Portmaster

His exhaust isn't helping his power as of Right now. Not everyone buys aftermarket heads. I'm not a mind reader so I have no idea what he's going to do. If My car had 5:13 gears in it I wouldn't leave them in because someday I might turn it into an 1/8 mile car. His exhaust is too large, Joel disagrees. Thats fine.

Joel5.0

1. Why is the exhaust in his setup too large?
2. How could it not help the setup's power? ......provided he correctly tunes for it, which is 100% doable. BTSTDT, have you?
3. If the exhaust is too large, why does a properly tuned setup with C3/C4/C5/E7/GT40/GT40p heads perform better, with open headers? BTSTDT, have you?
4. So it makes sense to spend $$ in choking the exhaust, rather than utilize/capitalize its better exhalation cycle capabilities and spend that $$ on the intake instead? Why not match the inhalation cycle in the engine? Wouldn't a better breathing engine setup make more average power?
5. ...5.13:1 gears compare to a 3" ID full exhaust?.....

Would that be too much "techno babble BS" to answer?.... for the benefit of the OP and the membership?

Portmaster

1. His exhaust being to large slows the flow of exhaust through the headers thus reducing the scavange effect at the collector. His 3 inch exhaust from his big long tubes back only help one the engine reaches full flow. The E7's will never realize either.

2. You can no more tune a car with E7's to work at an optimal level with too large exhaust anymore that you could with to large a Carb. There IS a point of no return when going large

3. Who runs open headers on their street car?

4.Did I ever say he should choke the exhaust? NO. Nothing like that was ever said. Sorry your word play doesnt fly. Yes it would be great if he could do an intake/Head and Cam Combo to match his exhaust. I don't deal in what if's just the problem at hand . A set of smaller headers are as low as 99 dollars.

5. Yes thats what I said.It make about as much sence as your theory. There are differant levels of wrong. Both of these were on about level 8

This has nothing to do with the Membership, It's all about you and your burning desire for anyone to challange your allmighty attitude. You quote yourself which I find halarious because you are so full of yourself. You have to have your own code printed into your signature line just so people have to decode that techno babble Bullchit. You are so full of yourself it's pathetic. You are a smart guy and won't argue with that but you slip up and not many people catch it because you talk over their head. I see right though you.
Sorry my strightforward, blunt and simple style threatens you so much you have to throw your techno babble BS style challange into the mix. Ask a real question, get a real answer. Thats my style, Deal with it.

John Doev1

Well being this topic I figure I'd throw this in here lol. I just scored a set of GT40P's today for $175

Joel5.0

You have 4 cylinders pulsing exhaust pressure/header, once each pulse gets timed at the header collector through primaries length/ID, overlap, collector shape and length, etc, etc....you want that refuse out of there ASAP. Now.... how does an increase of 44% in the cross section area of the exhaust (2.5" vs 3") will slow the flow down where it counts? Specially after receiving 3 additional pulses that will cause the leading mass of exhaust refuse to accelerate through the exhaust pipe?

The so called velocity is important at the header collector/extension location, and it is a pulse tuning exercise to impart a vacuum pulse to the other cylinder within that bank going through the overlap (aka scavenge). IOW.... Cyl. #3 exhaust pulse will help scavenge #1, #2 wil do #3, #4 will help #3 and #1 will aid #4 ...... once that scavenging pulse is used, exhaust flow (not velocity) takes the center stage.... you don't want that refuse hanging around that long. Besides, if you try to increase velocity using the typical Bernoulli techniques (narrowing a section of the exhaust), wouldn't it have an effect in back pressure?.... which is a for the Otto cycle engine?

Yep..... but that is not a 3" full exhaust system, or a 750 cfm Holley.

Legally?.... nobody. The point is that the open headers condition IS the condition to duplicate using a full closed/quieter exhaust system once the header collector/extension details are defined/tuned.

Word for word?..... nope, but why spend money in decreasing the exhaust flow capacity by 44%? Why not use that capacity and concentrate on improving the intake? Isn't that what "hot rodding" and performance building (including street setups) is all about? Can he still use that 3" ID exhaust with E7 heads over a 2.5" system?.... yep... so why decrease its flow? BTW.... decreasing flow = choking, it's not word play..... simply a synonym.

.....I can understand that......when a person has not done what is tried to be explained here, its obvious. I guess a 100% streetable setup on a 4 cylinder import with dual side draft Weber carburetors and full 2.5" exhaust system doesn't make sense either. When the only approach followed is the "big block" approach, that is understood..... why?, there's one of my quotes missing from that list..... "When all you have is a hammer, everything looks like a nail"

"Allmighty" attitude?..... moi?.... yep.... asking for explanations on topics that go against simple physics and Engine 101 concepts is an "allmighty" attitude. Members here don't have the right to UNDERSTAND the concepts, they only need to accept them because you say so, no explanations required, they are over their heads, so why provide them?...... and I am the one tagged with the "allmighty" attitude? A "straightforward, blunt and simple style" DOES NOT mean an automatic exception from providing explanations of whatever it is you are "suggesting"..... or is the use of "techno babble BS" an excuse to not engage in a little tech debate of the misinformation provided?

