Rally replica on Ebay

[rallymanDP]

In plain English, Craig, I think the nearest we can get to an answer for you is around the 138-140bhp mark ( at the Flywheel ), on the standard Carbs & Exhaust system - that is, for the earlier Engines - up to late '72 Production.

Anybody else got a better idea ?

 

[SeanDezart]

So............who's bidding for this car ?

 

[Albrecht]

Anybody else got a better idea ?

Which market version - and which year ( and month ) - are you talking about, though?

Which compression ratio, which head, which distributor, what power-sapping bolt-on emissions devices?

The answer is that there are several answers, and all are wrong.

 

[rallymanDP]

Any chance of you being a touch more constructive, Alan, and answering Craig's question ?

 

[Albrecht]

"Constructive"? He's asking how long a piece of string is.

What market version, what cylinder head, what compression ratio, what distributor....?

My point is that not all "240Z" engines were the same. Why do people think there will be just one figure that is 'right'...?

 

[SeanDezart]

Euro spec 240Z (L24 no emissions) sold from 1971-1973 (with a few left over sold in 1974).....please.

 

[Albrecht]

"Sold from 1971-1973" covers at least three different cylinder head castings, and is your definition of "Euro spec" the same as Nissan's ( ie did all "Euro" spec cars during that period have the same model of distributor, exact same carbs and compression ratio and carbs )?

I'll quote myself to make the point again:

My point is that not all "240Z" engines were the same. Why do people think there will be just one figure that is 'right'...?

 

[SKiddell]

covers at least three different cylinder head castings

OK so thats one more than I thought (E31, E88) I have seen pictures of at least 2 E88 variants would that account for the 3rd?

I would be very interested to see any numbers Alan, particularly for an E31 setup, presumably if there is any data it would be on leaded fuels ?

 

[Throttleton]

It is a 1972 registered car . The head has E88 on the side. Carbs appear to be original as far as I can tell. Distributor appears original but no idea about different ones.
If too many variants to be accurate then I suppose Duncans' 138bhp would be good to get near to.

 

[Albrecht]

If too many variants to be accurate then I suppose Duncans' 138bhp would be good to get near to.

Duncan's figure was quoted as being at the flywheel. You'd need to put it on an engine dynamometer ( as opposed to a chassis dynamometer ) in order to measure it.

Then you'd have to expect to have the calibration of the dyno questioned, the configuration of the engine as tested questioned ( with ancillaries, with some ancillaries, or without? ) as well as the - inevitable - questions as to whether your engine building and setup / tuning is representing the maximum stock capability of the components therein.

Point being - as I've been trying to get across - is that it's all a moveable feast......

The answer is that there are several answers, and all are wrong.

 

[Throttleton]

Blimey....is it even worth going to a rolling road in my case then ??

 

[Mr.G]

Best rolling road is the drag strip . Go before and after!

 

[Throttleton]

Best rolling road is the drag strip . Go before and after!

There is no 'before' that's the problem. I have nothing to compare to which is why I thought the rolling road was a good idea.
I suppose if I get a reading albeit slightly innacurate it is a reference point at least for when I do mod the engine.

 

[Albrecht]

Blimey....is it even worth going to a rolling road in my case then ??

Not if you're looking for a single number, as this thread has shown.....

A rolling road is just a tool to help you set the engine up. A way of measuring the effect of changes that you make by comparing before and after. It's not a tape measure or a weighing machine. As you will see, the power figure you get given on a piece of paper is open to all sorts of interpretation and criticism.

Best rolling road is the drag strip . Go before and after!

I find it hard to agree fully. Too many variables. If two people drive the same car up the strip and get different results, does it mean that the car has somehow changed? Drag strip will only give you some indication of the potential. It can tell you - through mathematical calculation - that an engine must be producing roughly X amount of power in order to return the time / speed it has just recorded, but that doesn't mean it's what the engine ( filtered through the drivetrain and tyres ) is producing. The calculation will tell you that it "can't be less than X"....

