Ok, who's thought of this... ok, rather, who done it. I'm thinking of 86ing two of my cats then replacing the other two with high flow cats.

Anyone know the price on a high flow cat. retail? What do we have 3 inch pipes stock? Anyone tried this?

I know I removed all four cats from my 1st gen L and it did seem to make a big improvement (especially in high RPM). I can only imagine is would remove a lot of restriction.

Or we could go to the 'good 'ol boys' way and just say "getten' me a long screwdriver and'll a havem' fixed in a jiff".

 

Crazy Bob has no cats with his Bassani, and let me tell you what, it is LOUD! SCARY LOUD! he does not think a made a big difference in power.

 

Removal, destruction, or replacement of funtioning catalytic converters with hi-flow cats is a violation of federal emissions laws. If your state has emissions inspections as most states or localities do, you could be subject to a hefty penalty. But I'm sure that you have taken that into consideration.

 

OK, so like, this time on the way home from race camp, I ran out of gas, and like all we had in the trailer was some leaded race fuel to get it home. Then when I replaced them it was cheaper to replace them with hi-flow ones
Perfectly legal.

 

I tried taking off the two larger ones and lost performance. Raced the same vehicle at the same track with no mods to his. Consistantly beat him with them on, consistantly lost to him with them off. Both are back in place. Take it for what it's worth.

 

I took off the Front PRE-heaters.....and replaced the rears with Hi-Flow cats.

Shoulda saved the money only gained about 9rwhp.

Lets see what happens tomorrow when I have the cat pipe shortened due to my new Long Tube Headers.

Maybe it will make a bigger difference NOW??

 

I'm kinda new around here so nobody knows me. But I am an engineer, and I work with engines everyday. I work in the the Engine Research and Design Department at SwRI. So maybe that short background will help give my thoughts some legitimacy.

Have any of you ever owned naturally aspirated cars in the past? Have you tried modding them? Have you noticed that no matter how bad the factory exhaust manifolds were, when you put shortys on, nothing significant happens? Then you put on longtubes, and holy moly, look at the power gains. Sometimes on 5 liter 'stangs it was 25 rwhp with a full exhaust with longtubes.

Now the lightning owners see that, and they think the same applies to them. But there is one huge difference between the two. And I'm sure everybody can guess that that difference is the supercharger. There are different forms of superchargers, but the fact that the L's is a constant volume device makes it special.

Since the supercharger is a constant volume divice, each turn of the rotor moves "X" volume of air. Therfore, the mass of air depends on the density of the incoming charge and the rotational speed of the blower. NOTHING ELSE. Take a look at the blower specs on Eaton's webpage. (The link was given on here a week or so ago, and probably several times before that). If you look at the first plot, the show flow in CFM at two different delta pressures. Notice how the lines are pretty much on top of each other.

Ever wonder why your L with a 2-valve PI head is rated at 380, and a new Cobra with a 4-valve head is rated 390. Only 10 hp different. While a mustang GT with 2-valve PI head is rated 260 and old Cobra with 4-valve head is rated 320. A huge 60 hp difference. The reason is no matter what you do downstream of the blower, the airflow is the same. 2V or 4V, port or no port, exhaust or no exh, cats no cats, the airflow is pretty much the same. Now when you make mods that increase the density of the air at the blower inlet (filteres, throttle bodies, larger MAF's), you can see that there will be more air mass flow through the engine. That's why these mods always show pretty good power increases.

When measureing power, there are several things you loot at. The IMEP give the indicated power looking at the thermodynamics in cylinder. The BMEP is gives measured brake power. The FMEP is the friction and is the difference of the two. All of the downstream modifications will show no difference in IMEP (and I used the term NO somewhat loosly as there is the possibility of 1 or 2 hp here or there). The BMEP may show some small increases due to a reduction in FMEP (and I'm lumping accessory drag in with FMEP). If you look at the next two plots on Eaton's page, they show that as delta pressure goes up (more boost) then the outlet temperature goes up and power consumed by the blower goes way up. If you change things downstream that allow the air to flow more freely through the engine, then what happens is the mass flow stays the same, but the pressures are slightly lower due to decreased resistance to flow. In other words, the boost actually goes down. Since the boost is now lower, the delta pressure is lower, and the power consumed and heat generated by the blower go down. This is what contributes to the slightly higher power. The IMEP is the same, its just that you reduced the FMEP, therfore increasing BMEP.

The problem is these downstream mods are very expensive for the marginal change in power that you get. Its also the reason the L in relatively inexpensive to get to go several tenths faster, and then all of the sudden, you hit a brick wall, and it costs a lot more money to go faster.

Now when the M166 comes out!!!!....the airflow can go up again, and the power can come up.

On another thread about the new mustang, people were questioning why it was "only" 390 hp. A response was that the exhaust was corked up to meet noise restrictions and that when you put an exhaust on there, it should go a lot faster. I replied that even if you uncork it, nothings gonna happen. A poster on here informed me that engines are a system, and that when you make changes in a system, it affects the overall system. I agree 100%, its just that you have to understand the system to get an idea of how the system might change.

That's my book about mods. Any other questions...feel free to ask. Most of the time, I'm the one asking the questions. It's certainly refreshing to actually understand something for a change!!

 

I have a question... Is it possible to make the L loud without a loss of power?

I see you are from SA as well... Have we met?

 

I just got my L about 3 weeks ago, so I haven't met anybody with an L yet.

 

'99 White Lite,

Cool post! Thanks for sharing, that's what it takes to make this community work.

Actually, no. If you were to convert a Cobra to 2V heads, you'd see a power loss.

You're mostly right. But you're talking about airflow through the supercharger, while the real issue is horsepower. That's generated by the OTHER air pump under your hood: the engine. Mass flow through the engine is what it boils down to, and you can't ignore the fact that heads with crappy intake ports are a big restriction to airflow through the important air pump: the engine. If the supercharger's airflow were the only thing that mattered, and if your 2V 5.4L vs. 4V 4.6L were a valid comparison, I could put an M112 on a Briggs & Stratton lawnmower and make 380-390 hp.

No, these mods show good power increases ONLY when the stock components are restrictive. A Lightning's factory air filter is restrictive, so replacing it helps a bunch. A Lightning's factory throttle body is not, so replacing it doesn't net much.

No, it's because factory exhausts are, in most cases, not that bad any more. A $450 throttle body nets a few horsepower to the wheels. An $850 set of longtube headers - a "downstream" mod - nets over twice that amount.

It all comes down to gazinta/gazouta. You have to pump air THROUGH the engine, and that means in as well as out. It's not just all about the supercharger.

Re: The '03 Cobra:
Let's make a second bet!


The M166 isn't coming out. There are other upgrade superchargers that are coming out, however. I won't go into it because it would turn into a flamewar.



Don't take this as a flame. It takes *****, as well as generosity, to want to post on here to teach other people. It takes even more guts to not get bent out of shape when someone says you're wrong.

 

Shoot me an email: steele@denimgroup.com

 

i have no cats with bassani headers and exhaust and its very very LOUD and i think i gained a little but im only very amatuer. im not like these other guys who know a good deal about this stuff.