SCT versus Roe - Drag Strip Results

[Jack B]

The following is a comparison of two years using the SCT package versus the use of the Roe from it's beginning. I finally made the drag strip where there were some decent temperatures.

Car:
97 GTS: head work, T&D's, 50 lb injectors and headers/exhaust.

Quarter Mile Speed:
Roe: 122-124
SCT: 126-128

Quarter Mile ET:
Vec: 11.5-11.6
SCT: 11.2 11.3

Let me preface the above by saying my 60's are terrible. I have not been at a strip where it has been prepped properly for quite a while. They are a range of 1.62 to 1.75. That is for the last 10 or 15 times down the strip.

The last four passes in August at National Trails were in 95-100 degree temps, the times were in a range of 11.32 to 11.42. I had to pull a huge amount of fuel out of the car in the 4500-6000 rpm range. Keep in mind the viper PCM does the opposite of what is logical - it adds fuel in high temps.

I had three passes this weekend and the temps were 70-75 degrees. I estimated that I should add 10% fuel between 3900 and 6000 to be safe due to the cooler temps - wrong, my first run was an 11.0 a/f.

Run 1 -this run was as follows:
Et: 11.32
126.9
Reaction Time +.06
60: 1.66
A/F: 11.0


Run 2 - I went back to original tune, in affect , pulled the 10% I had added over the 95 degree tune. This is what is interesting, this tune was a 12.5 a/f in 95 degree temps, however, it was a 11.5 a/f in 75 deg temps. This shows how counter-intuitive the viper PCM is.

ET 11.35
Reaction time: -.002
126.8
60': 1.72
A/F: 11.5

Run 3 - I pulled another 10% fuel, however, forgot to log on that run. It did not matter, the cars was absolutely putting out more hp, especially at higher rpms. The a/f has to be getting close to the sweet spot.

ET: 11.20
Reaction time: +.08
60': 1.75
127.8
A/F: ?

I had dialed in a 11.3 and the car I was racing had a dial of 12.9. I caught him and passed him about 100 yds before the lights, but, broke out. He had a .06 reaction, but, a poor 60', I should of backed off, but, got caught up in the car's performance.

There was a minor hesitation in all three runs at 5500 in first gear. That is the next issue to figure out. I will have to look closer at the logs and see what is causing it. SCT makes it all so easy.

 

[Twister]

trying to understand...So you didnt actually run them both on the same day..Just your results going from one to the other on differant days.

 

[Jack B]

trying to understand...So you didnt actually run them both on the same day..Just your results going from one to the other on differant days.

Sorry about the confusion, I ran the VEC several years. I changed to the the SCT tune two years ago. The mods have remained the same, the improved times/speeds came with the SCT. This is the first year that the SCT controls everything, there is no VEC intervention.

 

[BOTTLEFED]

I didn't think you were s/c??
So you are now running your Roe on the SCT and your previous results were with the VEC??
What pulley are you running and are you still on cast pistons? I thought you ran a big shot on N2O?
I think there is some missing info. Was there another older thread on this??

 

[moparracing]

nice runs.

excuse my ignorance, but what are T&D's?

 

[nutkees]

nice runs.

excuse my ignorance, but what are T&D's?

Roller Rockers

 

[Simms]

I didn't think you were s/c??
So you are now running your Roe on the SCT and your previous results were with the VEC??
What pulley are you running and are you still on cast pistons? I thought you ran a big shot on N2O?
I think there is some missing info. Was there another older thread on this??

Jack is NA, no SC.

 

[plumcrazy]

Jack is NA plus nitrous.

 

[1TONY1]

I didn't think you were s/c??
So you are now running your Roe on the SCT and your previous results were with the VEC??
What pulley are you running and are you still on cast pistons? I thought you ran a big shot on N2O?
I think there is some missing info. Was there another older thread on this??

I think he should have said "VEC" instead of Roe. Everyone thinks of the"Roe" as the supercharger which in this case it is not. If it were a "Roe" he would have been in the 140mph range

 

[BOTTLEFED]

ok, I think its making more sense.
So where did the VEC come in??
It says Roe vs SCT, but I'm not seeing where you ran a VEC??

