I having been speaking to a friend who is going to fabricate me a stainless steel exhaust, to fit my Toyota 4AGE engine. He has asked me a few questions which i promised to find out;

1). How important is it that the pipes from the manifold are exactly the same length? what sort of power loss will result from unequal lengths?

2) What is the optimum design 4-1 or 4-2-1?

3) What is the optimum wall thickness for the stainless?

4) Any suggestions as to bore sizes for the 4 cylinder pipes and for the larger single pipe? Can i just measure the standard Corolla exhaust?

5) silencers - how many? what type? and where from?

5) Is there anything specific to bear in mind for the SVA, while making an exhaust? i.e. noise levels (are thes easily obtained?), tail pipe angles etc.

Any help or advice greatly appreciated. Sorry about all the questions.

Cheers

1) if possible it is desirable. if you imaging the pulses of gas traveling down the pipe, if the lengths are uneven they will not merge at the junction well. Power loss might be 5 or 10 bhp at a guess (total guess)

2) probably 4-1.

3 no idea

4) bigger the better to a certain extent. helps flow rate but too big might be bad too, IIRC.

5) as few as possible to meet any noise requirements. silencers impede the flow of gas so they need to be good.

5) (why two 5s?!) if you fail on noise, just clamp on a long extention with another silencer in it. This will move the exit (and hence the meter) further from the engine. angle it down so it cant aim straight at the noise meter.

HTH, Joel.

Hi Albertz,

1&2. Are you after every last drop of power? If so, yes.
If not, then what you make will probably be better than the stock item anyway.

3&4. I use 1.5mm wall, 2" dia pipe & 1.5" dia for the primarys.
1mm for the can ends. 0.7mm for the can body.

5. 4-2-1 or 4-1 = 1 can

er.... 5 again. I roll the edge of the can end so there are no sharp edges and exit bend must have a rolled edge too.
I use a ring of 6mm dia rod welded to the end.

Hope some of this is of help.

Paul G

Thanks for the information, that is pretty much the main items covered. Sorry about the two No.5s!

Cheers

Just to add my two penn'orth, I used to have a Kawasaki GT550, fitted when I bought it with a 4-1 exhaust. It was always a bit flat in the mid range revs but picked up and revved to the redline above about 6-7000 rpm. After a numbty in a Fiesta knocked me off I used some of the insurance money to buy a 4-2 system which the bike comes with as standard and it transformed the engine. THere wasn't the sudden rush of peak power but the midrange flat band was gone, torque aplenty was for the asking. THe top end seemed a bit breathless but it mayt have just been that with the way it was with the power suddenly coming in a high revs was very noticeable, whereas with more mid range torque it was less so.

If you can find / get hold of the article Vizard wrote for an OZ mag on exhaust design it will explain everything you need to know.

It seems to help me achieve nearly 90 lb ft torque per litre from a road engine.

John

Doesn't work that link

The site worked for me last night when I did a search for it, but not working now.

The downloads are big but worth it.

John