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Enjoyed very much

That this car gives out 400 rw bhp on the dyno is actually very, very good, considering this (DB7 V12 vantage, with 20% loss):

http://www.youtube.com/watch?v=a78bCMi_KHY

I would have thought the car would peak at ~380 rw bhp at most., as I believe the avg for Front/rear config/ high performance is 15-20 ish. This is more like a very efficient Front/front car.

More amazingly I have read about (fairly new) DB9s peaking around 405-ish, despite the composite drive shaft.

I would say that this is a very well-preserved example, maybe with an engine that holds torque better than the average (again, no two engines are alike)

Also the twin plate clutch (special on the GT) would have helped a bit....

I still doubt that that is enough measure to get only ~ 10% drive train loss, would there be anything else?

Also, would you happen to know the torque percentage (from peak torque) it delivered at the low revs (1500-2500 RPM)?
 

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Discussion Starter #3
I have to admit my car doesn't hang about and I can easily induce wheel spin in the first 4 gears, a high RPM gear change above 100mph will spin the wheels, so the engine is certainly producing a good amount of torque still.

The details I look for on Dyno runs are the things most people know little about, and that is Barometric Pressure, Ambient Air Temp, Intake Air Temp, Ramp Ratios, Inertia Ratios etc.

Any one of these can be tweaked to give higher or lower readings.

Also on the video you posted the 429 figure is their own calculated engine power and not power at the rear wheels. They have a Barometric reading of 1006 which means it's well above sea level, if we knew the location we could find out if this figure is way out or somewhere safe. I also noted there was no temperature reading at all with the result displaying 0.0 degrees, this alone is enough to make the results only fit for the bin.

I like to see results that are displaying all the required data to allow for a like-for-like run.

Air temp is a very common failing for most Dyno runs as if that's wrong then you may as well forget it.

I have seen Dyno runs with temp readings swinging by 60 degrees, this affects the multiplier equations used by the Dyno software when working out final power readings.

Another thing I learned about is different Dyno makes use different variables which effectively give out different readings, so you need to use the same type of dyno to be able to compare, unless you know the exact ratios to adjust figures.

These affect the in-built correction Factors.

364.99 wheel power would be about where this V12 is performing, that is if the temp and other input data is reliable which I have my doubts over.

Plus coming from a Tuning shop I would imagine they tweak the figures in their favour slightly as has been found at some others in the past. I know of two tuners who have a switch wired into the Dyno so they can instantly alter the air temp and falsely increase figures.

I imagine for the whole V12 engine range including the Vantage and GT models you might see a range of engine powers between 405hp to 450hp, then you have the tolerances in the drive train, losses of between 10% - 20%.

I was expecting somewhere between 380 - 400 form my GT, to hit my upper expectations was fantastic and might be due to having a good engine mated with a good transmission.. some unfortunate Aston owners might get a lesser engine mated to a lesser transmission and suffer a 20% drop in power, however for most owners this would not be noticed.

There is certainly room for debate on the whole Dyno subject ;-)
 

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I have to admit my car doesn't hang about and I can easily induce wheel spin in the first 4 gears, a high RPM gear change above 100mph will spin the wheels, so the engine is certainly producing a good amount of torque still.

The details I look for on Dyno runs are the things most people know little about, and that is Barometric Pressure, Ambient Air Temp, Intake Air Temp, Ramp Ratios, Inertia Ratios etc.

Any one of these can be tweaked to give higher or lower readings.

Also on the video you posted the 429 figure is their own calculated engine power and not power at the rear wheels. They have a Barometric reading of 1006 which means it's well above sea level, if we knew the location we could find out if this figure is way out or somewhere safe. I also noted there was no temperature reading at all with the result displaying 0.0 degrees, this alone is enough to make the results only fit for the bin.
I might not have given you the right video... let me check...
Actually the 429-chipped car is a different video that is related, but not the one I linked to
The one I posted is "Aston Martin DB7 Vantage Dyno" by jimfrentress


I realize that there is a lot of ambient variables that would paly a role in the output figures apart form the specific engine/torque.

I believe they assumed the 420bhp/ 410 torque form the average factory ratings (which has potential to vary to certain degrees), however they got only 340 bhp/ 330 ft torque peak out of 2 dyno runs.

This was done in Seattle, Washington, so the maximum elevation there is 520 feet, which makes only ~ 2 kPa maximum pressure difference between sea level and there (I doubt that will cause the engine to strave). The specific weather high/low front might have played a role though. But then, the car in your video had a fan in front of it I believe (and that woud help bring the figures up/ simulate dynamic testing), not sure if they had a similar setup for the video I posted.

It is also not known how much the car was used or how it was used in my video.

I would say that these results are comparable to a degree.
 

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Discussion Starter #5
I understand fans of some form should always be used on a Dyno as it provides air movement for cooling more than anything else.

Also it simulates the car in motion, cars tend to create their power curves whilst being driven and this would mean air is being forced through the front vents.

DB7 V12's put a lot of heat out and running them under load without adequate air flow is not a good idea, even if for a short time.

It also helps to stabilize the intake air temp, so you know it's sucking in fresh air as opposed to heated air from the engine bay.


This leads to the biggest problem with all Dyno readings.. uniformed testing standards and comparability.

If all runs were done by the book then we could compare them all, however few are done correctly.

And we all know in order to extract real HP from an engine you're going to need head work and valve gear, fuel pressure, induction, exhaust and finally after all that has been done then you get it re-mapped.

Re-mapping offers little to no gains unless the engine was de-tuned at the factory and it already has the required tuning.

I know the difference between the GT engine and the Vanquish engine was ECU mapping and Camshafts / Valve gear.

The Early Vanq's only offered 470HP before going up to 510HP, so if a GT engine requires ECU's and Camshafts to gain an extra 35HP, how can these tuners get that with a simple re-map?

You cannot substitute Camshafts and valve gear for a simple re-map, unless of course you tweak the Dyno results ;-)
 

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Discussion Starter #7
Good choice all the same, the DB9 is technically the better car, although not as unique.

I was the other way around, I was looking for a DB9 originally before I stumbled by chance onto the GT :)
 
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