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Yet another run up the A3 and M25 from Portsmouth yesterday with the Sprint Booster set for the majority of the journey at Red5. This was quite satisfactory and no problems were noted. I tried up to Red8 but experienced an engine cough with the engine check light making an appearance.(SEE MY FINAL PARAGRAPHS IN THIS POSTING)

A fuel stop below Guildford allowed me to clear the faulting with the iCarsoft unit. "No communication with the ECU", flagged up as explanation. Experience of the XJR electronics to date suggested a pressure leak from the tube attached to the SC pressure manifold which links to the by-pass actuator as a issue. I discounted that as the tube had recently been replaced and was unlikely to have been blown off the pressure manifold stub pipe. With the Sprint Booster operating at very high Red8 setting, I suspected that this could be an "out of limits" issue caused by high Red level software within the Booster being at that point, unacceptable and un-familiar to the ECU and thus generating a "fail judgement". So I re-fueled, cancelled the fault on the Powertrain Control Module and lowered the Red level setting to 5. Although I attempted to further provoke a re-occurance of the faulting, the Booster performed well and no further glitches occured.

This morning, PTJS1 joined me at the former RAF Kenley airfield for a photo shoot, a comparison driving session of our two X350`s and some testing of the Sprint Booster. Paul wanted to drive my car with the unit fitted and we both wanted to see what occured when the Booster was activated from its lowest setting to the highest. The tests were conducted with the ignition and dash lights showing but without the engine running except for one occasion when we checked standard idle speed with the engine running. The results make interesting reading. I hope Paul will correct me if I`ve produced any errors here in the our findings or results description below.

Our tests were conducted using an Android phone with the Torque Pro app activated to display throttle opening as a percentage between 0-100%. At idle, the percentage opening of the throttle plate within the throttle body throat registered as 3.5% at idle condition. That equated to 652rpm with the engine running. Note that regardless of whether the Booster was switched off (ie allowing the car to run on its inbuilt software program with Viezu up-rated performance modification) or if either the Booster Green or Red programs were operated, this idle speed and 3.5% opening remained consistant throughout our tests. With the Booster switched off, we noted that we could watch the throttle percentage opening increase from the 3.5% idle condition, rise to a full 100% opening with throttle pedal depressed fully to the floor.

We then moved to a second test. We placed a block under the accelerator pedal to enable us to establish a base line fixed throttle opening which would be consistent throughout this test. With the block in place and the pedal depressed to contact the block, this gave us an 18.8% opening, with the Booster switched off. My foot stayed permanently on the pedal throughout this next part of the investigation. Switching the Booster to Green9 immediately displayed a 43.1% throttle opening. ie just over twice the opening percentage found from the slightly modified ECU program permanently written onto the internal Powertrain Module. We then switched to the "race" Red mode. Whilst we did not record percentage readings from Red1-4, we found that Red5 gave a 54.5% percentage opening. Red1-3 gave percentage openings that were less than Green9. Only when Red4 was selected did we start again to see percentages rise to above the Green9 again.

Red6 gave 62.7%, with Red7 giving 69.8%. Red8 and 9 gave no further percentage increases BUT having removed the block from under the accelerator and pushed the pedal to the floor, caused a total failure of the engine management system! Quite clearly the Powertrain module and software could not comprehend the throttle pedal signal, caused a "fail judgement" and shut down ALL throttle pedal response, faulting the DSC, ABS and electronic handbrake. We cleared the faults issue with my iCarsoft930i and re-instated the failed systems.

Essentially then, we can see that by activating Red7 nearly FOUR TIMES the throttle plate opening percentage occurs. It is no wonder that the throttle in service becomes extremely touchy when set to Red7 and above.

Red8 and 9 in practice do not generate any further percentage opening figures and there is no point in using those two programes with XJR/XKR or 4.2XFR models fitted with Denso ECU Powertrain modules. What we do know is that depressing the throttle pedal fully to the floor on my XJR with either Red7,8 or 9 is likely to cause either a glitch when driving or most significantly generate a total "fail judgement" as defined in the paragraph immediately above. So I must issue this precautionary advice. DO NOT USE Red 7,8 or 9 WHEN DRIVING THE CAR ON THE ROAD. SHOULD FAILURE OCCUR WHILST USING THESE THREE PROGRAMS, YOU COULD LOOSE TOTAL THROTTLE PEDAL CONTROL!!!!!!!!! Please heed this warning. Today we deliberately provoked and prooved twice in real time that using Red9 under hard acceleration does cause this complete and possibly dangerous failure. I for one will not ever be using programs above Red7-9 again and will be contacting Telematica for a further discussion. Used below Red7, the unit displays no issues at all.

Returning to the engine "cough" I experienced yesterday, it is likely that I came very near to a total failure limit by using Red8 as I was at the time. I`ll not be doing that again!

