Power claims

SeanDezart

SeanDezart

Well-Known Forum User
What seems to matter to some is THE number ! How much bhp, perhaps after having spent out 'X' £ to reach said figure. Is this a means to justify the expense or to impress or a self-congratulatory acheivement ?

There is one who states that the only true test of engine power is by the 1/4 mile.

There are those that test theirs' on various rolling roads. Even assuming that all r-roads and testers and weather conditions are alike, what is the agreed calculation for power loss through the drive-train ? Is that affected by having upgraded the drive-train ?

My engine figure for example is 219 at the wheels for a 3.1 n/a. Others I've seen quoted are 370 (where ?) for a 3.2 n/a and more recently 283 at the wheels for 315 at the flywheel which means it's losing just over 10%.

Using that figure and not the +/-20 that I always believed, the 370 engine (assuming that that is a bench test) is giving 330 ish at the wheels for a n/a SOHC - astonishing !

And mine is only giving 240 ish !:(

Never mind, what counts more I suspect is how that power is delivered and I suspect that more than 250 (flywheel power) is an awful handful to keep on the road unless the car is set up as a racing Z !

Any thoughts ?
 
Hi Sean ! Long time no speak :) Just an interesting lil note,,I work with a fella who worked on K Bernsteins drag car from a few years back ( early 90's) He says when they went down one grade on the gearbox oil, say from 60 weight to 70 they could loose about 10% of the 1600 hp they had :eek: amazing just with a bit thicker oil,,,makes you wonder how accurate any "formula" can be due to different build tolerances in drivetrain etc ? :driving:
 
Nigel Brook said:
Thank God power is'nt everything in rallying. You actually have to be able to drive:D
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That's it in the nutshell. 330hp in a NA Z is useless in the hands of someone who can't use it. A cool guy once said to me (when he whipped their ass in his old Z at the strip) that a 13 second car is no good if you have a 15 second driver.
 
No doubt the Japanese are getting 370bhp at the crank, I think the Wako engineering car is doing 10s 1/4miles. But as you say it is the way it’s delivered and I would think it would drive like rubbish on the road. But at the end of the day they should be applauded for pushing the game on and if that know how is made availible to us we should use it much like I have done by getting my head made in Japan.

How many stroker Z's are in Europe or soon to be in Europe now? Maybe we should all get together and have some beers and get on the dyno and compare specs rather than procrastinating on here. At the end of the day we should be fighting it out with Porsche owners not other like minded Datsun guy’s!

But I would suspect Sean we will never know who really builds the ultimate L series engine, there are as you say to many variables and also it’s how well the rest of the car is set up in terms of handling, braking, reliability etc etc I’m certainly not building a 1/4 car just a nice rounded one with I hope 300bhp too:driving:

C
 
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its wot it does on the road that counts against these so called fast Beemers and alike,surprised a few boy racers since i had my engine done,as for going up the strip to see how it goes is not for me,not interested,tearing it off the mark and round country lanes that is where the real driving is done
 
nice comment from the guy who builds our racing v8's 'horsepower sells engines torque wins races'. how can you relate horsepower to drag strip times? you have to factor in driver ability, weight of car and driver, type of diff, ratio of diff and overall gearing, tyre compound and no doubt loads of other variables that i forget. couldn't you train a monkey to drive in a straight line?
 
We dont all look for number Sean, although it is nice to know how all my hard work is paying off, I also thought 10% loss was low, I have put some super slippery stuff in the gearbox maybe that helped, there were 18 or so cars tested on the day and most of them have been Dyno'd before so as far as I can see the numbers are good. and yes 300hp is a handfull on the road especially when it's damp, you just have to give it some respect.I built my engine myself nut and bolt upwards and didn't spend as much as most people do. we'll see how it does round Castle coombe this May!!! care to join me!!
 
I thought, and I may be wrong, that you could calculate the BHP from a run based on the terminal speed and the weight of the car. Anyone know if this is true?

With regard to a trained monkey driving in a straight line, that may well be true but I think there is more to drag racing than just driving in a straight line. Reaction time, clutch control, wheel spin, gear changes, etc.... will all have an effect on your time.

At the end of the day its another opertunity for a day out with friends and like minded individuals. Plus plenty to look at if your into automotive engineering.
 
