BatmobileLT4

Hey all, I wanted to get some input from those who have done it (preferably on OBD2 cars just to be relate able) but what have been your results (if any or if possible) in terms of having a tuned ECU and having to do smog/emissions in states like California? Reason being, upon completion I know the car will need to have a tune done to make sure everything runs right. On top of previous bolts ons that are legal in CA (except the SLP Cold Air Intake), I have added LT4 Hotcam and had my stock heads and manifold ported/polished, and LT4 Extreme Duty Timing Chain in terms of major internal performance engine upgrades. Im aware that PCMForLess, TPIS, and Hawk Motor Sports will tune LT1/LT4 cars. I just talked to Kyle of Hawk Motor sports and he told me that they would provide me the best tune they can but cannot guarantee it will pass emissions. Tune for my car was quoted at $350 which is not bad at all and less than what I had expected. Im a bit worried because I need to do smog here in California and I want my car to get the most out of the mods Ive made but still pass emissions. Ive always kept up on basic maintenance and also have all my emissions equipment like stock cats and A.I.R. accessories. Before I call TPIS or PCMForLess I just want to see if its been done already with some of you who have had your ECU tuned. I had a feeling smog wouldn't be a guaranteed pass but I figured if everything is running correctly and at full power witha tune shouldn't I technically pass? California is a strange place but thats just my theory. My car is 1996 LT4 Corvette
Engine related mods upon completion: Bored to 355 from 350, LT4 Hotcam, Basic street/strip port and polish of stock LT4 heads and manifold, LT4 Extreme Duty Timing Chain, TB Coolant Bypass, Airfoil, MSD Coil, Borla Catback with X-pipe in place of resonator, Pacesetter Shorty Headers, SLP Cold Air Intake and cut lid with K&N for smog check, and Dewitts Dual Core radiator. Pretty mild build engine wise which is what I was going for. Regardless, Please share any experiences in terms of having a tuned ECU and having to pass smog. Bonus if you live here in Commiefornia. Thank you!

Kevova

The stock PCM can handle the "hot cam" without tuning. You have a long list of CARB numbers. If there is no ses light it should pass smog. SES light is supposed to illuminate with PCM determines exhaust won't meet emissions. Tuning will probably get a little more out of your combination.I would get a second PCM to tune and swap PCMs as required.

MatthewMiller

Are you required to do a tailpipe sniffer test where you live? If so, that will be the more challenging part. It's easy to get a car to pass the OBD2 scan for emissions compliance.

bob arrowsmith

what part of calif . do you live, im in socal and have hot cam, 1.5 lifters, 383. car was tuned and passed smog.

mtwoolford

my LT4 with a hotcam passed California smog with no problem with stock tune.

BatmobileLT4

I live in the bay area. They do the tailpipe sniffer here. I know from many that they have passed emissions with the hotcam but Im not sure if my mods will have any effect on making it harder to pass. Also most people mention that after the cam swap, their is some slight drive ability issues mainly in just the fact that it runs abit rich and also they obviously dont get the full benefit of the swap. At the least its driveable. Once i done Ill see how the car runs. If its driaveable Ill try to get another PCM or maybe just send mine in and have it tuned. I was thinking of going the other route and buying a PCM from an LT4 if I can find one and sending that in instead.

BatmobileLT4

Did you have any issues with driveability with the hotcam and stock tune? Did the car feel "weak" or maybe smell like unburned fuel?

mtwoolford

Yes I did notice drivability issues. The car went faster. A corsa exhaust and an LT4 Hot Cam are a match made in heaven. Judging by the plugs, the engine does run a bit richer with the Hot Cam. Is that a bad thing? I'd rather the engine be on the rich rather than the lean side. No gas fumes either.

looking at your mods, get the intake back to stock, not because it hurts the tailpipe test, but because it will flunk the visual. Make sure both cats are in good shape. run the hot water back through the throttle body, and replace the thermostat with a 180 degree (or 195 degree, if available) Tstat and pre test, take it out for a nice hard run and have it well warmed up for the tailpipe test. You should have no problem.

Also, erase any codes in the CPU memory; easy enough.

BatmobileLT4

It went faster haha good one. Im hoping the Borla with the x-pipe being thats its deeper and smooth in sound compared to the corsa wont "hide" the sound of the cam loping. The hotcam matched with the corsa sounds awesome from what Ive seen on video and I cant imagine it sounding any worse in person. I bought the car with the borla and Ive owned it for 2 years. Its been a money pit and not excatly in a bad way. I love it. All the bolt on mods listed, I have had prior to the engine rebuild. I did take the intake off for the visual and Ive passed with everything else. Im just abit worried this time around (like most of the time when it comes to upgrades here in Calif.) and would really like to tune my car to make sure everything runs at its best. Im no mechanic but I dont think a car running rich is good for its longevity. Personally, I just want the car to run almost perfect. Im thinking about going the secondary PCM route as recommended by Kevova but man they are kind of pricey and add that on top of the tune and possibly an LT4 Knocnk Moduel since it may or may not come with one and thats another 350. TPIS sells a PCM for 349 (not sure if compatible with my car though), tune from hawks 350, LT4 Knock Module another 350. Thats alot but once the car is done ill know what I need

mtwoolford

Well, the opposite, running lean, may work in low compression engines, but go lean in a performance engine and the pistons start melting. Most performance engines are tuned on the rich side as a safety factor. Personally, I'd drive the car with a stock tune and see if you like it before worrying about trying to fix problems that may not even be a problem. Everybody wants to maximize the performance on their engines, but reading dyno tests from back in the day, the LT4 with a Hot Cam and stock tune didn't leave much, if anything, on the table.

BatmobileLT4

I agree. For now Im just going to worry about finishing the car and seeing how it runs. Ive been making some calls to get some info and quotes but no one has been able to 100% assure me it can pass. It all comes down to how good is the tuner. I will post my thoughts once its done to help others even if there are older threads on the matter. Now I was thinking if I do go the route of a secondary PCM could I get one from a 1996 LT1 Corvette, change the knock module to an LT4 one, have my VIN files programmed into it and then tuned for the mods I have and expect it to work in my car?

fredk

When I did my car years ago I purchased most of my parts from TPIS. At that time they had a package they said that would even pass in California. Give them a call.

BatmobileLT4

I did call them yesterday, Jim from TPIS told me that he cant be sure because they dont do emissions in his area. They also dont have that package on thier webpage. unfortunately.

fredk

That was back in 2005 when I purchased my parts from them. Too bad they don't make it anymore.