Why it is hard to produce power in the Rockies!

[Coloviper]

TR930;

Looking at your last dyno run graph you posted, it would appear your belt is slipping or something, which is why you have oscillations in the boost profile. That could be why you only added, what 1.25 #s of boost with the pulley change. With that 10 psi sea level pulley on there, you should have been up around 7.5 to 8 psi up here at altitude with that pulley change.

As far as the rest, I am just not sure. The damn FMU has killed me on my other cars (granted they were Mustangs) and it is just a band aid solution to the real problem. The real solution is as I found out on my Mustangs and would assume it is the same for any hi-po car up here including the GEN III Viper is to:

1. Dump the FMU, Paxton fuel pumps (on top of the fuse box) and get rid of the split second boost retard box.
2. Upgrade the stock Viper fuel pumps at the back (both in-tank and rail mount , if it has them)
3. Upgrade the Fuel Injectors to appropriate sizes. Fuel lines should be good enough to handle the extra psi and flow volume.
4. Go with an SCT Custom Tune for up here in the Rockies and at this altitude.
5. Add headers as I saw a large increase in torque on my Viper when I did. Your torque numbers should be higher.

Even though SCT is pulling out of the new GENs and later model tuning for most all cars, they are apparently still supporting 2006 and older Vipers (amongst other older cars), which I just found out a few days ago so I was wrong a while back. SCT is the only tuning software who supports Viper, I believe.

Would be good to contact SCT and see if they could send their local Rockies rep with you to the dyno shop and see what can be done. That is how I would approach it and what I was planning on doing if I took the plunge on my car up here.

The graph you attached shows you are pretty rich and while that is saving it from detonation, that level of richness may cause issues down the road with the piston rings. You need to be careful with that.

This thread is a good one as the issue has been around for a long time and it needs to be solved once and for all. Altitude tuning *****! I hope what I posted helps in some way. It does seem like only shops in Colorado can appreciate the gravity of the situation and a good speed shop in Denver (like Eddie's) should know how to handle it. I know they have not tuned Vipers before but the reality is no one has at this altitude. If you cna get SCT on board, that is the only thing holding you back from solving this thing. SCT is your key.

 

[TR930]

You know, I thought about all this and spoke with Glynn P. About it and honestly I am going to put the stock pulley back on and call it a day. Gonna keep the car in the garage on hot days as it runs really rich. I can live with leaving all the power on the table, 5lbs boost and running on the rich side ( on the dyno) is okay with me. I am sure on the road it leans out some with real airflow and I might throw a set of headers on and that should lean it out some more. I am running the 6:1 disk in the FMU! Altitude is a tuning ***** and I am not interested in pouring alot of dollars into it. The car runs good. You were right, there is no consensus or real knowledge depth of tuning this car at altitude and some think there isn't that much difference, well there is a big difference.

So, unless someone has a brainstorm here as to what my problem or issue is as to why it might be rich, I'll stick to the DC tune and Paxton setup. I am convinced at this point it is related to the lack of air density and its' effect on the heat generated by the Paxton. Ambient air temps play a role here as well. Hell, i am trying to figure out the effect of less boost because of less air density on the fuel pressure since my fuel PSI must be lower since my boost is lower.

I ordered the SCT tuner but honestly don't know what good it's gonna do. The car is VERY sensitive to temperature at this elevation with the blower. This is where I am mentally right now.

 

[Coloviper]

I hear you TR930! This has been my hesitation in buying the Paxton blower for my car up here. The success is all in the tuning. This is why I was pushing so hard for a Screw Type of blower package or the Magnusson package for the Viper. Getting rid of that FMU is the key and the rest is the right fuel system and tuning.

Before you give up totally, I do think you are close and I would talk a ton with SCT before giving up the approach.

 

[TR930]

Unless the SCT guys want to donate their time then I don't know if I am up for it. I honestly think that even with scrapping the FMU you will have variances in power AND boost depending on temperature. I will try and validate this with another dyno run at a lower ambient temp. BTW Glynn nor the guys at DC think the belt is slipping, the undulations are due to how the dynojet measures/samples boost readings. I am convinced that at lower amb. temp I will run a higher boost. If true, how can you make tunes that adjust for boost AND ambient temps? I don't think you can. I think all can hope for is to get an "average" tune and be happy with it. I think the way it was setup originally was that tune/pulley.

What I would love to know is what does running a lower PSI at boost cause the ECU to do to compensate? If I was running 8lbs at SL with 6:1 fmu then I had additional 48lbs Psi fuel at max boost. Now I run 5-6 lbs boost with same 6:1 disk for additional 30-36 PSI . If stock is 55 PSI, would a deficiency in fuel pressure at boost (target is 100 PSI i assume) cause the ECU to compensate in some way? I wonder.

 

[STUGOTS]

I would SOOOOOOOOOO move

 

[TR930]

That's what my wife said, it might be cheaper than trying to dial this in!

