vinnie12345

Last year did the ECS, meth & LT's on a 15 C7(M)Z51 all done put down 690hp/606tq on 11.1lbs of boost on 91 octane.(80* temps outside). loved it so happy with it, wouldn't change a thing.
Now fast forward to last week; was feeling a bit off and went through every thing and found meth leaking. Changed out all fittings and no more leaks. Put it back on the dyno only 580. Found some debris clogging the meth nozzle. Cleared that and did another run same tune, everything same as last year except temp outside,it was about 100*'s. Now only 640/580 at 10lbs...????? What could the culprit be? Weather make that much difference? Love some advise!
Thanks

FYREANT

weather makes a big difference. 10 degrees is a big deal when dealing with timing. 100 degrees ambient is likely high enough to start pulling timing. If you are only hitting 10 PSI though, you may have a leak somewhere if you usually hit 11+. Perhaps check your fittings..

vinnie12345

Thank you for the input - I'll definitely check for leaks..

Could a dirty air filer opposed to a brand new one(the first tune had a new one put in) make the 1lb of boost difference? Is 1lb of boost = the missing 50hp?

NmtMev

This might sound a little silly, but reset your ecu as well. That might help. Just unplug overnight. It's free and easy to do. It won't hurt anything. You never know.

NmtMev

unless you've been out off roading in the desert and that airfilter is caked, then no. If it looks dirty change it anyways, they are cheap and reset the ecu like I said in my above post.

FYREANT

Could a dirty air filter account for a 1 psi restriction, if its really dirty yea. But, to clarify 1 psi is NOT 50 hp. More like 30.

DOUG @ ECS

You can clean the filter with soap and water, but if it's shot PM and we can one out to you. Like we discussed on the phone, the difference in 20* temps on dyno pulls from 80* to 100* is big. Much different then 60* to 80*. Especially if the car was heat soaked this time and not last time.
I can easily get a 20+ RWHP difference from just an afternoon pull after street driving compared to leaving it on the dyno overnight and making a pull even if the temps are the same.
Also make sure your throttle is staying completely open during the pulls.

Hope that helps.

vinnie12345

So here is the plan;
Check for leaks, check the air filter, and re Dyno in a couple months when it's cooler and see where we are then.
Thank you very much for the suggestions, I will follow up with results after the re-dyno... have a great weekend!!

DOUG @ ECS

For an example I just finished a C7 this morning that made 656 yesterday after street tuning and driving for a few hours, compared to 674 today after just letting it warm up and made a pull. Outside air temps were near identical.
I will put a post up on that car when I get a minute because we did some back to back testing of the stock intake to a sheet metal intake.

robert miller

Doug would like to see the diff on those intake's.

officermartinez

The scenarios listed above are spot on! But, I'd like to even offer another possible means for a small loss in power. Belt slippage or improper belt tension. A belt that is wearing out or improper tension will often times prevent the blower from reaching its full potential. In my case, after a quick belt swap, that meant an almost 2 pound increase in boost on my setup.. went from 19.x to 21.x on boost numbers.

Patriot Six

As the belt ages it will stretch. Had this problem on my C6Z. Ended up going direct drive. Problem solved.

BrunoTheMellow

tensioners should take care of stretch.

Patriot Six

I was maxing out the blower so I would need to periodically adjust the tensioner to avoid slip. I avoided this with the direct drive and picked up two pounds of boost compared to when the original set up showed no belt slip with a new belt.

vinnie12345

Didn't think about that! Thanks for the idea!!