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S13 Race developements
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366 Posts
yes. sounds good, with very strong back fires. but i guess not your not too intersted in sound, how does it go, have you road tested it yet?
so its just the back box changed. correct?
 

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Themis
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1,791 Posts
Discussion Starter #102
Haven't done anything yet. Thinking of doing the single tip back box, which would basically be a free flow single pipe back box connecting with the 2,5' exhaust piping after the downpipe. The tip would have to be over 100mm me thinks in order to have the right proportion with the bumper void. It will be an interchangeable part used only for rally mode. The length of the part would be exactly the same as a stock back box. I will disassemble the exhaust clamp and remove the JCW stage1 to fit the new one before every event.
It will be loud for sure but not as silly loud as the side exhaust I was initially thinking.
If you watch the videos I posted with the exhaust view and listen carefully you will hear that the exhaust is full...It has that characteristic hissing which is heard when the whole volume of the pipe is covered and gases have altered their velocity to a point and they are struggling to exit the pipe. So I thought removing the Y joint prior back box and using a larger diameter pipe back box will run more efficiently than the JCW stage1 I already have. The shortest way is the straight, right?
I would like to know what you all think. Does anyone have a better idea?
Of course once I decide which way to go I will road test with all info posted here.
I want your opinion on this, so keep the ideas coming...
 

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S13 Race developements
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366 Posts
i wouldnt know the technicalities of how the gas work at different stages of the exhaust, when you take into account of exhaust gases going through the down pipe, then resonantor and finally the back box.
simple logic suggest a straight pipe with no restrictions should work best. this is not the case. as im sure you need certain pressure in the system. a straight pipe may even hinder power.
like i said, im no expert on exhausts, so someone with ACTUAL knowledge would be better suited to comment on this.

what thing i can say for certain, a catles downpipe adds power in the mid to high rev range. and be decrease slightly in the lower range.
 

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Themis
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1,791 Posts
Discussion Starter #104
Thanks mate for your reply.

As usual, I like to base my conclusions to my own empirical data acquired. So I might have to do some further testing before I decide what will be the best solution. Dyno and road testing with and without back box, with a straight pipe or without and will see.

As far as the downpipe is concerned I agree with you, I just don't want to swap my Akrapovic (100cpi) for a decat. I am sure there is a very small gain from that, considering that the Akrapovic is already free flowing. Not to mention it passes all the smog tests and MOT with no problems.

There is also another thought that crossed my mind with the back box. Keep the twin tip design with the engraved JCW stage 1 tips modified and a new back box with internally bigger diameter pipes (something like the challenge box)
I'll put some photos of the tips to explain further what I mean...tbc
 

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Themis
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1,791 Posts
Discussion Starter #105
This photo is not mine, stole it from another thread but here you can see te design of the JCW stage1 tips (45mm internally) ImageUploadedByTapatalk1341772604.686301.jpg
They are just slot into position and tightening the bolt underneath will hold them on the actual pipes exiting the back box.
Now, if I loose the internal part as seen in the picture, that will give me two pipes 85mm in diameter (I think pretty much the same as the challenge tips?) and then have them welded onto another box with the appropriate dimension.
What do you all think?
 

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Registered
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3,198 Posts
Changing exhaust and downpipes can produce more power ,and better spooling of the turbo - the target is the minimum possible backpressure , so wider pipes , hotter pipes , and minimum restriction ,minimum length - However like everything mechanical there is a price to pay ;
the Turbo has its limits , reducing backpressure increases the speed it spins at - usually beyond its design limits - always this reduces the life of the turbo , maufacturers spend loads finding limits , the shaft of the turbo has harmonics and accurate dynamic balance,under load the bearings must hold things aligned - spin the turbo faster ,all bets are off ...
Often oil seals leak and oil mist gets into intake or of out the exhaust , or bearings fail -the point this happens is unknown but I guess its not much beyond stock power -for any length of time
Answer ; get a better turbo ,hybrid or better yet a bespoke turbo for your needs
Turbos are like golf balls -one is never enough ......
 

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Themis
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1,791 Posts
Discussion Starter #108
Thanks Adam...all your info sounds familiar to me...
So while I am having fun with the JCW turbo I will fit a less restrictive back box and give it a go...

Golf balls eh? I am already using my third turbo, so maybe one more won't harm me eh? It's all part of the game...
I'll wait till this one farts and then go for a better bespoke one...thanks for the advice though.
 

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Registered
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3,198 Posts
Im sure its not news to you but ... you are dealing with an old design turbo , no ball bearings , so more oil flow needed for journal bearings and extra chance of seal failures , no ceramic bearings ,no billet constructed wheels,no ceramic blades , no bleed recirc air to compressor , no efficient design comp wheel ...etc
you have biltong and want steak... :lol:
couple this with a manifold made for low grunt and response not high boost and flow and a DI restricted rpm engine - not the stuff of dreams without much £££ spending
All this is unlikely to stop MTers - so go buy a better golf ball :lol:

Your folly is to everyone elses benefit
 

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Bugger
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25,329 Posts
Thanks mate. The videos don't do justice. In reality it sounds horrifying...

Very sunny, no rain in a month and 35-40oC...

Clear sky is one thing...40oC is another! Got to watch my IATs, if you know what i mean...
Try scotland i dont remember what blue sky looks like anymore.
 

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Themis
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1,791 Posts
Discussion Starter #119 (Edited)
Took some pictures of the caliper's spacers the other day and thought to post them, might be handy...

ImageUploadedByTapatalk1342534259.230663.jpg ImageUploadedByTapatalk1342534333.775113.jpg

As seen on the pics upper and lower spacers are the same with 4mm thickness each.

Another issue which should be addressed when splitting the calipers and using the spacers is the spring that holds the pads...
ImageUploadedByTapatalk1342534527.127385.jpg ImageUploadedByTapatalk1342534552.163975.jpg
As the photos show there is an extra 2mm clearance from each side of the caliper. Well there shouldn't be...cause the spring might move from one side to the other, when hitting a pothole for instance. Thus it won't be centered where it should be and would scrap on the perimeter of the disk giving you a continuous squeak. I did this as a remedy...
ImageUploadedByTapatalk1342534982.266188.jpg
 
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