Rolling Road graph interpretation.
Discussion
Here is a graph from a 1996 Griffith 500 rolling road power/torque run. No exhaust gas analysis was done.
The car has done about 53k miles and has had no engine repairs or upgrades.
The air filter, plugs, plug extenders, HT leads, distributor cap, and rotor arm were all renewed 3k miles ago.
Two heavy chaps were sat on the boot to ensure no wheelspin, which may account for some of the indicated power losses.
I'd be interested to hear the views of those experienced in these matters, thanks.
The car has done about 53k miles and has had no engine repairs or upgrades.
The air filter, plugs, plug extenders, HT leads, distributor cap, and rotor arm were all renewed 3k miles ago.
Two heavy chaps were sat on the boot to ensure no wheelspin, which may account for some of the indicated power losses.
I'd be interested to hear the views of those experienced in these matters, thanks.
I'm no expert but the power appears to be lowish and the torque looks a little 'peaky' - they're usually wider. I'm sure someone who knows about these things will be along shortly.
ETA::Odd, the graphs should cross at 5252 RPM but they don't - and they cross twice. Very spooky. Doesn't look right to me.
ETA::Odd, the graphs should cross at 5252 RPM but they don't - and they cross twice. Very spooky. Doesn't look right to me.
Edited by LordGrover on Friday 10th July 20:37
I'm no expert, but here's my 2p worth........
Interesting; would the gear the rolling road is sampled in make a significant difference?
Thought it was mostly done using 4th? The OP's looks like it was in 5th.
225hp is a little low for a 5ltr IMHO & the way the power drops off isn't great either.
Rolling roads vary.Put it on the rollers at the GROWL & compare like with like.
BUT...
How does it feel on the road, are you happy with the way it drives? That's the 64 million dollar question.
Interesting; would the gear the rolling road is sampled in make a significant difference?
Thought it was mostly done using 4th? The OP's looks like it was in 5th.
225hp is a little low for a 5ltr IMHO & the way the power drops off isn't great either.
Rolling roads vary.Put it on the rollers at the GROWL & compare like with like.
BUT...
How does it feel on the road, are you happy with the way it drives? That's the 64 million dollar question.
Edited by griffdude on Friday 10th July 22:36
That looks nothing like any RR graph I've ever seen. The way I read it, unless I'm missing something is that peak torque is produced at 3000 RPM and then falls away to oblivion (with a little twitch at 4k) instead of being smoother and flatter. The power curve climbs steadily but seems to be a bit poor on ultimate power. Breathing issues?
This is the one I got with mine, it's producing a bit less at the moment 'cos of over-fueling issues which are probably down to the AFM. I'll get that sorted with one or two other items when funds allow
This is the one I got with mine, it's producing a bit less at the moment 'cos of over-fueling issues which are probably down to the AFM. I'll get that sorted with one or two other items when funds allow
Edited by V8 GRF on Friday 10th July 22:31
V8 GRF said:
Yea but even allowing for the scale the torque still drops away very steeply.
The curve is a bit of a mess. Usually the data is smoothed out. The steep bit from 4000 to 4500 is a 10% drop. I still think this looks ok IMO. I bet if the power run was repeated several times this sharp drop would smooth out.I do agree that the power is very low and the 4000 point seems to show an anomoly. Best bet is to run it again on the rollers and see if the curve is the same.
Worn cam?
Edited by Chimjunkie on Saturday 11th July 02:33
The place this RR is at mostly do Minis and rumour has it that the RR struggles at higher torque levels. I guess 275FtLb is rather a lot for a Mini. As this car is reasonably competitive for a standard production car on the Hills I think it is the RR that has to be in doubt not the engine
Have just noticed something else about your plot Andrew. It says 224 @ 151Mph. Unless you have odd ratios in the new gearbox that must be 5th gear. Normally a power run seems to be done in 4th. I always assumed that was because 4th is 1:1 gearing. Don’t really understand the implication of using a different gear but presumably it could have an effect on the roll down loss correction. If it was done in 5th I would think it unlikely you would have suffered wheel spin and would not have needed two large chaps sat on the back. Just to contradict the 4th gear argument it that it looks like the Austec one was done in 3rd, the Emerald one looks like 4th to me. Hopefully an expert will be along soon to explain if the gear used is important.
Yes I think you are right, if I remember correctly it was 4th gear at Emerald. Speed was 119mph at 5560 rpm giving 254.4 bhp and 273.3 lbft torque. I'm afraid the graph displays smaller than I expected it to. The graph is same scale (left axis) for both bhp and torque, the right axis is AFR (air fuel ratio)which is the horizontal(ish) line lower down.
Nick
Nick
As a result of abject boredom this afternoon resulting from being trapped by road closures for local carnival and weather too grim to go sailing, I plotted the various charts in an Excel chart using the same scale. Doesn't half make it all much better to follow. Couldn't read V8's torque data as it was too squished so only showing the bhp for that chart.
Nick
Nick
Edited by sunwharf on Saturday 11th July 23:38
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