Yep.... other than FOCUSING on the discussion and questions, lets focus on the trivialities of a signature, since the tech inquiries are way above one person's abilities to explain them, let's draw the attention to something that is not related to the discussion at hand....... fine, here's a few I also use... "If you can't explain it simply, you don't understand it well enough. (Albert Einstein)" and "I can explain it for you, but I can't understand it for you. (90lxcoupe)"

Yep... I only come here to provide misinformation that will cause others to waste money downgrading components they already have, I don't do a thing to try to help fellow enthusiasts to solve problems with their rides either.... and God forbid I encourage any type of discussion regarding a specific topic, nobody has the right to understand why they should or shouldn't perform some modifications, and if you do, expect the "allmighty" tag?...... ..... BTW, since my signature is such a problem, would the one shown below be more appropriate?

Or would it be too ""straightforward, blunt and simple"? ......... it is a signature used by someone else.

Portmaster

Yeah OK, Keep beleiving half that crap. I guess engine builders like Joe Sherman, Bill Jenkins and Warren Johnson have it all wrong as well.

If you beleive that an totally unrestricted exhaust will out perform a slighty restricted one they why does an exhaust port flow better from .100-.600 lift with a 10 inch header pipe bolted to it than with nothing at all? Don't beleive it? chuck up an Edelbrock performer head on your flow bench and try it open, then with a 1-5/8 header tube, 1-3/4. That exhaust port will flow better with the 1-5/8 than anything else. It's the same reason that some heads flow better without some material removed when the obvious and logical thing would have been to remove the restriction. Chevy had a head W port that had a large bump (or Vane) in the exhaust ports we removed them in serch of more flow. We had to go back and weld the bumps back into the head to increase the flow. It goes to show that everything isnt as cut and dry as you would lead people to beleive.

Did you realize that exhaust movement can stall in an exhaust that has too large and create turbulance that can restrict flow over a properly sized exhaust? You have to keep the exhaust flow moving at maximum speed without stalling the air.

I don't ask people to beleive what I tell them but I do give them my proven opinion. No matter wheather you approve it or not my advice is proven over years of many many cars. You seem to be stuck on two or three cars and years of pratice tuning those few cars. I really do beleive you are a smart guy and I beleive as an auto technician you are prob very good. When it comes to airflow dynamics youre are a hack.

This conversation is over with you.

Joel5.0

Now I see........ the fact that you could have a setup that flows great on a flow bench @28" H2O does not mean the same flow characteristics will be the same, or linearly proportional @35", or 38" or 48"......... or does an engine work under a 28" pressure drop constantly? Specially with exhaust gases flowing @240+ ft./second?

And no, I do not lead people to believe things are cut and dry, reason why the results at the track or street have more validity over flow bench based data.... or do we race flow benches or dynos? BTW..... have you not read the specific mention regarding primaries ID, length, collector style design, ID, length, geometry and the same details for the extension that may be required? There's more into header tuning than primaries ID size.

And that will be caused by a 3" exhaust system over a 2.5" connected to a 302? So an engine revving @3000 - 5000 rpm, imparting 6000 - 10000 exhaust pulses/bank @240+ ft/sec each, will cause the flow to stall using a 3" full exhaust?

LOL...... a hack regarding airflow dynamics?...... the keyword is "DYNAMICS". You previously mentioned the need to keep the exhaust velocity as high as possible, to prevent it from stalling therefore, prevent the creation of turbulence...... did you know that flow turbulence is directly proportional to velocity? The higher the velocity, the higher the possibility of having turbulence in the flow? Don't believe it?......You might want to check what Mr. Osbourne Reynolds contributed towards that principle. Have I had to use his work previously, before working 100% on customer cars?...... do what you do best..... guess.

And no, I don't approve or disapprove anything here.... I simply try to help out understand, fix problems, and try to prevent others from falling into many misconceptions out there.

mjr46

GOOD JOB Joel

Joel5.0

.... for bringing this back to the top, but when new facts and data of other people setups one has had the chance to help contribute, as little as it might be...... it has to be shared to prevent misinformation out there. The following is the experience of a person working on a '97 Mustang SC V6 setup, simply to make something different. His plans were a topic of discussion elsewhere and the focus was..... you guessed it right, the exhaust system. Since his build plan is staggered in phases, he installed the headers + 3" full dual exhaust to the stock EFI N/A 3.8L..... obviously, no dyno numbers were intended to be generated from that build step, but look at his experience regarding the misconceptions we usually read about, with the full 3" exhaust and the headers intended for the SC 3.8L setup......

The above was a reply to my direct questions regarding losses in torque and overall street performance, the MPG was an addition he shared on his own.

Now..... the above is just a single data point using a 100% stock 3.8L V6 EFI N/A engine with an automatic transmission. It's nothing to derive generic conclusions or BS, but that "exception to the rules" (if you want to tag it like so) alone, should be more than enough evidence to support the so called "techno babble"..... Otherwise......

1. How is that interim setup performing better with such a reduction of the scavenging with stock V6 heads? .... or,
2. How is that interim setup performing better with such a theoretical reduction in the exhaust flow?

Portmaster

Don't beleive everything you read on the internet. Maybe you should start giving advice to some of the nations top engine builder and racers over the advantages of a properly sized header and exhaust. That stuff just eats you up doesn't it? I think I'll take the word of people Like Joe Shermam, Bill Jenkins, Warren Johnson, Scott Strope of Hooker Headers over some guy with a V6 who outran his brothers Focus. Good try XOXOXO