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castellan Offline
#21 Posted : Saturday, 15 December 2018 2:33:05 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
I didn’t make this up, it is a well known and tested formula. It is a function involving only 3 variables: weight, hp and mph. Nothing to do with torque except that torque and hp are inter-related.


I did not say that you did, I know the concept well.

Torque is torque and HP is HP but there is a relation ship and that's what the revs will tell you, it's a working in such progressive when one looks at such a chart, then one can understand it better.
castellan Offline
#22 Posted : Saturday, 15 December 2018 2:40:50 PM(UTC)
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Originally Posted by: wbute Go to Quoted Post
I am not sure on this theory. You can determine some things like water flow through a hose in this way, because the variables of things like friction loss are known and pump efficiency etc are constant.
Trying to work out power figures from trap speed and weight is way to inaccurate. You have no idea of power train loss or atmospheric conditions etc. You will come up with a figure, but it won’t be correct. They could have had a headwind or tailwind or no wind etc. The torquier engine would have performed better in some conditions.


It comes down to this the max HP is only one factor of a engines power.

One could build a 308 and both produce 330hp max but they could be totally different to drive, lets say that one has a short peek max and one has a wide peek and good all round to drive and the other a pig to drive gutless down low and lacking all over below and over the max HP.
abi Offline
#23 Posted : Saturday, 15 December 2018 11:05:56 PM(UTC)
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What Terry and HK are saying is bang on true, the drag racers have been using this very accurate formula for decades. Google 'Moroso horsepower' and you will see trap speed and weight have been used since the 1960's to calculate engine output and is spooky accurate.
Another old saying - tune for trap speed and tyre and gear for ET.
castellan Offline
#24 Posted : Sunday, 16 December 2018 10:58:22 AM(UTC)
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It's as easy as working out HP it's self.

But not the full picture.

Factory HP figures ? well there are a lot of ways they arrive at such and I would say that to be accurate, such would need all hooked up like exhaust etc.
Look at a VB Commodore that has a realistic DIN figures that no one could deny, so a V8 4.2L Single or Dual exhaust points to the reality's and then you go Auto or 4speed manual and then look at the diff ratio and that will give one an idea of what to expect. but the other way like a HT-G-Q-J-X-Z is a joke as the one looking at the info is under delusions, as he may think why go to the Dual exhaust option ? because he does not understand that going to a Dual exhaust will gain him performance and I have come across this type many a time, they think that the Dual exhaust will only make more noise, they are convinced of this ! because they can not see the change in the brochure, so it does not exist to them. but with the DIN system in the VB Commodore they can not reject the facts within the Brochure.

One can look at the VZ Commodore figures that are even more accurate again, we can see with the 5.7L the difference between the SS and the other types with single exhaust or the Monaro has even more kw.

Even tho with the DIN figures I found this to be advertised wrong some how ? with the last of the VS V8 utes stating the 179kw figures of the VT V8 and their is no way that a crappy VS single exhaust ute could match the VT Dual exhaust with 2 cats, I would think it would be truly around 168kw at most. why do I believe such, well a VN to VS exhaust is the same crappy single system with 165kw but with their crappy Dual that they had with only one cat you get 180 to 185kw and not to mention a bit more of a tune job in that and running on 95 octane I believe and that's why they got the knock sensor for, and the fact of the matter is that the VT exhaust is better than they were as it has 2 cats. not to mention another thing them VT V8'S were designed to run on 95 octane to get them there figures, but you can run 91 octane in them and that's another story again that we can look at.
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#25 Posted : Sunday, 16 December 2018 12:01:39 PM(UTC)
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Factory figures are normally accurate but not always, as you well know sometimes engines were deliberately not properly rated. Good examples were L34 and the GT-HO engines, sure they may be telling a half truth but do not quote the maximum outputs of such engines. GM deliberately underrated the power figure of the 1969 LM1 engine, but left its torque alone. GMH rated it properly in the HT-HG 350 auto GTS. I am sure there is plenty of other examples in GM, Ford etc.