I can say having run up the pod that you need alot of practice to put in a real good time!! I ran last year and was not happy with the time I acheived but, I give all credit to Steve K and the like for getting into the low 13's with an NA car that is some serious practice and dedication.
I will go back to the pod 09 and see if I can get into the 12's with a little work over the winter, and some proper tyres.
 
Steve'll get in the 12s in that ol' straight 6 next season for sure. There's plenty of fun to be had at the drag strip. The one on one aspect alone is just so cool. My favourite though is the hillclimbing in the loony powered Vitara's and old 405s & Celicas. Pikes Peak would be the ultimate for me I think.
 
Zed2k said:
We dont all look for number Sean, although it is nice to know how all my hard work is paying off, I also thought 10% loss was low, I have put some super slippery stuff in the gearbox maybe that helped, there were 18 or so cars tested on the day and most of them have been Dyno'd before so as far as I can see the numbers are good. and yes 300hp is a handfull on the road especially when it's damp, you just have to give it some respect.I built my engine myself nut and bolt upwards and didn't spend as much as most people do. we'll see how it does round Castle coombe this May!!! care to join me!!
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It wasn't a get at anyone Nick and I apologise for hijacking your figures to use as a demo. You do seem to stand by them though.....but never mind if I'm only getting 219 compared to your 283 (and I would expect a 2.8 t to easily top the 300) then yours must be a handful in the dry, let alone wet - I can light mine up in a straight line WITH the LSD ! Obviously quicker if I don't.......:eek:

How much bhp can one expect from a n/a road engine whatever the size ?

I would like to get away from who's got what unless it is to discuss valid points.

What % is lost in average on a dyno run ?

What can one expect to see on road car 'tuned' engines - I've seen the dyno of over 270 at the crank on a 3 litre but hardly for the road ?

Sorry, Steve but I keep coming back to this - one must need a whole lotta practice and iron out the variables before one can reliably state that ones' engine is giving out exactly 'x' bhp after having done a drag run.

Maybe what it comes down to is not what you've got but how it delivers and obviously how you deliver it on the road.

Torque counts for sure - my choice was for low down stuff - I imagine that we've all chosen the engine that best suits us and/or the desired application.
 
if your car is a good fast road tune 3.1 I would expect more at the wheels than 219, as my last engine on triple and mild mods dyno (somewhere else) at around 200 on the rollers if you can just stamp on it in the dry and it lights them up then you must be putting down good power etc. mine lights them in at least 1st and second in the dry just to compare.
The Dyno I used take the revs up to whatever you ask then allows the engine to drop back and this gives a transmission brake effect which is then worked out by the dyno not sure what losses are normally for a standard 240z box.
 
For me, and yes, I know it is personal taste, the tractability and driving characteristics of an engine woul be more important than the ACTUAL numbers involved.

For example, I like lots of low downn torque and am not into massively screamy engines like the S2000 - I like grunty, low down power - so I agree with you Sean, it's not all about the numbers, it is about how those numbers are delivered as well and how that translates to "road mannners". No point having full power in a narrow rev band, much better to have an evern, smooth spread of torque from low down.

In my DMS'd 535d, full torque is delivered from 2200 to about 4500 rpm - I like that.
 
In the interests of general discussion, this is my graph (for what it's worth).

Now, maybe it's pessimistic (I think Skiddell ran on the same dyno and found his result to be :( ) or maybe it's optimistic. Who knows ? Does it matter ?

Long gone are the days when I was impressed by having a graph that stated 180bhp in my greenie machine when I was probably struggling to get 160 and even then it detonated and got burnt off by more modest machines !

You will note that peak torque is at about 3800 but that might all change now as I no longer have a standard box (mine's brand new as well) ?

I've also seen some dyno read outs with smoking (slipping) tyres so not even they are accurate !
 
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amocrace said:
nice comment from the guy who builds our racing v8's 'horsepower sells engines torque wins races'. how can you relate horsepower to drag strip times? you have to factor in driver ability, weight of car and driver, type of diff, ratio of diff and overall gearing, tyre compound and no doubt loads of other variables that i forget. couldn't you train a monkey to drive in a straight line?
Click to expand...

Yep you are right. Im already fully trained.:D
Now can I have another banana please???;)
 
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