640 rwhp = 130 mph Trap Speed???

[Viperless]

My Viper specs:

'99 GTS
10 lb roe blower system
50/50 water/meth mix
VEC3
"Belanger like" headers, no pickle
3" exhaust, no cats
Harland Sharp rockers
Stock air box, k&n filters, smooth tubes
BFG drag radials
640 rwhp 698 rwtq on Dynojet tuned by PBJ

Went drag racing Saturday. Very good air. Temps in low 70's, low humidity, 980 ft elevation. Best run of the day was:

60' 1.80
330' 4.812
1/8 7.239
MPH 104.27
1000 9.306
1/4 11.043
MPH 130.69

MPH on the two other runs I made was 129.87 & 129.92.

My car dynoed 640 rwhp just three weeks ago and I've made no changes since then. Estimated vehicle weight of 3700 lbs with driver. I was expecting to see trap speeds around 134-135 with that kind of power. The 1/8th mph seems right. Am I off or is my car off? Or was the dyno lying???

Compare that to my old '97 GTS that dynoed 436 rwhp and went 11.77 @ 120 mph, 91 mph in the 1/8th with a vehicle weight of 3600 including driver. Different track but virtually identical atmospheric conditions.

I ran the numbers through some online horsepower calculators. Using 3700 lbs and 130 mph comes out to 634 hp. Some say at the rear wheels and some say at the crank.

Is a 200 gain in rwhp only worth 10 mph????

[Mccarlin]

You may be experiencing something that i have had concerns about when i first took my car to PBJ to get it tuned. After the Roe was installed with the 8lb pulley i had installed a boost gauge in the car to monitor it. To my surprise i was only seeing ~6lbs of boost on the street with the 8lb pulley. I explained this to Joe at PBJ and when we strapped the car to the dyno we were seeing 10-11lbs of boost on 2 different boost gauges (mine and joes hooked up to the VEC).
Since the Dyno doesnt have the same drag as the street we were able to get more boost out of the car and dyno good numbers. I'm guessing this is the same as in your case. You are probably more around 600-620rwhp on the street with normal drag.

[Nader]

Nice quater mile time nonetheless.

[ViperBing]

I have almost the same mods, and I run 133-134 on Kumhos.

[PAvenomRT/10]

The hp calculation based on ET and weight is by definition at the rear wheels since it is calculating the actual hp required to move the object (your Viper) to a given speed over a given distance. It's what the rear wheels are pulling that counts not what the fly wheel sees.
Pavenom RT/10

[Limit]

I don't want to be the ass to get this thread offtrack, but how much does a Roe S/C cost?

[99 R/T 10]

Depends, but about $7500. www.roeracing.com

[plumcrazy]

contact 1TONY1 on this site

tony sells and installs them

[mbccenter]

Keith

I was just thinking. Did you find the problem you were having on the dyno? Maybe that has something to do with it?

[Russ M]

It all depends on your traction and driving ability. On drag radials your 60foot time is ok, but the 1/8 mile time is a bit slow. In a perfect world your hp should be enough for 140mph, practice makes perfect.

[RobZ]

Our shop EVO with a built engine and GT37R turbo put down 625AWHP on our Mustang dyno and ran a 10.667 @ 132 down in 90* Tucson heat. I would expeect a higher trap speed with the torque of a boosted Viper.



Rob

[mnviper]

Just curious, are you running the same fuel as at Joe's or is our 10% ethanol Minnesota fuel now involved? I did a little research and found that the 10% mix has about 3% less BTUs than standard gasoline.

[Viperless]

Originally Posted by PAvenomRT/10

The hp calculation based on ET and weight is by definition at the rear wheels since it is calculating the actual hp required to move the object (your Viper) to a given speed over a given distance. It's what the rear wheels are pulling that counts not what the fly wheel sees.
Pavenom RT/10

Well then, it looks like 130mph is right on given the weight. Calculator says 634 rwhp for 3700 lbs and 130 mph trap speed.

[Viperless]

Originally Posted by mbccenter

Keith

I was just thinking. Did you find the problem you were having on the dyno? Maybe that has something to do with it?

No. Replaced the fuel filter though. I kept an eye on the AFR's and everything seemed fine. A tad on the rich side if anything.

Originally Posted by Russ M

In a perfect world your hp should be enough for 140mph, practice makes perfect.

At a race weight of 3700 lbs???

Originally Posted by RobZ

Our shop EVO with a built engine and GT37R turbo put down 625AWHP on our Mustang dyno and ran a 10.667 @ 132 down in 90* Tucson heat. I would expeect a higher trap speed with the torque of a boosted Viper.
Rob

Again, what about the weight. 100 lbs = ~1 mph.

Originally Posted by mnviper

Just curious, are you running the same fuel as at Joe's or is our 10% ethanol Minnesota fuel now involved? I did a little research and found that the 10% mix has about 3% less BTUs than standard gasoline.

