hmmmmmmmm
https://www.rx7club.com/attachment.p...hmentid=116083
https://www.rx7club.com/attachment.p...hmentid=116082

 

nice job , arent those really big ?

 

I thought the stock exhaust port was massive to begin with.

And, well, whats the effect of porting it even bigger anyway?

 

Yeah, that looks about right.

 

Thats hungrier than a fat chic @ KFC.

Those ports are identical to what I did on my last engine.

 

whats the effect of radical exhaust porting on a rotary?

 

Bevel the closing edge!

Yup.

 

thats ******* huge
they are like as big as u can go

 

Did you pretty much take the sleeves out and go even more?

 

glad to see the postive responses

 

holy **** ...

man, what the hell did you do to get that? i was just porting my exhausts tonight and wondering if mine were too big, but ... WOW!

2 questions:

1. what do you use to cut your exhaust?

2. how would i get the sleeve out, like yours?

 

Very flat torque band around peak that stretches for over 1500rpm when running a street port, all others have a peaky narrow range in comparison

 

I dont know what gains I willget from this size

 

Those are humongous. I hope there's not a dramatic power loss due to the port opening so early.

Bevel the closing edge.

B

 

Rice Racing - could ya run that by me again, I dont quite understand what you mean.

Do you mean it makes the torque peak larger so you have a bigger powerband to work with?

Also, does it effect low end or midrange at all?

 

You loose a fair bit of low end power, mid range power to 5k is only slightly lower from 5.5k to 7k it makes almost flat torque on a street port has a nice flat peak to it, it makes the power more linear in this range (steadily going up) then it falls away (depending on size of turbo charger and exhaust). Ideal set up is to run this on a large frame GT Turbine housing at minimum GT42 1.15 or a twin turbo set up with 2.5" ID headers... When I didi it I ran with 2" ID headers and a small T04 1.32 housing (small runners) and I did not get the high rpm gains because of restrictive turbo.

My new engine combo has exactly the same porting, its as large as you can fit wihout the seals droping out or water leaking into the chamber, basicaly.... but this time running a more matched turbo and header combination to make full use of it.

 

Ah, so the same as porting anywhere else but without the drastic low-end drop.

BTW, why do you lose low end from porting out the EXHAUST anyway. Is it because of the earlier opening and not giving the expanding charge time to push the rotor all the way through the cycle as it would if it were unported?

I'm still a bit of a newbie and tryign to figure all this out :P

 

did you use a Dremel? if so, what kind of bits did you use and from where?

how do i go about removing the port sleeve?

 

Removing and swapping exhaust port sleeves

 

what do you guys mean bevel the edges?? can you show pics

 

He didn't do the porting, just for clarification here, so I don't think he has any idea about beveling the closing edge or why it's important. Nor would he probably be able to tell you much about removing the sleeves...

Sir Rupert Hobo bought the housings from SilverRotary, and he bought them from Rupert.

You know it's kinda lame to make a post about "your" exhaust ports acting as if you did the work when you really didn't.

And FYI, in stock form the closing edge of the exhaust port as a 2mm bevel for support as the apex seal travels over it, better transition. Once you port the exhaust these is taken away and must be added back.

https://www.rx7club.com/showthread.p...3&page=1&pp=15
https://www.rx7club.com/showthread.php?t=431210

 

to put it simply: on a rotary when you port either exhuast or intake ports you will shift your powerband more to the right. which means you will have a peaky power band at around 6-8k. and the bigger you port the higer your revs are going to be because once you get to bridge-porting all your power will be at 7k or higher. and thats for street use. not to mention where the power goes when you "MONSTER PORT" or Peripheral Port. if i were you since you already have a massive exhaust go with a race port on the intake or "D-bridge" it with high compression rotors. or use 9:1 rotors with a T04S turbo. that should give you some good driveable power.

 

Ito gave a great run down on that subject....

http://www.nopistons.com/forums/inde...howtopic=31895

James

 

cpt: And if I were to street port it, compared to stock, where would my powerband be?

 

They key tuning idea behind exhaust porting is overlap. The farther up you go, you give the engine more port overlap (where the intake and exhaust ports are open at the same time) so that the sweeping out of the exhaust gasses will draw in more air on the intake charge. These modifications can really only be utilized at high engine speeds when the rotor is moving fast enough and the manifold pressure is high enough to keep from pumping that fresh air back into the manifold. This is why ported engines make more power at the top end (much like aftermarket high duration cams in a piston engine) and also why they pull less vacuum.