I see many people complaining about some surging or running rich at lower RPMs. Most run a cam with an LSA in the 108-112 range and/or duration in the >230s.

I don't understand how you want to run a medium to large size cam and expect to have stock-like driveability. I've spent countless hours tuning on the street and there is simply not much you can do past a certain point. You just can't have the best of both worlds. (although that doesn't mean that you can't find a good cam that will be somewhere in the middle of both)

Now as far as running rich. With an LSA tighter than stock, the car will run rich at lower RPMs due to overlap. Leaning it out will make the driveability issues worse and if you don't run cats and EXPECT your car to smell clean with a big cam, leaning out to such a point WILL reduce your engine's life.

In other words, if you are looking for a ton of power but want clean exhaust and smooth driveability, you'll probably be better off going forced induction and running cats on the car.

By making this post, I am not trying to cover up for lack of knowledge when it comes to tuning, but simply stating a few facts that everyone should think about before making a decision on which route to go with.

EDIT: Just to clarify and avoid misunderstanding, having posted this, I am not attacking or even intending of criticizing anyone. This post was made for discussion and informational purposes only.

 

Ion: you asked "why" and I think I know the answer. I blame the Internet and human nature. It's human nature to want to have it all and also to look good in front of your peers. So, you get people boasting on the 'net about all the hp they have, how drivable their car is with a big cam because of this or that, and so on. Because it's the 'net, they never have to actually produce the car and in some cases I'd bet it doesn't exist, let alone do everything they say it can.

EFI has changed things. While you can now run a more radical cam with EFI than you ever could with a carb, there is still such a thing as too much cam. Your points are well made and people ought to pay attention to them.

Rich

 

Couldn't you open this thread earlier? According to your post I should go with FI route,but I went with Heads/cam route,and its too late to change the route (charger) I always suppose "charger" has less drivability then "NA" .. Anyway its a great post though

 

There is really nothing about a SC or turbo that directly effects part throttle/light load drivability. That's one of the things that is attractive about them.

Rich

 

I was affraid of going with charger route because I don't know when,how, but I learned (maybe wrong) that with charger you have a bad gas milage and its not friendly with long trip. I think lots of people suppose that and for that reason they don't choose to go on this way.

 

and on top of that...they want it to be their daily driver because its the only car they can afford. .

 

You won't have such issues with a properly built motor, good selection of parts and good tuning. You need to invest to go fast and be reliable at the same time. There's really no cheap way around it.

Of course, some of the issues mentioned in the first post can also be caused by failing or over used parts such as o2 sensors or opti. That's why your main focus should be to make sure these things are working correctly, not taking your car to the track the 2nd day after your cam install.

I see too many people cutting into their o2 wires and extending them by adding more wire and crimping, people who port their MAF sensors, others who buy used internals and have no idea what they've been through before and install them without any inspection, or people who will buy a "custom" cam and have no idea what the specs are, but have been told that it's "big" and "it will work" because guy X ran 9s all day on it. And of course, the people who have never done any engine work before and put things together in a rush with a couple of friends and some beer in grandma's garage and expect things to work perfectly the first time you start up the car. Things don't quite always work that way. Some get away with it and the rest you see posting "I spun a bearing".

These are just bad decisions in my opinion. If you want a high performance engine, you need to give it quality components, otherwise, you'll find yourself replacing things all the time and not being able to figure out what the problem is.

 

...and with that, proper time to research intelligently. Too many folks rush into the 'gotta have it' mode, without being brutally honest with themselves with regard to the inevitable trade-offs or sacrifices that are inherent to any high performance engine.

 

wait a minute.....





I cant have a 24x/24x, .6XX/.6XX cam with no surge? Whats up with that? I mean c-mon. And I wont get 30mpg anymore. Dam.




I got the ecu Ion, Thankyou.

I never did think about the overlap causing the car running to run rich.

 

Oh I'm happy to heard that because I didn't escape to spend $$$ and built it with top notch quailty parts. Do it once and let your mind free..

 

Good point. Let's also not forget that different people have different "tolerances" when it comes to driving and how the car feels. Some will shake in the seat and smile, thinking "Wow, I can actually drive this car on the street with this cam" while others will bite their nails over some low rpm hesitation that may not even be cam/internals related. (opti most of the time)

Also, another reason why numerically higher gears are recommended for bigger cams is because these gears will move you over the surge area quicker, whereas if you have 2.73s and you installed a monster cam. (I just had someone stop by with an LS1, 2.73s, stock converter and G5X3 cam [read "big"], that surge effect will be signficantly more noticeable, not to mention that a stock converter and those low gears will keep you too long out of that cam's operating range to actually see a difference in track times.

EFI did improve things a lot though. Some of the cams people are driving around these days would have been kept for track use only just a decade or so ago.

Also as engine management systems evolved through time, more radical cams can be used with less issues, (LSx engines will most of the time have better driveability with the same spec cam than an LT1 will) but since we are talking and driving LT1s, let's be reasonable and think a little before you click the order button.

 

thats true..! For example here many people love rough/lumpy idle. But I really don't like it.. But the camshaft that I choosed will have kind a rough idle (237/245 113lsa) But for my engine going smaller than this cam specs will not be worth to 210cc AFRs and forged 383cid.. So there are many decisions before you spend money..

 

That cam should work well for your setup.

 

thanks I hope it will worth to rough idle

 

And then you get the opposite some of these guys throw together cheap combinations and put out great numbers. Thats what pisses me off. Then i didn't cut any corners and i've been battling problems forever.