High CR question
Thread Starter
Launching!
Joined: Feb 2012
Posts: 213
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From: LJC via STL
High CR question I'm currently running 11.0:1 CR on a forged iron block 347.
The parts list on the lower end listed in the picture below:
I have it paired with a Futral f14, 232/234 .598/.598 114+2lsa cam shaft. Ported 243's.
I'm running a procharger f1. Will my dynamic Compression end up being to high? What could I do to make the setup work? Or do I need to change things on the setup?
Any help is greatly appreciated.
The parts list on the lower end listed in the picture below:
I have it paired with a Futral f14, 232/234 .598/.598 114+2lsa cam shaft. Ported 243's.
I'm running a procharger f1. Will my dynamic Compression end up being to high? What could I do to make the setup work? Or do I need to change things on the setup?
Any help is greatly appreciated.
Thread Starter
Launching!
Joined: Feb 2012
Posts: 213
Likes: 0
From: LJC via STL
CR is 11.0:1. Currently running 93 octane. The tuner said he had the timing all the way to 0 and I was still getting spark knock at 4500-5000 rpms. Max boost I'd want is 15 psi.
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8.34 DCR according to my calculator and that is with the piston in the hole with stock specs(-.006)
Which will work fine on pump gas, but I'd use methanol injection with 100% for the added octane.
The ls1 computers have an issue with picking up false knock in the peak torque or max load areas, especially in the rpm area you are speaking of.
If he had it all the way down to 0 degrees timing then it's not spark knock.
What do the plugs tell you? Any shiny aluminum speckling on the porcelain? Any black peppering on the porcelain? What plugs are you running? Hopefully not a projected tip TR6...
The plug will tell the true tale.
Which will work fine on pump gas, but I'd use methanol injection with 100% for the added octane.
The ls1 computers have an issue with picking up false knock in the peak torque or max load areas, especially in the rpm area you are speaking of.
If he had it all the way down to 0 degrees timing then it's not spark knock.
What do the plugs tell you? Any shiny aluminum speckling on the porcelain? Any black peppering on the porcelain? What plugs are you running? Hopefully not a projected tip TR6...
The plug will tell the true tale.
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Launching!
Joined: Feb 2012
Posts: 213
Likes: 0
From: LJC via STL
The plugs were speckled, but he ran it on the dyno the first pass super lean.. Looking more and more like a tuning issue..
Pistons are flat tops, motor was originally built for nitrous. Plugs are Br8's I believe.
Pistons are flat tops, motor was originally built for nitrous. Plugs are Br8's I believe.
B8's(they are B8's for sure if they are NGK part number 1049) are what I would use also, some people seem to can't get over using that "cold" of a plug but that's the plug I would use in your set-up and many others.
Hmm, when you say timing was at 0 you mean he took it all the way down to 0 degrees during the pull and it still showed knock?
Put a new set of plugs in it, put the timing at 10* from the rpm your first see boost to red line and put the AFR at 11.4. Make a pull/pass where ever you can safely and easily shut it down after the pull by cutting the car off at the end of the pull/run. Make sure when you do this you do it as close to the way you would run it at the track. You can also do a 3rd gear pull from say 40-50mph and run it up to 6000-6200rpm and then pull them if you do it on the roadway.
Just make sure you get significant heat in the plug so you can get a true reading and post the pictures up here or PM them to me.
A lot of times with the LS1 pcm's we have to pull the timing back 1-2* sometimes as much as 4* between 4000-5000rpm because of the knock sensors on these cars. That is if you keep them as sensitive as they are now.
Most of the time you can cut the knock sensitivity in half and it will eradicate this problem while still keeping working knock sensors.
Last edited by Fbodyjunkie06; Jul 15, 2012 at 07:04 PM.
