Thanks for the tip. That's _exactly_ who I'd like to talk to.

-p

 

nuff said



Gotta pay to play - especially if you want to win the Targa

AMS UK

 

subscribed for results with cams

 

Okay people, here's the story. I've got good news and bad news.

The good news is, we fixed the boost problem on my car. Shiv discovered that one of the factory pills was missing and keeping the computer from boosting. It was a quick fix and he was able to get the car to boost as expected. Why this wasn't done during my first dyno tune is a bit confusing to me, but whatever. :-/

The bad news: the car was misfiring badly.

It was consistently breaking up at ~7000RPM, keeping us from being able to do any sort of real run. We tried swapping the spark plugs, wires, and coils from Shiv's car to see if that made a difference, but to no avail. Kept doing it whatever we did.

After we installed the cams, I didn't push the motor very hard as I didn't know what the air/fuel curve looked like after the mod. Otherwise we would have noticed the misfire. I revved the car hard after I left the dyno just to get a feel for when it was misfiring. Unlike on the dyno, the misfire happens even lower in the rev range when pushing the car hard on the street. It sounds like machine gun fire as unburned fuel ignites in the exhaust tract.

Shiv suspects that it's actually being caused by valve float due to using the stock valve springs. I called Works, who has experience with these cams, and they have not heard of anything like this with a stock valve train, but agreed that it was theoretically possible that that is the cause. As Works has experience with these cams, I'll be bringing the car to them next week. We'll swap in the upgraded valve springs and retainers and see if that kills the misfire problem. If not, I'll be yanking the cams and going back to something that I know works.

The result? So, it looks like I'll be going back for a THIRD time to Shiv to try to get this car sorted out. I guess that's the price you pay for trying to mod a new car.

The good news is that the car did make pretty good power even with the misfire. It peaked at ~300whp and ~320lb/ft of torque. And that was without any real tuning. The dyno plot did not drop as we got closer to redline, so there seems to be more power in these cams with a real tune. We'll find out soon enough, as I plan to get the car back on the dyno as soon as we can sort out the misfire.

One other note on these cams -- they kill your idle. The idle on the car is really, really lumpy. It jumps up and down and threatens to die all the time. We didn't do anything about it because of the misfire, but I'll ask Shiv to try to do something about that when it's back on the dyno.

I'll post a picture of the dyno sheet later tonight for those who care.

 

I sincerely doubt its the valvetrain, you may want to keep looking for other reasons besided your valve springs, Cosworth does not require valvesprings unless revving beyond the limits of the stocks........

 

If you don't think it's valve train, what do you think it is? We swapped plugs, plug wires and coils and saw the same thing. I'm open to suggestions.

As for what Cosworth said, read my blog . I called them and asked them directly before installing the cams (I actually bought the upgraded valve train parts) and they said that it _should_ be okay, but that valve float is a possibility.

Either way, we'll find out for sure next week.

 

GOOD LUCK !!!!

hope you find the problem.

 

I would look other places than the valve springs as the culprit. I have yet to see anyone do testing to prove the strengths or limits of the stock valve springs. Was the tuning done through an xede? if so have you tried bypassing it? Have you checked all components to make sure the motor is timed properly? Try narrowing things down one at a time.

 

I posted the dyno plot here in my blog.

 

There's definitely a known issue with valve float with aggressive cams. I also am suspicious of this as the sole culprit, but I'm willing to try it out.

The tuning was done with the Xede by Shiv himself. According to him, the XEDE was disconnected for one of the runs and it was still misfiring.

 

I have run several different cams with the stock valvetrain with no problems, I now run a 280 ex cam on my 9 with no problems.
Process of elimination, checking spark is only the beginning.

 

Okay, so using process of elimination, what should I check?

 

Your problem sounds like the problem I was having. It was solved by adding the HKS DLI 2. The theory was that spark squelch was taking place because the stock ignition couldn't handle the increased air flow. This happened when I changed my turbo and cams to HKS 280s, but the problems you describe are indentical.

It is cheaper and easier to "borrow" a DLI and check it out than change the valve train, but if you plan on doing it anyway, go ahead.

 

Shiv knows all the little tricks I'd try, but the first thing I'd do would be to gap your spark plugs way down to around .022. What kind of plugs are you using? If you are using the iridiums, you aren't supposed to adjust the gap on those and if so, maybe Shiv left them at the recommended gap, which is around .028.

 

Robert,
That is certainly worth a try, but I have seen lots of Evos, including mine, making anywhere's from 505 to 585whp on the stock ignition with no misfire at all, once the spark plug gap is adjusted down. I would agree however, that running teenie plug gaps isn't the perfect solution, but it is by far the best solution in terms of affordability.