It is all about A/F ratio. Most cars (Z06 included) run a bit rich from the factory. This is done to protect the motor. If your airbox introduces a bit more air into the motor and you run the correct A/F ratio you will make more power. This is a fact, not an opinion. You may need a MAFT or LS1edit along with your airbox to get the proper A/F ratio.

FWIW, just tuning the A/F ratio with a MAFT or LS1edit will probably provide power gains even if you are still running the stock airbox.

 

rbartick,

I agree that A/F is a big part of the improvement, it would be interesting to have someone MAFT tune a stock airbox and get before and after dyno results then switch to a top breather to see what additional gains, if any, are realized.

Airflow and air temp also affect performance with respect to combustion efficience. I believe that is why the Vararam (Optic) edged me out on trap speed with his bone stock car except for the Vararam against my lightly modded car with the T1. On the dyno I had almost identical power but he pulled me every friggin time :) Now I have the Vararam so we shall see what we shall see :)

Les


[Modified by ZO6Les, 9:52 PM 7/10/2002]

 

True.

In my book air flow, air temp, and A/F ratio are all closely related parameters. For all we know the 'Ram Air' effect of the VaraRam may be causing the A/F ratio of the V.R. equipped car to lean out a bit at speed, causing a slight gain in power. Too bad these cars do not come with wideband O2 sensors.

Theory:

Maybe the PCM does not have time to learn and enrichen the additional RamAir airflow since it only happens when you race at high speed, not when you cruise at normal speeds. I am guessing most of us cruise more than we race, which would bring the LTFT values down. Maybe when you do a 1/4 mile pass and hit about 100 MPH the additional RamAir airflow starts to lean out the A/F ratio??

Monitoring the MAF readings at cruising range and high speed WOT with Autotap before & after the Vararam would be a good idea.





[Modified by rbartick, 6:29 PM 7/10/2002]

 

It would help to know what goals differant members are trying for. If thay are looking to get the "claimed" result,on a dyno so be it. The number of assumptions some make is the problem. Tom thinks because he read 12.4 HE is going to run 12.4? That's not the reality you will find tom, when you go to the track, it may be faster or slower. Most ALL the racers are only interested in REAL RESULTS on the track, and those transfer in a real way to how fast your car is. It's fine in the world we live in to make "claims" apparently. But if your interested in geting quicker times differant systems DO produce differant results. Even if the dyno number is same or similer, whats the average hp and how long did it take to reach it are valed questions but in my oppinion if it's not quicker and faster so what?Dyno's are for tuneing ONLY or shuld be. I have run with the stock filter, K&N, cover and no cover and VR. I can let you know with worked better on the track for me, trying to put real fact's on the fourms is valuable in my opinion, not everyone interperts them the same but most are only trying to relate the truth as they see it. It nice to know why some things work better than others, but in the case of car mod's it's more important to know if it works better. The number of varyables is to high to be worth a scientific understanding for me at least on simple mods for my car. How well it worked foe me is the most important thing because I race on a track not dyno's or fourms. Everyone does get to decide what's best for them self it's just helpfull to see the differance between claims and real results. Try this stuff for your self, and you will quickly find out how easy real results are. IMHO Ric

 

EXCELLENT POINT. Now, let me ask this. How long before the computer relearns the air/fuel mixture and takes away that 15hp?


I hadn't thought of this, but it would make some sense that the computer might be tricked into running a tad leaner. The problem I have with that, is that I believe the computer is pretty good at adjusting, and will richen it back up over a short time period.

This is the kind of discussion I was talking about. Now we aren't arguing, we're thinking!

I have mixed thoughts on this. Obviously GM thought enough of the low-to-the-ground air that they included "cold-air" vents on the front of the car. But as many folks have asked, is the air down there that cold? The closer you get to black asphalt, the hotter your air gets... That's something your not going to see at the dyno either.

My jury is still out on that. I'd like a cold air induction somewhere around the headlights before I really considered it "cold."

To be honest, my options are very limited where I live. We have a few 1/8th mile tracks, they aren't real close though, and I'm from Florida originally so I grew up with and really prefer 1/4 mile tracks. Plus, the C5 performs MUCH better on a longer track. It isn't geared well for 1/8th mile.

