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I took my 1980 Malibu for some dyno tuning today and found that no spring in the wastegate = 10 to 13 lbs of boost, WTH. On the first power pull it was apparent the engine was making more boost that the 7lb spring. Opened up the wastegate and found a crimped diaphragm so we took the spring out thinking we would just tune what we could at little or no boost only to find out this thing would go much higher. One pull to 6,000rmp would make 13lbs and the next 10. I thought no spring meant no boost. Any ideas, is this a high back pressure situation? I used 2" tube for the crossover pipe to promote quick spooling characteristics.
The best pull of the day was only 440rwp at 6000 and 13lbs of boost using the sloppy base tune for timing and AFR. Power seamed to be falling off over 6000 rpm and we didn't want to push anymore with the boost out of control. Could the low power be cam related, I installed it dot to dot. Engine timing is verified. Valve springs are CompCam.
I'd recommend stabilizing boost and go through the tune first. But the cam could be off. It's been documented here where the crank keyway is offset up to 8*? on some cranks. Degreeing the cam in would be great insurance. But I'd check everything else off the list first, since it's a big job to do now. Car looks great!
It's been documented here where the crank keyway is offset up to 8*?
My timing was off 3.5 deg but that has to do with the placement of the reluctor wheel on the crank, right? This was corrected using the tuner studio software.
Can't wrap my head around why guys spend days, weeks, months or whatever assembling/fabbing and turbo system, doing an engine swap, etc and dont take 30 minutes to degree a camshaft.
Can't wrap my head around why guys spend days, weeks, months or whatever assembling/fabbing and turbo system, doing an engine swap, etc and dont take 30 minutes to degree a camshaft.
A lot of folks don't know how or are intimidated by learning.
it's a must-do with mix n matching factory and aftermarket parts
I agree a compression test would be a good idea. My wastegate is located on the exhaust turbine housing, isn't that a good place for it?
Its 90* to the flow how you have it. If the gate was vertical instead of horizontal it would work better. That way the exhaust can go straight instead of trying to turn at warp speed.
My timing was off 3.5 deg but that has to do with the placement of the reluctor wheel on the crank, right? This was corrected using the tuner studio software.
That's ignition timing variance. The keyway problem effects camshaft position in relation to crankshaft position. So the camshaft events may be occurring early or late causing your power loss.
Its 90* to the flow how you have it. If the gate was vertical instead of horizontal it would work better. That way the exhaust can go straight instead of trying to turn at warp speed.
My turbo flange is not straight up, more like 45 degrees so my wastegate flange is not at a 90 degree angle to the flow. It looks like a 45 to 60 angle. I realize this is not the best though. Should I think about adding another wastegate or see about a bigger one?
When I pulled all of the plugs for the compression check I noticed they all looked about the same except one had a slight tan ring on the insulator. Does that indicate anything wrong? It wasn't like there was a major difference on any one plug as far as sooth or carbon.
I need some help figuring out what my next step should be to solving the low power issue. Since all of the plugs look about the same wouldn't that indicate there is probably not an issue with any one cylinder? They should all be getting equal spark and fuel. The compression check went well. Am I dealing with a camshaft or valve train issue. Here is a look at the dyno curve and the HP is starting to fall off around 5650 rpm. The boost went to 13lbs on this run.
I am using Demah's MS3 tune from his 05 Colorado when he had the same 78/75 turbo and JFR 218 cam. I believe he was making almost 600 HP at 10 psi with this tune.
07-02-2017, 01:00 AM
