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XfireZ51 · 10-15-2011

Finally got opportunity to put car on dyno yesterday at Speed Inc.
It was somewhat disappointing for a couple of reasons. In its previous configuration on the same dyno, the motor pulled ~399rwhp with a peak of 6800rpm. With several successive pulls, we didn't get more than 414rwhp this time. The previous config. was ported top end, headers, full exhaust, and my tuning. Now the motor sports GVD heads, Pete's Intake regrinds, again full exhaust and previous top end porting.
As a caveat, don't take these numbers as etched in stone at this point. It took 9 pulls and 2 hours to get the AFR numbers near where they should be. Quite a bit of additional fuel was needed for this configuration. Myself and the dyno opertor had agreed that if we saw an AFR > 13.2, he would shut it down. So we did this and got to 7000rpm+ in stages. The AFR curve I now have is much better than what I came in with. In some cases, AFR was climbing towards 14:1. One GOOD reason not to run the car last Sunday before getting it on th dyno. The curve still needs a bit of tweaking but it needs to be right before I would play with timing. I did do some datalogging just to check for Spark Counts. With the timing tables I have there now, I only had 1 Spark Count near 6K and then very briefly. Timing was retarded by 1d for 1-2 frames. Not enough to be concerned.
Consulting w Pete, our thoughts are that:

1. The air bridge is likely collapsing. It continues to squirm off the air cleaner assembly regardless of how much I tighten the worm screw. Pete says that is a sign of the snorkel being pulled away by the suction of the motor. Although I have one of Marc H's "hoops" inside, the air bridge may be collapsing particularly at the housing end.

2. I may have discovered the limits of the MagnaFlow resonator. Up to this point, it didn't appear to be a bottleneck, but with the increased flow (the addtional fuel needed really suggests that) it may not be able to move the exhaust efficiently at this level of power.

Bottom line is I will try to get back to the dyno before the snow flies but first addressing the airbridge collapse and resonator restriction issue.
In the meantime, here's a vid of the car on the dyno yesterday.

I'll post dyno sheet one I get data file of it from Speed Inc.

BTW any suggestions on the exhaust issue are welcome. Right now I am trending towards removing the resonator and Xpipe combo and replacing with SW Xpipe and 2-3" straight pipes in its place. I'll worry about the drone later I guess.

10-15-2011	#1
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,686	Dyno Day Finally got opportunity to put car on dyno yesterday at Speed Inc. It was somewhat disappointing for a couple of reasons. In its previous configuration on the same dyno, the motor pulled ~399rwhp with a peak of 6800rpm. With several successive pulls, we didn't get more than 414rwhp this time. The previous config. was ported top end, headers, full exhaust, and my tuning. Now the motor sports GVD heads, Pete's Intake regrinds, again full exhaust and previous top end porting. As a caveat, don't take these numbers as etched in stone at this point. It took 9 pulls and 2 hours to get the AFR numbers near where they should be. Quite a bit of additional fuel was needed for this configuration. Myself and the dyno opertor had agreed that if we saw an AFR > 13.2, he would shut it down. So we did this and got to 7000rpm+ in stages. The AFR curve I now have is much better than what I came in with. In some cases, AFR was climbing towards 14:1. One GOOD reason not to run the car last Sunday before getting it on th dyno. The curve still needs a bit of tweaking but it needs to be right before I would play with timing. I did do some datalogging just to check for Spark Counts. With the timing tables I have there now, I only had 1 Spark Count near 6K and then very briefly. Timing was retarded by 1d for 1-2 frames. Not enough to be concerned. Consulting w Pete, our thoughts are that: 1. The air bridge is likely collapsing. It continues to squirm off the air cleaner assembly regardless of how much I tighten the worm screw. Pete says that is a sign of the snorkel being pulled away by the suction of the motor. Although I have one of Marc H's "hoops" inside, the air bridge may be collapsing particularly at the housing end. 2. I may have discovered the limits of the MagnaFlow resonator. Up to this point, it didn't appear to be a bottleneck, but with the increased flow (the addtional fuel needed really suggests that) it may not be able to move the exhaust efficiently at this level of power. Bottom line is I will try to get back to the dyno before the snow flies but first addressing the airbridge collapse and resonator restriction issue. In the meantime, here's a vid of the car on the dyno yesterday. I'll post dyno sheet one I get data file of it from Speed Inc. BTW any suggestions on the exhaust issue are welcome. Right now I am trending towards removing the resonator and Xpipe combo and replacing with SW Xpipe and 2-3" straight pipes in its place. I'll worry about the drone later I guess. Last edited by XfireZ51; 10-15-2011 at 04:13 PM.