Track temps HP timing etc

[lmcgrew79]

So after running at road atlanta last week after installing headers, my top speeds at the end of the straights are down about 3 mph vs being there last fall, I've got a lot of data comparing getting out of turn 7 at different speeds getting on throttle etc, and the car is just slower. The IATs was around 93-94 on track vs 74 back in the fall, coolant temps about the same at 217 at this tt event as I was shooting for 2nd and 3rd laps times. Another friends stock car in the fall was only running 208 temps and was going a few mph faster as well. In watching some other viper videos they are getting to around 157 leaving the corner at around the same speed and i was hitting about 153, and my 153 was a bit deeper than the 157s. One thing im actually good at is getting of corners, that is generally how i set up the entry. I could go deeper basically because the lack of speed.

On a dyno the headers did pick up good mid range power about 45-50hp and some top end power 25-30 hp, but those are controlled runs. On track I feel i basically got nothing but better sound and maybe less power because of the heat? The car has an arrow pcm as it did last fall as well. This is pretty aggravating and I'm not sure what is the cause. According to the timing tables and iat/ect i may have been pulling around 6-8 degrees of timing. Just looking for some input, car has arrow/comp coupe pulley, arrow pcm, arh headers with cats, and a dei heat shield. I just purchases a ron davis radiator to see if it does anything or not, no one really seems to know for sure on track, maybe its something different i dont know, car seems to run just fine, but not really making anymore power. Thanks

[ViperGeorge]

Suggestions: Insulate the airbox and make sure to wrap the IAT sensors in the tubes. PCM pulls timing at ridiculously low IATs. In fact I believe it would pull timing even if the sensors were reading an ambient of 93-94. But the sensors can get hot even though cool air is entering the airbox. I have wondered if the DEI airbox blocks air flow from the vicinity of the radiator (at speed the fans really don't do anything). Does air coming through the radiator help cool or heat the sensors? Does this cause more heat to accumulate around the IAT sensors? It does sit kind of low behind the radiator. Wrap oil cooler lines, coolant tank, Fuse box, main wire harness, O2 wires, ABS lines, and EVAP line. Talk to Andy at Viper Exchange about getting your water pump blue printed. He claims this solves any heat issues. Someone else (BlueTA #1, maybe) did try a different radiator with little effect from what I remember.

[lmcgrew79]

I wrapped everything, except for the very end of the rear 02's figured out the hard way that they needed it as well. The DEI box did seem to reduce the iat a some as they seem to be a bit closer to ambient, not sure if they block flow from radiator or not though. Someone said something about using a spring in the upper radiator hose as well, will try that when i do the radiator. Andy message me a price on the waterpump.

[FLATOUT]

Luke,

Your coolant temps although a touch higher (I read 217) certainly aren't in anyway out of line or "high" so I wouldn't worry about those numbers. If they are getting above 240 and climbing I would look into the water pump issue discussed above. It's rare but it does happen and is an easy fix.

As for your speeds at the end of the straight, do you have anything to compare against in those same conditions? Comparing what you did in the fall and what you did in the summer temps makes it very tough to compare. Obviously the car picked up power as seen on the dyno but on a 95 degree day both a stock car, and a car with headers are both going to be down on power due to the DA. We saw it at the Ring, you'll see it at your local drag strip, and if you're a good enough driver you'll notice it on the road course as well.

I'll be interested to see how much it picks up in the fall

In a 1/4 mile I will see a 6mph swing in trap speeds from cooler days to the hot summer days.

Just throwing out some words for discussion.

Andy

[mjorgensen]

So after running at road atlanta last week after installing headers, my top speeds at the end of the straights are down about 3 mph vs being there last fall, I've got a lot of data comparing getting out of turn 7 at different speeds getting on throttle etc, and the car is just slower. The IATs was around 93-94 on track vs 74 back in the fall, coolant temps about the same at 217 at this tt event as I was shooting for 2nd and 3rd laps times. Another friends stock car in the fall was only running 208 temps and was going a few mph faster as well. In watching some other viper videos they are getting to around 157 leaving the corner at around the same speed and i was hitting about 153, and my 153 was a bit deeper than the 157s. One thing im actually good at is getting of corners, that is generally how i set up the entry. I could go deeper basically because the lack of speed.

