dj55b

iTrader: (2)

weather up here hasn't been the greatest, but the car did fire up for a short time and then flooded again. It will be my priority in the next coupld of weekends if the weather permits ... I should have a couple of dyno's by maythe 5 th

the_duke313

23racer, care to explain ur exhaust at all... or at leas hint if its to secret?

sc0rp7

iTrader: (3)

If I had to guess... I would be willing to bet its something similar to this, the main difference being that you have to vary then length of piping before the collector per your port size, since this one is based on stock ports...

http://iscracing.net/2nd_Gen_Parts.htm

That setup is also based on peak hp if im not mistaken... *hint* the longer the runnners the lower the powerband, just like on an intake setup.

Also, remember there is a *short* primary design and a *long* primary design depending on what exhaust wave you are trying to tune.

- Chris

23Racer

I have had 3 different exhausts on the car. I have run a short collector system, a mid length and a long system. I ended up running a system modeled after the Aussie IPRA systems. I spoke to Rohan Ambrose at last years PRI Show in Orlando and explained what I was planning on doing. It was to modeled after the IPRA 4 port ITB setup and I needed an exhaust setup.

He was very reluctant to give me any direct information, but told me to model my system after what they run "Down Under". I pursued this information on another website and I ended up with an extended 2" primary system gathered together under the rear subframe using a special type of venturi collector with a certain angle to the merge. After the venturi I go to 3" through a Borla and out the back. Obviously this is nothing trick, but it really made the car fly. It has lots of down low torque, but allows the motor to pull strong to well over 8,500 rpm with no drop off. I didn't want to re-invent the wheel so like a true racer I just stole what was working somewhere else, LOL.

I plan on finally tuning the car this summer and setting some new HP figures, but I have to tell you that the car is very very strong. It is far stronger now than it was when I pulled an uncorrected 184 RWHP on an untuned Holley setup.

Regards,

Eric

rxtuner79

iTrader: (1)

So it's a 2" exhaust from the header back, collecting at the rear subframe, and then going 3" into a Borla, correct? Is this on stock ports? Do you have any pictures?

People usually say that the best diameter for NA's is 2.25-2.5". Would there be any advantage to opening the piping up a little more? And how loud is that setup (for street and track)?

Sorry for all the questions, but my plans are to get another daily driver so I can have my '89 NA as a dedicated track car. And as far as modifications go I would like to get it as close to race-ready as possible while still driving it daily, so that way when I get another car I can just strip the interior, put in a cage, etc. So I was just wondering about how this exhaust setup would be for the street/autox.

the_duke313

thanks 23racer that helps alot actually. im trying to figure a way to do ITBs on my rx8 and i need an exhaust to supplement it. im also wondering how loud the exhaust setup as my car would mostly be street, and a lil autox

sc0rp7

iTrader: (3)

Want a possible formula for setting up your intake or exhaust length? Try reading this thread... has some good info that should get you close.

https://www.rx7club.com/showthread.p...ghlight=tuning

- Chris

rotarygod

iTrader: (1)

Keep in mind that those formulas are merely ballpark estimates. You'lll do fairly good following them but for that last 10% in gains it takes trial and error and testing. I really need to update some of that info as I wasn't clear in some places and left out some info in others.

sc0rp7

iTrader: (3)

I know im a forum troll, but update that thread whan you can, as well as your custom exhaust sleeve insert thread if you can... I love the reading and information I learned from both threads...

the_duke313

updates???

23Racer

Like I said, sorry for the delay. I don't come back to this forum too much any more as I am spending time with my Speed WC Touring Cougar trying to get it ready for this season. I go from a club racing car with great handling and no torque to a car with poor handling (the world's largest and fastest lawn dart), fwd and tons of torque. Going to try to enter some Speed events later this year.

Anyways, to answer some of the questions. My motor has a Racing Beat Racing exhaust port done by RPM. It is a half BP with Judge Ito Extended primary port and a RB Racing BP secondary. It is running S5 internals and a Tweak It 7.5 lb flywheel setup. I am running a Megasquirt ECU and TII injectors. I am running a full set of Hayabusa ITB's.

Regarding the exhaust, as I only turn the motor to 8500 rpm max I was trying for a lot of velocity so I stayed to the small side. The Aussie guys run 2" primaries into a 3" or a 4" collector and make crazy power all the way to 11,500 rpm. I tried a number of different pipe diameters and this worked the best for my set up. The car has a lot of grunt down low (4500 rpm and up) and pulls hard to 8500 rpm. The whole trick according to some people down under is the collector, it needs to keep the exhaust velocity up for best scavenging without adding back pressure.

Regarding running it on the street, simply no. It is way too loud and coughs out 10 foot flame ***** (which I personally like). By the way, under full throttle the intake noise is actually loader than the exhaust, so you need to consider that.

Eric Nummelin

the_duke313

haha thats awesome. i wouldnt mind some 10 foot flame *****... but im sure cops would

the_duke313

23 racer how is the intake noise on the busa throttles at partial throttle?

23Racer

It depends on the airbox you use, but at partial throttle it is okay, but as soon as you tip into the throttle they start to chuff pretty bad.

Eric

the_duke313

icic i wasnt thinking about using a plenum at first just for simplicity but myabe il hav to use one for noise and maybe easier to tune with MAF

chello

To get your tuned length for your exhaust, a simple and fairly close way is to get a white paint pen and run it along the pipes of your exhaust from the block to the back of the car. Then take the car out for a "spirited" drive and when you get back, have a look underneath and see how mcuh paint/marker burnt off, from where it finished burning, that is your tuned length, exactly half of that is tuned length at a different rev range. Try not put any mufflers or resonaters before that length

rotarygod

iTrader: (1)

^That's the method for determining where to put an H-pipe on a V8 as the paint burn off spot is where the off pulses back up and are the largest restriction. The tuned length of any single exhaust pipe is the total length of it.

chello

Ok, just a backyard way to do it if your too lazy to do the sums :P You put a line on each individual pipe, with a rotary it will be back near the diff, hence why the IPRA boys and alot of rotaries in Australia run their pipes back to the diff before addidn resonators or mufflers

rotarygod

iTrader: (1)

Those are called "long primary" systems. My favorite!