just a quick question for all you subaru masters, just got a toyosport decat up pipe for my 2003 blob and noticed that it has a very large lip at the turbo end, would then be any benefit in porting it and removing that lip?

where it connects to the manifold it 60 mm
where it coneects to turbo with lip 53mm

 

Hi Sam
The way I understood porting to work was that you want the gas to flow uninterupted without any turbulence, so by having a narrower input on the turbo end of the up pipe where it meets the turbo should ensure that happens.
If the gas was flowing the other way it would hit the edges of the smaller diameter pipe and cause turbulence.

That's the way I see it anyway.

 

personally i wouldn't enlarge it any more as the size of the up pipe is to large to start with and will cause lag, going larger will only make it worse.

 

I agree with you when you say you would not enlarge it yourself ,but once done proffesionally, by someone who does not just widen the whole with a dremel,but ports the uppipe for the given turbo(Harvey Smith),then i give you my word the last thing you will feel will be any lag.Since fitting ported headers and uppipe my vf28 spools up not far behind my old td04 ,and better top end grunt.

 

Bigger diameter of Up pipe will kill spool up,don't do this and really rather invest in Harvey Up pipe...


Jura

 

yes but we are not talking about improving the flow of a standard up pipe, but making a over sized upipe even bigger by removing the inner lip, im pretty sure the only way to improve the op's up pipe would be to weld a choke into it.

 

I assume this is a 2 litre car. Performance will be crap with an uppipe of these dimensions. That uppipe would be better suited to a 4 litre equipped with a truck turbo. Big is not always best.
Are your headers 2 bolt or 3 bolt and what is the diameter at the flange where the headers join to the uppipe?

 

yeah its a 2 litre impreza, there the standard headers 2 bolt, i was told removing the cat in the up pipe and fitting a decat up pipe would improve spool up, but im all in your hands please let me know what you think would be the best route for me.

 

I think a 1.75 inch diameter is best for the 2 litre up pipe.

 

so are all the ebay jobies no good?

 

The uppipe that is best for a particular vehicle will vary in design and dimensions.
So we know you need a 2 bolt uppipe. The flange hole centres are probably 100mm.
A 2 bolt tubular GT 1 spec type header exits the collector at 58mm. I do not know what diameter the exit from the collector on a ToyoSport might be but with that information I can match the right uppipe to your application. Getting it right is very important as it has a big effect on torque and spool.

To say that a 1.75" uppipe will be best is a very rash statement.

As many of you will know I do a trick 3 bolt flange uppipe for use with GT2 Spec tubular headers and this has achieved incredible results. I now do a trick uppipe for the 2 bolt GT1 which has a 2 bolt flange with 100mm centres and mates to the 58mm collector. This is now referred to as a trick 2 bolt uppipe but is only worth using if you have a 58 diameter exit from the header collector and 100mm centre flange.
I have six other uppipes, all 2 bolt to accommodate various turbo, header and engine specs and the trick is to match the right uppipe to the right application as this can make a big difference to the crispness, spool and torque available.

Some are total rubbish but there will be some that do a good job but without knowing the diameter of your collector output and actually seeing the uppipe, who knows?
What is for sure is that a 60 x 53 uppipe on your particular car is simply going to slug spool and torque.
harveysmith1@btopenworld.com

 

Basically most are yes. Also only fit genuine gaskets as the cheapie silver gaskets on ebay normally supplied , blow out very soon after fitting. All gaskets and new stud sets etc are available from ICP.

 

So the question is what diameter are your headers at the flange where it connects to your uppipe?
Getting rid of the CAT with the right uppipe will improve spool, torque and crispness/response.

 

All sorted now, got my Harvey up pipe coming tomorrow, so excited
Thanks a million Harvey