Sprint Booster A technical white paper
Contents
1. a technical white paper position gaining a bit over stock Notice however that on releasing the accelerator the reverse is true Because the top 1 3 of the pedal is dead throttle response is lengthened by about 1 second Using this information does Sprint Booster improve throttle response and as a result yield faster acceleration The Sprint Booster amplifies or increases the amplitude of the accelerator pedal signal It directly affects only this one parameter signal amplitude It in and of itself doesn t really do anything faster The speed at which things get done depends upon how fast the driver presses the accelerator pedal So we must know how fast the pedal is moving to see if things are happening faster Let s consider what happens when we depress the accelerator pedal We are moving the pedal over a unit of time In my case if I stomped on the pedal I could get it to the floor in about 0 2 second The accelerator pedal signal increases with travel It will increase to maximum value in 0 2 second in this case With the Sprint Booster in circuit maximum value is reached at 2 3 travel Converting to time that would be 2 3 x 0 2 or about 0 13 seconds So we shaved off 0 07 in the time it takes to go to maximum value when flooring it What if I took 0 3 seconds to floor it With Sprint Booster the ECU would see maximum accelerator signal in 2 3 x 0 3 or 0 2 seconds But wait that is exactly the same time as the s2. Sprint Booster A technical white paper Dick Bipes September 2007 Introduction Several Mercedes owners had installed a Sprint Booster in their cars and subsequently posted rave reviews about it I wondered if all of their claims were true Frankly I was skeptical but if these owners were on to something I might want a Sprint Booster in my car I also wanted to know how the Sprint Booster worked I decided to investigate The results of my investigation are presented here The Sprint Booster is an aftermarket electronic module that plugs in between the accelerator pedal and the engine control unit ECU in vehicles equipped with an electronic throttle control Many Mercedes BMWs Audis and other vehicles sold today employ electronic throttle control and more vehicles are going that way The Sprint Booster web site makes these claims regarding electronic throttle control and the Sprint Booster The ECT system Electronic Throttle Control also known as drive by wire has the unfortunate downside of delayed throttle response and subdued acceleration creating problems in certain circumstances such as up hill starts quick gearchanges overtaking etc The Sprint Booster aims to overcome this throttle response delay for ECT equipped vehicles providing crisp on tap acceleration at the driver s disposal By installing the SPRINT BOOSTER we eliminate the delay that occurs from the moment that the throttle is depr
3. ch as relaxed and aggressive acceleration My car is a 1999 Mercedes Benz SLK 230 with a manual transmission In my car the accelerator pedal sensor s signal is a voltage of about 0 2 volts at rest and Bipes Page 2 September 2007 Sprint Booster a technical white paper about 4 4 volts at full throttle There is a redundant signal at about half that amplitude which I did not record The TPS is about 0 7 volts closed and 4 6 volts open On my charts I have scaled these signals accordingly Throttle response measurements The first measurements that I made were of the stock system without Sprint Booster To map the throttle response to accelerator pedal I slowly depressed the pedal over a period of about one and a half seconds The resulting data log is in Figure 1 WINDAQ x WDQ DER File Edit View Search Sealing Transform XY Options Help 4 500 Full 200 ivi BASE 287 200 SEC TBF aff SEC TM off EOF T 167 SEC DIV b Figure 1 Stock accelerator pedal response In this graph the blue line is the accelerator pedal sensor and the gray one is the TPS If I had been perfectly smooth in pressing the accelerator pedal the blue line would have been perfectly straight Nonetheless it s close enough to make some observations about throttle response Note that at 1 2 accelerator pedal depression the TPS reads about 1 4 of full value At accelerator the TPS is about 1 2 At full accelerator pedal to the fl