So a little more has been learned. My thanks to Paul for hooking up with me at Kenley and for helping make this summary possible. No doubt Paul will pass comment shortly.

Mike

As Mike has detailed, we had been trying to think of a way of really showing how the Sprint Booster worked. We knew that it used a voltage signal amplifier to change the mapping of how throttle pedal movement travel was translated by the engine ecu into actual throttle plate opening. From my knowledge of the functionality of the Torque Pro Smartphone App we surmised that we could physically see how the different settings of the Sprint Booster changed the voltage map of the throttle potentiometer output signal enabling much wider throttle plate openings for the same pedal travel.

Ideally, we would like to see full graphs of throttle pedal travel to throttle plate opening for each setting of the Sprint Booster. It may be that we can use a datalogger to show this but in the meantime we can at least show how, for a given throttle pedal travel, the Sprint Booster multiplies the voltage signal to significantly increase throttle plate opening.

The initial literature on the product implied that the opening was increased by a ratio of about 1.3. However, our tests show that, depending on the setting, the ratios can be multiplied significantly higher than that. This helps us to understand how the Sprint Booster can have such a marked change on the throttle opening and corresponding acceleration improvement.

Mike has detailed the figures in the post above and the following photos show this. As explained, we used a block to limit the pedal travel and then set the pedal with the Sprint Booster turned off such that the throttle plate was open at 18.8%
We then turned on the Sprint Booster to Green 9 (a mid-range setting). With the pedal still at the same position, the throttle plate jumped to 43.1% open
As we raised the settings of the Sprint Booster, the throttle plate opened further to a max of 69.8%, a huge increase from the 18.8% opening for that normal pedal travel.
This fairly simple test enables us to see how a very different driving characteristic can be achieved using the Sprint Booster. One can understand how 100% throttle opening could be achievable at say 50% pedal travel or even less.

Having now driven Mike's car, I can vouch for the significant change. It is really not possible to emulate this change just by mashing one's foot to the floor all the time. The ability to generate really significant throttle openings with small pedal movements is a fascinating real-world driving change. It creates not just an illusion, but a driving experience that simulates a huge power increase of the engine. With variable settings, the ability to just turn it off and no negative consequences to the physical configuration of the engine, it really is a genuine cheap alternative to fuel and ignition performance re-mapping.

Paul

Interesting stuff gents.

Out of interest, what happens if you have Sprint Booster engaged (in say, a mild setting), and then you activate the sport button?

I'm personally a big fan of the sport button, it livens up throttle response (I think?) and it definitely livens up shift patterns. So would an ideal be Sprint Booster in a mild position, to give improved throttle response, and sport button activated to give improved shift patterns. Have you observed this to be the case?

Cheers,
Charlie.

Charlie,

AFAIK, in an x350, the Sport gearbox setting does nothing except vary the points at which upshifts are undertaken, and also change when part-throttle downshifts are triggered. It doesn't do anything to the throttle response or engine tune etc.

So with Sport selected, the car can be driven "quicker" but it's not because it's affecting engine power or tune.

What you might find with a Sprintbooster and Sport mode selected is that part-throttle downshifts would become much more prevalent as the gearbox thinks it is being asked to change down more frequently as the % throttle opening happens faster with the Sprintbooster engaged. I'm sure Mike can advise whether it feels like that in real use.

Hope that makes sense.

Paul

I have to admit, that apart from a session at Test Hill, Brooklands with Paul present earlier this year, that is the only time I`ve ever used the Sport button!

The reason for that is that this car has so much grunt in the standard economy mode, that I`ve never felt the need or urge to use the Sport selection. However, as regards Sprint Booster use in general road situations, the extra options of response just add to the fun.

Around town, I`m running Green 2 which is a softish setting that is better than the standard OE setting alone and just makes the car a little less prone to throttle lag. Running away out of town, I tend to raise the setting to Green 5. This becomes useful when wanting a snappy response and instant thrust. Very useful when at the last part of a motorway entry slip road as you join a fast moving traffic flow. Four or five seconds of full blast has you up to speed and out in the third lane before you know it and makes for a ballisticaly fast piece of machinery.

Tail gaters are quickly disposed of as they simply can`t keep up with this XJR! Believe me when I say this particular car is searingly quick. The Sprint Booster just gets the action going that much quicker. One can see the looks of astonishment as you go rocketing out of an irritating bunched up traffic situation. I don`t think there are many vehicles out there on the motorways that could even touch this level of performance. Suffice to say that one really does have to excercise considerable restraint at times. The car is as smooth as silk and just gets smoother as speed increases. It is all done without any effort at all. The same goes for the potential of loosing ones driving licience and getting locked up for several months.

Mike