Annual Christmas Day 150MPH run yields suprise?
12-25-2004, 02:29 PM
#1
Annual Christmas Day 150MPH run yields suprise? Once again, I’ve done my annual Christmas Morning high speed run. I was expecting to break 160 mph this year after the installation of the SuperMaxx headers.
I didn’t.
At 155+, the engine cut out like I hit the rev limiter or the speed governor.
This year, I ran an AutoTap log. The log shows on data point #65 that the car was at 158 MPH and the engine was at 5412 rpm. The log claims that the vehicle speed held steady at 158 MPH for the next several data points, even though the engine rpm climbed an additional 344 to 5756 rpm.
At which time I remember the engine cutting out, and my log shows I started coasting down.
WTF?
I thought that GM set the LS1 cars with Z rated tires at at a 162 mph speed governor?
And the stock fuel cut off is at 6250 RPM, right?
So since The AutoTap COMPUTER LOG sez I never hit either stock limit, why did the engine cut out?
Does the PCM have some kind of data sending limit or what happened here?
2002 Collector Edition Coupe, M6
Direct-Flo Airlid
Holly Powershot Air Filter
Brian Green Ram Air System
NGK TR55-IX {Iridium} Plugs
Dynatech SuperMAXX Header System
I didn’t.
At 155+, the engine cut out like I hit the rev limiter or the speed governor.
This year, I ran an AutoTap log. The log shows on data point #65 that the car was at 158 MPH and the engine was at 5412 rpm. The log claims that the vehicle speed held steady at 158 MPH for the next several data points, even though the engine rpm climbed an additional 344 to 5756 rpm.
At which time I remember the engine cutting out, and my log shows I started coasting down.
WTF?
I thought that GM set the LS1 cars with Z rated tires at at a 162 mph speed governor?
And the stock fuel cut off is at 6250 RPM, right?
So since The AutoTap COMPUTER LOG sez I never hit either stock limit, why did the engine cut out?
Does the PCM have some kind of data sending limit or what happened here?
2002 Collector Edition Coupe, M6
Direct-Flo Airlid
Holly Powershot Air Filter
Brian Green Ram Air System
NGK TR55-IX {Iridium} Plugs
Dynatech SuperMAXX Header System
12-25-2004, 02:56 PM
#3
Originally Posted by JNorris
The stock speed limiter is set at 160mph.
John
John
But the car cut out at 158 mph. It went no faster then 158 in the AutoTap log, though the rpm's increased by 344 rpm.
I have no slushbox torque converter so those 344 rpm's went somewhere!
Where?
12-25-2004, 03:41 PM
#5
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Well I believe it's a drag limited speed rating. To my understanding an LS1 equipped F-body can't push itself in stock form much beyond a certian speed due to air drag created by the body. I see that you are not stock so maybe with stock HP levels you may have only gone say 155mph. 158mph is plenty fast.....call it good!!
12-25-2004, 05:09 PM
#6
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Originally Posted by fnbrowning
Okay, Let's say you are correct at 160mph.
But the car cut out at 158 mph. It went no faster then 158 in the AutoTap log, though the rpm's increased by 344 rpm.
I have no slushbox torque converter so those 344 rpm's went somewhere!
Where?
But the car cut out at 158 mph. It went no faster then 158 in the AutoTap log, though the rpm's increased by 344 rpm.
I have no slushbox torque converter so those 344 rpm's went somewhere!
Where?
There is no question that the file I just looked at from a stock 2002 SS had the speed limiter set at 160mph. If your PCM has not been reprogrammed then it is set at 160 as well.
I can not tell you why AutoTap only showed 158mph.
John
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12-26-2004, 10:30 AM
#9
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Originally Posted by SmokingWS6
A tap does not always update that fast. I'm sure you topped out at the speed limiter. They are definately not drag limited at 150 
He's right, autotap reads too slow to probably show 160. Try a tech 2 and i'm sure it will show 160.
12-26-2004, 01:48 PM
#10
I want to thank everyone in this thread that replied so quick to answer my question.
I did not have this "problem" last year, before the SuperMaxx header install.
I blame the headers as the cause of the car hitting the speed limiter.
I will have the PCM reprogrammed this spring.
Not an easy task in St. Louis!
I did not have this "problem" last year, before the SuperMaxx header install.
I blame the headers as the cause of the car hitting the speed limiter.
I will have the PCM reprogrammed this spring.
Not an easy task in St. Louis!