 

[TR930]

Oh, and there is 15% less oxygen at altitude as well. Just another reason my car is running rich (at boost), no air. Can someone, anyone tell me how to fix this?? I cannot lean out the FMU disk to 4:1, what can I do with ignition timing? Spark duration, injector duration??

 

[Coloviper]

TR930;

I love Glenn as he is the only one who has worked on my Viper mods (I do trust him) and have no experience with the DC guys however I have tested 4 of my blown vehicles on that exact same dyno and none of them have those undulations in the boost profile graph. Not a single one so there is something else going on there.

I can only say talk to SCT so many times. They will be able to bring new elevation corrected O2 tables to the mix to burn in to the program, they will be able to address your concerns as that is what they do.

I know trying to consider everything can cause you to pull your hair out. There are too many variables and the solution seems like it gets lost at times. I have been there a done that on many vehciles before. I have a 1/2 dozen blown car projects up here over the years to just say, go back to the real source to fix and use KISS principle. Old world hot rod solutions can not be discredited. Upgrade fuel pumps, upgraded injectors, dump the FMU and those Paxton pumps and then a good tuning software like SCT (who supports the GEN III Viper) and then do the best you can fine tunign that program. The key to it all is SCT. Other than SCT, the other mods I mentioned are just hot rod mods for any car, that is not Viper or any motor specific. They just work!

 

[ViperGeorge]

Rick, Don't put a blower on your car! Sell it and buy my 06 First Edition. Mine already has forged internals, traction control, and other goodies. Heh, I'm just sayin.

TR930, DC flashed a new tune on my 06 based on a Dynojet run that I sent them. I simply sent them the printout and the PCM. After that the car was dyno'd again and the A/F looked fine. Now admittedly that was before I moved to Colorado and I haven't had it checked since. I'm running the stock Paxton pulley, FMU, and Paxton pumps.

I'm in Greenwood Village, not far from you guys. We should plan a BBQ or something. I'll host.

George

 

[ViperGeorge]

By the way, I've always been told that higher gear ratios would increase power and torque on a dyno. Someone up above posted it is the opposite. Anyone know which thought is correct and why?

There was also a thread on here somewhere where someone had a compelling argument that drive train loss was not proportional, i.e. not really based on a %. His basic argument went something like this. For a stock car the loss maybe measured as a % drop from the crank. However, this does not apply for modded cars it only sets the baseline in terms of how much HP it takes to turn the drive line. His point was if you lose say 65 HP from the crank to the wheels on a stock car you would always lose 65 HP regardless of the power adders you put on the engine. Essentially if you don't change the drive line components then it takes the same amount of HP to turn them. Seemed to make sense to me. If you change drive line components then it is possible that you will change the parasitic loss.

Hey are you guys going to be in Breckenridge this weekend? If you are we'll see you there.

George

 

[TR930]

George, I would advise you not to dyno your car here as you may discover that your perfect tune is quite imperfect up here! I need a data logging device to get someone out of state to tune this car. It is very frustrating.

CV, I called SCT and to get custom tune and they told me to go to local SCT tuner.

So, I don't know what I am going to do.

 

[ViperGeorge]

I know the tune would be different, my guess is the car would run richer. Although I'm not sure what impact the FMU would have. It is boost activated so that it adds fuel as boost increases. With lower boost levels I'm guessing that the FMU would add less fuel but not sure if that would offset the lack of air. I do have left/right wideband O2 sensors connected to a digital PLX multi gauge so if I were to get on it I could see what was happening. Haven't really driven the 06 much out here (or really not at all) since I've got it up for sale. We're probably taking the ACR to Breckenridge although my wife is trying to convince me to take the vert. We'll see.

 

[Coloviper]

When I was in Eddie's shop a few weeks ago, the local SCT tuner rep was in the shop so I know he has a relationship with him. Sorry, I wish I had a solid solution for you. But then I would have a solution for myself too.

Sorry but work is nuts and Heather has to work this weekend as well. No Breckenridge again this year. Damn!

 

[TR930]

I will receive the SCT tuner next week. I also ordered a data logging software and OBD2 scanner. I spoke with Sean Roe and he is putting me in the right direction. I will be back on the dyno next weekend with some results.

 

[Coloviper]

TR930;

That is good! Keep us posted on what you come up with. What is scary is that I thought you were a finance guy, not an electrical engineer (with all the data loggers and scanners) like me. Have a great 4th!

George, a BBQ sounds awesome. I haven't had a moment to spare since I started my new company in April. I was suppose the take the rest of the year off, but had to cave in. Just too much work out there right now. Hell I am up to 24 people in my group now. Crazy!

 

[TR930]

CV, I am in finance and asset management, I need the data logger to capture MAP sensor voltage across RPM range and corresponding A/F ratios.
I got a 2 BAR MAP sensor as well.