Bog between 1st and 2nd gear

[GR8_ASP]

RIW, I understand what you are saying but I do not think that it is the "bog" you are experiencing. What happens is a noticeable reduction in acceleration, almost a deceleration, right after a 1-2 shift and then a return to the expected level of acceleration. It feels almost like you turn off the ignition while accelerating.

Outside of the bog my SRT now (post valve change) feels stronger than the RT/10 (about 420 RWHP).

 

[riwracer]

Your description seems pretty accurate to what I have experienced. I have 600 miles on the SRT and have not gone to 5900 when shifting yet. However, I feel the real torque and power are in a very high rev range.
I am not sure of the reason why I do not get instant power between 1st and 2nd. Again, I agree with your analysis and would hope that some other members could give us some hard SRT numbers. The one time I took my GTS to the track, I ran 12.4 @ 116, Hopefully I will get a chance to run at the same track with my SRT.
RIW


2003 SRT black
2000 GTS black - sold
2002 ZO6 yellow
1993 ZR1 anniv.
1967 427 yellow convert.
2003 AMG E55 coming in June

 

[Vic]

Ron, very good symptom reporting there. Thats a good clue to those who will find the answer. (If PVO is listening)

I'd say its software related, because-

-You can't make it bog by just crossing the RPM range in which the bog is noticed, which means that its not caused by anything that would exhibit itself under a steady state of RPMs, like a bad sensor, or abnormal air/fuel flow dynamics.

-The bog only occurs when going from a high RPM, to a lower RPM, as when shifting under acceleration. This dynamic is fooling the engine management software somehow, and its reacting on purpose, because it thinks it needs to for some reason.

-The bog only occurs at part throttle, (under closed loop operation), and does not occur at WOT, when the PCM is running open loop. This could likely mean that the PCM is adjusting the spark advance, or fuel flow, and that is causing the bog. If the problem occured during open loop operation, then the bog would be seen at WOT as well, which its not.

If I worked at PVO, I'd put an SRT on the dyno, and recreate the bog conditions over and over, and watch the engine management computer in real time, as to what the PCM is seeing from the sensors, and what outputs its sending to the spark plugs and to the injectors. Then I would look at the software program, and determine why its reacting the way it is.

Much of the engine design of the SRT was done using computer modeling, which saves a lot of time and money in engine development. The only thing is, that the real world always has a few more operational parameters that either cannot be accounted for on the flow bench, or could not be anticipated.

I'm sure they will find it soon. (I hope they are listening). Good job, Ron, with your accurate reporting.

 

[Russ Oasis]

I have the bog under the exact same conditions that Ron described above. It occurs only in the shift from first to second under moderate acceleration. It is more like someone starved the engine out for a second or two. I think that it's important that we get to the bottom of this. On a different note, anyone have interior rattles in the car?

 

[Hans Christian]

Has this issue been elevated to PVO - Joeseph ???

Any comments - reprograming of PCM ???

??? what is going on here

 

[Dyno Dave]

I've been reading.

 

[Hans Christian]

Dyno Dave,

What is you what is your take on this - any solution from your side

 

[Russ Oasis]

If I had to take a wild stab at what it is, I'd say that the engine controller has a bug in it that accidentally reduces the amount of gas going to the engine when certain engine / vehicle operating conditions are met (those described by Ron above). I'd be curious to know how many people have experienced this bog.

 

[unclgreggy]

It happened to me last week, several times.I figured others might be having the same problem. glad I'm not alone. Haven't said anything because my car has been sitting in the garage from the rain!

 

[BlackVenom]

I experienced it when I drove an SRT-10 three weeks ago in Texas. The car had less then 50 miles, but it was a warm sunny day. The dealer's Viper Tech said this was the first he had heard of it. I showed him this thread and he noticed the original ones who reported the problem were from Florida. As more people drive their cars in warmer weather, there has been an increase in the number of reports.

 

[CHAD]

Sounds like a slight tuning issue in warmer ambient temps. My wife's Mercedes had a similar problem that the service tech said many cars were experiencing. They called her back a while later with a patch from DC that cured the problem.

Chad

 

[unclgreggy]

Took a ride today for the first time in like a week. This "bog" problem is very annoying. I hope they have a fix for this soon.

 

[Russ Oasis]

While I can't be positive, I don't necessarily think that the bog has to do with hot weather. All of us tend to drive our cars more in warm weather and I think that might have something to do with it. It has to be computer related because it is either an ignition or fuel issue.

 

[riwracer]

I had my SRT out tonight, and again at a partial throttle, 4000-4500 rpm, it felt for an instant like it was fuel starved. This seems to go along with Ron's assessment and other explainations that there may be a sensor cutting off fuel for an instant. The power comes right back upon pressing the throttle to the floor. I never realized that there was a red shift light at about 5800 rpm. On seeing this light I shifted from 1st to 2nd, where I would have shifted anyway, and all four times that I did this tonight, the car accelerated perfectly. The tires chirped and the care leaped forward with great power 4 out of 4 times.

This leads me to believe that there is a slight program glitch at a lower rpm and a quick shift at partial throttle only.

Does anyone else use the red shifter light for maximum shift....I have not heard any comments about this.

riw


2003 SRT black
2000 GTS black - sold
2002 ZO6 yellow
1993 ZR1 anniv.
1967 427 yellow convert.
2003 AMG E55 coming in June

 

[Vic]

To just say its computer related is an over-simplification.

