Back from the dyno and disappointed

[Billy Mild]

I spoke with Marc yesterday about the situation I faced Sunday on the dyno.

He mentioned if the shop didn't use SAE correction that the increased heat will have a bigger hit on the dyno numbers. After that he mentioned if my engine was heatsoaked that could have as much as a 10-15 HP hit. Those two things would make up about a 17-20 WHP affect on my dyno numbers. He said that I may be able to get 3% more power if he removed some fuel, but most likely that would not increase power much.

So overall it looks like outside temps, and engine temps may have hindered performance a bit. I will most likely wait for later this year when it cools down and dyno again to see if that is the cause.

[Kevin]

All of that is true and Mark would know better then anyone, however if you have the stock duct you need to change it out. Worth every penny of whatever option you go with

[mike100]

The very first time I took my headers out for the maiden voyage/test drive- I didn't feel a lot of difference, but he next morning in 60 deg air I could really tell. The torque at mid-range shifting into the next gear was much improved too.

initially I just ran the stock exhaust for about a month with the headers. Once I put the SW 3" catback on, then you could really feel more top end- at least in my case.

I have since discovered my secondary fuel pump wasn't maintaining pressure past 5500 rpm, but these days I am back to the oem manifolds. It runs a bit better on the stock pipes with the new pump- I kind of can't wait to try the headers again.

[Billy Mild]

Attached is my best run SAE corrected and with RPM instead of Speed.

[XfireZ51]

Originally Posted by Billy Mild

Attached is my best run SAE corrected and with RPM instead of Speed.

???

[Billy Mild]

If anyone would want to look at the actual run file I can send that a long. Marc gave me some other suggestions such as maybe one of my secondaries is not opening all the way, could have a slight misfire as well. His test for misfiring is to go 40 MPH in 4th gear and go WOT. It should pull smoothly and clean.

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[mike100]

peak hp should be at 5900-6000 rpm and peak torque at 4800 rpm on the early 375hp engines.

[XfireZ51]

Here's an early stage mod dyno run on my car. Ported top end and headers.
As Mike points out, torque peak and hp peaks at higher rpms.
It makes me wonder if the cam timing may not need to be verified.

[Billy Mild]

Looks like you are running closer to 13:1 for the AFR. I'm in the 11.8:1 range

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[Paul Workman]

Originally Posted by Billy Mild

If anyone would want to look at the actual run file I can send that a long. Marc gave me some other suggestions such as maybe one of my secondaries is not opening all the way, could have a slight misfire as well. His test for misfiring is to go 40 MPH in 4th gear and go WOT. It should pull smoothly and clean.

Sent from my Nexus 6 using ZR-1 Net Registry mobile app

Yep. That ain't right!

Here is another set of dyno graphs, one w/ 2ndaries closed and then open (the porting specifications unknown). Notice where your torque is peaking compared both Dom's top-end porting graph, and the one from Lingenfelter.



You can see why Marc is wondering if the secondaries are opening properly. Although skewed somewhat toward FULL POWER, the graph stubbornly follows the primary characteristics. Cam phasing might be a small part of you graph, but it does look more like malfunctioning secondaries.

Again, Dom's top-end graph for comparison...

Originally Posted by XfireZ51

Yours should look more like Dominic's graph for a top-end/headers upgrade.