Highly Tuned Viper

[SUN RA KAT]

Is it normal for Roe Supercharged, heads, & cam or other highly tuned Viper using a VEC2 to get stuck in a closed loop where it will start but have to be shut off and restarted before it can drive on the street?

And what is the solution?

Thanks.

----------------------------------------------------------------------------

Kenny

Larry Macedo has had my Viper back since September 8, 2006 and is correcting all problems with it at this very moment. The last time I drove my Viper and it ran right was November 13, 2005 just before it went to Larry Macedo. Larry Macedo promises to have my Viper running right and returned to me sometime in November 2006. Thanks.

 

[FE 065]

I think the answer is going to be a big fat no.

Where did this come from?

 

[banton]

The title should read highly modified Viper, not highly tuned Viper.

 

[Joseph Dell]

Re: Highly Modified Viper

When a car starts, it is in closed loop until it warms up. nothing you can do about this. It is seconds or minutes depends on the sensors. And when in closed loop, it can be 5-10 min before it goes open loop.

Is it normal to NEVER come out of closed loop? No. But it sometimes takes a little while.

And ODBII reader (like the one sean sells) can help tell you when you go from closed to open loop.

JD

 

[Casey]

The title should read highly modified Viper, not highly tuned Viper.

I would agree!

 

[SUN RA KAT]

The title should read highly modified Viper, not highly tuned Viper.

I would agree!

Me, too.

Sorry about an inaccurate title.

 

[SUN RA KAT]

I think the answer is going to be a big fat no.

Where did this come from?

Actually it is an old issue that I had forgotten about and I sent an Email to Larry Macedo for him to add to the list of what needs to be fixed on my Viper earlier today. Larry told me about my Viper having this problem when he delivered my car to me on July 1, 2006. So much else has gone on with my car that I had forgotten what a pain it was to have to start my car and let it run for a little bit then turn it off and restart it before it would stay running when I would try to drive it.

I was trying to be serious here to see if this is normal with highly modified Vipers and if so, see if anyone knew of how to fix it so I could pass the info on to Larry Macedo while he's fixing my Viper. I'd like to help Larry with serious suggestions on any problems he needs to fix.

 

[KenH]

Re: Highly Modified Viper

When a car starts, it is in closed loop until it warms up. nothing you can do about this. It is seconds or minutes depends on the sensors. And when in closed loop, it can be 5-10 min before it goes open loop.

Is it normal to NEVER come out of closed loop? No. But it sometimes takes a little while.

And ODBII reader (like the one sean sells) can help tell you when you go from closed to open loop.

JD

Actually, I think you have your terminology backwards. Closed loop is when the car is using the O2 sensors to adjust A/F to 14.7. Open Loop is when the car adjusts A/F according to built in A/F tables. The car starts up in Open Loop until it warms up for a couple of minutes and the O2 sensors have a chance to come up to operating temperature. At that point, the car goes into Closed Loop and stays in Closed Loop until you go WOT, at which point it goes Open Loop again. Kenny, if your car will not run right under normal street driving, it sounds like it could be stuck in Open Loop when it should actually be in Closed Loop mode. O2 sensor problems can cause this, but that will usually throw a code eventually.

A faulty TPS sensor might also cause this I suppose. I had the opposite problem where my car would not go into Open Loop during WOT and it was the TPS sensor (actually, the thottle plates where not adjusted correctly, causing the TPS sensor to never reach the minimum WOT voltage)

 

[ROGUE]

Re: Highly Modified Viper

For the love of god man, you've spent sooo much time and $$$ dicking with this thing i'm surprised it hasn't totally ruined the whole experience for ya.

Honestly it sounds like the vec2 just isn't cutting it. Throw an aem in there and most of these silly issues will go away immediately.

 

[SUN RA KAT]

Re: Highly Modified Viper

Larry did find one of my O2 sensors was shorting out - maybe that fixed the problem I'm asking about here as well as the fuse blowing problem.

Thanks KenH and Joe Dell!

