Why dyno days often disappoint...

For those who wonder why their cars underperform on a dyno day, here's why! It's especially true for dynos with very small cooling fans.

Adam.

ps - images are 500k each.

http://www.volvotuninguk.com/volvotuning/dinandyno1.jpg
http://www.volvotuninguk.com/volvotuning/dinandyno2.jpg

[Ross9]

Interesting reading there Adam, I'm sure a lot of people will have been interested by that.

The difference between a well cooled Dyno and a poorly cooled one is definately notable, even by a car that does not alter the mix etc as much as the car mentioned does, the simple fact that intake temps are through the roof will make a car suffer.

At a recent RR day my intake temps got up to 77.7 degrees by 6500rpm, done in 500rpm increments, the run is "stepped" so the car is on the rollers longer than a normal sweep from 1000-limiter and heats up. Peak power was at 6000rpm and was 69 degrees at this point. now we all know this is way to high, the engine was getting a bit of detonation etc.

There are also two main "normal" dyno's used by most up here, one has much superior cooling, and I've seen the same car run on both two weeks apart, on the same spec...and drop around 30 BHP running on the "hot" dyno, unfortunately I made my 235 on the hot one, maybe I'd have got more on the cooler dyno, we live in hope lol. I only managed 187 BHP at the same RR with just the boost turned up (standard 197) and I blame the cooling for that, made 23 lb/ft above standard but as the run progressed and the turbo and intake temps went up the car died off and overfuelled, so I would definately say the article is making a lot of sense.

A Rolling road is always a lottery, it's a valuable tuning and diagnostic tool, but RR days for power figures are never going to be that accurate for flywheel BHP, there are too many variables, the best thing to do is to compare what you get with other cars on the same rollers on the same day.

Ross

Agree entirely with Ross's post - dyno days are a lottery. It does however seem strange that on the day of you ECU upgrade the dyno always 'seems' to get the right figure but then when you go to the third party dyno it is always lower.

Karl

Well, there is a difference between a "dyno day" dynamic dyno run, and dyno testing for tuning purposes. During a dyno day, the dyno operator will not give a flying fish about heat soak, or any other problems associated with dyno testing - the idea is to simply get as many cars through as possible!

Dyno testing for tuning purposes however is totally different. The dyno operator will ensure maximum cooling, will let an engine cool down between dyno runs, and will also do static dyno testing to reduce heat soak. The idea is to eliminate as many of the problems as possible that will affect the true power readings. Problem is, all this can take a whole day, which is simply too expensive and impractical for a dyno day.

Adam.

Totally agree but I have also been on non dyno days - just me - so none of the above applies.


Karl

[pyaap]

I second that. I've had readings ranging between 120 and 240bhp with no physical changes to my car. To me, rolling roads are a useful diagnostic tool and that's about it. However, with regards to cooling fans, based on the report on the DINAN setup, I guess the rolling road at Owen Developments must be one of, if not the best in the UK; the cooling fans are enormous on comparison to anything else I've seen.

Our dyno is also mainly used for diagnostics. What better way of putting the car under load while stationary!

Adam.

Karl,

Where did you go? What size was the fan? And what kind of dyno test was done? Was it static or dynamic?

Adam.

[foggyjames]

I think a lot of folk are slightly suspicious of certain areas of the 'car work' market - a classic example being the tyre shop. Kindly request that they don't air-wrench your wheelnuts on and you traditionally got some very odd treatment! Anyone remember the 'Hi-Fi shop' "Not The 9 O'Clock News" sketch?!

This definitely applies to things like Rolling Road tuning specialists, which is why choosing a reputable firm is so important - and I'm pretty sure why Adam and Don do so well here, because they put lot of time and effort into being part of the community, and a good reputation is built out of that.

Can we just clear one thing up which always grates with me...
A Dyno is a 'testbench' device which you hook the engine up to.
A Rolling road is the device you run your whole car on.

Speaking of which...have you fixed your rollers yet Adam? I can't wait for the next RR day to see how many of my supposed 105 horses I have left!!!

cheers

James

[TheJoyOfSix]

> I
>can't wait for the next RR day to see how many of my supposed
>105 horses I have left!!!
>
>cheers
>
>James


The way you were driving the other day I'd say about 50! :9