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Thread: birth of another C55

  1. #201
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    Originally posted by c55m8o
    hold your opinion until you see it calculated out though (I'm tell'n ya, get CatTest2000 )... I'd say after seeing the runs, you shouldn't underestimate the impact such a drop-off in torque @ high RPM can have, and how that works against raising the rear-end gear ratio, too much. Hey, I was a =die-hard= advocate of converting my rear to 3.45:1 ; that is, was, but not with this engine's torque rolling off as it does @ high rpm .

    yes, CarTest2000 also says 3.07 is pretty much the optimal rear. What I was saying was it also proves out that going longer (to 2.82:1) would be better with that engine then going to shorter gearing (to 3.45:1).

    BTW, raising the gear ratio is not all upside ; there's trade-off there too, since the shift occurs a few mph sooner in each gear when you have shorter gears; (I hope I can explain this right) ... for the few mph difference between where it shifts with the shorter gears, compared to where it used to shift with the longer stock gears, acceleration is actually =lower= because you have less torque multiplication working for you, as you're in the next higher gear. Less "F", same "m", less "a". So that actually takes more time to get through that few mph range, then with the stock gears. Of course, for all the rest of the mph range in that gear, acceleration is quicker with the shorter gears. However it's important to realize there's some given back through the RPM range, so it's not all up-side.

    This is also why I say going to shorter gears should be accompanied with a raise in the redline as well (which of course is easier said than [safely] done). [ Please read my analysis on this subject here ... ]

    If this is done, there is no trade-off, as
    a) you have more pull in each gear @ the tire's contact patch from the shorter gears...
    b) since you have a higher redline, you can now pull longer (to a higher RPM) then you did before, and you will not have to shift out of the gear sooner because of the shorter gear.

    I'm really not sure if this is clear enough. If you read my analysis on this, it should be clearer. Also, please read my reply to ironchefc43 just under the one I'm linking to, regarding the gains if you raise the redline to accompany the shorter gears.

    Yes I agree threre is threshold , you cannot just pick random shorter gear. you have to calculated to determine which is optimal for.

    then again what is optimal for all around is not the same for optimal performance.

    Since optimal performance doesn't always conform to better MPG.




    PS: I don't see why that thread contracdic with I am saying.
    Especially going from 3.07 to 3.45 is not that extreme.
    When you go much shorter gear you will most likely need to increase the read line since the sweep rpm spot shift higher now. So you want to be able to use the usable power through out the entire rpm in which now is higher (hence need to raise rpm limit).

    Regardz,


    Regardz,
    J Irwan by AMG........Motorsport.

  2. #202
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    Originally posted by coolcarlskic43
    The engine TQ is multiplied by the differential to spin the rear wheels at a certain revolution.Then you have to apply a formula based on all of that.

    I strongly dissagree about the fact that having 4.11 gears in the rear of my E36 M3 will show an increase in rear wheel hp as opposed to having a 3.23 diff on the car.The ex. you gave about the C5 and the E46 M3 does not equate to the E46 M3 putting down similar or more hp to the wheels than the C5 because of the diff.No offense but that does not make sense,if that's what you are saying.

    Alot has to do with the characteristics of the motor and weight + rear axle ratio of the two vehicles .

    The two vehicles are very close when it comes to rwhp 270-280(M3) vs rwhp 295(Corvette).This is not because of the differential.How they run against each other off of the dyno can be attributed to weight,engine character,and gearing. They are also close in rwhp.

    Lets talk apple to apple

    On this example E46 M3 using 4.11 vs 3.23 diff
    4.11 will produce more rearwheel hp number.


    I am getting tired saying smething over and over again.
    If you can't agree too bad. I'd suggest to do more reading.


    Regardz,
    J Irwan by AMG........Motorsport.

  3. #203
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    Originally posted by c55m8o
    BTW, J, I still wish to come to some clarity on the subject... I think I put my finger on the whole back and forth. I finally realize we still continue to use the same terminology, but are talking about slightly different things when we say rw hp (or rw torque) ... I'll annotate this with a visual aid <grin>.

    So, please note my HP/Torque graph I posted in the middle of this thread ... actually, I'll post it here...

    (btw, this is the stock E55 chip program. DYNORUN.001 done with the mod'ed E55 program peaked @ 306hp, but I don't have it graphed like this.)