 

[SUN RA KAT]

Re: Highly Modified Viper

For the love of god man, you've spent sooo much time and $$$ dicking with this thing i'm surprised it hasn't totally ruined the whole experience for ya.

Honestly it sounds like the vec2 just isn't cutting it. Throw an aem in there and most of these silly issues will go away immediately.

I hope it hasn't totally ruined the whole experience for me, too.

I am sick and tired of having problems with this project. I want Larry Macedo to make my car what he promised it would be when we discussed him undertaking this project. I know I'm not going to get the "at least high 700's in power" that I was promised and based a lot of my $28,000 spent on ($6,500 heads, $3,500 fuel system, $2,000 roll bar/cage, etc.), but I sure as hell want my car to run right on the street and I want to give him any legitimate ideas on solving the problems with my car. I'm not sure how much more he needs to do, but he did promise he would have my car done right and delivered to me before the end of November 2006.

It's up to Larry Macedo to decide what he wants to use to make my car run right. Most people I've talked to say the VEC2 can tune it to run right with what I have in it. Some people say use the AEM. Larry can decide which he wants to use. I don't care as long as my car runs right when I get it get it back later this month.

----------------------------------------------------------------------------

Kenny

Larry Macedo has had my Viper back since September 8, 2006 and is correcting all problems with it at this very moment. The last time I drove my Viper and it ran right was November 13, 2005 just before it went to Larry Macedo. Larry Macedo promises to have my Viper running right and returned to me sometime in November 2006. Thanks.

 

[GTS-R 001]

Re: Highly Modified Viper

Good Luck Sun Rat

 

[Joseph Dell]

Re: Highly Modified Viper

Ken -

thanks for reminding me. I explained that one totally @ss-backwards. I always mix them up that way too. open vs. closed. I got the concepts right but the terms backwards.

Thanks for straightening that up!

JD

 

[Shelby3]

Re: Highly Modified Viper

Kenny, do you have any details on your upgraded fuel system?

 

[ViperJoe]

Re: Highly Modified Viper

Kenny, could that have been a contributing factor to your initial drivability issue(s)?

Hope it all gets sorted out!

 

[SUN RA KAT]

Re: Highly Modified Viper

Kenny, do you have any details on your upgraded fuel system?

55 pound injectors, pump, filter, regulator, one-way valve, hose, & fittings - all for $3,000 plus $500 for installation. Needed for "at least the high 700's in power". Questionable if needed for 721 rwHP that is the current reported maximum power achieved by Larry Macedo so far. He is now promising the mid 700's in power, but hasn't dyno tested it yet after over 2 months back in his shop as far as he reports.

 

[SUN RA KAT]

Re: Highly Modified Viper

Kenny, could that have been a contributing factor to your initial drivability issue(s)?

Hope it all gets sorted out!

A lot of things were probably contributing factors to all my drivability issues. The shorting O2 sensor probably caused the fuse for the PCM to blow and could also be responsible for having to restart my car in order to drive it each time it started cold. Maybe even it contributed to the surging and bucking and high idle hang up. I'm not an expert - that's why I made a post here. Larry's the expert, but sometimes even experts need help - Vipers are very complicated machines. It has been over 2 full months that he's had my car back.

I hope Larry corrects all my Viper's problems so I can have my Viper back and running right on time (by end of this month).

 

[dansauto]

Re: Highly Modified Viper

yes you will need a fuel upgrade for anything over 700 Hp. The stock system in good for mid 600's but any hicup and you could damage the motor. 55# injectors should be easy to tune with a vec 2

 

[ROGUE]

Re: Highly Modified Viper

yes you will need a fuel upgrade for anything over 700 Hp. The stock system in good for mid 600's but any hicup and you could damage the motor. 55# injectors should be easy to tune with a vec 2

Says who? I've put 800rwhp through a setup with 55# injectors, fuel rails, and just a boost a pump. Granted it was a turbo car, but it can be done if it's setup right.

At any rate thats not the point of this thread. Hope everything comes out well and you can get back to enjoying the car Kenny.

