Cq20v RE2400

[hibby]

Are you guys suggesting the Flywheel figures are maybe a bit high?

I had doubts about a few results on the day. My first run also came back at 249 bhp but the plot was away to hell and they made excuses about the tolerances or some cack and that they had fixed the problem. An a6 ran after me and got expected figures then an a5 that was quite a bit over expected figures.

Here is her dyno results








I notice that the difference in Flywheel figures and wheel figures are a different % on each run. How do they calculate this?

[stiglet]

I've never really understood how the dyno calculates fly figures. From what i can tell, it simply measures the wheel power on the power run, then measures the losses on the coastdown run. However, on the coastdown run the engine isn't applying a force to the drivetrain, so you are simply just measuring the resistance in the bearings, cv joints, etc, which means nothing i'm sure. When the engine is applying full torque the resistance in the drivetrain would be higher just because more force means more friction surely?

Unless the dyno software extrapolates assuming a linear force increase or something?

Pointless really though, your car is either faster or slower than a standard 20v, if you reckon it's faster then it's more powerful, simple as.

[hibby]

It is faster I reckon. On a motorway run alongside my mate in a Vento VR6 we reckon I just had the edge.

And the figures seemed to coincide with the claimed figures.

The way the drivetrain losses are calculated make sense, a faulty bearing or binding caliper or possibly other faults could possibly push this percentage up I guess. I have new hubs etc to put on so that should sort that out a bit.

[Error404]

Nice car mate, something a bit different
Throttle bodies!! :mischeif:

[stiglet]

Does look like a very nice example, would love to see it at Combe (hint hint )

[stiglet]

Ok so i was basicly wrong, this site claims that the torque related losses are minimal compared to speed related losses. So basicly 2 cars with identical transmissions will loose a near identical amount of power regardless of the engine power.

Does this sound right? Makes sense since yourself and Mr Casey are both losing nigh on 60hp through near identical transmissions.

[EspenW]

Ok so i was basicly wrong, this site claims that the torque related losses are minimal compared to speed related losses. So basicly 2 cars with identical transmissions will loose a near identical amount of power regardless of the engine power.

Does this sound right? Makes sense since yourself and Mr Casey are both losing nigh on 60hp through near identical transmissions.

The load factor is very important. A high power engine will lose more power through the transmission than a low power engine. A transmission is not 100% efficient. Lots of good information to be found on the net about this topic. Relying on coast down losses alone is a highly flawed method.

[EspenW]

Hibby: your numbers for the A5 seems quite correct with a 22-24% drivetrain loss. Impressive engine.

[hibby]

There seems to be too much conflicting info on the net about the drivetrain losses.

What I know for certain is I am having a great time driving the car. And that is what matters the most I guess.

[EspenW]

Tire pressure was spot on?
Sticky caliper, perhaps?

[hibby]

Tyre pressures checked beforehand.

Sticky caliper sounds about right. possibly a dodgy wheel bearing.

[T2Andy]

That A5 is going to be quicker than an s2 was it mapped ,thats a lot of torque

[hibby]

The A5 was supposedly standard but it produced similar figures to an A4 with the same engine that had been mapped.

[S2central.net]

A few observations here...

1. The drivetrain losses do seem strangely high. Tis often a subject of great debate on how best to adjust for this. Different rollers and operators have different behaviour I guess - makes sense to keep using the same rollers and also to focus on power at the wheels instead of flywheel.

2. Does anyone else think those AFR values are a bit lean ? Which is what I would expect I suppose - the engine has increased capacity of air intake thru the mechanical mods yet the ECU is untouched... Relies on the MAF still providing useful information at WOT on air intake, but if its maxxed out then the fuel pulses will be none the wiser and you consequently run leaner than you might like. I'd be expecting AFRs in the 12s for example.

3. Seems very lacking in torque between 3 and 4k which I don't recall as being a characteristic of the 7A (been a long time since I drove one though).

Some ECU tweaking could go to good effect on such a conversion...

[Flat on my back]

From a late 7A fwd.

Hope you can see them ok.

Think my MAF is causing issues...was hoping for nearer 180 with all my mods!