    So to understand, I'll ask, how is it the HP & Torque graphs when the car is in third, is measured and rendered to the same values @ the same RPM as when the car is in fourth? I know that this graph represents hp (& calculated torque) to the rear wheels, not crank. (any why I'm saying "dynos normalize", to =remove= gearing from the equation).

    I also know though, you're saying "hp to the wheel is greater the shorter the rear" ... well yes, but I guess I'd like to call that linear force @ the tire's contact patch, not rwhp. But isn't it true that's also the case the lower the tranni gear? i.e. more force @ the tire's contact patch in 3rd vs. 4th, and 2nd vs. 3rd, and 1st vs 2nd?

    So what I'm trying to understand, is it you are saying that the graph above is =not= a rear wheel hp and rear wheel torque graph? What is it then / what would you name it? I don't think that's the case. And I know it's not "crank" hp & torque. So what I'm having trouble with is, if that graph shows rwhp, how can we call what you're saying -- that =includes= gearing in the equation and any resulting graph if it were to be graphed -- rwhp too? (actually, CarTest2000 does have a particular name for that, but that's on my laptop and I'm not up for going to get it, plug it in and turn in on to see @ the moment... ).

    Therefore, perhaps, wouldn't it be better to call the force being applied the the tire's contact patch that is a result of including gearing in the equation which you keep using, =effective= HP and =effective= torque? ... it is the =effective= torque applied to the tires' contact patch, as a result of torque multiplication when taking gearing into account as well.

    So I finally get to the point, that I guess it all boils down to is it generally accepted to call it rwhp, and include gearing? I personally, thought it was not ; that rwhp is the engine crank torque, passed through the drive-train and tires, and the rotating torque at a speed (a.k.a. HP) is measured, and normalized to remove gearing ; and if gearing was included, it should be called something else (i.e. effective rwhp).

    thoughts?

    All I was pointing out the relation of higher rear diff on C43 vs E55 E210. Which why attribute to different reading.


    If you want to prove me wrong try the same car dyno with different rear-diff gear ratio and you will see what I am trying to say.


    When it comes down to dyno using stock gearing sure this applies:

    quote:
    So I finally get to the point, that I guess it all boils down to is it generally accepted to call it rwhp, and include gearing? I personally, thought it was not ; that rwhp is the engine crank torque, passed through the drive-train and tires, and the rotating torque at a speed (a.k.a. HP) is measured, and normalized to remove gearing ; and if gearing was included, it should be called something else (i.e. effective rwhp).


    But when the gearing changes is in the equation that when you see increase in rearwheel hp.

    If you think about it, dyno doesn't know whether the geariing has been changed from 2.82 to 3.07 for example. (all it jobs is measuring rotational force either applying brake horse power or vise versa).
    All it knows when it measure the rotational force is now greater (as a result of the new gearing).

    As I mentioned before upgrading the rear-end diff is not a hack job. Its need to be calculated properly.
    If you see some aftermarket company offer it for a specfic ratio, its there for a reason (they probably already done back to back calculation and R&D to select particular ratio, otherwise if it is too high you might just getting better 0-60 time , but slower at 1/4 miles and slower at higher speed).




    Regardz,
    J Irwan by AMG........Motorsport.

  4. #204
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    (yo ; ya gotta stop including the =whole= thread on the replies... that's just plain ridiculous! ...don't you agree? ...I'm hoping you aren't doing it on purpose to slam/dis the thread? and me? )

    Originally posted by J Irwan
    quote:
    So I finally get to the point, that I guess it all boils down to is it generally accepted to call it rwhp, and include gearing? I personally, thought it was not ; that rwhp is the engine crank torque, passed through the drive-train and tires, and the rotating torque at a speed (a.k.a. HP) is measured, and normalized to remove gearing ; and if gearing was included, it should be called something else (i.e. effective rwhp).


    But when the gearing changes is in the equation that when you see increase in rearwheel hp.
    Sorry? I'm not sure what you're saying (typos?) , but I'm sure it didn't answer/address my question.

    Again, is it accepted practice to include torque multiplication offered thru gearing in rear-wheel hp measurements? ... operative word being "measurements" ; because I know it not to be the generally accepted practice. After all, then everyone would "measure" their HP in 3rd and get higher results, or 2nd and still higher, or 1st and still higher. (and we all know that's not the way it works )

    And if you will, why did the dyno graph I posted produce the same values in 3rd gear as in 4th?

