KR issues at mid throttle, TC locked; New Scans 4-7 - Page 6 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 02-07-2006, 10:11 PM   #51
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Another opinion from a good wrench who read this topic (sent to me via email):

Quote:
..........By the way, I saw your comments about EGR and it is absolutely on the money. The old style systems, way back, were pretty poorly controlled, and did cause problems, but the modern system is seamless in operation and actually helps as you said. I have an old Saturn winter car (144k miles), and the EGR solenoid malfunctioned. The car was very difficult to drive from a stop and at city cruise speeds (too much EGR). I plugged the vacuum line to make the car driveable until I could get the new solenoid. Mileage dropped from 33 down to 28 mpg and I was running scans at the time also to diagnose the problem and I would see 7-9 degrees of retard at highway cruise speed (light load). I make a 70 mile round trip commute for work every day, so I have a pretty good handle on the average mileage. It never varied more than 1-2mpg overall until the EGR was deactivated. When I installed the new solenoid, the mileage is back in the
32-33 mpg range. Thanks again for the help.
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Old 02-07-2006, 10:16 PM   #52
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Noted. I'll probably be reinstalling the EGR when I have a chance.

Bill, do you have any thoughts on the cam degreeing issue?

Also, is it recommended to limit my driving with this much KR?
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Old 02-07-2006, 10:57 PM   #53
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IMHO some knock retard is tolerable if it is only under light load. It would be better to get rid of it, but at light throttle, cylinder filling is relatively low, so pressures are not terribly high. I see the same sort of problem with my turbo conversion and it is something that will have to be tuned out. The best would be to try to stay out of the area where the major retard occurs, stay out of lockup until you get to a higher speed, or stay in a lower gear to get up to a speed where it doesn't occur. My chip was changed to eliminate lockup below 55 mph and it has helped, but is a temporary bandaid. I do have EGR but is probably tuned incorrectly for the new engine running parameters.
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Old 02-07-2006, 11:47 PM   #54
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Quote:
That article is an interesting read. We did no kind of degreeing, but the cam can't be that far off because the car actually runs, lol. All our Desktop Dyno projections show my cam profile making power up high with retarded timing and power down low with timing advance. We think the cam must be retarded a little bit because the street performance reflects a sluggish bottom end and plenty of power up at the top.
First, like Willwren and others have said; you should re-install the EGR system. On my 1995 SSEi, it did make a big difference after I replaced it.

Second, the cam, when installed, was aligned to the OEM timing markings, therefore, it is going to start and run. What I am talking here is about the timing events that are dictated by the camshaft lobe design and the centerline that was ground at. This is something that you can only figure out by degreeing the cam.

By the way, the Desktop Dyno is just a guideline and not a real time prediction tool and it is way off from actual numbers and performance. Believe me, I have seen and tried every engine/prediction program in the market since the mid-1980'* and compared them to actual track numbers and dyno results. There are only two programs that come close to actuals.

A camshaft with too much duration, or too advanced centerline, will build too much cylinder pressure, cause knock with pump gas and also be lazy, with no bottom end since it moves the powerband to a higher RPM band/level. To take full advantage of a cam with big duration, or advanced centerline, you need either, or both, a looser/high stall torque converter and deep gears to match the powerband.
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Old 02-08-2006, 02:41 AM   #55
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Quote:
Originally Posted by ssei1995
A camshaft with too much duration, or too advanced centerline, will build too much cylinder pressure, cause knock with pump gas and also be lazy, with no bottom end since it moves the powerband to a higher RPM band/level. To take full advantage of a cam with big duration, or advanced centerline, you need either, or both, a looser/high stall torque converter and deep gears to match the powerband.
Well, you're actually describing something similar to the current setup of this car. It doesn't have much on the bottom, but once you get into the mid/high revs it takes off like crazy. I definitely need a higher stall TC, but I'm way too poor for it right now.

So are you thinking that this knock will still be a problem even when the EGR goes back on? I know I can get ZZP to pull timing from the PCM which will solve the problem, but I assume you would like to see us properly degree the cam sometime?

This cam doesn't have big duration, but the centerline might be advanced too much. Do you think any trouble will come of this if we don't touch the cam for a while?

