From a post I made in the crutch section :

Taking advantage of 2:1 back pressure .

I've had some trouble between steet tune and track tune . My AFRs are 12:1 on C-16 and it likes it there . The problem is , its very rich on my pump gas tune . So rich its been hurting spool . I had the PVs to open at 3psi and when they open its like flood gates . lol AFRs would drop to low 10s and hurt power bad .

Now I've tried to open these PVs with just hat pressure and it doesnt work so I got to thinking about my 2:1 back pressure .

:ding:

Teed into my back pressure line in the turbine flange and and ran a line to the solenoid that opens at 3psi . At 11psi of boost there is 22psi on the PVs now .

AFRs at 11psi of boost are 11.5 now and its pulling like a freight train .

Even at 22psi on the PVs they are still not open all the way ,( proven by the AFRs not being in the 10s anymore ) , but just enough for perfect transition into boost and enough fuel to hold 11.5 AFRs .

 

Nice work Dave. You are really getting a handle on that system.

 

Damn never thought about using backpressure. Damn good idea.

 

wow dave simple but genius

 

I first tested how much pressure it takes to open Brents PVs . I just put air on them with a gauge and while in park brought the RPMs up around 2500 . The motor went rich and started stumbling at around 10psi . So I figure the hat pressure should open them far enough to get the AFRs where I wanted them . WRONG . Its amazing how much fuel bowl pressure works against the PVs ............ Even with 15psi of hat pressure on the PVs , AFRs were in the high 13's low 14's . ( I had already done this last year , dont ask me why I thought the out come would be different .)

I get it back home and I was just staring at the motor in a daze wondering WTF can I do , when I looked down and saw the line I used to measure back pressure . I thought yea , thats going to work . lol

22psi of back pressure on the PVs with 12psi in the manifold is just enough to overcome fuel bowl pressure and keep AFRs at 11.5 .

 

Yeah but... brianj5600 is opening his with fuel pressure which is only 6-7 higher than the hat. Wonder if his are fully open?

 

I'm thinking the spring that Brent uses is pretty stiff . But still , 22psi is only 7psi more than hat pressure . I have 15 in the hat and 11 to 12 in the manifold .

Just got back from a drive and could only get 17psi of back pressure at 12psi of boost . :scratch: AFRs were 12.5 . Heat and weather play a big role you think ?

I think I'll go to a lighter spring or cut the ones that are in there .

Weird how back pressure can be 22psi one day and 17psi the next with the same boost .

 

How do you like the balancer? Looks like a nice piece!! Seen one on larry larsons 6 second nova this past weekend!! With the bulit in tabs for crank trigger, bad ass!!

 

As long as it does its job , I like it alot .


But seriously , its a very nice piece . Like I said earlier , its almost to pretty to put on the motor . It should be under a piece of glass for viewing . 8)

 

put a lighter spring in the primary and its all good .

 

I finally made a log of the AFRs . This is a 2nd to 3rd gear pull on the street . Crutch solenoid set to open at 4psi manifold . Then its turbine pressure on the PVs .

AFRs are in the 13s as I get on it . Keep in mind I have a 1:1 linkage and it helps transition into boost dramatically .

Its a little fat when the PVs open but not bad at all . No stumbles . AFRs come up during the shift but comes back down as soon as load comes back . I'm assuming this is the loss of turbine pressure on the PVs during the shift . But once in 3rd the AFRs are good and I can assure you they will stay there as long as I can stay in it .

 

Heres the pre and post intercooler temps . No ice just water . Same run as above .

 

Dang, that's a pretty pimp intercooler you got there.
Those are pretty nice without ice.

 

Its a shame you cant that thing of beauty . Its all hidden away .

But we know .

 

Sent a customer the link here to your temps. He's fighting my kung fu. Wants to put a HE on

 

Are those 195's out of the box? What springs?

 

yes ... out of the box , but springs were changed . AFR # 8019

The numbers are very good according to Mark at Bullet Cams .

I think you can order the 195street heads with the springs as an up grade . Or the 195cc Street Competition head comes with those springs and flows better .

http://www.airflowresearch.com/index.php?cPath=24_29

I just have the regular 195s .

 

Tell him to put that money somewhere else .

 

Made it to the track today . Got two runs all day .


Dont know where it came from , but it picked up 3mph . lol

21psi crossing the line at 6200rpm . AFRs 12.0

60'.............. 1.38
330 ............ 3.93
1/8 ............. 6.06
MPH ............ 115.64
1000 ........... 7.90
1/4 .............. 9.46
MPH ............ 146.94


147mph !

 

That's hauling the mail!!!!