View Full Version : Downpipe, does it need lagging?

Chris. Lax
2nd April 2000, 21:57
I fitted a S/S donwpipe and magnex mid.section just over a week ago and was wondering whether these needed to be lagged. Any comments would be welcomed.


P.S. What a difference these two additions have made to the car, amazing!
Unfortunately with the extra urgency the car now has in second and third gears, the front end is noticeably lifting, is it now time for an anti lift kit, any advice would be appreciated.

2nd April 2000, 22:23
Have you retained the heat shield ?

I too am going to be SS downpipe-ing it soon, have some exhaust wrap in the shed so would be interested to hear from an exhaust guru.

chris did you fit it yourself ? if so, how much of a job is it ?

Chris. Lax
2nd April 2000, 23:26
Yes I fitted it myself (5 hours of fun), the only part of the heatshield that was retained is the alloy part around the turbo (with the hand sign on), this had to be trimmed due to S/S downpipe being wider than standard.
The job would only take 2-3hrs once you know which bits come off in what order. Unfortunately one of the bolts attaching the downpipe to the turbo was seized which delayed matters for quite a while.
I also had to replace the bolt at the support bracket underneath the car, as the alignment of the pipe and the bracket were not quite right, a smaller bolt fitted nicely.
Hope this helps,

3rd April 2000, 00:10
If you guys would like to know the benefits/drawbacks of wrapping compared to HPC coating , drop us a line.

The fact of the matter is wrapping does cause premature wear although there are some benefits...

Greg Nikolettos www.bpmsports.com (http://www.bpmsports.com)

3rd April 2000, 00:39
I had the pleasure of being the first Impreza that Pete Croney fitted with his version of the Down-pipe.

I was used to "exagerated claims" regarding cars in general, but Pete just let the product "do the talking"! http://bbs.22b.com/ubb/biggrin.gif

It turns a 22B as standard into a rocket ship http://bbs.22b.com/ubb/biggrin.gif Pete Croney wrapped my down pipe, ceramic coating is an expensive option that I have sought as well.

Consensus is "wrap up well"! http://bbs.22b.com/ubb/biggrin.gif

3rd April 2000, 12:18
Ok guys, humour me. I have the SS downpipe and Magnex centre section. Whats the reason behind lagging them?

3rd April 2000, 13:24
Keeps the hot gases hot inside the pipe and stops the engine bay melting! http://bbs.22b.com/ubb/eek.gif

Something to do with efficient exhaust scavenging I believe.

3rd April 2000, 16:07

Does the BPM exhaust that Mike has on his car have this HPC coating?
If so, why is it so rusty?
If not, why is it so rusty?


3rd April 2000, 17:34

I think some of the pipe is mild steel...not Stainless

but what do I know.


Andy Tang
3rd April 2000, 20:18
My downpipe was fitted by Pete about a year ago now, but it wasn't lagged. should I look at getting it done, or is not really worth the bother now?


4th April 2000, 01:49

Due to your [UK] "salty" conditions we have gone to mild steel with HPC[ceramic] coating for the entire exhaust. Alternatevely stainless for the full system is an option , although you get far better bends and longevity with mild steel and HPC [Ceramic] coat.

Mike's mid and back section is in mild steel. If you see his downpipe you will see it looks like the day it was made.

Greg www.bpmsports.com (http://www.bpmsports.com)

4th April 2000, 16:33
Still looks pants though! http://bbs.22b.com/ubb/wink.gif


4th April 2000, 18:35
Hi guys..

I strongly suggest some form of heat insultation on the down pipe.

Either HPC or Lagged.

I have had lagging on my D/P for quite a while and suggest it. For exhaust gas temps.. and to minimise the heat in the engine bay.. it is very close to the brakes and power steering.

I also have HPC on my equal length headers.

Both are similar price (for the same job)

The results are similar with HPC slighty winning. The reason I havent HPC'ed my D/P is becuase I might be changing it.... and I already paided for the lagging.

Dont bother lagging equal length headers... due to the complexity of shape the lagging will eventually come loose.

I'm not advertising here.. but if anyone is interested in HPC, let me know.. I have a company I know use.


ps - If the bolts come lose off the turbo its quite a quick job... if not... cry... lol
pss - Remember to moisten/wet the lagging first

4th April 2000, 18:54
WRC engine showing lagging of manifold and DP I think........




[This message has been edited by frisby (edited 04 April 2000).]

4th April 2000, 23:03
I expect that Greg of BPM is happy to receive feedback about his products!

In a way it is a shame that there is not more competition in the UK market over Scooby stuff.

Once people start evaluating alternative products this is the forum to give open feedback!

5th April 2000, 04:31
We [BPM} are quite happy to accept whatever advise the UK has to pass on. We will endeavor to tailor solutions to suit your market.

Whether that be on product already in production or items on a wish list.

Just like Anders pointed out we have something to offer that is a bit different to a backbox solution etc.
Not to say we do not offer them but I think offering high performance mufflers, FMIC, Chargecoolers, carbon Fibre Airboxes , large inlet pipes etc , will allow the Impreza owner to evolve as their needs change.

In a nutshell we will try to fill what we consider large gaps in the UK performance sector.

Greg www.bpmsports.com (http://www.bpmsports.com)

[This message has been edited by BPM (edited 05 April 2000).]

[This message has been edited by BPM (edited 05 April 2000).]

Andy Tang
5th April 2000, 14:12
Can I lag a downpipe without taking it off the car?? Or will I have to pay lots of cash for someone to take it off, lag it and put it back on???

Andy http://bbs.22b.com/ubb/frown.gif

5th April 2000, 23:38

You have to take it off. The difference between wrap and our coat has to be explained.

