jp0863
1/2 ton status
Between edelbrock and comp cams, which one is better for power and emissions? Being in California i have to have an emission compliant cam, and I don't know enough to know which one is better.
CK5
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TBI cams
- Thread starter jp0863
- Start date
I put a Comp Xtreme Energy 4x4 cam in about 10 yrs ago. Breathes way better and much more torque on the low end. Never burned a chip for it, but I did install an MSD 6A box to make sure I was burning all the fuel. Anyway, performance improved. Can't say much about emissions, we don't worry about such things down here in God's country. Sorry.
I wouldn't be surprised if Comp Cams grinds Eddy's bumpsticks.....
jp0863
1/2 ton status
Yeah wish I didn't have to deal with the smog nazi's.... Is this something I should take up with the Camshaft manufacturers?
CC's tech support is about the best you'll find for any product...
jp0863
1/2 ton status
Thanks, i'll give them a call
Why are you concerned with smog? Cam isn't something they will know about, tuned properly even decent cams can pass. It will just take more effort to figure out what that limit is.
There is nothing such as a "computer friendly" camshaft. While it will or can make more power, and pass emissions, under load is a different matter entirely. Depending on the cam, there will be power that you are missing. These injection setups are limited because they have no way to change timing or fueling (in a positive manner) for changes made to the motor. Even carbed GM had a bunch of different cams.
There is nothing such as a "computer friendly" camshaft. While it will or can make more power, and pass emissions, under load is a different matter entirely. Depending on the cam, there will be power that you are missing. These injection setups are limited because they have no way to change timing or fueling (in a positive manner) for changes made to the motor. Even carbed GM had a bunch of different cams.
WRONG. When you start installing a cam with a smaller lobe centerline angle that makes the engine vacuum start going down which now freaks out the ECM via the MAP sensor and all of a sudden you have an engine that won't run correctly.
That is the downfall of a MAP system. A MAP system calculates air flow into the engine while a MAF system reads actual air flow into the engine.
79bonanza
1/2 ton status
Just buy a cam for a 5.3 or 6.0 and save up till you can wrap the rest of the parts around it.
You install a camshaft to gain more power. You gain more power by burning more fuel.
Now, that being clarified, after a cam swap (or any other change that requires different fueling and/or timing, like better heads, better exhaust, etc) how exactly does an OBD1 (or any OBD2 system I'm aware of either) system add more fuel when you mash the pedal? How does the ECM adjust timing to better match the different cylinder filling and burn characteristics? In a worst case scenario, what is the ECM going to do about already low fuel pressure with an engine that now demands more?
Think about that a bit, you will see the fallacy of "computer friendly" camshafts.
First off, to gain more power doesn't neccesarily mean you'll burn more fuel. You need to optimize the system more effiecently and you'll produce more power.
The ECM reads all of the sensors on the engine to determine what the timing and fueling needs are. If you have added a larger cam and heads that exceeds the capacity of the factory injectors for instance then you are only capable of making the maximum amount of power that the fueling will allow with the now too small injectors. Now someone could burn/flash a new chip/PCM to correct fuel tables which could allow the factory injectors to work for your application given the demand for fuel isn't beyond the capability of the injectors or fuel table. Fuel requirements are monitored by the MAP sensor, TPS, 02 sensor(s), and even the knock sensor(s).
Mechanical efficiency (roller cams, roller rockers, less reciprocating mass, etc) is the only way gains can be made without adding fuel. Pretty hard to make much in the way of gains there on a SBC for most budgets. More air in always equals more fuel in.
In a given engine where you swapped a cam, because the PROM programming is for a "smaller" cam that needs less fuel, and O2 isn't accurate under heavy throttle WOT conditions (and cold starts) the engine is running lean, what now? The ECM can't "see" the lean condition, so how will it fix that?
Timing is based off a timing map, basically a spreadsheet of load vs. RPM. At X load and Y RPM, timing is Z. That was all based on the stock engine as an assembly...changing any one component can/will change the timing requirements, but the ECM is stuck working off the stock timing chart. It can't add, and will only subtract when the engine starts knocking, which is too late.
If you swap engine components, at BEST if you don't tune the PROM, or have someone do it, you are leaving power on the table. If your changes are significant enough, you will run lean enough to do real damage. Neither the best nor worst case is "computer friendly". You might be able to drive it, and it might feel good, but until it's been datalogged and optimized, it's not running as good as it should or could, and it may very well be dangerous.
In a given engine where you swapped a cam, because the PROM programming is for a "smaller" cam that needs less fuel, and O2 isn't accurate under heavy throttle WOT conditions (and cold starts) the engine is running lean, what now? The ECM can't "see" the lean condition, so how will it fix that?
Timing is based off a timing map, basically a spreadsheet of load vs. RPM. At X load and Y RPM, timing is Z. That was all based on the stock engine as an assembly...changing any one component can/will change the timing requirements, but the ECM is stuck working off the stock timing chart. It can't add, and will only subtract when the engine starts knocking, which is too late.
If you swap engine components, at BEST if you don't tune the PROM, or have someone do it, you are leaving power on the table. If your changes are significant enough, you will run lean enough to do real damage. Neither the best nor worst case is "computer friendly". You might be able to drive it, and it might feel good, but until it's been datalogged and optimized, it's not running as good as it should or could, and it may very well be dangerous.
Everything you're saying makes sense, but lemme run this by you...
For mine, which is a 'computer friendly' Comp, I figure with a batch-type FI system like the TBI a little bit more gas and fuel is getting in simply because the valve opens a little more and a little longer. If the TBI is squirting a fixed rate of fuel, a longer duration makes for a little more fuel in the cylinder, no? This is probably not true with a direct injection system unless the O2 sensor is telling it to get more fuel in.
