help with cam info...?

**Azeroth** · 01-13-2010 11:26 AM

so i've read a lot about whatever the cam is, and watched some videos on how it works, but i am by no means experienced at all with engines so it was a bunch of gibberish to me. i hear a lot about people having problems with their cam follower, or upgrading it. what does it even do? can anybody help me out in more simpler terms so i can get an understanding of it? thanks!

**bblume** · 01-13-2010 11:43 AM

http://en.wikipedia.org/wiki/Camshaft

we have two cams on top (DOHC) and one is an intake and one is an exhaust cam.
because of the immense pressure required to roll with an fsi motor, our FP runs on the intake cam (the one on the right when looking
down on your motor at the rear of the motor {assuming you're quattro}) The FP plunger rides on a cam lobe at the back of the cam that's shaped like a rounded triangle. When the cam spins the loaded triangle spins actuating the plunger forcing fuel at 1500+psi into your motor.
Other cars run with an electronic fuel pump. The problem that's happening is the follower (the thimble like piece that rides on the lobe and goes on the end of the piston in our FP) is failing and ultimately allowing the piston of the FP to ride directly on the cam lobe scoring it.
see this thread next.

**Azeroth** · 01-13-2010 04:04 PM

so is this right (bear with me here cuz i'm trying to learn haha)... it allows fuel to go in the engine or wherever it goes to? so whats the difference between that and a HPFP if i were to get one. sounds to me like they both have to do with the introduction of fuel to the engine, is that correct?

**TheHeggi** · 01-13-2010 04:17 PM

Originally Posted by Azeroth

so is this right (bear with me here cuz i'm trying to learn haha)... it allows fuel to go in the engine or wherever it goes to? so whats the difference between that and a HPFP if i were to get one. sounds to me like they both have to do with the introduction of fuel to the engine, is that correct?

The cam follower sits between the hpfp (high pressure fuel pump) piston and the cam lobe. The follower is just a medium between the two that spreads the force of the thin, pointed piston and the wide, smooth cam lobe. The cam lobe drives the fuel pump by making the piston in the hpfp go up and down as it rotates. The speed is directly related to engine rpm. Just like the cam lobes that cause the intake and exhaust valves to open and close, there is a separate cam lobe that controls the hpfp's operation. When the cam follower wears down or out, the hpfp piston rides directly on the cam lobe, causing the piston to dig into the cam lobe, creating metal shavings that will flow through your engine and cause damage. Not only that, but piston is only so long and relies on the cam lobe being a certain size, but once that piston wears grooves into the lobe, the pump will no longer be pumping the correct amount of fuel or lose contact completely causing no fuel to be pumped. Gas will NOT be injected into the engine. You have a HPFP already, you might be looking at an upgraded HPFP that allows MORE fuel to be pumped into the engine, allowing you to make more power. The cam follower issue and upgraded hpfp are seperate issues. The cam follower is a maintenance issue whereas the upgraded design is a performance issue assuming the rest of the system is in proper working condition.

Between the threads and sites linked above and the explanations, if you don't get it after you read these, you'll probably not understand it. It's a very simple relation, try not to overthink it just because it's "complicated engine stuff". If you still don't get it, all you need to know is that you should have it inspected frequently (no more than every 10k miles), you shouldn't be charged more than 2 hrs of labor for the job, and the flat side of the follower should be flat and still have nearly all of it's black coating and the cam should be smooth and mirror like. If the cam is scratched, be sure they're not significant scratchs by using your fingernail to scratch it to verify slick smoothness or rough scratches.

**Azeroth** · 01-13-2010 05:06 PM

ok im getting it more and more thanks. good explanations. so if i wanted to upgrade, it would be the cam follower right? so would i be able to get an upgraded one and install it without any other upgraded parts? or are there essentials that go along with an upgraded cam follower. sounds to me like the fuel pump and cam kinda go hand in hand. would it be smart to upgrade the fuel and the cam follower at the same time? what type of performance gains does and upgraded cam follower provide? thanks guys. plus one for rep

**bblume** · 01-13-2010 08:41 PM

Originally Posted by Azeroth

ok im getting it more and more thanks. good explanations. so if i wanted to upgrade, it would be the cam follower right? so would i be able to get an upgraded one and install it without any other upgraded parts? or are there essentials that go along with an upgraded cam follower. sounds to me like the fuel pump and cam kinda go hand in hand. would it be smart to upgrade the fuel and the cam follower at the same time? what type of performance gains does and upgraded cam follower provide? thanks guys. plus one for rep

You should just go start taking things apart....
No seriously, you would only want to change out your follower if it is damaged. I wouldn't change it out just to change it out as it has no performance gain. AN UPGRADED HPFP (b/c you already have a HPFP in your car) would allow you to go Stg2+ or run a bigger turbo.
At this point you need to keep reading cam follower threads....and if you have fuel cut-like symptoms ie no power while in a high gear while under load, then you should check the follower (or pay someone else to). Go and take your engine cover off, look at the very back of the motor near the firewall on the right top of the motor. There's a little cylinder thing sticking out at an angle with a plug coming off of it. That's your HPFP, if you were to remove that the HPFP piston would have a follower (thimble-like object) sitting on it. If you looked into the hole that would remain, you'd see a glimpse of the camlobe which the follower (and therefore the piston) rides on. I'm sure someone has some pics on here or you could look in the thread I posted for you...inside there is a link to my initial thread when my follower failed and was replaced under CPO warranty. I'm so tired of typing my wrists hurt...so there ya go!

**Azeroth** · 01-13-2010 10:34 PM

haha sorry to have you write novels but it helps me understand. great info +1 for rep. ok i have a way better understanding of it all. still got room to learn but definitely am gaining knowledge. thanks again

**Zacko** · 01-14-2010 08:23 AM

This is good onfo. I am also experiencing a fuel cut at higher rpm's while at WOT. The explanations have helped me to understand how the cam follower affects that. Good info, BBlume and Heggi...thanks guys.