JDM has supposedly warned about doing the kickdown at 60ish mph. I have read others that say that it is as hard on the engine as 10 1/4 mile runs. Could some of the truly knowledgable tuners here care to shed some light on why? Here is my theory just for grins...


JDM warns against doing it, but I haven't really heard anyone else say it is bad on the motor other than an occasional post warning not to do it. All I can figure is that you are INSTANTLY at max boost and near max rpms and maybe it causes a breif lean condition or something. I know that the computer chip makes X adjustments to A/F per second or whatever, but I don't know how many. I guess it is logical to say that the computer might get behind the curve trying to catch up to the instant demand rather than building from a stop.

The way I would see it is Imagine going from a 2000 rpm very light throttle to sudden FULL throttle 4500 or so rpms. The engine needs a lot of fuel instantly according to the new maf readings. Maybe the computer makes its first adjustment to compensate and then realizes that's not enough and makes another and so on. Obviously this is happening very fast, but how long does it take the system to reach equilibrium? Just long enough to mabe get one big ping and toss a rod?

Theoretically, starting from a stop is a gradual but still quick climb, but the maf/computer isn't having to compensate from one extreme to the other.

Again, this is just a theory, and I don't know why people say the kickdown is hard on the engine.

Ken

 

Can't answer your question exactly.

But I do know it's very hard on the 2nd gear clutchs in the tranny.

Also I spent 6 years in FEAD engineering. And can tell you that a sudden acceleration causes very high stresses on the FEAD components and especially their bearings. (front end accessory drive)

It's just physics 101. Any sudden acceleration of a mass requires a high load for a short period of time. And these engines have so much torque that it places a big load on any/all related parts & their systems.

WOT

 

anytime you drop the engine it's going to be hard on it,

i personally have 29000 miles of hard driving and about 200 1/4 passes

i would definately recommend a safe tune if your going to be getting on it

 

I think what Jim is trying to say is when the tranny kicks down and you are WOT it puts a LOT of stress on the motor all at once possibly breaking the stock rod.
Jim or any tuner does not want people blowing motors.Not good for buisness and just not good period.
Really the only time Jim has said anything to me is when we discussed a 8# lower pulley on a stock motor.He is concerned about daily driving a 8# pulley on 93 octane,a street tune and kicking down the tranny under WOT.
I for one am glad to have a tuner that cares about what happens to my truck( I am not saying JL and Sal do not care) I am sure they do the same.
The stock motor is only so good.we are putting a lot of strain on it already and I think maybe Jim sees the 8# as the possible breaking point for the stock motor.
Of, course only JIM@JDM can answer this question proprly as he is the one you are referring to making the statement.(again,I am sure JL and Sal know the answer also).
Boy it is not easy being politically correct when we are talking about tuners.The last thing I want is a tuner war thread.

VINNIE

 

well if you look at very many dyno runs and torque curves, that statement is self explanaitory. It doesn't do the tranny (2nd gear) any good either.

 

remember,,, these days even too much water is a bad thing,,,,,

~Toast

 

Also the hard KICKDOWNS have been known to cause problems with timing chains breaking on the modular motors as well......

 

I got the same info from JDM and have just adhered to it. I took the advice mostly as a "tranny protection" thing but the engine discussions above make sense as well.

 

 

at least NYC has enough water now. They lifted the restrictions on car washing yesterday. Ya Hoo!

 

There are millions of lightning strikes every year around this great country of ours with 1k or so coming from my truck alone

Maybe i should take the blower belt off every time i drive her or maybe life is too da*m short to worry about a little fun

 

I like living with that in mind....

 

Just to make it clear: This is in no way a bashing or tuner war. I am not inviting anyone to say the satement is BS or that he is more concerned about it than other tuners.... I was curious the thougts of other users and tuners as to what the potential breakage areas are and what the relationships are to tuning. I.e. is it A/F or is it merely a function of instantaneous mechanical stress -- or both.

Thanks for the answers, guys. I appreciate it.

Ken

 

it's obvious it's a factor of all things,

if your tune's bad that's #1

obviously if you got a bad part or weaker part, something could go wrong,

i had a coil pack go bad on my 99 cobra with just a few thousand miles on it, but never had any other problems besides that

things just break

the more power you make outside the "factory specs", the harder it's going to be on the engine

 

I wonder if we leave the shift points stock, and/or leave the "4 cylinder/torque reduction" in the program if this would be an issue...!?

Driving at 60 mph, it's nearly IMPOSSIBLE to avoid this downshift to make a pass on a two-lane road...?

How do you guys "avoid" it?