Which type of rating is better depends upon your perspective. To me DIN is a waste of time as I am not interested in comparing cars, just engines. I don't care if the engines is in a Nova or Corvette an El Camino or a Monaro - their ratings will be all be different for the same engine. Others want SAE net or SAE gross, either are as valid as each other a long as the test conditions are equal which is easy to do in a controlled environment engine dyno whether the engine be using for example a GM1 test, or a GM20 test or whatever the DIN test is called. Where net tests become frustrating though is it is hard to compare engines when sometimes they were auto only. When I was doing the 350 article for Eric Norton I found it particularly frustrating to try and find proper comparable power figures for the HQ era L48 engines. Many of the applications were auto, and in an auto DIN test they struggle to get revs out of an engine to show its full capability. Thus when trying to find the same US engine as we got in the early HQ's, I couldn't easily find the same engine as the DIN rating on auto engines were quoted at 4000 or 3400rpm for power and 2400 or 2000rpm for torque. The only way I could even link the two ratings together was the 1971 engines were rated at both SAE gross and net, so you had a comparison point where I could show the US 1971 ratings for our 1971 engine, then show what they became in subsequent years in the USA, even though GMH never changed its figures.

The ratings that still elude me are the HQ into HJ figures, I still do not understand what caused GMH to drop the power ratings of all the HQ/HJ engines other than the 308 which increased (as it was the only one that changed). One day I'll find the paperwork that spells it out. I suspect GMH were telling a few porkies with all of the HQ engines except for the 350, these were pretty much right as compared to the US engines.
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castellan Offline
#26 Posted : Sunday, 16 December 2018 1:29:17 PM(UTC)
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I know you are not interested in comparing cars and I understand where you are coming from.

You are looking for engines that are the same as to ID them as what is what, nothing wrong with that and I like to know that as well.

If Holden did come out with a different figure something must be changed in the HQ-J the 253 in the HJ has a smaller cam, but you reject that is true, but I believe it must be so, as to understanding cam spec being made longer after TDC, like on the intake side if it was 20/60 and this goes to like say 20/65 and it's the same for the exhaust spec being extended at the closing point, that is done due to emissions laws, like we see with the HJ 253 so it is heating up the exhaust to burn up the un burnt fuel and it's the same thing we see with the 308 HJ and that's why the compression had to be increased because what was lost with that cam had to be increased to keep the volume efficiency compression much the same, or the power lose would of suffered.

So ok HJ cam in a 9.0 static compression would of been less efficient making less power, so they had to up the static comp to set it to the same volume efficiency as the HQ was.

You can not put more duration into a cam and not increase the static compression or you will loose volume efficiency and that's why you see the XU-1 come out with such high static compression but it's running compression may be just the same as a stock 202. if we did not lose that compression with the bigger cam we would not have to increase the static compression to save the real running compression.

So when we are confronted with a Octane rating we must abide with in that frame work or we will loose power and have to retard the spark timing or end up destroying the engine.

Putting a XU-1 cam into a low compression 202 of 7.7:1 would not ping on the Standard fuel of the days 87 octane but it would be gutless and no point in doing such. we only increase the static comp to save the loss of compression when the engine is action as to it's volume efficiency.

So we have a HJ 308 with 250hp gross and a HQ 308 with 240hp gross, but but what about with a single exhaust and the dual hey ? well we do not know the figures now do we, but it would be good to know.

With turbo engines one has to lower the static compression because the volume efficiency is increased but to be sure to be sure that the running compression will never exceed the fuels octane or it will blow up.
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#27 Posted : Sunday, 16 December 2018 1:49:37 PM(UTC)
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Nothing changed in the HQ-HJ transition except for the 308. I have the Engineering specs for both and they are identical yet power and torque figures drop, except for the 308. I reckon the figures weren't right and they made them right. GM Corporate did have some general edicts issued in 1974 about different things, truth in advertising may have been one of them. I do have real HQ 308 power figures and they are less than the published 240, so I reckon the revised HJ figures are actually correct, including the 250hp for the revised 308. The HT-HQ 308 real figure is just under 230hp, and that compared to the advertised 240hp is about the same % less that all the HJ figures were changed to compared to HQ advertised.
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#28 Posted : Sunday, 16 December 2018 3:19:01 PM(UTC)
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Originally Posted by: abi Go to Quoted Post
What Terry and HK are saying is bang on true, the drag racers have been using this very accurate formula for decades. Google 'Moroso horsepower' and you will see trap speed and weight have been used since the 1960's to calculate engine output and is spooky accurate.
Another old saying - tune for trap speed and tyre and gear for ET.


