I said the claim that you must run a VAP tune to use a pulley has been disproven. I don't use dishonest vendors. So VAP is out.

You are recommending a tune that will increase peak power, that is not what I want as it will increase peak engine stress which almost certainly shortens life. I want to raise the low parts of the curve, only.

 

 

I am not an expert or a professional, like to consider myself a well informed amateur.

It would seem from my understanding that the ecu calibration whether standard or aftermarket tune doesn't expect any value rather it receives data from sensors.

It receives inputs from MAF value and IAT and MAP and rpm and coolant temperature exhaust lambda and throttle pedal position etc etc it looks up tables to determine outputs of throttle opening, ignition timing fuel injection duration (amount of fuel injected) and other parameters


If the supercharger spins faster it moves more air, extra air flow is measured by MAF.
MAP sensor measures inlet manifold pressure.
IAT sensor allows air density to be adjusted for and timing and fuelling to be altered accordingly in relation to temperature

One output also controls supercharger 'bypass' valve whereas earlier supercharger had this directly controlled by manifold boost / depression pressure.

Happy to be informed about any flaws in my understanding

 

VAP have never claimed this, they have infact stated the opposite that one can use an upper pulley but do not advise it as the factory mapping can only adjust fuelling by so much for additional airflow and though the upper pulley should be fine they do advice tuning as most who do these mods are interesting in gaining top-end power as the V8 has no shortage of response and low down torque.

In the V8S you'd be better off with more top-end power rather than more torque as your severely traction limited.

 

​​​​​​A severe loss of rear end traction sounds GREAT to me!!

 

OK, but you will go slower, you may even crash.

 

 

I think that's about right. I want low end torque without increasing peak torque. That way the engine is always under peak limits but you have lots more area under the torque curve. That's the sweet spot for me. 30-40 lbft from a pulley alone is the full benefit of "the tune" down low, meaning it's all pulley down there anyway.

And why is it that the VAP plus pulley supposed dyno intersects stock down low? Shouldn't faster pulley gearing increase sc boost at all RPM?

 

Your on the right track and in the olden days like say on a Peugeot 306HDI from the 90's you could simply turn up the boost mechanically and gain like 50HP, the car would run fine, no issues as like you say the sensors in the car would read new readings and fuelling would adjust.

On a modern day car there are tables upon tables of data for all areas of mapping, spark, cam values, IAT, fuelling, lambda, knock, throttle maps, DBW, global settings and lots of other values. The factory map will be reading data from MAF, IAT, Knock, O2 sensors etc and making necessary adjustments however the tables have a min/max values and as such if you move below or beyond or a reading stops reading that is when the ECU throws a cel. They do this to limit power purposely but they also do it to be emission legal in all regions and so the car will run even on lowest grade fuels without detonation.

When a car is remapped they generally increase the upper limits within reason, of course they still need to keep knock sensors active for safety.

For a novice tuner on a modern day car easy power can come from increasing boost limit, adjusting fuelling, adjusting spark for higher RON fuels etc and keeping knock sensors fully active for safety, but of course if the stock timing is 18 degrees, you'd not try to dial in 25 degrees as you'd get detonation, but you'd just add 1-2 degrees at a time either globally or just at set RPM points, of course you should always get your car tuned by an experience tuner as they will have done all the research and they will also be adjusting torque demand tables, cam tables to not only make best power throughout entire rev band but also safely and they can also give you throttle mapping to your desire via tweaking drive by wire system and throttle maps.

The Jaguar factory map is based on worse case scenario, really poor fuel, really high IAT and very strict emissions. So a tuner can easily make more power just by simply tuning for good fuel and not having to worry so much about emissions, in case of our cars by also increasing the PSI limit to stop boost been bled off.

I am no expert but have a rough idea from tuning with HP tuners and know several professional tuners who have shared how they do things and how factory maps work.

 

With tune you will gain even more down low due to further advanced spark timing and better fuelling.

 

And any tuner or individual that recommends more peak power than a owner is comfortable with should be ignored. Man oh man, is that dumb.

 

Yep; agreed on all counts.