4. characteristic curve for a quiet driver is active after a long drive on the motorway then the accelerator pedal must be pressed down unusually hard to obtain a higher acceleration level So the ECU actually does on its own what the Sprint Booster does It changes the gain or response to the accelerator pedal However unlike the Sprint Booster which applies a fixed gain in these Mercedes applications the ECU varies the gain between at least two characteristic curves OK If I ve been driving my stock Mercedes on the motorway or freeway a long while the ECU switches to the quiet driver curve Of course as the driver I have no indication of this Now if I want to pass and I press the pedal down a bit say to the 70 point what do I get Because I m on the quiet curve I would get 40 power at 50 pedal so I suppose I get maybe 60 70 power at 70 pedal we don t know because Mercedes doesn t tell us But if I have a Sprint Booster installed now what happens The Sprint Booster multiplies the 70 pedal by 1 3 to 91 I m still on the quiet curve but since there s no difference between curves above 90 pedal travel and that s what the ECU got from the Sprint Booster boom I get 90 power Feels great Note that Mercedes tells me that I could Bipes Page 9 September 2007 Sprint Booster a technical white paper get the same 90 power without the Sprint Booster I just need to hit 90 pedal But of course that feels
5. control is very responsive Let s compare throttle response with and without Sprint Booster Figure 5 shows rapid depression hold the release of the accelerator pedal with Sprint Booster installed Bipes Page 6 September 2007 Sprint Booster a technical white paper Z WINDAQ sb WDQ File Edit View Search Sealing Transform XY Options Help 4 500 BASE 256 033 SEC TBF 418 317 SEC TM 38 0 EOF T 167 SEC gt Figure 5 Sprint Booster throttle response The top graph plots accelerator sensor versus Sprint Booster Consistent with what has already been observed the two outputs are near identical at first but the Sprint Booster output rises a bit faster and hits maximum value a bit sooner less than 1 second than the accelerator sensor This is because the pedal more sensitive for the first two thirds travel and dead for the last third of its travel with Sprint Booster installed The middle portion plots Sprint Booster output versus TPS Compare this graph to the one in Figure 2 You can see that they are nearly identical as would be expected The bottom graph plots accelerator sensor versus TPS Here we see that initially the throttle response is virtually identical to that with no Sprint Booster connected However at the top 1 3 of accelerator pedal travel where the pedal has now become dead the throttle response catches up to the accelerator Bipes Page 7 September 2007 Sprint Booster
6. el is recognized by the control unit The throttle valve opens more slowly The entire opening angle in this case is approx 50 In a vehicle equipped with traction or stability control the ECU may close the throttle based upon wheel spin or loss of traction even if the accelerator pedal is not moved The ECU also may limit throttle response in the case of a fault such as engine overheating In some vehicles the ECU may alter the response of the throttle to the accelerator depending upon how the pedal is used adapting to the driving style For example here is a description by Mercedes of what they call their adaptive accelerator pedal system in some of their vehicles The engine control unit recognizes how the accelerator pedal is being actuated and switches between characteristic curves Eighty percent of the engine load is released for a pedal travel of about 50 for a sporty driver and about 40 for a quiet driver There is no further difference felt above a pedal travel of about 90 Measurement Setup I measured the response of my car s system both with and without a Sprint Booster installed To measure my car s system I connected a DATAQ DI 194RS data logger to the accelerator pedal sensor signal and the throttle position sensor TPS in my car With a Sprint Booster plugged in I also measured the output signal of the Sprint Booster I logged measurements over several minutes time driving under various conditions su
7. es Page 12 September 2007 Sprint Booster a technical white paper Conclusions The Sprint Booster is a simple amplifier that multiplies the accelerator pedal sensor signal making the accelerator pedal more sensitive It does not eliminate any significant delay in throttle response nor does it greatly improve acceleration figures It does not change the adaptive throttle control programming of electronic throttle control vehicles It does change pedal feel This change in feel is interpreted by some as improved throttle response acceleration and a change in adaptive throttle control programming Considering what it actually does it is expensive Bipes Page 13 September 2007
