A lag monster is spawned! (cam timing)

RSMike · Oct 30, 2009, 05:15 PM

Hi,

i just chucked in my kelford 272's into my mirage.
Max boost went from about 3400rpm to about 3800-3900 rpm, with transient throttle response lacking.
I haven't put in my adjustable cam gears yet, they're on the way from the US.
I have then put my FP Red on that just arrived, and so i'm getting full boost at about 4500rpm (in 3rd/4th, 5th is about 4200).

My question is -
How do i adjust the cam gears to get maximum throttle response and the quickest spooling possible?

Also, with the FP Red, would putting a 9.8hotside onto it actually increase response? or just kill top end power?

Cheers

Aby@MIL.SPEC · Oct 30, 2009, 06:30 PM

people say that the kelford 272's are similar to the cosi m2's.....which i have + a fp-red....what worked for me, was +2int / 0exh for the cam gears.

it offered better response while still making decent power @ a more desirable rev range for me.....

you really need to move the intake cam around a bit & go from there...

RSMike · Oct 30, 2009, 06:50 PM

thanks mate.
my fidanza cam gears should be arriving next week from the US.
I'm drag racing on the friday, so hopefully i'll get something sorted before then

Cheers, Mike

03whitegsr · Oct 30, 2009, 09:45 PM

You picked one of the most aggressive cams out there. Those cams are built for top end.

Why strangle them with a smaller housing and cam timing?

Either run them where they are supposed to be ran, or pick a less aggressive cam.

norcalSRTrida · Oct 30, 2009, 10:31 PM

^^^ x2

closing up some of the overlap will help bring back some bottom-mid

Dave W. · Oct 30, 2009, 11:15 PM

If you're drag racing, why are you worried about spoolup?

gfng · Oct 30, 2009, 11:53 PM

im on kelfords , and saw no loss in spool or power ,

RSMike · Oct 31, 2009, 04:42 AM

i'm modifying my car in stages.
even though i'm drag racing this car, it's a daily driver and i want to do the odd track day in it.
i was just surprised at the amount of lag the cams created, was just wondering if other people have experienced the same thing. but like i said, cam gears are on the way.
hopefully they'll fix up my problems straight away!
cheers

Dave W. · Oct 31, 2009, 12:29 PM

Here's a good tech article for adjusting cam gears. When you get them I'd recomend advancing the intake cam by one or two degrees and see how it goes.

http://my.prostreetonline.com/forums....php?t-117.htm

Evo8luva · Oct 31, 2009, 01:12 PM

I played with mine a little bit and ended up back at 0/0. +3 on intake and 0 on exhaust is what I ran along with some tuning adjustments to smooth the idle out, and it also felt like it shifted the power band a little earlier, but gave up a little bit on the top end, even with the stock 9 turbo... So for drag I went back to 0/0

black E · Oct 31, 2009, 05:44 PM

what about the S2's on a red?! anybody tried advancing the intake cam with this setup?

Ted B · Nov 1, 2009, 03:20 AM

Quote:

Originally Posted by RSMike

i just chucked in my kelford 272's into my mirage.
...
My question is -
How do i adjust the cam gears to get maximum throttle response and the quickest spooling possible?

First, advance the intake cam by one degree while advancing the exhaust cam by one degree at the same time. Next, leave the intake cam at +1 and try advancing the exhaust cam by one more degree. Note any differences.

RSMike · Nov 1, 2009, 04:00 AM

Quote:

Originally Posted by Ted B

First, advance the intake cam by one degree while advancing the exhaust cam by one degree at the same time. Next, leave the intake cam at +1 and try advancing the exhaust cam by one more degree. Note any differences.

Thanks for your ideas. Hopefully i'll get my cam gears on monday or tuesday.

whats the theory to advancing the exhaust camshaft? to reduce overlap?

I've got a pretty good grip on most mechanical and performance theories.
But cam timing kinda has me stumped.

I thought that large overlap was desired for high rpm and small overlap was for low rpm.
This is why large cam/large overlap engines need to idle high etc or they will stall (3000rpm etc).

But alot of people are stating that increasing the overlap will increase bottom end power and spoolling characteristics?

Ted B · Nov 1, 2009, 05:28 AM

As you estimated, we adjust the exhaust cam primarily to tailor overlap. Overlap begins to be beneficial in the midrange, and definitely at the top. How much or little we want depends upon factors like static compression ratio, boost pressure, turbine side sizing, etc.

I am advising you to advance the intake cam slightly to bring the power a little earlier in the rpm range. After that, I am advising you to remove a little overlap to determine if that further helps your spool characteristics, but as always, you will need to evaluate this in the real world.

JohnBradley · Nov 1, 2009, 12:47 PM

Also remember that changes to the exh cam alter timing as well. Well "base timing reference" anyway so watch for knock.