 

[418viper]

Re: Highly Modified Viper

Is close loop also called "limp home mode" where you can still drive the car if a sensor or sensors fail?

 

[Tom F&L GoR]

Re: Highly Modified Viper

No, closed loop is normal, desireable, and what you want to happen. It means the engine runs, sensors sense, and provide feedback to the brain on what is happening. That "closes the loop." If sensors fail or do not give feedback, the brain guesses on a few settings to still allow the engine to run. If it's really bad, the brain more or less goes to a fail-safe state to allow you to "limp home."

Open loop also happens in some systems at full throttle, but then not because a sensor failed.

 

[Jack B]

Re: Highly Modified Viper

418Viper:
If the sensor shows a continued lean condition, the PCM will protect the car and go full rich, it does set a code when this happens.

Ken:
If the O2 sensor is bad, it could cause an erratic idle and/or increase the low speed rpm, here is what happens:

a. If the O2 output voltage is low the PCM thinks the car is lean.

b. The PCM then adds fuels and if it stays lean it will again add fuel, hence, your surge is created. If you are at idle it will also add timing.

c. If the O2 sensor then intermittantly starts working the PCM is adding and subtracting the fuel and creating the bucking. Note! - all of our cars will have this to some degree. When you add larger injectors and forced induction the manifestation is exacerbated, therefore, with a bad sensor the whole scheme is magnified (bucking/surging).

A bad O2 sensor is farily easy to find with a scan tool, all you have to do is monitor the O2 output voltage. You have to ingore the 02 voltage till the car is in closed loop, it takes about 90 seconds (from a cold start) and the coolant temp must be at approximately 170 degrees or higher. Both conditions must be satisfied to go into closed loop. In general closed loop is only encountered at start-up and when over 90% throttle.

 

[dansauto]

Re: Highly Modified Viper

yes you will need a fuel upgrade for anything over 700 Hp. The stock system in good for mid 600's but any hicup and you could damage the motor. 55# injectors should be easy to tune with a vec 2

Says who? I've put 800rwhp through a setup with 55# injectors, fuel rails, and just a boost a pump. Granted it was a turbo car, but it can be done if it's setup right.

At any rate thats not the point of this thread. Hope everything comes out well and you can get back to enjoying the car Kenny.

not to hijack, but-you a stock gen2 fuel pump will not handle the fuel requirments for 800Hp. If you contnue to run at those levels you will have problems Various tuners have documentated this.

 

[SUN RA KAT]

Re: Highly Modified Viper

418Viper:
If the sensor shows a continued lean condition, the PCM will protect the car and go full rich, it does set a code when this happens.

Ken:
If the O2 sensor is bad, it could cause an erratic idle and/or increase the low speed rpm, here is what happens:

a. If the O2 output voltage is low the PCM thinks the car is lean.

b. The PCM then adds fuels and if it stays lean it will again add fuel, hence, your surge is created. If you are at idle it will also add timing.

c. If the O2 sensor then intermittantly starts working the PCM is adding and subtracting the fuel and creating the bucking. Note! - all of our cars will have this to some degree. When you add larger injectors and forced induction the manifestation is exacerbated, therefore, with a bad sensor the whole scheme is magnified (bucking/surging).

A bad O2 sensor is farily easy to find with a scan tool, all you have to do is monitor the O2 output voltage. You have to ingore the 02 voltage till the car is in closed loop, it takes about 90 seconds (from a cold start) and the coolant temp must be at approximately 170 degrees or higher. Both conditions must be satisfied to go into closed loop. In general closed loop is only encountered at start-up and when over 90% throttle.

Jack - Thanks for the info. My car also would throw right and left banks running lean codes intermittently usually under light throttle. It sounds like Larry Macedo knows his stuff in finding the intermittent shorting O2 sensor and hopefully this fixes several problems at once.

 

[Tom F&L GoR]

Re: Highly Modified Viper

To everyone searching or suspecting a bad O2 sensor:

They can be bad, but not "caught" by the OBD. OBD needs to see the problem for a certain amount of time and if the malfunction happens for less time, it is not logged or does not throw a code.