Same fuel as when it was on the dyno which was/is our local 92 octane pump gas.

[V10TT]

Could be heat soak. What I find interesting is that it looks like the car is laying down in the top end. It only picks up 26 mph between the 1/8 and 1/4 mile marks.
I bet that if it was an all motor viper making that kind of power, it would trap over 135.

[Russ M]

Viperless,

Yes even at that weight, it should not be much of a stretch.

One of my old cars which made an honest 600rwhp at the time with a race weight of 3400lb's ran 139mph. But it was far from a v10's power band and torque curve, so your car should be capable of doing it.

[RX VIPER]

I've got a mild tune on my Roe s/c (568 rwhp currently) and ran mid to high 120's (126-128.5) last month in 95+ degree heat. I also had the bfg's on.

[kwkshift]

Originally Posted by V10TT

Could be heat soak. What I find interesting is that it looks like the car is laying down in the top end. It only picks up 26 mph between the 1/8 and 1/4 mile marks.
I bet that if it was an all motor viper making that kind of power, it would trap over 135.

My car is N/A and it makes 600 rwhp and 615 rwtq. With about 1300' DA it trapped 135. Heat soak does sound like a possiblilty with his car. It should pick up a good 30+ mph on the big-end with that kind of power.

[JUCD VPR]

That sounds right. I have 600/820 and I run 1.5 60' 6.8 1/8th mile, and 10.666@131 in the 1/4 mile.

[Viperless]

I don't know how the hell you guys pull those 1.5x short times on anything but a slick. I've been drag racing stick shift cars for 20 years so it's not like I'm a novice at it. Best 60' I ever managed in a Viper was a 1.75 on Hoosier road racing tires. I hear guys claim 1.7x's on Pilots which I find very hard to believe unless they're soaking them in VHT or something. Who knows.

[RTED]

Those quarter mile times are impressive! I was at Milan Dragway (Michigan) yesterday to observe the time trials. Cars hitting similar times and speeds were HEAVILY modified and were definitely not streetable! Your car is turning some impressive times in comparison and you can drive it home from the strip!

[TOOOFST]

Mccarlin's right on!
You've got more like 600 rw.

[Viperless]

Starting to look a little better.

http://videos.streetfire.net/video/5...c8008b3c35.htm

Next two passes were 10.85 & 10.87 so it wasn't a fluke.

[BlueGTS]

134 is very health. Did you change anything on your setup?

[Viperless]

Originally Posted by BlueGTS

134 is very health. Did you change anything on your setup?

Tried different spark plugs and richened up the fuel curve. The mph on all three runs was within .1 mph of each other so I was going to bump up the fuel again to see if I could get more mph out of it. But the damn laptop battery died on me so I called it a day. I'm happy for now. I'll fool with it more next year.

[Disturbed]

You are making closer to 600rwhp. I make 565rwhp N/A... running 127's in the 85+ heat. 600rwhp should hit right at 130's.

Also, shifting plays a big roll in the mph.


You've got to be one big boy to make a viper come in at 3700lbs.

[dun4791]

Heat soak....... A non-intercooled/heat exchanger Autorotor twin screw has to be holding a lot of heat. Couple that with only 1 IAT. Probably the least efficient forced induction for our cars.

[Viperless]

Originally Posted by Disturbed

You've got to be one big boy to make a viper come in at 3700lbs.

Not really. 3375 curb weight + 125 (blower and other odd & ends) + 200 (driver) = 3700. I plan on getting the car four corner weighted next spring. Then we'll know the actual weight. It has to be pretty close to 3700 with me in it and a full load of fuel.

[TrainerDave]

With that kind of power you will see mid 10's at over 130 when you get used to the car. Most of the C6 Z06's are getting high 11's in the mid 120's granted the car is only 3100lbs, but has much less HP, than you do. I have seen a video of a "claimed" 100% stock Z06 running 10.80's and 130 traps on drag radials. I have also personally seen runs of stock Viper gts's going high 11's as well.

[kwkshift]

Another important factor that no one on any car forum seems to address is DA. I remember that one guy about a year ago claiming that his C6Z06 ran 10's and it was stock with tires. Yeah, it did, but it was at -800 feet DA. Those racing conditions are so rare, that they are next to impossible to duplicate.

Someone may live where their DA on that certain day, at that track, at that time of the day may only be 3500+' above sea level and they may not get very good times.

Here is a little converter: http://wahiduddin.net/calc/calc_hp_dp.htm

So for example, right now it's 61 degrees, Baro. is only 29.69, dew point is 34* and we are at 1,200' above sea level. So, the density altitude is 1963'. Not horrible, but the best we may get out here in the winter is in the 1200' range. If it gets too much cooler out, say in the low 50's or so, the track starts going away and that new-found power is wasted.