Frankly an upper pulley alone is a waste of time for 0 peak hp and a very small midrange boost for $195 plus install; the tune at $995 for 100+ hp is a bargain and VAP is the only vendor I trust


Dave

 

Paul 59 a thank you for your in-depth analysis of my post.


From Gibbo's post it would seem that if engine sensors supply out of range (or unexpected or unallowed) values to the ECU it will throw a CEL because it cannot calculate or look up the correct response to the inputs.

Gibbo is this correct?

 

I don't think a 30-40 lbft flattening of the torque curve is small at all. There is more to speed than a peak increase at redline. The pulley seems like a much better option since it works down low, always under the manuafacture's peak design stress limit, and a tune minus pulley can't generate more boost until the SC is beyond peak anyway.

If you think the potential to blow up your engine, and the certainty of shortened life, is the only way to go, I disagree. Raising the low end torque curve without exceeding peak design limits is smarter IMO. Will VAP guaranty full reimbursement for short and long term engine damage? Lots of tuners warranty their tune in full. If VAP does not, they are telling you the tune is risky.

 

I think we have already determined the pulley alone works fine, like every other modern SC'd car. That was the original question. No upsell required.

 

You seem to be confused about peak power. If you increase power at lower RPM, you are increasing stress on the engine. Creating 400 ft lbs of torque at 2000 RPM is more stressful than creating 400 ft lbs at 4000 rpm - cylinder pressures are higher, stresses on rings, connecting rods and bearings is higher, etc.

Think about it. Do you think Jaguar just guessed on pulley sizes? I'd be willing to bet lots of testing went into determining the correct sizes of the pulley to achieve power and safety objectives. If you prefer to just alter the pulley with no compensating alterations, go for it!

 

Nope, I'm 100% certain the jag tune is optimum for engine power vs engine life. Tuning will, without a doubt, shorten engine life. There is no free lunch.

Given the options, a pulley only is the best way to go IMO, since it will raise/flatten the torque curve without ever exceeding peak design stress. This will provide 30-40 ftlb of low end, or virtually all of the pulley+tune low end gain, without regular, substantial OEM design limit exceedences at high rpm. That's exactly what I want.

 

Actually you show your limited experience.
Torque bends rods, not HP.
With the smaller upper pulley you will hit peak power sooner, around 5000rpm, so the next 1500rpm will be flat, will make the car feel not as exciting and one could say if you want a limited and torquier power band, maybe you should of purchased a diesel powered car.
The manufacturer (Jaguar) designed the AJ133 engine and supercharger to be capable of as high as 700PS without any additional stress or reduction in life, in short its an over-engineered car and ran well below its capability and capacity on a V8S, proven by other models running as much as 100PS more with the same hardware from the factory with the same warranty.

Tuners who warranty their tunes, tend to charge extra, VAP have no single failure and why should they their tune gives a max of 605HP, they will also offer to put the Project 8 tune on your car which is about 590HP which is a Jaguar tune, designed for the hardware by the manufacturer that they sell and mass produce.

This is a service that VAP offer, you can request either their tune or the Jaguar Project 8 600PS tune, so as for safety there is no safer than the latter.

Stop dissing VAP, they offer quality products, that they spend years perfecting and great customer service, there are zero reports of failures down to tuning VAP or not.

 

Jag have 4 tunes for this car, V8S, V8R, SVR and P8, hardware is identical across all 4 and they are all optimum for engine power vs engine life. You can buy the Project 8 tune from VAP, so yes a free lunch except from the tune cost, but a nice easy 100HP gain with a much more power and torque throughout the curve.

Pulley is not the only way to go, its an option, the car won't be optimum for engine power vs engine life as its a configuration Jaguar never intended.

 

the tune does much more than just give you a peak increase at redline and as others have noted the car is already traction challenged at lower speeds. As far as exceeding peak design limits, as Gibbo mentioned; ALL AJ133 F type motors are identical except software whether they are the 488/495hp version, the 550ps version, or the SVR or P7's 575ps version so if you're worried about "exceeding peak design limits" run the 575hp tune and be happy in the knowledge that your V8S is running the exact same output levels as those aforemented " factory tuned" F types. I'll tell you something else; if you're worried about warranties and engine damage coverage, you'd better not do either the tune OR the pulley. ;-)

Dave