I used to race a bit in FL when I had my Mustang Cobra. I even won sometimes. :) But I didn't race professionally.

I'm even in an old issue of Super Ford when I won the trophy class in my 93 Cobra. :D That car, with only 3.55's and shorties would run 13.70's on street tires (not drag-radials, just plain old 245/45/17 GSC's). And it would run them consistently, which is nice in bracket racing.

However, on to now - I'll race just about anything that pulls up beside me (I know, CF does not condone street racing, neither do I ;) ) if the situation looks right. (No heavy traffic, cops, road look is safe for racing, etc...) So I do care about winning.


Lights have EVERYTHING to do with who crosses the finish line first though!

I'm surprised the shorties didn't do anything. I assume they dropped a few lbs off the car though. We have iron manifolds now, right?

I don't want ugly under the hood either, but I also think if it comes down to it and I can make the car go faster without spending $400 on an airbox, then I'd like to know about that. And I might even be able to piddle around in the garage and do it myself and make it look good.

I think there are a lot of questions still to be answered about the airboxes, and I enjoy the discussion. Sorry if you felt attacked, that wasn't my intention!

 

Well, the reason I jumped in this discussion is that I have a healthy dose of skepticism about the science behind the air-boxes for sale to C5 owners. You might have been able to tell that! :D

My skepticism starts with the OUTRAGEOUS claims that many of them make on their websites. (No one here even claims to believe the numbers the manufacturers quote!) I think, "If they (the makers) are lying here, then they no longer count as a source of VALID information about how the product works at all." Besides, you KNOW they have a vested interest in making their products look good.

So, then I ask other questions. Start with ram-air. Any aerospace engineers here? I actually have a degree in Engineering/Physics so I'm not just making this stuff up, although I also freely admit I don't do that for a living and I don't claim to be an automotive or aerospace engineering expert. But, I know some aerospace engineers, and they all tell me the same thing. Ram air doesn't really start to happen until around 300 mph. Anyone differ on this? Even if I was off by a factor of three, it wouldn't matter for our cars.

Furthermore, the "ram-air" effect we are talking about with these filter-systems, is further negated by poor ducting paths and poor sealing of the ducting. I don't think the air-pressure is a factor. But the manufacturers say it is. They aren't being truthful.

So now vararam is just vara - whatever that means. ;)

Don't get me wrong. I'm not one of those folks who believes that all Z06's run 12.40s out the door. I was just using those numbers for argument's sake. But you make a valid point. I should have asked Les what the car ran stock and how much those mods have lowered his e.t. Les?

And I'm not attacking modifications. You HAVE to mod the car to make it faster at some point. I'm just skeptical of a particular mod, the airbox.

I think we are 100% in agreement here, we just approach it differently. I think the "claims" made on these air-boxes are outrageous. And I'd like to make sure they are verifiable before I send $400 to a snake-oil salesman.

Personally, I think the manufacturers of these items believe some of their claims. It is VERY EASY to believe the ram-air effect makes a difference. It SEEMS so common sense. But when you do the math, you see that a perfect system might get you 1/10th of a PSI boost at track speeds. That isn't going to make many extra hp.

I'll post that info in a separate post here, for anyone who cares.

I agree wholeheartedly, but I also think if you analyze the numbers, you should be able to accurately predict whether the car will be faster.

Area under the curve is almost everything. Peak hp is just a subset of that and not nearly as important.

Figure out your rpm range (in every gear, first really makes the equation more complicated!) and your hp for that section of the curve and you will know a lot more about how a car will perform than just looking at a peak hp number.

But lots of things matter. Wheelspin is critical. Not only does it reduce your e.t., but it usually increases your trap speed. Sounds odd, but it has to do with the amount of time you had to accelerate (more, since you were spinning at the bottom) and is pretty common.

It would be easy to think, "look, my trap speeds were higher so I was making more hp, and I was spinning because of that extra hp!" In reality, it may simply be that the spinning was making the trap speeds higher, but it could easily be mis-interpreted.

Well, I say give a man a fish, he eats for a day, teach him to fish and he eats for life applies here. I'd like to figure out WHY if I can.

Dynos suffer from the same problems as actually going to the track. Corrected or not, the weather, operator and such can make a difference.

