How many pulls did you make on the dyno? If it was just 1 I can see why it would be low... LS1's tend to make better power on the 2nd and 3rd runs. You might have seen 310-315rwhp and 325ish rwtq.

 

made 2 runs...1st run: 300.5 power 315.5 torque 2nd run: 302.5 power 317.9 torque

 

Your new 18" rims and tires look nice, but I'd bet they are way heavier than stock... That will hurt your acceleration, braking, handling, and oh yeah... your dyno numbers too.

If you've got an open track nearby, make one pass with your stock wheels and tires, and another pass with your 18" wheels. I wouldn't be shocked to see a 2mph difference in the trap speeds (given similar passes). If so, then that's where your 20 rwhp is missing.

 

didn't think of that...but they wern't that much heavier than factory, and 20hps gone because of that...i dunno...i think i'm gonna take one off this weekend and weigh it just to see...

 

Your numbers are definitely low. LT headers are known to make your car run pig rich. You didn't say what your AFR is, but I venture to say you are on a rich side, which will rob of your HP/TQ.

If you need to correct the AFR, either get it dyno tuned, or use LS1 Edit, or Predator, or ATAP it and use MAF translator to get it corrected.

Also, don't mess with MAF, as an ex-LS1 engine moderator of couple of LSx sites, I have seen people with more problems than gains from using after-market MAF.

 

Wheels are always within a couple of pounds of each other, but those couple of pounds extra correlates into around 20lbs of roating mass per wheel. Because the wheels are what the engine actually turns, a slight increase in weight of the wheels has more of an impact than you think.

Don't know if I exactly said that right. I'm sure someone knows what I'm talking about.

 

Im also sure your putting down more power then that...btw beautiful car

 

First I have to say "Stock Z28 low"??? wtf is that about?? Mines stock.. 320/337 with 101 intake temp..

You simply cannot compare dyno to dyno.. regardless of name brand. Your best bet, is do a dynoday locally (you can organize it yourself if you really want to) and then compare with others on the same dyno on the same day..

One person may run their dyno better and may keep it in better shape..

Dont worry about what numbers you THOUGHT your car would put out.. Without a baseline pull beforehand, those numbers mean jack squat about your mods.. they just mean that on that particular dyno on that particular day with the settings put into the system, you car produced those numbers.

For dyno days, you can call up local shops with dynos and then see if they are interested in doing 2-3 runs for $35-$45 on a Saturday btw. x and xpm.. Promise to get at least 15 cars and its all good.. then get a date and promote it amoung your local car groups..

Good luck.

 

Agreed... my "slower, less powerful" '98 put down 316/326 bone stock barely broken in. I'd say it's a tuning issue or maybe a bad wire somewhere in the mix. Did you happen to run an a/f ratio test? not sure about those trailer dynos either. I'd take it to a shop to get some better information. Are you also positive it wasn't a mustang dyno? If that's the case the numbers look pretty good.

 

no it wasn't a mustang dyno...and that's what i was thinking bout the a/f cause i had an SES light on for O2 sensors so i thought maybe it was running lean cause of my GMAF and that was throwing a code but now the light went off yesterday and hasn't come back on yet...so i have no idea!!!

 

I am still running stock tune right now. Fixing to buy HP Tuner.

 

Definately change the fuel filter. These filters have been known to start clogging at early miles.