Exhaust To Make.....aargh!

[Guest woolly]

daz on a 2in to 2 type which i understand is better you need advice as to weather to join runners 2&4 and 1&3 maybe not as you have 1&2 3&4 don't know the answer but could make a difference to the scavenging effect.

[Guest The Modfather]

Hi Chris.

As the firing order is 1-3-4-2, there is no way I can do a 4-2-1 system without two adjacent pipes firing one after the other entering the same down tube. With what I have drawn, 1 & 3 are on seperate down tubes, 2 & 4 are on seperate tubes, but 4 follows 3 immediately.

If I made 1 and 3 join together, and 2 & 4 join together, then the problem is on both down tubes. If I made 1 & 4 together, and 2 & 3 together, the problem is the same.

 

Hang on, that isn't right........... 1 & 4 together, and 2 & 3 together would work! That would make alternate pipes firing thus allowing each pipe to clear before being followed immediately. But, (there's always a but) trying to get each pipe the same length would be harder.

 

I feel more confident in myself having drawn a plan rather than trying to see it in my mind's eye. But now I think I need to re-draw it. Anyone out there that knows a bit about building exhausts can clarify any point raised, or anything I need to know that hasn't been raised?

 

Thanks

[Guest The Modfather]

I found this, and it is really interesting (boring for some I know) but informative!

 

http://www.custom-car.us/exhaust/default.aspx

[Longboarder]

Join 1 & 4 and 2 & 3. Ideally about 17 inch x 1.75 primaries. Then 11 inch x 2 or 2.25 secondaries to the next collector and 2.5 inch system.

(Caught me mid edit.)

 

Nigel

[Guest The Modfather]

Hi Nigel.

 

Then I guess it'll be 1 & 4 and 2 & 3 then! From your given lengths, the final 2 into 1 collector will probably be outside the car, but that isn't a problem.

 

Okay, back to the drawing board

[Longboarder]

I had a long chat to the guy who is OJZ exhausts at Stoneleigh last year. He said there is some tolerance in getting equal lengths to the primaries, slight crimping of the pipes on bends, bend radii and lengths of primaries and secondaries without doing much more than moving the power band up or down the rev range. The most important points in his view were port matching to the head, never allow a step narrower, slightly wider may even be of benefit and secondly the design of the collectors. Best to have two 15 ish degree bends, cut parallel, weld together and amputate the point to the right diameter.

 

Nigel

[Guest The Modfather]

The problem with the Ashley exhaust I show in my first post, is that the secondaries are 2", but my end can has 1.75" bore pipe entering it. You state I shouldn't go down in size, but will 1/4" make that much difference?

From reading the info on the site I post just above this, a 2" secondary is probably too big and won't help required back pressure, but if i do go down to 1.75" pipe to match the end can, perhaps this would be better for the engine?

 

Is it really this involved? Will the difference I propose be that detrimental to the flow? As even the length and radius of any bends can effect the flow, I bow down to superior knowledge, and you Nigel, are very knowlegable!

[Longboarder]

The Ashley exhaust kit shows 1.75" primaries, 2" secondaries and 2.25" or 2.5" system. Those dimensions all seem fair enough. If you are saying your exhaust can has an internal diameter of 1.75, same as the primaries then I think it's too small. 2.25" minimum.

 

The original Robinhood zetec exhaust which I had started with had 1.5" primaries and then 2" system as it was a four into one. I thought it was too small for a 2L zetec and strangled the engine to the tune of about 20 bhp. My engine spec of ported skimmed head, 285 cams, jenveys/omex, rolling roaded at 170 flywheel when it should have been close to 200. With a good exhaust I think it would have been close but it never was.

 

The ST is a lunatic beast and has a 4:1 with 1.75 primaries and 2.5" system. It ran about the same as the silvertop on the old exhaust. The new exhaust from Martin Keenan transformed it.

 

Nigel

 

Re-reading your post it sounds like you are doing 1.75" primaries, 2" secondaries and 1.75 system exhaust can. Definite no.

[Guest The Modfather]

Ummm, it isn't a problem as I'll just have to look for a 2.25 can, maybe a bike can? LOL, I just threw out a bike can, D'OH!

[agent_zed]

well.... if you are making your own headers then why not finish the job and make the exhaust can.

its what i plan to do.

all you need to do is find some nice rolled edge Stainless end caps, which is a case of searching the pots and pans section until you find a nicely shaped pair of pots.

a sheet of stainless that you'll roll and weld along the seam.

a pipe in welded to the end cap and a pipe out welded on the other cap.

a length of perforated tube that will slip over the bits of tube you've left sticking inside the endcaps to locate it

and some glass fibre packing.

 

then just fix the end cap into the tube of stainless and bolt round with button hex bolts (or weld if you are happy after welding the headers). slide the perforated tube in and pack with glass fibre then put the other end cap on and secure again. job done. Ive seen the end caps bolted on on a bike exhaust so i assume its do-able although may need some sealant of somesort if it lets exhaust through. I'll prob try and weld it when i do it although maybe only one end so i can re-pack.

 

You can then make it as long/wide as you want and repack it whenever you need too.

 

I think it was Longboarder who said somewhere near 7inch O/d would be best.

 

This is just my thoughts so feel free to correct me or add something if i've missed anything.

[Guest The Modfather]

Hi Zed.

 

I'm afraid, for me, that making a can is too much hassle, especially as a large Suzuki TL1000 or GSXR can is easily available on Ebay for a tenner! I have my eye on a pair of TL's in VGC for £9.99! As I have the zetec, I need a left handed can so that the hanger is on the correct side. Most Kawasaki cans can be used on either side as they utilise a hanger band that can be turned either left or right. Most Honda's and smaller single canned Suzuki's are right siders, and they have welded brackets on the can, which when used on the left side mean that the bracket will stand out and look ugly.

TL cans are good because the engine is a 2 cylinder 1000cc, which means large bore pipes, and hopefully will give me the stated 2.25 - 2.5" bore I require, and they bolt to a welded plate at the end of the pipe.

I will let you know the outcome.

[Longboarder]

Measured my exhaust this morning and it's 1.75" headers with 2.25" ID can. Not 2.5" as I wrote last night.

 

Nigel

[Guest mower man]

Daz bite the bullet and get in touch with Martin Keenan and get one of his repackable boxes you wont regret it . By the way noticed on your later photos that your tie bars are hope fully at the temp fit stage or you may have clearance probs mower man mick

[Guest The Modfather]

By the way noticed on your later photos that your tie bars are hope fully at the temp fit stage or you may have clearance probs mower man mick

 

I'm gonna stick a skateboard wheel on the tie bars so that when I turn full lock the tyre will rub on the wheel and not cause any damage.

[Guest The Modfather]

I just ordered the exhaust shown in my first post, with a 2.25" tail. I have found a suitable bike can with the same size opening as well!

Sorted.

Thanks to everyone for their input, especially Nigel who measured his pipes, I trust your advice mate