    Remember, I am, and always have been, (as well as Carl) talking about the =MEASURED= HP a dyno returns... not =EFFECTIVE= RWHP that is a result of =BOTH= tranni and rear-end gearing. I reiterate what you are saying is not =measured= RWHP.

    I agree now as I always have, =YES= shorter gears will produce more =EFFECTIVE= rwhp ; though that was never what I was talking about. I would have stated it earlier if I would have realized what you were talking about was different then what we were talking about. I will never agree that my car measure higher rwhp then you thought it should because it has 3.07 gears ; because gearing is automatically factored out in a dyno.

    I will reiterate when a dyno =MEASURES= rwhp, it removes gearing from the values it returns, since it knows engine RPM and dyno drum rotation speed, so can calculate a normalization factor to remove torque multiplication from the measured value. The combination of tranni gear and rear diff gear and tire radius, which all factor into the amount of linear force produced @ a tire's contact patch, is a "black box", and gets reduced to one number. This one number is a single normalization coefficient (sic) that is "less then 1" -- the lower the tranni gear engaged in the tranni, the smaller the normalization value for that measurment sub-range -- and is multiplied to the raw physical (effective) rwhp measured, to remove all gearing and make the dyno interplolate the physical (effective) rwhp, and reduce it to as if it was a 1:1 gearing with a tire having a 1 foot radius ; thereby producing a measured rwhp.

    I don't need to spend thousands of thousands of $$$ changing my rear-end to know that's how dyno measurements work.
    ...computerized dynos that is ; where drivetrain parameters are not entered and fixed into it, rather it is free to calculate the normalization factors ; if you measure a car on an older dyno, where you had to enter the drivetrain values and tire dimensions, then change the rear but you =don't= change the drivetrain values ... YES, it will measure a higer HP -- but that is ERRONEOUS, because the dyno was mis-configured with incorrect drivetrain values. [!]

  5. #205
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    Originally posted by J Irwan
    If you think about it, dyno doesn't know whether the geariing has been changed from 2.82 to 3.07 for example. (all it jobs is measuring rotational force either applying brake horse power or vise versa).
    All it knows when it measure the rotational force is now greater (as a result of the new gearing).
    um, yes it does [!] ... I have thought about it -- and the guy who operates the dyno I last used has apparently thought about it because he told me this same thing wehn I was there that I posted in my last post, which he learned from the dyno manufacturer, reinforcing what I knew to be the case for quite some time -- and it =does= know the difference between 2.82 gearing and 3.07 gearing, because when you dyno a car it also knows the engine RPM right off your plugs or coil, and knows the final rotation speed of the rear wheel via the dyno's drum speed... (yes ... and the dyno normalizes the values using the ratio difference between drum RMP and engine RPM ... bla bla bla...)

    Fine. Continue to believe what you will....more pwr2ya...

    ... I will continue to know putting a car on a dyno will not =measure= higher or lower rwhp generated by the engine with different (shorter or longer respectively) rear-end gear ratios, or if it's measured in 3rd or 4th or 2nd, which is basically the same thing on a larger gear-ratio scale.

    ...and I will continue to call what you call "rwhp", "effective rwhp".

    ...but if you do call a hp that includes gearing @ the wheels, "rwhp", what do you call rwhp a dyno measures?

  6. #206
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    Originally posted by J Irwan
    As I mentioned before upgrading the rear-end diff is not a hack job. Its need to be calculated properly.
    If you see some aftermarket company offer it for a specfic ratio, its there for a reason (they probably already done back to back calculation and R&D to select particular ratio, otherwise if it is too high you might just getting better 0-60 time , but slower at 1/4 miles and slower at higher speed).
    That is definitely something I will support. Happly, I'll again say CarTest2000 actually said the 3.07 was a better gearing for my car then 2.82 gears, after I entered the measured rwhp curve and it used that in its interpolations and calculations.

  7. #207
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    Originally posted by c55m8o
    That is definitely something I will support. Happly, I'll again say CarTest2000 actually said the 3.07 was a better gearing for my car then 2.82 gears, after I entered the measured rwhp curve and it used that in its interpolations and calculations.

    Off course.