Now, I'd like to see something like, bring the car in to the dyno with stock (or whatever) filter. Measure it. Change to the new filter. Measure it. Go drive it for 30 minutes to let the computer re-learn it. Measure it.

Now, we have eliminated a great deal of the variables and have better information. We have the same dyno, same operator and same day.

Only problem with that, as I see it, is that those variables can come back to haunt you. Unless you race a LOT, you may think you have gotten some gain from a particular filter, but in reality it was one of those variables you didn't eliminate.

I'm not trying to upset you guys, I just have my doubts about how, and perhaps even if, these airboxes make their gains. It isn't a slam on you or intended to be personal.

I hope you take my discussion in the way they are intended, which is to try and understand how, and if, the airboxes are truly getting their power or are they a marketing scam.

 

Carroll Smith in "Tune to Win", P. 106 sez.... (most of his experience comes from INDY racing, good book..)

Intake Ram (psi) =

Air density (lb/ft^3) X (Air velocity in FPS)^2
----------------------------------------------
288g

80 mph:

.076 X (118)^2
---------------- = .11 lb/in^2
288 X 32.2


BUT he goes on and says:

"In both cases we have assumed a 100% efficient duct, which is not possible---75% efficient would be a good one"

Turbulence isn't the real problem. In any piping run, a boundary layer builds up next to the wall where the flow velocity is actually zero. As the roughness of the pipe wall gets worse, the boundary layer grows thicker. As the air moves on down the pipe, it is slowed by the boundary layer effect (head loss) and the boundary layer essentially grows thicker slowing the air more. If the run is long enough, the head losses can actually be long enough to completely stop the flow (pressure differential between the inlet and outlet is zero).

Take the vent on your dryer and add about 30 feet to it and you'll see that there's not enough pumping power (from the exhaust fan) to even move the air through the hose. The same head losses occur every time straight flow is interupted by a bend, valve, fitting, etc.

There's a piping engineer's bible published by Crane Valves (Technical Paper #410) that puts all the equations together and will let you calculated the pressure drop through a piping network with all the variables you could think of.

--------------------------

Tom's note, I saved this from a Ford forum years ago when I had my Mustang and there were a lot of folks out there trying to make ram-air for them. (Myself included) I ended up throwing mine out...





[Modified by Tom Steele, 10:25 PM 7/10/2002]

 

Some of us have already done that. There is more to it than you think. You also have to worry about heat soak/timing issues when running on the dyno.

If you get more air into the engine and mix it with the proper amount of air (resulting in a good 12.8 WOT A/F ratio) you will make more power. The power increase may not be big enough for some people to justify the time & expense. Others, like me, love to tinker and will work toward every gain.

:)

 

Les: It is a FACT that my T1 made 15 RWHP when 1st installed. You don't have to believe me or the many others who have had similar results.

It works for a top or bottom breather because it flows more CFM than stock which in turn leans the car out a bit and the combination = more power. The vast majority who have dyno'd the cars get similar results.

Tom: EXCELLENT POINT. Now, let me ask this. How long before the computer relearns the air/fuel mixture and takes away that 15hp?

Les: I did a re-dyno 300 miles later, and the power had dropped by 5 or still a net gain of 10. A/F had gone a bit richer to 11.8 vs 12.4. That is when we noticed the ECM pulling timing on the high end (not due to knock) and kicked off the whole injector debate. Replaced injectors with 30# and installed the MAFT - retuned, picked up 11 more RWHP (net 21 higher from stock). That number now varies between plus 19 to plus 21.
__________________________

Tom: This is the kind of discussion I was talking about. Now we aren't arguing, we're thinking!

Les: I wasn't trying to argue before :)
________________________________________ ___

Les: The Vararam or any bottom breather also brings in more and colder air as you move but this can't be duplicated on the dyno. I will have track results soon.

Tom: I have mixed thoughts on this. Obviously GM thought enough of the low-to-the-ground air that they included "cold-air" vents on the front of the car. But as many folks have asked, is the air down there that cold? The closer you get to black asphalt, the hotter your air gets... That's something your not going to see at the dyno either.

My jury is still out on that. I'd like a cold air induction somewhere around the headlights before I really considered it "cold."