I had both O2 sensors bad (OBD-1, '94) and not until I drove around with a high-zoot real-time scanner did I see it. Because the sensors functioned again within a certain time (the malfunction had to happen continuously for several seconds) and gave an acceptable signal within the time window, it never threw a code. Driving around you can see it, though. Hopefully OBD-II has a shorter window...

 

[ROGUE]

Re: Highly Modified Viper

yes you will need a fuel upgrade for anything over 700 Hp. The stock system in good for mid 600's but any hicup and you could damage the motor. 55# injectors should be easy to tune with a vec 2

Says who? I've put 800rwhp through a setup with 55# injectors, fuel rails, and just a boost a pump. Granted it was a turbo car, but it can be done if it's setup right.

At any rate thats not the point of this thread. Hope everything comes out well and you can get back to enjoying the car Kenny.

not to hijack, but-you a stock gen2 fuel pump will not handle the fuel requirments for 800Hp. If you contnue to run at those levels you will have problems Various tuners have documentated this.

Really? well after a few thousand miles, countless 200mph runs, and incessantly pounding on the car it hasn't missed a beat. If I notice via the aem datalog that the fuel pressure starts to drop or the injector dutycycle is overly high I'll deal with it. But up to this point it's been working flawlessly.

 

[Jack B]

Re: Highly Modified Viper

Tom:

I agree 100%, if typically will not throw a code, however, they are easy to troubleshoot, you just have to watch the voltage and that ain't hard. The comment on the code relates to a cycle where the car stays in the lean condition for xx revolutions, the PCM always sets a code at that point. For some reason the car can run rich forever without setting a code and this is the most common failure mode.

If you want to diagnose the O2,it should go right to zero volts on de-acceleration and should not go above 1 volt any other time(or seldom). When you log both at the same time on a scanner you can juxtapose those data points pretty easy and watch for the one that has a slower cycle rate. NB's are basically switches and they are easy to follow.

I have a couple of scanners, for quick and dirty I use a Palm bluetooth (no cables needed) based scanner (Auto Inginuity)which is relatively slow and it picks up the above anomolies very easy even with a very slow refresh rate.

You may be interested, Innovate just annouced their OBD logger. The limitation on a good scanner is when you are at WOT, most scanners have a single data stream and the more channels you record the more it slows down. As an example I built a ciruit to log timing because the scanner could not keep up which the real-time advance output at WOT. The Innovate technology is going to use parallel/dedicated conductor pairs and samples the OBD 12 times per second, therefore, can log any enhanced OBDfucntion in realtime. The have announced the OT-1 logger, but, have not posted the information on the commercial product yet.

 

[grcforce327]

Re: Highly Modified Viper

To everyone searching or suspecting a bad O2 sensor:

They can be bad, but not "caught" by the OBD. OBD needs to see the problem for a certain amount of time and if the malfunction happens for less time, it is not logged or does not throw a code.

I had both O2 sensors bad (OBD-1, '94) and not until I drove around with a high-zoot real-time scanner did I see it. Because the sensors functioned again within a certain time (the malfunction had to happen continuously for several seconds) and gave an acceptable signal within the time window, it never threw a code. Driving around you can see it, though. Hopefully OBD-II has a shorter window...

That's when it's time to go to "arm movie" mode on your scanner,and "lock-n-load"!!!!

 

[99 R/T 10]

Re: Highly Modified Viper

I have been told by a smart guy(1tony1 ) that the O2 sensors should be replaced on a regular basis(maybe once every 2 years). Sounded to me like solid advice and this thread kinda supports that thought.

 

[1TONY1]

Re: Highly Modified Viper

I have been told by a smart guy(1tony1 ) that the O2 sensors should be replaced on a regular basis(maybe once every 2 years). Sounded to me like soldi advice and this thread kinda supports that thought.

I think that's when we were discussing about sometimes running leaded fuel.