyota switched to the new ratings immediately, with multi-directional results; the rated output of Cadillac's supercharged Northstar V8 jumped from 440 hp (330 kW) to 469 hp (350 kW) under the new tests, while the rating for Toyota's Camry 3.0 L 1MZ-FE V6 fell from 210 hp (160 kW) to 190 horsepower (140 kW). The ES330 and Camry SE V6 were previously rated at 225 hp but the ES330 dropped to 218 hp while the Camry declined to 210 hp. The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette Z06. Certified power rose slightly from 500 hp (370 kW) to 505 hp (377 kW).

DIN horsepower


DIN horsepower is the power measurement protocol in the German DIN standard 70020. Because the German word for horsepower is Pferdestärke, in Germany it is commonly abbreviated to PS. DIN hp is measured at the engine's output shaft, and is usually expressed in metric (Pferdestärke) rather than mechanical horsepower.

ECE hp


ECE R24 is the European standard for measuring engine output.[13] It is quite similar to the DIN 70020 standard, but with different requirements for connecting an engine's fan during testing. ECE is seen[who?] as slightly more liberal than DIN, and ECE figures tend to be slightly higher than DIN.[citation needed]

Citation 12 above is Certified Power - SAE J1349 Certified Power SAE International

Citation 13 above is http://www.unece.org/trans/main/wp29...gs/r024r2e.pdf
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Old 6th March 2010, 21:05   #27
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Quote:
Originally Posted by Shan2nu View Post
So to even say that an old engine will lose 25-30% of its original power (inspite of having all the major parts replaced) is just your personal estimate based on what you experienced with your build. This does not mean that all engines that have done 2,00,000kms will show such loss in power and this is what i was trying to say.
Not alone mine, or maybe I'm unlucky that way, but I've seen it with so many cars undergoing rebuilds and the minimum power loss we ever got was 10%, and oh, that actually was a petrol engine (some relation here?)

Quote:
2ndly, you cannot judge an engines life just based on how many kms it has clocked. An abused engine with 70,000kms will show much more wear and tear as compared to a well maintained engine with equal mileage.

An engines life is not decided by how many miles it has done but rather how it has done those miles. So 70,000kms is long enough to do a great deal of damage on an abused engine.
Absolutely agreed, however this point would be completely moot in the case of a single owned car that has been kept for so long.

Quote:
And my calculation of 17.5% wear at 70,000 was just to show you that you cannont calculate wear and tear with numbers. It never works out. So the kind of power loss you're talking about is impossible on a well maintained engine, especially when the worn out/damaged parts have been replaced.


You were just unlucky with your engine rebuild.

Shan2nu
Agreed, though to a certain extent - some engines just have a shorter life. Take e.g. tata engines (no disrespect, because they DO come cheap). Those engines need to be scrapped by the time you reach 200,000kms.
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Old 6th March 2010, 21:35   #28
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Quote:
Originally Posted by Shan2nu View Post
Rocam is running a TC B16 from the 80s which he has rebuilt and tuned to produce 400whp.
How much of the engine is actually in a stock condition? And how many of the parts inside the engine have been replaced with forged aftermarket stuff?
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Old 6th March 2012, 11:19   #29
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Default Computing h.p.

tbhp gurus. I'm trying the find out the HP for an SX4 VXi. Google tells me that:

1 HP = 2pi(T)(RPM)/33,000

One site tells that:

HP = (T X RPM) / 5252

According the MUL website: T = 145 Nm @ 4100 RPM

So is '113.194973343 hp' the correct answer?

Your corrections/suggestions/thoughts most welcome.
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Old 7th March 2012, 22:11   #30
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Quote:
Originally Posted by jn-3-16 View Post
So is '113.194973343 hp' the correct answer?
No.
Check whether the formula you have used is valid for the units you have used!

Regards
Sutripta
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