FCS Dyno graph

[Scott]

Some are more accurate than others and there are a lot of different variables in dyno runs, so that's why it's best to do two on the same day at the same place before and after a modifcation if you want more accurate results. The ambient temperatures should be approximately the same, it'll be the same fuel in the car, same dyno operator...the list goes on.

[Ruan]

Calibrated to what though...

If they read your RPM wrong, or your tacho is wrong... You can completely skew the results...

Say a car made 250lb.ft at 3230rpm - that's 153.7HP, say they read that as 3130rpm - that makes 148.9HP... And they NEVER read it accurately, they just run it up to 3k to guess the gearing... Not to mention if your tacho reads out too.... Unless they laser tacho it, it's fruitless...

Hence why most RR days are totally pointless, unless they know exactly what the RPM is, they can NEVER give an accurate HP figure, the only figure that might be CLOSE to correct is the Wheel Torque figure... And unless you go to the same dyno, on the same day, using the same engine RPM reading, at the same temperature - you can NEVER get an accurate figure, they'll say that they can correct the temperature and barometric pressure, but they just can't - they don't take into account if you have an intercooler, which is badly affected by ambient temperature...

And don't even get me started on handing out flywheel figures, look at my dyno graph, I ended up having to correct it by hand for a remotely close ATF figure, they based it on a 5% tranny loss, I went for 15%, and it's probably more than that, a 180k mile gearbox on old engine oil probably saps more than 15%, especially when you've got 300lb.ft+ going through it!!!

[Toms306]

So is there any way to actually get a proper acurate power reading then? I'd assume not from what you said above??

Also........the RPMs were way out on my graph (I was doing 19000rpm at peak power lol)........so this MUST make the power inaccurate surely? As my tutor said it had been calibrated so he was sure the power read accurate even if the revs didn't, but I can't see how that could work??

[darrenjlobb]

No dyno is ever "right" as it depends on to many things...

But the thing most likely to be right / close is the torque reading, not so much in line with the rpms on graph, but just the peak torque / delivery of torque in some way... That only depends on the dyno load sensor being calibrated correctly, which in most cases shouldnt be far out, unless there playing silly with your money..

HP is obviously directly calculated from the rpms the motor is dong, now 99% of dynos, just nick this straight from your car tacho, so they bring your car up to say 3krpm, look at your tacho, tell the computer its doing x rpm there, and the computer can then calcuate the gear ratio to know what rpm its dong at any point in that gear during the pull....So instantly if your car tacho is out (which often is) the hp reading / grash will be skewed totally, and as Ruan pointed out, 250-500rpm out, can make a big different to the output... You can buy laser rpm meters from china for like 11 quid delivered, so worth getting one and revving car thro each 1k mark on your tacho, and looking to see how far out it is, because you will be quite suprised when you do this!

The next issue for diesels is dyno operator....alot of the bigger power 11mm cars, dont have very effective fuel control at all, hence the smoke...this creates chronic ammounts of bogging resulting in the turbo coming in much later than it would normally have, therefore ruining your normally driveable car and producing a graph that looks like shite...

Then obviously on top of that, you have all the other varibles like weather / temperature, lack of fans giving as much cooling as you have normally on the road etc....

In other words, dynos are never that reliable, just a usefull tool to give you a rough idea of the power, and for comparing cars directly one after another, or modifications if done at the same dyno...

Not to say your shouldnt read much into the results, as on a decent hard standing calibrated dyno, the results should be pretty good, but id only trust a dyno up to 10/20% as they read so much pants at times...

[Toms306]

Ah ok, that makes sense, cheers.

I hope the torque was out on mine though.....cos I only made 70Nm max haha.

I expect the rev counter probably is out tbh, and thats exactly the way I did it. Just held it at 2k to get the reading.....but as soon as we started the actual test the revs went miles out, so thats a fault with the actual dyno I assume.

I suppose thats sort of where ECU control wins over mechanical control as you can't really bog it, if theres not enough air detected, it won't just dump the fuel in, so I didn't have a bogging problem like that......and I'm a very inexperienced dyno operator haha.

Still be interested to get it on a proper dyno though.....

[Atterz]

I think a dyno is only useful if you want to know what gains or losses you get from doing different things, and the only way to keep it relatively consistant is to use the same rolling road time after time with the same wheels/tyres etc. And even then that doesnt account for atmospheric conditions!

[Eeyore]

They can be miles out. Hell, you can fiddle the result to double if you wanted to.

But surely they're all calibrated to the same lol?? Oterwise a dyno graph/reading is completely pointless (just as pointless as the one for the golf haha).

one lol is very different to another lol though tom!

[dervpower]

i still havent had my dyno graph neither has my mate with the beetle

[darrenjlobb]

Mine took about a week to come last year..

If you dont get it I can give you the email address that mine came from

[strictly_perv]

Mine took about a week to come last year..

If you dont get it I can give you the email address that mine came from

Still no e-mail. Could you give me their e-mail so I can message them?

[darrenjlobb]

Yeh give me 5 mins as ill have to search my inbox to find it!!

---

Cant find the email, but these were the guys

http://www.mtechautomotive.co.uk/rolling-road/

[Eeyore]

still havent got mine! Anyone got theirs?

[4WayDiablo]

Terrible service lol

[strictly_perv]

Thanks Darren. I've sent them a message on Facebook now.

[darrenjlobb]

I told one of the FCS people to get there arse in gear and find someone better to do the dyno next year, as those guys are a bit of a pisstake tbh!

[Eeyore]

I told one of the FCS people to get there arse in gear and find someone better to do the dyno next year, as those guys are a bit of a pisstake tbh!

good job! If it hasnt come by tomorrow night ill be writing an angry email!

[strictly_perv]

They are utter wank. I wasn't going to do it when I found out they had no fan but was peer pressured into it as everyone wanted to see some boosted XUD action

Was a laugh to see though. Although they got really fun when I sat in the car rushing me for the cash.

[darrenjlobb]

Bunch of twits tbh, in competent / crap....

[strictly_perv]

After alot of hasstling over Facebook they finally got them up.

http://www.facebook.com/media/set/?set=a...406&type=1

But they havn't bothered labeling each one of what car it was...

[darrenjlobb]

Have they not even taken the time to bother emailing the graphs? Like seriously wtf....30 quid, and you dont even get a printout, and have to FIND your graph...wtf!

[Sambarker]

So if I've got no rev gauge does this mean I wouldnt be able to take mine on a RR?

[darrenjlobb]

So if I've got no rev gauge does this mean I wouldnt be able to take mine on a RR?

Depends how competent the garage are....

Just buy a laser pen on ebay for 11 quid, stick bit on your crank, and tell them to use that if you have to, but any DECENT stationary dyno station will have a proper laser sensor anyway, as using the tacho is not very good in any case...

[Toms306]

I think (and I'm sure someone will correct me if I'm wrong) some dyno's use a thing on a diesel which clips onto the fuel line to measure the injector pulses or something like that. And can calculate the RPM from that. Thats what I was told when I asked about dyno'ing the 106 (no rev counter) for lolz anyway.

[darrenjlobb]

Yep, you can get pulse sensors, can be used for timing light on a derv also...anything like that is fine, just need an accurate rpm readout really!

[strictly_perv]

Sooo after alot of messages and no replys I've just given them a call and he said he will get it sent off tomorrow morning. About f*cking time!!!!!!!!!!!!!!!!!

[darrenjlobb]

Did you tell them that they royally suck while you were on the phone?

[Eeyore]

i emailed them and got it sent 3 days later! No sorry or anything just a reply with an image attached! complete shit!