[meford4u]

Just got off the phone with Marcy Motorsports in Cali, talking to them about their new 4-2-4-1 header---delayed until the SEMA show in Nov.--and after a lengthy discussion he came to the conclusion that I would be wasting my $ spending $450 US on the header and flex pipe with the SC application.
He said that we need some backpressure for the SC, and the shorty would provide this perfectly for us, as he has been testing both naturally aspirated and forced induction set ups for the new header, along with the FC,FS and JBA header, and said that I would gain a modest 3-5 hp, but lose torque.
He has suggested a random tech cat and just changing the flex over to a 2.5"

I know Marc And Kevin that you have piped up in the past about getting the race header, but this seems to go against what you guys have been talking about. Not to say your not right for a Focus that doesn't have forced induction, he even said that's where they are seeing huge gains of up to 15 hp, but with the JRSC, I am now rethinking the decision.

Comments???Anyone???

[FociS8nt]

so they are saying with an N/A motor its better to go with a shorty header and ORP or hi flow then a full race header??? :blink:

[boost til'bust]

yea, heres what I have to say.

Backpressure is not good!!!!!!!!!! it does not help to have backpressure!!!!!!!
if this would true, you would be saying that adding a kink to your exhaust pipe will gain you some performance, and we all know thats not true!

too many people think its backpressure that helps, when in actual fact its EXHAUST SCAVENGING that helps. basically exhaust scavenging is how when one cylinder fires, and as the exhaust travels away from the engine through the exhaust piping, it helps to draw out the next firing cylinder's exhaust gasses. As you open the exhaust and go to bigger diameter piping, this lessens the exhaust scavenging.

really I can only see exhaust scavenging as being important in an all motor car. For boosted applications, the bigger the exhaust the better.

thats my opinion on "backpressure"

[meford4u]

With the NA, it is better to go with the full race header to improve hp and torque.

The SC motor will not give you a great deal of improvement with a race header, and their tests have shown an actual decline in torque after putting on a race header to a SC Focus.

The change from a hi flow cat in the SC Focus will show the greatests improvement without sacrificing torque.

[tdot-zx3]

Yea... I knew that all along about the race header and the jackson racing s/c at low boost.... I guess you werent on focaljet back in the day but they had alot of info on this.

I dont think this would be the case for darkpuppets engine though, since his supercharger works more like a turbo. But who knows till you try right....

[meford4u]

It's the trying that can get expensive........... Not to mention a rather large pain in the ars----right Steve?

[darkpuppet]

haha.. the trying is the hardest part in the end.... stuff adds up quickly the more you try different things.

I agree that losing some of the backpressure will hurt your low-end torque numbers, and since the JRSC is pretty sparse on torque to begin with, I'm not sure if losing low-end torque is a good thing.

Now why would we be concerned with backpressure at low RPM? well, I think it's because the stock manifold, at lower RPM works more like a tuned pipe than a pressure-less sytem. At certain RPMs, the pulses generated by the backpressure help scavenge exhaust gasses, but ensure that your cylinder pressures are still maximized during the intake/combustion cycle.

By changing the exhaust, you decrease the backpressure, which improves the overall efficiency of the engine at higher RPM, but it hurts the scavenging effect at low RPM.. thus you lose low-range torque, but gain overall.

But you have bigger issues to worry about when it comes to your exhaust system.... you currently have some very aggressive cams on your car that could be hurting your cylinder pressures under boost and robbing you of valuable horsepower and midrange torque. I would look into that first before looking into an exhaust.

Once you maximize your gains with the current exhaust setup, you'll be able to gain more HP with a better exhaust, but you're ultimately going to hurt low-RPM torque numbers because high-flow exhausts are optimized for higher RPM ranges... what's good for flowing air/exhaust at high RPM could hurt the engine's breathability at low RPM...

just remember I didn't say anything about backpressure being good.. only that maximizing the efficiency of the exhaust is good.. but different sized exhausts maximize efficiencies for different flow characteristics which affect your power band at given points.

I think...

[ZX3 Canuck]

How about using the svt's 4-2-1 header, cat and flex?

[meford4u]

That's pretty much what he said Steve. We didn't talk much about the cams. I am hoping that that issue gets resolved with the cam gears, but we will see. Another expensive test run.

