unclefester

Having seen a number of exhaust threads and the usual 'what's the best intake' type threads, I'd like some feedback on some questions I have.

1. No Dyno is truly accurate and most will fluctuate between days depending on weather, temperature etc, so many factors.

2. A Dyno fan cannot immitate the effect of real airflow over the front of your car at motorway + speeds. Therefore airflow, air temperature and cooling are not 'real world' and may be more or less than optimum.

3. Increases in power from various intake / exhaust mods is 6 to 10bhp at most?

4. If the above is true and bearing in mind that's between a 3% and 4% increase on stock, how do you know it's not Dyno lottery clouding the results?

http://www.eurotuner.com/techarticles/0412...ison/index.html - they state a 6% error margin for Dyno results. According to that, there's 2% more error to factor in than the increase apparently recorded.

I can see how FI, be it turbo or supercharged can be measured, that's too much of an increase to be mistaken for anything else, the 6% error margin is neither here nor there. I know from my previous car how much difference a decent intake/exhaust system and cooling system can make to a FI car. What I can't see is how anyone with a NA car can reliably claim to have gained X amount of bhp at a certain rev range when the results are based on figures that are smaller than the percentage of error built into the results.

I'm fully expecting varying opinions but as above, i'm interested to know what others think.

I would like to close by stating that both PRM and Blueflame were fitted purely for the way they sound because I don't believe they gain me or lose me anything in terms of performance, certainly not enough of an increase / decrease to accurately and reliably measure.

lovegroova

I think the best way to test he effect of modifications would be to hire an airfield for a day, get some data logging equipment and do some acceleration runs from, say, 20mph to 100mph. 20mph wou be used to avoid clutch damage and remove the randomness of getaways.

That would sort it all out.

unclefester

That's my view too Simon. I'd be interested to find out just how much real world difference there is between the NA cars with intake / exhaust mods but with stock gearing.

eSeM

[QUOTE=unclefester,Feb 3 2010, 11:30 AM] What I can't see is how anyone with a NA car can reliably claim to have gained X amount of bhp at a certain rev range when the results are based on figures that are smaller than the

Owen_1987

I agree, probably all dynos will give you different results just because of the way they are callibrated. Although I think the dyno fan will be good enough to emulate wind, I imagine it will always be slightly cooler than the outside temp.

I think the most accurate way to see how a mod has increased the bhp/ torque is to have multiple runs, then you can take an average. Although i would still expect there could be a 2-3% fluctuation?

Another way could be to do 2 runs, 1 with the car standard and 1 with the mod. Easy to do with intake for example but very difficult with an exhaust system. I imagine it will be more accurate than the one above, but not always do-able.

Owen_1987

I agree with that, it's all about the power/ weight ratio

lovegroova

My view is "not much".

A car with 250 or 260 bhp isn't going to make up much on a car with 240bhp over anything up to 1/2 mile. The FI cars will, however

The extra noise mods make certainly help to "fool" us into thinking something is faster than it really is, final drives being a great example. The "average" human being isn't very good at accurately gauging g-forces.

Making the car go round corners quicker is the best way to make it faster. I remember leaving Adrian (Sti Vi) in his Mugen'ed car way behind me after going round a roundabout. Mostly because I knew the roundabout very well and was able therefore to carry a lot more speed through it and thus onto the straight afterwards.

eSeM

Dyno runs are usually done with the bonnet open so difficult to get meaningful results from testing different air intakes.

Owen_1987

would it not be acceptable to do it with the bonnet closed with more fans/ more powerful fan?

unclefester

Supercharge it, Turbocharge it or shut it .....

From my understanding, any intake / exhaust mods should be considered as supporting mods if you're going for FI - other than that it's pub Dyno talk and nothing more.

FWIW i've yet to see reliable supporting evidence on other forums too