Exhaust Design

Hi!

I want to put a new exhaust on my second gen and i am confused.
On the Racingbeat webpage as well as in my book I am reading about how important primary tube length and the collector is.
But if you check the racing beat products for race applications they seem to offer a system without a collector.
Can anyone shed some light on this?

Check out ISC Racing and see if Mike has any systems left or if he will make some more. There is a thread with pics on Rx7club.com in the race section on this system. RB is not what you need.

Agreed, do not go with anything RB.
It all depends on how much porting has been done, more porting needs shorter primaries and a bigger collector.

if mike at isc has any exhaust systems left , that is a good choice. if not get up with steve eckerich , his system is really good , he also knows these rx-7s very well . we run/use mike's system . ralph

I just ordered a collector from Burns stainless that works with the RB racing header. I used the RB 3" presilencer and 3"muffler. Not sure of the WHP results but the car is much quieter. I shipped Burns Stainless the exhaust flange from RB and Burns made the collector to go to a 3" singe output. Beautiful piece of work. Speak to Vince at Burns.

My Mazdaspeed/ISC header, ISC mid section, 3" mandrel pipe and lava rock filled Dynomax SS muffler will be going up for sale in the next 4-6 weeks for those looking and can wait. Price and whether I will seperate not determined yet.

i have one more option i have been developing(design 14years ago been on test cars for 4 years)a expansion chamber exhaust for 3inch systems(this goes way beyond what isc calls and expansion chamber)very significant gains both on ported and unported motors fit both 1st and 2nd gen cars(minor floor clearancing need to aid ground clearance)you must be able to tune your fuel mixture to use this i.e. be able to jet a carb or have a programable efi system.the ability to adjust timing curve and split increases the gains.example 1st gen ita car converted to e-prod stock untouch non ported 12 48 weber my exhaust 140whp secgen 90spec motor 191whp(the timing split was not mapped as i wanted car can make 5-7 more)on average test cars gained 7-11% more at peak but more significantly power on average met or exceeded the previous peak 1000rpm earlier in the power band and instead of dropping off after 8500-9000rpm continued to increase till we stop the dyno pulls in some cars close to 11k!!the power gains on some ep motor cars(street ports)in the 9500-11k(on conventional exhaust power is dropping off)have been as hi as 25-30whp as the curve plateaus(one car was 199whp@7200 204@10400 and still rising when we stop the test(unbalance or clearanced motor)@ the track said it pulled past 11k wanted to go higher!if you need more info drop me a line @ [email protected] remember if you do not have the ability to tune you fuel properly this is not a part for you it causes a dramatic shift in fuel air ratios and will result in damage to your motor if run on a untuned set up!!!! we have had to make fuel curves as much as 5 points richer i.e base line tuned to 13.7 add pipe now 16.9 peak power after tuning 11.2-11.3 if motor is not tuned it will not last more that 3-5 laps at race speed

That 12A number could be attributed to the Weber alone though.... :(