Dump Pipes

[M E S O G L E A]

I have one of those JJR split/dumps on my ECR33. I concur on the fitment issue. I had to use a pipe bender to alter the straight portion to clear the underside of the car. They can also be incredibly annoying to install because of the design, the bolts/studs are hard to reach due to the joining of the pipes to the flange.

While it improved power and decreased spool time, the wastegate swing valve hits the flange at max opening. My tuner says it causes boost creep because the wastegate pipe is too small. It works but could be better.

these are supposed to be one of the best http://www.moonface.co.jp/mfr/ex/exhaust/exchamber-pro.htm

[1SLP80]

Why do manufacturers like tomi make the bellmouth style aposed to a split dump if they are not a better design?

I just brought a JJR bellmouth front/dump pipe........ Which i must say, looks to be quite poor quality.

I asked around and most people said that the bellmouth was a better design than the split dump.

[HCR32R]

Why do manufacturers like tomi make the bellmouth style aposed to a split dump if they are not a better design?

I just brought a JJR bellmouth front/dump pipe........ Which i must say, looks to be quite poor quality.

I asked around and most people said that the bellmouth was a better design than the split dump.

Hi, i'm just about to buy this dump/front pipe from JJR and just wondering about the fitment on the product? bolt straight on? any mod need to be done to make it fit perfect? what gasket did u use?

how about the X-Force one? any info or feedback guys?

Thanks

[zebra]

I have an X-force one in mild steel...Fits fine, but its a pain in the ass to get 2 of the bolts in

[saliya]

Why do manufacturers like tomi make the bellmouth style aposed to a split dump if they are not a better design?

I just brought a JJR bellmouth front/dump pipe........ Which i must say, looks to be quite poor quality.

I asked around and most people said that the bellmouth was a better design than the split dump.

Hey,

split-dump is 'apparently' inherently better because the gas coming off the exhaust wheel is flowing in radically

different directions than the gas bypassing the wheel. The split designs are designed to minimize the impact

that the merge has by merging flow after it's had some time to laminarize itself.

Most 'bolt-on' pipes that try to do this are hamstrung because they have a very limited distance

(10-15cm or so) to do it before the merge (in order to bolt on to the existing system).

Most folks in the know recommend a much larger distance (30cm+) before wg/turbine merge to gain appreciable benefit.

So if you want to go down the split-dump path on an internal-gate design:

a) ensure that the wastegate path is as closed to sealed-off as possible

b) ensure that the split pipes are longer than 30cm.

Hope this helps,

Saliya

[TR34GT-000]

SAU Members,

I may as well put my 2 cents worth in too. I apologize now in advance.

Call Best Mufflers in NSW and they'll tell you one or the other (bellmouth or split) is the better dump pipe for turbo applications.

Call Hi Tech Mufflers and they'll tell you something else.

Call the manufacturers of the dump pipes and it gets more confusing. (not that they aren't very very helpfull)

It seems that where performance gains are quoted, they're usually overstated.

It seems that even with long time experience in this field, opinions vary.

A technical understanding of exhaust gas flows from the turbo, in relation to computer modelling or the monitoring of actual results between various products and manufacturers would be a great thing, and maybe even settle a few arguments.

(Maybe someone like Hi Performance Imports or Zoom magazines can run a tech article on this issue)

Most of us understand the split gases non-turbulent separation and flow into a split system can aid turbo response, but there seem to be times when the differences in gains are insignificant.

There is no doubt though, that theres better response and a few more kilowatts on offer by going with either a better aftermarket bellmouth (say X-Force) or split system (say BOS Importing).

In my humble opinion, the Aussie manufacture is much better.

I can attest to the gains on the last two R33's I've owned and modified, and now on the R34 GTT, that at least the BOS Importing unit is simply much better than the OEM bellmouth.

Research what you want to purchase thoroughly. Compare the shape, angles, connection point of split pipe, design, flange arrangement, bolt hole position and various connections.

You will find they are pretty much different.

(I have no interest in promoting BOS Importing by the way)

Hope this helps.

Regards

Jim (TR34GT-000 & TR34GT)