    Now try with 3.45 as 3.45 should be an upgrade to your car not the 2.82


    Regardz,
    J Irwan by AMG........Motorsport.

  8. #208
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    Originally posted by J Irwan
    PS: I don't see why that thread contracdic with I am saying.
    Especially going from 3.07 to 3.45 is not that extreme.
    When you go much shorter gear you will most likely need to increase the read line since the sweep rpm spot shift higher now. So you want to be able to use the usable power through out the entire rpm in which now is higher (hence need to raise rpm limit).
    That wasn't meant as any disagreement with what you were saying ... just an "FYI". I said "BTW, raising the gear ratio is not all upside ; there's trade-off there too, since the shift occurs a few mph sooner in each gear when you have shorter gears; (I hope I can explain this right) ... etc..."

  9. #209
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    Originally posted by J Irwan
    Off course.

    Now try with 3.45 as 3.45 should be an upgrade to your car not the 2.82
    LOL ... I did ... I did... =Trust= me, I =wanted= 3.45:1 gears. I don't have my laptop on again ; I have to make some screen captures and post them. I'll have a visual aid hopefully tomorrow of what CarTest2000 simulates and I'll post it here.

  10. #210
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    Originally posted by c55m8o
    (yo ; ya gotta stop including the =whole= thread on the replies... that's just plain ridiculous! ...don't you agree? ...I'm hoping you aren't doing it on purpose to slam/dis the thread? and me? )

    Sorry? I'm not sure what you're saying (typos?) , but I'm sure it didn't answer/address my question.

    Again, is it accepted practice to include torque multiplication offered thru gearing in rear-wheel hp measurements? ... operative word being "measurements" ; because I know it not to be the generally accepted practice. After all, then everyone would "measure" their HP in 3rd and get higher results, or 2nd and still higher, or 1st and still higher. (and we all know that's not the way it works )

    And if you will, why did the dyno graph I posted produce the same values in 3rd gear as in 4th?

    Remember, I am, and always have been, (as well as Carl) talking about the =MEASURED= HP a dyno returns... not =EFFECTIVE= RWHP that is a result of =BOTH= tranni and rear-end gearing. I reiterate what you are saying is not =measured= RWHP.

    I agree now as I always have, =YES= shorter gears will produce more =EFFECTIVE= rwhp ; though that was never what I was talking about. I would have stated it earlier if I would have realized what you were talking about was different then what we were talking about. I will never agree that my car measure higher rwhp then you thought it should because it has 3.07 gears ; because gearing is automatically factored out in a dyno.

    I will reiterate when a dyno =MEASURES= rwhp, it removes gearing from the values it returns, since it knows engine RPM and dyno drum rotation speed, so can calculate a normalization factor to remove torque multiplication from the measured value. The combination of tranni gear and rear diff gear and tire radius, which all factor into the amount of linear force produced @ a tire's contact patch, is a "black box", and gets reduced to one number. This one number is a single normalization coefficient (sic) that is "less then 1" -- the lower the tranni gear engaged in the tranni, the smaller the normalization value for that measurment sub-range -- and is multiplied to the raw physical (effective) rwhp measured, to remove all gearing and make the dyno interplolate the physical (effective) rwhp, and reduce it to as if it was a 1:1 gearing with a tire having a 1 foot radius ; thereby producing a measured rwhp.

    I don't need to spend thousands of thousands of $$$ changing my rear-end to know that's how dyno measurements work.
    ...computerized dynos that is ; where drivetrain parameters are not entered and fixed into it, rather it is free to calculate the normalization factors ; if you measure a car on an older dyno, where you had to enter the drivetrain values and tire dimensions, then change the rear but you =don't= change the drivetrain values ... YES, it will measure a higer HP -- but that is ERRONEOUS, because the dyno was mis-configured with incorrect drivetrain values. [!]
    Steve I clearly understand what you're saying which has me understanding what he's trying to say which I can clearly see in my mind.Question? This is weird! If one were to put a 3.07 rear in a CLK430 vs it's 2.82,would it theortically do what J Irwin is trying to say?Interesting!Hence I understand the term "effective" RWHP.Which makes total sense.All I know is that with the stck E55 S/W in my car was putting down mid to high 280's rwhp just like an E55 which we know has a taller rear gear ratio.

