Further ramblings on exaust choices.

[ChrisGB]

Hi to All

I have been trying to decide on an exhaust for the '2. A few things to consider were taken into account. Off the shelf systems that qualified were as follows:

Remus / TTE - Pros: nice finish and quiet. Cons: Heavy and twin exit.
Magnex - Pros: Known power gains and quiet. Cons: Heavy, twin exit, silly tailpipes.
SP - Pros: known power gains. Cons: Cost, twin exit.
Fujitsubo Legalis-R - Pros: Light, quiet, known power gain. Cons: Cost once postage considered.
Che - Pros: Cost, known and respected supplier, lighter (just) than stock. Cons: Only butt dyno results available at the moment, small twin chamber silencer may be noisy.

Custom builders:

Blueflame - Pros: Cost, can make single exit system. Cons: Cant make required box size and shape for my requirements (std size box, absorption silencer) as their available tooling wont permit it.

Viper Racing Systems - Pros: Cost, Can make to my design, local. Cons: Will only work in 2mm wall sheet and tube, so my design becomes way too heavy.

H & S - Pros: Local, can make to my design. Cons: Locally, their systems are known to be noisy (may be dampening medium), cost.

A self designed system in Jetex 2.5" silencers - Pros, can get silencers easily, low weight. Cons: Cant find anyone to do the pipework ( the required bends in 2.5" puts off most fabricators).

The thought processes:

Magnex looks good from a power point of view. Read somewhere that it gave +5bhp and is quiet. Construction is multi cell (not straight through). Would be a winner but for two things: Weight at 15.5Kg and those two 4" exits are just too chavvy.

TTE / Remus not known to give power improvement. System weighs a little more than stock. Sound and fit is known to be OK. Looks nice if you like twin exit.

SP has known power gains but is twin exit and pricey. Dont know about sound.

Fujitsubo looks good until you factor in shipping from Japanparts when it suddenly looks very expensive.

Che is sort of unknown quantity being relatively new. One running on here and a couple on SC. All positive about sound (have also heard sound clips) and all reckon good power, but no dyno. Price is very low indeed. Multi chambered design.

Of the custom builders, if I go for a staight through design, I need two runs of absorption silencing (across the back of the car) to be quiet enough. Only companys that can do this for me are H & S and Viper Racing Systems. As above, both have cons that take them off the shortlist.

Magnex produces known good power and is a cell design (not straight through). This got me thinking. Back pressure is a know enemy of power generally, but straight through designs dont produce any. A cell design will generally not flow as freely as a straight through design, however, what it does do it proporgate a stronger return pulse than a straight through design.

As we know that fully de - catting will produce too little back pressure resulting in the need to adjust valve timing. Could it be that the engine requires a strong return pulse, rather than back pressure, to work well (thinking about force back wave prior to e-valve closing)? This could account for the advantage of the Magnex system.

Now I dont like the look or the weight of the Magnex system, but the Che is also a multi cell design. Given the cost ($420 delivered to my door), it has got to be worth a punt. So I just ordered one  s:D s:D  Only possible downside is big exit tip, but I have a neat idea for that if it looks too big.

If it works out, then I have a low cost upgrade. If it does not, I will have the stock system to measure up to make my own very light weight straight through silencer box. Thinking is stainless end cap, and pipework, rest in ally.

Will report fitting and dyno results when the Che exhaust goes on.

Thanks to those who offered a stock system for me to measure up. Wont be needing it now.

Chris

PS ETA on Che exhaust manifolds is now early March.

[ChrisGB]

Ordered Thurday 8-2-07, now standing in my hallway 9:37 Monday 12-2-07. That is what I call service!

Looks nice, welding is visually very good. Weight is 19lbs +/- 4oz. The bends going into and out of the box are more gradual than the stock box. I found some photos of a cutaway of the stock box. No wonder the stock MR2 sounds like a sewing machine.

Just got to get it fitted and dynod now.

Chris