exhaust ports

rx jamie · August 22, 2007, 11:35:39 AM

i have a bridge port on my engine. running over 2 bar boost. so i can get the gasses and fuel in pretty fast, id imagine it would be sensible to have my exhaust ports enlarged and remove those sleeves to help get the gasses out faster?
any thoughts ?

G@NDY · August 22, 2007, 11:59:38 AM

2 Bar !!!!!:2eek
There have been some old threads on this matey, either on here or FDUK. I have only known dragon to do this. I think that keeping the sleeves help with heat transfer. Im not 100 % on this, but will try and find these old threads for you.

rx jamie · August 22, 2007, 12:06:29 PM

thankyou very much gandy. i know reworx did it on their fd too. jeff said in a magazine \' it was a labour of love and he would never do it again\' lol

yeah 2.4 bar (35 psi) gt45 im hoping to run on the strip. car will be hopefully don for totb next year fingers crossed (a lot of fingers) its getting there. need to sell my pulsar to finish it

G@NDY · August 22, 2007, 12:12:39 PM

There\'s this one
http://www.mazdarotaryclub.com/forums/showthread.php?t=22662&highlight=remove+exhaust+port
and
http://www.mazdarotaryclub.com/forums/showthread.php?t=36543&highlight=exhaust+sleeves

hope that helps. Sounds like quite a project, i look forward to seeing it at some shows in the future.

rx jamie · August 22, 2007, 04:58:02 PM

thanks gandy thats very helpful and just what i need :cheers

rx jamie · August 30, 2007, 06:18:20 PM

does anyone know where i can get exhaust port templates from,that can be used on a bridge ported motor ? ive been on pineapple racing and sites from all over america, new zealand and oz. all i can find are street port exhaust templates.

stuart wizy · August 30, 2007, 06:37:32 PM

you can remove the sleeves and go as big as you feel is safe leaving enough meat in so you dont break through into water jacket, i used some odd leg calipers on mine so i didnt break through, i think the wall thickness top and bottom where about 4mm thick on mine when I finished them so basicly I went as big as possible up and down but didnt make the port any wider, I just scribed a line up and down each side of the widest part of the std port with some blue painted on and took it out to the line and then kept checking the wall thickness up and down.
I think there are around 45mm in height when they was finished measuring from inside the housing.
I used a big porting tool and a power file to get it flat.

kev-yorks · August 30, 2007, 06:41:09 PM

Leave the sleeves in place and port them as they conduct the heat away from the housings and into the exhaust. No problem if its just a drag monster but on a street car you could see elevated engine temps.
Kevin

stuart wizy · August 30, 2007, 06:53:51 PM

I have yet to build and run my motor but mines running full bridge with the intermediate bridges almost as big as the end plate bridges with massive inlet ports with a matched inlet manifold,
unchartered teritory so how it performs I don know but hopefully it will perform well and it will rev high safely I hope.

rx jamie · August 30, 2007, 07:12:06 PM

let me know how it goes. will have to put mine back a few weeks or so now as ive blown the big ends on my pulsar, sticking it to a 911 turbo on friday :Grrr

did you get your rotors balanced then? i was reading on another thread ?
what other work have you done/ considered

stuart wizy · August 30, 2007, 07:59:31 PM

to be honest its just dragin on and on, I do a bit then loose interest then do a bit more and so on.
ive milled rotor tip grooves out to 3mm, cncd sides of rotors to lighten them like racing beat do, ive cncd the bridge ports then finished them by hand, ive machined the inlets on all plates loads bigger with a flange plate machined out to match the inlet shapes exactly, ive made the plenum and shaped 4 50mm runners to be welded onto this inlet flange so the air volume from plenum all the way into bridges will be much bigger than any side port motor that I know of anywhere, everybody seems to use cosmo runners or a pp motor.
I havent balanced my full assembly yet but do have a good idea how to do it now!!
I really want to use a 2 piece e shaft with centre bearing but they arnt cheap, then I could rev it really high without any flex on that e shaft to make the power band much longer with the full bridge and big laggy turbo.
Ive got access to horizontal and vertical boring machines so the machining on the middle plate wouldnt cost me nowt which helps.
It takes time especially when your trying to run bussines
keep me informed on your project mate:yes

antnicuk · August 30, 2007, 09:49:53 PM

Quote from: rx jamiei have a bridge port on my engine. running over 2 bar boost. so i can get the gasses and fuel in pretty fast, id imagine it would be sensible to have my exhaust ports enlarged and remove those sleeves to help get the gasses out faster?
any thoughts ?

well it wont be long before it needs a rebuild so you can do it then :rollin

if its a drag car then try it, if you intend to run it at full boost for any length if time, keep em and port em. I have heard they also help with noise reduction. I made mine much bigger by removing them, heating them and stretching them where they shrink in the housing, then put them back and port the housing to match.

I assume from reading your posts you havent actually run this engine yet?, you may want to start it at a little less than 2 bar unless your on the strip or you will have more than a bottom end to rebuild. Remember when an RX7 pops it often damages the turbo at the same time.

You will also need some serious transmition mods to take the power.

FLAT4MATT · August 30, 2007, 11:58:52 PM

Not an expert but surely if you wanted to go bigger than the inserts why not get some new bigger sleeves made to fit your enlarged ports? If you get it all machined and pressed in then could that be an option?

Carl · August 31, 2007, 12:22:09 AM

What you can do is a sort of compromise by just using the outer ring part and eliminatiing the rest.
When you have taken off the inner part then turn the inner part of the remaining ring until you have around 2 or 3 mm of the outer part of the ring left,this then still helps to take some heat away from the engine to the exhaust manifold.
Once you have done this bit then you can open up the port inside the rotor housing to around double of it\'s original size by going down for about 3-5 mm and up 10-15mm.This gives alot of overlap,but on a drag engine it does not matter as at revs it will work really well.

Regards
Carl

rx jamie · August 31, 2007, 05:41:27 PM

yes i will do stuart, and likewise. im in a similar boat myself. i have a young family and i find i often i have a surge of enthusiasm for a few month, then it wains as the guilt of spending endless nights in the garage catches up with me lol.
im not taking my project to those lengths although i really wish i could. ive been researching and buying for two years now on and off !

it may be more cost effective for me to let the engine blow and rebuild it. especially with the cheap price of turbos and engine parts these days.
i would be happy if my engine lasted 50 miles once complete. i am absolutely expecting my engine to blow up lol , and i do not expect to drive my car on the road. its purely a weekend interest.

thanks for input
i will have a look at that tonight carl.