On a dyno the headers did pick up good mid range power about 45-50hp and some top end power 25-30 hp, but those are controlled runs. On track I feel i basically got nothing but better sound and maybe less power because of the heat? The car has an arrow pcm as it did last fall as well. This is pretty aggravating and I'm not sure what is the cause. According to the timing tables and iat/ect i may have been pulling around 6-8 degrees of timing. Just looking for some input, car has arrow/comp coupe pulley, arrow pcm, arh headers with cats, and a dei heat shield. I just purchases a ron davis radiator to see if it does anything or not, no one really seems to know for sure on track, maybe its something different i dont know, car seems to run just fine, but not really making anymore power. Thanks

The other cars you talk of ACR's? If so are they using the same wing settings as you are because that could be the difference of a few MPH. Also the ARH tubes are very close to the block compared to Belangers, that is a long run at full power so even a small change in coolant temp can put the timing off a bit more. You did wrap the coolant and oil lines on the passenger side of the engine correct?

[Dan Cragin]

You might consider running 94 octane or better fuel. If the car is going into knock control, it can cause the loss of power you describe.

[cashcorn]

Also, maybe an HPtune..

[ViperGeorge]

You might consider running 94 octane or better fuel. If the car is going into knock control, it can cause the loss of power you describe.

I was under the impression that you will lose power if you run higher octane than the engine requires. Something to do with higher octane fuel burning slower. The engine is rated for 91 I believe.

[Steve M]

I was under the impression that you will lose power if you run higher octane than the engine requires. Something to do with higher octane fuel burning slower. The engine is rated for 91 I believe.

With a stock PCM yes, but the Arrow PCM requires 93 octane minimum.

[lmcgrew79]

Luke,

Your coolant temps although a touch higher (I read 217) certainly aren't in anyway out of line or "high" so I wouldn't worry about those numbers. If they are getting above 240 and climbing I would look into the water pump issue discussed above. It's rare but it does happen and is an easy fix.

As for your speeds at the end of the straight, do you have anything to compare against in those same conditions? Comparing what you did in the fall and what you did in the summer temps makes it very tough to compare. Obviously the car picked up power as seen on the dyno but on a 95 degree day both a stock car, and a car with headers are both going to be down on power due to the DA. We saw it at the Ring, you'll see it at your local drag strip, and if you're a good enough driver you'll notice it on the road course as well.

I'll be interested to see how much it picks up in the fall

In a 1/4 mile I will see a 6mph swing in trap speeds from cooler days to the hot summer days.

Just throwing out some words for discussion.

Andy

217 was on the second lap, 230 by the 3rd, was a tt event so didnt ever go anymore than 5 and that was using 4 as a cool down.

The other cars you talk of ACR's? If so are they using the same wing settings as you are because that could be the difference of a few MPH. Also the ARH tubes are very close to the block compared to Belangers, that is a long run at full power so even a small change in coolant temp can put the timing off a bit more. You did wrap the coolant and oil lines on the passenger side of the engine correct?

Im running the least amount of wing as possible, and yes wrapped all the lines with dei velco wrap.


I revisited the data of some other tracks i've ran in different conditions, this seems to happen across the board, looking at earlier laps with lower coolant temps vs higher coolant temps the car don't seem to pull as much power as higher iat temps, I do have the dei shield but after I took it off this evening noticed the plug is not on the bottom of the airbox, I remember reading somewhere that plugging that helps, so I will try that as well. Even with headers it seems like an equal net loss of power vs stock when the car starts pulling timing.

[Arizona Vipers]

Dude there are so many variables in play here. You cant compare other Viper's trap speeds on the track. As Wheeler said above, wing settings alone you can see a 15mph difference on long straights. Wheels/tires are another huge factor. My Forgeline/Pirelli's setup weighs 90lbs less than a stock ACR setup. That would be 5mph+ on a long straight. You could weigh 250 and have full tank of fuel, the other guy could weigh 150 and have 1/4 tank fuel, that's 200 lbs. LOL. Despite some theories here, I ALWAYS run 100 octane, even in my stock ACR, in my opinion it WILL prevent detonation and decrease/delay the timing being pulled and result in a lot more power on hot days. This is my conclusion after tracking here in Arizona for three years. Every hardcore track guy I know runs 100 octane if they can afford it. These cars pull HUGE HUGE HUGE power on hot days, my 1st session of the day on small tracks will be TWO SECONDS faster than my 2nd session, then it gets worse from there. And it was much worse than this when I was running 91 octane.

