making an exhaust

[Clip]

hey guys,

Got a bit of a break coming up when the car will be on jackstands, and I was going to look at the possibility of making an exhaust for the GE.

So far, I've decided to run 2.5" aluminized pipe and powdercoat it after I finish. I'll either be using the stock cat or a high flow, but no test pipe. I'm going to have the same basic resonator/muffler setup, with maybe a few changes. That's about it.

Questions:

How restrictive is the downpipe from the manifold to the cat?

Can I cut off the downpipe flange if I'm going to make a new one and use that as a starting point?

Does anyone have a recommendation of mufflers/resonators to avoid?

I've made four exhausts before using continuous welds on the joints, but is it better to use a technique like this?

I know most of this is going to be my pure taste, but I'm just hoping to avoid buying a dud to start off with and having to change it out later.

Thanks!

 

[gaboonviper85]

The stock mani and y pipe is actually pretty damn good! Toyota did a great job at squeezing all the power they could from the na 7m!!!

 

[Cz.]

Questions:

Can I cut off the downpipe flange if I'm going to make a new one and use that as a starting point?

Does anyone have a recommendation of mufflers/resonators to avoid?

Thanks!

I would just go 3", even on an NA you'll have better top end and it doesn't really affect the lower end.

Isn't the downpipe cast? I'm not a welder but I was under the impression that you can't weld casted metal?

I'd avoid cheap ebay mufflers/resonators. If you get a good quality one you can really help the tone of the exhuast. It really depends on how much you care about the noise.

 

[gaboonviper85]

I would just go 3", even on an NA you'll have better top end and it doesn't really affect the lower end.

Isn't the downpipe cast? I'm not a welder but I was under the impression that you can't weld casted metal?

I'd avoid cheap ebay mufflers/resonators. If you get a good quality one you can really help the tone of the exhuast. It really depends on how much you care about the noise.

You obviously don't know the theroy behind exhaust systems:nono:

 

[Cz.]

I do know that I saw a comparison to the same NA car being dynoed with a 2.5" and 3" and it was better off with the 3" for pretty much the entire powerband.

I guess since I don't know the elitist "theory" behind it I must not know what the fuck I'm talking about though.

 

[gaboonviper85]

Proof or it didn't happen!

You're only going to flow as much exhaust as the most restrictive point will flow...putting 3" system on a stock exhaust manifold will not change flow much as you're only going to flow what that mani flows! Now with a nice set of headers you may see a 5-10 hp increase but is that worth $$$??? A stock 7m ge does not respond much at all to bolt on's and that HAS been proven by many....not to mention you'll need to match fueling and an intake to said exhaust!

3" is to big for our 3liter as you'll loose exhaust velocity...with an engine in stock form!

So show me the dyno sheets...till then I refuse to believe it made more power...dyno comparisons must be on the same day within close proximity unless it made outragous changes that can't be argued threw air temp and humidity etc.

 

[Cz.]

Sadly, I do not have the dyno sheets because I did not perform the test.
The thread was originally made on SF with the dyno sheets posted there. Since I don't particularly care about NA performance I didn't bother saving the images, however it did convince me that the 3" is the way to go regardless.

You obviously have no solid proof ('theory' is not proof of anything) that 3" is a worse choice so I don't even understand why you're arguing about this. Do you honestly think that I posted my opinion because I wanted to mislead the OP? Regardless of what he does it's still going to be a slow NA.

 

[Poodles]

IIRC that GE was far from stock...

Anyway, back to the original questions.

The stock Y pipe is tubular IIRC and not cast, so you could remake it if you want to. Also, in that pic that' looks like a flare was used and the pipe was slipped inside, not a bad way to do it as it allows you to move parts around a bit and then weld, but it will use more pipe and increase weight. You also don't need to weld joints like that if you use one of the sweet clamps they make for em.

 

[akito]

I have ceremic headers if you want, for 100 its yours. its cut a little bit after the y pipe. Also have a high flow 2.5 cat here too. I had an NA, if i was to make my own exhaust, i would go with 2.75. Nothing loud, just nice and to have fun in the car. Too bad i joined the gte force

 

[Mastapip]

Gaboon

I've known people in NA cars to say the same thing that CZ is saying. Granted they weren't talking about 7m's, but I've got a friend with a 240KA who switched from 2.5 to 3" and said it performed better overall.

But from most accounts on here, you're right... People suggest that the NA 7M doesn't really benefit much from exhaust, at least not like the turbo...

Judging by a diagram of the NA downpipe, it looks like it should flow pretty well. If I were the TS though, I'd make a catback without a resonator.

 

[gaboonviper85]

Gaboon

I've known people in NA cars to say the same thing that CZ is saying. Granted they weren't talking about 7m's, but I've got a friend with a 240KA who switched from 2.5 to 3" and said it performed better overall.

But from most accounts on here, you're right... People suggest that the NA 7M doesn't really benefit much from exhaust, at least not like the turbo...

Judging by a diagram of the NA downpipe, it looks like it should flow pretty well. If I were the TS though, I'd make a catback without a resonator.

hense why I was very specific on the "7mge in stock form".

 

[Clip]

I have ceremic headers if you want, for 100 its yours. its cut a little bit after the y pipe. Also have a high flow 2.5 cat here too. I had an NA, if i was to make my own exhaust, i would go with 2.75. Nothing loud, just nice and to have fun in the car. Too bad i joined the gte force

do you have any pics of the headers and cat? i might just be interested

poodles, i was definitely thinking about the clamp option too. mainly with that pic i was wondering if it was better to spot weld all the way around the joint or run a continuous bead. i suppose spot welds would have less of a chance to burn through the pipe if i was welding butt joints.

as for the diameter, i'd probably stick with the 2.5" for cost and simplicity. i know my car's always going to be fat and slow, so the possibility of gaining 1-2 extra hp doesn't worry me

 

[Clip]

nobody has any input on the weld technique? spot vs continuous?

 

[adampecush]

doesn't really matter as long as you don't burn through the pipe (which is fairly easy to do with a mig)

I'd personally go with the slip-fit joints - it will make welding much easier, not to mention improving flow due to avoiding the protrusion of the weld root into the pipe.

tack weld in 3 places, then weld between the tacks.

 

[CRE]

The biggest difference you'll really feel are just from changing the resonator and muffler out for unbaffled types. Have you found a resonator and muffler yet?

 

[Clip]

not yet, still looking. suggestions?

 

[Poodles]

Think the weld has more to do with the type of welder you have...

 

[Clip]

that weld in the first post was done with a mig setup. i'd rather use tig but have no access to equipment.