Les: I too was not convinced about how much, if any, the Vararam bottom breather did over a top breather. In fact I have been attacked as a Halltech clone for being so pleased with my T1 :) My jury came in when I raced Optic on a VERY hot day, cars had nearly identical dyno numbers and yet he pulled me in 4th gear. I had ALL my mods, he had only the Vararam. I had hoped to race tomorrow but getting a lot of rain, but I am waiting to see if my SOTP feel (which is VERY positive) on the Vararam is backed up by track results.
________________________________________ ______


Les: BTW when you drag race the lights have nothing to do with E/T or MPH, so my original point stands. BTW the Shorty's added zero power - waste of money and I am not ashamed to admit it (have done so in the past).


Tom: Lights have EVERYTHING to do with who crosses the finish line first though!

Les: You bracket racers are all alike :) For me yes I like to trip the lights first but it is the E/T and MPH on my little white slip that floats my bubble :)

________________________________________

Tom: I'm surprised the shorties didn't do anything. I assume they dropped a few lbs off the car though. We have iron manifolds now, right?

Les: I was surprised as well, as others claimed 10+ RWHP improvement. And yes you lose 16 pounds of weight going with the shorty's. My Z06 with 5/8 tank of gas weiged in at 3015 (no driver) which suggests what with an 1/8 tank the car is under 3000 - an amazing number IMO.
____________________________________

Tom: I think there are a lot of questions still to be answered about the airboxes, and I enjoy the discussion. Sorry if you felt attacked, that wasn't my intention!

Les: Peace (or piece :)



[Modified by ZO6Les, 2:43 PM 7/11/2002]

 

Tom: So, then I ask other questions. Start with ram-air. Any aerospace engineers here? I actually have a degree in Engineering/Physics so I'm not just making this stuff up, although I also freely admit I don't do that for a living and I don't claim to be an automotive or aerospace engineering expert. But, I know some aerospace engineers, and they all tell me the same thing. Ram air doesn't really start to happen until around 300 mph. Anyone differ on this? Even if I was off by a factor of three, it wouldn't matter for our cars.

Furthermore, the "ram-air" effect we are talking about with these filter-systems, is further negated by poor ducting paths and poor sealing of the ducting. I don't think the air-pressure is a factor. But the manufacturers say it is. They aren't being truthful.

So now vararam is just vara - whatever that means. ;)

Les: I have always been a sceptic about ram air systems, aftermarket or factory. I can say without hesitation that the Vararam bottom breather pulls better than a top breather (see other post). How much of this is due to colder air and/or ram effect and/or better design I can't say, only that it works!
________________________________________ ___

Powershifter: Tom thinks because he read 12.4 HE is going to run 12.4? That's not the reality you will find tom, when you go to the track, it may be faster or slower.


Tom: Don't get me wrong. I'm not one of those folks who believes that all Z06's run 12.40s out the door. I was just using those numbers for argument's sake. But you make a valid point. I should have asked Les what the car ran stock and how much those mods have lowered his e.t. Les?

Les: My car did pretty consistent 12.8's before I starting modding. I have raced a number of other Z06's here and near Atlanta and that seems a pretty normal number for a stock car and fairly experienced driver. I started modding pretty quickly AND raced quite a bit to get seat time and my E/T's dropped like a stone. Also MPH improved from (stock) 113-114 MPH to 116-117 MPH. I would personally attribute the improved E/T more to my improved 60' times (2.3 improved to pretty regular 1.9's, even a 1.8X) then the power (though that does help too) but all the MPH would be from increased power IMO.
______________________________________


Les



[Modified by ZO6Les, 2:40 PM 7/11/2002]

 

Excellent discussion!

I'm curious how you got your launch times down to 1.9's. What is your technique? Is it the generally accepted 2000-2300 rpm and feather the clutch in real fast, or are you doing something different?

I find that just dumping the clutch gets surprisingly good traction under 2,500 rpm, but horrible wheel hop and a bog. I assume that the best way to leave is to feather the clutch to absorb some of that energy?

Also, I'm curious about your injectors. I am unfamiliar with GM injectors. With the old Mustangs, the stock 5.0 came with 19lbs and the 93 Cobra had 24lbs injectors.

I assume the stock Z06 comes with something less than 30lbs and you increased your sizes. Doesn't that go against the whole "lean it out a bit for more power theory?"