This is a email that was on the WRX tech list that we repsonded to.

> Dave,
> >1. It says that it reduces underbonnet temps. Does this mean that it
> >retains the heat, like what we're trying to do with heatwrap?

If you can retain heat i.e. improve heat retaining properties within the
exhaust you will increase gas velocity within the piping.
So the better the heat retainment, the better the scavenging.... The
Extreme coat provides more HP than HPC is because it is better at
heat within the exhaust.

>2. It says that it has Rapid cool-down, is that defeating the purpose of
> >what we're trying to achieve e.g. retaining heat?

Rapid cool down is termed at the fact that the dispersion of heat is not
as evident since it remains WITHIN the exhaust piping. The cool down is a
result of the low running temperatures OUTSIDE the exhaust piping. The
exhaust coated allows the exhaust gas to remain extremely hot rather than
keeping the piping hot via wrap. The difference between HPC and wrap is
the fact HPC coat allows the exhaust gases to remain hot whilst the wrap tries
to keep the exhaust piping hot.
Add to the fact HPC will last about 10 times longer than what wrap does it
makes for a more sensible purchasing decision...

3.> >Is there any merit to heatwrap an HPC coated system?

Do not do it will void all warranty with HPC , it does not allow the
to do the work. If you want a coat that will handle in excess of 1300F go
Extreme coat....
The wrap would suffocate the coating not allowing the transfer of heat
that is necessary to take place....
> If you have any further queries about our products , please do not
> to email me or we can chat online with
> ICQ (45940764)
> Greg Nikolettos
> BPM Marketing Division
> Phone: (617) 3272 8885
> Fax: (617) 3218 8880
> bpm@bpmsports.com
> http://www.bpmsports.com

Hope that clears some of the questions that come up. As you can see we have a bit of a fetish with the HPC.

Greg Nikolettos www.bpmsports.com (http://www.bpmsports.com)

Warren Heath
15th April 2000, 20:18
Hey frisbee, I built that one!
Anyway, Just look at the standard exhaust manifold on all standard Subaru models. The amount of heat shielding is incredible. In these days of optimising costs in production and manufacture, it shows they regard this as an important issue. The more lagging/heat shielding the better. Under bonnet temps are sky high in these things anyway. Once the exhaust is in the airstream underneath it can cool, but I would always lag at least 9" under the turbo, especially if running modified components..

15th April 2000, 20:21
Warren is not bull sh1tting either! http://bbs.22b.com/ubb/biggrin.gif
I thought the picture looked familiar!
My equal length headers looked like that, shame they were not quite perfect.......perfectionists! http://bbs.22b.com/ubb/cool.gif

Between Firefox and Warren they decided the headers needed further work http://bbs.22b.com/ubb/rolleyes.gif

[This message has been edited by Anders (edited 15 April 2000).]

Chris. Lax
16th April 2000, 16:34
Were do I get lagging suitable for the job and what cost should I expect?

16th April 2000, 20:26
As far as I understand it heatshielding or lagging is used:
1) to keep heat in
2) to prevent heat from affecting other components

Standard cars with under-floor catalysts may require heatshielding to ensure fast light-off for the 'cat' for emissions regulations or for 'grass-shield' purposes. Particularly with 4WD vehicles that may be more like to take an off highway excursion.
I cannot see that hot gas increases scavenging - maybe someone can explain that to me. - tuning manifolds is a pretty complex process and as far as I know high temp gas is not a particular requirement.
If the pipe is bigger than the previous (unlagged?)pipe fitted you will be decreasing the clearance to other systems in the vicinity of the pipe which maybe would influence the requirement to lag or not.


Ian Sutton
21st April 2000, 20:27
Im totally confused,I had a Scooby Sport down pipe fitted two days ago and Pete didn't ask whether i wanted it lagged (at extra cost obviously).Surely if this was so important it would be recommended???

Got me worried now!


24th April 2000, 18:17

Don't worry too much about the lagging on the downpipe... you may find slightly higher under-bonnet temp without it, but this shouldn't really cause a problem. I was running for about 6 months without it and didn't have any problems.

I have recently re-ground the exhaust headers and in the process ditched the heat-shields, replacing them with exhaust wrap. The difference is quite incredible... the car just does not seem to run out of puff no matter how hard it has been driven. Coming to a standstill after an "enthusiastic" drive, the engine bay could only be described as "warm"; certainly I can lean on my intake manifold without feeling the need to remove my hand for fear of burning.... something that is not true of Anders' car [yet... I guess when that new manifold goes in, it will get lagged :)]

This difference was observed BEFORE the downpipe was lagged. I ran out of time on the day I did the headers and had to return later. The effect of lagging the downpipe wasn't really noticeable, certainly in comparison to the headers. Don't forget that you'll lose about 120-150 degrees in the turbo! I have thought of lagging the turbo, but I'm a bit worried about it getting too hot [more oil / water needed methinks!]. There's one piece of pipe left with no lagging, from the headers up to the turbo. I intend to wrap that up to see what difference that makes..... I suspect the answer will be "not a great deal".... the turbo still gives off a lot of heat!

Moral of the story.... lagging the downpipe alone probably won't do a huge amount [it WILL help, but how much?]. Lagging the whole lot will most definitely reduce under bonnet temp... a lot. But this ain't a cheap excercise. Thus far I have spent over UKP 100 on wrap, and it's not finished yet [I was pretty liberal with the application, admittedly!]



24th April 2000, 23:06
When my turbo was replaced at Scooby Sport Pete Croney took off my down pipe lagging as he now says it doesn't need it.