Power band
#1
#4
With the stock tune I could feel that a fixed pedal position would accelerate, then step up in power, almost like a turbocharger than needed to spool up before giving full boost. I described it as the system needing time to decide I really meant it, since superchargers don't have "turbo lag." I think the factory limited maximum available power until rpm and throttle position values were exceeded. To expand on that, I think that, for example, at 2000rpm and 100% throttle (really, pedal position) the maximum power the engine could provide was never delivered. What the engine can really do is not so artificially limited with the VAP tune. Since the engine can provide quite a bit, the pedal can be more sensitive, but it one can adapt.
#6
With the stock tune I could feel that a fixed pedal position would accelerate, then step up in power, almost like a turbocharger than needed to spool up before giving full boost. I described it as the system needing time to decide I really meant it, since superchargers don't have "turbo lag." I think the factory limited maximum available power until rpm and throttle position values were exceeded. To expand on that, I think that, for example, at 2000rpm and 100% throttle (really, pedal position) the maximum power the engine could provide was never delivered. What the engine can really do is not so artificially limited with the VAP tune. Since the engine can provide quite a bit, the pedal can be more sensitive, but it one can adapt.
#7
In other words maximum torque occurs at 2500rpm and is maintained ar the same level until 5500 rpm
Trending Topics
#10
#11
Yeah some quarter mile runs would certainly show the truer picture.
#12
Power = torque / 5250
when torque is measured ft lbf
Hence power in bhp always equal to torque (ft lbf) at 5250 rpm, irrespective of engine.
VAP tune shown makes more torque and hence power at lower rpm. At higher revs the graph shows still higher torque and hence power, however on VAP tune shown the torque falls off at a faster rate (greater slope on graph) and hence power drops more rapidly but it's still higher torque and power than standard.
I am not an expert or a professional, my understanding is the likely cause for high rpm torque drop is often related to a decline in airflow / volumetric efficiency.
Restrictions can be caused by exhaust flow, perhaps cast log style manifold limits flow and or inlet restrictions from valve area and lift, inlet manifold and supercharger airflow limitation, also not to exclude supercharger efficiency dropping and reduced inlet air density from lack of effective intercooling.
Put simply if you can get an engine to maintain high volumetric efficiency wirh dense colder air at high revs and adequate fuel flow and combustion efficiency then it will maintain or increase torque and power
Last edited by Paul_59; 07-11-2018 at 06:12 PM.
The following users liked this post:
DPelletier (07-12-2018)
#13
What Paul_59 said. The VAP tune hp, even though it is dropping off, is still more than the OEM tune. The value in the VAP tune is that the power and torque comes on far more quickly in addition to having greater peak values. The top end (>6000 rpm) limit is a function of the SC limitations. No tune will overcome that.
Last edited by Unhingd; 07-11-2018 at 08:42 AM.
The following users liked this post:
SinF (07-11-2018)
#14
One way to solve this is to get a bigger supercharger.
Another way to attempt to address this is to port and polish your existing supercharger.
#15
I don't think even dual pulleys would spin the V8 supercharger (TVS 1900) close to its max RPM. Likely the weird TQ towards the end of the RPM band could be due to less than perfect cooling (likely both the dyno shop's cooling and how tightly everything is packed in the F-Type's engine bay).
Don't forget you'd need to be simulating 120-130 mph worth of air flow to get an accurate indication of how the engine would be performing in a real life scenario.
Don't forget you'd need to be simulating 120-130 mph worth of air flow to get an accurate indication of how the engine would be performing in a real life scenario.
#16
My understanding is that with a tune and pulleys you will reach maximum supercharger efficiency earlier, hence a drop off. I suspect that if you were to map stock tune to 9000 rpm (!will likely result in engine damage!) you would see similar drop-off due to supercharger past redline.
One way to solve this is to get a bigger supercharger.
Another way to attempt to address this is to port and polish your existing supercharger.
One way to solve this is to get a bigger supercharger.
Another way to attempt to address this is to port and polish your existing supercharger.
If my bank balance ever matches my dreams which is unlikely given I have big dreams, then I would go the route of a larger supercharger
. The TVS 2300 would obviously flow more air but the TVS 2650 maybe even better not just due to its increased capacity but it's a newer generation with improvement in efficiency over TVS 2300, consequently it's claimed to flow more air and require less power to drive it than TVS 2300.
Obviously we are talking serious investment, in addition to an estimated £10000 for a custom TVS 2650 there would need to be serious upgrade to ZF 8HP70 auto transmission which is very close to its rated torque limit of 700 Nm even in standard tune, then there's prop shaft, diff and half shafts to upgrade
#17
Agreed, even if supercharger airflow is sufficient at higher rpm, operating outside peak efficiency will lead to increased heat into inlet air, this results in lowering of air density and hence reduced volumetric efficiency.
If my bank balance ever matches my dreams which is unlikely given I have big dreams, then I would go the route of a larger supercharger
. The TVS 2300 would obviously flow more air but the TVS 2650 maybe even better not just due to its increased capacity but it's a newer generation with improvement in efficiency over TVS 2300, consequently it's claimed to flow more air and require less power to drive it than TVS 2300.
Obviously we are talking serious investment, in addition to an estimated £10000 for a custom TVS 2650 there would need to be serious upgrade to ZF 8HP70 auto transmission which is very close to its rated torque limit of 700 Nm even in standard tune, then there's prop shaft, diff and half shafts to upgrade
If my bank balance ever matches my dreams which is unlikely given I have big dreams, then I would go the route of a larger supercharger
. The TVS 2300 would obviously flow more air but the TVS 2650 maybe even better not just due to its increased capacity but it's a newer generation with improvement in efficiency over TVS 2300, consequently it's claimed to flow more air and require less power to drive it than TVS 2300.
Obviously we are talking serious investment, in addition to an estimated £10000 for a custom TVS 2650 there would need to be serious upgrade to ZF 8HP70 auto transmission which is very close to its rated torque limit of 700 Nm even in standard tune, then there's prop shaft, diff and half shafts to upgrade
#18
I didn't realise that, I assumed that multiple variants of 8HP transmission such as 8HP75 with torque rating of 750 Nm and 8HP90 and 8HP95 both rated to 950 Nm were an indication that the ZF 8 speed transmission is available in different variants according to application and torque
Last edited by Paul_59; 07-11-2018 at 01:15 PM.
#19
#20
Cheers,
Dave