    Are the rear gear ratios taken into condideration prior to the car being placed on the dyno?I think I do remember George asking me what the diff gear ratio was.But he could have been just asking. I will call him this morning and ask him how this RWHP thing wrks according to the dyno.

    I know you were'nt at ICS performance when we did our dyno runs but Marc(Tump) dynoed 238 RWHP in his C43,Curtis dynoed 234 RWHP in his C43 and Neal dynoed 225 RWHP in his CLK430.Weird for the CLK to only be down 9 RWHP from Curtis C43 when they advertise 302HP crank (C43) VS 275HP crank(CLK430).Interesting I thought.Am I going off on another tangent as well?
    ,Please let me know. Sorry about the several different questions.Hey after all you are the engineer so I have confidence you can handle it!



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  11. #211
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    Originally posted by J Irwan
    Off course.

    Now try with 3.45 as 3.45 should be an upgrade to your car not the 2.82


    Regardz,
    In the 1/4 mile yes!!!!Effective hp yes! Rwhp on the dyno?
    Originally posted by J Irwan
    Lets talk apple to apple

    On this example E46 M3 using 4.11 vs 3.23 diff
    4.11 will produce more rearwheel hp number.


    I am getting tired saying smething over and over again.
    If you can't agree too bad. I'd suggest to do more reading.


    Regardz,
    Hate to sound brash man but I suggest you RELAX,CALM DOWN ,we'll find out. Jeez!



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  12. #212
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    Originally posted by 714guy
    Thanks, for the info. Just didn't know how i could get the flanges.
    714guy, not sure if you'll read this thread and get this ... if so, I was @ the guys house who made those custom turbo headers for Jeff to talk to him about headers for my car ... I saw all the jigs and flanges he had on his wall for cars he's done, or has in stock for cars he does often, and I asked him if he had an extra C36 flange ... he didn't think so, but low and behold after a little bit of looking, he's got one. So, if you want/need it, I can put you in contact with the guy. lemme know.

  13. #213
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    Originally posted by c55m8o
    714guy, not sure if you'll read this thread and get this ... if so, I was @ the guys house who made those custom turbo headers for Jeff to talk to him about headers for my car ... I saw all the jigs and flanges he had on his wall for cars he's done, or has in stock for cars he does often, and I asked him if he had an extra C36 flange ... he didn't think so, but low and behold after a little bit of looking, he's got one. So, if you want/need it, I can put you in contact with the guy. lemme know.
    Steve there is a guy (JLee) on MBworld using headers and his 1/4 mile and trap times were still slower than mine unless I have the wrng guy.This guy spent alot of money.You know what my next mod is gonna be? CAMS,definitely!!!!



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  14. #214
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    Originally posted by coolcarlskic43
    Steve there is a guy (JLee) on MBworld using headers and his 1/4 mile and trap times were still slower than mine unless I have the wrng guy.This guy spent alot of money.You know what my next mod is gonna be? CAMS,definitely!!!!
    ...really! Jeff's been saying that to me too. So, which ones? Custom?

    I dunno who makes a "hotter" NA cam. I think the one Kleemann sells is a F/I cam, so it has less overlap; I think we/d want a bit more for NA (though I don't have much knowledge on this one).

    ...so how much will that cost + time to install you think? (well ok, how much would time normally cost, for me, not you. ) We =gotta= also get the manifold spacers Carl. (www.outlawengineering.com) ... I gotta remember to call them one of these days. I guess it would be good to install both @ the same time.

    EDIT: I corrected the URL... no hyphen.

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    J Irwan, here's what I promised you -- hoped I'd have it the next day, but it's been a couple of weeks. Below are a series of screen captures displaying the analysis of how different rear differential gearing will affect performance done in CarTest2000...

    To recap, my assertion was the 3.07 gearing was actually near optimal for the C55... and that going with shorter gears of 3.45 or higher was actually slower; that the benefits of "going shorter" ran out much sooner then you were saying. To use your terminology, it's "out of the sweet spot" sooner then you'd thought ... and that I had seriously wanted to do that very ring & pinion change to those very gears, but no longer did after seeing this.

    So, on to the pretty pictures... First, the specifications used in all the simulations:

    GENERAL/BUILT-IN SPECIFICATIONS:

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)


    CUSTOMIZATIONS:

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)


    DRIVE POWER AND LOSS:

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)

    Please notice there are no transmission losses. This is a "good thing" because I'm using actual measured values from the dyno, as noted in the "c55 car specs - model specific" image, with the selection "Custom Power Curve Use = Drive Wheels". The "transmission losses" values used for simulating an automatic transmission are probably the most difficult to estimate, and being able to remove them from the simulation will lead to more accurate results.



