home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > performance & modifications

Reply
 
Thread Tools Display Modes
Old 06-07-2021, 10:19 AM   #1
VB242
Beep beep zip tang
 
VB242's Avatar
 
Join Date: Sep 2011
Location: The Right Coast
Default Adjustable cam gear help

I'm having issues with detonation after I retarded the cam timing on my 8V B23+T, enough to pop the GD head gasket once again. I keep adding fuel, the timing is 7 degrees in the range I'm getting the knock. Is there something I don't understand about dynamic compression ratio that I will not be able to tune this problem away? It's an IPD turbo cam, microsquirt, fuel system and injectors are fairly new. I'll be testing volume from the injectors to rule that out. It runs fine though the rest of RPM range and only knocks between 10-15psi around peak torque.
__________________
Quote:
Originally Posted by 240240 View Post
I'm shocked someone actually took me seriously.
VB242 is online now   Reply With Quote
Old 06-07-2021, 11:51 AM   #2
shoestring
Board Member
 
shoestring's Avatar
 
Join Date: Jun 2009
Location: Swampscott, 01907
Default

What's the compression ratio on this B23?
__________________
I AM THE MODAL AMERICAN. Planet money #936.
shoestring is offline   Reply With Quote
Old 06-07-2021, 12:02 PM   #3
740atl
rb67 life
 
740atl's Avatar
 
Join Date: Apr 2010
Location: USA
Default

I had to retard the hell out of the ignition timing...the only way I could get the +T to not knock.... but especially around the torque peak (3500 or so rpm for an 8v)... after the torque peak it's ok to have a little knock, but it's most devastating at the torque peak.

I'll tell you what though.... the moment I switched to e85, I was able to add most of the timing back.
740atl is offline   Reply With Quote
Old 06-07-2021, 12:27 PM   #4
culberro
Ronald Culberbone III
 
culberro's Avatar
 
Join Date: Feb 2010
Location: Portland, OR
Default

Retarding the cam timing will raise the DCR and usually make low end know worse. Try advancing the cam a few degrees to bleed off some of the DCR at lower revs, or a bigger cam.
__________________
Cult Person. Pissing in your Kool-Aid.
culberro is offline   Reply With Quote
Old 06-07-2021, 01:52 PM   #5
VB242
Beep beep zip tang
 
VB242's Avatar
 
Join Date: Sep 2011
Location: The Right Coast
Default

Quote:
Originally Posted by culberro View Post
Retarding the cam timing will raise the DCR and usually make low end know worse. Try advancing the cam a few degrees to bleed off some of the DCR at lower revs, or a bigger cam.
It has stock B23ET pistons and a 530 head, opened up a little around the intake valve, which i believe should be 8.5:1, I didn't have any problems with 25psi before I installed the cam pulley. I have a 3.35 first gear with a 4.10 rear, so it has plenty of jump off the line, I was trying to get a little more top end for autocross.
VB242 is online now   Reply With Quote
Old 06-07-2021, 03:01 PM   #6
culberro
Ronald Culberbone III
 
culberro's Avatar
 
Join Date: Feb 2010
Location: Portland, OR
Default

Got ya, something seems off in the setup.
culberro is offline   Reply With Quote
Old 06-07-2021, 06:13 PM   #7
740atl
rb67 life
 
740atl's Avatar
 
Join Date: Apr 2010
Location: USA
Default

Have you measured the actual timing at the crank at a few rpms?
740atl is offline   Reply With Quote
Old 06-07-2021, 10:19 PM   #8
VB242
Beep beep zip tang
 
VB242's Avatar
 
Join Date: Sep 2011
Location: The Right Coast
Default

Quote:
Originally Posted by 740atl View Post
Have you measured the actual timing at the crank at a few rpms?
No I did not.
VB242 is online now   Reply With Quote
Old 06-08-2021, 11:12 AM   #9
740atl
rb67 life
 
740atl's Avatar
 
Join Date: Apr 2010
Location: USA
Default

The only reason i say this is to verify that the timing you have programmed in the spark table is what's actually showing up in the cylinder. It's a pain to do with one person but have a bud rev the engine while checking it with a timing light on the crank to see if your 30 degrees at 2500rpm/50kpa isn't really 55 degrees.

It's a relatively quick check that could explain why you're getting severe knock on such a low compression setup.
740atl is offline   Reply With Quote
Old 06-08-2021, 11:37 AM   #10
VB242
Beep beep zip tang
 
VB242's Avatar
 
Join Date: Sep 2011
Location: The Right Coast
Default

Quote:
Originally Posted by 740atl View Post
The only reason i say this is to verify that the timing you have programmed in the spark table is what's actually showing up in the cylinder. It's a pain to do with one person but have a bud rev the engine while checking it with a timing light on the crank to see if your 30 degrees at 2500rpm/50kpa isn't really 55 degrees.

It's a relatively quick check that could explain why you're getting severe knock on such a low compression setup.
I totally agree with you, I'm bringing the timing light home tonight to check
VB242 is online now   Reply With Quote
Old 06-08-2021, 08:12 PM   #11
VB242
Beep beep zip tang
 
VB242's Avatar
 
Join Date: Sep 2011
Location: The Right Coast
Default

Soooo yeah, it was totally the static timing, I forgot the timing light at work when I put the pulley on at home. And over estimating my mechanicing skills I just assumed i had the timing belt and pulleys back where they started from. It did have a lot of power of course with the static timing advanced 9 degrees, I need i get it to the dyno and work on the timing cause there's definitely more to be had. . And much to my great relief my coolant leak appears to be the coolant pipe that runs from the water pump to the heater hose behind the block and not blown HG, I also just figured that puddle was from the coolant bottle. I need the one that works with the 940 water/ oil cooler, thankfully there's a 940 turbo at the pick and pull. I even ordered new ARP studs from Yoshifab and an Elring HG kit from FCP. I reckon I'll be ready if/ when I do blow the HG again.

Last edited by VB242; 06-08-2021 at 08:20 PM..
VB242 is online now   Reply With Quote
Old 06-11-2021, 02:32 PM   #12
dl242gt
Happy playing the blues
 
dl242gt's Avatar
 
Join Date: Jun 2002
Location: S NJ, a suburb of Phila.
Default

Glad you got it running better. That's some pretty scary knock when it happens like that.
dl242gt is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 06:20 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.