8. essed and the electronic throttle control opens the butterfly thus greatly improving the car s acceleration figures Let s see if these claims are substantiated Background The throttle is a valve in the air intake that regulates the amount of air that the engine takes in It is controlled by the accelerator pedal We call the accelerator Sprint Booster a technical white paper pedal the gas pedal but it does not regulate gasoline it regulates air Technically I suppose we should call it the air pedal but that doesn t sound very macho If a car has a carburetor the carburetor meters fuel in response to the airflow and if it is fuel injected the ECU does this by controlling the injectors In either case more air results in more fuel and more of both cause the engine to increase in speed and power In conventional throttle systems the accelerator pedal is connected to the throttle by a cable In electronic throttle control systems the accelerator pedal is connected to a sensor that sends a signal to the ECU The ECU is connected to a servomotor that operates the throttle In most cases the ECU operates the throttle in proportion to the input from the accelerator pedal However in some cases it does not For example in some Mercedes vehicles Mercedes reduces the pedal sensitivity when driving in reverse as explained in their service manual The pedal value sensor characteristic curve is changed if reverse trav
9. hink as the transmission finally downshifts and I accelerate to pass Now what happens when I use Sprint Booster I press the accelerator pedal down a bit not so much as to engage the kickdown tactile feedback just like I originally did before but enough to hit the kickdown full signal threshold Remember the Sprint Booster multiplies the signal and hits full value at only two thirds pedal depression so I don t have to press very much Boom Kickdown downshift full throttle and I m off accelerating at maximum Wow That Sprint Booster is amazing Look at all the power it gave me I might think Of course I could have had the exact same power and transmission downshift had I just pressed harder in the first place But if I didn t know better I d probably swear that the Sprint Booster overcame the ECU s adaptive nature Some have speculated that the Sprint Booster keeps you in sporty mode but based on Mercedes description I question that I think that the Sprint Booster just overcomes quiet mode without the aggressive step down With little factual information is available regarding manufacturer s adaptive controls there is lots Bipes Page 10 September 2007 Sprint Booster a technical white paper of speculation on how it works This only fuels speculation on what Sprint booster actual does What is the Sprint Booster I did not disassemble the Sprint Booster in my possession as it was on loan to
10. l amplitude This gives a good clue as to what the Sprint Booster is really doing Itis an amplifier boosting the accelerator pedal sensor signal by about 30 As further evidence of this Figure 4 compares Sprint Booster output in gray against accelerator pedal sensor output in blue but with the voltage scales adjusted The Sprint Booster output tracks the input with each and every change quite nicely with a gain of about 1 3 2 WINDAQ sb WDQ FE File Edit View Search Scaling Transform XY Options Help 4 500 sims Cie ei eo SB i i i i Yf Sn ee Ai i 200 BASE 282 133 SEC TBF 392 217 SEC TM 41 8 EOF T 167 SEC DIV Figure 4 Sprint booster versus accelerator pedal sensor Bipes Page 5 September 2007 Sprint Booster a technical white paper What does this mean Basically the Sprint Booster makes the accelerator pedal about 30 more sensitive A side effect which can readily be seen in the graphs in Figure 3 and Figure 4 is that the accelerator pedal becomes dead beyond about two thirds travel with Sprint Booster It is important to note that any accelerator signal into the ECU using a Sprint Booster can be duplicated exactly by a driver without a Sprint Booster merely by pressing the accelerator pedal a greater distance There is only one small exception which will be covered later Sprint Booster and throttle response I already noted that the stock electronic throttle
