donour

iTrader: (6)

Since installing HKS 272 (helix actually) cams about two months ago, I've been battling knock and an apparent need to run much less timing than a lot of other folks. What's really surprised me in the past few weeks is how little timing I'm able to run on E85.

This behavior is most obvious just free revving the engine. I get significant knock counts with a stockish map. See free-rev.zip for a an example from 94170715. One might think that there is some kind of wicked powerplant noise or that something the rattling. However, it is quite responsive to timing. I just have to drop it a lot...10 degrees from 2500-3500 @ 80-110 load. You can imagine what kind of suck that puts into the driveability.

On boost has a similiar problem with what seems to usually be very knock resistant e85. I'm at high altitude, so my powerband is narrower than most. Peak boost is 26-27 psi at 4100 RPM. I've had to drop timing to -2 in that cell. Any more will cause consistent and repeatable knock counts. This, of course, reduces actual timing values back down below -2 anyway. That's 8 degrees less than comparable car on the same fuel from the same source. The funny part is that I'm able to ramp back up to the expected values above 5000 RPM. At redline 21 degrees of timing is knock free and making good power. As a matter of fact, peak power numbers seem to be fine but torque is a pretty weak sauce. [see timing.png] On boost mixtures are 11.8-12.0:1 on a gasoline scaled wideband.

A quick list of relevant mods: intake, stock turbo, cams, cam gears, exhaust, 1050cc injectors, above 5000' altitude. The ignition system is stock all the way down to the plugs which were replaced a few thousand miles ago.

An obvious question would be whether the lifters were bled. Yes, they were. The valve train is slightly more noisy than stock but there isn't really a ticking sound. It also occurred to be that a cam gear may be off a tooth, but that would be 9 degree of cam angle and 18 degrees on the crank and should cause bigger problems than this as well as difficulty with idle and starting.

I'm very hesitant to touch any of the knock sensor tables because the knock is so responsive to changes in timing. I have no reason to think it is spurious noise. However, I'm completely out of ideas. I have lots and lots and lots of logs showing basically what I've described.

Anybody else have any?

d

AWD Motorsports

iTrader: (211)

I dont tune but some things to check is Cam sensor along with Balance shaft.. Make sure they are aligned properly..

Mike

donour

iTrader: (6)

Thanks for the suggestions. The cam sensor only goes two ways, one of which is correct. I was very careful to align it correctly per the service manual, but if I didn't then it would be 180 degrees out.

I didn't think of the balance shaft. The belt was replaced about a year ago, but I haven't touched it since then and it was run a full national autocross season in its current configuration without problems.

d

DDATuned

iTrader: (49)

Timing is off. I am 100% sure of it.

edit: Well let me not say "100%" but I think that is your issue. I have done a 100 timing belts and recently ran into this same issue. Turns out one gear was off a tooth. After running meth and e85 trying to track down the knock issue, I felt like a jerk. lol

Good luck

donour

iTrader: (6)

Thanks. It's good to get the motivation to check it again for the 4th time. EDIT: removed my stupid question.

d

donour

iTrader: (6)

Remy. Thanks for the tip. I after re-checking, the intake cam _was_ advanced by one tooth. Luckily, this was within my cam gear's adjustment range and was very quick to fix. However, it didn't seem to affect the knock issue at all.

d

GST Motorsports

iTrader: (8)

The helix cams are bit of piles. Some are good some are warped. I've seen a set that where warped with my naked eyes.

Helix parts are made with the highest profit percentage possible, which means as cheap as possible with the highest profit possible.

- Bryan

donour

iTrader: (6)

I appreciate your candor. I'm about ready to swap stock cams back in to see if that makes the problem go away, but I haven't given up yet.

donour

GST Motorsports

iTrader: (8)

are you sure a lifter hasn't collapsed?

In all honesty your timing map doesn't seem too far off.

Do you have a WOT log?

- Bryan

donour

iTrader: (6)

Not 100%, but fairly sure. I was careful to bleed each by sticking an allen wrench in and then actuating it. If one was faulty in some way, it would make a racket at idle, no?

That timing map knocks, at both low load and peak torque.

I've attached a a very short one that shoes a WOT between 2900-3500. Boost comes on, timing goes down, the car knocks, then I lift. The log is from last night, AFTER I fixed the intake cam. Fuel is straight class 3 E85.

d

donour

iTrader: (6)

*more data*

I've attached another free rev log. Look at tip-in. It's going very, very rich right before it starts knocking. Too rich?

EDIT: I'm using FIC1050 injectors, a walbro 255 fuel pump. The only maps I've adjusted are injector scaling, injector latencies, and main fuel. Although, for these load cells, the fuel map is stock. Are there enrichment maps that need to be adjusted?

EDIT2: lean spool is disabled.

d

donour

iTrader: (6)

Update:

The car made 360/360 on the dyno last friday. Exactly one year ago it made 303/310 on the same dyno, with stock cams on 91 octane. It doesn't make the giant torque numbers that a lot of E85 cars do, but I'm only running about 26 psi of boost. If you adjust for altitude, that's only 24 for you sea-level folks. My timing map is still retarded though. A peak torque:

* -1 degrees make 340 ft.lbs
* +1 degrees makes 360 ft.lbs
* +2 degrees knocks

Peak power was made at 7000 RPM, 11.8:1 mixtures, 19 degrees ignition advance.

My fueling system seems fine. It was completely consistent throughout the 25 pulls, including the last 5 which were back to back. I'm still running the original plug wires at 68k miles and 68 months. I guess I'll replace those next...

d

donour

iTrader: (6)

Update:

I pulled the plug wires. The terminal on the 4->1 cable was corroded [see photo]. I didn't bother to check the resistance. I just put new ones in because the factory manual told me to.

It didn't seem to have any effect. It still knocks while free revving and at tip-in as originally described.

I guess I'm going to look at the accel-enrich table next. Maybe it needs to be different with my ginormous injectors.

d

jid2

iTrader: (62)

Did you ever check the cams? This seems bizarre with a stock block.

donour

iTrader: (6)

I agree. It is very bizarre.

Check as in put the stock cams back in? No, not yet.

d