Dyno, how too?

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Ive been thinking, if I change over to a Crossflow later I have the opportunity to accurately match the performance of my 2V against the Crossflow by putting both on the dyno.
First could someone tell me what would be the minumum time or runs on a dyno to get accurate figures.
I also need to retard the timing around from 204 to 212 at 50 on the 2V because this is the minimum cam I would be happy with in the Crossflow. I would try and keep everything as evenly matched (carb ignition etc) as reasonably possible.
They quoted me $150 dollars and hour for the dyno, but said it might be cheaper if I just wanted a HP reading.
I would also like to know if I do need to drop the sump on my 2V to retard the timing on the gear. I was hoping to just remove the balancer and the timing cover to get at it.
 
There is a DIN (German Industrial Standard) for flywheel dyno runs. David Vizard used a similar variation, but base lines it against a US SAE net standard which is even more conservative. There are JIS and BS (bull sh**?) standards too.

The type of dyno used should have a current calibration certificate to the appropriate ASTM or SAE standard, by an independant agency such as Telarc, IANZ, or the Aussie ISO 9000 equivalent.

The acceleration rate is 300 rpm climb per second, and there needs to be five runs to produce a minimum deviation bell curve for a statistically accurate result. Any flash high reading not substaintiated is ditched. The barametric pressure, intake temperature, realtive humidity and tyre type (pressure and wear) must be exactly the same, or at least, corrected to exactly the same standard. And try ond get a print out referenced against the rpm level, not the road speed, because it makes the torque calculations easier. The overall gear ratio its tested with is important to resolve the accurate shaft torque.

There is a widely debated issue about rear wheel hp being one third the flywheel hp is not always true. Tire section size changes things too. A T5 equiped Falcon XR8 has 221 hp at the flywheel, but 175 hp at the rear wheels with 205/60 15 tires in 3rd gear. The factor is 1.263. On a BTR auto, it's down to 1.333. On a good Front drive car with narrow, tall tires, it can be 1.20 or even less.

If this sounds like a lot of details, know this. One flash reading from an uncalibrated dyno is a lie. No lie can give you a statistically correct answer, and is not much use at all. It's nothing to get a 20 hp difference between two dynometers in one town on a 1300 cc worked Mini with 50 hp at the wheels. With a Falcon, a 100 rear wheel hp engine could read 40 different, and show 50 hp difference at the flywheel.

One other option is to pool a dyno run with a mate with a more modern car without any alterations. If you can base line his car, then you can have a method of comparing that run to the DIN kw rating. It's a loose connection, as any factory 200 kw car can vary in peak power by 20 kw between highest and lowest. Ford got into an awfull pickle in the 90's with the 200 kW EB GT. They used the US Mustang Cobra power plant and engine rating, and didn't do enough pre-flight checks on a press GT. A car mag dynoed it and got slightly less than 150 kw at the rear wheels. Ford ripped the car appart, and got 190 kw on an engine dyno, close enough to being within the +/- 5% accuracy threshold. They the rationalised that the air intake clamps were over torqued on the production car, and this caused a calibration problem.

Power figures, the web of intrique!
 
I understand the curiosity behind wanting to see the difference in power between the two engines, but objectively it's a waste of time and money to dyno an engine that you will remove. That engine is what it is and you intend to replace it anyway. And like Xecute said, a single run is not going to tell you with much certainty anything. It takes at least three runs to get a baseline, and several more to do proper tuning.

What I would do is to make a couple of runs down the strip with the current engine to gauge its performance. Keep a record of times and air temps, car weight, tire pressure, fuel level, etc. All the variables.

Then build and install your crossflow, do a couple of baseline runs to get some readings, and use any consequent dyno time to optimize that engine. Then back to the strip to see what the improvement is. Duplicate the former variables as closely as possible and keep track of any differences. You'll then be able to gauge the real differnce between your old 2V and the new X-flow. Dyno HP numbers are all relative and may not be absolutely real, so the true test is in performance.
 
That is sound reasoning. I will do as you suggest, HP figures and times. Times are the real world!
Ive already got very consistant 0-63 mph times, but with my rather muted cam. My times went down from 8.62 to 8.42 when I reved an extra 400 rpm past 4000 rpm. Execute tells me I would need at least 155 hp to do these times (hard to know how you work this out when much of the time from 0-63 cannot be at max revs allowing for revs to build and gear change drop?)
From info on this forum I think I could free up another 40-50 HP by having more duration and reving to 4800rpm (Come cams say you dont lose much torque so long as rpms stay under 5000) which it feels like it could do easily.
If I cant easily retard (peaks higher) the duration on the 2V (without dropping sump) then the comparison will break down and will not be worth doing as I would to use a hotter cam than the one I have in the Crossflow.
I think we all know the crossflow is a better breathing head I would just like to know by how much. The problem is they are probably too closely matched and so many variables can alter the outcome.
After market cammed crossflows have more lift and bigger valves (2V 1.65, crossflow 1.75, 1.80). The amount of lift possible is related also to the valve size, lift approx 1/4 of valve size) on that bases alone I would expect some difference in performance. This does not account for the port sizes and departure angle differences. The other thing that is also often forgotten is that the 2V comes standard with extractors and its "potentual" must always be factored with that already inluded as a baseline.
Important to consider when the crossflow nets a big improvement with these fitted. In a word, It has to be better. I guess thats all I really need to know. As to exactly how much, I might have to leave that for someone with lots of dollars and expertize.
Thanks for your help.
 
I agree with Jack, the dragstrip is the best idea.
The other thing that srings to mind is to buy a G-Tec accelerometer type device and conduct your own testing, you can buy one for the same money you are likely to spend on dyno time, and still be able to use it in the future.
 
The other change Ill have to make is to get rid of my rear re-treds that is why I have only done 0-63 mph times. The re-treds are 135 kph speed limited (I wish I had realised this when I bought them). Its easy to forget and do this speed even when over-taking a slower vehicle.
 
That is the same as all unrated tires. That rating is a constant use rating, not a max speed rating. I'd take it to ~180-190, but I wouldn't suggest keeping it there for long.


-=Whittey=-
 
I would do the hour long session. The shop up by my house will give you the lift for an hour for $100. They hook up O2 sensors, and other stuff so you can tune and jet the engine properly, not just get a HP.

Slade
 
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