11. me But it appears to be nothing more than an amplifier My guess is that it is a pair of op amps is employed to simply multiply the two accelerator sensor signals by 1 3 My further guess is that the difference between the various models of Sprint Booster is the amount of gain which would be set by a few resistors in the circuit Even in low volume production I estimate the cost of the electronics to be less than 5 and total parts cost of the unit to be less than 25 With a retail price upwards of 10 times that amount the Sprint Booster is probably a very profitable product Incidentally if I were permanently installing this device in my car I would want the Sprint Booster to have two completely independent amplifiers Why Mercedes wisely used two independent accelerator pedal position sensors for the ECU to sample In this manner a single point of failure can both be detected by the ECU a check engine light and code and worked around driven normally If the Sprint Booster does not use independent circuits a single point of failure could affect both outputs rendering the car inoperative or telling the ECU to floor it neither of which might be detected by the ECU as a fault This is unlikely perhaps but not impossible Addendum Another enthusiast sent me a different version of the Mercedes Sprint Booster for analysis As you can see by the attached graph the two versions basically do the same thing one just amplifies the accelera
12. more sluggish The car is not more sluggish it feels that way This is in essence what Sprint Booster is all about feel Here is another consideration regarding feel On some Mercedes vehicles a kickdown switch is used This is a switch on the accelerator pedal that is activated on full accelerator pedal depression The switch feeds into the control module for automatic transmissions As the name implies it is one input to tell the automatic transmission to downshift for quicker acceleration It has a tactile feel to it you can feel the switch and need to increase pressure on the accelerator pedal a bit to overcome it so you know by feel when you are engaging it Here s a little tidbit of information from Mercedes The kickdown switch was no longer used from 9 01 Recognition of full load is now achieved over the signal from the pedal value sensor The pressure point on the accelerator pedal before achieving the full load position remains OK So what happens if I have a vehicle equipped with tactile kickdown feedback but no actual switch If I m cruising along then want to pass and I push the accelerator pedal down to 70 as before the kickdown switch does not engage The engine speeds up but slowly as does the vehicle because the automatic transmission remains in top gear Hmm sluggish I might think I press harder hit the tactile point press harder still and engage kickdown Finally I t
13. nificant I d be very surprised if a typical driver could detect this small difference in time This data makes me suspect that drivers of electronic throttle response vehicles who are noting throttle lag or poor throttle response are experiencing some behavior other than true throttle lag At any rate in my car there is negligible actual throttle lag due to the electronic throttle control system and consequently little if anything that a Sprint Booster could do to change this Sprint Booster measurements I measured the response of a Sprint Booster model BDD 451A2 in my car Using the same methodology as I did to measure accelerator pedal sensor and TPS response I simultaneously logged accelerator pedal sensor Sprint Booster output and TPS Bipes Page 4 September 2007 Sprint Booster a technical white paper Figure 3 plots the accelerator pedal sensor versus Sprint Booster output I measured the physical movement of the accelerator pedal to determine the 4 1 2 and 2 3 accelerator pedal depression points WINDAQ sb WDQ DAR File Edit View Search Sealing Transform XY Options Help 4 500 AO 1 1 Volt j pepese aga jy oon eee 385 833 SEC TBF 286 517 SEC TM 57 2 EOF T 167 SEC d Figure 3 Sprint Booster response Notice that up to about two thirds accelerator pedal depression the Sprint Booster signal is increased or multiplied over the accelerator pedal sensor signal then becomes flat at maximum signa
14. oor the TPS is full value This non linear response is not surprising The pedal is in effect less sensitive at the low end probably what most people want for finer control under low speed conditions Next to measure throttle lag I pressed the accelerator pedal to the floor as fast as I could held it and then released it See Figure 2 Bipes Page 3 September 2007 Sprint Booster a technical white paper WINDAQ x WDQ DER Eile Edit View Search Scaling Transform XY Options Help 4 500 BASE J29 JIJ OEC TBE 104 058 SEC IM 76 072E0OF Ti 167 SECADIV gt Figure 2 Stock system throttle lag Notice that it took me about 0 2 second to floor the pedal and slightly less to release it Looking at the delta between the blue and gray lines notice also that actual throttle lag the delay between pressing the accelerator and opening the throttle is less than 1 second What does this mean Well to overcome the mass of the accelerator pedal and connected parts such as the return spring tension to move the pedal through 3 of travel took a finite amount of time about 0 2 seconds It is reasonable to assume that in a fully mechanical system there would be a similar lag of at least 0 2 second to fully open the throttle The electronic throttle control is adding less than 0 1 seconds to that In the context of real world throttle response for example 0 60 mph time this small amount of extra time is not sig