There are dynamics involved, between the closed loop control of the fuel, and spark advance, and the intake's flow characteristics. It may not be just the software parameters, nor just the mechanical design of the intake, but put the two together, and under certain conditions, the software either over-compensates for something, or it can't react properly. To find the answer, you first have to find out what software flags are ineffect at the time of occurance. ie Is it retarding the spark? What is the flow rate to the injectors at that instant? After these points have been identified, you then have to look at the program, and see why the outputs were affected in the way they were, in other words, was the MAP sensor seeing a variance in the manifold pressure, and what did the program tell the outputs to do with that information? The program may be written correctly, but the MAP sensor may not have the right characteristics for the changing pressure/vaccum in the intake. So the dynamic of the mechanical components in conjunction with the PCM program must be examined.

When you are troubleshooting processor-based, software-driven electro-hydraulic-mechanical systems, you must never tell yourself what the problem is, otherwise you have "married the vein", to quote an old miner's term. (Instead of looking for evidence for gold, the miner starts to try to find reasons why he thinks there is gold in the mountain, and everything he sees convinces him there is gold there. He is said to have "married the vein")

The evidence must be studied without a pre-conceived notion of the cause.

First, find out what the software is doing with the inputs, and outputs. It may not be malfunctioning at all! Could still be a mechanincal based issue, maybe with transient compressions and rarefractions in the intake air flow, that the closed loop control cannot respond to.

I'm so d*mmm curious to find out what is causing this, I almost wish PVO would let me come over there and work on that with them!

I love a mystery!

 

[GR8_ASP]

When you are troubleshooting processor-based, software-driven electro-hydraulic-mechanical systems, you must never tell yourself what the problem is, otherwise you have "married the vein", to quote an old miner's term. (Instead of looking for evidence for gold, the miner starts to try to find reasons why he thinks there is gold in the mountain, and everything he sees convinces him there is gold there. He is said to have "married the vein")

The evidence must be studied without a pre-conceived notion of the cause.

Great perspective. I believe the philosophy applies to just about every type investigation.

 

[MiamiJeff]

Anyone hear any official or semi-official explanation and a fix? Attention PVO: Please fix in next few days since I'm in "I" status. Thanks!

 

[GR8_ASP]

Update: I experienced the bog today after a 2-3 shift. Same resulting engine speed so the condition is not dependent on what gear you are in. It was warm out when it occured. Still not certain there is a temperature factor, but I have felt it much more during warm weather.

 

[Nsane1]

Phew, I thought it was ME, and that I already blew out my clutch or synchos with 2500 miles (or that I can't shift the car!).

Anyways, this started happening recently, so could be miles, or could be temperature. It happens only to me from 1 to 2, and when I am driving "normally" (moderate to high accel)

 

[Russ Oasis]

Good News! I have spoken with the guys at DC and they are on it! While they couldn't replicate the bog in their car, they have already started investigating and if they can't get it to happen, they will put an IBOX (a data recorder) on one of our cars to find out why it is happening. They will clearly get to the bottom of this one. And not to be too much of a cheerleader, but how many car companies can you call the engineers DIRECTLY and actually find someone who believes you and cares? For all the complaining and whining I read on the boards, I think that DC is really responsive to us.

 

[Leonard Knight]

That is good news. It only happens on occassion but it is hard to explain to someone riding with you. Can't wait to hear what is causing it. Thanks for the extra effort to find out.

 

[Vic]

Well, I would have called them myself, you know, but uhm, (cough), uh, ,,I don't have an SRT!

Hope they figure this one out!

 

[Dyno Dave]

Since I'm the dyno rat and rarely drive the cars (I have more work than I can handle in the engine test cell) I have not experienced this condition.

What needs to happen is find a car that exhibits this condition and dcap (data capture) the event. When the conditions can be determined under which it occurs I can then replicate that condition in the test cell if necessary. Without experiencing it I could only speculate and probably fan the flames of this thread.

 

[Russ Oasis]

Dave, That's what DC is going to do.

 

[Vic]

Dave, That's what DC is going to do.

I could be wrong, (I know thats hard to beleive), but I think Dave has something to do with DC. True, Dave?

 

[Dyno Dave]

That's true. I've been flogging the Viper engine now for over 2 years.

 

[GTS Dean]

There are definitely some things that can't be learned with the engine bolted to a stand, or even in a car on a rolling chassis dyno. Things like oil starvation under heavy lateral G, or top end oil load-up under heavy braking, for instance. Issues like that need real track testing. Preferably by the sort of people that will be flogging them in the real world.

 

[Vic]

That's true. I've been flogging the Viper engine now for over 2 years.

Cool job!!

 

[Mac Viper]

650 miles and no noticed bog. I will be more vigilant in noticing the bog in the future although if it feels as though the fuel is shut off I believe I would have notice it already. The bog I feel is off the line, it takes about 2500 RPM to get any kind of launch. This is about 600 more than either my other cars. Below 2500 it feels sluggish. Could this be part of the same issue or tire size related.

 

[Russ Oasis]

Off the line is something completely different. You would notice this if you had it. It occurs when shifting and is a definite "bog."