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RST · 11-22-2007, 03:54 PM

Ill step back into this and I'll edit my previous post -that doesn't help anyone.

I feel like I've been mis-quoted somewhere which is why I was getting hacked-off as I don't think we're debating the same thing. I'm still of the oppinion that your original statement is invalid. However, probably the same as for me saying I don't care about wheel Hp -which admittedley isn't true at all and rightly for the reasons you posted.

Somewhere down the line I think I've been picked up as saying that measuring an engine BHP is as simple as measuring a wheel BHP and adding a corresponding fudge figure. In fact, I thought I'd already agreed that it's less accurate.

I quoted something off the web page but I must admit, I never realised that test would be in-gear as to be honest I don't think for a minute that's valid either (look I'm agreeing again) and I'm not sure why anyone would think engine breaking came into it, coast down to me means powerless so I assumed they bunged it neutral. I know doing this in neutral would again remove parts from the drive line but I never introduced engine breaking into that discussion. Now reading what they said is reasonably correct, but I would worry why they never spotted this kind of stuff beforehand or during the test itself ...or more importantly the owner. You and I can tell if you've got a partially seized caliper but not half the folk I know. Again, I thought I'd mentioned innacuracies rather than absolute values.

Hmm, coast down losses vs acceleration. Jury's out on that one, the two are linked in an ideal world but I agree I'm not sure what the relationship would be. A coast down loss (out of gear of course) will be there under acceleration but totally distorted I guess asd there are different loads applied to bearings etc.

I have to say, that I can't see photobucket stuff so Nik's last dyno sheet is summed up by yourself. There are 2 questions I'd ask:

How accurate are dynos of any kind -and this is a separate issue? Assuming RWHP only, personally on a 200'ish BHP engine, on 2 dyno runs I personally wouldn't be surprised to see between 3 and 5Bhp difference. That works out something like 1.5-2.5% difference. I'm pretty sceptical on the actual accuracy of measurements generally from the engineering work I've done so far. I'm really nervous about accepting figures of this sort as I'm sure it's clear that repeatability and accuracy are 2 different things. When I saw Nik's dyno sheet the other month we compared and I believe the comment was passed regarding mods and Bhp increases that he had spent >>>> more money and got a return in the order of something that I'd have written off as a measuring accuacy (sorry Nik). When I do this sort of "calibration" through work I'd immediately scrutinise a) the period when the equipment was last calibrated and b) the calibration method. I'm still amazed how folk continue to issue accuracies on their equipment geater than the calibration method in the first place!!!!

My second question relates to the dyno centre, not the dyno. or the method. I wasn't impressed with that centre and as far as I can establish the majority of folk I've spoken to who have used them aren't either. I won't get into why as it's too easy to publically flame someone then get a legal letter through the door. I fully agree with you regarding Nik's figures and adds to my su****ions. There are of course folk who are perfectly happy. Nuff said.

11-22-2007, 03:54 PM	#49 (permalink)
RST Beams Owners Group Join Date: May 2007 Location: Inverness, Scotland Posts: 401 Thanks: 8 Thanked 22 Times in 19 Posts iTrader Rating: (1/100% )	Ill step back into this and I'll edit my previous post -that doesn't help anyone. I feel like I've been mis-quoted somewhere which is why I was getting hacked-off as I don't think we're debating the same thing. I'm still of the oppinion that your original statement is invalid. However, probably the same as for me saying I don't care about wheel Hp -which admittedley isn't true at all and rightly for the reasons you posted. Somewhere down the line I think I've been picked up as saying that measuring an engine BHP is as simple as measuring a wheel BHP and adding a corresponding fudge figure. In fact, I thought I'd already agreed that it's less accurate. I quoted something off the web page but I must admit, I never realised that test would be in-gear as to be honest I don't think for a minute that's valid either (look I'm agreeing again) and I'm not sure why anyone would think engine breaking came into it, coast down to me means powerless so I assumed they bunged it neutral. I know doing this in neutral would again remove parts from the drive line but I never introduced engine breaking into that discussion. Now reading what they said is reasonably correct, but I would worry why they never spotted this kind of stuff beforehand or during the test itself ...or more importantly the owner. You and I can tell if you've got a partially seized caliper but not half the folk I know. Again, I thought I'd mentioned innacuracies rather than absolute values. Hmm, coast down losses vs acceleration. Jury's out on that one, the two are linked in an ideal world but I agree I'm not sure what the relationship would be. A coast down loss (out of gear of course) will be there under acceleration but totally distorted I guess asd there are different loads applied to bearings etc. I have to say, that I can't see photobucket stuff so Nik's last dyno sheet is summed up by yourself. There are 2 questions I'd ask: How accurate are dynos of any kind -and this is a separate issue? Assuming RWHP only, personally on a 200'ish BHP engine, on 2 dyno runs I personally wouldn't be surprised to see between 3 and 5Bhp difference. That works out something like 1.5-2.5% difference. I'm pretty sceptical on the actual accuracy of measurements generally from the engineering work I've done so far. I'm really nervous about accepting figures of this sort as I'm sure it's clear that repeatability and accuracy are 2 different things. When I saw Nik's dyno sheet the other month we compared and I believe the comment was passed regarding mods and Bhp increases that he had spent >>>> more money and got a return in the order of something that I'd have written off as a measuring accuacy (sorry Nik). When I do this sort of "calibration" through work I'd immediately scrutinise a) the period when the equipment was last calibrated and b) the calibration method. I'm still amazed how folk continue to issue accuracies on their equipment geater than the calibration method in the first place!!!! My second question relates to the dyno centre, not the dyno. or the method. I wasn't impressed with that centre and as far as I can establish the majority of folk I've spoken to who have used them aren't either. I won't get into why as it's too easy to publically flame someone then get a legal letter through the door. I fully agree with you regarding Nik's figures and adds to my su****ions. There are of course folk who are perfectly happy. Nuff said.