Both the low and mid range torque are sacrificed, they said, with the use of the race header, doesn't seem to matter which one in a boosted application. But as I said before, those with NA, this is still a big bang for your buck.

[Jays2000ZX3]

ONly thing I have to say here is:

-Look at Honda's.. (Yes, they are real cars) all the SC guys, be it JRSC or vortec run a Race header. Most guys use the Kamikaze header because of the big tubes. A Race header is worth it FOR SURE.

A Supercharged engine is similar to a NA engine when we're talking about the exhaust.

Either way, you'll find different people have different opinions but a race header is for sure the way to go.


**EDIT**

Just looked at a couple things on Honda-Tech and they use the Kamikaze because it has short primary runners and big secondary..so maybe a GOOD shorty header with a 2.5 inch cat/downpipe/flexpipe would be ok?

I dunno, I just think the shorty looks funny...

[boost til'bust]

Jays2000ZX3,Aug 31 2004, 01:20 PM Wrote:ONly thing I have to say here is:

-Look at Honda's.. (Yes, they are real cars) all the SC guys, be it JRSC or vortec run a Race header. Most guys use the Kamikaze header because of the big tubes. A Race header is worth it FOR SURE.

exactly...every other fast car uses a race header, but for some reason people with focus' seem to think that the engine in a focus is different than all other motors.

guess thats why their are no fast focus' out there :rolleyes:

[french_connection]

Meford4u problem will not be a race header and exaust flow,

problem----> exaust cam


solution-----> stock exaust cam and keep aggresive intake cam

retard exaust and advance intake.

buy race header


be happy. :blink:

could it be that simple? YES

[darkpuppet]

boost til'bust,Aug 31 2004, 11:1 Wrote:

Jays2000ZX3,Aug 31 2004, 01:20 PM Wrote:ONly thing I have to say here is:

-Look at Honda's.. (Yes, they are real cars) all the SC guys, be it JRSC or vortec run a Race header. Most guys use the Kamikaze header because of the big tubes. A Race header is worth it FOR SURE.

exactly...every other fast car uses a race header, but for some reason people with focus' seem to think that the engine in a focus is different than all other motors.

guess thats why their are no fast focus' out there :rolleyes:

good grief.

You folks are missing the point. I have not said anything about backpressure building ultimate power... I mentioned that the existence of backpressure can be beneficial for building low end power (due to tuned pipe properties)... something meford may wish to consider with the relatively anemic torque curve of the JRSC system.

Unfortunately, that statement can be a bit confusing... backpressure is bad, but the tuned pipe properties existent in a system is good. I should have probably stated it in terms of exhaust velocity. Maybe a quote from Sport Compact Car's Suck Squish Bang Blow article would make it a bit clearer what I mean?

Quote:Some self-proclaimed engine gurus claim too large of an exhaust tube on a car can cause problems; engines need a certain amount of backpressure to run correctly. Although the statement about not running too large of a tube is correct, the assumption about engines needing backpressure is not. A vehicle needs the lowest backpressure possible to produce the maximum power by keeping pumping losses low. Too big of an exhaust pipe causes power loss, especially in low-end torque, because a big pipe has less exhaust stream velocity than a smaller pipe. Velocity is essential to get the best scavenging effect from tuned headers. (We will discuss this in more detail later.) In simple terms, if the exhaust gas flow is kept high with good velocity, a vacuum can develop behind the closed exhaust valve allowing even better scavenging when the exhaust valve opens on the next exhaust cycle. Good scavenging is even more critical on valve overlap, the part of the four-stroke cycle where both the intake and exhaust valves are open.

I agree that on a turbo'd car, bigger is ALWAYS better, but that's because a turbo's efficiency is reliant on the pressure differential between the exhaust inlet and outlet sides.

Meford's car could definitely use a different exhaust cam, but once that's done, if he's looking for driveable power, he may not gain much with a race header other than a few extra HP in the upper reaches of the RPM range... but he could be sacrificing the torque that gets him going at a green light.

[Jays2000ZX3]

Let's see another graph of a dyno of a JRSC car...seems to me that the peak power, it at peak RPM..hmmmmm...obviously with a race header you are going to gaine a couple HP up top.... :blink: That's the point.

I forget what the torque curve on the JRSC does however...??