 

[cyaford]

ok, I think its making more sense.
So where did the VEC come in??
It says Roe vs SCT, but I'm not seeing where you ran a VEC??

See Tony's post above yours. VEC = ROE

 

[CWhiteRun]

Do you have a separate nitrous fuel enrichment setup? If so, then I'd lean that bad boy out some more. Mine N/A pulled like a MF'er around 12.3-12.5 under way with no knock.

 

[Jack B]

I didn't think you were s/c??
So you are now running your Roe on the SCT and your previous results were with the VEC??
What pulley are you running and are you still on cast pistons? I thought you ran a big shot on N2O?
I think there is some missing info. Was there another older thread on this??

All this data is NA. The only points I was trying to make is that the ET's dropped and the MPH's increased after the transition from the VEC tuned PCM to the SCT controlled PCM. I tried using the VEC for over five years and could never get rid of a very annoying hesitation. With the SCT package it fixed the hesitation issue that had been there since the VEC was installed. I was totally surprised the way the ET's came down and the MPH went up.

I do not think the VEC issues would have been as bad if the car had the stock injectors. I installed the larger injectors because the stock injectors go static at about 475-500 rwhp. That is not a guess, my logs showed them going static at about 480 rwhp. At that point I could not change the a/f, the injectors just would not respond.

 

[Jack B]

I think he should have said "VEC" instead of Roe. Everyone thinks of the"Roe" as the supercharger which in this case it is not. If it were a "Roe" he would have been in the 140mph range

Best speed on the bottle has been 144.6. All the data above is strictly NA.

 

[Jack B]

Do you have a separate nitrous fuel enrichment setup? If so, then I'd lean that bad boy out some more. Mine N/A pulled like a MF'er around 12.3-12.5 under way with no knock.

The nitrous enrichment is done strictly through the jetting on the tube sprayers. 12.5 a/f is the goal NA and 11.5 a/f on the bottle. I wish I had logged on my last run. It had to be close to 12.5 a/f. It was only about .15 sec (11.2) better than the previous runs, but, the last run had the worst 60 ft time. My guess is with the same 60 it would have a 11.05 - 11.1. That is still with a so-so 60. I think they have outlawed VHT in the State of Ohio. We have not seen a well prepped track in a long time.

Sort of a sidebar, but, the logs showed that the car never sees an rpm below 4200-4300 during the 1/4 mile except where the rpm's dip after launch. The shift light was set at 5800, the shift takes place at 6000 and the rpms drop to a low of 4200 as you go thru the gears. Tom Welsh used to shift at 5600 so the rpms dropped to the peak torque, that might be something to play with. What is everyone else (NA) shifting at?

 

[Daddy Long Stroke]

You have cleared the Roe/Vec confusion....But what is a SCT tune? lol it sounds great, but goddamn if I aint confused!

-But If someone can pick up 4 MPH and 3 tenths with one of these, it sure does sound worth while

 

[FastMatt]

The nitrous enrichment is done strictly through the jetting on the tube sprayers. 12.5 a/f is the goal NA and 11.5 a/f on the bottle. I wish I had logged on my last run. It had to be close to 12.5 a/f. It was only about .15 sec (11.2) better than the previous runs, but, the last run had the worst 60 ft time. My guess is with the same 60 it would have a 11.05 - 11.1. That is still with a so-so 60. I think they have outlawed VHT in the State of Ohio. We have not seen a well prepped track in a long time.

Sort of a sidebar, but, the logs showed that the car never sees an rpm below 4200-4300 during the 1/4 mile except where the rpm's dip after launch. The shift light was set at 5800, the shift takes place at 6000 and the rpms drop to a low of 4200 as you go thru the gears. Tom Welsh used to shift at 5600 so the rpms dropped to the peak torque, that might be something to play with. What is everyone else (NA) shifting at?

I shift my car at 6000rpm, it runs 10.7@130mph @3600ft N/A with 612 RWHP. I realy need to take it to sea level some time and run it. Should run a realy lo 10 all motor.