If I jumped into a Top Fuel car and ran an 18 second quarter at 110mph it would not be representative of the potential in the car, would it?

I think the drag strip is just one more way of telling you what your engine might be producing.

 

[Mr.G]

There is no 'before' that's the problem. I have nothing to compare to which is why I thought the rolling road was a good idea.
I suppose if I get a reading albeit slightly innacurate it is a reference point at least for when I do mod the engine.

Well, I had thought you could take it to the strip now, i.e before the mods you intend to do. This Sunday at SantaPod .

Alan, I agree with the many variables that the drag strip can entail and the theoretical bhp can differ and this may not answer Craigs initial quesiton. However, if Craig wants the bhp just for a benchmark purpose to see if future mods have provided an improvement, then I can see how the drag strip could help providing Craig perfects his technique so that his times and technique are consistent. There will always be variables at play, air temperature pressure etc... but a rough approximation is probably all that Craig is after?

 

[SeanDezart]

I find it hard to agree fully. Too many variables. If two people drive the same car up the strip and get different results, does it mean that the car has somehow changed? Drag strip will only give you some indication of the potential. It can tell you - through mathematical calculation - that an engine must be producing roughly X amount of power in order to return the time / speed it has just recorded, but that doesn't mean it's what the engine ( filtered through the drivetrain and tyres ) is producing. The calculation will tell you that it "can't be less than X"....

I think the drag strip is just one more way of telling you what your engine might be producing.

There's someone here who always claims that the % difference between different drivers is minimal....but I still have my doubts - me who has done maybe 3 runs in his whole life v. he who has 'worn out tyres in one season dragging' has got to be quicker up the strip.

Agreed, that the rolling road is merely a set-up tool which most of us quote and is meaningless in the big picture.

That said, the differences between an L24 with this or that in "euro" spec between the years of 1971-'73 can't be enormous my Count so please climb on out on that limb and say RW power between 'x' and 'y'.

 

[JK240]

Sorry to take this back to the original topic cool but this is finishing in a day or so and only has 2 potential buyers bidding £15,600 so it's way off the suspected reserve of around £25k, will it see a last minute ebay flurry...?? Are the buyers on here...??

 

[SeanDezart]

It's me - Ian 'powerfully' convinced me and being LHD - I can sell on the donor car !

 

[SKiddell]

There's someone here who always claims that the % difference between different drivers is minimal....but I still have my doubts - me who has done maybe 3 runs in his whole life v. he who has 'worn out tyres in one season dragging' has got to be quicker up the strip.

And "he" has always maintained that its the average of "many" runs that gives the accurate figures

And why is it that you think its "my" opinion, its the opinion of some very well respected physicists and engineers like err David Vizard for instance, he recommends in several of his books using the drag stip as platform for testing engine modifications and even cites some of the maths.

The statistical theory being that the more runs you do the more accurate and representative the figures

As for 3 runs Sean, were they on an accredited 1/4 mile ?? if not then you have done 0 runs.

For reference (once again, this time please actually read it before posting a reply) I link to

Stealth 316 - Formulas for 1/4 mile ET & mph vs. hp & wgt

In particular the spreadsheet http://www.stealth316.com/misc/performance_lrt2.xls

This guy has collected 243 1/4 mile times from various cars and plotted their calculated HP on a graph (he uses several poplular methods) read the article then tell me that the drag strip as a method of HP calculation doesnt work

Or if your not happy write to

God
Care of Heaven
123 Pearly gate street
Eternity

And start the letter with "I would like to complain that the laws of physics are way too accurate"

 

[SeanDezart]

You'd have been burned at the stake as a warlock not long ago !

Just flouncing a touch of SP98 on the fire.........and it was Santa Pod back in 1991 so I guess any hints I learnt are date-expired now !

Of course I agree upon a drag-strip being a "platform for testing engine modifications" - I just can't see it being a definitive measure just as it must have two cars on the same day, same rolling-road, same tester to be of any relevance as a comparison and even then is only what THAT tester produces on a graph.