Notices
GM Engine & Exhaust Performance EFI | GEN I/GEN II/GEN III/GEN IV Engines |Small Block | Big Block |

Why is my 408 a dog down low?

Thread Tools
 
Search this Thread
 
Old 01-16-2007, 04:23 PM
  #101  
High on diesel fumes
Thread Starter
iTrader: (70)
 
thunder550's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 12,658
Likes: 0
Received 3 Likes on 3 Posts
Default

Thanks for the ideas guys! I'll check all this out when I get home. I need to do some more logging, I have a set of PID's set up to log EVERY spark PID there is. I tried it yesterday and didn't see anything, but I didn't look real close.
Old 01-16-2007, 04:24 PM
  #102  
12 Second Truck Club
iTrader: (4)
 
TURBHOE's Avatar
 
Join Date: Nov 2004
Location: Jacksonville FL.
Posts: 6,318
Likes: 0
Received 2 Likes on 2 Posts
Default

found this in hpt. The VCM constantly looks up both High Octane and Low Octane spark tables and interpolates a value between the two tables based on the current Knock Learn factor. If the engine has been operating for a moderate time without any Knock Retard then Knock Learn is zero and the interpolation favors the High Octane table, if Knock has been detected then the interpolation will move towards the Low Octane table. During MAF failure the Knock Learn is set to maximum and the Low Octane table is used. are your low and high octane tables the same?
Old 01-16-2007, 04:31 PM
  #103  
High on diesel fumes
Thread Starter
iTrader: (70)
 
thunder550's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 12,658
Likes: 0
Received 3 Likes on 3 Posts
Default

Yes I made sure of that.
Old 01-17-2007, 11:43 PM
  #104  
Teching In
 
Ascrap2003's Avatar
 
Join Date: Jan 2007
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
Default

What is your combo? Are all your parts & mods matched?

If they are, you'll just need a converter, if not back to the drawing board.

When you build an engine all the parts need to work in harmony.

You can't take a race came that was meant to make power in the 4,000 - 7,000 range and put it in a engine that was built by GM techs to operate at idle - 5,000 rpm. Same with everthing else if you have a full blown race engine and the thing is set up to make power in the 4,000 - 7,000 range and you drop a stock cam in it it won't run worth crap! Get it?
Old 01-17-2007, 11:52 PM
  #105  
TECH Senior Member
iTrader: (26)
 
kbracing96's Avatar
 
Join Date: Jul 2004
Location: Oakland, OR
Posts: 9,485
Received 30 Likes on 28 Posts
Default

Originally Posted by Ascrap2003
What is your combo? Are all your parts & mods matched?
read his sig...
Old 01-18-2007, 12:29 AM
  #106  
TECH Veteran
iTrader: (24)
 
RandomHero's Avatar
 
Join Date: Jun 2005
Location: Austin,TX Name:Mark
Posts: 4,787
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by Ascrap2003
What is your combo? Are all your parts & mods matched?

If they are, you'll just need a converter, if not back to the drawing board.

When you build an engine all the parts need to work in harmony.

You can't take a race came that was meant to make power in the 4,000 - 7,000 range and put it in a engine that was built by GM techs to operate at idle - 5,000 rpm. Same with everthing else if you have a full blown race engine and the thing is set up to make power in the 4,000 - 7,000 range and you drop a stock cam in it it won't run worth crap! Get it?
Sorry, but from the nature of this post I get the feeling that you are a 40+ guy who knows alot about classic cars, but probably not alot about LS1 based engines.

No LS1 based engine is built to operate only till 5k rpms. Sure everything has to be compliable together, but your theory is for the most part outdated.
Old 01-18-2007, 09:51 AM
  #107  
High on diesel fumes
Thread Starter
iTrader: (70)
 
thunder550's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 12,658
Likes: 0
Received 3 Likes on 3 Posts
Default

I said it earlier in the thread, but the cam I have in there was designed to make power from about 2100-just over 6000 RPM, which is exactly what I wanted and exactly where I'm planning on running the motor.

As far as the timing issue goes, I got it figured out with the help of dc_justin and XLR8NSS.

https://www.performancetrucks.net/fo...d.php?t=383764

Now I gotta mess with the timing table some more, but I think it's going to wake up nicely. I just added 2* of timing when stalling up and now the tires try to spin while I'm sitting still. No KR, so I'm going to keep adding away.
Old 01-18-2007, 10:39 AM
  #108  
TECH Addict
iTrader: (18)
 
Zick's Avatar
 
Join Date: Jun 2004
Location: WI
Posts: 2,247
Likes: 0
Received 0 Likes on 0 Posts
Default

Glad to hear you got it figured out. Isn't tuning great!
Old 01-18-2007, 02:03 PM
  #109  
High on diesel fumes
Thread Starter
iTrader: (70)
 
thunder550's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 12,658
Likes: 0
Received 3 Likes on 3 Posts
Default

Oh yeah, but it feels so good when you figure out what's wrong

I'm up to 28* across the board now with no KR.
Old 01-18-2007, 04:08 PM
  #110  
12 Second Truck Club
iTrader: (4)
 
TURBHOE's Avatar
 
Join Date: Nov 2004
Location: Jacksonville FL.
Posts: 6,318
Likes: 0
Received 2 Likes on 2 Posts
Default

good deal, i've never had any problems like that in hpt. let us know how i runs once you get it all tweaked out.


Quick Reply: Why is my 408 a dog down low?



All times are GMT -5. The time now is 02:21 PM.