Also, I am not familiar with the MAFT, but judging from the context here, I assume it is a tuning device or is it just a "trick the cpu" device?

Is that how you are trying to get your WOT air/fuel to where you want it?

I was looking back at the earlier posts, and someone asked what was my goal. One thing I want to do, is pick the brains of the folks recommending these items so I DON'T have to do 8 million dyno and track tests. Neither is an easy option for me, so I want to hear stuff like we are discussing now, before I go burn $400 for an airfilter system. I don't have the time, or facilities nearby to do all those tests, so I am going to ask more questions before I pay for, and install these items.

Also, some items could actually take away hp and many people wouldn't notice. SOTP is rarely a good measuring device. Especially for something that probably increases hp at the TOP of the powerband. It's hard to know if you have added 10hp (2.5%), especially if the gains are at the top of the rpms.

And, if you have to buy three or four brands before you buy the right one, then your expenses rise even more.

Thus, I am very picky about my information. Hope that makes sense.

 

I'm ALL for maximizing the a/f ratio, BUT I want to make sure the computer isn't going to learn itself right back out when I step away from the dyno. And, I don't want an a/f that will leave me with detonation for obvious reasons.

 

>I assume the stock Z06 comes with
>something less than 30lbs and you increased your sizes. Doesn't that go
>against the whole "lean it out a bit for more power theory?"

When you increase airflow the PCM will have to increase Injector Pulse Width to maintain the proper A/F ratios. If the Pulse width gets close to full-duty then you may have issues with things like timing. A bigger injector allows the Pulse Width to come down and still gets the same A/F ratio


>Also, I am not familiar with the MAFT, but judging from the context
>here, I assume it is a tuning device or is it just a "trick the cpu" device?

Mass Air Flow Translator, changes the MAF signal. See here: http://www.c5forum.com/diy/ltft.php

>I DON'T have to do 8 million dyno and track tests. Neither
>is an easy option for me, so I want to hear stuff like we are discussing
>now, before I go burn $400 for an airfilter system.

If you want more power you WILL have to do multiple dyno runs and Autotap/Ease readings. You will need to record wideband O2 readings on the dyno. All cars and climates are different so there is no way around this

 

Tom,

I launch at 2800 RPM, 24 PSI tire pressure "releasing" the clutch quickly (but not dumping it like I do on my race car) and as the clutch engages Press (don't stab) the go pedal. I also give the tires a pretty good (2-3 second) dry burn-out and stage as shallow as possible. If the track is above 70 degrees and has some VHT on it I can get 1.8-1.9 most every time on the stock tires.

The stock injectors are 28#, I replaced with SVO 30# injectors. You are right, the MAFT "fools" the ECM into believing the car is running richer then it is. If you swap the injectors without a MAFT (or LS6 Edit) you will run VERY rich as the injector pulse width remains the same. The stock injectors run nearly 90% duty cycle from the factory (better spray = lower emissions is why they do it) but the ECM will yank 5 degrees of timing out at WOT beginning at 4K RPM's if you have even the slightest of mods. The larger injectors and MAFT solves this issue. So yes that is how I am able to run 12.8 A/F, no knock (in the heat).

Les

 

I've gotta say one thing though, and I'll gladly defend myself on this, but I just went to the following web page:
http://www.vararam.com/technical01.html

I don't think I've ever seen a bigger load of crap.

You know Les, I think the reason I am so rough on you guys, is that when I read these websites, it is so hard for me to believe ANYTHING the manufacturers say. So I am extremely skeptical of the whole mess.

From that page:

To truly understand "ram air", you must first fully understand the dynamics of the internal combustion engine. It has four cycles: an intake stroke, a compression stroke, power stroke and exhaust stroke.

Thanks for the "remedial four-stroke engine 101" course.

For our purposes, we will concentrate on the intake stroke. The basics are this, as the intake valve is opened and the piston travels downward this drop in pressure causes air to be pulled into the cylinder. Once the piston reaches the bottom of it's stroke (BDC or bottom dead center), the piston begins to travel upwards by 1 to 4 degrees of crankshaft rotation (compression stroke). The intake valve has not yet closed and the pressure waves from the intake stroke are still drawing in air/fuel mixture. This causes a "Supercharging" effect in the cylinder. There's a lot more to this, however. Any more information could confuse this explanation.