Ok, just had a look on JR's website..the torque is only like 130ft. lbs...hmmmmmmm let's see, by putting on the JRSC in the first place, you SERIOUSLY reduce the torque potential of the Zetec...so..why are we trying to gain 2-3 ft. lbs. now?

If you want torque, build a NA motor, or turbo. It's beenproven that the JRSC doesn't give you torque on a Zetec.

I mean, it's the only time on a Zetec that you see the torque lower then the HP.

so really..what's your point? It seems the JRSC is geared for top end/top RPM power, why would you want to do something different with a header?

:ph34r:

[meford4u]

The point is why waste money on a race header when I don't race the friggin car every day? The car is a daily driver. Period.

If I am only going to get 3-4 hp with a race header, but lose torque, well that's just not worth spending the $450US on a nice header. I would rather buy a nice Random Tech hi flow cat, get a bigger flex pipe and be done with it. No loss in torque and hp gains.

[Jays2000ZX3]

What's the point in wasting the money on a flex pipe and replacement cat when you are not going to be gaining anything?

:unsure:

380$US for a race header...sounds like a deal to me. :)

[Euro Ford Fan]

To answer your question nobody who wants big HP numbers.

But it's more about what you can put up with day to day rather than what you will accept for a trip to the strip.

Look at puppets car it makes decent power and is no louder than stock. Frankly I would consider accepting the restrictions and backpressure plus the loss of maybe 10HP to have a car that I could live with every day.

My simple theory on this is that if your running any sort of forced induction you want to get as much air into the motor and consequently as much air out of the motor as you possibly can. For big HP backpressure is your enemy.

Since I never successfully turbo'd my Focus I can only use my XR's for comparison.

My old 88XR made 199HP 205TQ after its motor rebuild everything was totally standard boost was at 15psi. I went to a full 3" system downpipe - tip and picked up 26HP. Most of this was HP I believe was gained with the addition of the 3" downpipe and the swap to a 3" cat. I don't believe the 3" pipe made all that much difference because I simply wasn't running that much CFM through he exhaust.

Now on my race XR I swapped the head from a stock unit to a PM Motorsports Stage 2 with a 480 cam and it went from 246HP to 298HP I then swapped out a gutted upper intake and ported and polished lower for the PM Motorsports Log Manifold and picked up a further 32HP. I know I could have see even more HP with that gain but at this point my turbo simply could not produce enough CFM to fill the intercooler, pipes and the new intake manifold this was plainly evident on the dyno chart.

As for the exhaust side a swap to a SS tube header shows gains of on average 40+ HP over the stock ported E6 manifold. That was on a mildly modified car running about 20PSI on the stock turbo so my suggestion if you can only pick up 3 or 4 HP with the addition of a race header on a blown application don't bother because there is a bigger restriction that needs dealing with somewhere else in the system.

[meford4u]

Jays200zx3 wrote"What's the point in wasting the money on a flex pipe and replacement cat when you are not going to be gaining anything?"


But you will gain a lot. As Euro Ford Fan said, in which I agree, you want to get as much air into the system, and out of your engine as possible. What I am looking at is whether the race header will greatly improve that for my daily driver.

I will be gaining hp with a hi flow cat. Somewhere in the neighbourhood of 10-12hp with the cat and a larger flex pipe. The addition of the race header, I don't think I would gain much more than a total of 15hp with the race header, flex pipe, under car hi flow cat.

So why spend $450 for the flex and header, another $100 on the cat, when all I really need is just the hi flow cat and a new flex pipe?

An we have to live with the neighbours everyday. We all know that race header is going to be louder, not something I am willing to accept for a daily driver. I have heard some of the guys bemoan their noisy cars on the highway. I will lose 3-5 hp for a lot less noise.

I noticed your earlier edit Jay, and that is exactly what I am looking at with the JBA shorty header, random tech hi flow cat and a 2.5" flex. Good call

Oh and one more thing, Marc and Steve, I am hoping that we can combat some of the cam problems with the cam gears. But if that doesn't solve the problem, then yes, back to the stock exhaust cam gears we go. We are not doing the work right now, as we are enjoying the car being driven. When the car goes to bed for the winter, let the tuning games begin!!!

Cam gears, change in header/exhaust TBD, hella fog lights, stainless brake lines, plus other goodies, then off to the dyno in the spring.