Large bore exhausts

Post by **alex_holden** » Mon Feb 18, 2008 1:29 pm

I don't think Fenchurch's standard exhaust has many miles left in it so I'm considering upgrading to a large-bore one at the same time as fitting a HIF38 carb, K&N air filter, and alloy inlet manifold (after upgrading the brakes, obviously). The engine is a 1098 with a mildly ported 12G202 unleaded head. I've already got all the inlet bits ready to go on.

Is it worth bothering with a larger exhaust? How much difference would it make to a very lightly improved 1098? A standard bore stainless two-piece exhaust would be much cheaper and if it's only going to add a few BHP at very high revs then I'll save my money.

Post by **chrisd87** » Mon Feb 18, 2008 3:31 pm

Most people seem to say that the exhaust is the main thing strangling the 1098 Minor engine, so I assume there are good benefits to be had especially if the rest of the 'breathing' has been improved.

I am in a similar position to you in that I have a 1098 with a 997 cooper cam and 12G295 head already on, and an HIF38 with K&N filter ready to go on as soon as I can get the last few little bits. This leaves me wondering about what to do with the exhaust.

Sadly it seems there isn't much choice for decent Minor exhausts - the Maniflow one is supposed to be good but is mild steel and very expensive, whereas the Falcon one... we won't go into that.

I'd also be interested if anyone has any figures or experience with the Maniflow system or any alternative ideas.

Post by **alex_holden** » Mon Feb 18, 2008 3:47 pm

I've been looking at the stainless three-part system the Birmingham MMC sells. I'm a bit confused about the choice of three different downpipes. It looks like the Marina downpipe is the cheapest option if you can find a Marina exhaust manifold to attach it to.

Post by **Alec** » Mon Feb 18, 2008 5:33 pm

Hello Alex,

I got a long centre branch system, one silencer, from the Birmingham MMC in stainless at a very good price. The car is now a 1275 and it seems to run fine on that. I don't remember the bore size but guess at 1 1\2". The only problem is that it cracked at the last Y of the manifold and I had to weld and reinforce it.

I think a good manifold is more important than the bore size of the whole system.

Alec

Post by **alex_holden** » Mon Feb 18, 2008 5:40 pm

Alec wrote:I think a good manifold is more important than the bore size of the whole system.

What are the differences between the various exhaust manifolds? The LCB manifold/downpipe from Birmingham MMC is a lot more expensive than the downpipe that mates to a Marina manifold.

Post by **Peetee** » Mon Feb 18, 2008 5:46 pm

From what I understand, and have purchased, the Birmingham exhaust system is manufactured by Falcon. the three different downpipes are to match the manifold options.
1. Single downpipe - to mate to a Marina cast iron manifold (visually similar to Minor)
2. Twin downpipe - to mate to a Ital twin outlet cast manifold
3. LCB. three-into-one pipe stainless system running directly off the cylinder head
No's 1 to 3 also reflect the order of increase in bhp attainable.
Any of these should fit the dedicated two part/box exhaust.

I know of more than one person who has had repeted problems with cracking of the 3-1 manifold and I had to cut both sections of the exhaust to length.

Maniflow have an excellent reputation in the race community and thier systems are sized to reflect the engine; either 1098 or 1275. However they are mild steel throughout and I have seen a well rotted one attatched to a healthy A+ 1275 so you can draw your own conclusions as to longevity.

For what it's worth I have run a tuned 948 on a standard bore stainless system. It was quicker than a 1098 at any revs but didn't feel strangled at all.

Post by **alex_holden** » Mon Feb 18, 2008 5:49 pm

Thanks, that's useful information.

Post by **chrisd87** » Mon Feb 18, 2008 6:17 pm

I think Pyoor_Kate who uses (or used?) this forum had a Falcon system and had no end of trouble with it. The ones I've seen also stick out miles from the back of the car.

Post by **Alec** » Mon Feb 18, 2008 6:17 pm

Alex,

I bought the whole system as one, and it was not expensive. As such, I accepted the weakness and sorted it myself. I appreciate that others may not have the facilities I have and such a course of action is not an option.

I see now that they do not sell the system I bought but a two silencer one. If you have the facilities you could omit the centre silencer and make up a straight(ish) section of pipe?

Alec

Post by **IslipMinor** » Mon Feb 18, 2008 7:07 pm

For performance the best manifold is an LCB. Maniflow do two bore sizes, the smaller (and cheaper) one should be ideal for for your engine spec.

I bought a secondhand Maniflow LCB 10 years ago to tide me over until I sourced a new one - it's still going strong!! The only change I made was to fit a new, larger bore end after the join, so that it would mate up to the 2" system needed for the engine spec.

The rest of the system is made from Jetex modules from Demon Tweeks, and the only part of the system to rot has been the over axle piece - quite easily replaceable.

I understand the benefits of stainless steel, but have often heard criticism of the manufacturing quality.

Post by **alex_holden** » Mon Feb 18, 2008 7:10 pm

Probably a daft question, but what does LCB stand for?

Post by **zippy500** » Mon Feb 18, 2008 7:21 pm

Long Centre Branch ??

Post by **bigginger** » Mon Feb 18, 2008 7:23 pm

Long centre branch, a bit bizzarely. I've been trying to dig out my Marina manifold to post a pic of it and the LCB I have, but I can't seem to find it. I can look some more if you're interested in seeing one

a

Post by **alex_holden** » Mon Feb 18, 2008 7:28 pm

bigginger wrote:Long centre branch, a bit bizzarely. I've been trying to dig out my Marina manifold to post a pic of it and the LCB I have, but I can't seem to find it. I can look some more if you're interested in seeing one
a

Yes, that would be good. Also interested in seeing what the Ital/MG Metro manifold looks like.

Post by **bigginger** » Mon Feb 18, 2008 7:32 pm

Oh lawks, I've got one of those too, but a LOT more hidden away - back of the garage somewhere. I'll see if it turns up

a

Post by **Mogwai** » Mon Feb 18, 2008 7:37 pm

Ive got the maniflow LCB (long center branch) system on my 1275 minor for about 7 years had no problems with it but it is geting a bit crispy at the rear now. If you do fit a bigger exhaust to a 1098 dont go too big as this can have a negative affect low end torque . i fitted my big system temporarily to a standard 948 just to get it running a few years ago it didnt run well with it on

Post by **Orkney** » Mon Feb 18, 2008 7:38 pm

Can / will make a lot of difference if combined with other things - sat here on the bookshelf is the Viz book (thats tuning the A series not the expensive comic ;-) ) want it ?

Post by **alex_holden** » Mon Feb 18, 2008 7:45 pm

I've got the Vizard book. I'll take another look at the exhaust section...

Post by **IslipMinor** » Mon Feb 18, 2008 7:49 pm

Alex,

I used Vizard to size the system we have - seems to have worked out pretty well.

Post by **Orkney** » Mon Feb 18, 2008 7:55 pm

In the example builds bout 3/4 way through there ar some interesting dyno tests & graphs from 'bolt on's ' its really intersting reading !