I'm no expert, just tossing it out. I can tell you that my cam definitely made a difference. The bottom end power definitely improved (it's a torque cam), no rich burning (also added MSD), even the exhaust had a lot deeper tone. Like I said mine's been in for about 10 yrs so I don't think it's dangerously lean. Maybe I AM leaving power on the table. Hell, maybe I just got lucky.
For mine, which is a 'computer friendly' Comp, I figure with a batch-type FI system like the TBI a little bit more gas and fuel is getting in simply because the valve opens a little more and a little longer. If the TBI is squirting a fixed rate of fuel, a longer duration makes for a little more fuel in the cylinder, no? This is probably not true with a direct injection system unless the O2 sensor is telling it to get more fuel in.
I'm no expert, just tossing it out. I can tell you that my cam definitely made a difference. The bottom end power definitely improved (it's a torque cam), no rich burning (also added MSD), even the exhaust had a lot deeper tone. Like I said mine's been in for about 10 yrs so I don't think it's dangerously lean. Maybe I AM leaving power on the table. Hell, maybe I just got lucky.
That is the FIRST thing I said.
Then why argue that there is such thing as a computer friendly cam? There isn't, that is a fact. If you HAVE to tune it to get everything out of it, then it's not really friendly with the computer.
"Computer friendly", at best, is misleading.
The ECM can only inject the amount of fuel it is programmed to inject (outside of mechanical limits of course). The "on" time of the injector is how it changes the amount of fuel added to the motor. If the valve stays open longer (or opens earlier, or closes later, whatever) the only way more fuel is added is if more fuel is available. The PROM has to be programmed to get that extra fuel in.
On a batch system you are right, there is more fuel available per cylinder because it's "shared" amongst four cylinders...but if you are pulling more for each cylinder, eventually the engine will pull more fuel than is required to keep from running lean, unless the PROM is programmed to give what the engine needs.
I'm not saying they don't make a difference. But if you are going to need to tune something to get all the benefit out of it, why limit yourself to "computer friendly" grinds? You can feel a lot more power in an engine, and still be lean. I suspect these cams are mild enough and GM was conservative enough that there is perhaps an overlap on how much fuel is injected under heavy throttle, but there is no way to know for sure without hooking it up and looking at the data. If it was a serious issue in all uses, these cams would be gone.
I use my Dad's 454 as an example, because it's a very mild motor...Edelbrock performer intake, mild cam, and headers. Fueling was 20% off (lean) from stock, not only 20% on the VE tables, but had to crank the fuel pressure up as far as the TBI pump would go. That's dangerous if undiscovered. It ran fine, you couldn't feel it or tell it any other way. But towing a trailer over the mountains? Someone who likes the throttle?
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big dif between a cam being optimized for performance, and a cam who's centerline won't allow the ECM to even keep it running..
I suppose if someone wants to buy parts and is happy knowing that they are leaving performance on the table because the cam manufacturer didn't bother informing them that "friendly" doesn't mean what most assume it does, thats all well and good.
All I'm saying. At best, these "computer friendly" cams, are absorbing any margin of error built in by GM in regards to fueling and timing. At worst they are exceeding it, and the engine isn't running as well as it can.
You could throw a thousand different cams in the motor and it would run, regardless of "computer friendly" or not, it would just be much more obvious why injection needs tuning.
All I'm saying. At best, these "computer friendly" cams, are absorbing any margin of error built in by GM in regards to fueling and timing. At worst they are exceeding it, and the engine isn't running as well as it can.
You could throw a thousand different cams in the motor and it would run, regardless of "computer friendly" or not, it would just be much more obvious why injection needs tuning.
try throwing TBI on a thumping hotrod motor cam with a low centerline and see if it'll run.....
I didn't say run good, I said run...just because an engine runs, it doesn't mean it's running right, nor to it's full potential. "Feel" doesn't matter. When it's really wrong, you'll feel it. When it's a bit wrong, you'll think everything is ok. If the cam is too radical, it will run bad, if at all...but that is simply an exaggerated example of a motor needing tuning...it's a degree.
My Dad's motor ran "fine" needing 20% more fuel, he drove it like that for some time. I wouldn't call that computer friendly just because it ran with no tuning. He knew no different.
My Dad's motor ran "fine" needing 20% more fuel, he drove it like that for some time. I wouldn't call that computer friendly just because it ran with no tuning. He knew no different.
they generally wont even run if the cam is pretty nasty, throws the ECM/vac signal so out of whack.. I've had 2 customers do that stuff..
TBI motor blows, "oh I'll do it myself, I have a friend with a motor" "gee, it won't stay running, can you look at it?" and it's some lumpy arse hotrod motor that had a carb on it before.... change the mill to something with a cam that's "reasonable" in it's spec's and it runs.. optimized no, but will at least run.. that certainly covers the term "computer friendly" imo..
I understand what your arguing, I'm just saying that there are cam specs that wont allow EFI to run, thus the term "comp friendly" has a bit of merit... albeit a stretch and advertising jingo..
TBI motor blows, "oh I'll do it myself, I have a friend with a motor" "gee, it won't stay running, can you look at it?" and it's some lumpy arse hotrod motor that had a carb on it before.... change the mill to something with a cam that's "reasonable" in it's spec's and it runs.. optimized no, but will at least run.. that certainly covers the term "computer friendly" imo..
I understand what your arguing, I'm just saying that there are cam specs that wont allow EFI to run, thus the term "comp friendly" has a bit of merit... albeit a stretch and advertising jingo..
