Tuning with a agressive cam

[bakes]

How to adjust a cal for a aggressive cam (low Vac at idle) ? I noticed this on my LS running a FM475 an now on Dick car (Boost geek) with a very aggressive cam that when at a idle the vac is around say 7-10" that the FPR starts to ramp up the fuel pressure
causing the AFR to richen up big . i don't want to turn the pressure down in fear of going lean on top.

Vids of Dick's new big valve modified 1 piece intake motor
http://s91.photobucket.com/albums/k302/boostgeek/?action=view&current=100_4014.mp4

and the link to his tread
http://www.turbo-mopar.com/forums/showthread.php?t=37923

[bakes]

for the record this a race car 1st street car 2nd. and it will have to go into air care but burn that bridge when it time for testing.

[boost geek]

for the record this a race car 1st street car 2nd. and it will have to go into air care but burn that bridge when it time for testing.

If worst comes to worst, I'll just use 3 day permits.

[zin]

How to adjust a cal for a aggressive cam (low Vac at idle) ? I noticed this on my LS running a FM475 an now on Dick car (Boost geek) with a very aggressive cam that when at a idle the vac is around say 7-10" that the FPR starts to ramp up the fuel pressure
causing the AFR to richen up big . i don't want to turn the pressure down in fear of going lean on top.

If the problem really is the FPR, you could install a piece of tube with a restrictor on the engine side, the idea is to dampen the pressure pulses from the intake, smoothing out the pressure so you can tune it. If the pressure is stable, then it should just be a matter of tuning, the lower vacuum really shouldn't be a big deal as there are data points in the cal for that level of vacuum.

However, an aggressive cam will typically make the vacuum choppy, and the MAP will try to keep up, and just confuse the computer. You'll likely need to adjust the sensitivity of it at what are now your idle conditions.

I'm probably not explaining this very well, but maybe it'll inspire one of the more experienced tuners to chime in and correct me!

Mike

[risen]

I'm with zin on his restrictor suggestion and I think the explanation is just fine.

The only other suggestion I'd make is maybe tune it with the vac disconnected from the for for idle. Figure out what the average vac is, disconnect the vac line to remove the pulses, set the fpr to the correct psi for the average vac at idle and tune the idle fuel in that way. Then put the restrictor on the fpr line.

[bakes]

What size restrictor is a fare size to start with??

AND keep the ideas coming

[bakes]

I really want to get the fuel psi set before adjusting the cal.

[risen]

Idk what size to start with, maybe .030 .023? I'd see what you have laying around for mig tips and try those.

[boost geek]

I just had it running, stays a solid 43 f.p. without fluctuation. Vacuum is a pretty constant 8, and it doesn't like to idle lower than about 1200 rpm. I wanna take it for a ride, but I'll wait till it gets dark, no insurance. ;)

[risen]

I just looked at your other thread, nice work, that thing's going to be fast. I did notice that you said you haven't set your timing yet. Maybe you can try and advance it a little or check it to see if it's even sane, timing has a pretty big effect on idle quality.

[bakes]

timing set at 12* the frist vid was set at 16*
i have to call dick but i think cam advance about 6 deg do to the shaved head so i think it is about 2 deg true advanced .

[turbovanman²]

I just had it running, stays a solid 43 f.p. without fluctuation. Vacuum is a pretty constant 8, and it doesn't like to idle lower than about 1200 rpm. I wanna take it for a ride, but I'll wait till it gets dark, no insurance. ;)

43? That's too low unless your tuned for it already from your last engine.

[boost geek]

43? That's too low unless your tuned for it already from your last engine.

43 at idle.


I have the cam retarded 6.5 degrees, should have it advanced, due to the milled head.

[bakes]

http://i91.photobucket.com/albums/k302/boostgeek/camcard.jpg

104 centerline

[boost geek]

Here it is running at 6* advanced, just after having the battery reconnected. Haven't taken it out for a spin yet, but it should spool quicker having 12* of timing difference.

http://i91.photobucket.com/albums/k302/boostgeek/th_6degreesadvanced.jpg (http://s91.photobucket.com/albums/k302/boostgeek/?action=view&current=6degreesadvanced.mp4)

[Force Fed Mopar]

FWIW I've never seen any lower than 18" hg on my 2.2 w/ the FM475 cam. It has a stock 782 head and stock compression ratio.

[bakes]

I was running a Fully ported head with +1's FM475 cold it idle a 10"hg until warm then climbed up to maybe 14"hg but went like a scolded cat when into boost.

[boost geek]

Vac is 10-11" after changing cam timing.

[black86glhs]

Did the added vacuum help the idle issues and fuel pressure issues?

[bakes]

Did the added vacuum help the idle issues and fuel pressure issues?

Yes it did AFR is now 14-15.5 at idle and switching:nod:
Now we can play in the Cal :thumb:

[boost geek]

I could turn the idle down lower now, close to 1000, which I couldn't do before. Fuel pressure has always stayed constant, but now idles at aound 14 a/fr where before it was 11.5. Makes me wanna take it for a burn. :)

[GLHNSLHT2]

need upload to youtube so the stuff actually plays the 1st time around.

[boost geek]

When I get it to the track I'll youtube it.

[black86glhs]

Can hardly wait!:nod:

[bakes]

Dick did you hook the vac lines to the wastegate sol as a t2 not a t1 the cal i made you is set as a t2 you get 7- 10 psi all the time if you hook it as a t1 .
If i remember right i set the Max boost a 25psi and it was progessive with the vehicle speed.