95naSTA: Did you degree your cam when you installed it?
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Old 02-08-2006, 10:28 AM   #56
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Quote:
Originally Posted by big_news_1
95naSTA: Did you degree your cam when you installed it?
No I did not nor has anyone on the boards IIRC.
But I think what ssei1995 is trying to say is when they reground your cam, the centerline may not be where it was stock. So, you may have wanted to degree your cam to get it exactly back to where it was stock. You can't really do this without buying an expensive timing set and I know at this point I wouldn't do it.
I'm still pretty convinced that if you get your egr hooked up agian, your light load KR will go away.
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Old 02-08-2006, 02:14 PM   #57
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Lol, the problem is now he'* got me all bothered that car might not be living up to its potential! Oh well. At least it runs!

I'm planning to hook up the EGR and tap/plug the coolant holes in the LIM. This should make the UIM just as reliable in the long run. Does plugging the coolant holes have any adverse effects on coolant flow throughout the rest of the motor? It seems that blocking a 'loop' such as the one through the UIM and TB would keep coolant from continuing to wherever it goes after the 'loop.' Is there some kind of bypass coolant passage before the LIM?
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Old 02-08-2006, 02:28 PM   #58
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95naSTA wrote:
Quote:
But I think what ssei1995 is trying to say is when they reground your cam, the centerline may not be where it was stock.
95naSTA is correct; there is a big difference when the camshaft is ground from a core by a company like Crane, Comp, etc... Using a core allows for more precision during the manufacturing of the cam, specially on the base, lobe shape and centerline. On a regorund cam, you are at the mercy of any variations or deviations when the cam was initially ground, specially more on OEM cams that are mass produced. New high performance and racing cams that are ground from cores, have more controlled processes since they are not manufactured in mass quantities; and also the reason why the vendors have to charge the prices they do for the new cams they sell from either Comp, or Crow cams in Australia for our cars.

Also, as 95SNASTA said, do the EGR first and then go from there.

big_news_1(Bill); I never intended to ruffle your feathers and get you worried. I am just trying to help determine the source and looking at possible root causes for the KR you are experiencing.
If you recall, when you started the project, I explained to you everything about camshafts and the Pro'* and Con'* of regrounds. I also understand that you were trying to make it a low budget project too. In addition, that was the reason why I had asked you at the time if you had done the camshaft timing check for the cam events. I have been in this road before too. Many years ago, I installed a racing cam on an engine that I was refreshing for a friend in a hurry, by matching the OEM markings in the timing gears. The car ran 3 tenths slower and I was using the same grind as before; After the race, I checked the timing events of the cam and it was way off; I fixed it and the car picked up an additional tenth (+ 4 tenths).
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Old 02-08-2006, 02:48 PM   #59
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Quote:
Originally Posted by big_news_1
I'm planning to hook up the EGR and tap/plug the coolant holes in the LIM. This should make the UIM just as reliable in the long run. Does plugging the coolant holes have any adverse effects on coolant flow throughout the rest of the motor? It seems that blocking a 'loop' such as the one through the UIM and TB would keep coolant from continuing to wherever it goes after the 'loop.' Is there some kind of bypass coolant passage before the LIM?
My HVII, in effect, does the same thing as drilling at tapping the LIM and I have no trouble keeping my car cool during the summer. Others on cgp have drilled and tapped the LIM without problems IIRC.
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Old 02-08-2006, 04:23 PM   #60
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Quote:
Originally Posted by ssei1995
The car ran 3 tenths slower and I was using the same grind as before; After the race, I checked the timing events of the cam and it was way off; I fixed it and the car picked up an additional tenth (+ 4 tenths).
See! Now I want to get in there and degree that sucker! Doug'* dad might even have the tools to do a degreeing job. I want my horsepower, torque, and 1/4 mile times!


Quote:
Originally Posted by ssei1995
big_news_1(Bill); I never intended to ruffle your feathers and get you worried. I am just trying to help determine the source and looking at possible root causes for the KR you are experiencing.
Not sure if you were calling me Bill, but my name is Ben. No worries though

I realize you're only trying to help, and even though I haven't always followed your advice I appreciate hearing it. I'm probably a fool for not always listening, but I guess I'm learning the hard way . Thanks for taking the time to help me out!
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