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Power band

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Old 07-09-2018, 09:14 PM
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Default Power band

anyone know if the vap tune and or pulley mods for the f type r alters the power delivery such that peak torque occurs earlier in the power band? My understanding is that stock, peak torque doesnít occur until 3500rpm.
 
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Old 07-09-2018, 11:20 PM
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I remember Space Ghost having power bands.

For the car, there are those with dyno charts, but I never dyno'd my car, either before or after.
 
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Old 07-09-2018, 11:50 PM
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Thx for the reply. Did you notice more power at lower rpm while driving and what mods did u do?
 
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Old 07-10-2018, 01:17 AM
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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.
 
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Old 07-10-2018, 03:42 AM
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Originally Posted by mominayal View Post
anyone know if the vap tune and or pulley mods for the f type r alters the power delivery such that peak torque occurs earlier in the power band? My understanding is that stock, peak torque doesn’t occur until 3500rpm.
VAP has Dyno charts on their website. The crank pulley appears to shift the torque curve lower.
 
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Old 07-10-2018, 08:37 AM
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Originally Posted by lizzardo View Post
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.
I find it almost impossible to put down full power in first gear (MT gearbox). You just end up spinning rear wheels, and this is with LSD and MP4S tires. If you are *really* fast on a perfectly flat road, you might hit WOT by 5500 rpm in first gear. From there on, if you find yourself under 3000 rpm you are not doing shifting right.
 
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Old 07-10-2018, 03:03 PM
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Originally Posted by mominayal View Post
anyone know if the vap tune and or pulley mods for the f type r alters the power delivery such that peak torque occurs earlier in the power band? My understanding is that stock, peak torque doesnít occur until 3500rpm.
Cant comment on VAP tune, my understanding of V8 output is the torque curve is flat from 2500rpm to 5500rpm.
In other words maximum torque occurs at 2500rpm and is maintained ar the same level until 5500 rpm
 
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Old 07-10-2018, 04:31 PM
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Before and after VAP tune and crank pulley
 
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Old 07-10-2018, 04:35 PM
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That VAP map looks terrible past 5500rpm, power drops off big time, whereas stock map keeps making power, they need to improve that!
 
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Old 07-10-2018, 04:48 PM
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No one was quite sure what happened there. Certainly not something you can feel in every day driving or even pushing it hard. Always feels like it wants to go faster but I have not yet put it on the track. We'll see then for sure.
 
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Old 07-11-2018, 04:31 AM
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Originally Posted by Andrew W View Post
No one was quite sure what happened there. Certainly not something you can feel in every day driving or even pushing it hard. Always feels like it wants to go faster but I have not yet put it on the track. We'll see then for sure.
Yeah some quarter mile runs would certainly show the truer picture.
 
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Old 07-11-2018, 08:01 AM
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Originally Posted by Andrew W View Post


Before and after VAP tune and crank pulley
Originally Posted by Gibbo205 View Post
That VAP map looks terrible past 5500rpm, power drops off big time, whereas stock map keeps making power, they need to improve that!
I suspect many car enthusiasts know that torque and power are linked.
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 07:12 PM.
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Old 07-11-2018, 09:40 AM
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Originally Posted by Gibbo205 View Post
That VAP map looks terrible past 5500rpm, power drops off big time, whereas stock map keeps making power, they need to improve that!
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.
 

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Old 07-11-2018, 10:09 AM
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Originally Posted by Paul_59 View Post
I am not an expert or a professional, my understanding is the likely cause for high rpm torque drop is often related to decline in airflow / volumetric efficiency.
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.
 
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Old 07-11-2018, 12:48 PM
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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.
 
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Old 07-11-2018, 01:40 PM
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Originally Posted by SinF View Post
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.
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
 
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Old 07-11-2018, 01:51 PM
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Originally Posted by Paul_59 View Post
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
Donít worry about the tranny. That transmission has seen substantially more torque in other applications without failure.
 
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Old 07-11-2018, 02:11 PM
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Originally Posted by Unhingd View Post

Donít worry about the tranny. That transmission has seen substantially more torque in other applications without failure.
ZF 8HP range


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 02:15 PM.
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Old 07-12-2018, 09:15 AM
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What about other components, like transfer case, differential, and even drive shaft?

I have seen sheared driveshafts on tuned cars after careless launches. It can get really ugly if it fails at the front and turns the car at speed into a plow/anchor.
 
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Old 07-12-2018, 01:30 PM
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Originally Posted by SinF View Post
What about other components, like transfer case, differential, and even drive shaft?

I have seen sheared driveshafts on tuned cars after careless launches. It can get really ugly if it fails at the front and turns the car at speed into a plow/anchor.
I don't have a transfer case ;-) ......the "fuse" in the driveline system is the tires/traction, not engine hp. With DOT tires you are unlikely to risk damage to the driveline and they are certainly designed with a safety margin in mind......that said, if you use the car every weekend at the dragstrip, it will wear those components out sooner than if it was only driven to church on every third Sunday!

Cheers,
Dave

 

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