That is true, but as you also say, tune for trap speed and tyre and gear for ET. None of the cars tested were tuned or set up for any particular timing test were they. They were supposedly from the factory. Did they check tyre pressures etc?
You can’t use a Moroso type calculator because you have absolutely no idea what any of the variables were. You don’t even know if old mate put standard fuel in by mistake, instead of super. Were the cars supplied by the manufacturer? I know that the level of setup varied between bike manufacturers, some going to more sneaky effort with supplied bikes that were not exactly as you could buy from the dealers for dirt bike tests.
I used to read all the dirt bike magazine tests back in the day. Sidetrack magazine used to get bikes after some other big name mags had tested new bikes. The bikes would turn up with suspension clickers set on different numbers on each fork leg etc. then these other mags had done a ten page test on the bikes and come to conclusions when they hadn’t even got the basic set up correct.

Edited by user Sunday, 16 December 2018 3:39:48 PM(UTC)  | Reason: Not specified

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#29 Posted : Sunday, 16 December 2018 3:27:07 PM(UTC)
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The cars I’m interested in are optimally tuned, not too interested in manufacturer supplied cars. There are some key tests of cars properly tuned to factory specs. None of them would run on Standard fuel. It isn’t academic or hypothetical. It will work and give real confirmation of the vehicle’s hp, that is all i’m interested in.
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castellan Offline
#30 Posted : Monday, 17 December 2018 10:16:10 AM(UTC)
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Originally Posted by: wbute Go to Quoted Post
Originally Posted by: abi Go to Quoted Post
What Terry and HK are saying is bang on true, the drag racers have been using this very accurate formula for decades. Google 'Moroso horsepower' and you will see trap speed and weight have been used since the 1960's to calculate engine output and is spooky accurate.
Another old saying - tune for trap speed and tyre and gear for ET.


That is true, but as you also say, tune for trap speed and tyre and gear for ET. None of the cars tested were tuned or set up for any particular timing test were they. They were supposedly from the factory. Did they check tyre pressures etc?
You can’t use a Moroso type calculator because you have absolutely no idea what any of the variables were. You don’t even know if old mate put standard fuel in by mistake, instead of super. Were the cars supplied by the manufacturer? I know that the level of setup varied between bike manufacturers, some going to more sneaky effort with supplied bikes that were not exactly as you could buy from the dealers for dirt bike tests.
I used to read all the dirt bike magazine tests back in the day. Sidetrack magazine used to get bikes after some other big name mags had tested new bikes. The bikes would turn up with suspension clickers set on different numbers on each fork leg etc. then these other mags had done a ten page test on the bikes and come to conclusions when they hadn’t even got the basic set up correct.

Yes I get sick of bike test that the riders do not the time to set the bike up for them, or don't know how to or jet the bloody thing, so it's only a lot of worthless info and I wonder why I bothered to buy the mag in the first place, thinking what a half arse test by f wits.

My brother had a 1981 Kawasaki KLX 250 and a mate had one as well, I road both and said to my mate ride my brothers and you will be blown away, my brothers is just so much better on power and setup of suspension. they were like chalk and chees, to ride it was like they were totally different bikes.
The same can be so with cars, some little mods can make a hell of a difference, take a HQ 202 for example people would bag the hell out of them, but when they drove mine they were impressed, what this thing handles and goes well, this has a freak motor etc BS!

When testing a car it's not all about the max HP or 1/4 mile.
Back in the day one would look at a new HK GTS327 Monaro and understand what it was and what the opposition had to offer and then again we have the lower powered HK GTS327 ones but they have some other goody's that may appeal at the time.

Or we could look at the HK GTS 307 auto VS the XT GT auto or 4speeds in both and it's not all about the max HP as to why one would buy such.
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