[azopelnut]

The typical exhaust upgrade (as I understand it) for our Opels is:
1) 2" pipe at the point head pipe goes from two pipes to one (approximately under the passenger side floorpan)
2) suitable muffler/resonator near that point
3) 2 1/2" bent pipe going over the rear axle
4) 2" into a rear muffler and out into a tail pipe


I recently asked the numbskulls at Midas to do this and when i went to pick up my Ascona the guy said. "Oh we used 2 1/4" all the way it won't make any difference"..........is he correct?????

 

[RallyBob]

Let's see, assuming a .060" wall thickness of the exhaust tubing, a 2" pipe has an internal area of 2.7759 sq. inches. A 2.25" pipe has an area of 3.5632", which is roughly 28.3% larger than the 2" pipe....

Yea, it makes a difference.

The good news is you'll have better top-end and mid-top power. The bad news is the off idle and low rpm performance will suffer, unless you have high compression (over 10.5:1) or a larger engine (2.2 or bigger).

Bob

 

[Chuck Luther]

then into side pipes???

if I have a sprint exhaust manifold - into the stock head pipe, then from the two pipes on the head pipe, run them each to their seperate side pipe?? which would be 2 inch pipes? I've been told this is workable...

would that give me some extra oomph?

 

[RallyBob]

if I have a sprint exhaust manifold - into the stock head pipe, then from the two pipes on the head pipe, run them each to their seperate side pipe?? which would be 2 inch pipes? I've been told this is workable...

would that give me some extra oomph?

Actually you will lose power by keeping the pipes split. A single merged pipe from the twin upper headpipe tubes will have better velocity, but more importantly, the exhaust pulses will help scavenge the cylinders correctly. Splitting the headpipe looks cool, but sounds kinda funny and always loses power and torque. Seen it before, tried it before, hated it!

Bob

 

[azopelnut]

exhaust upgrade

Thanks for the info as always Bob. I am sorry you are not coming out to the OMC picnic. I was looking forward to hoisting a few adult beverages with you and Bill Hoffman at a nearby pub.(Its the equivalent of reading this forum for week but with much more humor)
BTW
Susan says hi!

 

[soybean]

Quote from Azopelnut "The typical exhaust upgrade (as I understand it) for our Opels is:
1) 2" pipe at the point head pipe goes from two pipes to one (approximately under the passenger side floorpan)
2) suitable muffler/resonator near that point
3) 2 1/2" bent pipe going over the rear axle
4) 2" into a rear muffler and out into a tail pipe"

Bob, my question is would it be better to run it like Azopelnut said in item 1, or run from the headpipe with a whole new 2" pipe and new flange bolted to a sprint exhaust?
The other is why "2 1/2" bent pipe going over the rear axle" instead of keeping it 2" all the way to the rear? Thanks, Jarrell

 

[Excelsior]

That is a good question. I went with a 2" all the way back myself.

 

[tekenaar]

Why 2.5" over-axle pipe

Quote from Azopelnut "The typical exhaust upgrade (as I understand it) for our Opels is:
1) 2" pipe at the point head pipe goes from two pipes to one (approximately under the passenger side floorpan)
2) suitable muffler/resonator near that point
3) 2 1/2" bent pipe going over the rear axle
4) 2" into a rear muffler and out into a tail pipe"

Bob, my question is would it be better to run it like Azopelnut said in item 1, or run from the headpipe with a whole new 2" pipe and new flange bolted to a sprint exhaust?
The other is why "2 1/2" bent pipe going over the rear axle" instead of keeping it 2" all the way to the rear? Thanks, Jarrell

YES!

Because the ID of the "over-axle" pipe is somewhat restricted by pipe bending machines, however using 2.25" pipe works equally as well here.

An over-axle 2" pipe fabricated of mandrel bent sections would be the ideal solution, but requires a lot more work. Depends on how anal you are about little details, I guess. NOT that that's a BAD thing!

 

[Chuck Luther]

so if you really love the look of side pipes (like the old vettes)

then the best bet is to have one for looks and the other that really functions... if you are looking to keep as much power as possible?

???