[lmcgrew79]

Dude there are so many variables in play here. You cant compare other Viper's trap speeds on the track. As Wheeler said above, wing settings alone you can see a 15mph difference on long straights. Wheels/tires are another huge factor. My Forgeline/Pirelli's setup weighs 90lbs less than a stock ACR setup. That would be 5mph+ on a long straight. You could weigh 250 and have full tank of fuel, the other guy could weigh 150 and have 1/4 tank fuel, that's 200 lbs. LOL. Despite some theories here, I ALWAYS run 100 octane, even in my stock ACR, in my opinion it WILL prevent detonation and decrease/delay the timing being pulled and result in a lot more power on hot days. This is my conclusion after tracking here in Arizona for three years. Every hardcore track guy I know runs 100 octane if they can afford it. These cars pull HUGE HUGE HUGE power on hot days, my 1st session of the day on small tracks will be TWO SECONDS faster than my 2nd session, then it gets worse from there. And it was much worse than this when I was running 91 octane.

I know that, but what i can compare is my own car on different days, which is what I was mainly doing. Then I just compared a few stock acr speeds there to see what they was hitting, my entire point is with headers the loss on a hot day must be massive, being it made alot more with them on a dyno but was slower when it was 20 degrees hotter than without headers.

[ViperGeorge]

With a stock PCM yes, but the Arrow PCM requires 93 octane minimum.

I ran an Arrow controller on my 15 TA here in Colorado. We only have 91 here and the car ran fine. It might have run better on 93 but 91 didn't hurt it. Andy says that Dick tuned the 9 liter to run on 91 so I would assume the Arrow controller is fine with 91. I assume this because why would he tune the 9 liter to run on 91 but not the controller for the 8.4?

[Steve M]

I ran an Arrow controller on my 15 TA here in Colorado. We only have 91 here and the car ran fine. It might have run better on 93 but 91 didn't hurt it. Andy says that Dick tuned the 9 liter to run on 91 so I would assume the Arrow controller is fine with 91. I assume this because why would he tune the 9 liter to run on 91 but not the controller for the 8.4?

The car would run fine if you aren't beating on it...how much WOT time are we talking about though?

I can only go on what they say, which is straight from their website: https://store.prefix.com/products/20...rol-module-kit

- Revised fuel, spark and cam position tables that maximize power increases associated with engine modifications and/or exhaust systems
- Aggressive off-throttle exhaust note
- Requires min 93 octane fuel.
- Rev limit increased to 6600 rpm with decreased hysteresis.
- Allows racing approved final drive ratios from 3.07:1 to 4.10:1.
- First to fourth gear skip shift eliminated for racing use.
- Catalyst monitor disabled to allow the use of high flow / or no catalyst and headers
- Air flow rationality diagnostic disabled which permits greater range of flow modifications
- Misfire detection disabled to permit reduce mass rotating assemblies and further modifications
- Includes all 2014 production updates.
- Not intended to work with superchargers, turbochargers, nitrous or power levels above 675 BHP

I figure when they bold things, it's important to note.

That said, this issue seems to come up every year around this time. This is a known issue with these cars, and is mostly IAT driven. About the only thing you can do outside of a custom tune is wait for cooler weather.

[ViperGeorge]

The car would run fine if you aren't beating on it...how much WOT time are we talking about though?

I can only go on what they say, which is straight from their website: https://store.prefix.com/products/20...rol-module-kit

- Revised fuel, spark and cam position tables that maximize power increases associated with engine modifications and/or exhaust systems
- Aggressive off-throttle exhaust note
- Requires min 93 octane fuel.
- Rev limit increased to 6600 rpm with decreased hysteresis.
- Allows racing approved final drive ratios from 3.07:1 to 4.10:1.
- First to fourth gear skip shift eliminated for racing use.
- Catalyst monitor disabled to allow the use of high flow / or no catalyst and headers
- Air flow rationality diagnostic disabled which permits greater range of flow modifications
- Misfire detection disabled to permit reduce mass rotating assemblies and further modifications
- Includes all 2014 production updates.
- Not intended to work with superchargers, turbochargers, nitrous or power levels above 675 BHP

I figure when they bold things, it's important to note.

