LS1TECH - Camaro and Firebird Forum Discussion

PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

PCM limited to 8k how?

Thread Tools
 
Search this Thread
 
Old Dec 11, 2011 | 11:56 AM
Share
  #1  
LSwonderfull's Avatar
LSwonderfull
Thread Starter
On The Tree
 
Joined: Nov 2005
Posts: 184
Likes: 0
Question PCM limited to 8k how?
Im using a 98 fbod pcm in my carbed LS2 and im wondering what method GM uses to limit rpm to 8000 rpm? The lower rev limits are fuel cut, but what about 8k limit? Ignition kill?
Reply
0
Old Dec 11, 2011 | 12:18 PM
Share
  #2  
2TR's Avatar
2TR
On The Tree
 
Joined: Apr 2011
Posts: 181
Likes: 1
Default
The PCM doesn't have calibration options BEYOND this RPM. Its the limit of the stock PCM according to the stock tune calibration. There are no more fields beyond this rpm...no data to reference...no worky!
Reply
0
Old Dec 11, 2011 | 12:26 PM
Share
  #3  
LSwonderfull's Avatar
LSwonderfull
Thread Starter
On The Tree
 
Joined: Nov 2005
Posts: 184
Likes: 0
Default
Originally Posted by 2TR
The PCM doesn't have calibration options BEYOND this RPM. Its the limit of the stock PCM according to the stock tune calibration. There are no more fields beyond this rpm...no data to reference...no worky!
Im not trying to turn past 8k, im asking how pcm disables 8k and up rpm?
Reply
0
Old Dec 11, 2011 | 01:51 PM
Share
  #4  
2TR's Avatar
2TR
On The Tree
 
Joined: Apr 2011
Posts: 181
Likes: 1
Default
Rev limiter cuts fuel. Fuel is then turned back on at an rpm you choose which is typically -100rpm below the cut limit. i.e. cut @ 6,500rpm, back on @ 6,400rpm.

Hp Tuners Example:

VCM Editor> Engine > Fuel > Cutoff, DFCO > Fuel Cutoff > RPM Limit. (Max available in stock tunes is usually 12,800rpm) BUT again there are no other supporting tuning tables past 8,000rpm.
Reply
0
Old Dec 12, 2011 | 11:05 AM
Share
  #5  
gectek's Avatar
gectek
TECH Enthusiast
iTrader: (2)
 
Joined: Jun 2008
Posts: 702
Likes: 0
Default
In the crazy high RPMs the crank sensor "pulse" becomes static. Maybe that will shed some light.....
Reply
0
Old Dec 12, 2011 | 01:33 PM
Share
  #6  
Wnts2Go10O's Avatar
Wnts2Go10O
TECH Veteran
iTrader: (12)
 
Joined: Dec 2004
Posts: 4,354
Likes: 0
From: Rockville, MD
Default
Originally Posted by 2TR
Rev limiter cuts fuel. Fuel is then turned back on at an rpm you choose which is typically -100rpm below the cut limit. i.e. cut @ 6,500rpm, back on @ 6,400rpm.

Hp Tuners Example:

VCM Editor> Engine > Fuel > Cutoff, DFCO > Fuel Cutoff > RPM Limit. (Max available in stock tunes is usually 12,800rpm) BUT again there are no other supporting tuning tables past 8,000rpm.
i think it just uses the table values at 8k for anything past that.
Reply
0
Old Dec 15, 2011 | 11:55 PM
Share
  #7  
soundengineer's Avatar
soundengineer
8 Second Club
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (16)
 
Joined: Jul 2003
Posts: 4,651
Likes: 17
From: Chicago IL
Default
the pcm will use the last values in the cells as it goes past 8k...
RPM limits are 12800... its a pcm resolution thing..
Reply
0

Trending Topics

Old Dec 16, 2011 | 12:28 AM
Share
  #8  
ZTwentyAteU's Avatar
ZTwentyAteU
TECH Fanatic
iTrader: (12)
 
Joined: May 2005
Posts: 1,250
Likes: 0
From: Nashville, TN
Default
^ exactly. How far is the res on the newer pcm's? the...is it green and blue connnectors? i cant remem the numbers. haha

I can tell you mines seen 8200 more than a few times..of course, it also blew up eventually haha
Reply
0
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Dec 16, 2011 | 12:40 AM
Share
  #9  
soundengineer's Avatar
soundengineer
8 Second Club
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (16)
 
Joined: Jul 2003
Posts: 4,651
Likes: 17
From: Chicago IL
Default
Originally Posted by ZTwentyAteU
^ exactly. How far is the res on the newer pcm's? the...is it green and blue connnectors? i cant remem the numbers. haha

I can tell you mines seen 8200 more than a few times..of course, it also blew up eventually haha
the newer pcms are higher resolution, but they limit to 8192...
which is pretty screwed up if you ask me..

but hey, twice the data rate of ls1 pcm's
Reply
0
Old Dec 16, 2011 | 08:28 AM
Share
  #10  
ZL1Killa's Avatar
ZL1Killa
TECH Resident
iTrader: (17)
 
Joined: Sep 2004
Posts: 3,747
Likes: 0
From: NC - Charlotte area
Default
its 2 ^ 13. 8192. gotta understand the chip(s) and programming
Reply
0
Tags
Back to Subforum
PCM Diagnostics & Tuning
View Next Unread
BEST Computer Tuner?




Advanced Search

All times are GMT -5. The time now is 11:19 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE