I was thinking about this for some reason. Here's some myths and misconceptions FYI.

The first concerns plugs and wires. There are no plugs or wires that will add any hp to a stock or mildly modded LT1. So why do some apparently reliable people say they will? Most likely because they are replacing old, malfunctioning parts with new. But the stock parts are fine with stock or mildly modded motors.

As with plugs and wires, coils and ignition boxes are also pointless mods for stock or near stock car. The OEM pieces are quite up to the job of efficiently igniting the mixture and there are no gains to be had replacing them unless they are malfunctioning.

Another concerns changing the fuel pressure. The stock tune for an LT1 is a little rich, so leaning it out with an AFPR will add a few hp. But the change won't last, due to the ability of the PCM to learn. No, the PCM does not directly sense FP. But over time will compensate for a lean condition and bring the mixture right back to where it was. You can still use the AFPR to improve track performance by clearing the PCM before each run. But you won't gain anything messing with the FP in a typical street situation.

A related myth is that there are gains from making timing changes. The stock timing is quite agressive and only works because the knock sensor function allows improper operation (low octane fuel, high load at low rpm, etc.) without damage. There will be no gain from advancing the timing on a stock or mildly modded vehcile running on pump fuel.

Here's another that relates to modded cars. It's the idea that stiff valve springs rob hp. They don't, at least to any significant degree. Of course, it takes more power to compress a stiff spring. But nearly all of the power is recovered when the spring expands, and it expands as often as it compresses. The process is not 100% efficient, some of the energy is lost in each cycle to heat. So there is a very small amount of power lost to stiffer springs. But it is insignificant.

A more semantic misconception relates to valve events and rocker ratios. You may hear it said that higher rocker ratios increase duration. They do not. Duration refers to cam characteristics, not valve events. What higher rocker ratios do is increase dwell at intermediate points on the lift curve. This has an effect similar to a cam with more duration (and lift) but isn't quite the same and it's just confusing to say it is.

Rich Krause

 

thank you. now go tell all the grand am owners over at gmpower the same things about their 3100s. =)

 

Are you just doing this so that the newbies know who's the man?
J/K Those are very intelligent pieces of advice.

 

Thanks Rich. I am sure that will save some people a little money.

 

Thanks Rich,

I have a question reguarding timing though. You say the stock timing is aggressive enough already. I was under the impression that was where most of the gain from my pcm tuning came from.

I'm ignorant about our PCMs because instead of doing my own tuning I chose to go with PCMforLeSS because Bryan lives right down the road from me and I didn't think i really had the time to learn LT1edit myself. Not to mention the software was more expensive. Anyways, my car ran noticeable better at low rpms. The car was still stock so it wasn't anything huge, but noticable. I assume it ran better up top too but never had it dyno'd before. Realizeing that the stock program is darn good, what adjustments do people make that are beneficial?

 

Continuing what rich said in a less technical and highly "mispeeled" manner-


Hypertech is a waste of money
you dont need to port you MAF if you are running stock internals
You dont need a bigger throttle body if you are lighltly/moderatly modded

(and I was guilty of this one)
Nitrous does not like nor require lowered compression. It is not high pressure air like a s/c turbo setup. It is a gas with a high concentration of Oxygen.

when you want to see how much compression you can run before detonation- look at dynamic compression, not static compression

[rskrause]
When picking a cam, lift is your friend if your valvetrain can hold it
[/rskrause]

cross drilled and slotted rotors will cause you to stop WORSE than blank rotors (do a search, i refuse to go through this again- at least not for another week )'

HP and Torque dont break rear differentials. Shock does. so you can have as much power as you want, but its all in the launch

Dont waste your time porting your intake if your heads and such are stock

bigger fuel injectors dont mean more power- only if your current injectors are maxed out.

 

Another concerns changing the fuel pressure. The stock tune for an LT1 is a little rich, so leaning it out with an AFPR will add a few hp. But the change won't last, due to the ability of the PCM to learn. No, the PCM does not directly sense FP. But over time will compensate for a lean condition and bring the mixture right back to where it was. You can still use the AFPR to improve track performance by clearing the PCM before each run. But you won't gain anything messing with the FP in a typical street situation.

Does this apply to 93's?

 

those two irritate me

i run into fbody owners in random places...........and they always ask what mods i have, then say

"dude, get a bigger maf and throttlebody!!.........oh yeah, and rip out that stupid screen in the maf!"

try as i might to explain that these have almost zero effect and possibly a negative effect on a mild-moderatly modified car, and they just start regurgitating stupid crap at me.

ugh.

 

Best thing to do... correct the misconceptions in the thread.

I would say that higher rocker ratios don't increase "dwell" at all. What they do is expose a greater amount of valve area per degree of crank rotation.... giving the cam more effective lift area per degree of rotation. I agree though, not "duration" from a seat to seat perspective.

And my C5 stopped quicker with a change to slotted Baer discs.

-Mindgame

 

i think trey's statement was much to broad.

in theory..........if two rotors are the same size..........and one is slotted/drilled/dimpled.........and one is blank.....all other things equal......then the blank rotor should stop the best on the first try because of more contact area. after the brakes heat up, the slotted/drilled/dimpled will brake better because of better heat dissipation and less brake fade.

how many times do you go out and only use your brakes once? so slotted/drilled/dimpled would be best for repeated breaking.

if im completely wrong, please correct me and ill delete my post.

 

The discs I'm referring to were a direct swap, no +1 sizing or anything like that.
Same diameter, same thickness except the Baers were zinc washed and had slots. The oem discs had Performance Friction CM pads on them before the swap and the same (but new) pads were used on the new slotted rotors.

-Mindgame

 

I think this is going to be a long one.


NICK

 

well hopefully you realized i was agreeing with you...........the only time i could see a blank rotor having an advantage is on the very first time using the brakes when theyre cool.

 

he is right, hotter rotors and brake pads cause slower stipping..........that is the whole point of slotted and cross drilled rotors...........ever heard of brake fade.....lol

 

That's a good question! I don't think my point applies to a '93, but am not sure.

'game: the cam thing is a semantic issue. I am sure we both know what we mean and it's the same thing. It just annoys me when I hear people talking about how they have altered "duration" by swapping rockers with a different ratio.

94formulabz: I was talking about WOT. The stock programming isn't perfect, and I am sure a skilled tuner can make some worthwhile changes. Just trying to point out that the timing is already optimal for WOT under good conditions and advancing it further will not do any good unless you are running some exotic fuel or some other odd conditions. In fact, you will see less hp with pump gas if you try to add timing.

Rich Krause