Re-stalled my Circle D converter. - RESULTS ARE IN!
12-26-2013, 08:55 PM
#1
Re-stalled my Circle D converter. - RESULTS ARE IN! So, after a few years with my Circle D 2B (2800-3000), I had it re-stalled to a 4C (3600-3800). I also had the transmission freshened up and upgraded to a Stage 2 while it was out. I drove it a little Christmas Eve and all day today.
The first thing I noticed is that it does not pull the engine down hardly at all when I put it in gear. The old converter would pull it down about 250 RPM. The new converter maybe 100 RPM.
At very light throttle, it behaves about the same. At moderate throttle the RPMs come up about 500 RPM more. At a moderate to strong part throttle the car pretty much sits at 3500 RPM as it goes through the gears now. At more aggressive part throttle the car feels quite different.
At full throttle the car is much stronger in 2nd gear. It actually feels like it pulls harder in 2nd than in first. It was the opposite with the 2B converter. The shift extension with the 2B were about 1800 RPM. Now they look to be about 800-1000 RPM. The car really stays in the powerband and it sounds ferocious. It jumps up on the cam fast and hard and stays there.
I am curious to see how it runs at the track now. I expect it to be quicker on the motor. I hope it does not lose any MPH and I hope it still runs as hard on the nitrous. Time will tell.
The first thing I noticed is that it does not pull the engine down hardly at all when I put it in gear. The old converter would pull it down about 250 RPM. The new converter maybe 100 RPM.
At very light throttle, it behaves about the same. At moderate throttle the RPMs come up about 500 RPM more. At a moderate to strong part throttle the car pretty much sits at 3500 RPM as it goes through the gears now. At more aggressive part throttle the car feels quite different.
At full throttle the car is much stronger in 2nd gear. It actually feels like it pulls harder in 2nd than in first. It was the opposite with the 2B converter. The shift extension with the 2B were about 1800 RPM. Now they look to be about 800-1000 RPM. The car really stays in the powerband and it sounds ferocious. It jumps up on the cam fast and hard and stays there.
I am curious to see how it runs at the track now. I expect it to be quicker on the motor. I hope it does not lose any MPH and I hope it still runs as hard on the nitrous. Time will tell.
Last edited by speedtigger; 01-18-2014 at 05:20 PM.
12-26-2013, 09:42 PM
#3
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Should 60' a bit better, maybe keep the same MPH but faster ET... or... since it stays in the powerband longer you may get the best of both worlds. Should be nice 
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01-08-2014, 09:51 PM
#8
Went to the local 1/8 mile track tonight. It is pretty much like racing on an unprepped street, so I never got a really clean pass. But, even lightly pedalling the car it still ran a new best on the motor. I am guessing when I get down to Bradenton Motorsports Park that the 60' times will be in the 1.5s on the motor and be about 2 full tenths quicker N/A. And I am really curious to see how it handle the nitrous.
01-18-2014, 04:59 PM
#12
The results are in! The results are in! About two full tenths quicker on the motor and the MPH stayed the same. On the nitrous, it ran a near identical time, but my bottle pressure was lower than normal after the pass, so the jury is out on that one until some more testing.
The cool part is we have a pretty close to apples to apples comparison. The D/A and wind was near identical to my old fastest time with the old converter.
Here is my old best on the motor with the old Cirlce D 2B converter:
Here is the new best on the motor with the new Circle D 4C. As you can see, the car is incredibly consistent for the street cruiser with the new converter.
Here is my old best on nitrous with the old Circle D 2B converter:
Here is my new best on nitrous with the new Circle D 4C converter:
As you can see, the nitrous passes are virtually identical. However, I was struggling with bottle pressure today. So, I will need more testing on nitrous before I will draw any conclusions there.
The cool part is we have a pretty close to apples to apples comparison. The D/A and wind was near identical to my old fastest time with the old converter.
Here is my old best on the motor with the old Cirlce D 2B converter:
Here is the new best on the motor with the new Circle D 4C. As you can see, the car is incredibly consistent for the street cruiser with the new converter.
Here is my old best on nitrous with the old Circle D 2B converter:
Here is my new best on nitrous with the new Circle D 4C converter:
As you can see, the nitrous passes are virtually identical. However, I was struggling with bottle pressure today. So, I will need more testing on nitrous before I will draw any conclusions there.
02-18-2014, 04:01 PM
#14
Well, I went back out this weekend and was able to maintain consistent bottle pressure and the car went a 10.16 @ 132 on a 73n jet in much warmer weather than last trip. So, the issue last time was definitely bottle pressure. The converter is doing a fine job handling the nitrous.
In fact, I upped the nitrous jet to an 81n tune and it continues to respond to the tune of 10.04 @ 133. Not bad for a SBE full weight street car at #3780. Here is a motor pass and a nitrous pass with the new Circle D 4C converter:
On the motor:
On the nitrous:
02-19-2014, 05:36 PM
#18
Thanx Chris. The D/A will help me get my N/A 10 second pass for sure. I will have my 9 second pass with or without great D/A. I can see with my testing, that this converter can handle more jet. So I can just jet up if I have to for the 9 second pass. 
Either way, props for nailing the converter. I told you I wanted a converter that could deliver a 10 second N/A pass and a 9 second nitrous pass. You have delivered. The reset is up to me.
Either way, props for nailing the converter. I told you I wanted a converter that could deliver a 10 second N/A pass and a 9 second nitrous pass. You have delivered. The reset is up to me.