Yeah, it sure could confuse it, cause you might have to get into facts that would show what nonsense they are spewing. The best part, is that the basic description of the four-stroke process is true. But what does it have to do with ram-air???

This process is called Ram Tuning. That's right, ramming air into the engine by using what is already given in the design of the internal combustion engine. However, very few engine builders truly understand this sophisticated form of engine tuning. Tuning by using pressure waves in an engine once exploited can add 30-70 BHP to an engine's total output without a ram air system.

Now we get to the fun part. So, GM doesn't understand tuning a camshaft profile??? Which is REALLY what they are talking about here. Ram tuning is a function of the (real) intake manifold and cam shaft and heads. Not the air filter.

And they make it sound like this is recently discovered stuff, that only they know about! Hey, NEXT THING YOU KNOW, they are going to tell me that the exhaust valve is open the same time as the intake and that is called overlap!!!

So, why am I telling you this?
Simple.

To try an get you to send me $$$ (How much are these things? I can't find them anywhere except vararam.com and it says call for price).

Now imagine a large volume of air pre-packed behind the intake valve waiting for the valve to open. When the valve opens, this pre-packed air charge will create an even greater rush of high velocity air into the cylinder creating an even larger, faster pressure wave. This produces an even greater "Supercharging" effect. This is ram air.

So I assume, since the LS-1 and LS-6 have different cam profiles, that the Vararam's for these two engines are quite a bit different, being that this is a sophisticated method of tuning that most engine builders don't even understand.

Or are they virtually the same, because in reality, they are just like every other bottom breather out there, with perhaps a slightly classier looking design using the "Z06" factory openings for the air intake?

Patrick?

 

Tom,

I have never checked their web site, never will. For both the T1 and Vararam I went off other peoples real experience as well as personal observations racing and seeing others use these units. The whole ram tuning hype is just that IMO. As I said I believe it is the "cold air rules" that makes the Vararam a bit better as a bottom breather, and getting that colder air to the T/B "quicker" with the "ram effect" makes sense to me too. The rest is, I agee, more :bs than science.

My advise, forget the manufacturer website and stick with people you know and/or trust. Down the road hopefully we will all learn to know who to trust on this forum :flag :flag :) :)

Les

 

Hey Tom:) Glad to see you back. Thanks again for the CD ahwile back.

We offer the money back gurantee that VaraRam offers on their homepage. If you'd like to try it, I'd be glad to get you one and honor the guarantee.

If you don't think it will work, I can appreciate your position and just say that I have very happy customers using it who've made gains with increased trap speeds and reduced their et's. As far as the science of it, my degree was on the business side of things so I leave that to the professionals who design these things. All that being said, I need products from suppliers that work and that they stand behind, bottom line, because that's what you want and deserve, along with everyone else. That's what sells and that's what people are happy with, what works. I feel very comfortable with that focus in mind.

I have a ton of customers happy with the Vortex unit...and I use that one on the current car...just not the next one as I think the V/R will look nicely on my new Z, when I get it, and will out perform the others out there, as long as I can do my part behind the wheel.;)

If I could offer driving skill in a bottle for a price, I'd be on the beach typing this.:)

RG





[Modified by RG in Dallas, 11:47 AM 7/11/2002]

 

Very good info. Thanks for the tips. I'll have to try that. I'm probably not gonna be at the track anytime soon, so I'll have 30lbs, but I'll drop the rpms a little and try that and see how it leaves.

My 93 Cobra was pretty much a "find the right rpm for that track surface and sidestep the clutch at that rpm" system.

But I am used to the 2000 coupe I had for the past 2 1/2 years and know about the wicked wheel hop if you try that with a C5. I am used to easing into the clutch, but figured with more hp, and fatter tires, the Z06 would be a bit different.

Does autotap just show you what is going on, or can you change things? Seems like that would be the best option, rather than just trying to trick the cpu. But I have done a bit of that in my time with Mustangs. It is a lot of work to get that sorted out.

Thanks again for the info!

 

Auto-Tap is a 'reading' tool. LS1-edit would make changes to the pcm.

RG

 

RG,

Good to hear from you. I may take you up on that offer. The money back guarantee is a nice thing. At least that makes the manufacturer live up to their claims, or take it back.

I'll let you know what I decide to do.