Now this pup failed hydro carb w/2.70 allowed 1.7 everything else just perfect. Now ??? still had a touch of seafoam in it very little AND no way would they do the test in 4 th gear only looked like 1 st. has cam ,heads ,ported intake,ported 90m tb all this set up done with Tony Mamo so not junk and mid 480's rwhp on mustang dyno . Any thoughts, really heard a lot about this 4 th gear deal.
If you have your skip shift disabled it really screws them up.
The emissions computer knows what its testing and that your corvette is supposed to go from 1st into 4th, so it only tells them to do 1 upshift.
I had the same problem last year.
You may still have to much cam or mods to pass.
Hope this helps.
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ASE Certified L1 Master Automobile/ L2 Master Heavy Truck/ Master Truck Equipment Technician
Alternative Fuels Vehicle Specialist
Was the car nice and warmed up before you went? Sometimes that makes a huge difference, make sure it's been running for at least 15-20 minutes before getting there.
Do you have a lower temp thermostat? Have you lowered the fan turn on temp? I went back to a stock thermostat and some what lowered fan temps and it cut my hydrocarbons by half. I swear it ran better as well, and gained a mpg or two.
If you are running long tubes with aftermarket hi flow cats, they may not be getting hot enough to light off. This was my problem, and my car is an A4 with comparable setup. Required a retune and factory cats to get it legal. Dragon finally figured it out.
Have the themo lt. headers and cats starting to get in that range $$$$ so just just show how much and get exemption or just register that puppy some where else, already had to change ride height wheels and tires , changed oil,gas. Going to give it one last shot with cags. I have lot of problem after mods and tune and seeing significant increase mpg accepting the car is that dirty. Also do know that the test was tuff for tester to do in 2 nd gear maintaining correct speed. So will see, cam is not that nuts little overlap put in at 114 ,Tony said it should go in at 112 but could be close on emissions so go with 114. So who knows.
Change the thermostat and fans. I have LT with high flow cats, they did not effect it as much as the thermostat. I have a 228/232 lsa 114 cam and ported heads, even with a poor tune I was able to pass the hydro carbons.
I didn't have a problem with the 1st to 4th issue, not sure why as I have it turned off.
Talk about open pit found dyno sheets,Then found that, repeating I know that test was done with stock injectors. So when they showed up at + 90 % duty cycle @ WOT ,adjusting started . I was told numbers great but 90% be ok just don't drop to lower altitude HUH ! well can't live with that so back at shop they installed bigger injectors can't find exactly what size but larger injector now down to high 50's low 60's great what showed on dyno ? Oh didn't go back tune looks fine. IN parking lot?? HUH? so told Tony I got this back and I quote : " Someone would have had to rescale the injector table or it would be rich as hell!!! " in the parking lot ? No. So now quest goes on. So now the search for correct tuner.
Thanks for letting Vent ,Better word would "B" but don't need to be yelled at.
The first time took it to Dragon and they retuned it and brought it back and reinstalled tune. $$$
This last time, I took the old center section, adapted it to fit my headers, put that on and put a little denatured alchol(sp) in the gas tank and passed the E-test.
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