Knock in 1st gear

[xveganxcowboyx]

No, I have ordered the evo 8 fuel pump and injectors. The fuel pump will be going in as soon as I get it, but the injectors will wait until I get some fuel control.

The car is a 91 TSI AWD. Big 16g, 2g manifold, 3" exhaust, boost controller set at 14psi, rewired stock fuel pump, egr and vacuum lines removed and capped, FMIC (a few small leaks, but nothing major). I can't remember everything right now that's going on in the engine bay. No major changes. Compression is low, but stable (110 to 120) which allowed me to run 17-18 psi on my 14b with no knock whatsoever.

I have tried to figure it out on my own, but have come up short. When it was knocking through the lower gears (most in first, but lots through third) I thought it was my dying 14b causing it. The knock was reduced when I changed the turbo, but I'm still having problems. The problem is it started without any major changes being done by me and I can't think of what would cause this condition.

So to reiterate the symptoms: Knock starts at any boost in first gear at both partial and wide open throttle. Rises to mid twenties at least which causes timing to be pulled heavily (car feels very doggy). I may be getting a little knock in second as well. Third on up runs smoothly with no knock until I start running out of fuel.

[94talonawd]

Originally Posted by xveganxcowboyx

No, I have ordered the evo 8 fuel pump and injectors. The fuel pump will be going in as soon as I get it, but the injectors will wait until I get some fuel control.

The car is a 91 TSI AWD. Big 16g, 2g manifold, 3" exhaust, boost controller set at 14psi, rewired stock fuel pump, egr and vacuum lines removed and capped, FMIC (a few small leaks, but nothing major). I can't remember everything right now that's going on in the engine bay. No major changes. Compression is low, but stable (110 to 120) which allowed me to run 17-18 psi on my 14b with no knock whatsoever.

I have tried to figure it out on my own, but have come up short. When it was knocking through the lower gears (most in first, but lots through third) I thought it was my dying 14b causing it. The knock was reduced when I changed the turbo, but I'm still having problems. The problem is it started without any major changes being done by me and I can't think of what would cause this condition.

So to reiterate the symptoms: Knock starts at any boost in first gear at both partial and wide open throttle. Rises to mid twenties at least which causes timing to be pulled heavily (car feels very doggy). I may be getting a little knock in second as well. Third on up runs smoothly with no knock until I start running out of fuel.

Your compression should be right around 160. Id look more into that.

Also I would fix any of the boost leaks, you would be amazed at how much air is escaping when your doing 18 psi. Also, if you are still on your 1g mas, you might be over running it too, since you are leaking boost too. Or your 1g mas might just be faulty.

What are your injector duty cycle at in 3rd?

Also, your fuel pump could be dying out too. So I would consider replacing that, if it hasnt been already. It is a 10+ year old car.

Have you checked your base timing? If your knock count is going up that high the timing may have been advanced. If you haven't, check it and make sure it is back to factory specs.

[xveganxcowboyx]

I plan to rebuild it. I was going to do it around Christmas, but since it's been stable since I've owned the car (well over a year) I've decided to wait until spring.

I was leaking at a couple welds on my piping. I ground them down and fixed most of them. I still need to pressure test for the rest, but it's much better than it was. The problem started long after the install of my FMIC so I know the pipes arent the cause. (Though for good measure I will check all of my couplers)

The MAS issue is a good one. I shouldn't be over running it, because I'm not boosting much, but it may be bad. I hadn't thought of that, but I had similar issues when one went bad on me a while back. Good time to find a 2G MAS.

When I last checked my injector duty cycle the spring in my boost controller was too stiff and I was boosting 15-16psi. I was getting 110% by 6,500rpm. I have since replaced the spring and am running more conservative boost. At 17lbs on my 14B I was hitting 100% around 7,000rpm.

Fuel pump will hopefully be replaced within a week with an EVO unit so that should cure any fuel pump issues.

Checked base timing 5 or 6 months ago. It was a couple degrees off. I set it. Haven't checked it since. I'll grab my timing gun next time I get to my folks place.

[94talonawd]

Originally Posted by xveganxcowboyx

I plan to rebuild it. I was going to do it around Christmas, but since it's been stable since I've owned the car (well over a year) I've decided to wait until spring.

I was leaking at a couple welds on my piping. I ground them down and fixed most of them. I still need to pressure test for the rest, but it's much better than it was. The problem started long after the install of my FMIC so I know the pipes arent the cause. (Though for good measure I will check all of my couplers)

The MAS issue is a good one. I shouldn't be over running it, because I'm not boosting much, but it may be bad. I hadn't thought of that, but I had similar issues when one went bad on me a while back. Good time to find a 2G MAS.

When I last checked my injector duty cycle the spring in my boost controller was too stiff and I was boosting 15-16psi. I was getting 110% by 6,500rpm. I have since replaced the spring and am running more conservative boost. At 17lbs on my 14B I was hitting 100% around 7,000rpm.

Fuel pump will hopefully be replaced within a week with an EVO unit so that should cure any fuel pump issues.

Checked base timing 5 or 6 months ago. It was a couple degrees off. I set it. Haven't checked it since. I'll grab my timing gun next time I get to my folks place.

Definitly get a 2g mas. You may not be boosting much, but when the mas draws in air, some of it is going to leak through boost leaks, then the mas is going to draw in more air again to replace the boost that is leaking. Which ends up in your mas over running. This also makes you run richer too, because the mas is counting air that isnt getting sucked in by the engine, but rather being dispersed into the atmosphere via boost leaks, and your ECU doesnt know that, so its reading more air, which means its going to send more fuel. This also then raises the injector d/c to a higher point than it should be, and causes the fuel pump to not be able to support this much amount of fuel that is needed. So all of this is going to account for your car to go FDRTHRTHAEFGARHGFDVXVBAR!!!

So...

FDRTHRTHAEFGARHGFDVXVBAR!!! = Knock

Well, atleast thats what I came up with, lol.