View Full Version : breathing mods

Iain Atkins
6th June 2001, 09:40

This is my first post on the 22b bbs http://bbs.22b.com/ubb/biggrin.gif ( i am registered on scoobynet but have realised that the real enthusiasts (sp?) are on 22b http://bbs.22b.com/ubb/wink.gif

I have a uk my97 with magnex centre and rear and ITG panel filter and i want to try and speed up the spool up of the turbo but due to getting my first house things are a bit tight.

I was told to get an induction kit (pipercross vortech) and dump to atmosphere DV (Bailey), will this help me or will it just attract the wrong attention.



Danny Fisher
6th June 2001, 10:56
Iain, yep a induction kit will help some what. The vent to atmos. D/V will make the car run rich, thus you will need a deep pocket for the petrol bills.

If you want the turbo to spool up faster try a downpipe. This is commonly known as the best way for a turbo to spool up. Removes the cat, aids breathing.

Dan - UK MY97 owner of sorts!

6th June 2001, 10:56
Have you removed the resonator yet? This greatly improves throttle response and benefits spool time too.


Iain Atkins
6th June 2001, 13:33
Thanks for the replies


I have tried the resonator trick and in the end i cut the bottom part off (box baffle part) and resealed up the pipework with fibreglass, drilled a drainage hole and put it all back on. The reason i did this was because of all the leaves etc that were ending up in the airbox, so i though that by removing the baffle part and keeping the pipe diameter more uniform, it would help airflow - it did work and looks standard when viwed from under the bonnet, but i suppose like anything, i have now got used to it and want more.


I'm probably going to order an induction kit next week so that i can try it out. The induction roar isn't too loud on the Scooby is it?

I am only going to change the DV if it is going to be of benefit, if all i get are higher fuel bills and boyracer like 'woosh' that i might not bother.

You say you have a UK97 of sorts, whats that all about then, bit special is it?

Thanks for your help so far


Adam M
7th June 2001, 12:55
Fitting any after market dump valve is not going to be a benefit on teh scoob, unless yours is leaking or you want to change the noise.
The downpipe will make a huge difference, as will adding the furthert sections to your exhaust.

induction noise will increase but it is nice. I would go for K and N for value, and consistent reliability. When changing such things, dont forget about the filtration characteristics, which is why it is on the car.

Danny's is a bit special for reasons relating to air and water http://bbs.22b.com/ubb/wink.gif. It is certainly bloody fast. http://bbs.22b.com/ubb/smile.gif http://bbs.22b.com/ubb/biggrin.gif http://bbs.22b.com/ubb/smile.gif

11th June 2001, 14:33

most of what needs to be said has, errr, already been said http://bbs.22b.com/ubb/smile.gif

To improve spool up, you need to reduce exhaust back pressure or increase manifold exhaust gas speed. Of the two, the former is easier to achieve, so look at the exhaust system and identify the restrictions and remove them. In general the biggest restriction is the cat in the downpipe, that's why replacing the downpipe has the single most noticeable effect on spool up... get rid of any centre cat or resonator.

Increasing exhaust manifold gas speed is a bit at odds with high power, as it almost certainly requires either higher temperature or a smaller diameter pipe. Higher temps will limit the safe operating area (before you melt the turbo) and smaller diameter will seriously limit flow at the top end... not good.

Dump valves are a bit of a myth. No dump valve will improve performance over and above that achieveable without a dump valve (unless the turbo is so large that the shock load on the system would be great enough to burst pipes / blow intercooler cores on lift off). What it will do is save the turbo from shock loading as you lift off. Different valves require different amounts of manifold vacuum before they open; in general the more they require the less boost lost during a gear change. Unless your DV is leaking under high boost, any replacement is likely to make very little difference; it will NOT affect turbo spool up or boost threshold (unless it is leaking so badly as to bleed significant amount of air when it should be shut, read: unless it is broken). It may make a slight difference in gear changes, which is a different issue entirely.

Induction kits will not affect spool up. There, I said it http://bbs.22b.com/ubb/wink.gif What they may do is to improve power due to lower insertion loss; that is to say the create less partial vacuum at the the turbo impeller than the stock item. Any reduction in partial vacuum at the turbo inlet is a VERY good thing. This allows the turbo to operate at a reduced pressure ratio, which is almost invariably a higher efficiency point on the compressor map. In short, it reduces outlet temperature, hence increasing charge density and thereby allows more charge per cylinder and thus also more power. But it won't materially affect spool up, however it may sound like it does, due to the added induction whistle.

Hope this helps,


11th June 2001, 15:43
Pat - I think you should write a book, good stuff! http://bbs.22b.com/ubb/smile.gif