That said, this issue seems to come up every year around this time. This is a known issue with these cars, and is mostly IAT driven. About the only thing you can do outside of a custom tune is wait for cooler weather.

I may remember this incorrectly but I had thought that Mark Jorgenson had told me the car would run fine on 91 with the Arrow controller but you would gain power with 93. I tracked the car so it was WOT a lot.

[Arizona Vipers]

I know that, but what i can compare is my own car on different days, which is what I was mainly doing. Then I just compared a few stock acr speeds there to see what they was hitting, my entire point is with headers the loss on a hot day must be massive, being it made alot more with them on a dyno but was slower when it was 20 degrees hotter than without headers.

Wrap the headers and get Doug Shelby's heat shield and insulate it

[ViperGeorge]

Wrap the headers and get Doug Shelby's heat shield and insulate it

I know Lou Bellanger says not to wrap the headers. Don't know what ARH says.

[lmcgrew79]

Ive got the heat shield im putting more heat shielding on the bottom of it as we speak, Ron Davis radiator came in today and im about done putting it in , will be at track in 2 weeks with some other vipers that will be a better comparison same track same day, dont think the headers are the problem as far as heat.

[Jack B]

I know Lou Bellanger says not to wrap the headers. Don't know what ARH says.

Wrapping will not hurt the ARH headers. I had mine ceramic coated in/out. I do not know why, however, the engine bay and sills seem to run cooler with ARH, versus, Belanger. However, the Belange factory ceramic coating looked suspect.

[Bruce H.]

I ran an Arrow controller on my 15 TA here in Colorado. We only have 91 here and the car ran fine. It might have run better on 93 but 91 didn't hurt it. Andy says that Dick tuned the 9 liter to run on 91 so I would assume the Arrow controller is fine with 91. I assume this because why would he tune the 9 liter to run on 91 but not the controller for the 8.4?

The regular Arrow PCM was tuned for 93, not 91. What that means is it is not safe on 91 "under all conditions", and will run like a champ right up until the time that the knock response system can no longer retard timing far enough or quickly enough to avoid damaging detonation. I had a lengthy conversation with Dick about the safety of running it on my car on track at an advanced level with 91. I don't have easy local access to 93 and for that reason he was not able to recommend it. I questioned him about the knock sensor monitoring the amount of detonation and providing that as an input to the PCM and it in-turn retarding timing slightly to avoid severe detonation. He agreed that is how it works but that some combination of conditions can exceed the ability of this knock response system to protect the engine and that 93 must be used to be safe under all conditions, especially when planning to track the car.

I'd suggest that only those who know more than Dick about the engine and PCM should disregard his advice

[1of1TA1.0]

I'd like to see a comparison of a track car with and without the DSE shield. I removed mine but haven't been back to the track yet. It has to cut down on some of the airflow. I still run one on my street car though. I love the product so don't anyone think I am saying anything bad.

[SSGNRDZ_28]

Data is king and I don’t have any comparing coolant or oil temps but if I wanted to block radiator air flow, placing an object spaced off the low pressure side is about the least effective way I can think of. The air is already through the radiator by the time it encounters the heat shield. At that stage you’re just diverting lower speed air in other directions but the air flow through the radiator will not have been affected.

[lmcgrew79]

This could have been the issue, if the car was thinking it was running lean.
C98BEC49-36BA-40A6-815B-F1A94948FEED.jpg

[Steve M]

Heh...nice. There are way too many issues with headers on Vipers considering the price - the juice just isn't worth the squeeze IMO.

[Jack B]

This could have been the issue, if the car was thinking it was running lean.
C98BEC49-36BA-40A6-815B-F1A94948FEED.jpg

Refer to my ARH install thread, the difficulty with installation of the header merge joint can lead to damaging the gasket. The answer is to put a light tack coat of high temp red on one side and attach the gasket to the joint. The problem is, that adds a day (curing time) to the job and a lot of shops will not take the extra step. Time is money, I would probably to the same on a fixed price install.