I have a 94 E500 with Renntech 1st gear, K&N filters,& PAD performance chip. I recently noticed what seems to be a flat spot in acceleration when the car shifts from 1st to second under full throttle acceleration. This car definitely pulls harder in the upper rpms after I installed the chip. What I can't figure out is: is this flat spot just normal but accentuated because the car pulls better in the upper rev ranges( a friends E500 w/o a chip seems to have some hesitation after shifting but not as accentuated as mine); is it something in the adjustment with the 1st gear installed; or is it caused the the chip and could it be solved with a new chip. Anyone experience what i'm talking about? I don't seem to have that flat spot shifting from 2nd to 3rd. Is it possible the gear ratio between 1st & 2nd is so wide that the performance chip accentuates what I'm noticing.

Can you define "flat-spot"?? Do you mean the car "feels" like it's not accelerating at all?? And at which RPM do you feel this?? From all the DOHC V8s I have driven, it seems that the engine is "flat" from idle to about 1500rpm, and starts to push around 2k, and jumps at around 3000 - 3500 all the way up to redline....

Andy Kuo

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1992 Mercedes-Benz 400SE
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2002 Acura TL Type S
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Other than the first gear start, my car has the same mods. But my car pulls like a scalded dog throughout the rev range.

Please try to describe your situation in more detail, because I think many of us aren't quite sure what you mean.

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

Thanks for the reply. What I mean by a flat spot is when the car shifts from 1st to 2nd under full throttle which is at about 6300 rpm I notice a distinct softness in acceleration in 2nd gear for about the first 500-700 rpm then it takes off like a scalded dog up to the rev limit.
I had another friend with a 92 500E with no chip drive the car and he definitely noticed what I was talking about. It is hard to describe.

Under full throttle, and change gear from 1st to 2nd..... I think I get it now... it feels more like the gearbox is "slipping" on purpose?? Some kind of compesation for a smoother ride?? But backfires on us drivers when driving aggressively....

Is that what you experienced??

Andy Kuo

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1992 Mercedes-Benz 400SE
http://members.shaw.ca/AKRY/W140_Side.gif

2002 Acura TL Type S
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I ran through the gears this morning and do see what you are talking about.

The roads are wet today but still, there is a slight (half second) delay when shifting to 2nd that I never noticed.

Maybe this can be adjusted via the Bowden cable? My understanding is that this will only help if the shift is at a lower than redline point. This thread may provide some information and insight to the transmission's behavior? 500E Transmission Woes?

Does anybody think this might help?

YES..you are beginning to understand what I'm talking about. I can't tell whether this is a normal "flat-spot" that is accentuated because the car has so much more upper end power with the chip or the transmission is "slipping" on purpose or due to some problem. Also of concern is if the chip has a faulty "fuel-mapping" problem that is occurring although I doubt this. Just thought I would throw this problem out .... hoping someone who has installed the PAD chip might have noticed the same thing. I have noticed the same phenomena in an unchipped 94 E500 but not nearly the magnitude as in mine.

Hm...my W140 has the same behavior, too. It's most obvious of such behavior when engine is close to its redline. The cable adjusting method mention by Roas might help.

BTW, after some aggressive driving, do you find the tranny refuse to shift up?? Or any difference in tranny behavior at all?? My tranny would refuse to shift up from 2nd to 3rd to 4th even if I keep throttle at 1/3-1/2, and will keep pulling the rpm up unless I ease off the trottle to about 1/4(or less).... however, if I don't keep the throttle 2/3 down, tranny will shift from 1st to 2nd at around 2000 rpm.....

Andy Kuo

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1992 Mercedes-Benz 400SE
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2002 Acura TL Type S
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My car acts entirely normal other than the hesitation I mentioned. Today I was able to quantify it a little better. The car shifts out of 1st @ 6300 rpm and drops to around 4800after the shift and that "flat spot" seems to occur as it accelerates from 4800-5000 rpm, then it takes off like a scalded dog. This may be a normal trait of an E-500 & nothing may be wrong. I would be interested in any other feedback.

How about ASR? Do you have an ASR defeat switch? If not maybe ASR is interupting power supply ever so slightly on the 1st-2nd gear change? I am sure that there is the chance of some wheelspin at the gearchange, maybe enough to cause the ASR to kick in?

David Hendy
'92 500E 65k miles

Good thought about the ASR, however the ASR light does not come on so I don't think that is the problem.

Just so everyone knows, these cars retard their timing at gear-change time to facilitate a smoother shift. However, once the new gear's engaged my car resumes its pull-like-a-train behavior (the primary reason I love my car!).

Keep us posted.

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

There is a timing "blip" when the car shifts, but it is so brief that I doubt anyone could detect it. If the torque difference is big enough and you do get wheelspin, only then does ASR gets involved. As far as just an engine power curve, virtually every M119 I have driven has displayed a bit of a flat-spot in the torque curve between about 1700rpm and 2700rpm. It isn't lacking power by any means, but the power increase is not linear through there. Once you hit 3000, and especially 3500 when the valve timing advances, it goes crazy right up to (even slightly past) redline...

I've heard from a reliable source (c'mon Michael) that some of the aftermarket chips help with that flatspot, but I've never been able to get personal verification.

If your car is shifting short of redline, it could feel like there is a flat spot that isn't there. Gear ratios are chosen to work with the engine's power curve...if you are shifting outside of spec, you will lose some performance. The bowden cable is an easy adjustment on a M119 W124. Look just behind the airbox and the firewall. You should see a metal rod with two press-on ball/socket ends. By adjusting the length of the rod you can adjust the shift tendencies. Start at spec (the two nearby plastic arrows lining up) and work from there. I recommend about 1 full turn past spec for daily driving. Up to 2-3 turns past spec for track. The motor will not go past redline (at least no more than any other M119 going to 6300 or so) no matter the adjustment. However, if you want to know for sure, just shift the car manually. Hold it in 1st with the shifter until 6000rpm then tap the shifter to 2nd, then bump up to 3rd. Do this all just right and it should only take you about 14 secs tops. At least the testing will be fun...

Hope this helps,
Lee

Lee:

What tool is needed to make the Bowden cable adjustment?

On second thought, perhaps I will ask my technician/mechanic to show me, in person. I'm not yet comfortable enough with my mechanical prowess to risk a "complete bolo!"

Thank you,

Slow-acting O2 sensors can cause some funny stuff...check for codes. I'm not sure that a somewhat slow-reacting O2 sensor would trip the "check engine" light, but it's worth investigating (I believe a MBZ "HHT" (Hand Held Tester) can track the O2 sensors' characteristics. But regardless, the O2 sensors are off-line if under full throttle (and you've depressed the switch under the gas pedal).

My car, under 2/3ds throttle, surges a slight bit; it's likely either carbon in one cylinder continuing to cause that cylinder's timing to be retarded a bit, or I need to do my O2s. They've never beeen done, and I'm at 80+k mi. These are the guesses of my tech, who's an MBZ Shoip Foreman and drives a 500E (and a Viper of all things! Think he likes power?!?)

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo