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Question about why a cammed car acts the way it does

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Old 02-17-2006, 08:36 AM
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Default Question about why a cammed car acts the way it does

I have a very mild cam, the old standby called "TR224 on a 112 LSA". My car has been tuned by a local shop, but all he did was full throttle dyno tuning, no driveablity tuning.

When I start the car for the first time, it smells very rich, I mean you can smell the gasoline while it's ideling. It also is a bit difficult to drive when it's still cold. Usually I let it idle for a minute or two to get a bit of temperature into it. When I start driving, I don't exceed 2k rpm's until the car is up to operating temperature, and if I am not careful in how I let the clutch out, it bucks, sometimes even dies. It does a bit of surging too while it's still cold.

Why do cammed cars do that? Should a car with a cam as common and small as mine act like that after it has been "properly" tuned?

I also noticed that when it first warms up, my exhaust shakes fairly violently, but once it's warmed up, the exhaust doesn't shake at all.

I also only put down the number that are in my sig....and they are STD not SAE! Pretty low, considering my mods, aren't they?

Thanks for any opinions and input. The reason I am asking this is because I am trying to decide if I should make the guy re-tune the car, or if I should spend another 500 for another initial tune and bring the car to Tampa at to RevXtreme.

Again, once it is warm, it runs just fine.

Manny
Old 02-17-2006, 08:53 AM
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Originally Posted by MannyZ28
I have a very mild cam, the old standby called "TR224 on a 112 LSA". My car has been tuned by a local shop, but all he did was full throttle dyno tuning, no driveablity tuning.

When I start the car for the first time, it smells very rich, I mean you can smell the gasoline while it's ideling. It also is a bit difficult to drive when it's still cold. Usually I let it idle for a minute or two to get a bit of temperature into it. When I start driving, I don't exceed 2k rpm's until the car is up to operating temperature, and if I am not careful in how I let the clutch out, it bucks, sometimes even dies. It does a bit of surging too while it's still cold.

Why do cammed cars do that? Should a car with a cam as common and small as mine act like that after it has been "properly" tuned?

I also noticed that when it first warms up, my exhaust shakes fairly violently, but once it's warmed up, the exhaust doesn't shake at all.

I also only put down the number that are in my sig....and they are STD not SAE! Pretty low, considering my mods, aren't they?

Thanks for any opinions and input. The reason I am asking this is because I am trying to decide if I should make the guy re-tune the car, or if I should spend another 500 for another initial tune and bring the car to Tampa at to RevXtreme.

Again, once it is warm, it runs just fine.

Manny
The reason it runs crappy when cold is because it is in open loop, going off of preset tables in the computer, it will always run rich in open loop. More so for a cammed car. The surging and bucking shouldnt happen, you need a full tune. Not just WOT tuning. Im not sure why it bucks and surges, but id guess it has to do with the overlap of the cam, and timing.
Old 02-17-2006, 08:54 AM
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For your dyno numbers, your wheels are holding you back. And I would also try a different dyno and swap to a stock MAF sensor, theres probably some left in the tune too. It sounds like the guys that tuned it didnt actually tune it.
Old 02-17-2006, 09:01 AM
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It's the stock MAF, they just made it a bit bigger.....I suppose you could call it a ported stock MAF.

I should put some donut spares on it for some nice numbers, hm? Hehe...

And yeah, I don't think he did much tuning either....didn't take but an hour or so, including cool down times between the 8 runs he made. It definitely wasn't worth the money!
Old 02-17-2006, 09:10 AM
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8 runs is about how much time you need to nail down the timing and AFR for WOT
but driveability tuning is a whole another ball game
go buy some tuning software and do it yourself...the basics are easy to pickup.
Old 02-17-2006, 09:14 AM
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your numbers are a little low. i put down like 375 or something with a 224 cam, headers, exhaust and a lid. you should be higher than I, with the xtra mods you have.
Old 02-17-2006, 09:16 AM
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Originally Posted by black_z
It sounds like the guys that tuned it didnt actually tune it.
Sounds like you flushed some money on botched tune.
Old 02-17-2006, 10:28 AM
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I think I am gonna spend some more money and take it to RevXtreme. What bugged me the most is that the car was initially tuned after headers and LS6 intake. It was then re-tuned for the cam, pulley, etc. about 4 months later. The re-tune charge was supposed to be 150, they charged me that times 1.5....so 150 x 1.5 = 225! Supposedely coz it was more work??
Old 02-17-2006, 10:40 AM
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When I start the car for the first time, it smells very rich, I mean you can smell the gasoline while it's ideling. It also is a bit difficult to drive when it's still cold. Usually I let it idle for a minute or two to get a bit of temperature into it. When I start driving, I don't exceed 2k rpm's until the car is up to operating temperature, and if I am not careful in how I let the clutch out, it bucks, sometimes even dies. It does a bit of surging too while it's still cold.

You need a good tune. Messing with the MAF and TB probably added to your tuning woes.



Why do cammed cars do that? Should a car with a cam as common and small as mine act like that after it has been "properly" tuned?
It acts like that because the cam has changed the airflow that the computer expects to see. Your "small" cam is still much bigger than stock in terms of overlap. At low rpms such as idle, your cam is much worse at filling the cylinders with air than the stock cam. Less air needs less fuel. Untill you tell the computer to add less fuel at low rpms, you will be running too rich.
Old 02-17-2006, 11:04 AM
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will drilling a small hole in the throttle body blade help that?
Old 02-17-2006, 11:09 AM
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I wouldnt drill the TB.
Old 02-17-2006, 11:53 AM
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Oh no...it idles fine, no need to drill anything as far as the blade is concerned. Basically I am looking for some inspiration to drive 100 miles to tampa and spend 500 bucks to see what's really in her.

Coz the other thing about the place that tuned my car was that the second tune, the one for the addition of the cam, took 3 appointements until I finally got in. First time I went there for my appointment, but noone was there...."emergency" according to the neighbors. Second time I had to cancel, and on the 3rd time, I actually called first before we left to go there and I was told that they need some time since their computer was not working. So I called back an hour later, and they said they had to have the computer fixed and they don't know how long it would take. Being that I am a computer tech, I asked what the problem was, and I right away diagnosed it and told the lady that all she had to do is take out the memory and put it back in, and the computer would have been fine again. So then I asked if I could bring my own computer down so we could get this done since I didn't want to take another day off work. So I load my computer up and bring it down there and hook it up....and yet, after all that they still charged me more! Oh yeah, just when we were done, the computer shop and told her exactly what I told the lady...she could have save herself that money.

So yes...that's another reason why I don't wanna go back there.
Old 02-17-2006, 12:04 PM
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Wow sounds like they are kinda shady...I say def go to rev extreme for a tune. You will have a slight change in regular driveability with your cam, but it should run like you say it does. My buddies 2002 z28 with a 228/228 cam had it tuned at east side performance and it idles like stock but has a nice little lope to it so you can tell its cammed. I say save up and drive to rev extreme and have them properly tune it. Good luck though!
Old 02-17-2006, 03:11 PM
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yea. goto RevX. ive been there, and its a nice shop with good people
Old 02-17-2006, 04:47 PM
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Isn't the initial $500 cost of a tune related to purchasing the software license? I thought that was why subsequent tunes were about $150. If this is true you might be able to take your license to another shop and pay quite a bit less than another $500 "initial" fee. Of course both shops will have to be running the same tuning software.
Old 02-17-2006, 05:40 PM
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You obviously got one of those "half-***" tunes that have become popular lately.
Old 02-17-2006, 05:44 PM
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Buy tuner software and download somebody elses 224 tune as a starting place. then you can tune it yourself until your heart's content. Looks like you're fairly competent with the rest of your buildup. Don't be scared. HPtuners was the coolest thing I've bought for my car yet. It's like a video game you can really drive.
Old 02-17-2006, 08:26 PM
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Get hptuners its not as hard as it sounds.
Old 02-17-2006, 11:15 PM
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I may work with computers, but I don't own a laptop, and I really don't have the time to learn all this stuff. So between the cost of the software, a laptop, and the time it takes trying to not **** it up....and also not having a dyno available to see what she does after the tune, I'd rather take a trip to a tuner that knows what he's doing.

They used LS1 Edit to tune my car, I know HP Tuners is the more popular choice nowadays, but being that my car is a 98, is there any limitations as far as tuneability since 98's have a different computer?

Vortecfcar,

What did you mean by "looks like you're fairly competent with the rest of your buildup", do you mean I picked good parts, or did you actually think I did all that work myself? Coz, the only work I did myself was change out my headlights for halos, and my clear corner lense swap, and I messed up just a bit in both cases....lol

Thanks for all the input guys!!!
Old 02-18-2006, 10:25 AM
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you need a retune. after my cam install the car drove funky for awhile.
i went to speedinc a few times so they correct it and they did.
i drove my car for an 800 mile roadtrip last year and it drove flawless



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