    OPTIMAL GEARING - 0-60 mph :

    Gear Ratio Finder - 0-60 mph : ...says 3.19 gears are optimal.

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)


    Gear Ratio Simulation Analysis - 0-60 mph : ...says going higher then about 3.33 reduces performance significantly, until you get near and over the 5.0:1 gear ratio range <yikes>. (I stopped the analysis and didn't go into such an infeasible gearing)

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)



    OPTIMAL GEARING - 1/4 mile :

    Gear Ratio Finder - 1/4 mile : ...says 3.16 gears are optimal.

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)


    Gear Ratio Simulation Analysis - 1/4 mile : ...again says the current 3.07 gears are near optimal. 3.26:1 is available for that pumpkin, and would be slightly better (worth it?) , but 3.45:1 or higher is slower, not faster.

    (Click Image then click 'Get Original Uploaded Photo' for Full Size)


    ...so J, I didn't mean to be argumentative just for the sake of it. I was basing my statements on legitimate analytical simulation, that calculates the force to the contact patch of the tires at every mph speed and engine rpm, in every gear, and takes into account linearly and geometrically increasing resistances and losses from many many sources.... and knowing the mass, can calculate the acceleration.

    And J, dare I say, if I were to do this simulation with a different engine, having a torque curve biased to the higher rpm range, and redline at say, 7K or 8K, that we would indeed see better performance out of using much shorter gears then the M113 engine will benefit from.

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    Originally posted by c55m8o
    ...really! Jeff's been saying that to me too. So, which ones? Custom?

    I dunno who makes a "hotter" NA cam. I think the one Kleemann sells is a F/I cam, so it has less overlap; I think we/d want a bit more for NA (though I don't have much knowledge on this one).

    ...so how much will that cost + time to install you think? (well ok, how much would time normally cost, for me, not you. ) We =gotta= also get the manifold spacers Carl. (www.outlaw-engineering.com) ... I gotta remember to call them one of these days. I guess it would be good to install both @ the same time.
    Jeff would perhaps charge us both the samething at this point but I'm only guessing.

    I thought about going Kleeman but yes the overlapp is a concern.They claim their cam is also good for NA use but I'm not certain the overlapp will be enuff.

    I'm sure there are German companies out there that produce them but we have to do the research.One German company that I know that makes them for BMW's and other German cars is Schrick.I have that in my M3.Nice mid range and topend especially with full header ,midpipe ,exhaust and SW upgrade.She will be next to run on the track.(M3)



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  17. #217
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    Originally posted by c55m8o

    ...so J, I didn't mean to be argumentative just for the sake of it. I was basing my statements on legitimate analytical simulation, that calculates the force to the contact patch of the tires at every mph speed and engine rpm, in every gear, and takes into account linearly and geometrically increasing resistances and losses from many many sources.... and knowing the mass, can calculate the acceleration.

    And J, dare I say, if I were to do this simulation with a different engine, having a torque curve biased to the higher rpm range, and redline at say, 7K or 8K, that we would indeed see better performance out of using much shorter gears then the M113 engine will benefit from.
    Good stuff Steve, and I still did the 13.39 @102mph with the stck 3.07 diff,18" mono's and open diff.Would be nice if i had LSD.

    Steve don't the 18" rims make my diff gears taller? I have 255-35-18's on the rear.I'm wondering if I should put the 17's back on for the track? Read this:http://www.mbworld.org/forums/showthread.php?t=121083



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  18. #218
    C55 Charter Member
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    Originally posted by coolcarlskic43
    Steve don't the 18" rims make my diff gears taller? I have 255-35-18's on the rear.I'm wondering if I should put the 17's back on for the track? Read this:http://www.mbworld.org/forums/showthread.php?t=121083
    well, yes, a tad ... the goal of a "plus one" upsize is when you go from 17" rims to 18" rims, you also go wider, and from a profile of 45s to 40s or 40s to 35s (depending on front or rear) ; but the key being that the goal to a "plus one" upsize is the outer diameter [OD] of the tires are basically the same. The reality is the tire's new OD isn't the exact same.

