I took my Z to Z1 Motorsports this afternoon for my TopSpeed header install and got 3 dyno pulls prior to adding the headers. The mods I had at the time of these pulls are:

plenum
test pipes
popcharger
Injen dual exhaust
grounding kit

My best numers were 226.47 HP and 223.73 ft/lbs. To me, this is worse than stock. Am I assuming correctly??

Also, the 5AT is to be run in 4th gear correct??

With that being said, here is my problem. When the car was put into 4th gear and then stomped, the RPMs would climb noticably until around ~3600 RPMs and the like hesitate. They would then climb again until around 4800 RPMs and then hesitate again. Has anyone experienced this? Does anyone know what this may be or what could be causing this? One of the guys @ Z1 said it could be bad plugs or the plugs could be gapped incorrectly. What do you guys think?

The attached image is the dyno run.

Thanks for any info,
Zach

 

Tomorrow night I will post another dyno sheet which is after the header install.

 

I don't think I have ever seen a dyno sheet with "loops" in the power curve. That's really weird. I am familiar with the dynojet, but I have a MT and do my dynoes in 5th gear. As far as your baseline, I think that might be on par with autos. My completely stock dyno was 235rwhp and I cant remember my torque number.

 

yeah what the hell is that loop? Crayon drawing of dyno? Your ecu is still adjusting for the increasing exhaust flow. You will not be able to get the full affect from the headers for about 2 weeks. Your A/F looks good after 3500 rpm. Make sure you don't have any exhuast leaks either.

another edit: Test pipes are really not the greatest thing for a N/A car, maybe putting back the catalic converters will have a better effect.

 

Different dynos give different numbers even for a stock Z, so its hard to say. Although there have been variances of up to 30hp between dyno machines on the same car, I have been looking at the dyno results in this and another forum, and most stock MT Zs come in at an average of 235hp. Assuming a 17% drivetrain loss, that comes close to the rated 287hp. AT have a higher drivetrain loss, probably closer to 20%, so that 235 may be a bit high.

With all your mods, 226.47 seems awful low, but if you do not have a dyno of your car stock on that same machine, it is hard to tell. Once you do additional mods and dyno on that same machine, changes should be accurate.

However, if I were you, I'd go try someone else's dyno just for the heck of it. I mean, if you are going to dyno a car repeatedly on the same machine after every mod, might as well do it on one that doesnt give depressing numbers like that...

 

A lot of autos are pulling LOTS of timing out when dyno'd in 4th gear...

Sounds like yours is doing the same. Time for a reflash.

 

Join the club. My z made no net gains on a dynojet with the mods i have. Its a mystery. You never baselined yours before adding your mods? Maybe you could post a thread like "have your mods yielded no gains or a loss?" And we can try to figure out why this is happening.

 

No I never did a baseline dyno. Z1 just moved to their new location, so I have not even had the opportunity to do a dyno run with them before. I have read from a few members that their dyno gives very low results.

As I stated earlier, this dyno was with the 5 mods I listed and I will be dynoing this afternoon after the header install. I will also post results.

The reason for the crayon looking lines is because my scanner is a POS and you couldnt see the TQ and HP curves. So I just took a pen and outlined them.

 

Yeah, but does that explain the hesitation that I am experiencing throughout several locations in the powerband???

 

every time I dyno with my AT5 , I get a slight hesitation in the rpms on my tack around 3,600 rpm . But it doesnt show up on the chart . I dyno on a Mustang dyno and do it in 3rd gear . We have tried several times to dyno in 4th .And just like the operator said...I lost a couple hp .

 

Don't know about the hiccup in the rpms, but I wouldn't trust a dyno chart where hp and tq don't cross at least close to 5250 rpms.

 

Could it be possible the torque converter "loses its bite" during those hesitations?

 

Why is that?

 

because they are supposed to on every car!

As for your numbers, the dips most likely are knock

As for your plugs, if they are stock, I doubt highly thats the answer...seems the reflash should be the next thing you look into

 

The equation for horsepower is;

horsepower = torque x rpms / 5250

When you make a graph of this equation like a dyno, horsepower and torque will always cross at 5250 rpms. Its not always perfect in real life, but it should be pretty close.

Your dyno crosses at 4750 rpms. That is 500 rpms below where it should be. Almost 10 percent off. My guess is that your dyno power is 8-10 percent higher than shown. So that would put you up around 248 or so. Dyno's can only be compared in relation to each other on the same car, on the same machine, under similar environmental conditions for this very reason. You may have picked up plenty of hp with those mods, but without a baseline you may never know.

Does it feel faster??

 

zach, find out the size of the bolts needed for the headers, pls.
Btw, weight of topspeed headers=6.5lb ea.

 

It does seem faster while just driving around. However, it is actually slower on the dragstrip. I ran about a half second slower after I installed the plenum and exhaust.

 

Here's my advice. Go find a totaly stock Z and run him from a roll in a few different gears. See what the outcome is. Preferably another auto. Our cars suck at the 1/4 mile because of traction. If you add power, traction problems are even worse.

 

if you look at the graph the reason why it does not cross at 5250 is because the scale is screwed up on that thing... on the torque side its starts at 125 and goes to 250....on the horsepower side it starts at 50 and goes to 250....get them to scale it so that they are the same

edit: how do you like the headers, i recieved mine the other day and will be installed soon...how do they sound any different also how much of a difference could you feel?

 

Yep, good eye.