15. tock case when I stomped on it In fact for any rate of accelerator pedal travel less than absolutely mashing it as a driver I can duplicate the Sprint Booster result simply by pressing on the pedal a bit faster The only time that the Sprint Booster can make anything happen faster is if I absolutely mash the pedal to the floor Now let s consider the throttle butterfly valve It is driven by the ECU with inputs from the accelerator pedal and other sources Since in all cases but mashing the pedal I can duplicate the Sprint Booster signal to the ECU just by moving the pedal a bit more I can make the throttle move equally fast or slow with or without the Sprint Booster I just need to adjust the way I modulate the pedal The one time that I can t duplicate Sprint Booster is mashing the pedal OK so what about thos times when I do mash the pedal to the floor If you examine the TPS curves carefully you ll see that with or without Sprint Booster when mashing the accelerator pedal the throttle butterfly valve moves equally as fast for about the first half of its travel It s only when the throttle is more than half open does it actually move a bit faster with Sprint Booster The Sprint Booster speed gain when mashing the throttle is 0 07 second so 0 07 x travel is 0 035 second With Sprint Booster the throttle is open wider for 0 035 second How much wider Only a small fraction wider than the stock case at any given point in its travel In theor
16. tor sensor signal more than the other Bipes Page 11 September 2007 Sprint Booster a technical white paper Sprint Booster transfer function Sprint booster 0 0 0 5 1 0 1 5 2 0 2 5 Accel sensor BDD 451A BDD 451A2 I ran across this link in MBWorld org forums explaining the two models Here is the text from that link After long talks with Stamatis Boulekos I have learned that there are only two versions for MB and if you purchase yours from them or a authorized dealer you will not get the old aggressive version it simply is not made anymore You can tone down a manual trans by using the automatic version but that is the only difference one for manual and one for automatic This is from the owner of the company Der Mr Werner There are two Versions for MB One is for automatic transmission models and one version is for manual transmission models The part for manual transmission can only be installed in manual cars the part for automatic can be installed in automatic cars but also can be used in manual cars as a lighter version if someone wants the acceleration less sharp than the sharper manual version Best Regards Stamatis Boulekos hope this answers your question Of course the so called manual model can indeed be installed in an automatic car as the connectors are identical It s just that the accelerator pedal may be overly sensitive But who knows maybe some people would like it that way Bip
17. y that would translate into a faster 0 60 acceleration Bipes Page 8 September 2007 Sprint Booster a technical white paper figure of something less than 0 035 second In actuality the increase is so small that it is not measurable Sprint Booster does not improve throttle response or acceleration Sprint booster and adaptive throttle Several Sprint Booster users have complained about the adaptive throttle in their vehicles with an electronically controlled throttle They claim that performance becomes sluggish over time and that using a Sprint Booster overcomes this Knowing that Sprint Booster is nothing more than an amplifier of the accelerator pedal sensor signal it s hard to understand this claim Let s look into this A lot of people speculate on exactly what the adaptive control in their vehicle is or does There is precious little information readily available on this subject I was able to get the following information from the Mercedes service manual through my subscription to alldatadiy com Adaptative accelerator pedal model 203 209 211 215 220 230 The engine control unit recognises how the accelerator pedal is being actuated and switches between characteristic curves Eighty percent of the engine load is released for a pedal travel of about 50 for a sporty driverer and about 40 for a quiet driver There is no further difference felt above a pedal travel of about 90 Note If for example the
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