    Stock, our rear drive tires are 245x40-17 ; upsized one, as you say and as I have, it's 255x35-18. The 17" rim + tire's OD is 24.7" ; the 18" rim + tire's OD is 25". That's only a 1.3% difference; so that could equate to something like having a 3.03:1 rear but continuing to use the stock tire's OD, instead of a 3.07:1 rear with the upsized tires ... a bit longer, but pretty negligible. But then again, the graphs above say, slightly shorter is better then slightly longer; if only by a bit, but it's still better. So to gain every little bit, the 17" should help you out.

    ...If you use 255x30-18" tires, the OD is 24" ... I think that calculates out to as if the car was using 3.156:1 gearing...


    I get that from here:
    http://www.miata.net/garage/tirecalcold.html

    That tool is actually Javascript. You can save that page locally to your harddrive and open it up and use if, w/o having to go to the internet to use it.

  19. #219
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    715
    Originally posted by c55m8o
    well, yes, a tad ... the goal of a "plus one" upsize is when you go from 17" rims to 18" rims, you also go wider, and from a profile of 45s to 40s or 40s to 35s (depending on front or rear) ; but the key being that the goal to a "plus one" upsize is the outer diameter [OD] of the tires are basically the same. The reality is the tire's new OD isn't the exact same.

    Stock, our rear drive tires are 245x40-17 ; upsized one, as you say and as I have, it's 255x35-18. The 17" rim + tire's OD is 24.7" ; the 18" rim + tire's OD is 25". That's only a 1.3% difference; so that could equate to something like having a 3.03:1 rear but continuing to use the stock tire's OD, instead of a 3.07:1 rear with the upsized tires ... a bit longer, but pretty negligible. But then again, the graphs above say, slightly shorter is better then slightly longer; if only by a bit, but it's still better. So to gain every little bit, the 17" should help you out.

    ...If you use 255x30-18" tires, the OD is 24" ... I think that calculates out to as if the car was using 3.156:1 gearing...


    I get that from here:
    http://www.miata.net/garage/tirecalcold.html

    That tool is actually Javascript. You can save that page locally to your harddrive and open it up and use if, w/o having to go to the internet to use it.
    Steve your the man!



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

  20. #220
    That is an awesome conversion! Makes the 3.6 feel small...

  21. #221
    OG Moderator
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    Originally posted by c55m8o
    J Irwan, here's what I promised you -- hoped I'd have it the next day, but it's been a couple of weeks. Below are a series of screen captures displaying the analysis of how different rear differential gearing will affect performance done in CarTest2000...


    Pretty interesting stuff Steve...

    Then again some of the calculation I found to be purely math..

    Some of the little different like 17" to 18" might not be that significant in real life.

    But this seems like a good tools to do some calculation before commiting on any mod...


    Good stuff..




    By the way Carl... 13.3x is a great number by any standard...you should be glad.


    The first time I drove E55 (W210) and CLk55 (W208) I was like ...woah..
    the torque and power seems bottomless
    Damn dude...I know how you feel now


    Regardz,
    J Irwan by AMG........Motorsport.

  22. #222
    Senior Member
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    Is this the only real power mod to do to a C43. Have been looking at power mods In another thread

    Cheap power for the C43. Is this really worth it?

    Hmm Keep my eyes peeled you never know if a 55 motor will come along at the right money.
    Better to try & fail than fail to try

    MB ClubUK Forum

    My Local Car Club


  23. #223
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    256
    Im kinda bummed the HPS system has such mixed reviews. I was planning on getting one instead of trying a swap. I just sold my motorcycle so I have the cash now. Such bad press from that company is tough to over look. Guess I will just be forced to be happy with the car as it sits.

  24. #224
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    715
    Originally posted by sig425
    Im kinda bummed the HPS system has such mixed reviews. I was planning on getting one instead of trying a swap. I just sold my motorcycle so I have the cash now. Such bad press from that company is tough to over look. Guess I will just be forced to be happy with the car as it sits.
    You can always upgrade with camshafts,headers,headwork,valvesprings,you name it!



    silver 1998 AMG c43 to C55 convert(293whp/307lbft TQ) ,1999 M3,1995 400 whp eagle Talon Tsi AWD,94 BMW 325i to M332i(M3)conversion

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